Boundary controller for dynamic voltage restorers to achieve fast dynamic response

The performance of using second-order switching surface in boundary control of dynamic voltage restorers (DVR) for improving the voltage stability of power system is examined. The switching surface is derived to estimate the state trajectory movement of the DVR after a hypothesized switching action. It results in a high state trajectory velocity along the switching surface. This phenomenon accelerates the trajectory moving towards the target operating point. The proposed boundary control method has been studied with computer simulations, as well as a low-power prototype. The dynamic responses of the DVR with different voltage sags and different loads, including a resistive load, inductive load and nonlinear load have been examined. It has been shown that the proposed boundary control scheme can achieve a faster transient and damping responses than the other control methods.