A shunt active power filter based on P-Q theory combined with high pass filters (HPFs) for harmonic-current compensation was proposed in this paper. A dual level H-bridge inverter (DLHI) and clamp diode multilevel inverter (CDMI) as inverters was used. The proposed active power filter was applied IntroductionThe power quality is determined by voltage swell, voltage sag, flicker, voltage interruption, negative and zero sequence components, voltage and current harmonics [1,2]. The use of non-linear load can increase a harmonic current [3]. The harmonic current also cannot contribute to the active power and need to be eliminated to enhance the power quality [4]. Recent efforts have been made to improve the power quality by reducing harmonic current based on active power filters [5]. A three-phase active power filters was proposed by [6]. This active power filter is controlled by the P-Q theory, the notch instantaneous method, and the positive sequence method. A pulse width modulation (PWM) was used as an inverter. This research shows that a notch instantaneous method can reduce a har monic current with the value of total harmonic distortion (THD) from 19.76 % down to 5.58 %. Furthermore, a positive sequence method can reduce THD to 12.76 %, THD depression does not occur significantly. Compared with the previous methods, the P-Q theory can reduce THD to 3.54 %. The THD result is lower than those of the notch instantaneous and positive sequence methods.A single-phase shunt active filter with a fuzzy controller and a PI controller for harmonic mitigation was proposed by [7]. This active power filter was applied to 230 V, and 50 Hz power systems. The fuzzy controller was reduced THD significantly in comparison with a conventional PI controllers. The dual-level inverter with a PI controller has THD of 8.39 %, which is higher than dual-level inverter with a fuzzy controller with THD of 5.68 %. In the case of a multi-level inverter, the PI controller has 7.10 % and it is also higher than multilevel inverter with a fuzzy controller with THD 4.47 %. Ref [8] proposed a 3-level (NPC) shunt active power filter based on P-Q theory combined with a fuzzy controller for harmonic-current compensation. The simulation results show that the effectiveness of the designed shunt active filter based on PWM fuzzy logic controllers. THD is reduced after compensation to 2.12 %.In this paper, we propose a shunt active power filter based on P-Q theory combined with high pass filters (HPFs) for harmonic-current compensation. In this research, we used a dual level H-bridge inverter (DLHI) and clamp diode multilevel inverter (CDMI) as the inverters. We applied the proposed active power filter to 3-phase 220 V and 50 Hz power systems. The superiority of P-Q theory includes the capability of working instantaneously and in time domain [9][10][11]. The P-Q theory is applied in 3-phase [12]. Hence, P-Q theory considers the 3-phase as a unit, not a superposition or sum of three single-phase circuits [13]. Therefore, the P-