Investigations on shunt active power filter for power quality improvement

Most of the pollution issues created in power systems are due to the non-linear characteristics and fast switching of power electronic equipment. Power quality issues are becoming stronger because sensitive equipment will be more sensitive for market competition reasons, equipment will continue polluting the system more and more due to cost increase caused by the built-in compensation and sometimes for the lack of enforced regulations. Efficiency and cost are considered today almost at the same level. Active power filters have been developed over the years to solve these problems to improve power quality. Among which shunt active power filter is used to eliminate and load current harmonics and reactive power compensation. In this work both PI controller based and fuzzy logic controlled, three-phase shunt active power filter to compensate harmonics and reactive power by nonlinear load to improve power quality is implemented for three-phase three wire systems. The advantage of fuzzy control is that it is based on linguistic description and does not require a mathematical model of the system. The compensation process is based on sensing line currents only, an approach different from conventional methods, which require sensing of harmonics or reactive power components of the load. A MATLAB program has been developed to simulate the system operation. Various simulation results are presented under steady state conditions and performance of fuzzy and PI controllers is compared. Simulation results obtained shows that the performance of fuzzy controller is found to be better than PI controller. PWM pattern generation is based on carrier less hysteresis based current control to obtain the switching signals to the voltage sourced PWM converter