Voltage stability is critical to a reliable utility grid. Solar photovoltaic (PV) arrays are being deployed at increasing rates around the world and can have negative impacts on the networks to which they are connected. There are similar concerns with distributed generation (DG) sources in general with variable prime movers such as wind. Recently, power electronics have opened up opportunities to mitigate some of these negative effects. Also, IEEE 1547a-2014 now allows DG resources to ride-through short-term voltage and frequency disturbances and also allows voltage regulation with agreement between the electric power system (EPS) and distributed resource (DR) operators. This project specifically looked at voltage fluctuations on the utility grid. Given the changes to IEEE 1547-2003 found in IEEE 1547a-2014, a minimum energy storage capacity relative to inverter power rating was calculated to provide voltage support through IEEE 1547a worst case voltage sag magnitudes and allowable ride-through time durations. An existing Simulink model was obtained and modified to: simulate voltage fluctuations from inductive loads on distribution networks, provide voltage fluctuation support through advanced inverter controls that may source or sink reactive power, and include energy storage in the form of supercapacitors to further analyze the voltage support capability. Three PV-Grid penetration scenarios of 10%, 20%, and 50% were simulated for comparison. The results show that while outputting maximum available real power of 1 per-unit, an inverter may still source or sink 0.46 per-unit reactive power without exceeding the long-term inverter current rating. This reactive power proved to provide limited continuous voltage support at all levels of increasing PV-Grid penetration. For the 10%, 20%, and 50% PV-Grid penetration cases, per-unit root-mean-square (RMS) voltages were increased by approximately 0.13-0.33%, 0.15-0.47%, and 0.34-0.63% respectively, for RMS voltage magnitudes of 0.928-0.968 per-unit. Including supercapacitors for energy storage showed similar results, except that voltage support capability increased when changes in PV output occurred and enabled the inverter to continue outputting near maximum real power rating while also providing voltage support through reactive power injection under changing solar irradiance levels.
