Nonlinear Control Design of Three Terminal HVDC Transmission Systems to Improve FRT Capability

This paper proposes a state feedback control technique for three terminal high voltage direct current (HVDC) systems based on a voltage source converter (VSC) to mitigate the impact of perturbations, such as AC fault ride-through (FRT). The proposed system consists of three terminals, with one serving as an energy source, and are interconnected via a long HVDC cable. A sliding mode controller is designed to maintain constant DC voltage during AC faults in the grid and regulate the active and reactive powers at the other terminals. This method ensures robust performance in the presence of grid perturbations and enhances the stability and dynamic response of the VSC-HVDC system. The proposed control technique is implemented using Matlab/Simulink, and the obtained results demonstrate the robustness of the proposed control strategy under AC grid disturbance....