Optimized Sliding Mode Control to Maximize Existence Region for Single-Phase Dynamic Voltage Restorers

This paper presents an optimized sliding mode control (SMC) strategy to maximize existence region for single-phase dynamic voltage restorers. It is shown analytically that there exists an optimum sliding coefficient which enlarges the existence region of the sliding mode to its maximum. Also, it is pointed out that the optimum sliding coefficient improves the dynamic response. In addition, a double-band hysteresis control which ensures the switching of a transistor in the voltage source inverter during a half-cycle while it remains either on or off in the other half cycle is used to mitigate the switching frequency. The theoretical considerations and analytical results are verified through computer simulations and experimental results. Simulation and experimental results show that the proposed SMC strategy not only compensates the undesired voltage disturbances and maintains the load voltage at desired level with low total harmonic distortion, but also exhibits fast dynamic response and operates at reasonably low switching frequency.