This paper proposes a novel control strategy for a unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate the harmonics in both the distorted supply voltage and the nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller and a resonant controller tuned at six multiples of the fundamental frequency of the network ($6{omega}_s$) are performed to compensate the harmonics in the distorted source. Meanwhile, a PI controller and three resonant controllers tuned at $6n{omega}_s$(n=1, 2, 3) are designed in the shunt APF control scheme to mitigate the harmonic currents produced by nonlinear loads. The performance of the proposed UPQC is significantly improved when compared to that of the conventional control strategy thanks to the effective design of the resonant controllers. The feasibility of the proposed UPQC control scheme is validated through simulation and experimental results.