Small-signal multi-frequency model for grid-connected inverter system with PWM effect

It is a well known fact that pulse width modulation (PWM) produces sideband effects. Taking this point into account, the accuracy of the grid-connected inverter model can be improved. In this paper, considering the aliasing effect of the PWM sideband components on the closed-loop control, a complete representation for the transfer function of the PWM is obtained. Furthermore, a multi-frequency model of grid-connected inverter system is derived. It is convenient for obtaining a PWM gain for grid-connected inverter system, which is PWM-controlled. In order to have an easy physical expression of the effects caused by the sideband components, an approximation is applied to simplify the PWM gain. The stability analysis is used to prove that PWM gain considering PWM effect is more precise than the conventional one. Experimental results verify the effectiveness of our proposal.