Aggregate Modeling of Distribution System with Multiple Smart Inverters

High penetration of renewable energy based distributed generators is a common goal for many electricity companies. While providing clean and cheap energy on the one hand, these active components create unprecedented problems in the grid. Arguably the most prominent one is causing unacceptable voltage rises due to power injection. Traditional solution is to cap the renewable energy generation. This turns into a double loss as the available energy is not captured and the installed equipment is not fully utilized. Introduction of smart inverters is aimed at solving these intertwined concepts. Impact of smart inverters on the distribution network operation has been recently reported in the literature. However, multiple smart inverter operation where several devices try to influence the power flow has not been thoroughly investigated. This paper focuses on analyzing the operation of several smart inverters that are running in Volt-Var mode and are connected to the same distribution feeder. Furthermore, considering the number of roof-top PVs in neighborhoods and the difficulty in simulating the individually, a simplification method is developed. In this fashion, multiple smart inverters operating in the same feeder are modeled in an aggregated way for easier calculation. Finally, simulation results are presented for analysis and validation.