A New Perspective of Dual-Frequency Power Oscillation in Multi-VSGs Parallel Supercharger System

The multivirtual synchronous generators (VSGs) parallel supercharger is an important way to achieve the fast charging of electric vehicles (EVs) and the fast support of the power grid. However, the dual-frequency power oscillation problem might seriously threaten its stable operation. Based on the P/ω admittance model of the multi-VSGs parallel supercharger, a new perspective of dual-frequency power oscillation in multi-VSGs parallel supercharger system is discovered. Specifically, with the various numbers of parallel VSGs, the power oscillation amplitude trend of the supercharger system under load power perturbation (LPP) and grid frequency perturbation (GFP) is opposite. Moreover, the larger the number of parallel VSGs, the greater the power oscillation caused by the GFP, which more easily leads to overload operation of the power transformer. Therefore, a dual-frequency power oscillation suppression method based on error power feedforward compensation (EPFC) is proposed, which can suppress the dual-frequency oscillation under two different perturbations regardless of the variation in the number of parallel VSGs. Finally, a three-VSG parallel supercharger platform is constructed to verify the accuracy of the new perspective and the effectiveness of the oscillation suppression method.