Voltage Regulation for Distribution Systems with Uneven PV Integration in Different Feeders

On-Load Tap-Changer (OLTC) transformer can successfully control the voltage for one feeder through adjusting its tap position. However, in real life application, the OLTC transformer installed in the zone substation may have to regulate voltage for several feeders at the same time. Considering uneven photovoltaic (PV) integration in different feeders, one feeder may experience reverse power flow caused by PV power, while another feeder may have to support heavy load. As a result, large voltage difference between feeders will occur. In such situations, the OLTC transformer may fail to control voltages of all feeders within the allowable range no matter how to adjust its tap position. In this paper, capacitor banks (CBs) installed in different feeders are used to reduce voltage difference between feeders. An innovative method of coordinating CBs and OLTC tap action is proposed. As long as voltage difference among feeders is controlled within a low value, OLTC transformer can successfully manage system voltage as it was designed. The effectiveness of the proposed method is verified through case studies.