Modelling of a Hybrid Active Power Filter for Power Quality Improvement using Synchronous Reference Frame Theory Narendra Babu P 1 ∗ , Bhabani Kumari Choudhury 2 , Biswajit Kar 3 , Biswajit Halder 4 Dept. of Electrical Engineering, NIT Meghalaya, Shillong, India, 793003. Abstract— As day to day the power demand increase, the generation also increases, but the generated power output is not a pure one. A lot of harmonics are present in the generated power that can be a voltage harmonics, current harmonics or frequency deviation. Either of these causes instability to the power system. Because of the instability there may be variation of the speed of the motor occurs, may be abrupt surges appears in the output signal in the form of noises which can cause the raise in the temperature, increase in the speed beyond synchronous speed or a large mismatch in the rotor and stator angle which causes the blackout of the system. Due to the presence of harmonics causes many mismatch and problems in the system, this paper presents an innovative way to reduce the harmonics of the signal by which the signal can be directly feed to the grid using Synchronous Reference Frame theory. In this paper describes Proportional Integral and Hysteresis Current Controllers, PI controller are used for feedback mechanism and it is apply to compute switching losses of Active filter inverter, these losses are apply for Active current calculations. A mathematical modelling of a Synchronous Reference Frame (SRF) Compensation theory with proposed controller is explained. Simulation Results is achieved using MATLAB/SIMULINK and the consequences are shown for proposed compensation technique at different load and different filtering conditions. Keywords— Hybrid Active Power Filter; Hysteresis Controller; PI; Power Quality; Power System; Synchronous Reference Frame Theory; Total Harmonic Distortion. Introduction I. I. INTRODUCTION The power system agonizes with power quality problems due to manifestation of harmonics due to discontinuous loads. The presence of harmonics reduces life extent and enactment of the equipment connected to the power system. This harmonics causes voltage spikes, weakening, alteration and interference in the wave shape of the power transferring through the transmission lines [1]. The striving of harmonics is more in case of renewable energy generation and HVDC stations, which comprises with the power converters. The power quality is enhanced prominently by using filters [2]. Mainly there are three types filters are existed, they are passive filters (PF), active filters (APF) and hybrid filters (HF) [3]. Fig 1 shows the HAPF position in Transmission system network. The passive filters entails with the passive elements like resistor, inductor and capacitor to abolish harmonics. Thus, the scheming as well as regulatory of passive filters is simple and cost is also reduced noticeably. The passive filters aches with the difficulty of parallel resonance, bulky and fixed tuning. This difficulties are overwhelmed by the use of active filters. The active filters are more prominent to remove higher order harmonics. Shunt filters and series filters comes under the active power filter classification [4, 5]. The APF is fixed in parallel with the system and is capable of handling the harmonics commendably but it is more costly compared to series active power filters. The Series active power filters fixed in series to eliminate the harmonics by generating the voltages from the power source to filter out the voltages harmonics. To get the welfare’s of both passive filters and active filters the hybrid active power filters are designed [6]. The voltage rating of the HAPFs is less comparatively with the active filters, Thus the cost and size of HAPFs are reduced. It also offers superior performance in flattening the harmonic voltages. The controlling and operating of HAPF is thought-provoking task when it’s used in case of power converters [7-12]. Fig. 1: HAPF Position in Transmission system network International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 http://www.ijert.org IJERTV6IS030365 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Published by : www.ijert.org Vol. 6 Issue 03, March-2017 369