Generalized discontinuous PWM strategy for Z-source inverters with switch losses optimization

Abstract

The shoot-through state of the Z-source inverter generates large switching losses. However, the discontinuous modulation strategy can effectively reduce the switching losses of power devices. When the discontinuous modulation strategy is used in Z-source inverters, the switching sequences and the shoot-through states need to be arranged reasonably. This paper provides a method for comparing the switching losses of different modulation strategies by calculating the current that is passed through a switching device for a fundamental cycle. The calculations show that the Z-source inverter switching losses are determined by the number of switching actions in a switching period and by the method of insertion of the shoot-through state. Based on this, a generalized discontinuous modulation strategy for Z-source inverters is proposed. This modulation strategy achieves optimal switching losses when the power factor is less than 1. The method of redistributing the shoot-through states can be applied to other modulation strategies to achieve loss optimization. The effectiveness of the proposed modulation method is demonstrated by MATLAB/Simulink combined with PLECS simulation. Finally, and a low-power platform is built for experimental verification.