Current Ripple Prediction and DPWM Based Variable Switching Frequency Control for Full ZVS Range Two Parallel Interleaved Three-Phase Inverters

In this article, an improved variable switching frequency zero-voltage switching (ZVS) control strategy is proposed for two parallel interleaved three-phase inverters. Discontinuous pulsewidth modulation is adopted and full-range ZVS can be achieved at any load or modulation ratio. The critical switching frequency can be easily calculated in a digital controller based on current ripple prediction instead of current zero-crossing detection. No additional high-frequency sensor or auxiliary circuit is needed. Compared with the continuous pulsewidth modulation, the switching frequency variation range is narrower and the frequency calculation equation is simplified. In addition, lower peak current ripple leads to lower current stress. Owing to the high switching frequency and the low inductance, the size and the cost of the inverter can be significantly reduced. A 6.6-kW experimental prototype with SiC MOSFETs interfacing 400-V dc with three-phase 110-V ac grid is developed to verify the effectiveness of the proposed control strategy.