Control methodology of three phase four wire current controlled voltage source active power filter for power quality improvement

In this paper two topologies of current controlled voltage source inverter (CCVSI) based active power filter using direct current control technique for compensating unbalanced loads in a three-phase four-wire system is proposed. In this method the harmonic compensation current reference is generated without introducing any additional harmonic extraction filtering circuits. A control approach for balancing the DC voltage of the active power filter is incorporated to cover the system losses. The proposed shunt active power filter compensates harmonics and reactive power in all three phases as well as the neutral current. To regulate and balance the dc capacitor voltage, a current control method using hysteresis controller is proposed. The simulation results based on MATLAB\Simulink tool demonstrate the feasibility of the proposed topologies. The total harmonic distortion of source current has been calculated and compared for two topologies to demonstrate important compensation characteristic of proposed control methodology of shunt active power filter.