Distribution network performance improvement using load compensation

Ojo, Alaba

Distribution network performance improvement using load compensation

Thesis / Dissertation

2023

Abstract

The phenomenal growth in electricity demand due to population growth, industrialization, and the inadequacy of generation, transmission and distribution capacities have affected energy demand and the overall performance of the entire power system network as witnessed in South Africa since 2008. Even if additional power generating sources are provided, the power generated has to be transferred to the consumers through transmission and distribution networks which would also require additional investment for capacity expansion and this would amount to huge investment and burden for the utilities. To reduce this investment, an option could be, performance enhancement of the existing transmission and distribution system. Since the overall performance of power system networks depends on the loads connected to it, the distribution system is the backbone by which electricity supply is distributed to the customers, therefore, ensuring the economical operation of the distribution network within power quality standards is imperative. The presence of substantial single-phase loads, and large industrial loads such as arc welding, electric furnace, lightings contribute to the system unbalance and this may lead to the pollution of the supply voltages and excessive neutral current in three-phase four-wire networks. In addition, in the recent years, the use of power electronic-based devices/equipment in both industrial, commercial and residential sectors due to advancements in technology and the need for energy efficiency measures has increased the power quality problem. Such loads include Adjustable speed drives (ASD), High voltage Direct current (HVDC) system, traction systems, electric arc furnace, flexible AC transmission systems (FACTS), heating, ventilation and Air conditioning (HVAC) and loads with switch-mode power supplies. These power electronics-based devices draw nonsinusoidal currents which increased the reactive power demand from the source and other effects such as current and voltage distortion, errors in metering and malfunctioning of protective equipment, increased heating in conductors and power transformers, poor voltage regulation due in the supply's distribution system due to resonance condition. Therefore, at the beginning of this study, a power quality survey of commonly used nonlinear loads and a typical commercial building has been conducted to evaluate the existing level of power quality issues in the distribution system. Various voltage and current waveforms of some of the commonly used loads and their harmonic spectrum have been recorded using a power quality analyser. In mitigating the above problems due to poor power quality, an effective load compensation is required to improve the performance of the system. This dissertation, therefore, investigates the power quality issues, causes, effects, monitoring and evaluation. It also proposes effective load compensation techniques for performance improvement of distribution network considering unbalance, poor power factor and harmonic distortion using passive and active components. An innovative load compensation model has been proposed and developed for a three-phase, four-wire system through simulations using MATLAB/Simulink. An analysis of the distribution network with and without load compensation shows an improved power factor of about 38% and an appreciable reduction in the kVA demand of the network while the current harmonic of the load is minimize to an acceptable standards. Based on the investigations reported in this dissertation, it may be concluded that various options for load compensations in the distribution system for improving the performance of distribution networks are successfully explored.

Keywords

Engineering

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