Power quality control algorithms for small scale power intergration systems

The electrical power system is a means of supplying energy that is intended to generate, transport and supply electricity to various kinds of loads that are connected to it. The electricity providers strive to supply their customers with steady and uninterrupted sinusoidal power as they function. Traditional power plants primarily rely on fossil fuels such as coal for their energy source. Because of the influence of global warming, air pollution is becoming a major concern in traditional coal-based power generation, and measures to reduce it have been implemented. South Africa is among the many African nations that have ratified these international agreements. Incorporating renewable energy sources is the sole method to establish an environmentally friendly power generation system. Integrating various energy resources at the distribution level is possible and helps to reduce transmission power losses. However, integration of renewable energy resources requires the use of advanced non-linear technological equipment which causes some technical problems. Amongst technical problems that may be faced is high penetration of solar Photovoltaic (PV) which results in voltage swell power quality issues whilst excessive connection of non-linear load results in current harmonics.The thesis examines the use of Custom Power Devices (CPDs) such as Dynamic Voltage Restorer (DVR), Distribution Static Compensator (DSTATCOM), and Unified Power Quality Conditioner (UPQC) for voltage and current-related power quality issues. The CPDs depend on the DC link voltage from the storage element used which is not always sufficient and the compensation of the power quality issues fail. The use of small-scale solar PV for the support of the DC-link storage element used in the CPDs is explored.A DVR has been proposed for the mitigation of voltage-related issues to ensure that the grid supplies power with voltage variation to sensitive loads. The load is protected from such and in the case where the DC link storage is not enough solar PV will support the DVR. However, this type of compensation has proved unable to deal with harmonics caused by the non-linear load connected to the system which meant another CPD has to be proposed for current related issues. A DSTATCOM is a device that can used for compensation of current-related power quality issues but also cannot deal with voltage power quality issues. A right shunt UPQC has been proposed as a combination of the two devices connected back-to-back through the DC link side for voltage and current multiple power quality issues. Optimisation of effective compensation for the CPDs depends on the proper selection of control algorithms for the gate switching of the Voltage Source Converters (VSCs) used. A control algorithm has been implemented considering the stated dynamic behaviours of the power system to ensure that the CPDs can restore the power quality required by the consumer and the utilities as regulated by IEEE standards. The modelling and simulation were performed on MATLAB Simulink simulation software.

电力系统作为一种供应能量的手段，旨在生成、传输并向连接至其上的各类负载供电。电力供应商致力于在其运作过程中向客户提供稳定且不间断的正弦波电力。传统的发电厂主要依赖化石燃料，如煤炭作为其能源来源。由于全球变暖的影响，空气污染已成为传统煤炭发电领域的主要关注点，并已实施减少其影响的措施。南非是众多签署这些国际协定的非洲国家之一。将可再生能源纳入电力系统是建立环保型发电系统的唯一途径。在分配层面整合多种能源资源是可行的，有助于降低输电损耗。然而，可再生能源资源的整合需要使用先进的非线性技术设备，这导致了一些技术问题。可能面临的技术问题包括太阳能光伏（PV）的高渗透率，导致电压波动，进而引发电力质量问题；以及非线性负载过多连接导致电流谐波。本论文探讨了用于电压和电流相关电力质量问题的定制电力设备（CPD）的使用，如动态电压恢复器（DVR）、配电静止补偿器（DSTATCOM）和统一电力质量调节器（UPQC）。CPD依赖于储能元件的直流链电压，而该电压并不总是足够，导致电力质量问题的补偿失败。探讨了使用小规模太阳能光伏来支持CPD中使用的直流链储能元件。为缓解与电压相关的问题，已提出一种DVR，以确保电网向敏感负载提供电压波动的电力。负载得以保护，在直流链储能不足的情况下，太阳能光伏将支持DVR。然而，这种补偿方式无法处理由系统连接的非线性负载引起的谐波，这意味着需要提出另一种CPD来解决与电流相关的问题。DSTATCOM是一种可用于补偿与电流相关电力质量问题的设备，但不能处理电压电力质量问题。一种正确的并联UPQC已被提出，作为通过直流链侧背对背连接的两个设备的组合，以解决电压和电流的多种电力质量问题。CPD的有效补偿优化取决于对电压源转换器（VSC）门控切换的控制算法的正确选择。为了确保CPD能够恢复消费者和公用事业所需的电力质量，符合IEEE标准的规定，已实施了一种考虑电力系统所述动态行为的控制算法。建模和仿真是在MATLAB Simulink仿真软件上进行的。