Initial position positioning device for plunger pump

Abstract

The utility model relates to an initial position positioning device for a plunger pump. The initial position positioning device comprises a controller, a motor, a moving part, the plunger pump, a switch and a current detection device. The input end of the controller is electrically connected with an input transformer of which the secondary side midpoint is grounded, the output end of the controller is electrically connected with the three-phase input end of the motor through an armored cable, and the armored cable is grounded and is electrically connected with a motor shell; the motor is mechanically connected with the moving part and the plunger pump, the switch is arranged in the moving part, one end of the switch is electrically connected with the center point of a motor stator winding, and the other end of the switch is electrically connected with a motor shell. The current detection device is connected into an electric loop of the motor; when a moving part is positioned, direct-current voltage or low-frequency alternating-current voltage with a certain amplitude is superposed in three-phase output voltage of a controller, and whether a switch is closed or not is identified by detecting the change of superposed current generated in an electric loop of a motor through a current detection device; whether the plunger moves to the initial position is judged according to whether the switch is closed.

Description

Technical Field

[0001] This application relates to the field of oil extraction, and more particularly to an initial position positioning device for a plunger pump. Background Technology

[0002] In oilfield production, mechanical methods such as beam pumping units are commonly used. This method converts the rotational motion of a three-phase electric motor into the reciprocating motion of the sucker rod through mechanical transmission. While simple in structure and highly reliable, it suffers from drawbacks such as significant efficiency losses in the transmission system, rod wear, and high noise levels. Using a rodless pump (motor + moving parts + reciprocating plunger pump) downhole can effectively avoid problems like rod wear. The plunger pump's drive motor can be a rotary motor, which drives a lead screw to rotate, causing the moving parts to reciprocate. These moving parts then drive the plunger in the pump's cylinder to continuously reciprocate, pushing the crude oil from the well to the surface, thus achieving oil extraction.

[0003] Given that it is generally impossible or inconvenient to install mechanical position sensors on downhole motors or plunger pumps, the displacement of moving parts can only be achieved through open-loop control based on motor characteristics, which cannot accurately determine the actual position of the plunger and moving parts. Due to unavoidable downhole phenomena such as motor jamming, plunger pump leakage or cavitation, and control errors, the positions of moving parts and plungers will deviate from the set positions. After a certain period of time, these positional deviations may accumulate and cause the plunger to collide with the motor, leading to motor deformation or even damage. This reduces the service life of the motor or plunger pump and increases the operation and maintenance costs of the oil production equipment.

[0004] Therefore, in practical applications, determining the real-time mechanical position of moving parts or plungers is crucial, and the ability to reposition and calibrate their positions is essential for extending the service life of motors and plunger pumps and reducing oil extraction costs. This invention fully utilizes the potential of a frequency converter by artificially superimposing a certain amplitude of DC voltage or low-frequency AC voltage onto the normal three-phase AC output voltage. Using only a three-core cable that can be several kilometers long and a switch installed at an appropriate location inside the moving parts or plunger pump, the mechanical position of the moving parts and plunger pump plungers can be determined by detecting changes in the motor current. Summary of the Invention

[0005] In view of this, this application proposes an initial position positioning device for a plunger pump.

[0006] According to one aspect of this application, an initial position positioning device for a plunger pump is provided, comprising: a controller, a motor, a moving part, a plunger pump, a switch, and a current detection device;

[0007] The controller's input terminal is electrically connected to the input transformer, which is grounded at the midpoint of the secondary side. The controller's output terminal is electrically connected to the three-phase input terminal of the motor via an armored cable to achieve motor control. The armored cable is grounded and electrically connected to the motor's casing.

[0008] The motor is mechanically connected to the moving parts and the plunger pump. The motor is suitable for driving the moving parts and the plunger of the plunger pump to reciprocate along the length of the wellbore within the oil well.

[0009] The switch is located inside the moving part. One end of the switch is electrically connected to the center point of the motor stator winding, and the other end of the switch is electrically connected to the housing of the motor or plunger pump. The switch remains open when the plunger has not moved to the initial position, and switches to the closed state when the plunger is touched by the moving part when it moves to the initial position.

[0010] A current detection device is connected to the motor's electrical circuit to detect the current value in the motor's electrical circuit;

[0011] When positioning moving parts, a DC voltage or low-frequency AC voltage of a certain amplitude is superimposed on the three-phase output voltage of the controller, and the current current value in the motor's electrical circuit is detected by the current detection device.

[0012] When the current detection device detects that the current value of the motor's electrical circuit contains superimposed current or its change caused by superimposed voltage, it indicates that the switch is closed, that is, the plunger moves to the initial position.

[0013] When the current detection device does not detect any superimposed current or its change caused by superimposed voltage in the current current value of the motor's electrical circuit, it indicates that the switch is in the open state, that is, the plunger has not yet moved to the initial position.

[0014] Beneficial effects: When initially positioning the plunger pump, a DC voltage or low-frequency AC voltage of a certain amplitude is superimposed on the three-phase output voltage of the controller. Then, the motor drives the plunger to move towards the initial position. When the moving part touches the switch and closes the switch, the current detection device can detect that the current in the motor's electrical circuit has a superimposed current caused by the superimposed voltage output by the controller or a change there. At this time, it can be determined that the plunger has moved to the initial position. Therefore, the change in the superimposed current generated in the motor's electrical circuit can be used to identify whether the switch is closed. The position of the plunger is determined by whether the switch is closed. By positioning the plunger, the accumulation of errors is reduced, which can effectively reduce the failure rate of the plunger pump and the motor, improve operating efficiency, extend their service life, and provide strong support for the safe production and improved economic benefits of enterprises.

[0015] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0016] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this application together with the specification and serve to explain the principles of this application.

[0017] Figure 1 A schematic diagram of an initial position positioning device for a plunger pump according to a first embodiment of this application is shown;

[0018] Figure 2 A schematic diagram of an initial position positioning device for a plunger pump according to a second embodiment of this application is shown. Detailed Implementation

[0019] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0020] It should be understood that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0023] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0024] Figure 1A schematic diagram of an initial position positioning device for a plunger pump according to a first embodiment of this application is shown; Figure 2 A schematic diagram of an initial position positioning device for a plunger pump according to a second embodiment of this application is shown. Figure 1 and Figure 2 As shown, an initial position positioning device for a plunger pump includes: a controller, a motor, a moving part, a plunger pump, a switch, and a current detection device. The input terminal of the controller is electrically connected to an input transformer with its secondary side grounded at the midpoint. The output terminal of the controller is electrically connected to the three-phase input terminal of the motor via an armored cable to control the motor. The armored cable is grounded and electrically connected to the motor casing. The motor is mechanically connected to the moving part and the plunger pump. The motor is suitable for driving the moving part and the plunger to reciprocate along the length of the wellbore within the oil well. The switch is located inside the moving part. One end of the switch is electrically connected to the center point of the motor stator winding, and the other end of the switch is electrically connected to the motor casing. The switch remains open when the plunger has not moved to the initial position and switches to a closed state after being touched by the moving part when the plunger moves to the initial position. The current detection device is connected to the motor's electrical circuit to detect the current value in the motor's electrical circuit.

[0025] It should be noted that the controller, acting as the motor's control device, drives the motor's output shaft to rotate continuously in both directions. During this rotation, the motor's output shaft drives the moving parts to reciprocate, which in turn drives the plunger in the plunger pump to reciprocate within the wellbore. At this time, the armored cable between the controller and the motor only carries the three-phase AC voltage required to drive the motor. When initially positioning the moving parts or the plunger in the plunger pump, a DC voltage or low-frequency AC voltage of the same amplitude is manually superimposed onto the controller's three-phase output voltage, driving the motor's output shaft to rotate. This brings the moving parts and plunger closer to their initial positions, and a current detection device monitors the current value in the motor's electrical circuit. When the plunger and moving parts move to the switch position and touch the switch, the switch closes, creating a current path between the center point of the motor stator winding and the grounded armored cable sheath. The current detection device then detects the superimposed current in the motor's electrical circuit caused by the superimposed voltage output by the controller. This indicates that the normally open switch has closed, meaning the moving parts and plunger have reached their initial positions.

[0026] It should be further explained that the initial position is a manually set limit position. Therefore, when the plunger is in normal oil production operation, the moving parts or plunger will not move to the switch position during reciprocating motion, and the switch remains open. However, when the moving parts or plunger pump needs to be positioned initially, the moving parts or plunger will move outside the working stroke range. Once the current detection device detects that the current in the motor's electrical circuit has a superimposed current caused by the superimposed voltage output by the controller, it can immediately determine that the plunger has reached the initial position. At this time, the frequency converter has completed the initial position positioning operation of the moving parts or plunger. Then, the controller causes the moving parts to leave the switch, the switch is automatically turned off, the circuit of the motor midpoint grounded through the armored cable is disconnected, and the oil production equipment returns to the normal oil production operation state.

[0027] Since oil wells can typically reach depths of over a kilometer, and both the plunger pump and motor are located inside the wellbore, it is difficult to determine the exact position of the moving parts of the motor or the plunger (even if the motor is on the surface, the exact position of the moving parts cannot be determined without turning it on). This application features a simple overall connection structure, allowing for the initial positioning of the plunger pump within the well periodically or manually. The entire process does not require downtime, thus avoiding oil production losses. It can also effectively determine whether the plunger has moved to its initial position, making the initial positioning operation of the plunger pump more convenient and efficient. By periodically or when necessary locating the plunger, the accumulation of errors can be reduced, effectively lowering the failure rate of the pump and motor, improving operating efficiency, and extending service life, providing strong support for the safe production and improved economic benefits of enterprises.

[0028] like Figure 1 As shown, the input terminal of the controller is electrically connected to the input transformer whose midpoint is grounded. The U, V and W terminals of the controller are electrically connected to the three-phase input terminals of the motor, respectively. The metal sheath of the armored cable is in direct contact with the ground.

[0029] Furthermore, the armored cable uses a common three-core armored cable, and the controller's U terminal, V terminal, and W terminal are electrically connected to the motor's three-phase input terminals through the three wires of the armored cable.

[0030] In one possible implementation, the current detection device is a current sensor, which can be connected to any one of the three-phase inputs of the motor. A current sensor can be connected in series with any one of the wires between the controller's U, V, and W terminals and the motor's three-phase inputs; or a current sensor can be connected in series with any two wires between the controller's U, V, and W terminals and the motor's three-phase inputs; or a current sensor can be connected in series with each of the three wires. This application does not limit this approach.

[0031] Preferably, the controller uses a frequency converter, which can adjust the speed and direction of the motor in real time to achieve energy saving, and also has multiple functions such as soft start and motor protection.

[0032] In one possible implementation, it also includes: a transformer; the input terminal of the controller is electrically connected to the transformer to be connected to a three-phase AC input power supply via the transformer; the secondary side of the transformer is star-connected and the neutral line is grounded; the secondary winding of the transformer is electrically connected to the controller; and the primary winding of the transformer is connected to a three-phase AC power supply.

[0033] Furthermore, the overall principle is explained as follows: Only when executing the "positioning" function does the controller superimpose a DC voltage or low-frequency AC voltage of the same amplitude onto the normal three-phase output voltage. When the switch is open: the superimposed voltage has the same potential in the motor, no superimposed current is generated, and the current detection device cannot detect the current corresponding to the superimposed voltage; when the switch is closed: the controller's three-phase output forms three identical phase voltages with the grounded motor windings, and the current detection device will measure the current corresponding to the superimposed voltage. Thus, by measuring the presence or absence of the superimposed current through the current detection device, the on / off state of the switch is indirectly identified, thereby achieving the initial position calibration of the plunger.

[0034] Example 1: A normally open switch is installed at a suitable location inside the moving part. The moving part will not touch this switch during normal reciprocating motion. Only during the initial positioning process, when the controller drives the moving part to slowly move towards the switch, a DC voltage or low-frequency AC voltage of the same amplitude is superimposed on its normal three-phase output voltage. Simultaneously, a current detection device detects the current of the three-phase output (U, V, and W) of the frequency converter controller (i.e., the three-phase input of the motor). When the switch is open: there is no superimposed current caused by the superimposed voltage in the three wires U, V, and W; when the moving part moves to the position of the switch, the switch closes, and superimposed current caused by the superimposed voltage appears in the three wires U, V, and W, and their amplitudes are equal at the same time, indicating that the switch is closed.

[0035] Example 2: When the secondary winding of the transformer is only electrically connected to the controller, i.e., the transformer only supplies power to the controller, such as Figure 2As shown, the current detection device can be connected in series in the neutral line of the transformer's secondary side connected to ground. It is suitable for detecting the current value in the neutral line of the transformer's secondary side connected to ground. It should be noted that when the transformer is configured to supply power to the controller alone, it is also possible to determine whether the plunger has reached the initial position simply by detecting whether there is a superimposed current caused by the superimposed voltage in the neutral line of the transformer's secondary side connected to ground. If a DC voltage or low-frequency AC voltage of the same amplitude is superimposed on the three-phase voltage output by the controller, and the current detection device detects a superimposed current caused by the superimposed voltage in the neutral line of the transformer's secondary side connected to ground, it indicates that the switch is closed. However, in this case, the current value detected by the current detection device is three times the current value in any one of the three wires U, V, and W of the controller, making it easier to detect and identify.

[0036] Example 3: Two normally open switches are used in parallel. One is placed at a suitable position on the moving part or plunger pump, and the other is placed at another suitable position on the moving part or plunger pump. The controller can drive the moving part and plunger to move slowly downward to perform initial positioning, or drive the moving part and plunger to move slowly upward to perform initial positioning, which improves the ease of use of the whole set of equipment.

[0037] Multiple switches can also be used in parallel to achieve positioning of moving parts or plungers at multiple different positions and to adopt different positioning processing modes.

[0038] Example 4: The above descriptions are all based on superimposing a DC voltage or low-frequency AC voltage of the same amplitude onto the three-phase output voltage of the controller. This way, regardless of whether any one, two, or three phases of the controller's three-phase output lines are being detected, or when detecting the transformer neutral line as in Example 2, it is only necessary to determine the presence or absence of the superimposed current caused by the superimposed voltage, making it simple and convenient to implement. In reality, superimposing voltages of different amplitudes or shapes onto any output line of the controller can also identify the on / off state of the switch. However, when the switch is open, there may also be superimposed current in the three-phase output lines or the transformer neutral line (with a few exceptions), which would make the judgment and calculation complex and cumbersome. Both of these methods of superimposing voltages of the same and different amplitudes are within the scope of protection of this application.

[0039] Furthermore, the switch can be a limit switch, a reed switch, a mechanical contact switch, or other components that can achieve the function of switching on and off.

[0040] Preferably, the current detection device can be a Hall current sensor, or other current detection methods can be used.

[0041] Furthermore, the motor can be a permanent magnet synchronous motor, a separately excited synchronous motor, or an asynchronous motor.

[0042] Driven by the controller, the motor drives the lead screw to rotate continuously in both directions. The moving parts are mechanically connected to the lead screw. The motor drives the lead screw to move the moving parts up and down through the forward and reverse rotation. The moving parts then drive the plunger of the external plunger pump to reciprocate, continuously pushing the crude oil from the well to the surface. In use, the motor is at the bottom and the plunger pump is at the top, placed in the oil well.

[0043] Several embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An initial position positioning device for a plunger pump, characterized in that, include: Controllers, motors, moving parts, piston pumps, switches and current detection devices; The input terminal of the controller is electrically connected to the input transformer whose secondary side is grounded at the midpoint. The output terminal of the controller is electrically connected to the three-phase input terminal of the motor via an armored cable to realize the control of the motor. The armored cable is grounded and electrically connected to the outer casing of the motor. The motor is mechanically connected to the moving part and the plunger pump, and the motor is adapted to drive the moving part and the plunger of the plunger pump to reciprocate along the length of the wellbore within the oil well. The switch is disposed inside the moving part. One end of the switch is electrically connected to the center point of the motor stator winding, and the other end of the switch is electrically connected to the motor housing. The switch remains open when the plunger has not moved to the initial position, and switches to a closed state when the plunger is touched by the moving part when it moves to the initial position. The current detection device is connected to the electrical circuit of the motor to detect the current value in the electrical circuit of the motor. When positioning the moving part, a DC voltage or low-frequency AC voltage of a certain amplitude is superimposed on the three-phase output voltage of the controller, and the current detection device detects the current value in the electrical circuit of the motor. When the current detection device detects that the current value of the electrical circuit of the motor contains a superimposed current or its change caused by the superimposed voltage, it indicates that the switch is closed, that is, the plunger moves to the initial position; When the current detection device does not detect any superimposed current or its change caused by superimposed voltage in the current current value of the motor's electrical circuit, it indicates that the switch is in the open state, that is, the plunger has not yet moved to the initial position.

2. The initial position positioning device for a plunger pump according to claim 1, characterized in that, The armored cable is a standard three-core armored cable.

3. The initial position positioning device for a plunger pump according to claim 1, characterized in that, The current detection device is a current sensor, which can be connected to any phase of the motor input terminal.

4. The initial position positioning device for a plunger pump according to claim 1, characterized in that, The switch can be any one of a limit switch, reed switch, or contact switch.

Images