When the intermittent renewable energies, such as wind generation or PV plant, generate more powers under the condition of the environmental influence, the tidal current of the distribution network will change and the voltage at the connected-grid point may exceed the safe limited range. In order to avoid the above phenomenon, it could be done to limit the output energy for these power generation systems. The control methods for the directly-driven permanent magnet (PM) wind generation system are studied, output power curves of the wind turbine are analyzed, control methods of the optimal wind-energy tracking or limiting power operation and end-stage control strategy of the system are designed. This makes wind generation system and PV generation system have the functions of MPPT or limiting power operation, and independent control of grid-connected active power and reactive power. At last, the simulation model of wind generation system is built, and the control strategy is verified by the simulation results.