A model-based controller for a half-bridge NPC used as an active power filter

This paper presents a model-based controller for an active power filter (APF) to compensate reactive power and current harmonic distortion in a single-phase system. A Half-bridge Neutral Point Clamped (NPC) topology is selected as a voltage source inverter (VSI) to implement the APF. The control scheme is composed by three control loops referred as the inner control loop (or current loop), the regulation loop, and the balance control loop. The inner control loop is aimed to compensate both the displacement power factor (DPF) and the harmonic distortion of the current flowing to the grid. Only compensation of odd harmonics is considered which is the distortion present in most single-phase non-linear loads. The regulation and balance loops are designed to achieve the regulation and balance of the capacitor voltages in the DC-link. Numerical results are presented to show the performance of the proposed solution.