Designing of Large Scale Grid Connected PV Systems

Abstract

Grid-connected PV systems are usually installed to increase power availability and at the same time enhancing the performance of the electricity network by reducing the power losses and improving the voltage profile of the network. However, this tend not to be always the case as these systems might impose several negative impacts on the network, especially if their level of penetration is high. These negative impacts include power and voltage fluctuation problems, harmonic distortion, malfunctioning of protective devices and overloading and under-loading of distribution feeders. The studying of the possible impacts of PV systems on the electricity network is currently becoming an important issue and is receiving a lot of attention from both researchers and power utilities. The main reason for the importance of this issue is that accurate evaluation of these impacts, as well as providing feasible solutions for the operational problems that might arise due to installing PV systems, is considered a major contribution towards facilitating the widespread use of grid connected PV systems. The primary objective of the research proposed in this thesis is to facilitate increasing the penetration levels of PV systems in the Zimbabwe utility grid. This can be achieved by properly designing PV systems and quantifying and analysing the impacts of installing large grid-connected photovoltaic systems on the performance of the electric network accurately. The cost effectiveness of these systems is also analysed. Solar PV technology for a particular site depends mainly on the annual solar intensity distribution for the site, variations in the efficiency of PV module technology with intensity, annual temperature distribution and module temperature coefficient, variations in the solar spectrum distribution and the rate at which the output power of the PV modules degrades with time. Electrical efficiency of the photovoltaic module depends on ambient temperature and the efficiency decreases as the temperature increases