Variable boundary dual mode current modulation scheme for three-phase micro-inverter

A traditional half-bridge three-phase inverter topology can achieve zero voltage switching by implementing BCM operation which requires no additional power devices or magnetic components. In this paper a variable boundary dualmode current modulation method that combines ZVS and ZCS is proposed in order to improve the efficiency of the BCM current controlled micro-inverter. Decreasing output current moves the ZVS/ZCS boundary toward the peak of the line half cycle which reduces the switching losses at light loads. Increasing output current will move this boundary toward the line zero crossing which reduces conduction losses at heavier loads. The experimental results show that using the proposed current modulation scheme peak efficiency of 98.7% for a 400W three-phase micro-inverter can be achieved with no additional cost.