Determination Method of Volt-var Curve Settings for Smart Inverters to Decrease SVR Tap Operations caused by PV Output Fluctuations and Minimize Distribution Losses

Due to the expansion of the photovoltaic (PV) power generation expected in the future, voltage fluctuations that occur locally in the distribution system are regarded as a problem. As one method of the suppressing this voltage fluctuations, Volt-var function of the smart inverter, that enables more flexible voltage control by reactive power output, is expected. The smart inverter not only just outputs photovoltaic power, but also has grid support functions that helps improve the stability of the grid. Considering new application of Volt-var control by smart inverter, it is necessary to construct a control system that sets appropriate control parameters according to the situation of the distribution line to which it is applied. The motivation of this research is to optimize the voltage control effect when the smart inverter is applied to distribution system with large amount of PV. Volt-var control behavior is defined by the curve point setting. It seems that the Volt-var curve setting could affect the behavior of tap changer control, and the reactive power output of the Volt-var control changes depending on the tap position. In this study, we propose a method for determining the Volt-var control parameters in consideration of the voltage control sharing with the tap changer control. And the effect of the proposed Volt-var control method is quantitatively evaluated by numerical simulation. © 2021 The Institute of Electrical Engineers of Japan.