Effectiveness of constant power factor control of mega-solar system for voltage regulation with long distribution line

When a large-scale photovoltaic system, such as a mega-solar system, is connected to a distribution system, voltage variations on the distribution line may be caused by the output fluctuation of the photovoltaic system. This paper reports the result examined by numerical analysis and an experiment using a real system about mitigating the voltage variation by applying the reactive power control based on constant power factor control of the PCS in a large-scale photovoltaic system. It is investigated that the loss change on a distribution line influences the results of the reactive power control, especially when the large-scale photovoltaic system is interconnected with a long distance from a substation. This paper reveals that it is possible to mitigate a voltage variation sufficiently with the distance of about 5km from a substation to the interconnection point, and this method can be applied in many cases under the condition.