Stability of distribution networks connected with distributed generation

Bibliography: pages 164-167.This thesis describes an investigation into the stability of distribution networks that are connected with distributed generators. Due to the restructuring of the electricity industry in the region as well as environmental concerns, distributed generation is bound to increase at a higher rate in the Southern African region in the near future. Southern Africa, like many other developing regions, is dominated by electrically weak distribution networks that have relatively high impedance lines. These networks suffer extreme voltage fluctuations when a transient disturbance occurs on the network. The distributed generators are connected onto distribution networks that were designed to operate without any generation, but were designed to receive power from the transmission networks. Once distributed generators are connected to distribution networks, a number of technical challenges are presented. One of the technical challenges includes investigating the stability of distribution networks connected with distributed generation. It would be beneficial to know what effect the connection of distributed generators onto distribution networks would have on the system stability. This is because if the connection of distributed generators onto distribution networks increases instability on the network, the quality of supply of that network would be degraded, therefore the connection of distributed generators must be limited or methods of improving the stability must be implemented. It is important to establish the measures that can be taken to make sure that the generators react in a stable manner when subjected to disturbances and to make sure that the local system stability is not compromised. The first objective of this thesis was to identify the types of generators that are likely to be connected to Southern African distribution networks and investigate their stability. The next objective was to design model distribution networks that would be utilised to highlight key stability issues that are raised when distributed generation is connected to distribution networks. The third objective was to conduct and analyse stability studies on model as well as existing Southern African distribution networks connected with distributed generation, including the assessment of the implications of potential instability such as on the quality of supply. The last objective was to identify various ways of improving the stability of distribution networks that are connected with distributed generation