A Dual-Input Mismatch Power Processing LLC Converter for Microinverter Application

This article proposes a dual-input mismatch power processing LLC converter for microinverter application. The proposed converter has two photovoltaic (PV) input interfaces in series, so that when the power of the two PV panels is mismatched, the LLC converter is still in good working conditions. The dual control of pulsewidth modulation and pulse frequency modulation achieves independent power flow control of two input ports to eliminate the impact of mismatched power. In addition, through the structure of flying capacitor, the voltage stress of all primary switches is reduced. This article also proposes a control strategy for active voltage balancing of flying capacitors to balance the voltage stress of all primary switches. All switches in the converter operate under zero voltage switching conditions, and all diodes operate under zero current switching conditions. Besides, the switches on the main power circuit have a fixed 0.5 duty cycle, which gives it a lower current stress under any working condition. Finally, a 500 W laboratory prototype was constructed for experiments to verify the effectiveness of the theory.