Research On Pitch-Controlled Of Small Doubly-Fed Induction Generators

With the large-scale development of wind power industry, the lack of wind power generation technology has become the biggest obstacle to the development of wind power industry in China. Especially compared with developed countries, there is a large gap between us in the wind power technology of large scale in wind power generation unit, and technology of variable pitch control, and technology of variable speed constant frequency, so speeding up the research and development of China’s wind power technology is the urgent problem to be solved. The paper focuses on the key technology of wind power technology--variable pitch control method. Through the introduction of total structure diagram of doubly-fed wind generator system, it analyzes the principle of doubly-fed generator variable speed constant frequency, and builds the mathematical model and simulation model of doubly-fed motor. Then through analyzing the aerodynamic, it gets the limit value in Baez theory. It adopts the relationship between the wind energy utilization coefficient and tip speed ratio, and reaches to the control method of variable pitch in wind power system. Finally it builds mathematical model for the parts in variable pitch running condition.Adopting variable propeller pitch technology, doubly fed wind power generator makes the fan have good starting performance and braking performance. The main purpose of variable pitch regulating is to maintain the pitch constant when the wind speed below the rated one. Through the control device, it changes the speed of rotation of the rotor and adjusts the regulating fan tip speed ratio, so that the wind turbine can put out more wind energy; When the wind speed is higher than the rated one, for the safe operation of generator, it is necessary to increase the pitch, so the wind energy utilization rate is lessened, and the power output of the generator is reduced, and finally the output power is maintained at the rated value attachment. The essence of variable pitch control is to alter the pitch of the value according to the change of wind speed and output power. But the pitch system is multivariable and nonlinear, which makes the control of blade pitch angle become more difficult. In order to solve this problem, this paper designs fuzzy adaptive PID controller, combined with the traditional PID and fuzzy control. Through simulation, it gets that the designed controller can make the pitch has a follower, and the system has strong adaptability and robustness. In order to make the pitch change fastly and accurately, the paper designs the electric actuator. Electric variable pitch servo system uses DSP as the controller of actuator, and it adopts permanent magnet synchronous motor, and it design the hardware and software for the actuator. Through the simulation results, it can be seen that the variable pitch system has good stability and the wind speed changes, the pitch has good tracking performance, which achieves the control requirement.