Shunt active power filter with three-phase switch-clamped inverter

A novel three-phase two-leg switch-clamped inverter is presented to achieve multilevel PWM operation, harmonics elimination, reactive power compensation and dc-link voltage regulation. Four active switches with voltage stress of dc-link and two ac switches with voltage stress of half dc-link are used in the proposed inverter. In this paper, the proposed inverter is operated as a controllable current source to supply the necessary active power for the compensation of inverter losses, to suppress current harmonics, and to compensate the reactive power drawn from the nonlinear loads. Therefore, the balanced and sinusoidal line currents are drawn from the ac source. Two control loops are used in the adopted control scheme to maintain the constant dc-link voltage and to achieve the line current command tracking. The mathematical model of the proposed converter for the operation active power filter is derived and the control scheme is provided. Computer simulations and experimental results based on a laboratory scale-down prototype are presented to verify the effectiveness of the proposed control scheme.