Wavelet Based Control Strategy for UPQC Control System Used for Mitigating Voltage Sag

This paper proposes a new control technique based on wavelet transform decomposition for Unified Power Quality Conditioner (UPQC) control system in order to compensate voltage sag. The new control technique extracts the reference voltages so fast; therefore, system voltages can be compensated fast and effectively and so, the injected voltages by series active filter decreases significantly. This control technique is used for estimating phase angle of voltages in a new control strategy which is designed to eliminate the harmonics and unsymmetrical components as well. Analyzing the new control technique as well as simulation results for mitigating voltage sag is presented to validate the control strategy. Comparison the technique with FFT control technique shows that the proposed control technique estimates the phase angle and amplitude of the system voltages faster than FFT algorithm and the compensation limits can be developed specially in the case of large phase angle jump caused by system faults.