| Doubly fed induction generator(DFIG)is rapidly becoming the leading type of wind power generation in China due to its low price,mature production technology and simple structure.However,the topological structure of DFIG also makes the grid voltage fault have a great impact on it.In recent years,experts have made great breakthrough in the research of low voltage ride through(LVRT)technology of DFIG,and the control technology is relatively mature.At the same time,high voltage ride through(HVRT)of DFIG has gradually become a research hotpot in recent years.In addition,the traditional research only involves the fault ride through problem of conventional DFIG,and the research on HVRT of DFIG with stator winding inter turn short circuit(SWITSC)fault is less mentioned;In order to solve the difficulty of tuning the parameters and other variables of the simulation controller,an improved gray wolf algorithm is proposed to calculate the correlation.Firstly,the mathematical model of DFIG in three-phase static coordinate system is given,and then the mathematical model of DFIG in two-phase rotating coordinate system is obtained through coordinate transformation;At the same time,the mathematical models of DFIG rotor side and grid side converters are given;According to the mathematical model,the simulation model of DFIG is built by using Matlab/Simulink simulation platform;According to the superposition principle,the transient characteristics(steady-state response and dynamic response)of DFIG are analyzed in detail.The fault response of DFIG is equivalent to the dynamic response of DFIG by adding a voltage surge component to the original steady-state response;Similarly,according to the superposition principle,the rotor current expression of DFIG during HVRT is derived,and the accuracy ofI_r expression is verified.To improve the control strategy of rotor side converter,a current tracking control strategy is proposed to realize the HVRT of DFIG.The structure of this control strategy is simple and the effect is remarkable,which overcomes the problem that the traditional"de-excitation"control cannot be controlled toT_e effectively.In addition,based on the analysis of transient characteristics of DFIG,it is concluded that the rotor side of DFIGR_r increases with theξincrease of DFIG,and the largerξthe DFIG is,the more obvious the effect of restraining DFIG oscillation is,and the additional impedance control is proposed.For the improvement of the control strategy of the grid side converter,based on the analysis of the mathematical model of DVR,the voltage compensation control strategy of DVR before surge is proposed,which improves the transient characteristics of DFIG and realizes the fault ride through.In order to realize the HVRT of DFIG better,the additional impedance control strategy and the voltage compensation control strategy of dynamic voltage restorer(DVR)are combined to realize the high voltage ride through fault of DFIG.DFIG can work with SWITSC fault.The mathematical model of DFIG with SWITSC fault is given.On this basis,the simulation model of DFIG with SWITSC fault is built.The dynamic response performance of the DFIG with SWITSC and the normal DFIG is compared,and the simulation verifies the performance of the combined control strategy of additional impedance control and DVR control strategy on the DFIG with SWITSC.Aiming at the difficulty of tuning the parameters of simulation controller and other variables,an improved gray wolf optimization algorithm is proposed,which provides a new idea for quickly finding the relevant variables.There are 30 figures,9 tables and 64 references in this thesis. |
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