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  • 2701. Yang, G.
    et al.
    Nilsson, Fritjof
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Schubert, D. W.
    Universal and anisotropic simulation platform for the study of electrical properties of conductive polymer composites2019Ingår i: AIP Conference Proceedings, American Institute of Physics (AIP), 2019, Vol. 2055, artikel-id 050012Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to carry out a study on the synergistic relationship of variables which could affect the electrical properties of CPC, a universal and anisotropic platform of simulation, containing three simulation modules are explored. The simulation modules are: finite element modelling (FEM), percolation threshold modeling (PTM) and electrical networks modelling (ENM).

  • 2702.
    Yang, Kunlong
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Flexible Electrical and Photoelectrical Artificial Synapses for Neuromorphic Systems2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Over the past decade, the field of personal electronic systems has trended toward mobile and wearable devices. However, the capabilities of existing electronic systems are overwhelmed by the computing demands at the wearable sensing stage. Two main bottlenecks are encountered. The first bottleneck is located within the computing module, between the processing units and the memory, and is known as the von-Neumann bottleneck. The second bottleneck is located between the sensing module and the computing module of the system.

    Inspired by neuromorphic computing, an architecture of the sensitive neuromorphic network (SNN) is developed as a candidate for overcoming both bottlenecks. Suitable building blocks, especially in flexible form, must be developed. In this work, starting from the demand analysis and followed by prototype development, performance optimization, and feasibility testing, two kinds of critical devices were developed for fabricating a photosensitive neuromorphic network (PSNN).

    A high-performance flexible electrical artificial synapse that is based on the electron-trapping mechanism was developed. In addition to the basic memristive features, multiple kinds of synaptic plasticity were also demonstrated, which enriched the collection of possible applications. Furthermore, optimization on multiple performance metrics was easily performed using the intrinsic features and structure of the device.

    A new photoelectrical artificial synapse was also realized by successfully combining light signal sensing and processing in a single synapse. A flexible dual-mode photoelectrical synapse, which fulfilled the requirements of the designed PSNN working protocol, was demonstrated. The device showed gate-tunable photomemristive features, thereby enabling its application as a photoelectrical artificial synapse.

    Using the newly developed devices and the proposed network architecture, this work successfully initiated a new area of research, namely, the sensitive neuromorphic network, and provided a valid solution that addresses the current limitations of existing wearable electronic systems.

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  • 2703.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Huan, Yuxiang
    tate Key Laboratory of ASIC and System, SIST, Fudan University, Shanghai, 200433, China.
    Xu, Jiawei
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zou, Zhuo
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Li-rong
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    Universal and Convenient Optimization Strategies for Three-Terminal Memristors2018Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 6, s. 48815-48826, artikel-id 8454450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Neuromorphic computing, i.e., brainlike computing, has attracted a great deal of attention because of its exceptional performance. For the hardware implementation of neuromorphic systems, the desired key building blocks, artificial synapses, have been intensively investigated recently. However, many issues, such as the small state number, low reliability, and high energy consumption, have complicated the path to real applications. Therefore, methods that can improve the performance of the artificial synapses are highly desired. Although different artificial synapses have diverse working mechanisms, universal opti- mization strategies that can be applied to most three-terminal field-effect-transistor-type artificial synapses are proposed in this paper. Instead ofwasting the third terminal in the device structure, the working condition can be effectively tuned by this third terminal. The key parameters, such as the gate electric field intensity and distribution, can be adjusted, and the performance is thereby tuned. In this manner, multiple performance metrics are optimized, such as the current change per pulse (ΔI), the linearity, the uniformity, and the power consumption. The mechanisms behind these strategies are also investigated to strengthen the effectiveness. This paper will push the performance of the current artificial synapses to a new level.

  • 2704.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik. State Key Laboratory of ASIC and System, Center of Micro-Nano System, School of Information Science and Technology, Fudan University, Shanghai, China.
    Yuan, S.
    Qiu, Z.
    Zhan, Y.
    Umar, A. A.
    Zheng, L.
    Seoane, F.
    Humidity effect on photoelectrical properties of photosensitive field effect transistors2019Ingår i: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 69, s. 42-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Environmental influences are critical for the reliability of photoelectric devices, especially those using organic semiconductors. Among all the influence factors, the effect of relative humidity on the material's photoelectrical properties receives less attentions. To date, reported humidity effects are mostly related to the electrical properties. Their impact to the photoelectrical characteristics has rarely been investigated. In this work, we firstly report a detailed study on the dependency of material's photoelectrical properties on the relative humidity in photosensitive field effect transistors. It was found that both the amplitude and the decay time of the photocurrent indicated a profound dependency on the humidity. To further clarify the mechanism, experiments were carefully designed along with a simulation to recognize and to provide a detailed understanding on any possible influence factors in these processes. The results indicate a prominent co-existence of carrier-trapping and dielectric-polarization phenomena in the photoelectric device under the influences of humidity. Since the water molecules in the atmosphere are predominant, the observed variation in the photoelectrical properties can be explained.

  • 2705.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Huan, Yuxiang
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Tu, Li
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Xu, Jiawei
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zou, Zhuo
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Wang, Jiao
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Lirong
    KTH, Skolan för elektroteknik och datavetenskap (EECS). Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    Merged acquisition-processing system based on a photoelectrical neural networkManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In brain-inspired computing, one of the most attractive fields of study currently, new issues are emerging despite its booming development. From the systems perspective, the performances of the existing systems are hindered by inadequate hardware support, particularly the unavoidable data acquisition and transmission between the sensor module and the data processing module. In this work, we break this bottleneck by proposing a photoelectrical neural network (PNN) that merges the new sensing function into the processing network. Benefitting from its high-parallel structure and minimized hardware consumption, a novel merged acquisition-processing (MAP) system with very high efficiency and very low cost has been developed. As the key component of the MAP system, a dual-mode photoelectrical synapse (DMPS) is carefully designed and developed. It has advantages in terms of both function and performance as compared to the existing artificial synapses, which make it the best candidate for the proposed system. This work will initiate an entirely new field of unconventional neuromorphic systems.

  • 2706.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Huan, Yuxiang
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Wang, Jiao
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Tu, Li
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Xu, Jiawei
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zou, Zhuo
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Li-rong
    KTH, Skolan för elektroteknik och datavetenskap (EECS). Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    Tunable flexible artificial synapses: a new path toward a wearable electronic system2018Ingår i: npj Flexible Electronics, ISSN 2397-4621, Vol. 2, nr 20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flexible electronics has been deemed to be a promising approach to the wearable electronic systems. However, the mismatching between the existing flexible devices and the conventional computing paradigm results an impasse in this field. In this work, a new way to access to this goal is proposed by combining flexible devices and the neuromorphic architecture together. To achieve that, a high-performance flexible artificial synapse is created based on a carefully designed and optimized memristive transistor. The device exhibits high-performance which has near-linear non-volatile resistance change under 10,000 identical pulse signals within the 515% dynamic range, and has the energy consumption as low as 45 fJ per pulse. It also displays multiple synaptic plasticity features, which demonstrates its potential for real-time online learning. Besides, the adaptability by virtue of its three-terminal structure specifically contributes its improved uniformity, repeatability, and reduced power consumption. This work offers a very viable solution for the future wearable computing.

  • 2707.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Humidity effect on photoelectrical response in photosensitive field effect transistorsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Environmental influences on photoelectrical devices are critical for a reliable working condition. Among all the factors, the effect of relative humidity received less attention. Up to date, reported humidity effects were mostly about the electrical properties. The relationship of humidity and photoelectrical response has rarely been investigated. In this work, we first reported the novel dependency of photocurrent on the relative humidity in photosensitive field effect transistors. Both the amplitude and the decay time of the photocurrent were related to the humidity. To further clarify the mechanism, experiments were carefully designed to distinguish possible influence factors, and simulations were also performed to provide theoretical supports. The observed phenomenon indicated that the trapping of carriers and the polarization of dielectric both existed in the device, and were involved in the photoelectrical responses. Since the water molecules in the atmosphere had effect on both processes, the observed change in photoelectrical properties could be explained. This work clarified the origin of the novel relationship between the humidity and the photoelectrical response, thus pushed forward the photoelectrical devices to real application.

  • 2708.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Lirong
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    A flexible artificial synapse for neuromorphic system2018Ingår i: 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC), IEEE conference proceedings, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Neuromorphic computing, as a new paradigm, highlighted for its highly parallel, energy efficient features, has attracted a lot of attention. The hardware implementation for a neuromorphic system proposes the strong desire for suitable building blocks. The synaptic device is a very promising solution because of its stimulation-history-related response, which fits the nature of a neural network. In this work, an artificial synapse based on a memristive transistor fabricated by a simple process is realized. The device not only shows multi-level states which is the main feature of a memristor and is essential to hardware implementation neuromorphic system, but also exhibits physical flexibility, a feature that supports wearable and portable electronics. On this basis, a proof-of-feasibility simulation using the experimental data is performed to realize the pattern classification.

  • 2709.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Lirong
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    A photoelectrical artificial synapse for novel neuromorphic network2018Ingår i: 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Institute of Electrical and Electronics Engineers (IEEE), 2018, artikel-id 8626411Konferensbidrag (Refereegranskat)
    Abstract [en]

    The requirement of information acquisition and processing is growing rapidly. However, existing systems either suffering from inadequate processing ability or from architecture limitations being restricted by the data sensing and transmission process. In this work, a novel photoelectrical artificial synapse is developed to settle down these issues by proposing a new possibility of having a photoelectrical neuromorphic network. The photoelectrical artificial synapse has both light sensing and non-volatile multilevel states making it a suitable candidate as building block in a sensing-processing merged and photoelectrical- enabled neuromorphic system. The device also has physical flexibility to adapt to flexible and wearable systems. This work initiates a new area of novel artificial synapses and neuromorphic networks.

  • 2710.
    Yang, Kunlong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Yuan, Sijian
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zhan, Yiqiang
    Fudan University, SIST, State Key Laboratory of ASIC and System.
    Zheng, Lirong
    KTH, Skolan för elektroteknik och datavetenskap (EECS). Fudan University, SIST, State Key Laboratory of ASIC and System.
    Seoane, Fernando
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Karolinska Institutet, Department for Clinical Science, Intervention and Technology .
    Voltage dependency of photoelectrical memory in photoelectrical artificial synapseIngår i: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Recently, the newly reported photoelectrical artificial synapses have attracted a lot of intentions because of their light-memory function provided them great potential in using as a building block of new neuromorphic systems. By now, most of those devices were achieved based on the photoelectrical field effect transistors with persistent photoconductivity (PPC) effect. But the real application of these devices needs comprehensive understanding of their mechanism and the influence factors, which was rare. We here focused on the relationship of the photoelectrical response and the gate voltage, and did both experimental and theoretical investigations. A model based on indirect recombination was proposed to explain the observed phenomenon. Simulations using this model got consistent results as the experiments. Moreover, the voltage influence on specific performance metrics of the photoelectrical artificial synapses was discussed to provide direction in the practical applications.

  • 2711.
    Yang, Tao
    et al.
    Washington State Univ., USA.
    Saberi, Ali
    Stoorvogel, Anton A.
    Grip, Havard Fjaer
    Output synchronization for heterogeneous networks of introspective right-invertible agents2014Ingår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 24, nr 13, s. 1821-1844Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider the output synchronization problem for heterogeneous networks of right-invertible linear agents. We assume that all the agents are introspective, meaning that they have access to their own local measurements. Under this assumption, we then propose a decentralized control scheme for solving the output synchronization problem for a set of network topologies. The proposed scheme can also be applied to solve the output formation problem with arbitrary formation vectors. We also consider the regulation of output synchronization problem, where the output of each agent has to track an a priori specified reference trajectory, generated by an exosystem. In this case, we assume that the root agent has access to its own output relative to the reference trajectory.

  • 2712.
    Yanggratoke, Rerngvit
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Data-driven Performance Prediction and Resource Allocation for Cloud Services2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cloud services, which provide online entertainment, enterprise resource management, tax filing, etc., are becoming essential for consumers, businesses, and governments. The key functionalities of such services are provided by backend systems in data centers. This thesis focuses on three fundamental problems related to management of backend systems. We address these problems using data-driven approaches: triggering dynamic allocation by changes in the environment, obtaining configuration parameters from measurements, and learning from observations. 

    The first problem relates to resource allocation for large clouds with potentially hundreds of thousands of machines and services. We developed and evaluated a generic gossip protocol for distributed resource allocation. Extensive simulation studies suggest that the quality of the allocation is independent of the system size for the management objectives considered.

    The second problem focuses on performance modeling of a distributed key-value store, and we study specifically the Spotify backend for streaming music. We developed analytical models for system capacity under different data allocation policies and for response time distribution. We evaluated the models by comparing model predictions with measurements from our lab testbed and from the Spotify operational environment. We found the prediction error to be below 12% for all investigated scenarios.

    The third problem relates to real-time prediction of service metrics, which we address through statistical learning. Service metrics are learned from observing device and network statistics. We performed experiments on a server cluster running video streaming and key-value store services. We showed that feature set reduction significantly improves the prediction accuracy, while simultaneously reducing model computation time. Finally, we designed and implemented a real-time analytics engine, which produces model predictions through online learning.

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  • 2713. Yanson, I. K.
    et al.
    Naidyuk, Yu G.
    Fisun, V. V.
    Balkashin, O. P.
    Triputen, L. Y.
    Konovalenko, Alexander
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Vortex-like state observed in ferromagnetic contacts2010Ingår i: Journal of Physics: Conference Series, ISSN 1742-6588, Vol. 200, nr 5, s. 1-4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Point-contacts (PC) offer a simple way to create high current densities, 109 A/cm 2and  beyond,  without  substantial  Joule  heating.   We  have  shown  recently  (Nano  Letters,  7(2007) 927) that conductivity of nanosized PCs between a normal and ferromagnetic metalsexhibits bi-stable hysteretic states versus both bias current and external magnetic field – theeffect typical for spin-valve structures.  Here we report that apart from the bi-stable state athird intermediate-resistance state is occasionally observed.  We interpret this state as due toa spin-vortex in the PC, nucleated either by Oersted field of the bias current and/or by thecircular geometry of PC. The observed three-level-states in the PC conductivity testify that theinterface spins are both weakly coupled to the spins in the bulk and have depressed exchangeinteraction within the surface layer.

  • 2714.
    Yao, Sha
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Relaying without Decoding2011Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Relay networks and cooperative transmission have spurred considerable interest in recent years, promising performance improvements in, e.g., system capacity, robustness and transmission rate. In this thesis, the focus is on the so-called half-duplex relay channels, where in the system, a source node wants to transmit a message to a destination node and a relay node can potentially assist this transmission. The relay is said to be half-duplex in the sense that it cannot transmit and receive at the same time within the same frequency band. It is natural to categorize the potential relaying schemes (operations of the relay node) into two kinds. The relay can either decode the message of the source node, or it can process its received signal without decoding. The thesis investigates various schemes of the second kind and they are termed as ``relaying schemes without decoding.''

    The first part of the thesis is devoted to the approach of instantaneous relaying. The instantaneous relaying schemes belong to the relaying schemes without decoding, where the relay node is implemented by a deterministic single-variable function. Both linear and non-linear functions are investigated and it is demonstrated that the functions with sawtooth-like shape give higher achievable rates than other functions investigated. Furthermore, the work is extended to half-duplex multiple-access relay channels, where an extra source node is present. For such channels, the relay's operation is ``instantaneous'' in the sense that it is represented by a deterministic function of two variables. Essentially, the function handles the received signals from the two source nodes, combining them together and transmitting the combined signal to the destination node. Novel functions based on the Archimedean spiral mapping and sawtooth-like functions are proposed and demonstrated to perform well, using achievable rate regions and achievable sum rates of the two source nodes as figures of merit.

    In the second part of the thesis, the class of relaying schemes without decoding and with memory is investigated, where for such schemes, information theoretic source and channel coding with long codewords is used at the relay node. The two predominant schemes of such kind are the so-called compress-and-forward (CF) and quantize-and-forward (QF) schemes. The achievable rate results of the two schemes and some of their variants are derived for static channels. Furthermore, under the assumption of slow fading channels, with transmitter channel state information (CSIT) not available at the source and relay nodes, outage probabilities, expected rates as well as diversity--multiplexing trade-offs (DMT) of the respective schemes are derived and compared. In addition, to compensate for the loss due to the absence of relay CSIT, a finite-resolution feedback link from the destination node to the source node is designed for the CF and QF schemes to provide the relay node with partial CSIT, and thus, the performance of the respective schemes can be improved. Lastly, the thesis considers the problem of lack of relay CSIT from another viewpoint. The concept of hybrid digital-analog coding, as is first investigated in source-channel coding, is adapted and applied at the relay node. Such relaying schemes are termed hybrid digital-analog relaying schemes and their performance in terms of expected rate is studied. It is shown that the hybrid schemes significantly outperform the conventional digital-only (e.g., the CF scheme) and the analog-only schemes (e.g., the so-called amplify-and-forward scheme).

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 2715.
    Yao, Yanmei
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Study of Induction Machines with Rotating Power Electronic Converter2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis investigates a novel induction machine topology that uses a rotating power electronic converter. Steady-state and dynamic performance of the topology is studied to understand its operational principle. Furthermore the potential of improving its efficiency and power factor is investigated. The topology is referred to as wound rotor induction machine with rotating power electronic converter (WRIM-RPEC).

        The WRIM-RPEC topology offers the possibility to magnetize the induction machine from the rotor side by introducing a reactive voltage in the rotor. Thus, the power factor of the machine can be improved. Constant speed variable load operation can be achieved by setting the frequency of the introduced voltage. Two options of rotor winding and converter configuration in the WRIM-RPEC system are investigated. The wound rotor windings can either be open-ended and fed by a three-phase back-to-back converter or Y-connected and fed by a single three-phase converter. The dc-link in both converter configurations contains only a floating capacitor. These two configurations give different dc-link voltages at the same torque and speed.

        Two analytical steady-state models of the topology are developed in this thesis. The first model can be used to analyze the operating condition of the motor at specific speed and torque. Particularly, the operating range of speed and torque of the topology is investigated. The second model is used to analyze variable power factor operation, including unity power factor operation. Analytical calculations and measurements are carried out on a 4-pole, 1.8kW induction machine and the results are compared.

         A dynamic mathematic model is then developed for the WRIM-RPEC system for the back-to-back converter configuration. The mathematic model is then applied in Matlab/Simulink to study the dynamic performance of the system including starting, loading and phase-shifting. The simulation results are compared with measurements on the 4-pole, 1.8kW induction machine. Moreover, the simulation model using the existing Simulink blocks are studied to compare with the results obtained from the mathematic model. Furthermore, the dynamic performance of the WRIM-RPEC system with the single converter configuration is investigated. In addition, harmonic spectra analysis is conducted for the stator and rotor currents.

        In the last part of the thesis, efficiency improvement is investigated on the 4-pole induction machine when it is assumed to drive a pump load. It is shown that the efficiency can be further improved by decreasing the rotor resistance. Due to space constraints it is however difficult to decrease the rotor resistance in a 4-pole induction machine. An investigation is thus carried out on a standard 12-pole, 17.5kW squirrel-cage induction machine with inherent low power factor. The cage rotor is redesigned to a wound rotor to enable the connection of converter to the rotor windings. An analytical model is developed to design the wound rotor induction machine. The machine performance from calculations is then compared with FEM simulations with good agreement. The analytical model is further used to design several WRIMs with different dimensions and rotor slot numbers. Power factor and efficiency improvement is then explored for these WRIMs. A promising efficiency increase of 6.8% is shown to be achievable.

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  • 2716.
    Yao, Yanmei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Cosic, Alija
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Sadarangani, Chandur
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Power Factor Improvement and Dynamic Performance of an Induction Machine With a Novel Concept of a Converter-Fed Rotor2016Ingår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 31, nr 2, s. 769--775Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates an induction machine with a novel concept of the rotor fed by a converter. The stator is Y-connected and directly connected to the grid, while the rotor windings are open-ended and fed by a back-to-back converter with a floating capacitor. Power factor and efficiency improvements of the induction motor are studied with different settings of phase-shift angle between the two converters. Moreover, the dynamic performance of the induction machine is explored in MATLAB/Simulink and verified experimentally on a 1.8-kW induction machine in the laboratory. The result shows good agreement between simulation and experiment. At a constant speed, variable load operation of the induction machine is obtained by setting the frequency of the rotor voltage.

  • 2717.
    YAO, YANMEI
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Sadarangani, Chandur
    Efficiency Improvement of a 12-Pole 17.5 kWInduction Motor Using Converter-fed Wound RotorIngår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper investigates an induction machine usinga novel concept of a converter-fed rotor. The stator is directlyconnected to the grid while the rotor is fed by a converter with afloating capacitor over the dc-link. In earlier work this topologyhas shown to be capable of improving the power factor andefficiency of a 4-pole induction machine. This paper exploresthe possibility to improve the power factor and efficiency of asquirrel-cage 12-pole 17.5 kW induction machine by redesigningthe cage rotor to a wound rotor to enable connection of therotor windings to the converter. A standard 12-pole squirrelcageinduction machine (SCIM) with an inherent low powerfactor is studied. An analytical model to design the wound rotorinduction machine (WRIM) is then developed. The performanceof the designed WRIM using the analytical model is shown toagree with the results from the finite element (FEM) simulations,thus verifying the correctness of the model. The analyticalmodel is then further used to design different WRIMs withdifferent dimensions and rotor slot numbers. Performances ofthese designed WRIMs show good potential for power factorand efficiency improvement. Particularly, an optimum efficiencyimprovement of 6.8%, compared with the original SCIM, hasbeen achieved.

  • 2718.
    YAO, YANMEI
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Sadarangani, Chandur
    Optimum operating point of an induction machine using a rotor integrated converter with a floating capacitor2016Ingår i: 2016 IEEE 8th International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 98-103, artikel-id 7512268Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates an induction machine using a novel concept of rotating converter. The stator is directly connected to the grid while the rotor is fed by a rotating converter with a floating capacitor over the dc-link. An analytical method to find the operating point at specific power factor and torque is proposed in this paper, which is verified by the good agreement between calculation and experimental results. It is found that when the considered machine topology is operated at rated torque and unity power factor, the efficiency can be improved by 0.74% compared with the standard induction machine with short-circuited rotor. Moreover, the effect of reducing the rotor resistance on efficiency improvement of the induction machine at unity power factor is explored. A further efficiency improvement of 2.36% can be achieved by decreasing the rotor resistance by 30%. Furthermore, optimum efficiency of the induction machine is studied when it drives a pump and operates near the rated operation point. The result shows that an optimum efficiency, which is 3.13% higher than the standard machine, can be obtained by operating the machine at a new operation point other than the rated condition. Decreasing the rotor resistance by 30% will further increase the optimum efficiency by 1.47%. The corresponding output power will also increase with higher operation speed and load torque.

  • 2719.
    Yao, Yanmei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Sadarangani, Chandur
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Cosic, Alija
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Experimental Investigation on the Speed Control and Power Factor Improvement of a Novel Induction Machine with Rotating Power Electronic Converter2013Ingår i: Proceedings of the 10th Jubilee International Symposium on Advanced Electromechanical Motion Systems: ELECTROMOTION 2013 Cluj-Napoca, Romania, October 21-22, 2013, 2013, Vol. 20, s. 138-144Konferensbidrag (Refereegranskat)
    Abstract [en]

    A novel speed control strategy of an inductionmachine with RPEC (rotating power electronic converter) isinvestigated in this paper. The stator of the machine is directlyconnected to the power distribution network while the open-endedrotor windings are connected to a back-to-back converter. Adynamic model is developed in the three-phase reference frame.Dynamic performance of the starting process of the system isstudied, based on an 1.8kW induction machine in the laboratory.Experimental results have shown that constant speed control isachieved in a simple manner by controlling the rotor currentfrequency. Importantly the stator power factor can be improvedeffectively within a wide range of load variation including therated load. Moreover, the dc-link voltage over the capacitorbetween the two converters is considerably low which implies agreat reduction of the capacitor size.

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  • 2720. Ye, Chenhui
    et al.
    Zhu, Kun
    Fu, Hongyan
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    An All-Optical Transformer From Differential NRZ Data to Ultra-Wideband Pulse Stream2011Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, nr 9, s. 579-581Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose and experimentally demonstrate a compact and cost-effective scheme based on a fiber Sagnac structure to realize real time conversion from differential nonreturn-to-zero (NRZ) data to ultra-wideband (UWB) pulse stream. The proposed conversion system for the UWB signal generation consists of a single-wavelength laser, a phase modulator, several polarization controllers, and optical couplers. Due to the optical interference between the two phase-modulated light waves with slight phase difference in the Sagnac loop, two sharp optical pulses with opposite polarities are obtained. With proper time delay, a UWB monocycle pulse stream is generated from the original differential NRZ data. Our proposed method gives a reliable, easy, and low-cost transformer from differential NRZ signal to UWB pulse stream, and no high-speed arbitrary waveform generator (AWG) is required in this all-optical transformer.

  • 2721.
    Yika Tuesta, Alberto Stavros
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Dielectrophoresis (DEP) and electrowetting (EWOD) as Anti-fouling processes for antibacterial surfaces2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Today the medical field is struggling to decrease bacteria biofilm formation which leads to infection. Also, biomedical devices sterilization has not changed over a long period of time which has resulted in high costs for hospitals healthcare managements. The objective of this project is to investigate electro-dynamic effects by surface energy manipulation as potential methods for preventing bacteria biofilm growing on medical devices.

    Based on electrokinetic environments two different methods were tested: rejection bacteria dielectrophoretic forces feasibility by numerical simulations; and electrowetting-on -dielectric by the fabrication of golden interdigitated electrodes on silicon glass substrates covered by a Teflon layer.

    In the first experiment, numerical simulations of gold electrodes in buffer solution and frequencies were carried out to determine the forces required to reject bacteria. In the second experiment, interdigitated gold electrodes coated with a dielectric Teflon layer, were characterized in terms of breakdown voltage, dielectric adhesion and contact angle in terms of applied voltage. Finally the effect of EWOD on bacterial adhesion was tested.

    The project resulted in promising simulation results for bacteria rejection using dielectrophoresis due to the wide range of frequency that rejects the modelled bacteria. However, practical experiments such as electrowetting-on-dielectric must verify this at incubation times larger than 24 hours in spite of the Teflon non-adhesive properties.

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    MasterThesis-StavrosYika
  • 2722.
    Yilmaz, Emre
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Algorithms for estimating reverberation characteristics for single channel dereverberation2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Speech enhancement systems achieving a joint suppression of reverberation and background

    noise can be used in digital hearing aids, voice controlled systems or hands-free

    telephony. Demanding requirements for computational complexity, signal delay and speech

    quality must be fulfilled in order to achieve a satisfactory performance. The speech quality

    depends on how accurate the reverberation characteristics such as the reverberation time

    or the spectral variance of the late reverberant speech are estimated. In this thesis, an

    efficient algorithm for a blind reverberation time estimation based on maximum likelihood

    approach is introduced. The new algorithm allows to estimate reverberation times from

    a much wider range with acceptable accuracy. Variance of the late reverberant speech

    is another important quantity in dereverberation systems. Two late reverberant spectral

    variance estimation methods are compared with regard to estimation accuracy and computational

    complexity. Finally, the performance of the considered speech enhancement

    system is analyzed with the improved reverberation time estimator.

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  • 2723. Yin, X.
    et al.
    Verplaetse, M.
    Breyne, L.
    Van Kerrebrouck, J.
    De Keulenaer, T.
    Vyncke, A.
    Pierco, R.
    Vaernewyck, R.
    Spiga, S.
    Amann, M. -C
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Van Steenberge, Geert
    KTH.
    Torfs, G.
    Bauwelinck, J.
    Towards efficient 100 Gb/s serial rate optical interconnects: A duobinary way2017Ingår i: 6th IEEE Photonics Society Optical Interconnects Conference, OI 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 33-34, artikel-id 7965517Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent advances in integrated opto-electronic devices and front end circuits have made it possible to efficiently transmit very high data rates over optical links for HPC/datacenter applications. This paper reviews our current progress towards serial 100-Gb/s optical interconnects, with emphasis on electrical duobinary (EDB) modulation.

  • 2724.
    Yu, Xingang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Developments for Improved Performance Vertical-Cavity Surface Emitting Lasers2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The vertical-cavity surface-emitting laser (VCSEL) is a type of laser diode that emits light from the surface of the chip from which it is manufactured rather than from a cleaved edge as so far has been common for most telecommunication lasers. VCSEL’s low cost, high power efficiency and low power consumption properties make it a very attractive signal source for many applications such as fiber optical communication, optical interconnects, 3D sensing, absorption spectroscopy, laser printing, etc.

    In this work, we have developed and evaluated new designs and technologies for extending the performance of VCSELs based on the GaAs material system. A novel scheme for single-mode emission from large size VCSELs, with active region size up to 10 μm, is proposed and discussed. Oxide-free designs of the VCSEL structure either based on an epitaxially regrown p-n-p layer or a buried tunnel junction (BTJ) for lateral current confinement are fabricated and characterized; the latter scheme yielding significant dynamic and static performance improvement as compared to epitaxially regrown design. In addition, the first room-temperature operation of a heterojunction bipolar transistor (HBT) 980nm VCSEL, a so-called transistor-VCSEL, is demonstrated. This novel three-terminal operational VCSEL is believed to have the potential for a ultrahigh modulation bandwidth due to altered carrier dynamics in the cavity region.

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    Thesis
  • 2725. Yu, Yufeng
    et al.
    Xiong, Jiang
    Li, Hui
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    An Electrically Small Frequency Reconfigurable Antenna With a Wide Tuning Range2011Ingår i: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 10, s. 103-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An electrically small frequency-reconfigurable antenna with a very wide tuning band is proposed. Three varactor diodes are used to achieve the tunable capacitance. With a modified feeding structure, the measured tuning range of the fabricated antenna reaches from 457.5 to 894.5 MHz, and the tuning band enhancement is also explained through an equivalent circuit analysis.

  • 2726.
    Yuan, Xiaolong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wideband Sigma-Delta Modulators2010Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Sigma-delta modulators (SDM) have come up as an attractive candidatefor analog-to-digital conversion in single chip front ends thanks to the continuousimproving performance. The major disadvantage is the limited bandwidthdue to the need of oversampling. Therefore, extending these convertersto broadband applications requires lowering the oversampling ratio (OSR) inorder. The aim of this thesis is the investigation on the topology and structureof sigma-delta modulators suitable for wideband applications, e.g. wireline orwireless communication system applications having a digital baseband aboutone to ten MHz.It has recently become very popular to feedforward the input signal inwideband sigma-delta modulators, so that the integrators only process quantizationerrors. The advantage being that the actual signal is not distorted byopamp and integrator nonlinearities. An improved feedforward 2-2 cascadedstructure is presented based on unity-gain signal transfer function (STF). Theimproved signal-to-noise-ratio (SNR) is obtained by optimizing zero placementof the noise transfer function (NTF) and adopting multi-bit quantizer.The proposed structure has low distortion across the entire input range.In high order single loop continuous-time (CT) sigma-delta modulator, excessloop delay may cause instability. Previous techniques in compensation ofinternal quantizer and feedback DAC delay are studied especially for the feedforwardstructure. Two alternative low power feedforward continuous-timesigma-delta modulators with excess loop delay compensation are proposed.Simulation based CT modulator synthesis from discrete time topologies isadopted to obtain the loop filter coefficients. Design examples are given toillustrate the proposed structure and synthesis methodology.Continuous time quadrature bandpass sigma-delta modulators (QBSDM)efficiently realize asymmetric noise-shaping due to its complex filtering embeddedin the loops. The effect of different feedback waveforms inside themodulator on the NTF of quadrature sigma-delta modulators is presented.An observation is made that a complex NTF can be realized by implementingthe loop as a cascade of complex integrators with a SCR feedback digital-toanalogconverter (DAC), which is desirable for its lower sensitivity to loopmismatch. The QBSDM design for different bandpass center frequencies relativeto the sampling frequency is illustrated.The last part of the thesis is devoted to the design of a wideband reconfigurablesigma-delta pipelined modulator, which consists of a 2-1-1 cascadedmodulator and a pipelined analog-to-digital convertor (ADC) as a multi-bitquantizer in the last stage. It is scalable for different bandwidth/resolutionapplication. The detail design is presented from system to circuit level. Theprototype chip is fabricated in TSMC 0.25um process and measured on thetest bench. The measurement results show that a SNR over 60dB is obtainedwith a sampling frequency of 70 MHz and an OSR of ten.

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    FULLTEXT01
  • 2727.
    Yuan, Zhao
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Hesamzadeh, Mohammad Reza
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    A Distributed Economic Dispatch Mechanism to Implement Distribution Locational Marginal Pricing2018Ingår i: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address the challenges of power flow computation and network operator coordination to implement distribution locational marginal pricing (DLMP) in this paper. Compared with other dynamic pricing schemes, DLMP can give clearer economic signals regarding distributed energy resources (DERs) investment, demand side response, congestion management and network reinforcement. Without neglecting the power loss of distribution network, the second-order cone AC optimal power flow (SOPF) model is used here to calculate DLMP. A distributed economic dispatch mechanism based on the modified Benders decomposition and distributed generation cost (DGC) is proposed to reduce the dispatch complexity in facing high penetration of DERs. The key contribution is that we take the tie-line power flow as the complicating variable to formulate the modified Benders decomposition algorithm. The concept of DGC is proposed to reallocate the global dispatch cost to economically incentivize the regional network operators for coordination. The distributed economic dispatch mechanism is implemented in GAMS grid computing platform. Numerical results show that SOPF can give accurate power flow and DLMP results. The fast convergence of the proposed distributed dispatch is guaranteed by the convexity of the SOPF model and efficient grid computing technique.

  • 2728.
    Yuan, Zhao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Reza Hesamzadeh, Mohammad
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Hierarchical coordination of TSO-DSO economic dispatch considering large-scale integration of distributed energy resources2017Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 195, s. 600-615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a hierarchical coordination mechanism for coordinating the economic dispatch of transmission system operator (TSO) and distribution system operator (DSO). The challenge of dispatching large-scale distributed energy resources (DERs) is addressed. The coordination problem of dispatching energy and reserve is formulated. Benders decomposition is the underlying mathematical foundation of the proposed hierarchical coordination mechanism. We define the generalized bid function to approximate the dispatch cost of distribution network by a series of affine functions. The generalized bid function is communicated from DSO to TSO. By using convex AC optimal power flow model, the convergence of hierarchical coordination is guaranteed. A grid computing structure in General Algebraic Modeling System (GAMS) to accelerate the computation is proposed. The generalized bid function is simulated for various test cases. We also demonstrate the effect of DERs on the voltage magnitude and phase angle. The numerical results show that the hierarchical coordination using the generalized bid function converges to very close results compared with the results of centralized dispatch. Hierarchical coordination is capable of managing various network congestion scenarios and power loads. The generalized bid function provides a unified format of communication between TSO and DSO.

  • 2729. Zamzam, D. M.
    et al.
    Abd El Ghany, M. A.
    Hofmann, K.
    Ismail, Muhammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Highly reliable and power efficient NOC interconnects2011Ingår i: NORCHIP, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Network on chip (NOC) architecture interconnects consume significant amount of power, have a large propagation delay and are susceptible to error due to deep sub-micron (DSM) noise. Major challenge that NOC design expected to face is related to intrinsic reliability. By incorporating error control coding schemes along the NOC interconnects, NOC architectures are able to provide correct functionality in the presence of different transient noise source. In this paper we present a novel coding scheme that increase the reliability of the NOC where the area is reduced by 19% and the consumed power by NOC interconnects is decreased by 51%. Butterfly fat tree architecture consumes the minimum power as compared to other NOC architectures.

  • 2730.
    Zandi Shafagh, Reza
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Development and fabrication of OSTE and OSTE+ cartridges for the integration of quartz crystal microbalance biosensors2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The introduction of lab-on-a chip (LOC) devices introduced hopes of more advanced and rapid point-of-care diagnostics and pathogen detection, especially when used in combination with miniature and sensitive biosensors. Nevertheless, the commercialization of such devices has been limited, partly due to issues in achieving a facile and economically viable packaging using cost-effective materials. Newly developed thermosetting polymers address some of the issues by offering industry like material properties (i.e. thermoplastics) along with straight-forward back-end processing, e.g. adaptable surface modification and low temperature dry-bonding. Thus, such polymers have a great potential to be used for the fabrication of LOC-devices with integrated biosensors.

    In this thesis project, a novel approach for the integration and packaging of quartz crystal microbalance (QCM) biosensor chips, aimed for Norovirus detection, has been developed. The work initially evaluates the properties of novel thermosetting polymers for LOC cartridge applications. The study continues with an investigation of new polymer formulations, which features more favorable material properties and versatile back-end processing compared to standard OSTE. Lastly, microfluidic cartridges based on a novel thermosetting polymer were successfully fabricated and integrated with a gold-coated quartz crystal. The bond interfaces were homogenous, void-free and leak-tight. The devices were successfully tested in terms of noise, drift and response in a flow-through setting and upon exposure of bovine serum albumin protein.

  • 2731.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research, Västerås.
    Sandulescu, P.
    ABB Corporate Research.
    Model-based synchronous machine control with compensation of model inaccuracies and instantaneous flux weakening capabilities2016Ingår i: Proceedings of the 8th IET International Conference on Power Electronics, Machines and Drives (PEMD), Institution of Engineering and Technology, 2016, Vol. 2016, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a model-based current/torque control strategy for synchronous machines, where the magnetic model mismatches are compensated in real time and the flux weakening operation is obtained without the need of an external voltage regulation loop. Starting from an initial (and potentially wrong) knowledge of the non-linear current-to-flux linkage relation in the form of a look-up-table, a combination of feedforward actions, compensating mechanisms and binary searches are used to achieve the target during real-time operation. The algorithm is implemented in a laboratory test bench and successfully verified with experiments on an 11-kW synchronous reluctance machine, proving the feasibility of the proposed approach.

  • 2732.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research.
    Sandulescu, P.
    ABB Corporate Research.
    Stator reference frame approach for DC injection-based stator resistance estimation in electric drives2015Ingår i: Proceedings of the 11th IEEE International Conference on Power Electronics and Drive Systems (PEDS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 867-872, artikel-id 7203391Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work discusses an online stator resistance estimation method for synchronous machines. Multiple improvements are provided with respect to a similar method already been used for induction machines. The method is based on the temporary injection of a DC voltage in the machine phases during normal operation. The stator resistance estimation is obtained by means of the Ohm's law. The proposed scheme works entirely in the stator fixed reference frame, without the need of any machine parameter. The selection of the DC injection level is discussed, as well as the countermeasures for reducing the spurious harmonics appearing in the currents and the torque when the machine is speed- and current-regulated. In particular, minimum electric loss and minimum torque ripple due to the injection is achieved. Moreover, as an alternative to conventional low-pass filtering of the measured signals, it is shown that the resistance estimation can be obtained by averaging the signals over few electric periods. Experiments prove the validity of the proposed approach.

  • 2733.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research.
    Zigliotto, M.
    University of Padova.
    Permanent magnet synchronous machines flux linkage estimation with zero steady-state error and its field-programmable gate array implementation2015Ingår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 9, nr 4, s. 332-343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper analyses a combined current model-voltage model estimator for flux linkages in permanent magnet synchronous machines, with the capability of converging to exact flux estimation even in presence of mismatches because of magnetic saturation. As a trend in next-generation electric drives, the whole algorithm, including both the flux estimator and the standard field-oriented control, has been implemented in a field-programmable gate array (FPGA) chip. Simulations and experimental tests, along with some figures for the FPGA selection, have been included in the study.

  • 2734.
    Zanuso, Giovanni
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Peretti, Luca
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Sandulescu, Paul
    ABB Oy, Finland.
    Model-based flux weakening strategy for synchronous machines without additional regulators2018Ingår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 12, nr 9, s. 1283-1290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study proposes a model-based control strategy for flux weakening operation of a synchronous reluctance machine, with a methodology that is extendible to any synchronous machine. The strategy leverages in the presence of digital non-linear models that describe the relation between currents and flux linkages in the machine. Such models are usually needed for conventional maximum-torque-per-ampere control and sensorless control, but here they are exploited to achieve flux-weakening operation without the need of flux weakening regulators, ensuring a seamless transition between the operating regions of the machine. The external voltage regulation loop for flux weakening is thus eliminated and substituted by a combination of look-up tables and binary searches, which are executed within one digital control period and which generate the required current and voltage references that fulfil the drive limitations. The method can also be coupled with mechanisms to compensate for magnetic parameter inaccuracies, to achieve an accurate tracking of the reference torque. The proposed solution is simulated and validated in a laboratory test bench on an 11 kW synchronous reluctance machine.

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  • 2735.
    Zarei, Tahereh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Morozovska, Kateryna
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Laneryd, Tor
    ABB AB Corporate Research.
    Hilber, Patrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Wihlen, Malin
    Ellevio AB.
    Olle, Hansson
    Independent Consultant at Ellevio AB.
    Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration2019Ingår i: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 106, s. 598-606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An increasing share of renewable energy on the electricity market creates the need for economic and efficient production, operation and integration technologies, associated with the specific behavior of renewable energy sources (RES). Dynamic rating (DR) provides a possibility to apply improvements to the system both during planning and operation stages. The DR benefits are well described in various literature sources. However, DR is often focused on more efficient exploitation of power lines, not power transformers. Power transformers are costly equipment and their efficient usage and planning can have drastic effect on total costs.

    Our analysis focuses on the dynamic transformer rating (DTR) for wind energy applications. The main objective is to study reliability effects of DTR from the component perspective. We utilize existing knowledge about transformer heat balance models from IEC and IEEE standards to obtain information on the loss of life (LOL) of the transformer under investigation and propose possible improvements for the system in question. The method can be employed for identifying the appropriate transformer size by taking into account ambient temperature and load variations and then overloading the transformer beyond nameplate ratings. The reliability of the proposed application is ensured by calculating the risk of overloading the transformer for each day of the year. A risk of overloading is quantified as LOL of the transformer. The risk is presented as a function of ambient temperature and duration of an overload. The final step consists of an economic analysis, which demonstrates economic benefits of DTR application.

  • 2736.
    Zdanowski, Mariusz
    et al.
    Warsaw University of Technlogy.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Kostov, Konstantin
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Barlik, R.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Design and Evaluation of Reduced Self-Capacitance Inductor for Fast-Switching SiC BJTdc/dc Converters2012Ingår i: Power Electronics and Motion Control Conference (EPE/PEMC), 2012 15th International, IEEE , 2012, s. DS1a.41-DS1a.47Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper presents design, measurements and evaluation of the inductor with reduced self-capacitance. As an reference inductor with the same parameters but non-optimized self-capacitance is chosen. Differences in the parasitic capacitance of the inductor are validated by four measurement methods and experimentally confirmed on a 2 kW, 100 kHz dc/dc converter with silicon carbide BJTs. When the low-capacitance inductor is applied the switching performance is better, especially high-frequency resonances are limited. Additionally, it was found that the power losses were reduced by approximately 20%.

  • 2737.
    Zdanowski, Mariusz
    et al.
    Warsaw University of Technlogy.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Kostov, Konstantin
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    The Role of the Parasitic Capacitance of the Inductorin Boost Converters with Normally-On SiC JFETs2012Ingår i: 2012 7th International Power Electronics and Motion Control Conference (IPEMC), IEEE conference proceedings, 2012, s. 1842-1847Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper the impact of the parasitic capacitance ofthe inductor on the performance of a fast-switching boostconverters with SiC JFETs is discussed. Two inductor designs,one conventional and another with a space between the windinglayers, are investigated and their parasitic capacitances aremeasured by different methods. The air-gap between the windinglayers reduced the inductor self-capacitance more than 8 times.The two inductors were used in a 2 kW, 100 kHz boost converterwith a normally-on SiC JFET and their performance wascompared. When the inductor with a low self-capacitance wasused, there were fewer oscillations during the switchingtransients and the losses were reduced about 16 %.

  • 2738.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Dielectric issues for silicon carbide MOS devices1998Ingår i: 29th IEEE Semiconductor Interface Specialists Conference, 1998Konferensbidrag (Refereegranskat)
  • 2739.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Electrical and transport properties of AlN1999Ingår i: Properties, processing and applications of gallium nitride and related semiconductors, Institution of Engineering and Technology, 1999, 1, s. 40-Kapitel i bok, del av antologi (Refereegranskat)
  • 2740.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Process technology for silicon carbide devices2002 (uppl. 1)Bok (Övrigt vetenskapligt)
  • 2741.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Dahlquist, Fanny
    Lundberg, Nils
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Rottner, K.
    Ramberg, L.
    Junction barrier Schottky diodes in 6H SiC1998Ingår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 42, nr 9, s. 1757-1759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Junction barrier Schottky (JBS) diodes in 6H SiC have been fabricated and characterised electrically. This device, demonstrated in silicon technology, has the advantage of a low forward voltage drop comparable to that of Schottky diodes, as well as a high blocking voltage and low reverse leakage current of a pn junction. This is especially attractive for wide bandgap materials such as SiC in which pn junctions have a large forward voltage drop. The devices were capable of blocking up to 1100 V with a leakage current density of 0.15 A cm-2, limited by the leakage when the drift region was fully depleted, or breakdown of the SiC material itself. The forward conduction was limited by an on-resistance of 20 mΩ cm2, resulting in forward voltage drops of 2.6 V at 100 A cm-2. © 1998 Published by Elsevier Science Ltd. All rights reserved.

  • 2742.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Dahlquist, Fanny
    Lundberg, Nils
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Rottner, Kurt
    Ramberg, Lennart
    High voltage silicon carbide Junction Barrier Schottky rectifiers1997Ingår i: Proceedings of the IEEE Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits, Ithaca, NY, USA, 1997, nr Piscataway, NJ, United States, s. 256-263Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Junction Barrier Schottky (JBS) diode has the advantage of a low forward voltage drop comparable to that of Schottky diodes, as well as a high blocking voltage and low reverse leakage current of a pn diode. This device, originally demonstrated in silicon technology, is especially attractive for wide bandgap materials such as silicon carbide (SiC) in which pn diodes have a large forward voltage drop. Two different JBS designs in 6H SiC have been fabricated, and the electrical characteristics have been compared to Schottky and pn diodes on the same wafer. Although the ion implanted pn diodes had remaining implant damage, the JBS diodes worked well. The JBS diodes were capable of blocking up to 1100 V with a leakage current density of 0.15 A/cm2, limited by the leakage when the drift region was fully depleted, or breakdown of the SiC material itself. The forward conduction was limited by an on-resistance of 20 mΩcm2.

  • 2743.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Hedayati, Raheleh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Kargarrazi, Saleh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Lanni, Luigia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Mardani, S.
    Norström, H.
    Rusu, Ana
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Suvanam, Sethu Saveda
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Tian, Ye
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Bipolar integrated circuits in SiC for extreme environment operation2017Ingår i: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, nr 3, artikel-id 034002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silicon carbide (SiC) integrated circuits have been suggested for extreme environment operation. The challenge of a new technology is to develop process flow, circuit models and circuit designs for a wide temperature range. A bipolar technology was chosen to avoid the gate dielectric weakness and low mobility drawback of SiC MOSFETs. Higher operation temperatures and better radiation hardness have been demonstrated for bipolar integrated circuits. Both digital and analog circuits have been demonstrated in the range from room temperature to 500 °C. Future steps are to demonstrate some mixed signal circuits of greater complexity. There are remaining challenges in contacting, metallization, packaging and reliability.

  • 2744.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Koo, S. -M
    Danielsson, Erik
    Liu, W.
    Lee, S. -K
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lee, H. -S
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Challenges for High Temperature Silicon Carbide Electronics2003Ingår i: Materials Research Society Symposium - Proceedings, San Francisco, CA, 2003, Vol. 764, s. 15-25Konferensbidrag (Refereegranskat)
    Abstract [en]

    Silicon carbide has been proposed as an excellent material for high-frequency, high-power and high-temperature electronics. High power and high frequency applications have been pursued for quite some time in SiC with a great deal of success in terms of demonstrated devices. However, self-heating problems due to the much higher power densities that result when ten times higher electrical fields are used inside the devices needs to be addressed. High-temperature electronics has not yet experienced as much attention and success, possibly because there is no immediate market. This paper will review some of the advances that have been made in high-temperature electronics using silicon carbide, starting from process technology, continuing with device design, and finishing with circuit examples. For process technology, one of the biggest obstacles is long-term stable contacts. Several device structures have been electrically characterized at high temperature (BJTs and FETs) and will be compared to surface temperature measurements and physical device simulation. Finally some proposed circuit topologies as well as novel solutions will be presented.

  • 2745.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lanni, Luigia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Future high temperature applications for SiC integrated circuits2011Konferensbidrag (Refereegranskat)
  • 2746.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lanni, Luigia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Future high temperature applications for SiC integrated circuits2012Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, nr 7, s. 1647-1650Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main advantage of SiC is its high critical field for breakdown. This leads to much lower on-resistance for high voltage devices compared to silicon, but at a higher price that has to be offset by system gains. However, it is not straightforward to exploit this advantage, which is clear from the many different device types that are presently being commercialized. There are other advantages of SiC yet to be fully investigated: the possibility of high temperature operating electronics and radiation hard devices. If integrated circuits in SiC are also available, the system advantage is larger. Here temperature ranges higher than that of SOI should be aimed at, and some of these new application areas will be described. An overview of IC research will be ended with a description of our selected technology operated at 300 °C.

  • 2747.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Liu, Wei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Thermal modeling of multi-finger SiC power MESFETs2005Ingår i: 2005 International Semiconductor Device Research Symposium, 2005, Vol. 2005, s. 290-291Konferensbidrag (Refereegranskat)
    Abstract [en]

    The high critical electrical field of silicon carbide makes it possible to fabricate high power SiC devices, which can handle much higher power than the traditional silicon and gallium arsenide power devices1. SiC power MESFET is one of such devices available on the market for RF applications 2. Despite the high thermal conductivity of the material, the SiC devices may suffer severe self-heating when operating at very high power levels, especially if the gate pitch is small3. The self-heating phenomena of one- and multi-fingered SiC MESFETs were studied through 2D electro-thermal simulations and 2D and 3D steady-state thermal simulations. The device performance degradation caused by self-heating was observed, and is more profound for devices operating at room temperature than for devices working at elevated temperatures. The junction temperature and temperature distribution of devices fabricated on SiC substrates were estimated through both electro-thermal simulations and steady-state thermal simulations, and the results agree well (Fig. 1). Different layouts and gate pitches were investigated to optimize the trade-off between maximum operating temperature and the longest signal path, which limits the size of high-frequency devices (Fig. 2. and 3.).

  • 2748.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Wongchotigul, K.
    Spencer, M. G.
    Harris, C. I.
    Wong, S. S.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Formation and high frequency CV-measurements of aluminum/aluminum nitride/6H silicon carbide structures1996Ingår i: Materials Research Society Symposium - Proceedings, San Francisco, CA, USA, 1996, Vol. 423, nr Pittsburgh, PA, United States, s. 667-672Konferensbidrag (Refereegranskat)
    Abstract [en]

    Undoped single crystalline aluminum nitride films were grown by metal organic chemical vapor deposition (MOCVD) at 1200 °C. The precursors used were trimethylaluminum (TMA) and ammonia (NH3) in a hydrogen carrier flow, at a pressure of 10 Torr. Silicon carbide substrates of the 4H or the 6H polytype with an epilayer on the silicon face, were used to grow the 200 nm thick AlN films. Aluminum was evaporated and subsequently patterned to form MIS capacitors for high frequency (400 kHz) capacitance voltage measurements at room temperature. It was possible to measure the structure and characterize accumulation, depletion and deep depletion. However, it was not possible to invert the low doped SiC epilayer at room temperature. From an independent optical thickness measurement the relative dielectric constant of aluminum nitride was calculated to be 8.4. The films were stressed up to 50 Volts (2.5 MV/cm) without breakdown or excessive leakage currents. These results indicate the possibility to replace silicon dioxide with aluminum nitride in SiC field effect transistors.

  • 2749.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    A novel UMOS capacitor test structure for SiC devices1996Ingår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 39, nr 9, s. 1396-1397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we propose the use of U-grooved MOS capacitors to investigate oxides intended for U-grooved MOSFETs and IGBTs in silicon carbide. The UMOS capacitor uses only two mask layers, and has vertically etched walls and a gate contact that overlaps the step. We have manufactured UMOS capacitors in n-type 6H SiC with dry thermal gate oxides, and compared the capacitance voltage characteristics to those of flat reference capacitors. It was found that the general appearance of capacitance-voltage curves was unchanged by the addition of the vertical grooves, although the leakage through the oxide was increased. The oxide thickness on the sidewalls was approximately the same as on the flat parts of the devices. Copyright © 1996 Elsevier Science Ltd.

  • 2750.
    Zetterling, Carl-Mikael
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Comparison of thermal gate oxides on silicon and carbon face p-type 6H silicon carbide1994Ingår i: Materials Research Society Symposium - Proceedings, San Francisco, CA, USA, 1994, Vol. 339, nr Pittsburgh, PA, United States, s. 209-214Konferensbidrag (Refereegranskat)
    Abstract [en]

    Monocrystalline 6H silicon carbide samples (n-type and p-type) with both carbon face and silicon face have been used to investigate gate oxide quality. The oxides were thermally grown in a dry oxygen ambient at 1523 K with or without the addition of TCA (Trichloroethane), or in wet pyrogenic steam at 1473 K. POCl3 doped polysilicon gates were used for electrical characterisation by capacitance-voltage measurements and breakdown field measurements. Large flatband voltage shifts indicate fixed oxide charges up to 1013 cm-2. The incorporation of aluminum in the oxides was monitored using SIMS (Secondary Ion Mass Spectrometry). Surprisingly high signals were interpreted as evidence of an aluminum-oxygen compound having been formed (ie Al2O3).

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