Improved Three-Phase Critical-Mode-Based Soft-Switching Modulation Technique with Low Leakage Current for PV Inverter Application

In this paper, an improved three-phase criticalconduction-mode (CRM)-based soft-switching modulation technique is proposed in order to reduce the leakage current for photovoltaic (PV) inverter applications. Soft-switching turn-on is achievable, which is especially beneficial for silicon carbide (SiC)based systems at high switching frequency operation to achieve both high power density and high efficiency. The proposed modulation technique is digitally implemented with one low-cost microcontroller (MCU). The modulation concept is verified in simulations and also experimentally implemented on a SiC-based three-phase bidirectional ac-dc converter prototype. Softswitching turn-on during CRM and DCM operations is verified. In addition, the experiment results show that at least 89% reduction in the leakage current is achieved with the improved modulation technique.