Research On Some Problems About Doubly Fed Wind Power Generation

With the consistent development of our economic, China has become the second economic entity in the world. The GDP of China is more than Japan. However, the need of power resource is more urgent than before, the green clean energy is required by our society. Therefore the wind power just can realize that.AC excited doubly-fed wind power generation is a relative advanced power generation technique, Comparing with synchronous motor, it can adjust the amplitude, frequency, phase of the rotor excitation voltage and run at the state of variable-speed constant frequency (VSCF).With the help of controlling the wind turbine, the maximum wind power can be achievable captured under the speed beyond the maximum wind velocity allowed, therefore the motor can put out the maximum wind power. The converter of double-fed wind power generation system is set on the side of the rotor side, the double direction flow power is slip power, and it is one part of the outputted power. As a result, the cost, bulk and weight of the power devices will be reduced. In this paper, the focus of the research is on the AC excited doubly-fed generation system on the state of variable-speed constant-frequency (VSCF).there are several aspects as follows:This paper not only introduces the overview development of wind power technology at home and abroad. It is of great urgency to improve the wind power technology in our nation, but also introduces advantages and principle of DFIG. Researchers can not study DFIG system because of lacking of wind turbine in laboratory. This paper uses DC motor to take place of wind turbine and illustrates principle of both wind turbine and DC motor. The possibility of using DC motor simulated wind turbine is analyzed. The ways to adjust the speed of DC motor are analyzed, and this paper chooses the circuit of Buck chopper. The simulation is set up in the software of MATLAB. The result of simulation can meet the requirement of experiment. Wind turbine will put out different power as the result of different speed of the impellers even at the same wind speed. The wind turbine will operate on the output of the maximum wind power rated state. Many methods to capture the maximum power of wind turbine are detailed introduced. This paper use the way of mountain climbing to seizure the maximum power. The software of mountain climbing in MATLAB is edited and simulated. The simulation can fulfill the purpose.This paper based on the simulation uses TMS320F2812 DSP controller conducted by TI Company of USA to control the signal of PWM (Pulse-Width Modulation), which is used to control the speed of DC motor in Buck chopper circuit. Hardware of DC motor simulating wind turbine including main controlling circuit, drive circuit, snubber circuit of power switching and protection circuit is detailed introduced and type of chip used in circuit is illustrated. The report of experiment point out the reliability of hardware is good and snubber circuit can protect power switching reliably. The C program based on the soft of CCS is edited to simularte and capture the maximum wind power of wing turbine. The result turns out that the program is exactitude, and the way of the maximum wind power point tracking can fulfill the need of experiment.The paper designs the three-phase bridge-type voltage source PWM rectifier with LCL filter.The flow of energy can flow between grid and rotor, the energy floe from grid to rotor under the state of sub-synchronous electric operation, and the energy flow from rotor to grid under the state of super-synchronous electric operation. However, Harmonic wave can not be inevitable from the inverter in the process of power transmission. Three-phase rectifier is designed on the base of LCL filter, for harmonic will be researched. The principle and mathematical model of LCL filter is introduced and the parameter of LCL filter is illustrated. The simulation of main circuit three-phase bridge-type voltage source PWM rectifier with LCL filter is set up in MATLAB. According to the out come of simulation, LCL filter can meet the need of design.