Comprehensive Optimization of ZVS Variable Frequency Control for SiC/Si HANPC Converter

The growing demand for high-efficiency power converters with silicon carbide (SiC) devices at high switching frequencies has fueled an interest in non-auxiliary circuit-based soft switching techniques, particularly the variable switching frequency control for zero-voltage switching (VF-ZVS). Besides increasing the Total Harmonic Distortion (THD), applying the full ZVS range to three-phase SiC/Si Hybrid Active Neutral Point Clamped (HANPC) converters leads to a rise in conduction loss. This issue is exacerbated by the use of Si IGBT, as it generates significantly more conduction loss than SiC MOSFET in medium and small power HANPC. Consequently, a power loss optimized VF-ZVS (OVF-ZVS), based on a precise loss model, is proposed to enhance efficiency by considering the effect of the current ripple on device loss. This OVF-ZVS optimizes the switching frequency to minimize the total loss of three-phase switching devices across all load ranges. Meanwhile, the variable switching frequency range and LCL parameters are optimized to strike a balance between superior output current quality, power density, etc. Simulation and experimentation using a 10 kW HANPC converter prototype illustrate the effectiveness of the proposed comprehensive optimization, further highlighting the reduction in THD and device loss.