A Numerical Method for Calculating the Output Spectrum of an H-Bridge Inverter with Dead-time Based on Switching Mode Analysis

The distortion of an H-bridge inverter originates from many nonlinear factors, of which the most dominant one is typically the dead-time. Different analytical and numerical methods have been proposed to calculate the distortion caused by the dead-time. However, all the existing methods are neglecting the effects of soft-switching and discontinuous conduction mode, resulting in a deviation with the practice. In this paper, the characteristics and the corresponding effects of each individual switching mode is analysed. Current constraint functions are proposed in order to determine the time position of different switching modes. A numerical method for calculating the output spectrum of the H-bridge inverter based on the switching mode analysis is introduced. The method has an improved accuracy compared to the previous analytical method especially when the inductor current ripple is high. The results are verified by simulation and an experimental prototype.