A permanent magnet electric submersible piston pump speed reduction control method, device and system

Abstract

The application discloses a permanent magnet electric submersible plunger pump deceleration control method, device and system. The method comprises the following steps: in the current operation period, when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point, the driving current frequency of the motor is reduced to make the plunger of the permanent magnet electric submersible plunger pump decelerate to the target limit position; wherein, if the current operation period is the first operation period, the rotor angle corresponding to the deceleration point is determined based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle; otherwise, the rotor angle corresponding to the deceleration point is determined based on the rotor angle corresponding to the deceleration point in the last operation period and the error angle. The rotor angle corresponding to the deceleration point can be accurately positioned, the accurate control of the upper and lower limit positions of the plunger pump is realized, and the occurrence of the top and bottom collision phenomena can be effectively avoided or reduced in the operation process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, in particular to a permanent magnet electric submersible plunger pump deceleration control method, device and system. BACKGROUND

[0002] In oil well exploitation, the permanent magnet electric submersible plunger pump is a high-efficiency fluid conveying device combining permanent magnet motor, electric submersible structure and plunger pump body, which realizes the pumping of downhole fluid by converting the rotary motion of the permanent magnet synchronous motor into the reciprocating motion of the plunger pump body.

[0003] Under the traditional control strategy, the permanent magnet electric submersible plunger pump has some problems, 1) in the plunger pump body, when the plunger moves to the upper and lower limit positions of the pump body, the top or bottom collision phenomenon is formed; the mechanical structure limitation causes the motor to be unable to continue rotating, the mechanical impact force is large, and the service life of the permanent magnet electric submersible plunger pump is seriously affected; 2) frequent mechanical impact can accelerate the damage of parts, increase the failure rate of the permanent magnet electric submersible plunger pump, and also increase the maintenance cost.

[0004] In order to solve the above problems, the following measures can be taken:

[0005] 1) install a spring at the upper and lower limit positions to buffer the mechanical impact, although it can prolong the service life to a certain extent, but it cannot fundamentally avoid the impact at the limit position;

[0006] 2) detect the sudden increase of current to determine whether the plunger reaches the upper and lower limit positions of the pump body, determine the average time of multiple strokes of the plunger in the pump body based on the detection result, estimate the time when the plunger approaches the upper and lower limit positions, and decelerate in advance at this time, or cut off the drive of the permanent magnet synchronous motor when the sudden increase of current is detected to reduce the mechanical impact. Among them, the sudden increase of stator current when the plunger reaches the upper and lower limit positions of the pump body is due to the limitation of the plunger at the upper and lower limit positions of the pump body, so that the rotor of the permanent magnet synchronous motor is forced to stop rotating and enters the locked-rotor state, resulting in the instantaneous increase of the stator current. SUMMARY

[0007] Using the sudden increase of current to determine whether the plunger reaches the upper and lower limit positions of the pump body, due to the complex current fluctuation and the non-timely response, there is an error in determining whether the plunger reaches the upper and lower limit positions of the pump body, which further leads to inaccurate estimation of the time when the plunger approaches the upper and lower limit positions, and cannot accurately decelerate in advance to avoid the mechanical impact of the plunger pump at the upper and lower limit positions.

[0008] In view of the above problems, the present application is proposed in order to provide a permanent magnet electric submersible plunger pump deceleration control method, device and system which can overcome the above problems or at least partially solve the above problems.

[0009] The embodiment of the present application provides a permanent magnet electric submersible plunger pump deceleration control method, comprising:

[0010] In the current operation cycle, when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point, the driving current frequency of the motor is reduced to make the plunger of the permanent magnet electric submersible plunger pump decelerate to reach the target limit position; wherein, if the current operation cycle is the first operation cycle, the rotor angle corresponding to the deceleration point is determined based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle;

[0011] Otherwise, the rotor angle corresponding to the deceleration point is determined based on the rotor angle corresponding to the deceleration point in the last operation cycle and the error angle; wherein, the determination process of the error angle corresponding to the deceleration point in the last operation cycle comprises:

[0012] The theoretical rotor angle corresponding to the preset correction point is determined, and the time interval required for the motor to run from the starting angle of the current operation cycle to the theoretical rotor angle is determined; wherein, if the last operation cycle is the first operation cycle, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, otherwise, it is the correction rotor angle corresponding to the correction point in the last operation cycle of the last operation cycle;

[0013] After the motor runs for the time interval from the starting angle, the stator voltage is increased to a preset amplitude within a preset time; based on the increased stator voltage and the collected corresponding current, and the electromagnetic characteristic parameters of the motor, the correction rotor angle corresponding to the correction point is determined by using the voltage equation; the error angle is determined based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle.

[0014] In some optional embodiments, the self-learning process of the plunger running in the pump body comprises:

[0015] The permanent magnet electric submersible plunger pump is started and the change of the motor current is monitored in real time, the time when the plunger reaches the top and the bottom of the pump body is identified by judging whether the current increment reaches a preset threshold, and the first motor rotor angle corresponding to the time when the plunger reaches the top of the pump body and the second motor rotor angle corresponding to the time when the plunger reaches the bottom of the pump body are recorded.

[0016] In some optional embodiments, the determination of the rotor angle corresponding to the deceleration point based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle comprises:

[0017] The difference between the first motor rotor angle and the second motor rotor angle is determined;

[0018] Based on the difference and the distance between the top and the bottom of the pump body, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body is determined;

[0019] determining the rotor angle corresponding to the deceleration point based on a distance between the deceleration point and the target limit position, a running angle of the motor rotor corresponding to a unit distance of the pump body, and a rotor angle corresponding to the target limit position reached by the plunger.

[0020] In some optional embodiments, the determining the rotor angle corresponding to the deceleration point based on a distance between the deceleration point and the target limit position, a running angle of the motor rotor corresponding to a unit distance of the pump body, and a rotor angle corresponding to the target limit position reached by the plunger includes:

[0021] If the deceleration point is set at a preset distance from the top of the pump body, determining the rotor angle corresponding to the deceleration point based on a distance between the deceleration point and the top of the pump body, a running angle of the motor rotor corresponding to a unit distance of the pump body, and a rotor angle corresponding to the top of the pump body reached by the plunger;

[0022] If the deceleration point is set at a preset distance from the bottom of the pump body, determining the rotor angle corresponding to the deceleration point based on a distance between the deceleration point and the bottom of the pump body, a running angle of the motor rotor corresponding to a unit distance of the pump body, and a rotor angle corresponding to the bottom of the pump body reached by the plunger.

[0023] In some optional embodiments, if the last running cycle is the first running cycle, the determining the theoretical rotor angle corresponding to the correction point based on the self-learning result includes:

[0024] determining a difference between the first motor rotor angle and the second motor rotor angle;

[0025] determining a running angle of the motor rotor corresponding to a unit distance of the pump body based on the difference and a distance between the top and the bottom of the pump body;

[0026] determining the rotor angle corresponding to the correction point based on a distance between the correction point and the target limit position, a running angle of the motor rotor corresponding to a unit distance of the pump body, and a rotor angle corresponding to the target limit position reached by the plunger.

[0027] In some optional embodiments, the determining the time interval required for the motor to run from the starting angle of the current running cycle to the theoretical rotor angle includes:

[0028] determining an angle interval for the motor to run from the starting angle of the current running cycle to the theoretical rotor angle;

[0029] determining the time interval required for the motor to run from the starting angle to the theoretical rotor angle based on the angle interval and a running speed of the motor rotor.

[0030] In some optional embodiments, the increasing the stator voltage to the preset amplitude within the preset time comprises:

[0031] The stator voltage is increased by 60-70% of the maximum output voltage of the frequency converter within the preset time interval.

[0032] In some optional embodiments, the determining the correction rotor angle corresponding to the correction point based on the increased stator voltage and the corresponding current, and the electromagnetic characteristic parameters of the motor, comprises:

[0033] The voltage equation of the permanent magnet synchronous motor is converted into a d-axis voltage equation and a q-axis voltage equation in the d-q coordinate system;

[0034] The d-axis back electromotive force vector component is determined based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed, by using the d-axis voltage equation.

[0035] The q-axis back electromotive force vector component is determined based on the component of the increased stator voltage on the q-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed, by using the q-axis voltage equation.

[0036] The correction rotor angle corresponding to the correction point is determined based on the d-axis back electromotive force vector component and the q-axis back electromotive force vector component.

[0037] In some optional embodiments, the determining the d-axis back electromotive force vector component based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed, comprises:

[0038] The d-axis back electromotive force vector component is determined based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed, by using the following formula:

[0039]

[0040] wherein, represents the d-axis back electromotive force vector component, represents the voltage component of the increased voltage on the d-axis, represents the stator resistance, represents the current component of the corresponding current on the d-axis after the voltage is increased, represents the d-axis stator inductance component, represents the q-axis stator inductance component, It indicates the current component on the q axis corresponding to the voltage increase. Indicates the rotor speed.

[0041] In some optional embodiments, determining the q-axis back electromotive force vector component using the q-axis voltage equation based on the increased stator voltage component on the q-axis, the corresponding stator current components on the d-axis and q-axis, the stator resistance, the stator inductance components on the d-axis and q-axis, and the rotor speed includes:

[0042] Based on the increased stator voltage component on the q-axis, the corresponding stator current components on the d-axis and q-axis, the stator resistance, the stator inductance components on the d-axis and q-axis, and the rotor speed, the q-axis back EMF vector component is determined using the following formula:

[0043]

[0044] in, represents the q-axis back EMF vector component, It represents the voltage component of the increased voltage on the q axis, represents the stator resistance, It indicates the current component on the q axis corresponding to the voltage increase. represents the d-axis stator inductance component, represents the q-axis stator inductance component, It represents the current component on the d-axis corresponding to the current after the voltage increases. Indicates the rotor speed.

[0045] In some optional embodiments, determining the correction rotor angle corresponding to the correction point based on the d-axis back electromotive force vector component and the q-axis back electromotive force vector component includes:

[0046] determining a ratio of the d-axis back electromotive force vector component to the q-axis back electromotive force vector component;

[0047] Determine the arc tangent value of the ratio and obtain the correction rotor angle corresponding to the correction point.

[0048] In some optional embodiments, the arc tangent value of the ratio is determined to obtain the correction rotor angle corresponding to the correction point, which is specifically implemented using the following formula:

[0049]

[0050] in, represents the d-axis back EMF vector component, represents the q-axis back EMF vector component, Indicates the corrected rotor angle.

[0051] In some optional embodiments, further comprising: before determining the correction rotor angle corresponding to the correction point, filtering the corresponding current collected after the stator voltage is increased by a Kalman filtering method.

[0052] The embodiment of the present application also provides a permanent magnet electric submersible plunger pump deceleration control device, comprising:

[0053] The determining module is configured to determine the rotor angle corresponding to the deceleration point in the current operation period, and specifically comprises: if the current operation period is the first operation period, determining the rotor angle corresponding to the deceleration point based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle; otherwise, determining the rotor angle corresponding to the deceleration point based on the rotor angle corresponding to the deceleration point in the last operation period and the error angle; wherein the determination process of the error angle corresponding to the deceleration point in the last operation period comprises: determining a theoretical rotor angle corresponding to a preset correction point, and determining a time interval required for the motor to run from a starting angle of the current operation period to the theoretical rotor angle; wherein if the last operation period is the first operation period, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, otherwise, the correction rotor angle corresponding to the correction point in the last operation period of the last operation period; increasing the stator voltage to a preset amplitude within a preset time after the motor runs for the time interval from the starting angle; determining the correction rotor angle corresponding to the correction point based on the increased stator voltage and the corresponding current collected, and the electromagnetic characteristic parameters of the motor; and determining the error angle based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle.

[0054] The control module is configured to, in the current operation period, reduce the driving current frequency of the motor to make the plunger of the permanent magnet electric submersible plunger pump decelerate to the target limit position when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point.

[0055] The embodiment of the present application also provides a permanent magnet electric submersible plunger pump deceleration control system, comprising:

[0056] The permanent magnet synchronous motor is configured to convert electrical energy into mechanical energy to provide power for the plunger pump body.

[0057] The plunger pump body is configured to realize the reciprocating motion of the plunger in the pump body under the action of the permanent magnet synchronous motor.

[0058] The permanent magnet electric submersible plunger pump deceleration control device as described above is configured to determine the rotor angle corresponding to the deceleration point in the current operation period, and reduce the driving current frequency of the motor when the angle of the motor rotor is in a state consistent with the rotor angle.

[0059] The embodiment of the present application provides the above technical solutions, and the beneficial effects at least include:

[0060] The corresponding deceleration point is set at a preset distance of the limit position of the permanent magnet electric submersible plunger pump body in advance, to ensure that the plunger is reduced in driving current frequency when moving to the deceleration point, thereby smoothly transitioning to the limit position of the pump body and avoiding impact;

[0061] In determining the rotor angle corresponding to the deceleration point in the current operation cycle, in the first operation cycle, the upper and lower limit positions of the permanent magnet electric submersible plunger pump are self-learned, and based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle of the motor of the permanent magnet electric submersible plunger pump, the rotor angle corresponding to the deceleration point is determined. The process of self-learning the upper and lower limit positions reflects the actual working stroke of the plunger in the pump body, provides a basis for determining the rotor angle corresponding to the deceleration point, and provides a relatively accurate basis for the first deceleration, thereby avoiding large initial errors that may exist in pure theoretical models.

[0062] However, due to the complex current fluctuation and the non-timely response, the rotor angle corresponding to the deceleration point determined based on the self-learning result is not accurate enough, so the preset correction point is used to determine the error angle of the current cycle in each operation cycle. Specifically, the time interval required for the motor to run from the starting angle of the current operation cycle to the theoretical rotor angle corresponding to the correction point is determined. After the motor runs for the time interval from the starting angle, the actual value corresponding to the correction point is calculated in a calculated manner. The actual value corresponding to the correction point is calculated based on the stator voltage, current, and electromagnetic characteristic parameters of the motor using the voltage equation of the permanent magnet synchronous motor. However, due to the long distance of the cable and the increase in resistance caused by the temperature change of the permanent magnet synchronous motor, there is an error in the value of the rotor angle of the motor calculated based on the voltage equation of the permanent magnet synchronous motor. Therefore, after the motor runs for the time interval, the voltage of the motor stator is increased by a preset amplitude within a preset time, thereby further increasing the stator current and the current change rate to compensate for the error caused by the decrease in the value of the rotor angle of the motor due to the increase in the resistance of the cable. Based on the increased stator voltage and the corresponding current collected, and the electromagnetic characteristic parameters of the motor, the correction rotor angle corresponding to the correction point is determined. The error angle is determined based on the theoretical rotor angle and the correction rotor angle of the correction point.

[0063] In subsequent operation cycles, the error angle determined in the last cycle is used to dynamically adjust the rotor angle corresponding to the deceleration point in the current cycle. Under this control strategy, the actual operation state of the system can be continuously learned and adapted, the deviation can be continuously corrected, the accuracy of the rotor angle corresponding to the deceleration point can be significantly improved, thereby achieving accurate and reliable deceleration when the plunger approaches the target limit position, avoiding hard impact, prolonging the service life of the pump, and compensating for errors accumulated over time due to mechanical friction and changes in parameters such as inductance, resistance, and permanent magnet flux of the permanent magnet motor.

[0064] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The purposes and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

[0065] The technical solutions of the present application are described in further detail below with the aid of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0066] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of the specification, illustrate embodiments of the present application and are used to explain the present application, but do not limit the present application. In the drawings:

[0067] Figure 1 Flow chart of the permanent magnet electric submersible plunger pump deceleration control method in the embodiment of the present application;

[0068] Figure 2 Flow chart of the rotor angle corresponding to the current running cycle deceleration point determination method in the embodiment of the present application;

[0069] Figure 3 Flow chart of the error angle corresponding to the last running cycle deceleration point determination method in the embodiment of the present application;

[0070] Figure 4 Structural schematic diagram of the permanent magnet electric submersible plunger pump deceleration control device in the embodiment of the present application;

[0071] Figure 5 Structural schematic diagram of the permanent magnet electric submersible plunger pump deceleration control system in the embodiment of the present application. DETAILED DESCRIPTION

[0072] Exemplary embodiments of the present disclosure will be described below in greater detail with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0073] Glossary:

[0074] Motor drive current frequency: refers to the frequency of the alternating current supplied to the motor stator winding, usually expressed in hertz, which directly determines the synchronous speed of the motor.

[0075] In order to solve the problem that the prior art cannot accurately slow down in advance to avoid the phenomenon of the plunger hitting the top or the bottom of the pump body during the operation of the permanent magnet electric submersible plunger pump, the embodiment of the present application provides a permanent magnet electric submersible plunger pump deceleration control method, which sets corresponding deceleration points at a preset distance of each pump body limit position of the permanent magnet electric submersible plunger pump, and sets a correction point; in the first running cycle of the plunger pump, the rotor angle corresponding to the deceleration point is determined based on the self-learning result of the plunger pump, which provides a basis for determining the rotor angle corresponding to the deceleration point; if it is not the first running cycle, the rotor angle of the current running cycle is determined by using the rotor angle of the deceleration point determined in the last cycle and the angle error determined based on the correction point; during the determination of the error angle, it is found that the long distance of the cable and the temperature change of the motor cause the motor stator resistance to increase and be unstable, which affects the calculation of the rotor angle, and the voltage of the motor stator is increased in the form of a short pulse to compensate for the error caused by the unstable resistance; and then through the correction of the rotor angle corresponding to the deceleration point in each running cycle, the accumulation of the rotor angle error corresponding to the deceleration point is avoided, which provides reliable support for the accurate positioning of the deceleration point, and the phenomenon of hitting the top and the bottom that may occur is avoided.

[0076] The embodiment of the present application provides a permanent magnet electric submersible plunger pump deceleration control method, and the flowchart is as shown in Figure 1 The embodiment of the present application provides a permanent magnet electric submersible plunger pump deceleration control method, and the flowchart is as shown in

[0077] In order to effectively avoid the plunger from hitting the top and the bottom of the pump body during the operation of the plunger in the pump body, when the plunger approaches the top and the bottom of the pump body, the driving current frequency of the motor is reduced, so that the plunger slows down to reach the limit position of the pump body, and does not produce violent impact with the limit position of the pump body. Therefore, it is necessary to set deceleration points at positions close to the top of the pump body and positions close to the bottom of the pump body, and to reserve a buffer zone for the plunger to slow down to reach the top and the bottom of the pump body. Specifically, a top deceleration point is set at a first preset distance of the top of the pump body of the permanent magnet electric submersible plunger pump, and a bottom deceleration point is set at a second preset distance of the bottom of the pump body of the permanent magnet electric submersible plunger pump. After the deceleration points are set, the following steps are executed, including:

[0078] Step S1: determining the rotor angle corresponding to the deceleration point in the current running cycle;

[0079] Step S2: in the current running cycle, when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point, the driving current frequency of the motor is reduced to make the plunger of the permanent magnet electric submersible plunger pump slow down to reach the target limit position.

[0080] In some optional embodiments, in the step S1, the rotor angle corresponding to the deceleration point in the current running cycle is determined, and the flowchart is as shown in Figure 2 The embodiment of the present application provides a permanent magnet electric submersible plunger pump deceleration control method, and the flowchart is as shown in

[0081] The plunger of the permanent magnet electric submersible plunger pump reciprocates in the pump body periodically. The first time the plunger moves from the top of the pump body to the bottom of the pump body and then to the top of the pump body, or the first time the plunger moves from the bottom of the pump body to the top of the pump body and then to the bottom of the pump body is regarded as the first running cycle of the plunger in the pump body. When the plunger reaches the limit position, the rotor rotates reversely, and the plunger moves towards the other limit position.

[0082] If the current running cycle is the first running cycle, step S11 is performed: based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle of the motor, the rotor angle corresponding to the deceleration point is determined; otherwise, step S12 is performed: based on the rotor angle corresponding to the deceleration point in the last running cycle and the error angle, the rotor angle corresponding to the deceleration point is determined.

[0083] In some optional embodiments, in step S11, based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle of the motor, the rotor angle corresponding to the deceleration point is determined, including:

[0084] The self-learning process of the plunger running in the pump body is as follows: the permanent magnet electric submersible plunger pump is started, and the change of the motor current is monitored in real time. The time when the plunger reaches the top of the pump body and the bottom of the pump body is identified by determining whether the current increment reaches a preset threshold, and the first motor rotor angle corresponding to the plunger reaching the top of the pump body and the second motor rotor angle corresponding to the plunger reaching the bottom of the pump body are recorded.

[0085] After the self-learning is completed, 1) the difference between the first motor rotor angle and the second motor rotor angle is determined; 2) based on the difference between the first motor rotor angle and the second motor rotor angle, and the distance between the top and the bottom of the pump body, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body is determined; 3) based on the distance between the deceleration point and the target limit position, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the target limit position, the rotor angle corresponding to the deceleration point is determined.

[0086] Specifically, if the deceleration point is the top deceleration point, that is, the deceleration point is set at the first preset distance from the top of the pump body and close to the top of the pump body, the rotor angle corresponding to the deceleration point is determined based on the distance between the deceleration point and the top of the pump body, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the top of the pump body.

[0087] If the deceleration point is the bottom deceleration point, that is, the deceleration point is set at the first preset distance from the bottom of the pump body and close to the bottom of the pump body, the rotor angle corresponding to the deceleration point is determined based on the distance between the deceleration point and the bottom of the pump body, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the bottom of the pump body.

[0088] In some optional embodiments, in step S12, the rotor angle corresponding to the deceleration point is determined based on the rotor angle corresponding to the deceleration point in the last running period and the error angle.

[0089] In this step, the rotor angle corresponding to the deceleration point in the last running period and the error angle corresponding to the deceleration point in the last running period need to be determined to compensate for the error angle of the deceleration point in the next running period and obtain a more accurate rotor angle.

[0090] The rotor angle corresponding to the deceleration point in the last running period is determined based on the learning result if the last running period is the first running period, as described in step S11. Otherwise, the rotor angle corresponding to the deceleration point in the last running period is determined based on the rotor angle and the error angle in the last running period of the current running period. For example, if the last running period is the second running period, the rotor angle corresponding to the deceleration point in the second running period is determined based on the rotor angle and the error angle in the first running period. If the last running period is the third running period, the rotor angle corresponding to the deceleration point in the third running period is determined based on the rotor angle and the error angle in the second running period, and so on.

[0091] The determination process of the error angle corresponding to the deceleration point in the last running period is shown in the flowchart of Figure 3 The determination process of the error angle corresponding to the deceleration point in the last running period is shown in the flowchart of

[0092] A correction point is set at a second preset distance from a target limit position. In each running period, the time interval required for the motor to run from the starting angle of the current running period to the theoretical rotor angle corresponding to the correction point is determined. When the motor runs for the time interval, the correction is triggered.

[0093] Specifically, step S121: determining the theoretical rotor angle corresponding to the preset correction point and determining the time interval required for the motor to run from the starting angle to the theoretical rotor angle corresponding to the correction point.

[0094] Step S122: increasing the stator voltage to a preset amplitude within a preset time when the motor runs for the time interval from the starting angle; determining the correction rotor angle corresponding to the correction point based on the increased stator voltage and the collected corresponding current, and the electromagnetic characteristic parameters of the motor.

[0095] Step S123: determining the error angle based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle.

[0096] In some optional embodiments, in step S121, the theoretical rotor angle corresponding to the preset correction point is determined, and the time interval required for the motor to run from the starting angle to the theoretical rotor angle corresponding to the correction point is determined, specifically including:

[0097] In this step, the theoretical rotor angle corresponding to the correction point of the last running cycle is determined, which is divided into the following two cases:

[0098] Case one: if the last running cycle is the first running cycle, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result; specifically, after the self-learning process in step S11, 1) the difference between the first motor rotor angle and the second motor rotor angle is determined; 2) based on the difference between the first motor rotor angle and the second motor rotor angle, and the distance between the top and bottom of the pump body, the running angle of the motor rotor corresponding to the unit distance of the pump body is determined; 3) based on the distance between the correction point and the target limit position, the running angle of the motor rotor corresponding to the unit distance of the pump body, and the motor rotor angle corresponding to the target limit position reached by the plunger, the rotor angle corresponding to the correction point is determined.

[0099] Case two: if the last running cycle is not the first running cycle, the theoretical rotor angle corresponding to the correction point is the correction rotor angle corresponding to the correction point in the last running cycle of the last running cycle. For example, if the last running cycle is the second running cycle, the theoretical rotor angle corresponding to the correction point of the second running cycle is the correction rotor angle corresponding to the correction point of the first running cycle; if the last running cycle is the third running cycle, the theoretical rotor angle corresponding to the correction point of the third running cycle is the correction rotor angle corresponding to the correction point of the second running cycle, and so on. The determination process of the correction rotor angle corresponding to the correction point during the running process is introduced in step S122.

[0100] After the theoretical rotor angle corresponding to the correction point is determined, the time interval required for the motor to run from the starting angle to the theoretical rotor angle is determined, including:

[0101] determining the angle interval of the motor running from the starting angle of the current running cycle to the theoretical rotor angle; based on the angle interval and the running speed of the motor rotor, the time interval required for the motor to run from the starting angle to the theoretical rotor angle is determined.

[0102] In some optional embodiments, in step S122, after the motor runs for the time interval from the starting angle of the current cycle, the stator voltage is increased to a preset amplitude within a preset time; based on the increased stator voltage and the collected corresponding current, and the electromagnetic characteristic parameters of the motor, the correction rotor angle corresponding to the correction point is determined, specifically including:

[0103] Step S1221: within a preset time interval, the stator voltage is increased to 60%-70% of the maximum output voltage of the input voltage of the frequency converter. Optionally, the voltage of the motor stator is increased to a preset amplitude within 0.3 ms.

[0104] In the application process of the permanent magnet electric submersible piston pump, the motor stator resistance increases and is unstable due to the long distance of the cable and the temperature change of the motor. If the motor rotor angle corresponding to the correction point is directly determined by using the voltage equation based on the current and voltage corresponding to the current collected correction point, the back electromotive force vector obtained will be small due to the increase of the motor stator resistance, and it is difficult to accurately determine the motor rotor angle corresponding to the correction point. In order to overcome this problem, the voltage of the motor stator is increased in the form of a short pulse, and the corresponding stator current and current change rate are also increased, which reduces the error of the back electromotive force vector, makes up for the decrease of the back electromotive force vector caused by the increase of the resistance, and improves the identification accuracy of the motor rotor angle, thereby ensuring the realization of the rotor angle correction function corresponding to the correction point.

[0105] Wherein, after the short-time pulse injection, the voltage mutation and current mutation will be instantaneously sampled, but because the pulse time is extremely short, the torque generated is not enough to overcome the load inertia and friction, and the rotor cannot respond to the short-time torque fluctuation within milliseconds, so the rotor position is almost unchanged. Therefore, the increase of the voltage mainly affects the transient response of the stator voltage and the stator current, so as to improve the determination accuracy of the motor rotor angle. The increase of the voltage should ensure that the current changes significantly, and the motor rotor should not be driven to move.

[0106] Step S1222: After the voltage is increased, the correction rotor angle corresponding to the correction point is determined based on the increased stator voltage and the collected corresponding current, and the electromagnetic characteristic parameters of the motor by using the voltage equation, the electromagnetic characteristic parameters include static electromagnetic parameters and dynamic electromagnetic parameters, the static electromagnetic parameters include stator resistance and stator inductance, and the dynamic electromagnetic parameters include rotor, specifically including:

[0107] 1) The voltage equation of the permanent magnet synchronous motor is converted into the d-axis voltage equation and the q-axis voltage equation in the d-q coordinate system;

[0108] The d-axis voltage equation is:

[0109]

[0110] Wherein, represents the d-axis back electromotive force vector component, represents the d-axis stator voltage component, represents the stator resistance, represents the d-axis stator current component, represents the d-axis stator inductance component, represents the q-axis stator inductance component, represents the q-axis stator current component, represents the rotor speed;

[0111] The q-axis voltage equation is:

[0112]

[0113] wherein, represents a q-axis back EMF vector component, represents a q-axis stator voltage component, represents a stator resistance, represents a q-axis stator current component, represents a d-axis stator inductance component, represents a d-axis stator current component, represents a q-axis stator inductance component, represents a rotor speed.

[0114] 2) based on the component of the increased stator voltage on the d-axis, the corresponding stator current components on the d-axis and the q-axis, the stator resistance, the stator inductance components on the d-axis and the q-axis, and the rotor speed, the d-axis voltage equation is used to determine the d-axis back EMF vector component; specifically, the following d-axis voltage equation is used to achieve:

[0115]

[0116] wherein, represents a d-axis back EMF vector component, represents the voltage component of the increased voltage on the d-axis, represents a stator resistance, represents the current component of the corresponding current on the d-axis after the voltage is increased, represents a d-axis stator inductance component, represents a q-axis stator inductance component, represents the current component of the corresponding current on the q-axis after the voltage is increased, represents a rotor speed.

[0117] 3) based on the component of the increased stator voltage on the q-axis, the corresponding stator current components on the d-axis and the q-axis, the stator resistance, the stator inductance components on the d-axis and the q-axis, and the rotor speed, the q-axis voltage equation is used to determine the q-axis back EMF vector component; specifically, the following q-axis voltage equation is used to achieve:

[0118]

[0119] wherein, represents a q-axis back EMF vector component, represents the voltage component of the increased voltage on the q-axis, represents a stator resistance, represents the current component of the corresponding current on the q-axis after the voltage is increased, represents a d-axis stator inductance component, represents a q-axis stator inductance component, represents the current component of the corresponding current on the d-axis after the voltage is increased, Indicates the rotor speed.

[0120] 4) determining a correction rotor angle corresponding to the correction point based on the d-axis back electromotive force vector component and the q-axis back electromotive force vector component;

[0121] Determine the ratio of the d-axis back-electromotive force vector component to the q-axis back-electromotive force vector component; determine the arc tangent of the ratio to obtain the correction rotor angle corresponding to the correction point, which is specifically achieved using the following formula:

[0122]

[0123] in, represents the d-axis back EMF vector component, represents the q-axis back EMF vector component, Indicates the corrected rotor angle.

[0124] In some optional embodiments, since there is noise in the current sampling data, before executing step S1222, Kalman filtering is performed on the corresponding current sampled after the voltage is increased. This can effectively suppress measurement noise and disturbance noise and improve the accuracy of the motor rotor angle. Specifically, the following steps are performed:

[0125] 1) Selecting a d-axis stator current component, a q-axis stator current component, a rotor speed, and a rotor angle as state variables; establishing state equations and output equations for the state variables, and initializing the state variables;

[0126] 2) Discretize the state equation and add the system noise to obtain the discretized state equation, discretize the output equation and add the measurement noise to obtain the discretized output equation; and initialize the covariance of the system noise and the covariance of the measurement noise respectively;

[0127] 3) Based on the optimal state estimate at the previous moment and the actual applied voltage, the discretized state equation is used to predict the estimated values ​​of the stator current, rotor speed, and rotor angle at the current moment, and the error covariance of this state prediction is estimated. The expected current measurement value is determined using the predicted state estimate at the current moment and the discretized output equation.

[0128] 4) Fusion update based on the expected current measurement value at the current moment and the actual current collected, including:

[0129] ① Calculate the residual between the expected current measurement value at the current moment and the actual current collected;

[0130] ② Dynamically calculate the Kalman gain matrix based on the covariance of the current state prediction error and the covariance of the measurement noise;

[0131] ③Fusing the predicted stator current and the collected stator current at the current time based on the Kalman gain matrix to obtain the optimal stator current at the current time, that is, the filtered stator current value.

[0132] In some optional embodiments, in the current operation cycle, when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point, the driving current frequency of the motor is reduced to decelerate the plunger of the permanent magnet electric submersible plunger pump to the target limit position. The current frequency of the permanent magnet synchronous motor and the mechanical rotating speed of the rotor are in a proportional relationship, and when the driving current frequency of the motor is reduced, the rotating speed of the rotor is reduced, thereby realizing the deceleration of the plunger in the pump body.

[0133] In some optional embodiments, if abnormal current, abnormal vibration or failure to normally identify the rotor angle corresponding to the deceleration point occurs in the operation process of the plunger pump, the reciprocating motion of the plunger pump is stopped by emergency braking to prevent damage to the equipment.

[0134] In the method of the embodiment, the influence of short-time voltage pulse reduction and instability on the rotor angle is reduced, and the Kalman filtering method is used to suppress the interference of noise in the collected current, thereby realizing the correction of the rotor angle corresponding to each deceleration point, overcoming the problems of response lag or inaccuracy of the traditional method, improving the accuracy of positioning of the deceleration point, and using the characteristics that the rotating speed of the permanent magnet synchronous motor is consistent with the current frequency. When the rotor angle corresponding to the deceleration point is positioned, the driving current frequency of the motor is reduced to decelerate the plunger to the target limit position corresponding to the deceleration point, thereby effectively avoiding or reducing the “top collision” and “bottom collision” phenomenon in the operation process, improving the safety and stability of the system operation, and significantly prolonging the service life of the plunger pump.

[0135] Embodiment two:

[0136] The embodiment two of the present application provides a specific implementation process of a permanent magnet electric submersible plunger pump deceleration control method, which comprises the following steps:

[0137] 1) A bottom deceleration point is arranged at a first preset distance at the bottom of the pump body, and a correction point is arranged at a second preset distance; a top deceleration point is arranged at a first preset distance at the top of the pump body; wherein the first preset distance is greater than the second preset distance.

[0138] In each operation cycle, when the plunger runs from the top to the bottom and passes through the correction point, the correction is triggered.

[0139] 2) A self-learning process of the running of the plunger in the pump body is performed to obtain a self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle of the motor. The specific process is shown in the self-learning process in step S11 in embodiment one.

[0140] 3) In the first running cycle, if the plunger first moves from the top to the bottom of the pump body:

[0141] ① Determine the rotor angle corresponding to the bottom deceleration point based on the self-learning result; when the angle of the motor rotor reaches the rotor angle corresponding to the bottom deceleration point, reduce the driving current frequency of the motor to make the plunger of the permanent magnet electric submersible plunger pump decelerate to reach the target limit position;

[0142] ② Determine the theoretical rotor angle corresponding to the correction point based on the self-learning result, and determine the time interval required for the motor to run from the starting angle to the theoretical rotor angle corresponding to the correction point, see step S121 for specific determination process;

[0143] ③ After the motor runs for the time interval from the starting angle, increase the stator voltage to a preset amplitude within a preset time; based on the increased stator voltage and the corresponding current collected, and the electromagnetic characteristic parameters of the motor, determine the correction rotor angle corresponding to the correction point, see step S122 for specific determination process; wherein the corresponding current collected after the stator voltage is increased can be filtered and processed before calculating the correction rotor angle, to improve the accuracy of the correction rotor angle;

[0144] Determine the error angle based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle;

[0145] ④ Update the rotor angle corresponding to the bottom of the pump body based on the determined error angle; when the angle of the motor rotor reaches the rotor angle corresponding to the updated target limit position, the motor returns to normal speed and the commutation is completed;

[0146] ⑤ Update the rotor angle corresponding to the top deceleration point after commutation based on the determined error angle; when the angle of the motor rotor reaches the rotor angle, reduce the driving current frequency of the motor to make the plunger of the permanent magnet electric submersible plunger pump decelerate to reach the top of the pump body; optionally, use the rotor angle corresponding to the top deceleration point obtained based on self-learning as the deceleration angle directly in the first running cycle.

[0147] 4) In the second running cycle:

[0148] ① The plunger runs from the top to the bottom: determine the rotor angle corresponding to the deceleration point in the current running cycle based on the error angle of the first running cycle and the rotor angle corresponding to the bottom deceleration point; when the angle of the motor rotor reaches the rotor angle corresponding to the deceleration point in the current running cycle, reduce the driving current frequency of the motor to make the plunger of the permanent magnet electric submersible plunger pump decelerate to reach the target limit position;

[0149] ② Obtain the correction rotor angle corresponding to the correction point in the first running cycle, and determine the time interval required for the motor to run from the starting angle of the current running cycle to the correction rotor angle;

[0150] ③After the motor runs from the starting angle for the time interval, the step of increasing the stator voltage in the first running cycle to correct the rotor angle corresponding to the correction point is repeated, and the error angle of the current running cycle is determined;

[0151] ④The rotor angle corresponding to the bottom of the pump body is updated again based on the error angle determined in the current cycle, and when the angle of the motor rotor reaches the rotor angle corresponding to the updated target limit position, the motor returns to normal speed and the commutation is completed;

[0152] ⑤The updated rotor angle of the top deceleration point of the first running cycle is obtained, and based on the error angle determined in the current cycle, the rotor angle corresponding to the top deceleration point is updated again; when the angle of the motor rotor reaches the rotor angle, the driving current frequency of the motor is reduced to decelerate the plunger of the permanent magnet electric submersible plunger pump to the top of the pump body.

[0153] The above steps are repeated in the subsequent cycle, and the deceleration point rotor angle of the current cycle is dynamically determined using the error angle and the rotor angle corresponding to the deceleration point determined in the last cycle.

[0154] In the embodiment, in the process of determining the correction rotor angle of the correction point, the stator voltage is increased for a short time, the angle recognition is performed in combination with the current response and the electromagnetic characteristic parameters of the motor, the motor itself is ingeniously used as a sensor, physical position sensors which are prone to failure in the harsh environment downhole are not needed, and the long-term operation reliability in harsh working conditions is greatly improved.

[0155] By introducing the correction point, the correction rotor angle of the correction point calculated in each running cycle is compared with the theoretical value, the systematic angle error is calculated, and the error is fed back to the setting of the deceleration point, so that the cumulative error caused by the motor parameter drift, mechanical wear and load change is effectively compensated, and the deceleration accuracy and reliability of the plunger at the target limit position are significantly improved.

[0156] Based on the same inventive concept, the embodiment of the present application also provides a permanent magnet electric submersible plunger pump deceleration control device 10, the structure of the device is as shown in Figure 4 , comprising:

[0157] The determination module 101 is configured to determine the rotor angle corresponding to the deceleration point in the current running cycle, and specifically includes: if the current running cycle is the first running cycle, determining the rotor angle corresponding to the deceleration point based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle; otherwise, determining the rotor angle corresponding to the deceleration point based on the rotor angle corresponding to the deceleration point in the last running cycle and the error angle; wherein the determination process of the error angle corresponding to the deceleration point in the last running cycle comprises:

[0158] determine a theoretical rotor angle corresponding to the preset correction point, and determine a time interval required for the motor to run from a starting angle of a current operation cycle to the theoretical rotor angle;wherein if a previous operation cycle is a first operation cycle, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, otherwise, is a correction rotor angle corresponding to the correction point in a previous operation cycle of the previous operation cycle;

[0159] after the motor runs for the time interval from the starting angle, increase the stator voltage to a preset amplitude within a preset time;determine a correction rotor angle corresponding to the correction point based on the increased stator voltage and the collected corresponding current, and electromagnetic characteristic parameters of the motor;determine an error angle based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle.

[0160] The control module 102 is configured to, in a current operation cycle, when an angle of a rotor of the motor reaches a rotor angle corresponding to a preset deceleration point, reduce a driving current frequency of the motor to decelerate a plunger of the permanent magnet electric submersible plunger pump to reach a target limit position.

[0161] The embodiment of the present application also provides a permanent magnet electric submersible plunger pump deceleration control system, and a structure of the system is shown in Figure 5 The system comprises:

[0162] The permanent magnet electric submersible plunger pump 20 is configured to realize reciprocating movement of the plunger in the pump body under the action of the permanent magnet synchronous motor.

[0163] The permanent magnet electric submersible plunger pump deceleration control device 10 described above is configured to determine a rotor angle corresponding to a deceleration point in a current operation cycle, and reduce a driving current frequency of the motor when an angle of a rotor of the motor is in a state consistent with the rotor angle.

[0164] As to the permanent magnet electric submersible plunger pump deceleration control device in the above embodiment, the specific manner in which each module performs the operation has been described in detail in the embodiment related to the method, and will not be described in detail here.

[0165] The above method and device of the embodiment of the present application no longer rely on mechanical springs or simply current threshold to determine the position of the deceleration point, can effectively reduce mechanical impact caused by "striking the top" and "striking the bottom", and adapt to working conditions of the plunger pump under different well depths and different load conditions.

[0166] Unless specifically stated otherwise, terms such as processing, computing, calculating, determining, displaying, and the like, can refer to an action or process of one or more processing or computing systems, or similar devices, that manipulate or transform data represented as physical (e.g., electronic) quantities within the systems' registers or memories into other data similarly represented as physical quantities within the systems' memories, registers or other such information storage, transmission or display devices. The terms "information," "data," "instructions," “command,” “signal,” “bit,” “symbol,” and the like refer to physical quantities presumed to represent a pertinent physical reality.

[0167] It should be understood that the particular order in which the steps in the disclosed processes have been presented is exemplary. Based on design preferences, it is understood that the particular order of steps in the processes can be rearranged without departing from the scope of the disclosure. The accompanying method claims present elements of the various steps in exemplary order and are not meant to be limited to the specific order or hierarchy presented.

[0168] In the above detailed description, various features are grouped together in single embodiments for the purpose of streamlining the disclosure. This disclosed approach is not to be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are expressly recited in each claim. Rather, as the claims below reflect, inventive subject matter lies in fewer than all features of the disclosed single embodiments. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate preferred embodiment.

[0169] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0170] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor and the storage medium can reside as discrete components in a user terminal.

[0171] For a software implementation, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes can be stored in memory units and executed by processors. The memory unit can be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

[0172] The above description includes one or more examples of the embodiments. Of course, not all possible combinations of components or methods described above can be claimed as embodiments. One of ordinary skill in the art can recognize that modifications and variations of the described embodiments can be made without departing from the scope of the present disclosure. It is therefore intended that the embodiments described herein be considered in all respects as illustrative and not restrictive, particularly as numerous modifications and further embodiments can become apparent to those skilled in the art. Accordingly, the scope of the present disclosure is intended to be defined by the following claims rather than the description. Moreover, the use of the terms "first", "second", etc. do not denote any order or importance, but rather the terms are used to distinguish one element from another. Furthermore, the use of the terms "including", "containing", etc. are meant to encompass the terms "consisting of" and / or "consisting essentially of". Moreover, the use of the term "or" is meant to encompass "and / or", unless otherwise indicated.

Claims

1. A method of permanent magnet submersible plunger pump speed reduction control, characterized by, Comprise: In the current running cycle, when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point, the frequency of the motor driving current is reduced to decelerate the plunger of the permanent magnet electric submersible plunger pump to the target limit position; wherein, if the current running cycle is the first running cycle, the rotor angle corresponding to the deceleration point is determined based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle; Otherwise, the rotor angle corresponding to the deceleration point is determined based on the rotor angle corresponding to the deceleration point in the last running cycle and the error angle; wherein, the determination process of the error angle corresponding to the deceleration point in the last running cycle comprises: Determine the theoretical rotor angle corresponding to the preset correction point, and determine the time interval required for the motor to run from the starting angle of the current running cycle to the theoretical rotor angle; wherein, if the last running cycle is the first running cycle, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, otherwise, it is the correction rotor angle corresponding to the correction point in the last running cycle of the last running cycle of the last running cycle. After the motor runs for the time interval from the starting angle, the stator voltage is increased to a preset amplitude within a preset time; based on the increased stator voltage and the collected corresponding current, and the electromagnetic characteristic parameters of the motor, the correction rotor angle corresponding to the correction point is determined by using the voltage equation; the error angle is determined based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle.

2. The method of claim 1, wherein, The self-learning process of the plunger running in the pump body comprises: Start the permanent magnet electric submersible plunger pump and monitor the change of motor current in real time, identify the time when the plunger reaches the top and bottom of the pump body by judging whether the current increment reaches a preset threshold, and record the first motor rotor angle corresponding to the plunger reaching the top of the pump body, and the second motor rotor angle corresponding to the plunger reaching the bottom of the pump body.

3. The method of claim 1, wherein, The determination of the rotor angle corresponding to the deceleration point based on the self-learning result of the running position of the plunger in the pump body and the corresponding rotor angle comprises: Determine the difference between the first motor rotor angle and the second motor rotor angle; Based on the difference and the distance between the top and bottom of the pump body, determine the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body; Based on the distance between the deceleration point and the target limit position, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the target limit position, determine the rotor angle corresponding to the deceleration point.

4. The method of claim 3, wherein, The determination of the rotor angle corresponding to the deceleration point based on the distance between the deceleration point and the target limit position, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the target limit position comprises: If the deceleration point is set at a preset distance from the top of the pump body, the rotor angle corresponding to the deceleration point is determined based on the distance between the deceleration point and the top of the pump body, the running angle of the motor rotor corresponding to the unit distance of the plunger running in the pump body, and the motor rotor angle corresponding to the plunger reaching the top of the pump body; If the deceleration point is set at a preset distance from the bottom of the pump body, a rotor angle corresponding to the deceleration point is determined based on a distance between the deceleration point and the bottom of the pump body, an angle of rotation of the motor rotor corresponding to a unit distance of the pump body, and an angle of the motor rotor corresponding to the bottom of the pump body.

5. The method of claim 2, wherein, If the last operation cycle is the first operation cycle, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, including: determining a difference between the first motor rotor angle and the second motor rotor angle; determining an angle of rotation of the motor rotor corresponding to a unit distance of the pump body based on the difference and a distance between the top and the bottom of the pump body; determining a rotor angle corresponding to the correction point based on a distance between the correction point and the target limit position, an angle of rotation of the motor rotor corresponding to a unit distance of the pump body, and an angle of the motor rotor corresponding to the target limit position.

6. The method of claim 1, wherein, The time interval required for the motor to run from the starting angle of the current operation cycle to the theoretical rotor angle includes: determining an angle interval for the motor to run from the starting angle of the current operation cycle to the theoretical rotor angle; determining the time interval required for the motor to run from the starting angle to the theoretical rotor angle based on the angle interval and the speed of rotation of the motor rotor.

7. The method of claim 1, wherein, The step of increasing the stator voltage to a preset amplitude within a preset time includes: increasing the stator voltage by 60%-70% of the maximum output voltage of the frequency converter within a preset time interval.

8. The method of claim 1, wherein, The step of determining the correction rotor angle corresponding to the correction point based on the increased stator voltage and the corresponding current, and the electromagnetic characteristic parameters of the motor, using the voltage equation includes: transforming the voltage equation of the permanent magnet synchronous motor into a d-axis voltage equation and a q-axis voltage equation in the d-q coordinate system; determining a d-axis back electromotive force vector component using the d-axis voltage equation based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed; determining a q-axis back electromotive force vector component using the q-axis voltage equation based on the component of the increased stator voltage on the q-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed; determining the correction rotor angle corresponding to the correction point based on the d-axis back electromotive force vector component and the q-axis back electromotive force vector component.

9. The method of claim 8, wherein, The step of determining the d-axis back electromotive force vector component using the d-axis voltage equation based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed includes: determining the d-axis back electromotive force vector component using the following formula based on the component of the increased stator voltage on the d-axis, the components of the corresponding stator current on the d-axis and the q-axis, the stator resistance, the components of the stator inductance on the d-axis and the q-axis, and the rotor speed: ； wherein, represents a d-axis back electromotive force vector component, represents a voltage component of the increased voltage in the d-axis, represents a stator resistance, represents a current component of the current corresponding to the increased voltage in the d-axis, represents a d-axis stator inductance component, represents a q-axis stator inductance component, represents a current component of the current corresponding to the increased voltage in the q-axis, represents a rotor rotational speed.

10. The method of claim 8, wherein, The q-axis voltage equation is determined based on the increased stator voltage component on the q-axis, corresponding stator current components on the d-axis and q-axis, stator resistance, stator inductance components on the d-axis and q-axis, and rotor speed, and the q-axis back electromotive force vector component is determined by using the q-axis voltage equation, including: The q-axis back electromotive force vector component is determined based on the increased stator voltage component on the q-axis, corresponding stator current components on the d-axis and q-axis, stator resistance, stator inductance components on the d-axis and q-axis, and rotor speed, and the q-axis back electromotive force vector component is determined by using the q-axis voltage equation, including: ； wherein, represents a q-axis back electromotive force vector component, represents a voltage component of the increased voltage in the q-axis, represents a stator resistance, represents a current component of the corresponding current in the q-axis after the voltage is increased, represents a d-axis stator inductance component, represents a q-axis stator inductance component, represents a current component of the corresponding current in the d-axis after the voltage is increased, represents a rotor rotational speed.

11. The method of claim 8, wherein, The correction rotor angle corresponding to the correction point is determined based on the d-axis back electromotive force vector component and the q-axis back electromotive force vector component, including: The ratio of the d-axis back electromotive force vector component to the q-axis back electromotive force vector component is determined; The inverse tangent value of the ratio is determined to obtain the correction rotor angle corresponding to the correction point.

12. The method of claim 11, wherein, The inverse tangent value of the ratio is determined to obtain the correction rotor angle corresponding to the correction point, and the inverse tangent value of the ratio is determined by using the following formula: ； wherein, represents a d-axis back electromotive force vector component, represents a q-axis back electromotive force vector component, represents a corrected rotor angle.

13. The method of claim 1, wherein, Further comprising: Before determining the correction rotor angle corresponding to the correction point, the corresponding current collected after the stator voltage is increased is filtered by using a Kalman filtering method.

14. A permanent magnet submersible plunger pump speed reduction control apparatus, characterized by, Including: The determination module is configured to determine the rotor angle corresponding to the deceleration point in the current operation period, and specifically includes: if the current operation period is the first operation period, determining the rotor angle corresponding to the deceleration point based on the running position of the plunger in the pump body and the self-learning result of the corresponding rotor angle; otherwise, determining the rotor angle corresponding to the deceleration point based on the rotor angle corresponding to the deceleration point in the last operation period and the error angle; wherein, the determination process of the error angle corresponding to the deceleration point in the last operation period includes: determining the theoretical rotor angle corresponding to a preset correction point, and determining the time interval required for the motor to run from the starting angle of the current operation period to the theoretical rotor angle; wherein, if the last operation period is the first operation period, the theoretical rotor angle corresponding to the correction point is determined based on the self-learning result, otherwise, the theoretical rotor angle corresponding to the correction point in the last operation period is the correction rotor angle corresponding to the correction point in the last operation period; after the motor runs for the time interval from the starting angle, the stator voltage is increased to a preset amplitude within a preset time; determining the correction rotor angle corresponding to the correction point based on the increased stator voltage, the collected corresponding current, and the electromagnetic characteristic parameters of the motor; and determining the error angle based on the theoretical rotor angle corresponding to the correction point and the correction rotor angle; The control module is configured to, in the current operation period, reduce the driving current frequency of the motor to make the plunger of the permanent magnet electric submersible plunger pump decelerate to the target limit position when the angle of the motor rotor reaches the rotor angle corresponding to the preset deceleration point.

15. A permanent magnet submersible plunger pump speed reduction control system characterized by, Including: The permanent magnet synchronous motor is configured to convert electrical energy into mechanical energy to provide power for the plunger pump body; The plunger pump body is configured to realize the reciprocating motion of the plunger in the pump body under the action of the permanent magnet synchronous motor; The permanent magnet electric submersible plunger pump deceleration control device of claim 14 is configured to determine the rotor angle corresponding to the deceleration point in the current operation period, and reduce the driving current frequency of the motor when the angle of the motor rotor is in a state consistent with the rotor angle.

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