A Low-Voltage Ride-Through Strategy for Cascaded H-Bridge Energy Storage Converters

Cascaded H-bridge (CHB) energy storage converter systems encounter issues such as overcurrent, power fluctuations, and three-phase current imbalance during grid voltage sags, which severely jeopardize the stable operation of the system. To address these problems, this paper proposes an improved droop control strategy based on virtual impedance and voltage compensation. While preserving the grid-forming characteristics of the converter, the control strategy effectively limits the transient inrush current and fault current amplitude during symmetrical faults by introducing virtual impedance. For asymmetrical faults, a dual second-order generalized integrator (DSOGI) is employed to separate the positive and negative sequence components of the grid-connected current. Combined with voltage compensation control, the converter’s modulation wave is corrected to suppress the negative sequence current, reduce power fluctuations, and ensure active power output. Simulation results on the PLECS platform demonstrate that, compared with the traditional droop control, the proposed strategy can effectively limit the fault current, suppress the negative sequence current, reduce power fluctuations, and ensure active power output.