Zero torque vector control method for motor of beam-pumping unit

Abstract

The invention discloses a zero torque vector control method for a motor of a beam-pumping unit. According to the method, when the beam-pumping unit is used for oil extraction, whether zero torque control or a load self-adaptive control shall be implemented is judged according to a detected motor rotational speed value and a load torque value of the beam-pumping unit; if zero torque control is implemented, a rotational speed ring is failure, an electromagnetic torque obtained through characteristic quantity calculation serves as a negative feedback of a torque inner ring, and thus, closed-loop control of zero torque is achieved; and if the load self-adaptive control is implemented, the rotational speed ring resumes to work, a detected load value serves as the negative feedback of the torque inner ring, and self-adaptive load change of the output torque of the motor is achieved. With the control method disclosed by the invention, on one hand, the output characteristic of the motor is matched with the load characteristic of the pumping unit better, on the other hand, regenerative power generation state of the motor can be eliminated or weaken, thus, the working efficiency of the beam-pumping unit is improved, and disturbance to a power grid by electric energy fed back from the motor is prevented.

Description

technical field [0001] The invention relates to a motor zero-torque vector control method of a beam pumping unit, belonging to the technical field of motor control. Background technique [0002] The beam pumping unit is widely used in various oil fields due to its advantages of simple structure, stable operation and reliable performance. Such as figure 1 As shown, the equivalent load of the beam pumping unit at the motor shaft alternates periodically, and there are two peaks on the equivalent load curve, which are the "dead points" of the pumping unit's upstroke and downstroke. However, in the middle and late stages of the downstroke of the pumping unit, it is easy for the pumping unit to back-drag the motor to run and generate negative torque. This negative torque causes the motor to run in the energy feedback braking state, which is an extremely bad working state. At this time, there will be energy storage and mutual exchange and transmission between the grid and the mot...

AI Technical Summary

Problems solved by technology

However, in the middle and late stages of the downstroke of the pumping unit, it is easy for the pumping unit to back-drag the motor to run and generate negative torque. This negative torque causes the motor to run in the state of energy feedback braking, which is an extremely bad working state.

At this time, there will be energy storage and mutual exchange transmission between the grid and the motor, which will greatly reduce the power factor of the grid and reduce the efficiency of the beam pumping unit

In addition, this phenomenon leads to generally low working efficiency of oilfield motors, and at the same time, there is a huge potential for energy saving

[0003] In order to solve the above technical problems, ordinary frequency conversion control usually processes this part of negative power on the DC side to prevent it from being fed into the power grid. Although this method prevents power feedback, it causes energy waste; the second method is to add an auxiliary inverter to send negative power back to the grid. However, the method of adding an auxiliary inverter leads to complex structure of the equipment and costs High, not easy to maintain, generally seldom used; third, at present, some oil fields also use overrunning clutches to eliminate energy feedback phenomenon, but overrunning clutches have short service life and need to be replaced frequently, which greatly increases the operating cost of the system

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