| The pumping unit is one of the most widely used oil-mining machinery,and it is also a large oil-consuming household in the oil field.Its electricity consumption accounts for about 40%of the total electricity consumption of the oil field.Pumping units can be divided into two categories:one is rod-type oil production equipment,and the other is rod-free oil production equipment.The beam pumping unit,the belt conveyor and the ground driven screw pump,which are common in production,belong to the rod-type oil production equipment;the electric submersible centrifugal pump and the hydraulic piston pump belong to the rodless oil recovery equipment.This paper introduces and analyzes the advantages and disadvantages of the rod-type oil production system and the rod-free oil production system,and proposes the existing problems of the rod-less submersible electric pump production system,and optimizes these problems.The existing rodless submersible electric pump has harmonics when it is driven by variable frequency,and the driving motor is located deep underground.The harmonics are amplified by the long-distance cable,causing the motor to overvoltage and generate heat,which has a great adverse effect on the downhole equipment;The mechanical reducer has a short service life due to its structural characteristics and insufficient strength of the material used.In response to these problems,the main work is as follows:First,consider the parameters of the long-line three-phase submarine cable itself.Usually,the method of adding a cable as a reactive component to the reactance of the stator winding is adopted,but since the method does not obtain the true voltage and current data of the downhole motor,vector control cannot be realized.Based on the equivalent circuit model of three-phase cable transmission,this paper analyzes the structural characteristics and electromagnetic mechanism of long-line submarine cable,analyzes the inductance and capacitance of long-line cable parasitic,and establishes a mathematical model to derive the transmission matrix and the exit end of any long cable.The power adaptive approximation acquisition algorithm is close to the real motor voltage and current values.Secondly,the mathematical model of the long-line three-phase submersible cable is combined with the transmission characteristics of the motor,and Clark and Park transform are used to establish a speed open-loop variable frequency speed control model and efficiency optimization control based on rotor field oriented vector control method.According to the research and development of the electric submersible screw pump frequency conversion speed control system,after more than one year of actual field operation verification,it has received the ideal control effect.Finally,according to the actual production requirements and special working conditions,the induction motor was electromagnetically designed,and the mechanical reducer and drive power were optimized.The calculation steps and results of the motor design are given in the paper.The reducer adopts two-stage parallel output,which can extend the life of the mechanical reducer.The power supply adds an active filter device to optimize the power waveform.The optimized and torque compensated submersible electric screw pump has been effective in more than one year of experiments.The motor starts running smoothly,the voltage and current waveforms are obviously improved,and there is no rod tube eccentric wear problem.The experimental results also confirm that the mathematical model of the long-line three-phase cable established by analyzing the parasitic inductance and capacitance of the long-line three-phase cable is correct;the driving model established by embedding the long-chain cable mathematical model into the motor vector control is also feasible;And the design of the motor and the optimized submersible electric screw pump system can meet the production,excellent running performance,energy saving and high efficiency. |
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