Mega penetration of photovoltaic power generations (PV) will be introduced in future electric power systems, coping with environmental problems such as global warming and energy exhaustion. The authors have pointed out that difficulties will arise in performing the N-1 security standard if increase in uncertainties cannot be avoided caused by the PV penetration. Then, we have proposed a new concept of “robust power system security” together with the several conditions to be satisfied to guarantee the N-1 security standard under the uncertainties. In this paper, (1) a model of uncertainties by PV generation is proposed based on the robust power system security; a method for proper parameter selection is also provided. Then, (2) the influence on the stability by the PV and load disconnection from the power system is studied through simulation using the model system; (3) the effect of PV's fault ride through (FRT) on the stability is investigated as well as dynamic voltage support (DVS). Finally, it is shown that (4) complicated burden tasks will be considerably increased in power system operation planning and real time operation in the future circumstance by the mega penetration of PV.