Non-linear sliding mode control with SRF based method of UPQC for power quality enhancement

This paper proposed a method of non-linear sliding(NLS) surface based control strategy for controlling the dc link voltage of unified power quality conditioner (UPQC) to compensate the current harmonics, sag/swell and voltage unbalance. The proposed non-linear sliding surface depends on controlling the DC-link capacitor voltage so that the damping ratio of the system changes from its initial low value to its final high value. The proposed algorithm allows the dc-link capacitor voltage of UPQC to obtained low overshoot and small settling time, hence better compensation can be achieved. This paper also proposed the Novel synchronous-reference frame (SRF) control technique for the reference current and voltage generation for both converters. Results have been validated using the real-time performance analysis in Opal-RT Lab. A comparison has been made with the conventional Pi-controller and adequate results are considered for the verification.