DC-link current harmonics and common mode voltage (CMV) are key design challenges for inverter-based power electronic systems. Addressing them collectively without additional hardware and/or complexity has promising advantages. This article investigates the interleaved utilization of modified space vector PWM schemes for parallel-inverter systems, targeting a combined and simultaneous reduction of these quality concerns. A time-domain analytical dc-link current formulation and a new application of sequence-based interleaving are combined in an offline numerical optimization algorithm that locates optimal interleaving shifts synced with the PWM sequence. With simulation and experimental validation, the corresponding numerical results ascertain an effective suppression of dc-link current harmonics alongside CMV reduction. In addition, this article extends the proposed idea to a special application for 3x multiphase machines through experimental validation.

This article proposes a simplified discrete space vector modulation (DSVM)-based model predictive direct speed control (MPDSC) with an improved load disturbance observer for permanent magnet synchronous motor (PMSM) drives. First, a simplified DSVM method is used to improve the steady-state performance of MPDSC. In this DSVM method, a novel geometric method relying only on three auxiliary lines in each sector is designed to simplify the algorithm’s complexity. In this way, the set of candidate vectors is quickly determined. Then, the current pulsation and speed of MPDSC are suppressed, and the computational burden of the DSVM execution process is reduced. Second, the reasons that affect the dynamic performance of the conventional linear extended state observer (ESO)-based mechanical disturbance observer are analyzed, and the observed error of the observer is derived. Based on the observer error, an improved mechanical disturbance observer is proposed to accelerate the convergence process. The Lyapunov theory proves the stability of the proposed observer. Finally, the feasibility of the proposed method is verified by experiments.

A multiphase induction machine model using vector space decomposition provides insights into many space harmonics through decoupled reference frames. In order to utilize this potential of the multiphase machine, the parameters of each vector space must be identified. These parameters are usually identified using standard no-load and locked rotor tests of each torque-producing vector space. However, these tests do not provide a method for identifying stator leakage inductances, which have comparable magnitudes to the magnetizing inductances for higher-order vector spaces. Thus, the magnetizing current cannot be neglected during the locked-rotor test. This paper proposes an accurate method for identifying the T-model parameters of a multiphase induction machine, which can be conveniently translated into the model of choice. The proposed method use harmonic relations to segregate the stator leakage inductance from the total stator inductance, enabling accurate locked-rotor and partial-load tests for the measurement of rotor side parameters. Lastly, a 9-phase induction machine is used for the evaluation of the proposed parameter measurement method. These measured parameters are used for the field-oriented control of each torque-producing vector space, whose performances are analyzed by quantifying the measured output torque error and linearity.

A multiphase induction machine (MPIM) modeled using vector space decomposition (VSD) provides insight intospace harmonics which are segregated into vector spaces. Depending  on the winding configuration of the MPIM, some vectorspaces can produce torque in addition to the fundamental vectorspace, and they can be represented by a standard equivalentcircuit (EC) of an induction machine (IM). This paper evaluates multiple EC parameters identification methods (IDMs) and proposes a robust IDM routine for their accurate estimation. Furthermore, the proposed IDM routine shows reduced sensi-tivity to errors in known parameters compared to the standardIDMs, which is validated with the help of a detailed simulationmodel of a 9-phase IM.

The active short-circuit is a standard safety measure for permanent-magnet synchronous machine drives in electric vehicles, but it can lead to harmful torque and current transients. This paper introduces a mathematical and graphical method to determine the safe operating area of pre-fault current conditions, complying with user-defined torque bounds and preventing magnet demagnetization during short-circuit transients. The method incorporates an inductance-based motor model considering magnetic saturation, which is used to outline a strategy for transitioning to safe initial conditions in the minimum time for the available voltage. Experiments on a 35 kW permanent-magnet synchronous machine support the efficacy of the proposed strategy, offering promise for its use in automotive propulsion where compliance to safety standards such as the ISO 26262 is paramount.

This paper proposes the field separation theory for predicting the magnetic field of a quasi-Halbach array permanent-magnet motor considering the magnetization pattern and iron saturation. According to the proposed method, the air-gap field consists of a permanent-magnet field, winding current field, and equivalent saturation field. The equivalent permanent-magnet currents replacing the Halbach array with radial or parallel magnetization are introduced to obtain the linear analytical air-gap field of the permanent magnets. The winding current field relating to the slot shape and air-gap length can be directly determined using the linear analytical model. The equivalent saturation field is derived from the combination of the linear analytical model in the air gap and the magnetic circuit model in the iron region. The finite-element analysis of an 8-pole/9-slot Halbach array permanent-magnet motor and its prototype experiments are carried out to verify the effectiveness of the field separation theory, which is then used to analyze the harmonic magnetic field of Halbach array permanent-magnet motors to further improve the electromagnetic torque estimation. 

Magnet-free variable phase-pole machines are competitive alternatives in electric vehicles where torque-speed operating region, reliability, cost, and energy efficiency are key metrics. However, their modeling and control have so far relied on existing fixed-phase and pole-symmetrical models, limiting their drive capabilities especially when switching the number of poles on the fly. This paper establishes the harmonic plane decomposition theory as a space-discrete Fourier transformation interpretation of the Clarke transformation, decomposing all pole-pair fields into a fixed number of orthogonal subspaces with invariant parameters. The model remains unaltered for all phase-pole configurations, guaranteeing continuity even under phase-pole transitions. Relations of the state and input space vectors, and model parameters to those of the vector space decomposition theory used for multiphase machines are established via the use of the complex winding factor. Experiments confirm the modeling theory and demonstrate its practical usefulness by performing a field-oriented-controlled phase-pole transition. Non-trivial configurations with more than one slot/pole/phase and a fractional phase number are also demonstrated.

This paper proposes an equivalent resistance model of the permanent-magnet (PM) motor which is useful for predicting the losses. The PM loss and iron loss are replaced by the eddy-current loss and hysteresis loss in the equivalent resistance model, where the characteristics of these losses are extracted from the analytical model. The harmonic current and the current control angle are investigated in the paper to guarantee the accuracy of the loss prediction. The parameters in the equivalent resistance model can be easily obtained from the finite-element model and experiment. The proposed model demonstrates significant potential to improve motor efficiency.

A multiphase induction machine model using vector space decomposition provides insights into many space harmonics through decoupled reference frames. These decoupled reference frames host specific space vectors related to particular space harmonics. Based on the physical winding configuration, these vector spaces can be excited independently and simultaneously for the production of torque. However, this approach may result in beat oscillations due to interference between excited vector spaces if proper synchronization of vector spaces is not maintained. This paper describes this phenomenon through experimental tests. Furthermore, a solution eliminating the beat oscillations is proposed while optimizing the stator current or rotor flux linkage peaks. The effectiveness of the solution is experimentally verified on a 9-phase  induction machine. 

Active short-circuit is a standard emergency procedure applied to three-phase permanent-magnet synchronous machine drives in battery-electric and hybrid electric drivetrains to comply with stringent automotive safety standards, such as the ISO 26262. Unfortunately, the ensuing torque and current transients can harm the passengers and the driveline itself. This paper develops and validates a mathematical and graphical method to determine the safe operating area of pre-fault current conditions to guarantee that the torque remains within user-defined acceptable bounds and that the permanent magnets do not demagnetize during the short-circuit transient. The new method utilizes an inductance-based dynamic model of the motor, including magnetic saturation. The proposed methodology promises to be useful in the design, initial testing, and commissioning of permanent-magnet synchronous machines used for the propulsion of automobiles.