A DC Voltage Optimal Control Strategy for VSC-MTDC Systems

In order to improve the stability of VSC-MTDC systems, a DC voltage optimal control strategy that is suitable to multi-terminal HVDC systems is proposed. This strategy combines the advantages of DC voltage deviation control strategy and DC voltage droop control strategy. In order to balance system power in different conditions, each converter station is coordinated by the changed amount of DC voltage. When there is a small fluctuation in power system, a part of converter stations that are connected to the active system will be applied to adjust system power to maintain system stability. When a large fluctuation occurs in power system, all converter stations that are connected to the active system will be applied to adjust system power to maintain the stability of DC voltage, and therefore to avoid big changes of DC voltage. In the end, the characteristics of DC voltage optimal control strategy are simulated and analyzed in Matlab/Simulink simulation platform, and simulation results verify its validity and feasibility.