Effect of reactive power control by photovoltaic power generation on short-term voltage stability

In this study, we investigate two countermeasures using inverters of photovoltaic (PV) power generation systems to avoid short-term voltage instability caused by sudden shutoff of the PV systems after a voltage sag. One of the countermeasures is the operation of the PV system at a leading power factor in the normal state, and the other is the dynamic reactive power control after the fault. First, these countermeasures are tested for a one-load infinite-bus system where we consider dynamic characteristics of an induction motor load. In the numerical example, a previously proposed analytical method is applied to discuss the effect of the countermeasure on the short-term voltage stability. Next, numerical examples are carried out for a five-machine five-load power system. The results show that these countermeasures can play a substantial role in preventing the voltage instability phenomena caused when a PV system is suddenly interrupted because of a fault.