Pumping unit

Abstract

The embodiment of the utility model provides an oil pumping unit set, and relates to the field of oil and gas exploitation control, the oil pumping unit set comprises a plurality of oil pumping units, and each oil pumping unit comprises a frequency converter and a motor which are connected with each other; the pumping unit set further comprises a common direct current bus which comprises a positive electrode and a negative electrode. The frequency converters of the oil pumping units are connected in parallel to the common direct-current bus, the positive ends of the frequency converters are connected to the positive electrode of the common direct-current bus, and the negative ends of the frequency converters are connected to the negative electrode of the common direct-current bus. According to the pumping unit set provided by the embodiment of the invention, the direct current side bus-side buses of the frequency converters of the multiple pumping units are connected to the common direct current bus to form a large-scale direct current power supply system, and on the formed pumping unit set, regenerated energy generated by one or more motors in the pumping unit set can be absorbed by other motors in an electric mode, so that the power consumption of the pumping unit set is reduced. The problem that the voltage of the direct-current bus is too high due to regenerated energy generated by the motor can be reduced, and energy waste can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas production control, in particular to an oil pumping unit. BACKGROUND

[0002] As the most important energy-consuming equipment in oilfield production, the oil pumping unit is generally operated 24 hours a day, and its energy utilization rate is directly related to the cost of oil production. Therefore, it is of great significance to strengthen the research and analysis of the energy consumption of the oil pumping unit, find energy-saving methods, and improve production efficiency.

[0003] When the oil pumping unit is working with unbalanced counterweights, the mechanical energy of the load is converted into electrical energy during the deceleration or braking process of the motor. If this part of electrical energy is not processed, it will cause the DC bus voltage of the frequency converter to rise, affecting the normal operation of the frequency converter, and even causing the frequency converter to fail.

[0004] Therefore, the oil pumping unit cabinet is generally equipped with a braking unit and a braking resistor. When the DC voltage rises to a certain value, the power tube of the braking unit is turned on, the current flows through the braking resistor, the braking resistor releases heat, absorbs the regenerated energy, and reduces the DC bus voltage. When the DC bus voltage drops to a certain voltage, the power tube of the braking unit is turned off, and at this time, no braking current flows through the resistor, and the braking resistor naturally dissipates heat to reduce its temperature. Although this solves the problem of excessive DC bus voltage, it also causes energy waste. CONTENT OF THE INVENTION

[0005] The oil pumping unit provided by the embodiments of the present application can effectively solve the above technical problems.

[0006] The specific technical solutions of the embodiments are as follows:

[0007] The oil pumping unit provided by the embodiments of the present application can effectively solve the above technical problems.

[0008] In some embodiments, a first fuse is arranged between the positive terminal of the frequency converter and the positive pole of the common DC bus, and a second fuse is arranged between the negative terminal of the frequency converter and the negative pole of the common DC bus.

[0009] In some embodiments, a first control switch is further connected in series with the first fuse between the positive terminal of the frequency converter and the positive pole of the common DC bus, and a second control switch is further connected in series with the second fuse between the negative terminal of the frequency converter and the negative pole of the common DC bus.

[0010] In some embodiments, the frequency converter is also electrically connected with a braking unit and a braking resistor.

[0011] In some embodiments, the pumping unit set comprises 4-12 pumping units.

[0012] In some embodiments, the plurality of pumping units in the pumping unit set are connected to the same three-phase power supply.

[0013] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0014] In the pumping unit set provided by the embodiments of the present application, the DC side bus of the frequency converter of the plurality of pumping units is connected to the common DC bus, forming a large DC power supply system, and in the formed pumping unit set, the regenerative energy generated by one or more motors in the pumping unit set can be absorbed by other motors in the form of electric driving, which can not only reduce the problem of over-high DC bus voltage caused by the regenerative energy generated by the motor, but also avoid the waste of energy. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is an electrical schematic diagram of the pumping unit cabinet in the prior art;

[0017] Figure 2 is an electrical schematic diagram of the pumping unit set in some embodiments of the present application;

[0018] Figure 3 is a basic principle schematic diagram of the frequency converter in some embodiments of the present application;

[0019] Figure 4 is a schematic diagram of external wiring terminals of the frequency converter in some embodiments of the present application;

[0020] Figure 5 is a control loop schematic diagram of the DC bus parallel scheme provided by some embodiments of the present application;

[0021] Figure 6 is a main loop schematic diagram of the DC bus parallel scheme provided by some embodiments of the present application;

[0022] Figure 7 is an effect comparison diagram of the pumping unit set provided by some embodiments of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely in the description of the embodiments of the present application in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the scope of protection of the present application.

[0024] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0025] "A and / or B" includes the following three combinations: only A, only B, and a combination of A and B.

[0026] The use of "adapted to" or "configured to" in the present application means open and inclusive language that does not exclude devices adapted to or configured to perform additional tasks or steps. In addition, the use of "based on" means open and inclusive, because the process, step, calculation or other action "based on" one or more stated conditions or values can be based on additional conditions or values beyond those stated in practice.

[0027] In the present application, the word "exemplary" is used to mean "serving as an example, instance, or illustration." Any implementation described as "exemplary" in the present application is not necessarily to be construed as preferred or advantageous over other implementations. The following description is presented to enable any person skilled in the art to make and use the present application. In the following description, for the purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present application. It should be apparent to one skilled in the art, however, that the present application can be practiced without the use of these specific details. In other instances, well-known structures and processes are not elaborated upon in order to avoid unnecessary detail, which might obscure the description of the present application. Accordingly, the present application is not intended to be limited by the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0028] The embodiment provides an oil pumping unit, which comprises a common DC bus and a plurality of oil pumping units, each of the oil pumping units comprises a frequency converter and a motor connected with each other, the common DC bus comprises a positive electrode and a negative electrode, the frequency converters of the plurality of oil pumping units are connected in parallel with each other and connected to the common DC bus, a positive electrode end of the frequency converter is connected to the positive electrode of the common DC bus, and a negative electrode end of the frequency converter is connected to the negative electrode of the common DC bus.

[0029] In the above embodiment, the DC side bus of the frequency converters of the plurality of oil pumping units is connected to the common DC bus, thereby forming a large DC power supply system, and in the formed oil pumping unit, the regenerated energy generated by one or more motors in the oil pumping unit can be absorbed by other motors in the form of electric driving, thereby reducing the problem of overhigh DC bus voltage caused by the regenerated energy generated by the motor and avoiding energy waste.

[0030] In some embodiments, a first fuse FU1 is arranged between the positive electrode end of the frequency converter and the positive electrode of the common DC bus, and a second fuse FU2 is arranged between the negative electrode end of the frequency converter and the negative electrode of the common DC bus. Through the arrangement, the first fuse and the second fuse isolate the frequency converter and the common DC bus from each other, thereby improving the overall safety of the oil pumping unit.

[0031] In some embodiments, the first fuse is further connected in series with a first control switch KM1 between the positive electrode end of the frequency converter and the positive electrode of the common DC bus, and the second fuse is further connected in series with a second control switch KM2 between the negative electrode end of the frequency converter and the negative electrode of the common DC bus. Through the arrangement, the first control switch and the second control switch can be used to control the on-off of the circuit between the frequency converter and the common DC bus, thereby further improving the overall safety of the oil pumping unit.

[0032] In some embodiments, the frequency converter is further electrically connected with a braking unit and a braking resistor. The positive electrode end of the frequency converter is connected to the positive electrode end of the braking unit, the negative electrode end of the frequency converter is connected to the negative electrode end of the braking unit, to form a loop, and then the braking resistor is arranged on the formed loop. Through the arrangement, the braking unit and the braking resistor can still be used as redundant protection, and the regenerated energy generated by the motor can be absorbed when the redundant protection is performed, thereby further improving the overall safety of the oil pumping unit.

[0033] In some embodiments, the oil pumping unit comprises 4-12 oil pumping units. Through the arrangement, the formed oil pumping unit has better operation performance.

[0034] In some embodiments, the plurality of oil pumping units in the oil pumping unit are connected to the same three-phase power supply. Through the arrangement, the oil pumping unit can better transfer the regenerated energy generated by the motor to other frequency converters through the common DC bus, and reduce the influence on other frequency converters.

[0035] In a specific example, the application proposes an oil pumping unit, which can be modified in the original oil pumping cabinet, only a small amount of electrical elements need to be added. The construction is simple, the modification is convenient, and it is beneficial to promote and utilize on site.

[0036] Each oil pumping cabinet can retain its own braking unit and braking resistor, even if multiple motors are in the power generation state at the same time, there is no need to worry about the processing method of regenerative energy.

[0037] Before modification, each oil pumping cabinet serves as an independent control system, with a frequency converter, a braking unit, a braking resistor, and a 24V power module, and its system is as shown in Figure 1 .

[0038] The oil pumping unit in the application is as shown in Figure 2 , and four oil pumping units are taken as an example for illustration. In the application, the DC positive terminals of the four frequency converters are connected in parallel, and the DC negative terminals are also connected in parallel. This not only reduces the number of times the braking unit works, but also utilizes the regenerative energy generated during the braking process of the oil pumping unit, and at the same time, reduces the number of times of interference to the power grid, and improves the power quality of the power grid.

[0039] As can be seen from the schematic diagram of the basic principle of the general frequency converter in Figure 3 , the DC positive (+) and DC negative (—) of the frequency converter are connected in parallel respectively, which does not affect their respective functions, but makes the rectification capacity larger, the filter capacitor larger, and the anti-interference ability stronger after the frequency converter is connected in parallel at the DC side.

[0040] In the application, the common DC bus technology is to use a separate rectification / feedback device to provide a certain power DC power supply for the system in a multi-motor AC speed regulation system, and the speed regulation inverter is directly connected to the DC bus. When the system works in the motor state, the inverter obtains power from the bus; when the system works in the power generation state, the energy is directly fed back to the power grid through the bus and the feedback device, so as to achieve the purposes of energy saving, improving the reliability of equipment operation, reducing the amount of equipment maintenance and equipment area, etc.

[0041] When the general frequency converter is connected in parallel at the DC bus, the pre-charging circuit of the rectification needs to be considered. The advantage of the embodiment of the application is to utilize the pre-charging circuit of the frequency converter itself, without the need to additionally increase the pre-charging circuit, which is simple to modify and convenient to popularize and apply.

[0042] Each frequency converter has an internal pre-charge circuit, which will not cause damage to the frequency converter under normal start-up sequence. However, if a frequency converter does not start, a voltage is applied to the DC ± poles of the frequency converter through the parallel DC bus, and due to the capacitor in the rectifier circuit of the frequency converter, a large instantaneous current can be generated, which can burn the frequency converter. In the present application, after the frequency converter is started normally, the capacitor pre-charge is completed, and then the DC ± poles of the frequency converter are connected in parallel to the common DC bus. In this way, the damage of the instantaneous voltage to the components of the frequency converter is avoided.

[0043] Taking a three-crystal frequency converter as an example, the external wiring terminal diagram of the frequency converter is shown in Figure 4 T2A / T2C are a group of relay normally open contacts, and are not used. According to the user manual of the three-crystal frequency converter, the group of relay output contacts can be defined by F6.03 group parameters. The F6.03 group parameter value is set to: 1 (operation signal). In this way, only when the pumping unit is running normally, T2A / T2C is connected, and the DC contactor is powered on, so that the DC ± poles of the frequency converter are connected in parallel to the common DC bus. That is, before the DC ± poles of the frequency converter are connected in parallel to the common DC bus, the pre-charge of the rectifier of the frequency converter has been completed.

[0044] The pumping unit group provided in the present application has the advantage that when a frequency converter fails, the DC ± poles of the frequency converter can be automatically disconnected from the common DC bus, without affecting other frequency converters.

[0045] The following points need to be noted for the parallel connection technology of the DC bus of the general frequency converter:

[0046] 1. When several frequency converters are simultaneously braked, the problem of residual energy consumption.

[0047] Each pumping unit cabinet can be configured with a braking unit and a braking resistor, and in the energy-saving modification scheme, the original energy consumption braking system of the pumping unit cabinet is retained. Even if each frequency converter connected in parallel is simultaneously braked, the energy generated by braking can be consumed by the self-braking resistor.

[0048] 2. The several frequency converters that need to be connected in parallel are preferably installed together to avoid long-distance wiring.

[0049] 3. The number of frequency converters connected in parallel is best between 4 and 12.

[0050] The principle of 4-6 units in a group is adopted for the parallel connection of the DC bus of the frequency converter of the pumping unit cabinet, which can achieve the best effect.

[0051] 4. An additional isolation protection device must be provided for each frequency converter.

[0052] In the application, the DC + and - poles of each frequency converter are connected to the common DC bus through fast fusing to prevent all frequency converters from burning out in the case of short circuit of the DC bus.

[0053] 5. The parallel frequency converters must use the same three-phase power supply.

[0054] For a well site with two box converters, special attention must be paid to the problem that the three-phase power supply of the parallel frequency converters must be of the same source.

[0055] 6. After the frequency converter fails, it should be quickly disconnected from the common DC bus to avoid affecting other frequency converters.

[0056] In the application, the control loop is composed of a DC contactor, a 24V power supply module built-in the cabinet and a frequency relay output contact to achieve the above purpose.

[0057] 7. Data comparison before and after the DC bus of the frequency converter is connected in parallel.

[0058] The energy-saving reconstruction scheme is tested in four wells, and the data before and after the DC bus of the four frequency converters is connected in parallel are measured as shown in the table. Figure 7

[0059] Through comparison, it is found that after the DC bus is connected in parallel, the following phenomena are found:

[0060] (1) The maximum DC voltage of the frequency converter is significantly reduced.

[0061] (2) There is current between the parallel buses.

[0062] (3) The maximum input current of the oil pumping unit cabinet is significantly reduced.

[0063] (4) The working time of the braking unit is significantly shortened.

[0064] Through the phenomena, it can be analyzed that the four frequency converters have obvious energy-saving effect after being connected in parallel to the common DC bus.

[0065] The utility model discloses a kind of oil pumping unit, utilize direct current bus parallel technology and connect together multiple oil pumping unit frequency converter direct current bus, such not only can utilize regenerative energy in braking process of oil pumping unit, also can reduce system voltage fluctuation.The main electrical components of the system include frequency converter, braking unit, braking resistance, contactor, fuse.

[0066] For the reconstruction of conventional frequency conversion cabinet, only a small amount of electrical components such as contactor, fast fusing and cable need to be added to implement, which is convenient for popularization and application.Contactor controls single frequency converter to access or disconnect, fast fusing protects the capacitor unit of frequency converter on DC bus, and cable mainly connects the DC + and - poles of each frequency converter in parallel.

[0067] ​The pumping unit provided by the application has the following advantages:

[0068] 1. Each frequency conversion cabinet has a set of independent rectifier and inverter units, instead of a rectifier with multiple inverters.

[0069] 2. The structure is simple and easy to transform and implement. No additional rectifier bridge, pre-charging unit, capacitor group and inverter are needed.

[0070] 3. Each frequency converter can be independently disconnected from the DC bus for operation, or the DC ± poles of the frequency converter can be connected in parallel to the common DC bus for operation.

[0071] 4. The contactor action is controlled by the frequency converter relay output contact, realizing the linking and disconnection of the frequency converter DC bus and the common DC bus.

[0072] 5. Four to six frequency converters form a group, and the DC (P+) and DC (-) of each frequency converter are connected together through a 1*16 square cable.

[0073] 6. Each frequency converter has its own independent braking unit and braking resistor, which can consume the excess energy generated by several frequency converters under simultaneous braking conditions.

[0074] 7. Each frequency converter is equipped with two fast fuses to protect the capacitor unit of the frequency converter on the DC bus, which can also avoid the situation that a short circuit of the DC bus causes damage to all frequency converters.

[0075] In the application, specific examples are applied to illustrate the principles and implementation modes of the application. The above examples are only used to help understand the method and its core idea of the application. Meanwhile, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the application.

Claims

1. A pumping unit characterized by, The pumping unit set comprises a plurality of pumping units, each of which comprises a frequency converter and a motor connected with each other; the pumping unit set further comprises a common DC bus comprising a positive pole and a negative pole; the frequency converters of the plurality of pumping units are connected in parallel with each other to the common DC bus, the positive pole of the frequency converter is connected to the positive pole of the common DC bus, and the negative pole of the frequency converter is connected to the negative pole of the common DC bus.

2. The pumping unit set according to claim 1, characterized in that A first fuse is arranged between the positive pole of the frequency converter and the positive pole of the common DC bus, and a second fuse is arranged between the negative pole of the frequency converter and the negative pole of the common DC bus.

3. The pumping unit set according to claim 2, characterized in that The first fuse is further connected in series with a first control switch between the positive pole of the frequency converter and the positive pole of the common DC bus, and the second fuse is further connected in series with a second control switch between the negative pole of the frequency converter and the negative pole of the common DC bus.

4. The pumping unit set according to claim 1, wherein The frequency converter is further electrically connected with a braking unit and a braking resistor.

5. The pumping unit set according to claim 1, wherein The pumping unit set comprises 4-12 pumping units.

6. The pumping unit set of claim 1, wherein, The plurality of pumping units in the pumping unit set are connected to the same three-phase power supply.

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