Improving on-load tap changer voltage regulation process for power distribution networks with a high penetration of distributed generation

Abstract: The demand for electric power both globally and in South Africa has increased recently due to the increasing population and the expansion of industries, manufacturing and agricultural activities. Most of the power produced worldwide is generated using fossil fuels such as coal. This leads to undesirable consequences on the environment such as global warming and climate change. Therefore, alternatives to the fossil fuel power generation process such as renewable energy were introduced. Generators that are connected to the power distribution network are called distributed generators, and hence renewable energy sources that are connected to the power distribution network are also known as distributed generators. The connection of distributed generators into the existing power distribution network interferes with existing power distribution network voltage regulation devices leading to poor voltage regulation and hence undesirable voltage magnitudes within the power distribution network. This is because conventional power distribution network voltage regulation devices such as the on-load tap changer and step voltage regulators assume a unidirectional power flow in which power flows from the substation towards the electrical load; they also assume that the substation busbar will always have the highest voltage magnitude. Therefore, the reversed power flow that occurs when distributed generator output power exceeds the local electrical load will render these voltage regulation devices ineffective and hence voltage magnitudes will increase beyond acceptable limits. This dissertation will introduce a new control system that will improve voltage regulation in power distribution networks with a substantial amount of distributed generation connected. The proposed control system uses a unique algorithm that will enable the on-load tap changer to keep all voltage magnitudes within acceptable limits both in the absence and presence of distributed generation. The proposed control system will monitor voltage magnitudes of crucial locations on the power distribution network; the on-load tap changer will therefore keep all monitored voltage magnitudes within acceptable limits. The control system will further reduce power generated by the distributed generator when monitored voltage magnitudes cannot be maintained within acceptable limits and again increase power generation when the load on the power distribution network increases.M.Ing. (Electrical Engineering