Subfundamental Cycle Switching Frequency Variation for Switching Losses Reduction of a Two-Level Inverter Traction Drive

This paper proposes a method to vary the switching frequency within a fundamental cycle to reduce the switching losses of a two-level inverter while maintaining the peak-peak current ripple within a predefined limit. Unlike conventional strategies, the proposed technique utilizes precomputed switching frequency variation factors without relying on prediction or optimization techniques, since the peak-peak current ripple follows a definite trajectory within a fundamental cycle. Moreover, the variation in switching frequency is further controlled based on the operating carrier ratio and modulation index. The proposed strategy has been validated through both the simulation and experimental results on a permanent magnet synchronous motor drive for the space vector and discontinuous pulsewidth modulation patterns, and the results demonstrate that it reduces the two-level inverter switching losses up to 15%.