Improving the Efficiency of Traction Systems through Inverter Voltage Waveform Optimization

In recent railway traction systems, squirrel-cage induction motors are commonly used as traction motors. They are usually driven by a voltage source inverter with a single-pulse waveform at high speed. The single-pulse waveform contains lower harmonics that induce additional loss in the motors. Therefore, this paper studies the optimization of three-pulse and five-pulse waveforms which could replace single-pulse waveforms to reduce additional loss. This paper proposes three-pulse and five-pulse waveforms that are optimized to minimize additional loss while maximizing fundamental components. The effectiveness of the proposed waveforms was verified through finite element analyses. The results showed that the proposed waveforms are able to improve motor efficiency by about one percent compared with single-pulse waveforms.