Supplementary power control scheme for an MMC-HVDC station considering inertia and damping

A supplementary power control strategy with enhanced damping is proposed for an MMC station to eliminate the active power deviation resulting from synchronous generator emulation control in the condition of steady-state grid frequency fluctuation. With the proposed method, the frequency command is corrected in real time by integrating the active power deviation to control the output power more accurately. A damping control is introduced to the supplementary power control loop. This can improve the dynamic performance and stability of the system. Also, a switching strategy is designed to achieve the selectivity needed for the converter station to participate in grid power regulation. Simulations are conducted in PSCAD/EMTDC to verify the effectiveness of the proposed scheme. The results show that the transition between grid-connection and island mode is not disturbed under the proposed method. Under steady-state grid operation, the deviation of DC voltage and output active power can be eliminated. This improves the steady-state performance of the MMC station; under the transient period, the power oscillation of the system is suppressed, and the output power of the converter station can be controlled quickly and accurately. © 2020, Power System Protection and Control Press. All right reserved.