EP1935087A1

EP1935087A1 - Electromechanical driving system, in particular for progressive cavity pump for oil well

Info

Publication number: EP1935087A1
Application number: EP06820284A
Authority: EP
Inventors: Christian Petit
Original assignee: Moteurs Leroy Somer SA
Current assignee: Moteurs Leroy Somer SA
Priority date: 2005-10-12
Filing date: 2006-10-12
Publication date: 2008-06-25
Also published as: WO2007042732A1; FR2891960B1; CN101313459A; US20080246427A1; US7880418B2; FR2891960A1; EA200801051A1; CA2626066C; CA2626066A1; BRPI0617234A2

Abstract

The invention concerns an electromechanical system (1) designed to be connected to a power grid (7), comprising: an electrical machine (2) capable of operating as a stand-alone power generator, including a rotary shaft, and a switching system (9) enabling i) in a first configuration, the machine to operate as motor when the coupled device (4) is normally driven or as generator when the coupled device is normally driving, and ii) in a second configuration, the machine to operate as stand-alone generator, the electric power generated by the electrical machine (2; 22) being dissipated in the machine and in a dissipative load (13).

Description

Electromechanical drive system, especially for progressive cavity pump for oil well

The present invention relates to electrical systems for coupling to driven or driving devices.

The invention relates more particularly, but not exclusively, to driven device drive systems which are capable of storing a relatively large potential energy during their operation.

In case of failure of the power supply of the system, this potential energy is likely to drive the system suddenly in the opposite direction, it is called devilage, and can cause runaway with a speed of deviation reaching values that can be dangerous for people and equipment.

This problem is encountered, for example, with progressive cavity pumps used in oil wells.

Such pumps store in operation a potential energy in two forms, namely on the one hand a torsion energy in the drive rod of the pump which is twisted on itself and on the other hand a hydrostatic energy corresponding to the column of fluid in the well.

These pumps are traditionally driven by asynchronous electric motors and pulley systems providing a reduction ratio of about 2 to 5.

A braking device is provided in order to avoid that in the event of engine stopping, the accumulated potential energy suddenly drives the system in the opposite direction.

This device comprises for example a mechanical disk or centrifugal brake or a hydraulic braking device.

Publications WO 99/2477, WO 00/25000, US 2005/0045323, US 6 079 489, US 6 113 355 and US 5 749 416 disclose examples of relatively complex braking devices.

The patent publication of Japan JP 61 269 686 discloses a system comprising an asynchronous motor for driving a water pump. The engine comprises a wound rotor.

During a braking operation, the windings of the stator flow in a dissipative circuit while the windings of the rotor are fed by the network. Such a system can not work in the event of a power failure, since the motor does not operate as a stand-alone generator.

The invention aims, inter alia, to provide an electromechanical system to be coupled to a device for driving and / or driven, to prevent runaway of the system in case of change of operating conditions, including power.

The electromechanical system is for example configured to be coupled to a driven device and comprises a motor.

The driven device is for example a progressive cavity pump rod.

The electromechanical system can still be configured to be coupled to a device driving and include a generator. The driving device is then, for example, a wind turbine.

According to one of its aspects, the subject of the invention is an electromechanical system to be connected to an electrical network, comprising: an electric machine comprising a rotary shaft, and

- a switching system allowing: in a first configuration, that the electric machine operates as a motor in the case where the coupled device is normally driven or generator in the case where the coupled device is normally driving, and in a second configuration, that the electric machine operates as an autonomous generator, the electrical energy generated by the electric machine being dissipated in the machine and in a dissipative load.

The dissipative load that is connected to the machine can provide more or less of the dissipation of energy when the machine operates as a stand-alone generator. A significant part of the dissipation of the energy can take place in the machine itself, in particular in the stator windings, in particular in the case where the dissipative load has no significant impedance and its impedance is substantially less than the internal impedance of the machine.

Accordingly, the term "dissipative load" should not be understood in a limiting sense and the power dissipated in this load can be much lower than that dissipated in the machine. When the machine is short-circuited, most of the energy delivered by the machine is dissipated therein. The dissipative charge is then reduced to the conductors, contacts and / or components that ensure this short circuit. In the case where their internal impedance is very low, the power dissipated in this short circuit will be negligible compared to that dissipated in the machine.

The invention makes it possible to create a braking torque with the electric machine.

The expression "autonomous generator" designates a generator that can operate without external input of electrical energy by the network.

When the electric machine operates as an autonomous generator, the magnetic field generated by the rotor to excite the stator windings may be due to the presence of permanent magnets and / or windings powered by an exciter incorporated in the machine or powered by the current produced by the machine. The machine may be an asynchronous machine whose excitation is provided by one or more capacitors connected to the terminals of the stator.

The electrical machine may comprise, in exemplary embodiments, a rotor with permanent excitation, in particular a rotor with permanent magnets. The use of a permanent magnet machine in particular increases the reliability.

The electromechanical system may comprise no battery intended to constitute an auxiliary source of energy for supplying windings of the electric machine when the latter operates as an autonomous generator, nor any generating unit playing the same role.

When the electric machine comprises a rotor with permanent magnets, the rotor is advantageously flux concentration, comprising permanent magnets engaged between pole pieces. The machine may include permanent magnets which are oriented radially, the polar axis of each magnet being oriented in the circumferential direction.

As a function in particular of the impedance of the dissipative load, the shape of the curve of the braking torque as a function of the speed can be modified and in particular the braking torque can increase until it reaches a maximum for a certain speed of rotation. then decrease. A low dissipative load impedance can make it possible to reach the maximum braking torque relatively quickly. The speed for which the torque is maximum is advantageously for example less than or equal to 50 rpm, better 40 rpm, even better 35 rpm. This can allow a significant braking of the coupled device as soon as the network disappears, and maintain this device coupled to a relatively slow rotation speed.

Even if the braking torque is close to the nominal torque, the energy dissipated remains relatively low because the speed remains relatively slow. This keeps the system in this state without excessive overheating of the machine.

In the case where the coupled device is a pump, in particular an oil well pump, for example of the progressive cavity type, this may allow the column of fluid in the well to empty only very slowly.

As soon as the network reappears, the system can be restarted without being penalized in production by the dead time due to the emptying of the well and its filling.

In exemplary embodiments of the invention, the system may or may not include a gearbox or multiplier between the shaft and a device to be coupled to the electromechanical system.

The presence of a gearbox makes it possible to benefit from inertial braking as well.

The invention can make it possible to reduce the risk of runaway in a relatively simple, reliable and economical way, in the event, for example, of a break in the network to which the system is connected.

When the electric machine is a motor, the switching system can be used to power the motor in the first configuration to drive the coupled device.

The reducer can be a gear reducer, which improves the reliability.

The reduction ratio may be greater than 6, in particular 7 to 15, which makes it possible to use a motor with a relatively high speed of rotation, for example between 2,000 and 9,000 rpm under normal operating conditions.

The system may include the dissipative load. The latter may comprise at least one electrolytic or metallic resistance, for example at least one metal resistor immersed in a bath of a liquid.

The dissipative load may, if necessary, be reduced to short-circuited conductors and have a relatively low impedance substantially less than the internal impedance of the windings of the machine thus short-circuited. This can have as an advantage of ensuring that the machine essentially delivers, when driven by the coupled device, on its own internal impedance.

This can make it possible to obtain a relatively large braking torque for relatively low speeds of rotation, which may be of interest for achieving a significant braking of the coupled device as soon as the network disappears, as mentioned above.

The dissipative load can be connected to the terminals of the machine simply by means of one or more switches, which can be formed by electromechanical relays or by electronic components such as for example thyristors or power transistors.

In exemplary embodiments of the invention, the dissipative load is connected to the machine without the current discharged by the machine when it operates as an autonomous generator circulates in a relatively complex electronic device such as an inverter or a dimmer. The dissipative load can still, in embodiments, be connected to the machine without this connection involving power electronics components.

When the dissipative charge comprises an electrolytic resistance, comprising at least two electrodes immersed in an electrolyte, the level of the electrolyte can be modified in order to vary the impedance.

The switching system can be arranged to automatically switch from the first aforementioned configuration to the second configuration in the event of voluntary cutting or not or failure of the power supply of the electrical machine or the electrical network powered by it and / or stopping the machine.

The switching system may comprise at least one relay comprising a coil, which is for example supplied directly or indirectly by the electrical network.

The switching system may be arranged to remain in the second configuration until a predefined command is received.

The sending of this predefined command depends for example on a voltage observed on the machine, a time delay or a speed of rotation of the machine.

The electrical system may include a frequency converter to which the motor is connected. The predefined command can be sent by the frequency converter, for example. When the machine operates as a stand-alone generator, the frequency converter may not be powered and receive no current from the machine. In the second configuration, the frequency converter is for example disconnected from the electrical machine.

In another embodiment, the system may comprise a machine speed control device, arranged to connect and disconnect the dissipative load so that this speed of unwinding remains between two thresholds that can be predetermined.

The control device can then be arranged to disconnect the load when the minimum speed threshold is reached and to reconnect it when the maximum speed threshold is reached.

The control system of the speed of deviation can also be arranged to act on the current flowing to the dissipative load so that the speed of deviation remains between the two predefined thresholds and / or is substantially constant.

The electromechanical system can thus remain in a predefined speed range as long as the braking torque is greater than the driving torque and the driving torque remains sufficient to accelerate the system.

The invention also relates to a surface drive system of a progressive cavity pump for oil well, comprising: a motor comprising an output shaft,

a reducer, preferably geared, between the output shaft and a drive rod of the pump,

a dissipative charge,

a switching system arranged to allow, in a first configuration, the motor to be supplied by a power supply network in order to drive the pump drive rod in a first direction, and in a second configuration where the output shaft is rotated in a second direction opposite to the first, to transfer electrical energy generated by the engine thus driven to the dissipative load, the switching system being arranged to automatically switch to the second configuration in case cutoff of the electrical network in particular. The electric motor can be connected to a frequency converter.

The reduction ratio may be greater than 6, in particular from 7 to 15.

The motor can be permanent magnets.

The invention further relates, in another of its aspects, to a surface drive system of a progressive cavity pump for oil well, comprising: a motor comprising a stator having windings and a rotor with permanent magnets , in particular a flux-concentration rotor, a switching system arranged to allow, in a first configuration, the motor to be powered, and in a second configuration, to short-circuit the stator windings in case of accidental interruption of the power supply of the motor, for example in the event of a power failure.

The invention will be better understood on reading the detailed description which follows, examples of non-limiting implementation thereof, and on examining the appended drawing, in which:

FIG. 1 is a block diagram of an electromechanical system according to an exemplary implementation of the invention,

FIG. 2 schematically represents a relay of the switching system,

FIG. 3 illustrates the possibility for the dissipative load to comprise several stages of resistances that can be selected,

FIGS. 4 and 9 are block diagrams of other examples of electromechanical systems,

FIGS. 5 and 6 are block diagrams of electromechanical systems comprising a device for controlling the speed of unwinding,

FIG. 7 schematically represents, in cross-section, an example of a rotor with permanent magnets, and

FIG. 8 is an example of a curve of evolution of the braking torque as a function of speed.

The electromechanical system 1 shown in Figure 1 comprises an electric machine 2 comprising an electric motor in the example. This motor comprises for example a stator and a rotor with permanent magnets. The stator is for example concentrated or distributed winding. The rotor comprises for example surface magnets or magnets arranged between polar parts.

FIG. 8 represents an example of rotor 100 with permanent magnets 101, arranged radially between polar pieces 102.

Such a rotor is at a flux concentration, which can make it possible to limit the short-circuit current and reduce the risk of excessive heating and / or the risk of demagnetization of the magnets. The motor is, for example, as described in US Pat. No. 6,891,299. The associated stator may be concentrated or distributed winding.

The electromechanical system 1 also comprises, in the example under consideration, a gear reducer 3, making it possible to reduce the rotational speed of the motor 2 and to drive a driven device 4 which is, for example, a drive rod of a pump. progressive cavity disposed at the bottom of an oil well.

The gearbox 3 for example has a relatively high reduction factor, for example greater than 6, especially between 7 and 15.

The engine 2 is normally powered by a frequency converter 6, which is connected to a power supply network 7.

The motor 2 is powered by the drive 6 through a switching system 9. The latter can take a first configuration in which the motor 2 is powered by the drive 6 and a second configuration in which the motor 2 is connected to a motor. dissipative charge 13.

For example, the switching system 9 comprises at least one electronic and / or electromechanical switch which makes it possible to selectively connect the motor 2 to the converter 6 or the dissipative load 13.

In an exemplary implementation of the invention, the switching system 9 comprises at least one electromechanical relay having a coil 10 and a series of contacts 11.

The series of contacts 11 makes it possible, for example, when the coil 10 is energized, to establish the current flow between sets of conductors 14 and 15 respectively connected to the motor 2 and to the variator 6. In the absence of power supply to the coil, the series of contacts 11 connects the sets of conductors 14 to sets of conductors 17 connected to the dissipative load 13.

The restarting of the machine may, in exemplary embodiments of the invention, be conditioned for example by a speed of rotation of the machine, by a voltage observed on the machine or by a time delay.

For example, the restart can be prevented as long as the speed is not zero or the voltage across the machine is not less than a threshold value.

In the illustrated example, a second series of contacts 12 of the electromechanical relay can be used so that the supply of the coil 10 is through this second series of contacts, which allows, once the supply of the coil 10 has ceased, again to prevent it from being excited until a predefined action is exerted on the switching system 9.

This can prevent a restart of the engine in case of return of the power network 7 after a break, for example.

The predefined command comes for example from the drive 6 but can be done differently, for example by acting manually on a contactor.

The dissipative load 13 may be formed of electrical conductors of low ohmic resistance, in order to short-circuit the terminals of the machine, most of the power to be dissipated then being dissipated in the machine. Alternatively, the dissipative load 13 may have a higher impedance.

The dissipative charge 13 comprises, for example, at least one resistor, which is, for example, a metal or electrolytic resistor.

The metal resistor is advantageously immersed in a bath of non-combustible liquid, which can reduce the risk of fire when the electromechanical system is used in an explosive atmosphere, which may be the case in the vicinity of a well. oil.

The dissipative load 13 may comprise resistors and / or any other passive or active component making it possible to dissipate electrical energy, for example capacitors and / or chokes. The dissipative charge 13 may further comprise an electrolytic resistor comprising at least two electrodes immersed in an electrolyte. If necessary, the level of the electrolyte can be changed to adjust the resistance to the desired value.

The braking torque of the motor is a function of the current flowing through the dissipative load 13 and the choice of the impedance of the dissipative load can make it possible to dissipate the energy appropriately.

For example, the braking torque can be reduced as the pump drive shaft slows down, so that the well can be emptied more quickly.

The dissipative load 13 can for this purpose comprise several resistance resistor stages 20 which can be selectively connected to the motor 2, for example via the switching system 9, as illustrated in FIG. 3, as a function of the rotational speed. of it and / or the voltage at its terminals, for example that the dissipated power is maximum while remaining admissible.

In an exemplary embodiment using an electrolytic resistor, the level of the electrolyte varies with time during braking, for example decreases thanks to a controlled leakage.

The lowering of the electrolyte level increases the resistance and decreases the braking torque. This lowering of the level can be triggered for example during the passage in the second configuration.

The electromechanical system of Figure 1 allows, in case of power failure 7 for example, the motor 2 to be driven in the opposite direction of rotation by the energy accumulated in the driven device.

This rotation can be performed at a relatively high speed, given the reduction ratio of the gear 3, which allows to obtain inertial braking.

The use of gears in the gearbox 3 contributes to ensuring the reliability of the mechanical connection between the driven device 4 and the engine 2.

The rotor drive of the motor 2 generates an electrical energy which is dissipated more or less in the dissipative load 13 and in the motor 2, according to the respective impedances.

The use of a permanent magnet motor contributes to the reliability of the electromechanical system, such a motor having the advantage of having a permanent integrated excitation. The switching system 9 can be arranged to automatically switch to the configuration where the motor 2 is connected to the dissipative load 13, not only in the event of a cut in the electrical network 7, but also in the event of engine shutdown or failure of the engine. inverter 6, for example.

The braking provided by the motor 2 prevents the drive rod of the pump from rotating at an excessive speed. Thus, the accumulated potential energy can be gradually dissipated.

When the motor 2 is an asynchronous motor, excitation capacitors will be connected to its terminals.

The invention also applies to an electric machine 22 which is driven by a driving device 24 such as for example a wind turbine, via a multiplier 3.

In this case, the machine 22 normally operates as a generator and the energy is returned to an electrical network 27.

If this network 27 disappears, the system runs empty and presents a risk of runaway and the switching system 9 can then allow the generator 22 to be fed into the dissipative load 13, which provides a braking torque.

The braking of the driven device 4 or driving 24 can be carried out only by the engine 2 or the generator 22, by causing it to flow into the dissipative load 13, as just explained.

However, it is not beyond the scope of the present invention when the braking of the driven device 4 or driving 24 also involves a different braking device, for example mechanical or hydraulic, which acts for example at the same time as the braking torque exerted by the motor 2 or the generator 22 or in a non-simultaneous manner.

This braking device can for example be activated from a certain rotational speed of the engine 2 or the generator 22.

FIGS. 5 and 6 show electromechanical systems comprising a device 10 for controlling the speed of unwinding.

The dissipative charge 13 is connected to or disconnected from the machine 2 or 22 by the control device 10 by any breaking means, for example at least one contactor or a static electronic switch which may comprise for example a thyristor.

This device 10 is configured so that the speed of rotation of the machine remains between two determined thresholds. Load 13 is disconnected from machine 2 or 22 when the minimum speed threshold is reached. The electromechanical system then in freewheel can accelerate under the effect of the driving torque of the coupled device 4.

When the maximum speed threshold is reached, the load 13 is connected. The coupled device is then braked, the braking torque depending on the current passing through the load 13.

The device 10 thus allows the system to remain in the desired speed range as long as the braking torque is greater than the driving torque and the driving torque remains sufficient to accelerate the system.

Especially in the case of a machine having a permanent magnet rotor, the voltage supplied by the machine is an image of the speed, the switching of the load can be performed depending on the output voltage of the machine when the it works as a generator.

The control device 10 may comprise an electromechanical relay that sticks from a certain voltage corresponding to the speed from which the braking is to be triggered.

The control device 10 may comprise a more complex electronic circuit for setting trip thresholds.

Instead of using logic "all or nothing" type of one or more electronic or electromechanical switches, it is possible to use in the control device 10 a regulator, for example of the PWM chopper type or dimmer, allowing to continuously control the current between the machine 2 or 22 and the dissipative load 13. This may allow a finer regulation of the speed.

When it is desired to exert a relatively high braking torque for a relatively low rotational speed, for example to reduce as much as possible the unwinding speed, it may be useful to choose a dissipative load 13 whose impedance is less than the internal impedance of the machine, in order to obtain a rapid increase in torque as a function of speed, as illustrated in FIG. 7. For example, a maximum braking torque can be obtained for a speed of rotation less than or equal to 50 rpm, for example of the order of 30 rpm. In such an example where the dissipative load has a low impedance, the rotor is for example permanent magnets and flux concentration.

In the variant of Figure 9, the drive 6 remains connected to the motor 2 and includes electronic switches capable of withstanding the voltage induced by the machine 2 when operating as a generator.

The term "power grid" should be understood generally and encompass public or private, regional or local networks.

The electrical network is for example single-phase in about 100 V / 60 Hz or 220 V about / 50 Hz, or three-phase in about 400 V / 50 Hz or about 460 V / 60 Hz.

In the examples which have just been described, the electromechanical system comprises a gearbox or multiplier, but in non-illustrated variants, for other applications for example, the electromechanical system is devoid of it.

The expression "having one" shall be understood as being synonymous with "having at least one", unless the opposite is specified.

Claims

1. Electromechanical system (1) to be connected to an electrical network (7; 27), comprising: an electric machine (2; 22) capable of operating as an autonomous generator, comprising a rotary shaft, and a switching system (9) enabling ) in a first configuration, that the electric machine operates as a motor in the case where the coupled device (4) is normally driven or as a generator in the case where the coupled device (24) is normally driving, and ii) in a second configuration , that the electric machine operates as an autonomous generator, the electrical energy generated by the electric machine (2; 22) being dissipated in the machine and in a dissipative load (13).

2. System according to the preceding claim, the switching system (9) being arranged to automatically go from the first configuration to the second configuration in case of failure of an electrical network (7; 27) supplying the electrical machine or powered by it and / or stopping the machine.

3. System according to claim 1 or 2, comprising a reducer (3) or multiplier (3) between the shaft and a device (4) to be coupled to the electromechanical system.

4. System according to one of claims 1 to 3, the electric machine being a motor, the switching system for supplying the motor in the first configuration to drive the coupled device.

5. System according to claim 3, comprising a gear reducer.

The system of claim 5, wherein the reduction ratio is greater than 6.

7. System according to the preceding claim, the reduction ratio ranging from 7 to 15.

8. System according to any one of the preceding claims, comprising the dissipative charge (13).

9. System according to the preceding claim, wherein the dissipative charge comprises at least one metal or electrolyte resistance.

10. System according to any one of the preceding claims, the dissipative charge comprising at least one resistance immersed in a bath of a liquid.

11. System according to any one of the preceding claims, the machine having an internal impedance and the dissipative load (13) having an impedance less than this internal impedance.

12. System according to any one of claims 1 to 7, the switching system being arranged to short-circuit the electric machine in the second configuration, the bulk of the energy delivered by the machine being dissipated therein.

13. System according to any one of the preceding claims, the rotor of the electric machine (2) being permanent magnets.

14. System according to any one of claims 1 to 10, the machine being self-excited in the second configuration.

15. System according to claim 2, the switching system comprising at least one relay comprising a coil (10) powered by the electrical network.

An electrical system according to any one of the preceding claims, wherein the switching system (9) is arranged to remain in the second configuration as long as a predefined command is not received.

17. Electrical system according to claim 4, comprising a frequency converter (6) to which the motor is connected.

18. Electrical system according to the preceding claim, wherein the defined command is sent by the frequency converter.

Electrical system according to one of the preceding claims, comprising a device (10) for controlling the machine's speed (2; 22) designed to connect and disconnect the dissipative load (13) of the machine (2). 22) and / or act on the current flowing towards the dissipative load such that the speed of deviation remains between two predefined thresholds.

20. System according to claim 13, the rotor of the machine being at flux concentration.

21. Surface drive system of a progressive cavity pump for oil well, comprising: a motor (2) having an output shaft, a gear reducer between the output shaft and a drive rod of the pump,

a dissipative charge (13),

- a switching system (9) arranged to allow, in a first configuration, the motor to be powered by a power supply network (7) and to drive the pump drive rod in a first direction, and in a second configuration where the output shaft is rotated in a second direction opposite to the first, to transfer electrical energy generated by the engine thus driven to the dissipative load, the switching system (9) being arranged to automatically switch to the second configuration in case of power failure (7).

22. Surface drive system according to the preceding claim, wherein the electric motor is connected to a frequency converter (6).

23. Surface drive system according to one of the two preceding claims, wherein the reduction ratio is greater than 6, in particular from 7 to 15.

24. Surface drive system according to one of claims 21 to 23, the motor (2) being permanent magnets.

25. Surface drive system of a progressive cavity pump for oil well, comprising: a motor comprising a stator having windings and a rotor with permanent magnets, in particular a flux-concentration rotor, an arranged switching system. to allow, in a first configuration, the motor to be powered, and in a second configuration, to short-circuit the stator windings in case of accidental interruption of the motor supply.