NEUTRAL POINT POTENTIAL BALANCING ALGORITHM FOR SLIDING MODE CONTROLLED THREE-LEVEL ACTIVE POWER FILTER

Abstract

In this paper, the authors present a study of the instability problem of the input DC voltages of the three-level Neutral Point Clamping (NPC) Active Power Filter (APF). This APF is applied for the enhancement of voltage network power quality by compensation of harmonic currents produced by a nonlinear load. In the first part, the authors present a topology of three-level NPC Voltage Source Inverter (VSI), and its space vector diagram. In the second part, as solution for instability problem of the input DC voltages of the APF, the authors propose a simplified Space Vector Pulse Width Modulation (SVPWM) with neutral point potential control. After that, the sliding mode regulator used to control the APF is developed. Stable DC bus supply associated with sliding regulator of APF allows getting low harmonic content network currents with unity power factor.