Flexible voltage control to support Distributed Generation in distribution networks

Increasing penetration of Distributed Generation (DG) in distribution networks significantly changes both the real and reactive power flows in the network and can create serious voltage control problems. Furthermore, traditional Automatic Voltage Control (AVC) schemes that can normally deal with the reverse power flows, are unable to cope with the voltage problems associated with the presence of DG under certain conditions. Several techniques have been deployed to improve distribution network voltage profiles in such cases, for instance network reinforcement or active voltage control with remote voltage sensing units. Another method that has been proposed and recently implemented is the SuperTAPP n+ relay scheme that is based on locally taken measurements at the substation level combined with a state estimation technique. Such an approach enables assessment of the voltage rise at the point of connection of DG and effective control of the voltage level at the substation. The first objective of this paper is to present the fundamental principles of innovative voltage control schemes for distribution networks with DG based on locally measured signals. Secondly the functionality of the most flexible scheme will be demonstrated via software simulation for a range of distribution network case studies based upon realistic EDF Energy network scenarios. Finally, the results from the modelling and analysis of the SuperTAPP n+ relay scheme and its feasible application will be discussed and detailed conclusions are presented.