Research On Power Converter Design Optimization And Torque Ripple Suppression For Switched Reluctance Motors

Switched reluctance motor(SRM)has attracted widespread concerns from scholars and entrepreneurs both here and abroad due to a series of advantages,such as simple structure,low cost,high starting torque,and excellent fault-tolerance ability.With the increasing application of SRM drive system,the different optimization requirements are required in the various complicated applications such as electric vehicle drives.To further enhance the competitiveness of SRM system,power converters design optimization and torque ripple suppression are studied and analyzed deeply in this paper.For phase current detection in four-phase SRM drive,a novel phase current reconstruction scheme is proposed by one dc-link current sensor.Based on an improved asymmetric half bridge converter and high-frequency pulse injection,one current sensor is used to achieve the phase current detection with less electronic components and more compact structure,which can effectively reduce the system volume and cost,and improve the system reliability.For phase current detection in multiphase SRM drive,a universal cost-effective phase current reconstruction scheme is developed.Based on the proposed grouping principle of phase windings,for odd-numbered multiphase SRM(OMSRM)with m phases and even-numbered multiphase SRM(EMSRM)with n phases,the phase currents can be respectively detected by employing(m+1)/2 and n/2 multiplexed current sensors without converter change and high-frequency pulse injection.The proposed method can achieve the intact phase current detection,and be easy to implement with reduced system volume and cost.For fault-tolerance control in three-phase SRM drive,a novel fault-tolerance power converter is proposed based on full-bridge converter.Under normal condition,bidirectional current excitation is adopted.All the switching devices are actively involved,which can average the heat dissipation for the heat sink design and extended the life of switching devices.When a switch fault occurs,the fault type can be quickly determined by identifying the fault currents characteristics.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 by an inverter.For multiport converter design in SRM drive,a cascaded serial-parallel battery management system-based multilevel converter is developed.Multiple operation modes can be achieved,including the battery driving mode,generator driving mode,hybrid driving mode,running charging mode,and standstill charging mode.The flexible multilevel bus voltage can reduce the switching loss and improve the system torque capability,system efficiency,and reliability.With flexible discharging and charging functions,the state-of-charge balance can be dynamically achieved,which will enhance the system security.Moreover,the modular structure can enhance the fault-tolerance ability and be highly beneficial for the market mass production.For torque ripple suppression in SRM drive,a novel direct instantaneous torque control scheme is developed to suppress the torque ripple based on the online compensation of torque sharing function(TSF).The commutation region is divided into Region Ⅰ and Region Ⅱ in real time by a separation point.By the TSF compensation of the outgoing phase positively in Region I and the incoming phase negatively in Region Ⅱ,the torque ripple is effectively suppressed during the commutation region.Meanwhile,the combination of hard-and soft-chopping modes is adopted to accelerate the torque tracking during the commutation region and reduce the switching actions and switching loss during the one-phase conduction region for better motor performance.Finally,the simulation model and experimental setup are built up.The correctness and effectiveness of the proposed schemes are validated by the simulation and experimental results.