Abstract
This paper addresses the nonlinear controller design and the stability analysis of a shunt active power filter (SAPF) interfacing a solar photovoltaic (PV) system that consists of a couple of PV panels, a single-phase two-stage IGBT half-bridge SAPF and two identical DC link capacitors. We seek for the considered system the fulfillment of three control objectives: (a) extracting the maximum PV power using an appropriate maximum power point tracking (MPPT) algorithm; (b) regulation of the DC link capacitor voltages to the reference provided by the MPPT controller hence ensuring the exchange of power between the PV source and the AC power grid; (c) compensation for reactive power and undesired harmonics caused by the nonlinearity of electronic power loads, that is, performing power factor correction (PFC). The control objectives are achieved using a new two-loop cascaded controller. The Backstepping approach is applied in the inner loop to perform PFC. A filtered proportional-integral (PI) controller is applied in the outer loop to ensure tight regulation of the PV voltage. The MPPT control is implemented using a perturb-and-observe (PO) algorithm. The performance of the closed-loop system under the two-loop control strategy is formally analyzed through the Lyapunov approach applied to the averaged model. Numerical simulations are performed in MATLAB/SimPowerSystems environment to validate the design methodology and to confirm the theoretically predicted performances of the system under the proposed nonlinear controller.