Improvement of power quality under distorted source and nonlinear load conditions

This paper proposes an enhanced control strategy for unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate harmonics in the distorted supply voltage and nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller and a resonant controller tuned at six multiple of the fundamental frequency of the network (6 ωS) are performed to compensate harmonics in distorted source, meanwhile a PI controller and three resonant controllers tuned at 6nωS (n=1, 2, 3) are designed in the shunt APF control scheme to mitigate harmonic currents produced by nonlinear loads. Thereby, the load voltage and the supply current are regulated to be sinusoidal waveforms. Performance of the UPQC is significantly improved compared to the conventional control strategy thanks to the superiority of resonant controllers. The feasibility of the proposed UPQC control scheme is validated through the simulation.