A Study on Estimation Method of Reactive Power Control of DGs in Distribution Systems with a large amount of PVs

Abstract To solve the energy and environmental issues, it is expected that a large amount of Distributed Generators (DGs) such as renewable energy are introduced to power systems. In distribution systems with many DGs, the voltage maintenance becomes an important issue due to the reverse power flow. Although reactive power control of DG is effective for the voltage maintenance, the increase of distribution power loss may be caused by such a reactive power control. Additionally, the decrease of active power output of DG may be also required for the reactive power control when its reserve capacity is not sufficient. Thus, it is desired to reduce the amount of reactive power controlled by DGs. On the other hand, in general, distribution systems consist of High Voltage Systems (HVSs) and Low Voltage Systems (LVSs). Most voltage control equipments such as Load Ratio control Transformer (LRT) and Step Voltage Regulator (SVR) are included in HVSs, and DGs are introduced mainly in LVSs. To reduce the reactive power of DGs, the utilization of equipments in HVS is important. However, it is required for system operators to estimate the occurrence of reactive power control of DGs properly. Hence, we developed a new state estimation method of DGs by using sensor information supposing that existing section switchgears will be replaced with new ones that can measure voltage and current using their attached sensors.