Multilevel converters (MCs) are popular due to their higher voltage levels, low dv/dt, low harmonics, and high-power handling capabilities. This paper evaluates the use of two pulse width modulation (PWM) schemes for MCs: Phase-Shifted PWM (PS-PWM) and Level-Shifted PWM (LS-PWM). At first, the Cascaded H-Bridge (CHB) converter is utilized to demonstrate the principles and switching patterns of PS-PWM and LS-PWM. Thereafter, a 23 level CHB converter is designed for a permanent magnet synchronous machine (PMSM) drive application as a case study. The switching and conduction losses in different switches and submodules are analyzed in details under different PMSM operation points. The total harmonic distortion (THD) and efficiency of the converter are also compared. The simulation results show that PS-PWM performs better owing to reduced THD in the voltage and current as well as equal loss distribution, compared to LS-PWM. However, PS-PWM contributes to higher switching losses.

This paper presents an unscented Kalman filter (UKF) based method to estimate the severity level of stator interturn short circuit fault in permanent magnet synchronous machines (PMSMs). A mathematical model is firstly built for PMSMs to represent the machine dynamic with inter-turn faults (ISF). The voltage imbalance, inherent asymmetry, and ISF effects are all differentiated analytically by the model. To quantify the fault severity in the presence of unmeasurable fault parameters, the UKF is employed to estimate the nonlinear fault-related quantities in PMSMs, such as the short circuit current, the percentage of shorted turns, and fault loop resistance. The effectiveness and reliability of the proposed method have been validated by extensive simulations.

The traditional higher order sliding mode observer (HSMO) based sensorless control strategy uses a constant gain. However, very large gain value can decrease the output accuracy, while very small gain value will degrade the sliding mode observer’s stability. Therefore, under uncertain disturbances, an adaptive gain should be set for the higher order sliding mode observer. This paper proposes a variable universe fuzzy adaptive high order sliding mode observer based sensorless control (VUF-HSMO) strategy for permanent magnet synchronous machines (PMSMs) to achieve high precision sensorless control. Firstly, fuzzy logic control technique is used to get an adaptive gain in the HSMO. Then, variable universe theory is employed to self-tune the universe of discourse according to the change of inputs, and this results in the improvement in position estimation accuracy. Experiment results under different conditions demonstrate the effectiveness and the superiority of the proposed VUF-HSMO based sensorless control compared with the traditional HSMO and fuzzy logic based HSMO.

This paper presents an implementation of wide bandgap devices in soft-switching inverter architectures to fully exploit the benefits of high switching frequencies and fast switching transients without the adverse effects of motor insulation degradation and elevated levels of electromagnetic interference. Circuit simulation tools and analytical loss models are utilized to validate the advantages of the auxiliary resonant commutated pole soft-switching converter architecture against the implementation of wide bandgap devices in a conventional two-level hard-switching inverter where techniques are employed to control the dV/dt of the semiconductor devices. In addition, it is found that high-frequency operation is possible without the penalty in efficiency since switching losses are minimized in soft-switching inverter topologies. This characteristic leads to increased inverter efficiency and reduced harmonic losses in the motor which makes the architecture attractive for future electric vehicle traction applications.

Wide-band gap (WBG) power devices are gaining significant interest over conventional Si insulated gate bipolar transistor (IGBT) power devices for inverters in electric vehicle (EV) propulsion applications. Understanding motor-drive performance on a drive-cycle due to the influence of such emerging inverters is essential to design an optimal electric powertrain system which is superior in terms of cost, weight and efficiency when compared to the state-of-the-art. Specifically, this paper introduces a novel, hybrid approach that includes numerical and analytical simulations and analysis to consider drive-cycle load and switching characteristics of various power switches and harmonics generated by the inverter. A comprehensive list of performance indices including inverter and motor losses, current harmonics and torque ripple are initially selected and used in this approach. The impact of two-level IGBT, GaN, and SiC inverters on a surface permanent magnet machine are determined for a drive-cycle.

Wide band-gap (WBG) devices operating at higher switching frequencies have become attractive for EV traction inverter application in the recent years as they can be used to reduce harmonic distortion and switching loss. On the other hand, 800 V EV battery drivetrain systems have been recently deployed in commercially available in premium electric vehicles in order to achieve higher power for propulsion and faster charging. Given this scenario, this paper puts an effort to investigate and compare a 2-level inverter, a 3-level hybrid inverter and a nine-switch inverter for such an application. Motivation for investigating each of the inverter types is provided in the respective sections. This paper utilizes a novel hybrid modelling approach to get deeper insights into the power loss of inverter with device non-linearity and the harmonics, torque ripple and magnetic saturation in the motor due to different inverter types and their outputs. Cosimulation has been performed on each of the inverter types driving the same 100 kW surface-mounted permanent magnet motor on a WLTC drive cycle and results are discussed.

The equivalent circuit parameters of an interior permanent magnet synchronous machine (PMSM) vary under different operating conditions due to magnetic saturation and temperature rise. Knowledge of accurate machine parameters is of paramount importance for high performance PMSM control and condition monitoring. Therefore, this paper presents a novel parameter estimation method, which employs both the electrical and mechanical model of an interior PMSM (IPMSM) for simultaneously estimating three parameters; namely, the d- and q-axis inductances and permanent magnet flux linkage. Specifically, the proposed parameter estimation approach is mathematically justified at first. Thereafter, by using the machine mechanical model with the speed measurement, a third equation in addition to the dq-axis voltage equations is developed to make the estimation model full-rank for simultaneously estimating three parameters. Lastly, the proposed approach is implemented with the recursive least square algorithm to estimate machine parameters and it is validated with simulations and experimental tests on a laboratory IPMSM drive system.

Integrated charging (IC) technology in electric vehicles (EVs) employing conventional power electronics and motor drivetrain components facilitates level 3 fast charging capabilities with reduction in overall weight and cost of the vehicle. However, when the winding inductances of 3-phase interior permanent magnet synchronous machines (IPMSMs) are realized as line inductors for battery charging, due to machine saliency, the magnetic fields produced by the sinusoidal AC supply results in 1) asymmetrical voltages in the air-gap as a function of rotor position and 2) relatively high magnitudes of oscillating torques causing harmful noise and vibrations. This can lead to significant AC losses with risk of permanent magnet demagnetization in the machine. Since the same motor is employed for traction application as well, it is of significance to optimally design the machine for IC operation. Thus, this paper exclusively investigates three IPMSM rotor configurations to be employed for IC operation in EV. This paper firstly presents a conventional dq-axis circuit model based damper design approach implemented for mitigating the saliency effect during IC. Then, a comparative performance analysis of the rotor configurations with damper bars during IC operation on machine saliency; asymmetrical voltage waveforms; oscillating electromagnetic torque; permanent magnet operating point and magnet losses is performed using finite-element analysis (FEA). Results obtained are analyzed and discussed.