International Journal of Advances in Engineering & Technology, Jan 2012. ©IJAET ISSN: 2231-1963 331 Vol. 2, Issue 1, pp. 331-341 ANALYSIS OF DISCRETE & SPACE VECTOR PWM CONTROLLED HYBRID ACTIVE FILTERS FOR POWER QUALITY ENHANCEMENT Jarupula Somlal 1 , Venu Gopala Rao Mannam 2 , 1 Assistant Professor, Department of EEE, K L University, Vijayawada, A.P, India 2 Professor & Head, Department of EEE, K L University, Vijayawada, A.P, India ABSTRACT It is known from the fact that Harmonic Distortion is one of the main power quality problems frequently encountered by the utilities. The harmonic problems in the power supply are caused by the non-linear characteristic based loads. The presence of harmonics leads to transformer heating, electromagnetic interference and solid state device mal-functioning. Hence keeping in view of the above concern, research has been carried out to mitigate harmonics. This paper presents an analysis and control methods for hybrid active power filter using Discrete Pulse Width Modulation and Space Vector Pulse Width Modulation (SVPWM) for Power Conditioning in distribution systems. The Discrete PWM has the function of voltage stability, and harmonic suppression. The reference current can be calculated by‘d-q’ transformation. In SVPWM technique, the Active Power Filter (APF) reference voltage vector is generated instead of the reference current, and the desired APF output voltage is generated by SVPWM. The THD will be decreased significantly by SVPWM technique than the Discrete PWM technique based Hybrid filters. Simulations are carried out for the two approaches by using MATLAB, it is observed that the %THD has been improved from 1.79 to 1.61 by the SVPWM technique. KEYWORDS: Discrete PWM Technique, Hybrid Active Power Filter, Reference Voltage Vector, Space Vector Pulse Width Modulation (SVPWM), Total Harmonic Distortion (THD), Voltage Source Inverter (VSI). I. INTRODUCTION High power non-linear and time varying loads, such as rectifiers, office equipments like computers and printers, and also adjustable speed drives causes undesirable phenomena in the operation of power systems like harmonic pollution and reactive power demand [1-2]. The application of passive tuned filters creates new system resonances which are dependent on specific system conditions. In addition, passive filters often need to be significantly overrated to account for possible harmonic absorption from the power system. Passive filter ratings must be co-ordinate with reactive power requirements of the loads and it is often difficult to design the filters to avoid leading power factor operation for some load conditions [3-4]. Parallel active filters have been recognized as a viable solution to current harmonic and reactive power compensation. Various active power filter configurations and control strategies have been proposed and developed in the last decade in order to reduce these undesirable phenomena. Active filters have the advantage of being able to compensate for harmonics without fundamental frequency reactive power concerns. This means that the rating of the active power can be less than a comparable passive filter for the same non-linear load and the active filter will not introduce system resonances that can move a harmonic problem from one frequency to another. The active filter concept uses power electronics to produce harmonic current components that cancel the harmonic current components from the non-linear loads. The active filter uses power electronic switching to generate harmonic currents that cancel the harmonic currents from a non-linear load. The active filter configuration investigated in this paper is