Smoothing Effect and Energy Capacity in Photovoltaic Power Smoothing Control Using Spline Function

In a photovoltaic generation system, the output power fluctuates with the weather. Hence, the power quality may deteriorate when a large number of photovoltaic generation systems are connected to the power grid. Therefore, power smoothing control methods in the photovoltaic system with an energy storage system have been proposed. This paper evaluates the relationship between the power smoothing effect and the rated capacity of the energy storage system for the power smoothing control method using the spline function which is proposed by the same authors earlier. Validation uses data of a 153-day period measured in a photovoltaic power generation system with the rated power of 1.75 MW. The smoothing effect was 51.8% using the proposed method when the lower frequency for the target frequency band of the short-term fluctuation components of the power flowing to the power grid was 1/1,200 Hz, while the rated capacity of the energy storage system was 106 kWh without energy control. Although the smoothing effect decreased, the rated capacity of the storage system could be greatly reduced by energy control.