DESIGN AND SIMULATION OF SLIDING MODE CONTROLLED HYBRID ACTIVE POWER FILTER Taruna JAIN Barkatullah University Institute of Technology, Bhopal, INDIA (e-mail: taruna_17@rediffmail.com ) Shailendra JAIN, Ganga AGNIHOTRI Department of Electrical Engineering, Maulana Azad National Institute of Technology, Bhopal, INDIA (e-mail: sjain68@gmail.com , gangag@yahoo.com ) Abstract—This paper presents design and simulation of a three-phase hybrid active power filter to eliminate the harmonics and compensate reactive power generated by non-linear load. A sliding mode controller is used to regulate the DC-bus voltage with hysterisis band current controller. Passive filters are tuned to fifth and seventh harmonic frequencies. Simulation results are presented to verify the performance during steady state as well as during transients. The spectral performance is judged and the results are observed well below the limits imposed by IEEE-519 standards. Keywords: hybrid active power filter, power quality, harmonics and reactive power, total harmonic distortion (THD), sliding mode controller. List of symbols v sa, v sb, v sc source voltages at phase a, b, c V sm * peak supply voltage V dc voltage across DC link capacitor V ref reference DC bus voltage i sa , i sb , i sc source currents at phase a, b, c I sm * peak supply current i sa * ,i sb * , i sc * reference source currents at phase a, b, c u sa , u sb , u sc unit current vectors for phase a, b, c f n n th harmonic frequency X Ln inductive reactance at n th harmonic freq. X Cn capacitive reactance at n th harmonic freq. Q c VAr size of capacitor Q quality factor of inductive coil s sliding surface i sx source current at phase x, where x = a, b, c i refx reference current at phase x, where x = a, b, c v sx source voltage at phase x, where x = a, b, c 1. INTRODUCTION In modern power system, power electronic devices are dominating the consumer end in both industrial and domestic region. Majority of these devices are non-linear in nature, results in injection of harmonics and draw reactive component of current. These non-linearities, if not controlled, may spread further in the whole system deteriorating the system performance [1-3]. To avoid this undesirable effect and to improve the power quality of the system, passive filters were used initially. But their use is limited due to fixed compensation, large size and resonance problems. Active power filters are seen as a viable alternative to passive filter for reducing current harmonics and reactive power due to their small size, no requirement for tuning and stable operation [4-6]. They act as harmonic current source to provide an effective result to eliminate the harmonic currents and also to compensate the reactive power. The active power filters are broadly classified into two types based on their configuration- voltage source type and current source type. Although active power filters give satisfactory results, some times their ratings are almost equal to the load rating; therefore they are not cost effective solution for both harmonic and reactive power compensation. The hybrid active power filter (HAPF) are seen to be more attractive solution for both harmonics and reactive power compensation now a days [7-8], which is basically the combination of active and passive filters. It utilizes the advantages of both type and eliminates the drawbacks of individual filter type. In hybrid active power filter, tuned passive filters are used for compensation of lower order