Research On Speed Automatic Control Technology Of The Surface-driven Progressing Cavity Pump

The surface-driven progressing cavity pump lifting technology has some advantages that include simple structure, flow and pressure stability, strong adaptability, as well as it is widely used in the exploitation of viscous crude wells, highly contained sand and gas oil well. In this paper, speed control in the process of the surface-driven progressing cavity pump lifting system as a starting point, dynamic fluid level effects on speed control are studied in detail, the theory and methods of soft start and soft stop for the surface-driven progressing cavity pump are expounded. Direct torque control method of variable frequency control strategy for asynchronous motor is determined. And the advantage and disadvantage of simulation results are compared.This paper first describes that the submergence depth effects on oil well pump efficiency, system efficiency, pump rate, pump inspection rate, based on using the weighted average function analysis the best dynamic fluid level, According to the oil well inflow and outflow for balance between supply and demand, Real time tracking and matching the well fluid supply capacity, Establish the speed control model of the surface-driven progressing cavity pump, According to the different dynamic liquid level to choose reasonable speed,According to the different dynamic liquid level to choose reasonable speed, Improve the efficiency of the surface-driven progressing cavity pump oil production.Then the paper detailed introduces the control theory and method of soft start and soft stop for the surface-driven progressing cavity pump, Analysis of the soft start rise time, and required starting torque and starting current in the process of soft start, Select S-shaped speed acceleration mode,According to the mechanical characteristics of asynchronous motor in the process of deceleration stop, select appropriate deceleration time and S-shaped speed reduction mode, Analysis of the composition of the anti torque of the surface-driven progressing cavity pump in the process of well shutdown, the required braking torque in the process of soft stop are determined, the relationship between the output of the frequency change and the braking torque of the variable frequency speed control system are established.Finally, the paper expounds the basic principle and system structure of asynchronous motor direct torque control technology, as well as built a simulation model of torque control system under Matlab/simulink simulation environment, by using the traditional PI speed controller, the problem of the slow response of torque and rotational speed 、 poor anti-interference ability occur in the sudden load or speed, To solve those problems, fuzzy PI speed controller with the reasonable parameter setting is introduced. The experimental simulation result shows that compared with the traditional direct torque control system based on PI speed controller, the speed and torque response of the improved direct torque control system based on fuzzy speed controller is faster,lower overshoot.it also show that dynamic response of speed control system are improved obviously.