4-leg shunt active power filter with hybrid predictive fuzzy-logic controller

Distribution networks commonly utilize three-phase four-wire systems, especially for low-voltage industrial and residential customers. Due to the rapid increase of nonlinear and unbalanced reactive loads in such systems, several power quality issues arise. Among them, line current harmonics, unbalanced load currents, noticeable neutral current and low power-factor. This paper presents a 4-leg shunt active power filter (APF) featuring reactive power compensation, line current harmonics mitigation, neutral-current reduction and system load-currents balancing. The authors propose hybrid controller for the 4-leg shunt APF: Fuzzy Logic Control (FLC) for the DC-link voltage and predictive control for the grid current. The DC-link voltage FLC handles the system uncertainties and nonlinearities, hence improving the transient performance. In addition, the proposed predictive current control technique features phase locked loop (PLL) independency. Moreover, the proposed hybrid controller necessities sensing only the grid voltage and current, hence less number of sensors are required.In addition, implementation simplicity and cost reduction are achieved. The proposed controller is simulated using Matlab/Simulink^® package. For effectiveness verification, system performance is investigated under several loading conditions.