Research On Control Strategy And Low Voltage Ride Through Of Doubly-fed Wind-driven Generator

Doubly-fed Induction Generator (DFIG) wind power generation system became a significant research field in wind-force domain on account of its several advantages including less converter rating, high efficiency as well as flexible and controllable power control ability. This dissertation studied Doubly-fed Induction Generator (DFIG) wind power generation system and mainly carried out theoretical analysis of the control strategies for both generator-side converter and grid-side converter as well as Low Voltage Ride Through (LVRT) technique. Then this dissertation validated the theories by simulation and experiments.Firstly, the operating principle of DFIG wind power generation system was analyzed and the control method was studied on the base of DFIG mathematic model. Moreover, the vector control strategy based on stator flux oriented or stator voltage oriented was emphatically studied. This dissertation also applied novel Proportion Resonant Controller in voltage oriented vector control system and achieved better steady state performance and dynamic state performance.Then, this dissertation studied the mathematical model and control strategy of grid-side converter. The mathematical model and control strategy of PWM rectifier was built, and grid voltage oriented vector control strategy was mainly researched on the basis of the model. Moreover, the PI regulator and Space Vector Pulse Width Modulation (SVPWM) was introduced in detail. After that, this dissertation validated the control method as well as its steady state performance and dynamic performance of grid-side converter by simulation.For the purpose of guaranteeing that DFIG wind power generation system will not disconnected from the grid while the grid voltage drops, LVRT technique was introduced. This paper analyzed the response performance of DFIG wind power generation system, and determined a useful and feasible control scheme aimed at 1.5MW DFIG wind power generation system. Then, this paper compared and analyzed all kinds of low voltage simulators and presented simulation program based on the rising of stator voltage. This dissertation also simulated the control strategy.In order to validate the theoretical analysis and simulation, this dissertation experimented control strategy of generator-side and grid-side converter and LVRT scheme on 90kW DFIG wind power generation system platform. The experiments validated feasibility of control strategy of DFIG wind power generation system converters and LVRT scheme.