Power Quality Enhancement in Four-Wire Systems under different distributed Energy Resource Penetrations

Reactive and harmonic currents that are being injected into the power supply by nonlinear loads, cause an increasing deterioration of the power system voltages and currents, whereas active power filter (APF) has been widely used to overcome this problem and to improve the power quality delivered by the power supply. In this paper, a three-level four-legged active power filter based on a neutral-point-clamped (NPC) inverter is presented. To fulfil the requirement of the active power filtering function under balanced, unbalanced, and distorted (including 3rd and 5th harmonics) power supply voltages, a control method based on the instantaneous power theory has been used and discussed. On the other side, the inverter switching state control has been achieved based on PWM current controller. The performance of the proposed topology under the control approach has been finally discussed through the obtained simulation results.