With the rapid increase of the photovoltaic(PV)power penetration

it is essential to precisely consider the impacts of PV power on power system planning and operation. However

due to the uncertainty and volatility of PV generation

statistical approaches are required to describe its features. This paper quantitatively depicts the distribution of the time for PV power to continuously maintain a certain output status. Firstly

the output status of PV power is defined by the operation point and deviation range of PV power

then the duration time characteristic is proposed. It is indicated by numerical results based on field measured data of China and Germany that: there is an obvious ‘double peaks property' in PV power duration time distributions and it can be properly fitted by the mixture of inverse Gaussian and generalized extreme value probability density function. The ‘double peaks property' further reveals that under frequent disturbances of clouds

PV power will maintain the current output status for only a few minutes. Otherwise

PV generation can smoothly follow the regular changes of solar radiation and keep the current output status unchanged for hours. Research results of this paper can provide important references for the optimal choice of the measurement and control time interval in the PV generation dispatch

validation of the maximum output variability

and for design and selection of power equipment in transmission systems.