Control of static synchronous compensator with supplementary damping enhancement for wind farm voltage regulation

This study presents a new control design approach for the wind farm voltage regulation using static synchronous compensator (STATCOM). A mode decoupling proportional plus integral (PI) controller, in which the control gains are synthesised by eigenstructure assignment (EA), is proposed for the STATCOM. EA is a state-space approach, which is used to improve system damping by eigenvalue assignment and alter system mode shape by eigenvector assignment. To embed the physical PI control loops in the state-space model, an equivalent transformation is proposed to map the feedback gain matrix to the PI controller. Owing to the presence of the physical PI control loops, the control signals would not mire into saturation when appropriate limiter according to the STATCOM capacity is placed in the control variables. To further alleviate the undesired oscillation mode excited by transient disturbance, a lead-lag-based supplementary damping controller (SDC) is adopted. Simulation comparisons are provided to show that the proposed technique can be an effective method for mitigating the voltage fluctuation in the wind farm because of the load changes and the wind gust.