Design Of AC-excitation Controlling System For Wind Turbines With DFIG

With the increasing depletion of conventional fossil energy sources, in recent years, wind power as a new green energy, it has enjoyed rapid development, which VSCF-DFIG wind power technology for its excellent features, become mainstream technology. In this unit, the AC excitation system is the key part to have the whole unit achieve outstanding performance. This paper focus on controlling of the AC excitation system for VSCF-DFIG wind power. Main contents and research results of this paper are described as below:This paper analyzed the basic working principle of DFIG, discussed the two kinds of generating state:super-synchronous and sub-synchronous. Established the dynamic model of DFIG in the three-phase stationary coordinate system(A-B-C), taking rotating magnetic field is equivalent and the power remains constant as the principle of coordinate transformation, transformed it to a two-phase D-Q synchronous rotating reference frame. On this basis, the research focuses on the DFIG stator flux oriented vector control (FOC) strategy.According to the requirements of VSCF-DFIG wind power system on the AC excitation, the two-level voltage source back-to-back PWM converter can be used for DFIG which has the most exciting advantages. The PWM converter operating principle, topology is described; its mathematical model based on switch function is established. And in accordance with the principle of constant power the two-phase D-Q rotating coordinate system is transformed from three-phase stationary system. Then focuses on grid converter voltage oriented vector controlling strategy research in network side.Constructed a 15K W DFIG AC excitation control system platform for experiments, designed the converter main circuit using IGBT power devices, created the drive and protection circuit based-on PC923 and PC929 chip, finished detection circuit design for the whole system parameters; Took TMS320F2812 DSP from TI company as controller, done the two-chip inverter control system and its peripheral circuit.Designed software controlling AC excitation system, based on TI DSP standard subroutine library. Modular designed software, easy to be modified and transplanted, achieved the SVPWM vector control strategy, PI controller, serial communication network, etc. Combined with theoretical analysis, carried out laboratory simulations of AC excitation, when the voltage in the grid under normal circumstances. Initially validated that DSP controlled the back-to-back PWM as AC excitation system for the DFIG has fine features, this research got a practical valued conclusion.