A comparison of soft and hard-switching losses in three phase micro-inverters

The efficiency of a PV grid-tie micro-inverter is of critical concern to its application. Three representative three-phase voltage source micro-inverter topologies have been selected to make loss comparisons: A Hard Switching Inverter (HSI), an Auxiliary Resonant Commutated Pole Inverter (ARCPI), and an Actively Clamped Resonant DC-link Inverter (ACRDCLI). Loss composition and estimation are given in detail for 350W micro-inverters. It is pointed out that the HSI has outstanding advantages in both efficiency and cost. The ARCPI losses are lower than the other two topologies. But the auxiliary circuits are costly and the controlling and driving circuits are complicated. The ACRDCLI has a simple structure but high DC-link losses. If an improved control scheme is used, the DC-link losses of the ACRDCLI can be reduced. This paper compares these advantages and limitations for assessing the selection of soft-switching topologies for micro-inverters.