This paper presents a technical overview for low-noise switched reluctance motor (SRM) drives in electric vehicle (EV) applications. With ever-increasing concerns over environmental and cost issues associated with permanent magnet machines, there is a technical trend to utilize SRMs in some mass production markets. The SRM is gaining much interest for EVs due to its rare-earth-free characteristic and excellent performance. In spite of many advantages compared to conventional adjustable-speed drives, SRMs suffer from torque ripple and radial distortion (and thus noise and vibration) by their nature. Therefore, for high-performance vehicle applications, it is important and urgent to optimize the SRM system to overcome the drawbacks of the noise and vibration. In order to present clear solutions to the acoustic noise in SRMs, this paper starts by analyzing the mechanism of the radial vibration and torque ripples inherent in the motors, and then focuses on the state-of-the-art technologies to mitigate the radial force and torque ripples. It highlights two categories for low-noise SRMs, including the machine topology improvement and control strategy design for radial vibration mitigation and torque ripple reduction. Advanced technologies are reviewed, classified, and compared accordingly. In addition to these methodologies, the schemes that have been developed by authors are also presented and discussed. Finally, the research status on this topic is summarized and forecast research hotspots are presented. It is our intention that this paper provides the guidance on performance improvements for low-noise SRM drives in EV applications.

This paper proposes a modular multilevel converter (MMC)-based switched reluctance motor (SRM) drive with decentralized battery energy storage system (BESS) for hybrid electric vehicle (HEV) applications. In the proposed drive, a battery cell and a half-bridge converter is connected as a submodule (SM), and multiple SMs are connected together for the MMC. The modular full-bridge converter is employed to drive the motor. Flexible charging and discharging functions for each SM are obtained by controlling switches in SMs. Multiple working modes and functions are achieved. Compared to conventional and existing SRM drives, there are several advantages for the proposed topology. A lower dc bus voltage can be flexibly achieved by selecting SM operation states, which can dramatically reduce the voltage stress on the switches. Multilevel phase voltage is obtained to improve the torque capability. Battery state-of-charge (SOC) balance can be achieved by independently controlling each SM. Flexible fault-tolerance ability for battery cells is equipped. The battery can be flexibly charged in both running and standstill conditions. Furthermore, completely modular structure is achieved by using standard half-bridge modules, which is beneficial for market mass production. Experiments carried out on a three-phase 12/8 SRM confirm the effectiveness of the proposed SRM drive.

This paper proposes an optimized direct instantaneous torque control (DITC) scheme for switched reluctance motor (SRM) drives with a novel adaptive dynamic commutation strategy, which can effectively reduce torque ripple and improve system efficiency. To minimize torque ripple, two operational modes are developed for torque tracking during commutation regions. In Mode I, the torque error is compensated by the outgoing phase during the current buildup region of the incoming phase; in Mode II, the torque error is compensated by the incoming phase during the demagnetization region of the outgoing phase. To implement the proposed DITC scheme in a more effective conduction range, the commutation instants are dynamically adjusted according to the varied operation conditions. For each phase, the turn-on and turn-off angles are modified in each electrical cycle by a torque error regulator and a phase current endpoint detector, respectively. By employing the proposed strategy, the torque generation capability is fully utilized for minimized torque ripple, and the phase currents work within a more effective conduction range for improved system efficiency. The simulation and experiments on a three-phase 12/8 SRM are carried out to verify the feasibility and effectiveness.

This paper proposes an efficiency optimization method for the permanent magnet synchronous motor (PMSM) based powertrain by using field-circuit coupled finite-element method (FEM) for electric vehicle or hybrid electric vehicle applications. In this paper, an alterable flux-weakening (FW) angle is employed in the armature current control strategy for the FW operation. The optimal FW angle for each certain operating condition can be obtained through the pre-selection, which improves the system efficiency compared to conventional FW methods. Then, the lookup table (LUT) for optimal armature current control commands is obtained. Through using this optimal LUT in the drive system, the system efficiency can be significantly improved for the entire operation range. The time-stepping FEM is used to simulate the PMSM system, which integrates the electromagnetic field analysis of the motor prototype and the control algorithm of the drive system. A 2-D transient FEM model is built for a 15 kW PMSM in ANSYS Maxwell, and a vector control circuit model is set up in ANSYS Simplorer. Experiments are carried out on the 15 kW PMSM prototype to verify the accuracy of the simulation results and the effectiveness of the proposed design method.

Hybrid electric bus (HEB) presents an emerging solution to exhaust gas emissions in urban transport. This paper proposes a multiport bidirectional switched reluctance motor (SRM) drive for solar-assisted HEB (SHEB) powertrain, which not only improves the motoring performance, but also achieves flexible charging functions. To extend the driving miles and achieve self-charging ability, photovoltaic (PV) panels are installed on the bus to decrease the reliance on fuels/batteries and charging stations. A bidirectional front-end circuit with a PV-fed circuit is designed to integrate electrical components into one converter. Six driving and five charging modes are achieved. The dc voltage is boosted by the battery in generator control unit (GCU) driving mode and by the charge capacitor in battery driving mode, where the torque capability is improved. Usually, an extra dc-dc converter is needed to achieve battery charging. In this paper, the battery can be directly charged by the demagnetization current in GCU or PV driving mode, and can be quickly charged by the PV panels and GCU/AC grids at SHEB standstill condition, by utilizing the traction motor windings and converter circuit, without external charging converters. Experiments on a three-phase 12/8 SRM confirm the effectiveness of the proposed drive and control scheme.

In this paper, a novel modular full-bridge converter is proposed for three-phase switched reluctance motors (SRMs) by using six-pack switch modules, which provides an advanced fault-tolerance solution for both the open- and short-circuit faults in switching devices. The proposed converter is composed of two standard six-pack switch modules, providing great benefits for industrial massive production due to the modular topology. Under normal conditions, bidirectional current excitation is developed in the proposed converter, where all the switching devices are actively involved, which makes full use of the switches and averages the heat dissipation for the heat sink design. When a switch fault occurs, the fault signature can be extracted by detecting the characteristics of phase currents and operation modes, and effective fault-tolerance strategies are further applied to achieve the fault tolerance operation accordingly. Under switch open-circuit faults, the faulty phase is adjusted to unidirectional current excitation without degrading the motor performance. Under switch short-circuit faults, the motor can still work steadily with a single six-switch inverter module by easily reconstructing the proposed converter, without losing any phase windings. The simulation and experiments on a three-phase 12/8 SRM are carried out to validate the feasibility of the proposed converter and control techniques.