Adaptive nonlinear control of series APFs: Harmonics grid voltage compensation and inverter DC voltage regulation

The problem of controlling three-phase series active power filters (series APF) is addressed in presence of nonlinear loads. An oriented control model for Series APF-load system is developed in (α, β) coordinates. The control objective is twofold: (i) compensating for the harmonic and disturbed voltages components at the PCC, this objective is referred to voltage quality (ii) Regulating the inverter DC capacitor voltage. To this end, a nonlinear adaptive controller is developed, using the backstepping design, on the basis of the averaged system model. Moreover, the controller is made adaptive for compensating the uncertainty on the switching loss power. The performances of the proposed adaptive controller are formally analyzed using tools from the Lyapunov stability. The theoretical results are confirmed by numerical simulations.