Performance Comparison Study of Space-Vector and Modified-Carrier-Based PWM Techniques for a Three-Level Neutral-Point-Clamped Traction Inverter Drive

A performance comparison study between lower switching loss-based space-vector pulsewidth modulation (PWM) strategy for a three-level neutral-point-clamped inverter and a proposed modified-carrier-based PWM strategy is carried out for an electric vehicle propulsion application. The proposed carrier-based strategy uses single carrier and reduces the switching losses compared with the conventional carrier-based strategies by eliminating the common modulation interval between the upper and lower modulating signals. The inverter switching and conduction losses, total inverter loss, and voltage and current harmonic distortions are also compared with both the control strategies. PLECS is used to simulate the inverter losses with a 54-kW surface permanent magnet synchronous machine (SPMSM). Detailed simulation and experimental performances with the proposed carrier-based strategy and the dc-link voltage balancing during the change in speed and torque variations are carried out on a scaled-down prototype of 6-kW SPMSM. Dspace is used for hardware verification. Results show that, with the proposed carrier-based strategy, the dc-link capacitors are balanced even during the change in speed and torque.