| Most oil fields in our country,beam pumping units are used to lift up oil from the formation, while the pumping unit itself need speed and has the disadvantages of low efficiency, low power factor, resulting in power consumption is very large.Currently the installed capacity of the pumping unit is in the hundreds of thousands or more and the annual power consumption is more than 100 million kwh, so the pumping unit has a huge potential for energy saving. In order to achieve energy-saving purposes, this paper adopts the method of cascade speed regulation to speed the motor.Cascade speed control is widely used, easy to achieve continuous, smooth speed control, not only improve the speed performance, but also can recover a lot of power, improve economic efficiency, so for energy saving is of great significance.There is no specific information on the whole working process of the punping units, therefore, this paper, on the basis of understanding the working principle of the pumping unit, simplifies a pumping stroke velocity diagram, which is used to determine the motor in electric or braking condition, to determine whether to join the brake torque to stop; on the basis of understanding the the principle of cascade speed regulation, this paper adopts two methods of traditional cascade speed regulation and chopper cascade speed control, respectively by the changes of real-time inverter angle and duty cycle to adjust motor speed. Finally, using the MATLAB software, in the Simulink environment using the two methods respectively to model the process of the whole sucker pumping unit, parameters determination and simulation. The simulation results of the two methods are compared, including the quickness of motor start, the rotor current feedback, power, current distortion influence to power grid, etc., analyzing the pros and cons of each method, which provides theory basis and validation method for the engineering design of the beam pumping unit motor speed control system. |
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