An eight-switch three-phase VSI for power factor regulated shunt active filter

Abstract

A three-phase neutral point clamped (NPC) inverter operated as a shunt ac line conditioner is presented. Eight power switches and four clamping diodes with voltage rating vdc/2 are used in the proposed inverter. The presented inverter can compensate current harmonics and reactive power generated from the nonlinear loads, and supply the demanded dc side power of the inverter. If there is no nonlinear load connected to the system, the adopted inverter is operated as a power factor pre-regulator. If there is no output load connected to the dc side of the inverter, the inverter is operated as a shunt active filter. If a nonlinear load is connected to the ac source and a dc load is connected to the inverter, the adopted inverter is operated as an integrated power quality compensator to draw the sinusoidal line currents from the ac mains. To supply the necessary active power for the dc side load and compensate the power losses of inverter, a proportional-integral (PI) controller is used to obtain the active power for the inverter. A space vector pulse-width modulation (SVPWM) is used to track the line current commands. Simulation and experimental results based on a laboratory scale-down prototype are presented to verify the effectiveness of the proposed control scheme.