Experimental Research On Excitation Controller Of Variable-speed Constant-frequency Doubly-fed Generator

The wind power generation as one of the renewable energy with large-scale commercial development value in the aspect of technology, not only reduces environmental pollution but also reforms energy structs, improves energy safety level. It is the integral part of development strategy of sustainable energy in many countries around the world.AC excited doubly-fed wind power generation system is a new and advanced power generation technique, the stator of generator is connected with electric network directly, by adjusting the amplitude, frequency, phase of the rotor excitation voltage, generator can run at the state of variable-speed constant-frequency(VSCF), and can be independently adjusted to output active power and reactive power, to achieve maximum wind power capture. Because the converter is located at rotor side, only deals with slip power in double direction, so it is low cost, small cubage and light weight. The rotor excitation controller of VSCF AC excited doubly-fed generation system is taked as the research subject, the winding asynchronous motor is adopted as the doubly-fed generator, the voltage-typed double-PWM convertor is used as the excitation source of generator, and the wind turbine is simulated by the separately excited DC motor. These constitute the wind power generation experimental system.Firstly, the development situation of the wind power generation industry and technology at home and abroad is summarized, it′s urgent to improve and spread the wind power generation technology in our country. The advantages of VSCF generation technology, some realizing forms of VSCF and the basic operation principle of doubly-fed induction-generator(DFIG) at the state of VSCF are introduced.Secondly, the dynamic mathematical model of DFIG and the changing model at different reference frames are analysed. The principle of achieving power decoupling control based on the stator flux field oriented vector control strategy is analysed as the priority. According to the principle, power and current double closed-loop PI regulators are designed. The vector control principle of voltage Space Vector Pulse Width Modulation(SVPWM) is illustrated detailedly and the hardware method with DSP of SVPWM which for power decoupling control establishes base is introduced.The function of hardware circuits which compose the experimental system are showed, hardware circuit schematic are gived at the same time. In the aspect of software designing, the main program and timer interrupt subprogram as well as module subprograms are designed, the module algorithms are explained detailedly. The circuit of zero-crossing detect is designed, the measuring method of initial phase is introduced detailedly, the initial phase of rotor is measured by experiment. According to the problem that rotor measured currents have many harmonics and serious interference, the plan of using Finite Impulse Response (FIR) filter to act as software filter is shaped, the method by window function to design FIR filter is showed, the FIR filter parameter is designed with the software Matlab, subsequently the program of FIR filter is writed. For finishing the communication between the double DSPs, the communication program is writed based on Multichannel Buffered Serial Port(McBSP), and the program is debugged on single DSP.Finally, software is debugged and PI parameters are adjusted time after time on the experimental panel, the experiment data are registered. The experimental results testify that the academic study is correct and viable, the system realizes the double closed-loop power decoupling control of VSCF doubly-fed generator.