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Abstract
In a modern power system, due to broader applications of nonlinear loads such as power electronic equipment or arc furnaces, the degree of waveform distorted is more serious nowadays. These loads may cause poor power factors, lead to voltage notch or result in high degree of harmonics. Such power pollution has made power quality an increasing concern. Moreover, from the economical viewpoints, a utility‟s revenue may be affected at a higher cost. Therefore, an efficient solution for solving these pollution problems has become highly critical for both utilities and customers. Due to the rapid progress in modern power electronic devices and state-of-the-art electronic circuit technology, the active power filters (APFs) have been developed and put into practical applications. The APF can solve problems of harmonic and reactive power simultaneously. Modern active power filters (APFs) were introduced for high-quality compensation of the harmonics of nonlinear loads due to the weaknesses of the conventional passive filter. The shunt APF detects the harmonic spectrum of the load current and generates an output current, which ideally is of the same harmonic spectrum as of the load current but in opposite phase. In this way, the APF cancels out the harmonic currents and leaves the fundamental current component to be provided by the power system. One of the cornerstones of the active filter is its control strategy that is implemented in the active filter controller. Traditionally, Many kinds of control strategies of shunt APF are studied under sinusoidal and symmetrically voltage conditions.