Recently, introduction of the distributed power generation using renewable energy sources like photovoltaic (PV) and wind turbine (WT) generation is expanded. However, the output fluctuation and the unpredictability may have an impact on system frequency. In this paper, the methods to suppress the frequency fluctuation by the control of existing generators and PV are proposed. The probability of occurrence of the ramp rate violation and the available generating capacity shortage, and fuel cost are also checked. First, the method using pumped-storage generators is simulated. The operation time of pumped-storage generators is changed to prevent the surplus power. Second, the methods using thermal generators are simulated. Reserve margin is increased to prevent the deficit power, and 10-min spinning reserve (SR10) is increased to prevent the short-term power fluctuation. Finally, the method using PV is simulated. Suppression control of PV is simulated to prevent the surplus power.