An active power filter implemented with PWM voltage-source inverters in cascade

A three-phase active power filter implemented with two PWM voltage-source inverters connected in cascade is presented and analyzed in this paper. The active power filter is connected in parallel to the system and can compensate the reactive power and the harmonic current components of high power nonlinear loads. By using two PWM voltage-source inverters in cascade, the compensation characteristics of the active power filter are significantly improved. The voltage-source inverter connected closer to the nonlinear load compensates the reactive power and the low frequency current components required by the nonlinear load, while the second inverter compensates only the high frequency current components. For this reason the first PWM inverter can be implemented with GTOs operating at lower switching frequency while the second inverter can use IGBTs since it has to operate at higher switching frequency. In particular, this paper discusses the proposed scheme in terms of principles of operation, and the analysis under transient and steady state operating conditions. The computer simulation for the proposed active power filter has been done and the results show excellent static and dynamic performances