Digital Active Power Filter Controller Design for Current Harmonics in Power System

Nonlinear loads are essential part of power system. With the advancement in power electronics, switching elements have major share in electrical load. These elements create nonlinearities in lines increasing the line losses, reducing power quality and purity of sin wave. Passive filters work fine for harmonic elimination for specific frequencies which are considered in design specification. Active filters on the other hand work according to harmonics currently in line. Active filter designed in this work consists of a shunt active power filter that compensates current harmonic due to non-linear load. The active filter has a voltage source converter (VSC) which works in back to back configuration with a DC coupling capacitor. Power is injected by the VCS at the point of common coupling (PCC). The reference current is generated using instantaneous power theory. The harmonic components are separated from reference current, the reference is compared with actual current and the pulse width to control VSC is adjusted by the controller. The strength of proposed approach is illustrated through simulation in MATLAB software. The simulation results are then cross verified in real time using experimental setup. Total harmonic distortion (THD) of line current analyzed by fast Fourier transform (FFT) analysis is reduced to 4.56% from 28%.