A modified droop control structure for simultaneous power-sharing and DC voltage oscillations damping in MT-HVDC grids

With increasing energy demand, the use of renewable energy resources is increasing. Renewable energy sources require power electronic converters to get integrated into power grids. Multi-terminal high voltage direct current (MT-HVDC) systems are a promising solution for their grid integration. Using droop-based controller strategies in power converter stations of MT-HVDC grid, in addition, to providing power-sharing, can support the frequency of the connected AC grids. However, power changes lead to direct voltage deviations, thereby disrupting the stability of the MT-HVDC system. Here, a new control structure for the droop controller of the voltage source converter (VSC) controller is proposed which is named modified droop controller (M-Droop). This method, in addition to power-sharing, uses an appropriate control action to provide the required voltage stability. Here, analytical studies of the modified control strategy are reported. Moreover, through a developed MATLAB Simulink platform, its performance is verified in the events of transients, consisting of fault, variable load, and change in power generation.