| The large-scale wind power into the power grid must have a significant impact to the stability of the grid Permanent magnet direct-drive synchronous wind turbine system has been widely applied for its unique advantages. Transmission shafting flexible will lead to a unit in power grid fault and recovery process of torque oscillation, on the stability of unit operation effect, so it is necessary to research and analysis it.First, the mathematical model of permanent magnet direct driving wind power system is established and the control strategy of the converter is researched. The control strategy of id=0is researched in the motor side PWM. By regulating the stator current of dq axis to realize speed regulation and the decoupling control of motor excitation and torque. The voltage directional control is used in the Power grid side PWM converter and the coupling control of active power and reactive power is realized. The2.5MW wind generator of permanent magnet direct driving simulation model is built. The model and the control strategy are verified.Based on the built simulation model, supposing that there is three phase fault. The influence of transmission system characters on transient performances of wind turbine are researched. The simulation results prove that the increase of Hw、Hg or the decrease of Hw/Hg will both made the vibration amplitude of active power and dc voltage increase and the stability is reduced. It is necessary to consider the influence of the flexibility characteristics of the torsional axis of the transmission system when the transient performance is researched. The equivalent spring stiffness coefficient is bigger and the transient stability of the system is smaller. The self damping of wind turbine、the self damping of generator and the mutual damping of them are all have a significant impact to the transient stability of the system. Especially the mutual damping is cannot oversight, it can improve the transient stability of the system. |
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