Neutral Point Potential Balancing Algorithm for Autonomous Three-Level Shunt Active Power Filter

This paper presents a control method of the input DC voltages of three-level Neutral Point Clamped (NPC) autonomous shunt Active Power Filter (APF), which is applied to eliminate line current harmonics and compensate reactive power. 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. A theoretical analysis with a complete simulation of the system is presented to prove the excellent performance of the proposed technique.