الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Hybrid active power filters (HAPF) have been greatly recommended as a novel solution to harmonics and reactive power compensation. The HAPF has been introduced to eliminate the problems of using passive filter alone such as harmonic resonance, and the problems of active power filter (APF) such as high dc link voltage and increased switching losses. In this thesis, a detailed modified algorithm of a HAPF is introduced using MATLAB/SIMULINK platform. The proposed power circuit consists of a supply system and a nonlinear load. The combined nonlinear load comprises a 6-pulse rectifier feeding R-L load, and a direct torque control (DTC) induction motor drive system. The HAPF consists of a passive filter tuned at the 5th harmonic. This passive filter is connected in series to an APF forming the HAPF, which is connected across the load. The use of both filters provides the advantage of each type, as the passive filter is used to mainly mitigate the low order harmonics, while the APF is used to suppress the high order harmonics. The dc link voltage of the APF is reduced due to the voltage DROP on the passive filter. This voltage DROP decreases the applied voltage on the APF, which in turn reduces the losses caused by switching. The proposed control technique mainly aims to obtain better total harmonic distortion (THD) values, and reduced dc link voltage. Therefore, the operation of the APF can be optimized by reducing its size, cost, switching losses, and therefore, obtain enhanced performance of the overall system during variable nonlinear loads. The proposed control algorithm is divided to three control circuits. The main control circuit is based on the synchronous reference frame theory (SRF), it is used as a detection circuit to the load and filter current. The second control circuit is used to control the dc link voltage using a PI controller. The third one is used to extract the 5th harmonic component from load current and then injecting this component into the main control circuit. The overall control system is simulated, and extracted results are discussed concerning the values of the dc link voltage and the THD.