Multilevel Converter for Variable Speed Medium-Voltage Switched Reluctance Motor Drives

Electric drives have gained ground in multi-megawatt applications, where synchronous and induction motors are mainly used. Switched reluctance motors have potential in high power, high reliability applications. But so far no suitable converter has been proposed for this motor that possesses the scalability, reliability, and efficiency required at such high power and voltage levels. In this paper, a novel converter suitable for multi-megawatt medium-voltage switched reluctance motor drives is proposed and analyzed. The converter is easily scalable, thanks to the modular construction based on chopper cells with capacitors. The converter can easily accommodate redundant cells, which makes it highly reliable. High efficiency is achieved by virtue of multilevel operation and due to the use of low-voltage devices in the cells. Contributions in this work include the novel converter topology, and a comprehensive control algorithm that overcomes the challenges of balancing and controlling cell capacitor voltages. The converter's operation and control are studied through extensive simulation of a 2 MW switched reluctance motor drive system. The simulation results validate the proposed converter's concept, suggesting it is as a viable option for multi-megawatt medium-voltage motor drives. Simulations also show that the proposed converter has higher efficiency than the conventional 2-level asymmetric switched reluctance motor converter.