Design And Research Of Speed Controller Based On Fixed-pitch Variable-speed Wind Turbine

Due to the operation of variable-pitch wind turbine below rated wind speed is still not ideal,by the mid 1990 s,various variable-speed wind turbine based on variable-pitch technology began to enter the wind farm.The main difference between variable-speed and fixed-speed wind turbine control system is variable-speed wind turbine takes the wind speed signal as the input variables to carry out speed and power control.The main characteristic of variable-speed wind turbine is that in low wind speed area,it can track the optimal power curve,the wind turbine has the highest energy conversion efficiency;in high wind speed area,it can always operate at the rated power,and the output power is more stable.This paper takes the fixed-pitch variable-speed wind turbine as the research object,and introduces a fixed-pitch control strategy based on the permanent magnet synchronous motor.The PI double loop control technology is adopted to control the electromagnetic torque by controlling the stator current.The control of electromagnetic torque causes the speed change,so that the power of the generator in the low wind speed area can achieve maximum power tracking,in high wind speed area can maintain a constant power.The use of PI controller can enhance the stability of the system,and easy to realize the digitalization.This paper adopts space voltage vector control technology(SVPWM),SVPWM technology is a novel control method in recent years.It is considered from the overall effect of three-phase output voltage,focusing on how to make the motor to obtain the ideal circular flux track.Compared with SPWM Technology,SVPWM technology let winding current has the smaller harmonic waveform,it make the motor torque ripple reduce,rotating magnetic field more close to round.It make the utilization rate of DC voltage greatly improved,and easy to realize the digitization.In this paper,based on the previous theory of variable speed control,the RTLAB hardware in the loop simulation experiment is carried out to further verify the feasibility of the variable-speed control strategy.This paper introduces the software programming steps of the variable-speed wind turbine controller.The filtering algorithm,PI control algorithm and SVPWM control algorithm are introduced.This paper designs the hardware circuit of the wind turbine controller,and gives the circuit diagrams of the voltage conversion module,DSP module and PWM output module.The RTLAB hardware in the loop simulation experiments show that the variable-speed control strategy can achieve the maximum power tracking in low wind speed area and the constant power operation in high wind speed area.It shows that the fixed-pitch variable-speed wind turbine has the characteristics of low cost and high efficiency.