This paper proposes a new asymmetric neutral point diode clamped multi-level (NPC) converter for a four-phase switched reluctance motor drive. The inbuilt NPC clamping capacitors are used for both voltage level clamping and also as dc rail voltage-boosting capacitors to increase the output power of the motor, particularly for high speed electric vehicle applications. The new converter allows regenerative energy to be recovered back to the dc supply for rapid machine braking, thus increasing overall drive efficiency. Analysis of the different modes of converter operation, along with design equations for sizing the voltage-boosting capacitors, are detailed. The effect of capacitance on boost voltage and increased motor base speed is presented. Simulation and experimental results confirm the effectiveness of the proposed converter.

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters.

Active front-end boost rectifiers can replace the uncontrolled diode bridge rectifiers for ac-dc conversion offering high power quality with near unity power factor. The four-switch, B4, topology is gaining interest, either as an inverter or a rectifier, where each switch should withstand the full dc link voltage. Higher voltage-rated power semiconductor devices not only imply slower response with lower overall efficiency but also higher cost and size. Thus, multilevel inverters become a viable solution. This paper investigates a two-leg neutral-point diode-clamped B8 rectifier allowing the series connection of fast, efficient, and low voltage rating switches. The proposed rectifier has better performance and efficiency than the B4 rectifier. Only two inductors instead of three are required. Model predictive current control (MPCC) is developed for accurate current tracking. A model of the proposed rectifier is detailed for the implementation of MPCC. The concept is validated by simulation and experimentation.

This paper investigates the effect of rotor flux screens (conducting screens) on the performance of switched reluctance motors with a higher number of rotor poles than stator poles. A high number of rotor poles decreases the torque ripple, which is desirable for electric vehicle applications. The conducting screens fill the rotor interpolar gaps forming a cylindrical rotor hence alleviating the windage losses, especially effective at high speeds. The effect of conducting screen thickness and material electrical conductivity on current rise time, developed torque, and output power is studied. A procedure for calculating the effective value of unaligned inductance for screened motors using the flux tube method is presented. Finite element analysis results for different screen cases confirm the effectiveness of conducting screens in improving the torque, hence power capability, of switched reluctance motors. Received: 11 January 2023 Accepted: 03 May 2023 Published: 30 May 2023