Multiple Loops of Current-Limiting Control for Grid-forming Inverters in the Overload Conditions

With the increasing penetration of renewable energy interfacing with the power grid, the voltage of the distribution network in some areas easily drops and the grid strength decreases. Energy storage can effectively smooth the fluctuations caused by renewable energy. Currently, some energy storage inverters can operate under the voltage source mode to improve the characteristics and stability of power grid. Under this situation, the current control ability of the inverter decreases, which means there will be bigger risk of overcurrent when facing large load fluctuations. To solve this issue, this paper proposes a control method including multiple loops of current-limiting control for the grid-forming converter. It utilizes energy storage as the DC front stage. With the combination of current limiter and power limiter, it is of significance to maintain voltage synchronization and balance the power flows in the saturation state. Simulation results verify the feasibility and effectiveness of the proposed method.