NPC three-level four-legged Shunt Active Power Filter under Non-Sinusoidal Power Supply Conditions

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