PWM-PFM hybrid modulation for DAB converter based on RL algorithm

This paper proposes a hybrid modulation method to control a dual active bridge(DAB) converter. To improve the efficiency of the system, the proposed hybrid modulation is consisted with pulse width modulation(PWM) and pulse frequency modulation(PFM) in addition to single phase shift(SPS) control which is widely used in DAB converter. By adopting the proposed method, the RMS current of the switching device can be reduced while keeping ZVS operation capability. Therefore, the system can accomplish the high efficiency. Also, this method can be used to a wide output voltage range and light load which is traditionally referred to as a drawback of the DAB converter. To realize optimized control variables for hybrid modulation, reinforcement learning(RL) method is adopted.To verify the effectiveness of the proposed method, a 2 kW DAB converter is built and tested. The efficiency results shows that the efficiency is increased in 1.05% at full load.