Research on Control System of Variable Speed ​​Constant Frequency Doubly-Fed Wind Generator

Research on Control System of Variable Speed ​​Constant Frequency Doubly-Fed Wind Generators Dai Hongtao, Zou Qiuqi, Lin Chengwu (School of Information Science and Engineering, Shenyang University of Technology, Shenyang 110023, China) This control technology.

315: A variable speed constant frequency doubly-fed generator is a new type of wind power generator integrating aerodynamics, motor manufacturing, hydraulic transmission, power electronics technology and computer control technology. The core technology of this type of wind turbine is a control system design based on power electronics and computer control technology. Therefore, this paper studies the control system of VSCF doubly-fed wind turbine and its corresponding control technology, and gives some parts. The microcomputer control system based on 8XC196MC is as shown. Mainly composed of 8XC196MC chip, PC communication module, PWM signal drive and isolation module, sensor output signal processing module, status monitoring and fault processing module, display, keyboard module and relay control module.

If less than synchronous speed, the waveform generator WG directly outputs the three-phase PWM control signal complementary to the passage 6, the module IR2132 AAAAAAA \ eight hundred eighty-eight sub-synchronous-speed synchronous: when the super-synchronous speed synchronous speed the transition of the rotor AC excitation current fed Fig.4Wavformofrotorcurrent drive control waveform generator rotor side converter I, produces a corresponding frequency, amplitude of the excitation current. In the vicinity of the synchronous speed and over a short range of speeds synchronous speed, to achieve stable operation of the system so that the feeding and inverting smoothly continuous sequence of excitation current may be fed to the rotor trade deficit low frequency alternating current, direct current can also be fed. When super synchronous speed, the rotor chopper boosted potential emitted by the converter inverter back to the grid.

3 Experimental results analysis 1 Variable speed constant frequency control adjusts the frequency of rotor excitation current according to the change of wind turbine speed, so that the voltage frequency of the output of the doubly-fed generator is consistent with the grid, that is, constant frequency control. The control system uses LMA-200BM-C05E photoelectric encoder, which outputs 2 000 pulse signals per revolution. If the pole number of the motor is 2, the stator voltage frequency is fi=50Hz, kp is the rectangular pulse recorded by the MCU counter every 10ms. feeding the number of the rotor, the rotor mathematical relationship with the exciting current frequency f2 is â—Ž kp below synchronous speed. The current frequency is . Nk 2) The current frequency fed into the rotor at the super-synchronous speed is the waveform of the rotor current frequency adjusted with the speed when the doubly-fed generator is lower than the synchronous speed, and the output voltage is controlled by the open loop, so that the shifting constant of the doubly-fed generator is realized. Frequency control.

3.2 Three-state switching control When the speed of VSCF doubly-fed generator is converted between sub-synchronous speed, synchronous speed and super-synchronous speed, not only the phase sequence of the rotor excitation current is changed, but also the excitation current fed near the synchronous speed is ultra-low frequency. The alternating current therefore increases the difficulty of control. In order to feed the AC current waveform near the synchronous speed, the rotor current waveform is basically smooth and continuous.

3.3 Grid-connected experiment analysis When the VSCF doubly-fed generator is connected to the grid, it is necessary to make the stator-side power generation voltage of the generator and the grid voltage strictly the same frequency and the same amplitude in the same frequency, otherwise it will have serious harmful consequences. It is the voltage and current waveform diagram of the stator side of the generator before and after the grid connection. The upper part is the voltage waveform and the lower part is the current waveform. The left half is the voltage and current waveform before the grid connection, and the right half is the voltage and current waveform after the grid connection. It can be seen that since there is no closed-loop control of the active power after grid connection, the current waveform oscillates.

4 Conclusions The 8XC196MC single-chip microcomputer is used as the control variable-speed constant-frequency doubly-fed wind turbine control system. The basic control technology of the variable-speed constant-frequency doubly-fed wind turbine is studied. It realizes variable speed constant frequency operation; smooth conversion and grid-connected control of three operating states: sub-synchronous speed, synchronous speed and super synchronous speed. Experiments show that the design of the control system is reasonable, and lays a foundation for the study of bidirectional converter and active power regulation and corresponding control strategies under different operating conditions.

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