A voltage control strategy with NAS battery systems considering interconnection of distributed generations

Recent years, some distributed generations such as energy storage systems or renewable energy sources have been introduced in distribution systems, and the voltage violation problem has been at stake by the reverse power flows from the load to the generator. In this paper, we consider NAS (natrium sulfur = sodium sulfur) battery systems to be utilized for not only energy storage but also power system control, and propose a new voltage control strategy in order to provide the proper sending voltage at distribution substations. First, the current flows at each distribution feeder are individually measured, and the sending voltage is calculated by using V-I characteristics, which indicate the relationship between the sending voltage and the current flows at each distribution feeder. Next, active and reactive power outputs of the NAS battery system are determined by solving an optimal power flow calculation in order to realize the predetermined sending voltage. Numerical examinations have been carried out using a 52-bus example system model to verify the validity of the proposed method, and successful results have been obtained.