Hybrid Pulse Width Modulation for Optimizing Key Index Parameters in Multi-Level Traction Inverters

Electric vehicles are a major trend for many automotive manufacturers to fulfill more restricted legal requirements in the future. Improvement of key index parameters (KPIs) of electric drive unit (EDU) is essential to deliver better vehicles to the customers and compete with other car manufacturers. The most critical components in the EDU are the inverter and the electric machine (EM), which should be optimized to provide the requested KPIs, such as efficiency and total harmonic distortion (THD) levels. Multi-level inverters, as opposed to two-level inverters, improve these KPIs. Furthermore, using suitable modulation methodologies such as space vector pulse width modulation (SVPWM) and discontinuous pulse width modulation (DPWM) improves these KPIs in the EDU's operating torque-speed map. In this study, we have investigated the use of different types of modulation methods in T-Type multi-level inverters to optimize above KPI’s in the vehicle operation. The results show that different modulation methods result in better KPI’s in the different torque-speed ranges, and therefore the combination of these different methods (the hybrid method) ensures mutual optimization of the KPIs mutually in the EDU operating torque speed map. The method of combination and optimized results are demonstrated in this study.