Linear quadratic control of SSSC to increase power oscillations damping of HVDC-AC power system

The HVDC-AC transmission system is becoming more and more popular for its numerous benefits, such as low cost, low losses for long distance transmission, etc. However, the power oscillation of this hybrid system has become a major obstacle for its further application. Tons of methods have been tried to damp the power oscillation and static series synchronous compensator (SSSC) is proved to be one of the most effective way for its excellent inherent characteristics. The SSSC offers many advantages as a FACTS device, but it is challenging to design a perfect controller for its application in a nonlinear system. In this paper, a linear-quadratic regulator (LQR) for SSSC is designed to increase power oscillations damping (POD) of an HVDC-AC power system. The LQR optimizes the system input (injected voltage of SSSC) to the reference value with full state feedback so that no vague controller parameter (such as PI controller parameters) is needed. The Algebraic Riccati Equation is introduced as well to provide the solutions for the controller parameters. Simulation results validate the feasibility of proposed modeling and control approach.