Variable Dual Phase-Shift DPWM of ZVS Paralleled Inverters With Optimal Current Stress for AC Motor Drive

Zero voltage switching (ZVS) control is an effective approach for paralleled inverters with coupled inductors in ac motor drives, as it enhances switching frequency, efficiency, and overall control performance. However, conventional ZVS paralleled inverters only utilize the freedom of zero-sequence injection to adjust switching frequency which faces critical frequency conflicts for different phases, resulting in high current stress and suboptimal power capacity utilization. To address this issue, the freedom of phase-shift operation for paralleled phase-legs is implemented in this paper, and a variable dual phase-shift (VDPS) method under the discontinuous pulse width modulation (DPWM) is proposed for ZVS paralleled inverters. In the proposed VDPS-DPWM method, the circulating current ripple prediction model is proposed with the real time phase-shift angle, allowing the reconstruction of phase-leg current trajectories through the superposition of sampled fundamental current and predicted circulating current ripple. Additionally, an optimized VDPS angle is derived to mitigate critical frequency conflicts. The proposed VDPS-DPWM method demonstrates improved ZVS control and significant current stress optimization across the entire operational range. Simulation and experimental results are provided to validate the effectiveness of the proposed method.