An improved on-time control method to reduce the line-current distortion for BCM/DCM mixed micro-inverter at light load condition

Micro-inverters convert direct current (DC) from a single solar panel to alternating current (AC). Peak current control is a simple way to regulate the output current of the micro-inverter. In this way, the shape of the current reference will determine the total harmonics distortion (THD) of the output line current. However, several factors like valley switching turn-on delay and equivalent capacitor effect are difficult to be taken into consideration in the current reference and are all ignored in previous papers. As a result, it makes the THD performance high, especially at light load condition. In this paper, an improved on-time method is proposed to replace the peak current control. In order to reduce the THD, the effect of valley switching, the equivalent capacitance and the leakage inductance is analyzed and compensated in the on-time calculation. Simulation and experimental results have validated the proposed control method.