Distributed voltage control method using Volt-Var control curve of photovoltaic inverter for a smart power grid system

The integration of distributed generations (DGs) in the electric power grid introduces distribution voltage (DV) fluctuations. Load demand variations are another source of DV fluctuations. The DV needs to be maintained within five percent of its nominal value. Several approaches exist for controlling the DV e.g. transformer tap-changers (TPCs), capacitor banks (CBs), voltage regulators (VRs), and static VAR compensators (SVCs). However, these DV control methods require installation and maintenance of new equipment for the electric power utilities. In addition, these devices have a relatively long response time. Due to the increase of DG integration, the DV needs to react promptly. Distributed photovoltaic (PV) generation have been increasing rapidly. The smart PV inverter enables several strategies to control the DV. For example, the smart PV inverter can absorb and generate reactive power (Var) using the Volt-Var control strategy to regulate the DV. This paper shows an experimental study of the Volt-Var control method using a smart PV inverter. The Volt-Var control strategy was tested using a smart SMA PV inverter. When the DV drops, the smart PV inverter dispatches Var to increase the DV. On the other hand, when the DV is higher than its nominal value, the smart PV inverter absorbs Var to decrease the DV. The real-time analysis of the Volt-Var control method was investigated in the Maui Advanced Solar Initiative project.