Low cost control and fast magnetizing-demagnetizing fault tolerant converter topologies for high performance SRM drives

Abstract

Electric vehicles are a good alternative for a clean and environmentally friendly urban transport system. The electrical drive is the core component of electric vehicles, and researchers are continuously making efforts to improve the drive’s performance while making it reliable, safe, and cost-effective.. Though many electric vehicle companies and researchers focus on permanent magnet motors for electric vehicles because of their high power density and compactness, the availability of rare earth magnets creates a problem in mass production and makes them more costly. Therefore, the Switched Reluctance Motor (SRM) attracted many researchers for electric vehicles applications. SRM is a special type of variable reluctance motor designed for rugged operation. Being magnet-free and lightweight, SRM can drive high torque, making it attractive in electric vehicle applications. SRM has a simple manufacturing process, making it cheaper than other motors. SRM is fault-tolerant, reliable, and has a high power density. The significant issue limiting the SRM is the high torque ripple and its associated effects on the motor. Its rugged construction and low cost motivate industries and researchers to contribute to the development of algorithms to tackle the torque ripple issues. This thesis proposes to tackle the torque ripple problem in two ways, one by proposing better control algorithms and two through converter topologies. A new control algorithm is implemented based on the Torque Sharing Function (TSF) to reduce the torque ripple. This control algorithm effectively reduces the torque ripple and also has less computation burden. Further, the thesis is focused on the converter topologies development, where two new converters are developed with a minimum number of switches. The developed converters have the fast demagnetizing ability, which help to reduce the torque ripple in SRM drives. One of the proposed converter topologies which also has fast magnetizing ability is extended to make a fault-tolerant converter in order to make the SRM drive more reliable. Lastly, sensorless control algorithm is developed, where accurate rotor positions are detected at standstill and running conditions with minimum computational overhead. The proposed control algorithms and converter topologies are tested in simulation using MATLAB/Simulink. The control algorithms and converter topologies are experimentally tested with the help of a hardware prototype that is made in the laboratory on a 4-phase 8/6 SRM using an FPGA digital controller.