Research On Power Servo Control Technology Of Beam Pumping Unit

As an important extraction machine,beam pumping unit has been used widely in oil fields.However,some factors including intrinsic structure,drive system often lead to a variety of practical problems,such as overloaded motor capacity,strong fluctuation of load and reverse power generation.As a result,the system become less effective and suffer from strong fluctuation of power.In order to deal with these problems,in this paper,we investigate a power servo control technology for beam pumping unit and develop a set of control system.With the help of proposed system,the beam pumping unit is able to have better performance and efficiency.We firstly looked into the operation principle of beam pumping unit,after which we investigated its motion law and load characteristics on the basis of the kinematics and dynamics.Then,we presented a power servo control method with the goal of steady energy output.On the basis of variable speed drive technology,this method is able to adjust the speed of motor according to the load variation of the pumping unit and thus running smoothly.We also analyzed the feasibility of this control method and built a scheme for the power servo control system of the beam pumping unit.Secondly,the problems of model-based control policy and classical control policy(PID)existing in complex electromechanical coupling system like beam pumping unit are analyzed.After that a model-free adaptive control algorithm is introduced for power servo control of the pumping unit.This algorithm is model-free and relies only on the system I/O data for feedback control.In order to improve its interference immunity,high speed tracking differentiator is applied for signal filtering.On the other hand,considering the periodic characteristics of the pumping unit load and repetitive control,we developed a model-free adaptive control method,and introduce a learning factor to adjust the learning rate of historical cycle information.The effectiveness of algorithm is confirmed by using MATLAB simulation.Lastly,according to the overall scheme of the system,we completed the design and development of the control system at the level of software and hardware.Besides,a monitoring software on PC is developed to support the control system.We tested and analyzed the power servo control system of the beam pumping unit both in the laboratory and on the real wells.The results illustrated that the control system can effectively reduce the power fluctuation during operation and the time of power generation,which saves energy without changing the times of strokes.This is of great significance for the realization of intelligent control and production in the oil field.