Optimal variable switching frequency scheme to reduce combined switching loss and inductor core loss of single phase grid connected inverter

Abstract

Reducing the power loss of a converter without increasing volume or cost in hardware has always been a much sought-after, but challenging goal. This paper discusses a scheme to improve the system overall efficiency while still meeting a given THD requirement by implementing variable instantaneous switching frequency method without any hardware changes. This paper aims at minimizing the combined switching loss and inductor core loss by including different characteristics of the two types of losses relative to the instantaneous switching frequency in the optimization process. A 1kW H-bridge inverter using SiC MOSFETs and powdered iron core has been built to validate the theoretical analysis. Both constant switching frequency scheme (20 kHz) and optimal variable frequency scheme with simple code modification have been implemented in the experimental prototype using DSP TMS320f28335. The optimal variable switching frequency scheme shows a significant saving of 27.6% on the combined switching loss and inductor core loss compared with constant switching frequency scheme.