An Average Voltage Approach to Control Energy Storage Device and Tap Changing Transformers Under High Distributed Generation

The South African power distribution network is characterized by long power distribution lines with low short circuit capacity, and when distributed generation is introduced to these lines, voltage magnitudes are severely impacted. The existing voltage regulation methods of the on-load tap changer and step voltage regulator cannot successfully regulate voltage in long distribution lines with distributed generation since their control philosophy was designed for networks without distributed generation. Therefore, a dynamic system is proposed in this paper that coordinates the on-load tap changer, step voltage regulator, distributed generators, and the battery energy storage system to control voltage in long distribution lines with distributed generation. Their coordination will be based on response time and robustness. Unlike the conventional method, the proposed novel system will calculate a reference voltage that the on-load tap changer and the step voltage regulator must follow, based on the real time average voltage of the section of the network they each regulate. The system will also control the charging and discharging of a battery energy storage system based on the point of connection voltage and the average voltage of the feeder which it is connected to. Reactive power from distributed generators will also be used to enhance voltage regulation and refine the network power factor. When voltage magnitudes cannot be successfully brought within acceptable range, the proposed scheme will decrease the active power produced by distributed generators. The proposed system is examined on a South African 22kV network built in Matlab/Simulink.