Adaptive Backstepping Control of Three-Phase Four-Wire Shunt Active Power Filters for Energy Quality improvement

The increasing use of nonlinear loads entails serious electrical energy quality problem in power grids. In this paper, the energy quality issue is dealt with by using three-phase four-leg shunt active power filters (SAPFs). A new model that describes the whole controlled system including the SAPF and associated nonlinear and unbalanced loads is developed. The model also accounts for the electrical grid line impedance. The control objective is threefold: to make up for the harmonics and the reactive currents absorbed by the loads; to cancel the neutral current; and to regulate the inverter DC capacitor voltage. Based on the new model, a nonlinear controller is designed, using the backstepping technique. Moreover, the controller is made adaptive for compensating the uncertainty on the switching loss power. The performances of the proposed adaptive controller are formally analysed using tools from the Lyapunov stability and averaging theory, and their supremacy with respect to standard control solutions is illustrated through simulation. © 2015, Brazilian Society for Automatics--SBA.