Performance evaluation of hybrid active filter for power quality improvement of electrical distribution system

Rapid growth of non-linear loads in distribution systems has attracted power system engineers' attention from power quality point of view. Connection of the non-linear loads deteriorates power quality in the distribution system by introducing current harmonics. These current harmonics, when circulated in the electric network, interact with the system impedance and generate voltage harmonics. These current and voltage harmonics together can affect other consumers connected in the distribution network. Some typical non-linear loads, such as electric arc furnace (EAF), are inherent source of voltage harmonics which gives rise to voltage flicker, which can causes large voltage fluctuation in the connected distribution system. This paper presents performance evaluation of hybrid active filter (HAF) for power quality improvement (EAF) connected distribution system. The performance of HAF is evaluated in terms of harmonic and voltage flicker mitigation capability. The HAF is consisting of a shunt passive filter (PF) connected with a lower rated voltage source PWM converter based series active filter (SAF). There are various control strategies for series active filter control is surveyed in the literature. One of the control strategy based on the dual formulation of the electric power vectorial theory is implemented for balance and resistive load. In this paper an attempt is made to apply the same control theory for unbalanced and non-sinusoidal voltage conditions of the distribution system. A state-space averaging model of HAF constructed to analyze its system stability by traditional control strategy taking into account the effect of the time delay. Performance of the HAF is compared and analyzed with that of the (PF) to improve power quality at point of common coupling (PCC) as per the IEEE standards. Simulation for a typical distribution system along with the PF and the SAF has been carried out in MATLAB environment to validate the performance.