الفهرس 
Power quality overviewOnly 14 pages are availabe for public view
 |  | from | 133 |  |  |
| | | from | 133 | | |
Abstract
The modern society uses more power electronic devices in order to function together. This put higher burden on the electrical grid when compared to the past loads. Therefore, utility companies are obliged to keep the voltage within certain limits by mitigating harmonics in the system. This thesis objective is to mitigate the current harmonics to a reasonable value which is actually one of the power quality issues. To attain a realistic mitigation more proactive, continuous measurements of the nonlinear loads needs to be done. Then the mitigation technique and the locations have to be carefully selected in the beginning to get a wider perspective of mitigation in the grid. The thesis explains the different types of mitigation techniques of current harmonics used in power systems. It also surveys different types of active power filters control techniques that are used and reference current generation techniques used for active power filters, it also shows the comparison between the Double Capacitor Double Switch (DCDS) filter and the voltage source inverter active power filter. It compares the use of Artificial Neural Network (ANN) harmonic estimation technique which is suitable for generating the reference current estimation of Shunt Active Power Filter(SAPF). Among the different types of neural networks, the Radial basis function artificial neural network (RBFANN) is tested for the two filters. The proposed Active filter (DCDS) filter is as from its name consists of two switches and two capacitors. The switches are used to pass fundamental and switching frequencies while the two capacitors are to attenuate the fundamental and pass the higher frequencies only. The control strategy used to control the filter is the hysteresis control and it is used for both filters. The DCDS filter is used as the proposed circuit, which is one of Switched Capacitor Active Power Filters (SCAPF). A generalized model of switching function block is developed first. The proposed DCDS circuit is derived from the generalized model. The DCDS capacitance is calculated using parallel resonance equation. The two filters are tested and compared. Both filters were simulated using MATLAB and Simulink. The switching frequency used is in the range of 2.5 kHz to 12.5 kHz and the largest capacitor utilized does not exceed 102.3µF. while for voltage source inverter active power(VSI) filter the switching frequency is 20kHz and the largest DC link capacitor does not exceed 4700µF. Moreover, the thesis compares between the FFT and ANN techniques, which shows the superiority of the ANN technique for reference current generation of the proposed active power filter (DCDS). The switching pattern techniques are surveyed and the hysteresis current control (HCC) was used to generate the switching signal for the two filters. In simulation both filters DCDS and VSI filter were simulated with three different types of loads: inductive, capacitor and mixed load and their results were compared.