Optimal Impedance Reshaping Approach for Inhibiting Subsynchronous Oscillation in Virtual Synchronous Generator Based on SMES-Battery

Regarding a hybrid energy storage system (ESS) with superconducting magnetic energy storage (SMES) and battery, it can adopt the virtual synchronous generator (VSG) control to fulfill the grid-forming capability while doing more active voltage/frequency support. This article proposes an optimal impedance reshaping approach to inhibit the subsynchronous oscillation in the VSG based on the SMES-battery. Firstly, the theoretical modeling of the VSG as well as the SMES-battery is conducted. Then, the VSG's sequence impedance characteristic is investigated, and the subsynchronous oscillation influence is analyzed. By introducing an impedance reshaping link and revealing its effects on the VSG's low-frequency impedance, an optimized objective function with a minimum impedance phase difference is designed, and the improved particle swarm optimization is adopted for obtaining the solution. Using the MATLAB platform, a detailed simulation model is created, and different algorithms are considered to check the performance of the optimal impedance reshaping approach. Combining the time-domain simulation waveforms and frequency responses, the proposed method enables to effectively ameliorate the impedance features of the VSG, and inhibit the low-frequency oscillation while alleviating the power and current transients.