Research On The Stability Analysis Of DFIG Under Weak Grid With Symmetrical Fault

The increasing installed capacity of wind driving makes wind electricity more important in the electrical power system.There is higher grid-connected requirement,required the wind power plant must has the LVRT(Low Voltage Ride Through)ability.DFIG(Double Fed Induction Generator)is one of the most common wind drive.The stator of DFIG is directly connected with grid,and be easy influenced by grid.DFIG is more difficultly to ride through the low voltage.And more wind power plants have been built at remote area for stronger wind energy.The line impedance can't be ignored any more.DFIG is working under weak grid.Phase-locked loop and rotor side current loop influenced each other,if there is no suitable parameters,the DFIG system maybe instable.Phase-locked loop and rotor side current loop is a complex high order nonlinear system.The large disturbance stability can't be analyzed by small-signal analysis method.Singular perturbation theory is an analysis method of nonlinear system with small parameter,and rotor side current loop belong to this kind of system.According to singular perturbation theory,one high order system could be composed by two lower order system,and analyze their several stability.The DIFG model under weak grid could be made.Calculating the stability criterion,discuss the influence of grid voltage,line impedance,phase-lock loop and rotor current loop proportionality coefficient,rotor current instruction to the system stability criterion.Get neutrality system parameter.Analyze the influence of different rotor control strategy to system stability under LVRT process.Make 1.5MW simulation model in Matlab/Simulink and 2.5k W experimental platform to prove the correctness of neutrality system parameter..