| The wind power generation system(WPGS) is a device in converting wind energy into electrical energy, and the maximum power point tracking(MPPT) of WPGS is to ensure maximum wind energy into electric energy to improve the utilization rate of wind energy. In the actual operation, the maximum power point(MPP) will be influenced by the changes of environment in the wind farms where WPGS works. Moreover, wind turbine wind speed sensor and speed sensor of WPGS are easy to be damaged in bad weather, resulting in the decline of the reliability of the entire system. In order to solve above problems, the sensorless algorithm of WPGS will be provided and the maximum power will be corrected in this paper. Finally, two kinds of sensorless algorithm is used together in controlling the WPGS to achieve the MPPT without speed sensor. The main works are as follows:a) Considering the variation of environment will cause the air density value is no longer equal with standard value designed in WPGS, and changes in air density directly will vary many parameters data of the WPGS, so is the curve of the wind power. Firstly, using the air density calculation formula recommended internationally, and selecting the reasonable value of variable environment parameters, the air density is mainly relationship with three factors: air pressure, temperature, relative humidity. Then simplifying air density calculation formula, actual wind power could be calculated accurately. And the power curve of wind turbine is modified. Finally, the ranges of air temperature and air pressure are determined.b) After analysis of the impact of wind speed characteristics on measuring wind speed by the sensor, a method puts forward for estimating wind speed. The method mainly uses electric power to replace the power captured by the WPGS, reducing the additional sensor investment. Meanwhile, this estimation method is independent of wind energy coefficient, only needing to know its optimal value. When the air density set and the actual air density are not the same, the relationship between the wind speed estimated and the actual one will be given. The deviation between the maximum output and actual one are also different under different kind of air density.c) The speed observation method of WPGS is designed. With capturing the permanent magnet direct drive WPGS in this paper, the wind turbine blade speed can be obtained by speed observation for permanent magnet synchronous motor(PMSM). Considering the PMSM speed is unknown, and it can not be calculated by motor’s physical quantities, an unknown input observer is designed to observer it and giving the method to determine the parameters of the observer. Adopting this method not only realizes the generator speed sensorless control, but also achieves the MPPT of WPGS.d) Containing the sensorless algorithm of wind speed and motor speed, WPGS control system is determined where the estimation of wind speed used given speed, and the estimated motor speed as feedback. The MPPT control for the permanent magnet direct drive WPGS has been achieved. And when the actual air density and air density set are not the same, the deviation between the maximum output and actual one are given. |
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