Transient Whole Process Analysis And Current Limiting Resistance Optimization Research Of Doubly-Fed Induction Generator Under High Voltage Ride Through

With the increasing grid-connected capacity of wind power,the impact of the safe and stable operation of the Doubly-Fed Induction Generator(DFIG)on the system can not be ignored.Since the DFIG particularly sensitive to grid voltage disturbances,and it is difficult to achieve fault ride through operation.At present,the low voltage ride-through technology when the grid voltage drops is relatively mature,but the High Voltage Ride-Through(HVRT)technology when the grid voltage rises has not received enough attention;With the continuous improvement of wind farm related grid-connected guides,HVRT capability will become an inevitable requirement of wind farms;in addition,the difficulty of high-voltage ride-through needs to cope with both transient and steady-state effects.Therefore,it is important to study the high voltage ride through transient characteristics and control strategies of DFIG.The main research work of this paper is as follows:(1)Establish the mathematical model of DFIG in two-phase stationary coordinate system,and analyze the whole process of stator flux transient of DFIG under the symmetry swell fault and the asymmetrical swell fault of the grid.The theoretical derivation of the whole process of the stator flux transient after the recovery of different fault duration is derived,and the factors affecting the transient characteristics of the stator flux are analyzed in detail.(2)In view of the fact that most of the existing literature only considers the dynamic change of the stator flux linkage in the rotor voltage equation of the current inner loop,but ignores its influence on the power outer loop,and proposes an improvement of the influence of the stator flux linkage change on the power decoupling.For the "demagnetization" control,not only the magnetic chain is required to be accurately observed,but also the phase sequence needs to be separated,and a reverse current tracking control strategy is proposed.(3)The accurate analysis of the rotor current in the grid voltage fault is related to the realization of fault traversal and the analysis of fault characteristics.Based on the analysis of DFIG electromagnetic transient characteristics,the expression of rotor current from the occurrence of grid voltage swell fault to the full-time resection is deduced,and the traditional current limiting resistor setting method is optimized.