Moghaddam, Mohammad Jafar Hadidian (2021) Power Quality Improvement in the Distribution Network using Optimization of the Hybrid Distributed Generation System. PhD thesis, Victoria University.

Abstract

Due to increase in population growth and industrialization process, energy requirements have multiplied. Because of gradual depletion of energy sources resulting from fossil fuels as well as low efficiency and environmental concerns arising from these sources, much attention has been paid to the use of renewable energy sources. The use of resources such as wind and sun that are nominated as clean energy sources has been examined. However, due to the uncertainty of solar radiation and wind speed, their energy production has an unpredictable nature. Therefore, renewable energy resources are used appropriately to form a hybrid system consisting of wind turbines and solar arrays that meets network requirements. A group of power generation systems that are supplied from different sources are known as Hybrid Distributed Generation (HDG). In other words, they work together as complementary group and connect to the distribution network in both the stand-alone and grid-connected ways to supply the load. The presence of DGs in the distribution network has advantages and disadvantages. Voltage support, power loss reduction and reliability improvement are some of the benefits of DGs if their site and size are properly selected in the distribution network. On the other hand, Power Quality (PQ) problem can be defined as any power problem manifested in voltage, current or frequency deviations that fails to meet the requirements of customer equipment. Poor PQ causes tremendous financial losses in deregulated power systems. Today’s electric power systems are connected to many non-linear loads. One PQ problem is harmonic distortion, which is the result of the presence of non-linear loads in the network. Harmonics can cause improper performance in protective equipment, such as relays and fuses. Furthermore, due to the generated heat by the harmonic currents, many consumers and distribution companies are sometimes forced to decrease the amount of output from the transformers. Determination of appropriate location and optimal size of HDG in the distribution network is a main challenge in the changing regulatory and economic scenarios. In this thesis, design and placement of a HDG based on photovoltaic (PV) panel, wind turbines and battery storage (PVWTBAHDG) is proposed to improve the loss reduction and PQ in an unbalanced 33-bus radial distribution network. Further, in this research, improvement of voltage sag, voltage swell, Total Harmonic Distortion (THD) and voltage unbalance are considered as PQ indexes. The HDG system is designed to supply a residential load and it is able to inject its excess power into the distribution network. The PVWTBAHDG system has been designed to minimize the energy generation costs including initial investment costs and maintenance and operation costs. Therefore, the site and size of PVWTBAHDG components are optimally determined considering the total objective function of the system which includes decreasing the losses, reducing the cost of energy generation by the HDG and improving the power quality indexes. In this research, based on the social and intelligent behavior of crows, a hybrid meta-heuristic method named Crow Search Algorithm-Differential Evolution (HCSADE) is proposed to determine the location and size of PVWTBAHDG components in the network. In order to avoid the Crow Search Algorithm (CSA) from trapping in the local optima and increase the convergence speed of the algorithm, the crossover and mutation operators of the Differential Evolution (DE) method are employed to improve the CSA performance. Simulations have been implemented in several scenarios of single and multi-objective optimizations. Multi-objective results are obtained by compromising the results of single- objective optimization. The simulation results show that the HCSADE method presents a desirable performance in optimal sizing and siting the PVWTBAHDG in the network and also causes loss reduction and PQ improvement. The superiority of the HCSADE is confirmed in comparison with CSA and DE methods in terms of better objective function. Moreover, the results prove that increasing the number of PVWTBAHDG causes further reduction in the PQ indices and losses.

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