Dual-layer voltage and VAR control approach with active participation from distributed solar generations

Power distribution systems are desired to operate at their optimal control settings. These settings typically mean operation at low energy consumption and minimized distribution losses. Renewable energy resources can be very important for efficient operation of the distribution systems. However, when the number of renewables in the distribution system increases, the complexity of the control also increases. Intermittent renewable resources, particularly wind and solar, can cause significant fluctuations in distribution feeder voltages. This article presents a dual-layer control approach for finding the optimal feeder control settings and maintaining the feeder voltages within specified limits between the optimization intervals. The load-tap changer transformers, voltage regulator, capacitor banks, and smart inverters participate in the global control, while the smart inverters deal with the fast changing transients at the local control level. Thus, this control scheme will take full advantage of power-electronics-based smart inverters to reduce or eliminate fast transients, and also reduce the wear and tear of mechanical controllers. Evaluation studies are performed based on the IEEE 37 node radial test feeder under varying load and generation conditions. The results demonstrate that the proposed approach is promising for voltage and VAR control of distribution feeders with intermittent resources.