A model for short-term fluctuation of total generation of multiple PV power stations

Recently, a large number of photovoltaic (PV) power stations has been connected to power systems. Penetration of PV power stations may give some impacts on balancing between supply and demand in power systems. The representative impact is frequency variation which is caused by short-term fluctuations in power outputs from PV stations. Therefore, its investigation and evaluation are important before further penetration of PV. Generally, frequency variation in power systems can be kept within an allowable level by load frequency control (LFC) which is executed by generation reserve scheduled in power system operation. Also, the performance of LFC can be validated in details by several time series simulations. From these backgrounds, this paper proposes two types of short-term fluctuation models in terms of power outputs of PV power stations. One is a standard deviation model which can be applied in the reserve scheduling and the other is a time series model based on the autoregressive (AR) model which can be utilized as an input data for time series simulation of LFC.