Finite Control Set based Optimized Model Predictive Current Control of Four-leg Shunt Active Power Filter

Abstract

This paper presents a finite control set based Model Predictive Current Control (MPCC) of a four-leg Shunt Active Power Filter (SAPF) to mitigate the current harmonics and balance a three-phase four-wire system. A four-leg inverter is considered to balance the three-phase currents in the distribution system under unbalanced load conditions. The four-leg inverter provides a path for the neutral current to flow on the load side. The instantaneous i_{d_axis}-i_{q_axis} current method is applied to estimate the required compensating current. The squared error based cost function optimization is proposed in the MPCC technique. The classical current control techniques for four-leg SAPF use PID regulators to mitigate the current harmonics and to balance the load current. The proposed SAPF using MPCC technique has the inherent advantage of zero modulation stage and the control part considers only the mathematical model of the system which eliminates the requirement of PID regulator. The performance of the proposed four leg SAPF using MPCC control strategy has been evaluated under different source voltage and load conditions. The simulation results of the proposed system prove that the four-leg SAPF with MPCC is more desirable for effective current harmonic compensation and to balance the three-phase four-wire distribution system.