Variable Switching Frequency Strategy based on Circulating Current Analysis in Paralleled Inverters with Interleaved PWM

A time-domain model describing the circulating current of coupled inductors in paralleled inverters within a switching period is presented in this paper. Using this model, the circulating current can be predicted with interleaved PWM. To better utilize the coupled inductor's saturation limit which is determined by circulating current peak value, variable switching frequency PWM (VSFPWM) is proposed here. With the VSFPWM, both the electromagnetic interference (EMI) and switching losses of the paralleled inverters are well improved, and simultaneously the circulating current peak value is controlled within the limit. Detailed simulation and experimental results are provided to validate the proposed method.