Stability Analysis and Volt-Watt Control Setting Guideline for Distributed Energy Resources

Smart inverter grid support functions such as volt-var and volt-watt have the potential to alleviate over-voltage and voltage variation issues caused by high penetration of distributed energy resources, especially solar photovoltaic (PV), on the distribution circuit. However, because of the dynamic nature of volt-var and volt-watt control functions, they may cause voltage oscillation, especially when aggressive control settings are used. This paper investigates the stability of volt-watt control function through lab testing, analytical analysis, and simulation studies. Key factors affecting the stability of volt-watt control are identified. Moreover, a guideline to identify the volt-watt control setting range to avoid the voltage instability is developed and is verified via dynamic simulation on a simple test system.