Reactive-power control of photovoltaic inverters for mitigation of short-term distribution-system voltage variability

The output power variability of intermittent renewable sources can cause significant fluctuations in distribution system voltages. A local linear controller that exploits the capability of a photovoltaic inverter to provide both real and reactive power is described. This controller substitutes reactive power for real power when fluctuations in the output of the photovoltaic source are experienced. In this way, the inverter can help mitigate distribution system voltage fluctuations. The local linear controller has a control parameter called the substitution rate, and several methods of calculating this control parameter are described, including sensitivity minimization and violation optimization methods, which can be applied on a local or global basis and on a per-phase or phase-average basis. This controller is examined using an example distribution system, and it is found that the controller is effective at mitigating voltage violations. Furthermore, comparisons between the alternative methods of selecting the substitution rate are performed.