考虑数字控制和PWM效应的三相并网变换器多频小信号建模

The traditional averaging modeling methods applied for digitally controlled power converters are insufficiently accurate in the s-domain due to the neglect of the broadband frequency coupling effect introduced by the digital control and pulsewidth modulation (PWM) effect. In this article, an s-domain multifrequency small-signal model of a digitally controlled three-phase grid-tied voltage source converters is developed, which comprehensively considers the effect of digital control and PWM. As a result, crucial system dynamics in the digital control framework can be effectively incorporated into the system model, ensuring the accuracy of the model above the Nyquist frequency. Based on the established model, the high-frequency stability can be accurately predicted, while the traditional averaged model and other improved models present limitations. Furthermore, the model and stability differences resulting from different discretization methods (Tustin transform, backward Euler) are revealed. Simulation and experimental results verify the correctness of the theoretical analysis in terms of impedance measurement and stability analysis.