Under The Condition Of Power Grid Failure Doubly-fed Induction Motor Excitation Control Technology Research

With the deepening and evolution of contradiction between the energy demands of the global economic and social development and the world traditional energy supply, wind power and other renewable energy have been quickly promoted and widely used. Wind power generation system is on a large scale access to the main grid while its safe and reliable operation is directly related to the safe and reliable operation of the main grid. The doubly-fed induction generator based system is one of the most important architecture of the wind power generation system. Rotor excitation make the doubly-fed induction generator variable speed constant frequency operation and pass slip power between doubly-fed induction generator and grid.The thesis analyze the control structure and operation characteristics of doubly-fed induction generator system based on grid voltage orientation. Rotor excitation control features and variable speed constant frequency operation mechanism are verified and analyzed through simulation and experiment. A simplified model containing the grid voltage dynamic information is deduced from the fifth order model of doubly-fed induction generator. The thesis analyze the cause of cash current and oscillation electromagnetic torque during grid voltage dips. Considering grid voltage dip as disturbance, the thesis proposed a rotor damping current control based on feed-forward structure. It utilize the rotor compensation magnetic potential produced by rotor damping current to cancel cash current in stator and rotor side caused by natural component of stator and rotor magnetic potential. To assist the grid voltage recovering, a novel rotor current coordinated control is proposed to balance output of reactive component and damping component in rotor current. The control structure and algorithm is verified by simulation.