Multifrequency Modeling and Stability Analysis of Multisampled Three-Phase Grid-Connected Converters

Digital control based on multisampling and multiupdating (MSMU) is a potential way to enhance the performance of grid-connected converters (GCCs). But the traditional model of MSMU pulse width modulation (PWM) can’t be used to predict high-frequency instability caused by perturbation sidebands. Multisampled GCCs’ high-frequency response is still unknown and needs to be further explored. In this study, as for three-phase multisampled GCCs, a multifrequency model of MSMU PWM is built and verified, which considers perturbation sideband harmonics. Then, the output admittance model of multisampled GCCs is derived and can accurately describe the high-frequency admittance characteristics. High-frequency stability and the factors related to the impact of sideband coupling on stability are analyzed in detail. Compared with traditional one, the proposed model has higher accuracy in high-frequency band, which can predict high-frequency stability accurately. Finally, experimental results verify the effectiveness of the theoretical analysis presented above.