| Customers require reliable Power Quality (PQ) for safe operation of their equipment and home appliances. In industry, inconsistent PQ can manifest itself as a production shutdown due to malfunction or even damage of equipment. Improving PQ has attracted a great deal of attention since the beginning of the 1990's in order to reduce the revenue loss.; The objective of this thesis is to design an effective and generalized mitigating control strategy for the most common voltage related PQ problems, such as voltage harmonics, voltage unbalance, voltage sags and swells, and voltage flicker. Therefore, the focus of this thesis is on Voltage Quality (VQ). The proposed mitigating strategy depends on detecting the distorted voltage signals, tracking and extracting the voltage disturbance signals, and finally mitigating these problems by selecting an appropriate switching strategy to operate series and parallel mitigating devices.; In the detection and tracking stage, the Adaptive Perceptron (AP), the Linear Digital Filter (LDF), a simplified frequency tracking technique, and the Extended Kalman Filter (EKF) are introduced and modified to extract the system disturbances. The proposed techniques have the advantage of mathematical simplicity. In addition, they are accurate in instantaneous tracking of the distorted waveforms, and extracting the disturbance within a half cycle. The simulation results for the proposed mitigating control strategy are obtained from PSCAD/EMTDC and MATLAB. All the proposed techniques are coordinated to form a generalized mitigating control strategy.; In the mitigating stage, a power converter receives control signals from the control strategy to mitigate the voltage disturbances. For the series and parallel mitigating devices, the proposed topology is a modular approach. Each module is one single-phase voltage source for each phase.; Also, the thesis propounds novel methods to minimize the energy that is required for mitigating the common VQ problems. These methods are verified by the simulation results obtained from PSCAD/EMTDC and MATLAB.; The proposed mitigating strategy is experimentally verified by using a prototype of a single-phase distribution feeder with linear and non-linear loads. The series and parallel mitigating devices were built in the lab by using power MOSFETs and power IGBTs to mitigate the voltage harmonics with different Total Harmonic Distortion (THD), different levels of voltage sags and swells, and different types of voltage flicker. The control strategy is realized by using digital and analog circuits.; Finally, the simulation and experimental results are compared to verify the outcome of the proposed mitigating strategy and disturbance extraction techniques and to test the performance of the mitigating devices. The outcome of this comparison shows an excellent agreement between the experimental and simulation results, which confirms the effectiveness and generalization of the proposed mitigating control strategy. |
