Utilizing Spare Inverter Capacity for Distribution Grid Voltage Support: An Adaptive Control Scheme

Grid-tie inverters for connecting renewables to the grid are generally rated based on the peak power rating of the sources feeding them but, owing to the inherent variability and uncontrollability of most renewable energy sources, much of the inverter capacity is not used the majority of the time. This results in significant spare converter capacity that may be used for other purposes. This paper proposes an adaptive, plug-and-play means of utilizing this unused capacity for controlling reactive power, with the aim of providing grid voltage support on distribution networks, where reactive power control has traditionally not been economical. The method described uses an active impedance estimation algorithm to determine the gains required for reactive power controllers without requiring manual tuning of large numbers of converters. Both simulated and experimental results validating the techniques described are provided.