A model-based controller for a single-phase active filter using a full bridge NPC

This paper presents the modeling and control design of a single-phase full bridge neutral point clamped (FB-NPC) multilevel converter used in an active power filter (APF) application. The proposed topology is aimed to compensate reactive power and current harmonic distortion. Based on the system model, a multi-loop controller is proposed, which is aimed to accomplish three control objectives, namely, AC current tracking, and DC voltage regulation and balance. The controller comprises two main loops referred as the inner (current) loop, and the outer (voltage) loop. The outer loop includes both the regulation loop and the balance loop. The inner loop is aimed to compensate both the power factor (PF) displacement and the harmonic distortion of the grid current. The control design considers odd harmonics of the fundamental, as this is the usual distortion present in single-phase nonlinear loads. The proposed solution guarantees a line current proportional to the fundamental component of the grid voltage. Numerical results are presented to assess the performance of the proposed solution. Experimental results are under development and will be presented in the final version of the paper.