Distribution Grid Reliability Versus Regulation Market Efficiency: An Analysis Based on Micro-PMU Data

There is a growing interest among power system operators to encourage load resources to offer frequency regulation. Prior studies have evaluated the system-wide benefits of such load resource participation. However, the potential adverse impact of wide scale load resource participation on distribution system performance, in the transient time frame, is often overlooked. Our goal is to address this open problem. We focus on a scenario where load resources offer regulation down service. To obtain realistic results, a distribution feeder in Riverside, CA, USA, is considered, where distribution-level phasor measurement units are used to collect high resolution voltage and current data. We start by developing a novel data-driven approach to analyze transient load behaviors. Subsequently, we model the aggregate load transient profile, in form of a three-phase surge current profile, that could be induced on a distribution feeder once a group of loads responds to a regulation down event. The impact of delay, e.g., due to sensing, communications, and load response, is considered. Distribution grid reliability is analyzed by taking into account the characteristics of the main feeder's protection system as well as each lateral's protection system. Both momentary and permanent reliability indexes are calculated. Case studies suggest that it is possible to jeopardize distribution grid reliability if several regulation down load resources are on the same feeder. Depending on various factors with respect to load resources, distribution feeder, and regulation market, there may or may not exist ways to break the trade-off between distribution grid reliability and regulation market efficiency. The construction and analysis of the reliability-efficiency curves would be needed for each feeder.