An Adaptive DPWM Based on Variable Switching Frequency for Full Range Soft Switching under Any Power Factor in Three-Phase Two-Level Parallel Interleaved Inverters
Chen Jianliang, Zhang Yixiang, Ma En, Xin Zhen
State Key Laboratory of Intelligent Power Distribution Equipment and System Hebei University of Technology Tianjin 300401 China
Abstract：This paper proposes an adaptive discontinuous pulse width modulation (DPWM) strategy to achieve full-range soft-switching for switching devices under arbitrary power factors. It addresses the issue of high switching losses in two-level three-phase parallel interleaved inverters during high-frequency operation. The control strategy features modulation-changing angles and dynamically adjusted switching frequencies. Continuous switching frequency is ensured to enhance operational stability through optimized selection. The modulation-changing angle and the critical switching frequency enabling zero voltage switching (ZVS) can be easily calculated through online computation, without additional high-frequency current sensors. The adaptive DPWM soft-switching strategy addresses the discontinuity in the critical switching frequency curves of the fixed DPWM soft-switching strategy, which arises from the fixed modulation-changing angles of the modulating waveform. The strategy results in higher switching frequency and lower conduction loss. First, the principle of ZVS without an auxiliary circuit for three-phase parallel interleaved inverters is proposed. The critical switching frequency curves of CPWM1 and CPWM2 are drawn. The two crucial switching frequency curves of CPWM1 and CPWM2 always intersect in each sector, and the intersection can be regarded as the modulation-change angle. Subsequently, a full ZVS range strategy is proposed in a three-phase two-level parallel interleaved inverter based on adaptive DPWM modulation. The method achieves ZVS by selecting the appropriate modulation-changing angles and switching frequency under various operating conditions. The switching frequency variation range is further reduced from more than 200 kHz to less than 100 kHz. The modulation-changing angles are mainly affected by the power factor. In sector I, the modulation-changing angles are 30° for the unity power factor and pure reactive power loads. The angle decreases from 60° to 30° as the power factor decreases under inductive loads and increases from 0° to 30° as the power factor decreases under capacitive loads. The turn-on loss is eliminated, and the condition loss is significantly reduced. A 20 kV·A photovoltaic inverter with SiC MOSFET interfacing DC 700 V with a three-phase AC 220 V grid is developed. Compared with the fixed DPWM soft-switching, the conduction loss is reduced by 43%. The peak efficiency of the adaptive DPWM soft-switching strategy is 99.3%. The inverter can select appropriate modulation-changing angles and switching frequency under various operating conditions. This approach improves switching frequency and reduces conduction loss. The adaptive DPWM soft-switching strategy has the following advantages. (1) Based on the current ripple pulsation prediction, this strategy reduces the cost of soft switching in inverters, without adding high-frequency current sensors. (2) Compared to the fixed DPWM soft-switching, the modulation-changing angles of the adaptive DPWM are not fixed, and the maximum switching frequency curve can be kept continuous. Thus, the switching frequency is high, the conduction loss is low, and the efficiency is high. (3) This strategy can realize four-quadrant full-range soft-switching with reactive power compensation, which can be used in diverse operational scenarios.
陈建良, 张益翔, 马恩, 辛振. 基于自适应DPWM的三相交错并联逆变器任意功率因数全范围变频软开关策略[J]. 电工技术学报, 2026, 41(8): 2672-2685.
Chen Jianliang, Zhang Yixiang, Ma En, Xin Zhen. An Adaptive DPWM Based on Variable Switching Frequency for Full Range Soft Switching under Any Power Factor in Three-Phase Two-Level Parallel Interleaved Inverters. Transactions of China Electrotechnical Society, 2026, 41(8): 2672-2685.
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2026, Vol. 41 
