A dual-limiting power balance controller for multiterminal VSC-HVDC system

To enable zero-power tracking error in steady state and to ensure system security during power unbalance, we proposed a dual-limiting power balance controller for multiterminal voltage-source converter high-voltage direct current (MTDC). The dual-limiting controller is composed of an upper limiting loop and a lower limiting loop. By specifically setting the limits of the integrators and limits of the total output of the limiting loops, the dual-limiting controller is automatically disabled if direct current terminal voltage stays within the specified limits and is automatically enabled if there is unbalanced power. Simulations on a 4-terminal MTDC system under unbalanced power orders, alternating current faults, and wind power fluctuations verified the efficacy of the proposed controller. The dual-limiting power balance controller is promising for direct current voltage control of MTDC.