Modular multilevel converters require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Assuming that the individual capacitor-voltage sharing is managed effectively, an open-loop strategy has been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable. Experimental verification on a three-phase 10-kVA prototype is presented.

Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

A multiagent-based distribution automationsolution is proposed to be used in the distribution of selfhealinggrids to solve the service restoration part of theFault Location, Isolation and Service Restoration (FLISR)task. The solution reduces the grid topology to an undirectedweighted graph and executes a distributed implementationof Prim’s minimum spanning tree algorithm tosolve the problem. The solution is compliant with state-ofthe-art standards within smart grids, including but not limitedto IEC61850. To test the performance of the algorithm,a testbed is assembled consisting of a physical dc gridmodel and several Arduino microcontrollers and RaspberryPi computers. The test results show that the proposedalgorithm can handle complex FLISR scenarios.

This paper presents a novel gas microvalve design concept, in which a flow control gate is opened by a pneumatic pressure and closed by a shape memory alloy actuator, allowing large flow control. Two different design variations were fabricated using a novel wafer-level Au-Si eutectic bonding process for TiNi to silicon integration. The resulting microvalves demonstrate a record pneumatic performance per footprint area; a microvalve with a footprint of only 1 x 3.3 mm(2) successfully controls a flow difference of 3100 sccm at a pressure drop of 70 kPa using a power of 0.35 W.

In a future scenario where many devices can be controlled using the voice, easy and intuitive access will be crucial for avoiding cognitive overload when users are faced with many different systems and interaction models. We propose a model for interaction with spoken language interfaces applied to heterogeneous tasks for service robots, based on the idea of using a family of lifelike characters,, We argue that we can signal important features of the speech interface by using certain visual cues. The aim is to facilitate learning and transfer between interfaces. We discuss challenges for dialogue design affecting learnability in the light of the speech interface constructed for our full-scale robot prototype CERO.

Theory for the dynamics of modular multilevel converters is developed in this paper. It is shown that the sum capacitor voltage in each arm often can be considered instead of the individual capacitor voltages, thereby significantly reducing the complexity of the system model. Two selections of the so-called insertion indices, which both compensate for the sum-capacitor-voltage ripples, are considered. The dynamic systems which respectively result from these selections are analyzed. An effective dc-bus model, which takes into account the contribution from the submodule capacitors, is obtained. Finally, explicit formulas for the stationary sum-capacitor-voltage ripples are derived.

In this paper, a unified theory for sensorless fluxestimation and vector control of induction motors and nonsalientpermanent-magnet synchronous motors (PMSMs) is developed.It is shown that an estimator and vector controller for one of themotor types can also be applied to the other, with only minormodifications necessary. Two candidate estimators are considered:a variant of the well-known “voltage model” (VM) and aphase-locked-loop-type speed and position estimator. These areapplied to both motor types, and evaluated experimentally. Forthe nonsalient PMSM, an important result is that synchronizationcan be guaranteed from any initial rotor position.

A computationally efficient speed and position estimation algorithm, generally applicable to AC motor drives, is designed and analyzed. Applications include: (a) sensorless permanent-magnet and reluctance synchronous motor drives using the fundamental excitation as information source; (b) sensorless drives using saliency and signal injection; and (c) sensored drives using resolvers. Particular attention is given for case (a). Low parameter sensitivity in the entire speed range (except at low speeds for the reluctance motor)-implying a small position estimation error-and good dynamic properties at nominal speeds are verified.

The torque-maximizing field-weakening controlscheme proposed by Kim and Sul is developed further. Theperformance under imperfect field orientation conditions isinvestigated, and it is shown that an overestimated—rather thanan underestimated—model leakage inductance should be used. Aslightly modified algorithm, which offers better robustness andreduced computational complexity, is presented. The importance,for good performance, of combining the scheme with currentand speed controllers featuring antiwindup and improved disturbancerejection is emphasized. The dynamics of the resultingclosed-loop system are analyzed. Obtained in the process are rulesfor selection of all controller parameters, allowing tuning withouttrial-and-error steps. Good performance of the resulting systemis verified experimentally.

The time delay in the current control loop of a grid-connected voltage-source converter (VSC) may cause destabilization of electrical resonances in the grid or in the VSC's input filter. Instability is prevented if the input admittance of the VSC can be made passive. This paper presents an analytical controller design method for obtaining passivity. The method is equally applicable to single-and three-phase systems, i.e., in the latter case, for both stationary-and synchronous-frame control. Simulations and experiments verify the theoretical results.

In this paper, a variant of the well-known voltage model is applied to rotor position estimation for sensorless control of nonsalient permanent-magnet synchronous motors (PMSMs). Particular focus is on a low-speed operation. It is shown that a guaranteed synchronization from any initial rotor position and stable reversal of rotation can be accomplished, in both cases under load. Stable rotation reversal is accomplished by making the estimator insensitive to the stator resistance. It is also shown that the closed-loop speed dynamics are similar to those of a sensored drive for speeds above approximately 0.1 per unit, provided that the model stator inductance is underestimated. Experimental results support the theory.

The stacked polyphase bridges converter has gained increasing interest in recent years due to its modular design and easy adaption to different power levels. The real-time control and dynamic data transmission of a stacked polyphase bridges converter consisting of a number of submodules are challenging tasks. For the reason that the distributed control architecture can maintain the benefit of modularity, such an approach dedicated for the stacked polyphase bridges converter is presented in this paper. Suitable communication techniques and synchronization techniques for the presented architecture are discussed. In addition, based on a dynamic model of the converter, the sensitiveness of the distributed control system to communication bandwidth and delay is studied on an experimental prototype.

The stacked polyphase bridges (SPB) converter has gained increasing interest in recent years due to its modular design and easy adaption to different power levels. The realtime control and dynamic data transmission of an SPB converter consisting of a number of submodules are challenging tasks. For the reason that the distributed control architecture can maintain the benefit of modularity, such an approach, dedicated for the SPB converter is presented in this paper. Suitable communication techniques and synchronization techniques for the presented architecture are discussed. In addition, based on a dynamic model of the converter, the sensitiveness of the distributed control system to communication bandwidth and delay is studied on an experimental prototype.

This paper analyzes the exponential stability of a discrete-time linear plant in feedback control over a communication network with N sensor nodes, dynamic quantization, large communication delays, variable sampling intervals, and round-robin scheduling. The closedloop system is modeled as a switched system with multiple-ordered time-varying delays and bounded disturbances. We propose a time-triggered zooming algorithm implemented at the sensors that preserves exponential stability of the closed-loop system. A direct Lyapunov approach is presented for initialization of the zoom variable. The proposed framework can be applied to the plants with polytopic type uncertainties. The effectiveness of the method is illustrated on cart-pendulum and quadruple-tank processes.

A systematic study of the standard SPICE model of the diode in the case of simulations of power diodes in power electronic applications shows the limits of accuracy with respect to experiments. Therefore, the interest in such a model in power electronic applications is comparable to the high-low resistance model.

A high-voltage tapped-inductor buck converter utilizing a novel autonomous high-voltage valve is presented in this paper. Its application as auxiliary power supply for high-power cascaded-converter submodules is discussed, followed by a presentation of the most challenging problems in designing a low-power high-voltage step-down converter. The TI-buck converter topology is analyzed, which together with the novel autonomous high-voltage valve overcomes most of the problems. Analytical expressions describing the operation as well as circuit simulations are presented. Finally, an experimental evaluation of a 3-kV 70-W prototype converter utilizing the proposed autonomous high-voltage valve with series-connected super-junction MOSFETs is presented.

This paper theoretically introduces and develops a new operation diagram (OPD) and parameter estimator for the synchronous reluctance machine (SynRM). The OPD demonstrates the behavior of the machine's main performance parameters, such as torque, current, voltage, frequency, flux, power factor (PF), and current angle, all in one graph. This diagram can easily be used to describe different control strategies, possible operating conditions, both below- and above-rated speeds, etc. The saturation effect is also discussed with this diagram by finite-element-method calculations. A prototype high-performance SynRM is designed for experimental studies, and then, both machines' [corresponding induction machine (IM)] performances at similar loading and operation conditions are tested, measured, and compared to demonstrate the potential of SynRM. The laboratory measurements (on a standard 15-kW Eff1 IM and its counterpart SynRM) show that SynRM has higher efficiency, torque density, and inverter rating and lower rotor temperature and PF in comparison to IM at the same winding-temperature-rise condition. The measurements show that the torque capability of SynRM closely follows that of IM.

Efficient torque control of induction motor drives in combination with resonant dc-link input filters can lead to a type of stability problem that is known as negative impedance instability. An often-proposed solution to this problem is the nonlinear system stabilizing controller (NSSC). Stability is usually analyzed under the simplifying assumption of perfect torque control. This indicates that the NSSC stabilizes the drive at any operating point. In this paper, however, we show power laboratory experiments where the NSSC stabilization fails. An improved framework for stability analysis and synthesis of stabilization, based on a linear. feedback model of the drive, is therefore proposed. With this approach, effects of time delays can easily be included, and stability margins can be directly established from measurements. To solve the indicated problems with NSSC, a stabilization controller that considers the practical limitations of torque control is derived. In the design of the stabilization controller, the tradeoff between damping and acceptable torque control is also explicitly taken into account. The proposed stabilization scheme is implemented and evaluated on a hardware-in-the-loop simulator as well as in a power laboratory. The results show that the proposed method outperforms the NSSC method.

In this paper, the thermal impact of using different impregnation materials on high-performance liquid-cooled electric machines is studied. In this regard, varnish, Epoxylite, and a silicone-based thermally conductive material are considered. To study thermal effects of using different impregnation materials in theory, an advanced lumped-parameter thermal model of the studied electric machines is developed. In addition to the simulation studies, three identical induction machines using the aforementioned materials are manufactured and evaluated. Experimental tests are carried out at a wide range of current magnitudes and cooling conditions. A good agreement between the temperature measurements and corresponding simulation results is observed. It is demonstrated that using innovative thermally conductive materials in the stator slots and the end winding bodies of liquid-cooled electric machines results in a significant reduction in the winding hot spot temperature. Additionally, the influence of the critical parameters on the impregnation material performance, e. g., impregnation goodness and slot fill factor, is studied.

This paper presents a practical approach to modeland analyze transient thermal effects in open air-cooled electrictraction motors. The developed thermal modeling method enablesaccurate estimation of temperature in critical parts of the motorincluding winding and bearing. Advantages of both numericaland analytical modelling methods are exploited with the aim ofrealizing accurate estimation of hot spot temperatures in tractionmotors while keeping the computation time within a reasonablerange. Computational fluid dynamics (CFD) simulations arecarried out to model the cooling fan’s performance and airflow distribution in the motor in order to provide heat transferboundary inputs to the developed combined finite element (FE)and lumped parameter (LP) thermal model. The combinationof the FE and LP models keeps the size of the model relativelysmall and enables running transient calculations reasonably fast.Also, the developed model provides the possibility to studythe influence of stator and rotor duct blockages on the motorthermal performance which is a common root of failure intraction applications during operation in dirty environments. Theproposed thermal model is verified using experimental results ona traction motor equipped with temperature sensors in motorcritical parts and a good agreement between estimated andmeasured temperatures is achieved. Finally, a calibrated fullyanalytical model using the abovementioned developed model isimplemented to further reduce simulation running time andcalculate motor temperature under normal running condition.

Current major roadmapping efforts have all clearly underlined that true industrial sustainability will require far higher levels of systems’ autonomy and adaptability. In accordance with these recommendations, the Evolvable Production Systems (EPS) has aimed at developing such technological solutions and support mechanisms. Since its inception in 2002 as a next generation of production systems, the concept is being further developed and tested to emerge as a production system paradigm. Characteristically, Evolvable systems have distributed control, and are composed of intelligent modules with embedded control. A concerted effort is being exerted through European research projects in collaboration with manufacturers, technology/equipment suppliers, and universities. After introducing EPS, this paper presents current developments and applications, with specific emphasis on principles and mechatronic applications.

When multiple control processes share a common wireless network, the communication protocol must provide reliable performance in order to yield stability of the overall system. In this paper, the novel cross-layer optimized control (CLOC) protocol is proposed for minimizing the worst case performance loss of multiple industrial control systems. CLOC is designed for a general wireless sensor and actuator network where both sensor to controller and controller to actuator connections are over a multihop mesh network. The design approach relies on a constrained max-min optimization problem, where the objective is to maximize the minimum resource redundancy of the network and the constraints are the stability of the closed-loop control systems and the schedulability of the communication resources. The optimal operation point of the protocol is automatically set in terms of the sampling rate, scheduling, and routing, and is achieved by solving a linear programming problem, which adapts to system requirements and link conditions. The protocol has been experimentally implemented and evaluated on a testbed with off-the-shelf wireless sensor nodes, and it has been compared with a traditional network design and a fixed-schedule approach. Experimental results show that CLOC indeed ensures control application stability and fulfills communication constraints while maximizing the worst case redundancy gain of the system performance.

Previous results concerning instability of the dc linkin inverter drives fed from a dc grid or via a rectifier are extended.It is shown that rectifier–inverter drives equipped with small (film)dc-link capacitors may need active stabilization. The impact oflimited bandwidth and switching frequency in the inverter–motorcurrent control loop is considered, and recommendations forselection of the dc-link capacitor, the switching frequency, andthe dc-link stabilization control law in relation to each other aregiven. This control law is incorporated in a field-weakening (toenhance voltage sag ride-through) current controller for whichdesign recommendations are presented.

An experimental analysis of the behavior under short-circuit conditions of three different siliconcarbide (SiC) 1200-V power devices is presented. It is found that all devices take up a substantial voltage, which is favorable for detection of short circuits. A transient thermal device simulation was performed to determine the temperature stress on the die during a short-circuit event, for the SiC MOSFET. It was found that, for reliability reasons, the short-circuit time should be limited to values well below Si IGBT tolerances. Guidelines toward a rugged design for short-circuit protection (SCP) are presented with an emphasis on improving the reliability and availability of the overall system. A SiC device driver with an integrated SCP is presented for each device-type, respectively, where a shortcircuit detection is added to a conventional driver design in a simple way. The SCP driver was experimentally evaluated with a detection time of 180 ns. For all devices, short-circuit times well below 1 µs were achieved.

In this paper, an improved phase-locked-loop-type speed and position estimator for permanent-magnet synchronous motor (PMSM) drives is considered. Particular attention is put on salient-rotor PMSMs with fast mechanical dynamics. A method is presented, whereby significantly improved tracking is achieved. While saliency makes nominal-speed stability more difficult to guarantee (an analysis of this is presented), a benefit is that signal-injection methods can be used at low speeds for accurate position estimation, which is also included in the modified estimator.

This paper considers speed and position estimation of salient permanent-magnet synchronous machines (PMSMs). An estimator of phase-locked loop (PLL) type is considered. Signal injection techniques are used in the zero-speed and low-speed regions, while information found in the back electromotive force (EMF) is used for higher speeds. Particular focus is put on the transition region, i.e., the speed region where the estimator switches between signal-injection and back-EMF-based methods. It is shown that the estimator may become unstable for certain setups of machine parameters and operating conditions if the transition region is determined incorrectly. To avoid this instability, design rules for how the transition region should be determined, as well as recommended selections for all parameters introduced, are given. The results of the analysis are also supported with experimental results.

This paper proposes control algorithms for a fault-tolerant permanent-magnet synchronous motor (PMSM) drive. In order to improve the reliability of the drive, an algorithm for achieving a sensorless control that operates properly also in fault mode is proposed. Furthermore, it is shown how a closed-loop field-weakening controller needs to be modified in order to operate properly in fault mode. Automotive applications are in mind and the algorithms presented are verified with experimental results using an in-wheel PMSM. With the proposed modifications, the reliability of the drive can be improved.

Code division multiple access (CDMA) network-on-chip (NoC) has been proposed for many-core systems due to its data transfer parallelism over communication channels. Consequently, coder-decoder (CODEC) module, which greatly impacts the performance of CDMA NoCs, attracted growing attention in recent years. In this paper, we propose a new parallel CODEC technique for CDMA NoCs. In general, by using a few simple logic circuits with small penalties in area and power, our new parallel (NPC) CODEC can execute the encoding/decoding process in parallel and thus reduce the data transfer latency. To reveal the benefits of our method for on-chip communication, we apply our NPC to CDMA NoCs and perform extensive experiments. From the results, we can find that our method outperforms existing parallel CODECs, such as Walsh-based parallel CODEC (WPC) and overloaded parallel CODEC (OPC). Specifically, it improves the critical point of communication latency (7.3% over WPC and 13.5% over OPC), reduces packet latency jitter by about 17.3% (against WPC) and 71.6% (against OPC), and improves energy efficiency by up to 41.2% (against WPC) and 59.2% (against OPC).

In power system operation, the economic dispatch problem (EDP) aims to minimize the total generation cost while meeting the demand and satisfying generator capacity limits. This paper proposes an algorithm based on the gradient push-sum method to solve the EDP in a distributed manner over communication networks potentially with time-varying topologies and communication delays. This paper shows that the proposed algorithm is guaranteed to solve the EDP if the time-varying directed communication network is uniformly jointly strongly connected. Moreover, the proposed algorithm is also able to handle arbitrarily large but bounded time-varying delays on communication links. Numerical simulations are used to illustrate and validate the proposed algorithm.

Radio-frequency identification (RFID) with a received signal strength indicator (RSSI) is a low-cost and low-complexity approach for item-level indoor localization. Although RSSI-based algorithms suffer from multipath effect and other environmental factors, reference tags and RSSI changes can be utilized to further improve the localization accuracy. However, the current algorithms lack deep analysis of the influence of tag interaction on localization accuracy and faces the challenge of simultaneously locating multiple close targets. In this paper, we propose an analysis method about how tag interaction affects a tag antenna radiation pattern and an RSSI change. The tag interaction analysis guides us to improve the design of RSSI-based localization algorithms. We take the k-nearest neighbor (k-NN) algorithm and the Simplex algorithm as two examples. The experimental results show that the revised k-NN and the revised Simplex algorithms are robust to different numbers, spacing, and materials of target objects, and they are superior to other RFID localization schemes, considering cost, capability of simultaneous localization of multiple targets, and location estimation errors.