الفهرس 
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Abstract
Semiconductor switches are widely used to deliver controlled electrical power to loads such as furnaces, adjustable speed drives, and uninterruptible power supplies. Non-linear loads and solid-state converters are sources of harmonics, and draw reactive power from the AC system. In three-phase unbalanced power systems, non-linear loads may cause unbalanced excessive harmonic currents (including the triplen) to flow in the neutral wire. Harmonic currents, reactive power demand, and excessive neutral currents cause adverse effects on the power system such as low efficiency of distribution systems, abnormal operation of protection systems, poor power factor, overloading of capacitor banks, nuisance tripping, de-rating of distribution and user equipment, noise and vibration in electrical machines, etc.
Traditionally, passive filters have been used to reduce definite harmonic orders but have some disadvantages such as large size, possibility of resonance and fixed compensation. The significant increase of non-linear loads in electrical power systems makes engineers to design many solutions to solve power quality problems. Active power filters (also called active power line conditioners or active power quality conditioners) are one of the most effective solutions for power quality problems. Active power filter can be classified into several categories. These are; shunt active power filters (SHAPF), series active power filters (SEAPF), and unified power quality conditioners (UPQC).
Several algorithms are available to control the operation of active power filters. Among these methods are the instantaneous active and reactive power theory (p-q theory) and the Synchronous reference frame control theory (the d-q theory).
The p-q theory is accurate and more effective for harmonic mitigation and remedy of other power quality problems. However, it requires more sophisticated and expensive setup for practical implementation. On the contrary, the d-q theory is less effective for harmonic mitigation and remedy of power quality problems, but it is easier to implement, as it requires less number of sensors for the experimental setup. Hence, the d-q theory closely resembles the real time simulation as it experiences less delay time for data acquisition and processing.
In this thesis, a rigorous and an easily manipulated analysis has been developed for the determination of the effect of SHAPFs, SEAPFs and UPQCs on the power quality of electrical power systems. The analysis accounts for different power quality problems, namely; harmonics, reactive power compensation, voltage sag, voltage swell, and unbalanced of non-linear load. The analysis has been carried out using the SIMULINK/MATLAB software package. The p-q theory of control is used in this analysis as it is accurate and more effective for harmonic mitigation and remedy of other power quality problems. The results of the thesis have shown that SHAPFs are effective for current harmonic mitigation, SEAPFs are effective for the remedy of voltage harmonics, sags, and swells, and UPQCs are more suitable for all power quality problems. Use of the phase locked loop (PLL) in conjunction with SHAPFs enhance significantly the power quality problems and reduce appreciably the total harmonic distortion (THD) of the harmonic system especially in the presence of distorted AC sources.
Special considerations have been given in this thesis to the design and implementation of experimental setup for the SHAPFs. The SHAPF is chosen as it is widely used in distribution systems in parallel with non-linear loads to mitigate harmonic current distortions. Also, it is easy to implement and construct using simple and cheap components and circuits in the laboratory. The d-q theory is used in this design since it requires a smaller number of sensors for the experimental setup. The system consists of three main parts: 1) A three phase auto-transformer which represents a variable three phase balanced power supply, 2) A non-linear load which is a three-phase rectifier bridge supplying dc power to a resistive load, 3) A three phase Inverter which represents the shunt active filter. The SHAPF is based on intelligent power module (IPM). The IPM is a module product, based on a 3-phase inverter circuit with a control IC that contains a gate driving circuit and other protection circuits (short circuit, supply under voltage, and over temperature). This product makes it easier to design peripheral circuits than conventional IGBT modules with external driver circuits.
The IPM consists of six IGBT switches that receive the driving signals from the system controller. The controller is An Arduino Duo, ARM Cortex AT91SAM3X8E. A d-q theory-based control strategy is programmed and is deployed on an embedded controller to feed the inverter PWM driving signals. The three phase load currents and inverter currents are six feedback signals measured by six Hall Effect current sensors. A programmed PLL circuit receives voltage supply signal of phase “a” via voltage sensor to generate the phase angle required in Park’s transformation. The inverter dc input side is connected to a polarized capacitor which is a storage energy device delivers the dc power desired to configure active and reactive power, while the output is linked to point of common coupling (PCC) by using three shunt inductors. The DC capacitor voltage sensor measures the dc voltage level.
Experimental results are measured, depicted, and analyzed to verify the same results from the simulation model. The results display the waveforms of the source current, load current, inverter current, and source voltage to demonstrate the effectiveness of SHAPF on harmonics mitigation.