RU2610857C1 - Control method for deep well pump - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention refers to the control methods for a deep well pump including the well fill-up control by a volume of a liquid sucked by a pump; the methods are based on variation of electrical parameters of a driven induction motor. The supply current of the induction motor is measured; the active constituent of the measured current is calculated; and the reference diagram of the active constituent per a pump operation cycle is drawn and saved. Then, the current diagrams of the said constituent are drawn; their deviation from the reference diagram is calculated by a selected criterion; and in the case of an exceedance of a limit by the calculated deviation, the electric motor is shutdown for a projected period of a well fill-up. After that, the electric motor is re-started with the control of the said exceedance.

EFFECT: control method of a deep well pump increases accuracy of the well fill-up control.

3 cl, 1 dwg

Description

Technical field

The invention relates to methods for controlling a sucker rod pump (SHS), including controlling the filling of a well by the volume of fluid pumped by the pump, which are based on measuring the electrical parameters of an asynchronous electric drive motor. Such control of well filling does not require the installation of a dynamometric sensor on the elements of the mechanical drive of the sucker rod pump (for example, on its rod) to determine the forces corresponding to the degree of filling of the suction cavity of the well pump.

The invention may find application in oil production units equipped with a mechanical drive in the form of a rocking machine with a crank mechanism or in the form of a rack-and-pinion linear drive.

State of the art

There is a known method of controlling the pressure train with the control of the filling of the well, based on the dynamogram of the efforts, reflecting the degree of filling of the suction cavity of the sucker rod pump [RU 2546376].

The disadvantage of this analogue is the need for installation and maintenance of a dynamograph (a sensor that measures mechanical forces on the upper bar of the ШСН or on other elements of its mechanical drive), equipped with an autonomous power source.

Known methods for controlling the SHS with controlling the degree of filling of the suction cavity of the pump (and, therefore, filling the well) by the measured electrical parameters (current, voltage) of the drive motor, which are used to determine the magnitude characterizing the torque on the shaft of the drive motor, which, in turn, , allows you to track the effort on the upper rod of the SHS [EA 201500517, US 5362206].

As a prototype, a well-known method for controlling a sucker rod pump with well filling control is selected, which consists in measuring the current and voltage of the electric motor, determining the phase angle between them and, when the specified angle is exceeded, the motor is stopped for the expected (predicted) time of filling the well, then resume the operation of the electric motor with the control of the specified excess [patent US 5362206].

The disadvantage of the prototype is the low reliability of the assessment of well filling according to the criterion selected in the prototype — the phase angle between the current and the voltage of the electric motor.

SUMMARY OF THE INVENTION

The subject of the invention is a method for controlling a sucker rod pump with control of well filling, which consists in measuring the supply current of the asynchronous pump motor, calculating the active component of the measured current, generating and storing the reference diagram of the active component for the pump cycle, generating current diagrams of the indicated component, calculating according to the selected criterion, their deviation from the reference diagram and when the calculated threshold deviation is exceeded, the electric motor is stopped Spruce on the predicted time of filling the well, and then resume operation of the motor with the control of said excess.

The development of the invention reveals two possibilities for calculating the active component of the measured current, which consists in the fact that:

- the active component of the measured current is calculated using the passport data of the induction motor;

- the active component of the measured current is calculated as the projection of the vector of the measured current on the direction of the vector of the additionally measured voltage of the electric motor.

The inventive method, as well as the selected prototype, is based on measuring the electrical parameters of the induction pump motor of the sucker rod pump, which makes it possible to evaluate the torque on the shaft of the ШСН drive electric motor, but differs in that it uses not the phase angle between the current and voltage as the evaluation criterion, but the active component of the measured current, which, as will be shown in the section "Implementation of the invention", more accurately reflects the actual values of the torque on the motor shaft and the corresponding about efforts in the top bar of the pump.

The technical result achieved by the implementation of the invention is to increase the reliability of monitoring the filling of the well.

The implementation of the invention in view of its development

ШСН is connected with an asynchronous electric drive motor through a mechanical drive that converts the rotational movement of the motor shaft into the reciprocating motion of the rod, rod string and plunger of the borehole pump. Such a mechanical drive is performed in the form of a rocking machine with a crank mechanism [RU 2532488] or a linear drive with a gear-rack mechanism [RU 159640].

The proposed method can be implemented using a programmable controller for the control circuit of the SNR, equipped with an analog-to-digital converter for digitizing the readings of the current sensor (and, possibly, the voltage sensor).

The method is as follows.

Measure the current I ₁ power supply of the drive induction motor ШСН. The digitized values of the measured current calculate its active component (active current of the stator of an induction motor).

The calculations described below, performed by the CHF controller, are based on the well-known vector diagram of an induction motor shown in FIG. 1 [V.Ya. Bespalov, I.F. Kotelenets. Electric cars. - M.: Publishing. Center Academy, 2006, p. 138].

From the vector diagram of the induction motor (Fig. 1) we have:

- вектор питающего тока (тока статора),

- приведенный к статору вектор тока ротора,

- вектор тока намагничивания.Where

is the vector of the supply current (stator current),

- reduced to the stator current vector of the rotor,

is the magnetization current vector.

The calculations are based on the fact that in the steady-state mode of operation of the induction motor, its slip is small and the rotor current brought to the stator is active, i.e. coincides in phase with the applied voltage U ₁ . therefore

- приведенная к статору активная составляющая тока ротора, I_{1 a} - активная составляющая тока статора.Where

is the active component of the rotor current reduced to the stator, I _{1 a} is the active component of the stator current.

рассчитывается активная составляющая тока статора приводного асинхронного двигателя. Здесь I_μн - номинальный ток намагничивания, предварительно рассчитанный по формуле

, где I_1н и cosϕ_н - номинальные (паспортные) значения тока статора и коэффициента мощности приводного асинхронного двигателя.According to the formula

the active component of the stator current of the drive induction motor is calculated. Here, _μn I - nominal magnetizing current, previously calculated by the formula

where I _1n and cosϕ _n are the nominal (passport) values of the stator current and power factor of the induction motor drive.

The active component of the stator current I _{1 a} can also be determined using another sequence of calculations performed by the programmable controller. For example, it can be calculated as the projection of the measured current vector I ₁ onto the direction of the vector of the additionally measured motor voltage.

и

. Диаграммы

формируют за цикл работы штангового насоса, используя для этого (как и в прототипе) датчик перемещения, установленный на элементе механического привода и отражающий текущее положение плунжера и штока штангового насоса при возвратно-поступательном движении.The obtained value of I _{1 a is} used to form the reference and current time diagrams in the controller memory

and

. Charts

form for the cycle of the sucker rod pump, using for this (as in the prototype) a displacement sensor mounted on a mechanical drive element and reflecting the current position of the plunger and rod pump rod during reciprocating motion.

снимают (формируют и обновляют в памяти контроллера) изредка (например, раз в месяц), когда насос заведомо работает в штатном режиме (полное заполнение полости насоса, отсутствие неисправностей и т.п.).Reference chart

they are removed (formed and updated in the controller's memory) occasionally (for example, once a month) when the pump obviously works in the normal mode (full filling of the pump cavity, absence of malfunctions, etc.).

снимают непрерывно или с заданной периодичностью (например, каждые полчаса).Current chart

removed continuously or at specified intervals (for example, every half hour).

сравнивают с хранящейся в памяти контроллера эталонной диаграммой

, вычисляя их отклонение от эталонной диаграммы.Captured Current Charts

compared with the reference chart stored in the controller memory

calculating their deviation from the reference chart.

The deviation is calculated according to the selected criterion (in the simplest cases, this can be the maximum or rms difference of the time-aligned diagrams) and compared with a given acceptable deviation value. The selected criterion may include the calculation of deviations with different weights in different parts of the cycle (for example, for the part of the cycle corresponding to the lifting of the bar, the deviations can be calculated with the coefficient one, and for the rest of the cycle with the coefficient zero).

If the resulting deviation exceeds a predetermined threshold (which indicates a significant discrepancy between the current and reference diagrams), the drive motor is stopped by the controller signal and the timer starts for the expected (predicted) time of natural filling of the well (for example, for one hour). At the end of this time (by the timer signal), the drive motor and the process of forming and storing the current diagram, calculating their deviations from each other and comparing the deviation with a given threshold are resumed. Repeated excess of the specified deviation can be used as the basis, in particular, for the following conclusions:

- about the occurrence of a malfunction of the pump or its mechanical drive (with subsequent diagnosis of the defect);

- on the advisability of increasing the predicted time to fill the well;

- on taking measures to increase reservoir pressure.

Compare the claimed method with the prototype.

According to the foregoing, in the claimed method, the assessment of the force on the upper bar of the SCH, i.e. assessment of the force directly reflecting the degree of filling of the suction cavity of the pump and (in the absence of defects in the SHS and its mechanical drive) the degree of filling of the well is carried out indirectly - by the value of torque as a function of the active component I _{1 and the} stator current of the drive motor, calculated from the measurement results power current consumed by the motor.

As is known [O.D. Goldberg, S.P. Helemskaya. Electromechanics. - M.: Publishing. Center Academy, 2007, p. 205], the torque M on the shaft of the induction motor is connected with the magnetic flux Ф and the active component of the stator current I _{1a by the} ratio

where k is a constant coefficient.

With a constant magnetic flux Φ, this expression can be written in the form of a linear (proportional) relationship between the active component of the current of the induction motor and the torque

where C = const.

In the prototype, to evaluate the force in the upper rod of the ШСН and the corresponding torque on the shaft of the drive motor, the current angle ϕ between the applied voltage U ₁ (coinciding in phase with the active component of the stator current I _{1 a} ) and the measured stator current I _{1 is used} . As can be seen from the vector diagram (Fig. 1), the value of the angle ϕ is determined by the relation

From a joint consideration of expressions (1) and (2) it follows that the dependence M (ϕ) used in the prototype is non-linear and, therefore, reflects the torque on the motor shaft with a larger error than the linear dependence M (I _{1 a} ) used in the proposed method.

Thus, the use of the active component of the stator current of the drive induction motor as an estimate of the magnitude of the torque on its shaft (instead of the phase angle used for this purpose in the prototype) allows to obtain the above technical result of the proposed method is to increase the reliability of monitoring the degree of filling of the well.

Claims (3)

1. The method of controlling a sucker rod pump with a control of filling the well, which consists in measuring the supply current of the asynchronous pump motor, calculating the active component of the measured current, generating and storing the reference diagram of the active component for the pump cycle, forming the current diagrams of this component, and calculating by the selected criterion, their deviation from the reference diagram and when the calculated deviation exceeds the threshold, the motor is stopped for the predicted time complements the well, and then resume operation of the motor with the control of said excess. 2. The method according to p. 1, in which the active component of the measured current is calculated using the passport data of an induction motor. 3. The method according to p. 1, in which the active component of the measured current is calculated as the projection of the vector of the measured supply current to the direction of the vector of the additionally measured voltage of the electric motor.

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