A novel control strategy of resonant converter with modular rectifier based on SiC switching device

Abstract

The resonant converter with modular rectifier (RMR) is a promising topology for DC grid applications. This paper studies the control strategy of RMR based SiC switching device including the output voltage and submodule (SM) capacitor voltage balancing control strategy. Firstly, different working modes of the RMR converter are analyzed, and the Critical Mode with the highest efficiency is introduced. A control method is proposed to guarantee the RMR operating the Critical Mode. The control parameters design is detailed. Secondly, the charging and discharging principles of SM capacitor voltages are introduced, then a balancing method is proposed: the SM capacitor voltages are sorted, then assign gate signals with smaller pulse width to SMs with lower capacitor voltages, and vice versa. The proposed control methods are verified by experimental results on a 300 V/1200 V 8 kW RMR prototype based SiC switching device. According to the experimental results, the RMR operates at the Critical Mode under different load and gain conditions. The SM capacitor voltages are well balanced. The peak efficiency is 98.2%.

Keywords

• DC grid
• Resonant converter with modular rectifier
• Critical mode
• Voltage balancing
• SiC switching device