Development and implementation of novel techniques for the control of shunt active filter

Abstract

The wide spread use of non-linear loads such as adjustable speed drives, silicon controlled Rectifiers, furnaces, and uninterruptible power supplies (UPS) inject harmonics into the power system. However, the passive filters have the demerits of fixed compensation, bulkiness and occurrence of resonance with other elements. Also, in practical applications, the amplitude and the harmonic content of the load current can vary randomly; under such conditions the conventional solution becomes ineffective. With recent developments in power electronic switches, the Active Power Filters (APFs) have been applied to mitigate the problems created by non-linear loads. One of the most commonly used active filters is the Shunt Active power Filter (SAF) which is used to eliminate the unwanted harmonics and compensate reactive power consumed by non-linear loads by injecting the compensation currents into the AC lines. The most important task in the development of Shunt Active Filter is the implementation of the current control strategy to derive switching pulses for the Voltage Source Inverter (VSI). Hysteresis current control is the most commonly used method for current control, due to its simplicity in implementation. A fuzzy logic based PWM current control technique is developed to eliminate harmonics and compensate reactive power under varying load conditions. The performance of the shunt active filter with the proper control strategy is good since the controller does not need an accurate mathematical model; it can work with imprecise inputs and can handle nonlinearity. Computer simulations are carried out on a sample power system to demonstrate the effectiveness of the proposed control strategies and reference current extraction techniques for different source and load conditions. Finally, an experimental prototype is built for the proposed controller in DSP platform using TMS320LF2407A processor. The implemented hardware is tested for ideal source voltage condition.