Comparative Analysis of Inductor Loss for High-Frequency DCM Grid-Tied Inverters with Modulations Strategies Achieving ZVS

This paper presents a comparative analysis of two different modulations achieving zero-voltage switching (ZVS) for discontinuous current mode (DCM) grid-tied inverters. The DCM inverter can achieve ZVS by discretely adjusting the duration of the zero current period, in which the voltage across the devices is oscillating. ZVS capability and current ripples with the conventional bipolar modulation and a proposed hybrid modulation that optimizes them are reviewed. This paper proposes an estimation method for both the core and winding losses of the inductors. The impact of the modulation strategies on the inductor losses are analyzed. It was confirmed that the peak-to-peak reduction in the inductor current by the proposed modulation can reduce both the core and winding losses; however, the oscillating current during the zero current period can generate non-negligible losses both in core and winding. The estimated inductor losses were experimentally verified with an inverter using GaN-HEMTs operating at 1 MHz.