Doubly-fed Wind Power Generation System Of Lvrt Technology Research

With the growing energy shortage and environmental problems, as the bestrenewable energy of high development and commercialization prospects in theworld, wind power is more and more favored. In recent years, doubly fedinduction generators (DFIG) gradually become a hotspot in the field of windpower due to its converter in small size, light weight, and low loss.Mathematical models of doubly fed induction generators are analyzed in a gridasymmetric fault. On the basis of joint optimization control on the network sideand rotor side converter，the low voltage ride through of double fed inductiongenerators is realized. The main contents are as follows:1. The mathematical models of doubly fed induction generators are createdin the three-phase static coordinate system and the two-phase synchronousrotating coordinate system. The grid voltage oriented vector control technologyis used for the decoupling of active and reactive power of the network sideconverter. The stator flux oriented vector control strategy is used for achievingthe output reactive power control and maximum power point tracking of rotorside converter. And electrical quantities of the grid two-phase groundingshort-circuit fault are analyzed in the traditional control strategy.2. Voltage vectors in the grid voltage asymmetric fault are analyzed inforward and reverse synchronous rotating coordinate system. And thesymmetrical components method is used for the dynamic modeling of thenetwork side converter and the rotor side converter in asymmetric fault.Expressions of instantaneous active and reactive power are derived, which laysthe foundation for eliminating the twice ripple component of the asymmetriccontrol strategy.3. Due to the limited capacity of the single DFIG converter, thus the jointcontrol of network side and rotor side converter is adopted to realize low voltageride through in grid asymmetric fault, in which four different control objectives are set. On the grounds of simulation models established in Matlab/simlink, theeffectiveness of the control strategy is validated.