| Summary: | Electrical power quality has grown from obscurity to a major issue due to the wide use of non-linear power electronic loads in many applications. Passive filters have been extensively used to prevent harmonics from entering the power system. However, there are many disadvantages and hence active power filters provide an alternative solution to the passive filters. Active power filters have the advantages over the passive filters such as low cost, smaller physical size and are able to compensate for randomly varying harmonic currents. In this thesis, Shunt active power filters have been employed for harmonic current and reactive power compensation for typical non-linear loads. The characteristics of active power filters have been discussed and the operation modes of both single-phase and three-phase active power filters have been documented. The proposed APF system is based on voltage-source current-controlled PWM converter topology, and uses two separate controllers, namely current control loop (CCL) and voltage control loop (VCL). CCL deals with the supply current using a PI controller for current harmonic reduction by injecting the required amount of harmonic current components with equal in magnitude but opposite in polarity to the utility to cancel the harmonic currents produced by the non-linear power electronics load. The VCL is based on sliding mode (SLMC) control, it served two purposes: it regulates and maintains the DC capacitor voltage at a constant level and provides the feedback information for the reference current. The design of the proposed active power filter system has been carried out using ORCAD PSPICE simulation software package. The contribution of this research work is in-depth investigation of the shunt active power filter for supply current harmonics reduction and reactive power compensation, the current waveform is maintained sinusoidal and in phase with the supply voltage for a given non-linear load so as to improve the power factor. The current information is extracted using the supply current detection method and the voltage source current controlled PWM converter is employed to extract the voltage information required for the APF action. The simulation and practical results are discussed and conclusion drawn.
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