Smart Inverters' Functionalities and their Impacts on Distribution Feeders at High Photovoltaic Penetration

Abstract

There has been a consistent rise in grid-connected photovoltaic (PV) systems. Several studies have reported the impacts of this increase on the distribution networks such as reverse power flow, voltage fluctuations, possible increase in system losses amongst others. With this rise in PV penetration level, it becomes necessary for grid tied smart inverters (SI) to be allowed to participate in feeder voltage regulation. Till date, no comprehensive technical review and analysis has been done on the impact and interaction of existing and proposed SI settings on the existing legacy voltage control devices. This paper presents a novel technical review and analysis of some voltage regulation settings of SIs and their impacts on distribution feeders including their interaction with legacy devices such as capacitors, on/off Load Tap Changers, their impact on the feeder losses, harmonic effects and economic impacts (expressed as the device cost factor) and circuit impact index (CII). The analysis of these functionalities is done using the standard IEEE 8500 distribution feeder (modeled using OpenDSS and MATLAB), integrated with six PVs (based on real PV parameters and data), and strategically located with actual irradiance and temperature profile from a 1.4MW PV plant located at FIU. These PV locations were carefully selected to allow for detailed impact studies. The results show how the various SI functions impact the reactive power injection and switching of the capacitor banks, the voltage regulator switching, the losses in the feeder, the harmonic and the CII. The Volt-Watt with rise/fall rate-of-change limiting setting showed the least impact in terms of the CII, voltage regulator tapping and capacitor switching but with high amount of losses compared to other SI functions.