Experimental Distribution Circuit Voltage Regulation using DER Power Factor, Volt-Var, and Extremum Seeking Control Methods

With the rapidly increasing number of distributed energy resources (DER) on electric grids worldwide, there is a growing need to have these devices provide grid services and contribute to voltage and frequency regulation. PV inverters and other reactive-power capable DER have the capability to minimize distribution losses and provide voltage regulation with grid-support functions such as volt-var, volt-watt, and fixed power factor. DER reactive power function settings for specific distribution topologies have been widely studied for centralized (fixed reactive power, power factor) and decentralized (volt-var, volt-watt) control modes. However, optimal selection of the DER operating mode and settings depends on a priori knowledge of system topology, DER sizes and locations, or renewable energy power generation or forecasts. In this paper, we experimentally evaluate an approach for optimal reactive power compensation that does not rely on power system information. Specifically, we study the ability of Extremum Seeking (ES) control—a decentralized, model-free control strategy—to maintain voltage limits in a laboratory environment. The speed and performance of the ES control algorithm is compared to a smart inverter volt-var function for reactive power compensation utilizing local system measurements. Index Terms — voltage regulation, DER control, volt-var, fixed power factor, extremum seeking control.