A Novel FPGA based PWM Active Power Filter for Harmonics Elimination in Power System

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 has been 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. Active power filters have been developed to solve these problems to improve power quality. Shunt active power filter have been used to eliminate load current harmonics and also for reactive power compensation. The Active Power Filter (APF) has been implemented with Pulse Width Modulation (PWM) based on current controlled Voltage Source Inverter (VSI). This VSI switching signals have been generated through proposed three-level Hysteresis Current Controller (HCC) that achieves significant reduction in the magnitude and variation of the switching frequency. The system has been modeled and investigated under different unbalanced non-linear load conditions. The simulation results reveal that the active power filter has been effectively compensating the current harmonics. Due to non-linear characteristics, the load current gets distorted which causes undesirable effects like heating, equipment damages etc. in power network. APF is the best solution for eliminating the harmonics caused by the non-linear loads. This paper presents the three-phase four-wire active filter for Power Line Conditioning (PLC) to improve power quality in the distribution network and also implementation of a digitally controlled APF. Synchronous reference frame has been used for generation of reference current. PI currents algorithm and HCC together has been written in VHDL code and were implemented using SPARTAN VI 854 Sreekanth C. and Dr.Moni R. FPGA platform. Various simulation results has been presented under steady state and transient state condition and their performances has been analyzed. Simulation results obtained shows that the performance of three phase system with APF has been found to be better and a digital controller add a new aspect for the controller from low cost, high speed and hardware implementation. Thus PWM and hysteresis based current control has been used to obtain the switching signals to the VSI.