Do Grid Support Functions have Negative Impacts on Smart Inverter’s On-board Islanding Detection?

Abstract

With the proliferation of inverter based Distributed Energy Resource (DER) deployments, especially with advanced grid support functions (GSFs), the risk of unintended islands has remained a significant safety concern among the distribution system operators. IEEE 1547 standard requires DER to detect an island, cease to energize the area electric power system (Area EPS) and trip within 2 second of the island formation. In addition, because of aggregate impact of high penetration of DERs on system stability, IEEE 1547-2018 revision mandated several GSFs, including abnormal voltage and frequency ride-through and voltage/frequency regulation support capabilities for all DERs. These grid support functions aim to maintain stability during grid-connected operation and island preventions aim to destabilize the network when the grid is not present. These apparently opposite objectives lead to the skepticism about island prevention effectiveness together with grid support from smart inverters. This paper investigates the apparent conflict in objectives and provides answer by revealing the unique relationships between frequency, voltage, active and reactive power in grid following inverter dominated islands and the fundamental differences in inverter’s control during grid-connected and islanded condition. It also explains why ride-through, volt-var, frequency-watt, and volt-watt functions are not expected to impact island detection performance by smart inverters.