Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator

Abstract

This article presents a super twisting sliding-mode control (ST-SMC) for single-phase dynamic voltage restorers (DVRs). Unlike the conventional first-order sliding-mode controller, the proposed ST-SMC technique eliminates the need for differentiating the compensation voltage in the sliding surface function while keeping the merits of first-order SMC. As a consequence of employing ST-SMC, a continuous control signal is achieved from which the pulsewidth modulation (PWM) signals can be generated. In this case, the inverter operates at a constant switching frequency. The stability analysis of ST-SMC is also presented. The reference compensation voltage needed in ST-SMC is estimated by using Brockett oscillator-based frequency-locked loop. Theoretical considerations are verified through experimental results under ideal and distorted grid voltage conditions. The obtained results show that the ST-SMC has good dynamic performance and can maintain the load voltage at a desired level under voltage sag, swell, and harmonically distorted grid voltages.