Research On The Electric Variable Pitch Servo System Of Wind Power

Wind power is a new type of renewable and clean energy, which has incomparable advantage on protecting the ecological environment and mode rating resources consumption of the earth. However, the output power of wind turbine is instable because of the wind energy has shortcomings such as low energy density, great variation and randomness. In addition, the diameter of wind rotor increases with the increasing of capacity of wind turbine, as well as the influence of factors such as altitude, unevenness of the density of air and turbulence intensity of the air stream, etc., the facors above are related to the unbalanced airflow thrust of wind rotor blade. Above problems can be improved by adjusting the pitch angle of blade.Variable-pitch control is the method which changes the windward angle of the blade under different wind speed so as to make the output power of wind turbine stable, the process is the blade rotating along its longitudinal axis through variable-pitch actuator. This method is especially important when the wind speed is above its rated value, the amount of the wind power which captured by wind turbines will be limited, which makes the output power of wind turbine keeping around the rated power, as well as protecting the whole structure of the wind turbine from damage, improving the stability, reliability and safety of wind turbine. Due to above adventages, the research of variable-pitch control technology of wind turbine has become a hot spot. This article mainly researches on electric variable pitch servo system of wind turbine, selects asynchronous motor as servo motor, main research contents are as follows:1. On the basis of vector control technology with rotor flux orientation in the asynchronous motor, control structure diagram of variable-pitch servo system is constructed. The system applies three closed-loop structures which include the position closed-loop, speed closed-loop and current closed-loop, in order to improve the accuracy, speediness and stability performance of the servo system.2. On the basis of theoretical study of wind power variable-pitch control system, the electric variable-pitch wind power system is established, including the mathematical model and the corresponding simulation model, such as wind speed, pitch angle controller, the variable-pitch servo system and wind turbine, etc.. The analysis of simulation results show that when wind speed is under its rated value, pitch angle keeps minimum to capture maximum wind energy; when wind speed is above its rated value, adjusts the pitch angle of blade according to the change of wind speed in real time, so as to control the amount of wind energy which captured by the wind turbine, which makes the speed of the wind turbine stable a round the rated speed and the output power of wind turbine stable around the rated power.3. The hardware of variable-pitch servo system is designed, including the design of main circuit and control circuit. The design of main circuit including the parameters selection of components, structure application and selection of components, etc.; control circuit including minimum system, sampling detection circuit, communication circuit, detection of position and speed, etc..A lot of work focused on the reliability, the protecting function, versatility, scalability, expanding and anti-interference ability of the system, etc, is accomplish. The structure of hardware of servo system is reasonable and compact, which meets the demand of experiment.4. The software is programmed on the hardware platform, the position loop, speed loop and current loop of servo system are debugged and related dynamic performance of system is experimented. Experimental results show that the position of the servo system is able to follow the given values and has good following performance.