Direct-current power supply system for fracturing and power supply method thereof

Abstract

The invention discloses a direct-current power supply system for fracturing and a power supply method thereof, and the system comprises a plurality of alternating-current generators, a plurality of controllable rectifiers, an energy storage battery pack, a direct-current bus, a plurality of inverters and a plurality of fracturing pump motors, and the alternating-current generators and the energy storage battery pack form a direct-current microgrid to form the direct-current power supply system. Fracturing equipment operation does not need to adopt an alternating current power grid for power supply, does not adopt alternating current power transmission, does not need to be equipped with a 35kV switching station, a 35kV / 10kV transformer, a 10kV switching station and a rectifier transformer, reduces intermediate links of power transformation, is simpler in circuit design and less in module number, reduces acquisition cost and occupied area, adopts low-voltage electricity to replace high-voltage electricity, and is more energy-saving and environment-friendly. High-voltage electricians do not need to be arranged on the fracturing operation site, the electrical safety risk is reduced, and the method is particularly suitable for low-power-grid-capacity and power-grid-free oil-gas field

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas production enhancement operations in oil and gas fields, and more specifically, to a direct current power supply system for fracturing and a power supply method thereof. Background Art

[0002] In recent years, my country's oil fracturing equipment has been fully electrified, using electric motors as power to drive fracturing pumps, which has brought many benefits, such as high work efficiency, energy saving, and environmental protection. However, the operation of electric motors requires electricity as energy support. At present, due to the developed power grid in Sichuan and Chongqing, the power grid basically covers the oil and gas fields, which provides good conditions for the industrial application of electric fracturing equipment. In my country, only the power grid in the Sichuan and Chongqing oil and gas field areas is relatively developed, but the power grid in other oil and gas field areas is not developed. There are situations where the power grid capacity is low or even no power grid, so electric fracturing equipment cannot meet the needs of use in these areas. In addition, in the current electric fracturing power supply system, combined with the attached Figure 1 As shown, 35kV high voltage electricity is usually transformed into 10kV AC electricity through a transformer, and then the 10kV is transformed into medium voltage 6kV or 3kV AC electricity to drive the fracturing pump motor. Such a fracturing power supply system is very inconvenient to purchase and transport due to the large size and high cost of the transformer. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] Another object of the present invention is to provide a DC power supply system and a power supply method for fracturing, so as to solve the technical problem that the prior art oil fracturing equipment cannot adapt to areas with insufficient power supply capacity of the power grid.

[0005] In order to achieve these purposes and other advantages according to the present invention, on the one hand, the present invention provides a DC power supply system for fracturing, including a plurality of AC generators, a plurality of controllable rectifiers, an energy storage battery pack, a DC bus, a plurality of inverters and a plurality of fracturing pump motors, wherein the input end of the controllable rectifier is electrically connected to an AC generator, and the output end is electrically connected to the DC bus, so as to convert the AC power generated by the AC generator into DC power and transmit it to the DC bus, the energy storage battery pack is electrically connected to the DC bus, so as to output DC power to the DC bus, the DC bus is used to supply DC power to the inverter, and the inverter is used to convert DC power into adjustable AC power, and the output is used to drive the fracturing pump motor to operate.

[0006] Preferably, one controllable rectifier is provided for each AC generator, and one inverter is provided for each fracturing pump motor.

[0007] Preferably, the AC generator outputs 600V AC power.

[0008] Preferably, the thermal energy generated by the combustion source of the alternator is converted into mechanical energy and then into electrical energy to generate three-phase alternating current.

[0009] On the other hand, the present invention also provides a DC power supply method for fracturing. The alternator generates 600V alternating current, which is converted into direct current through the controlled rectifier and independently supplies DC electrical energy to the DC bus. At this time, the energy storage battery pack does not supply DC electrical energy.

[0010] Preferably, the energy storage battery pack and the alternator jointly supply DC electrical energy to the DC bus.

[0011] Preferably, the energy storage battery pack independently supplies DC electrical energy to the DC bus. At this time, the alternator does not work.

[0012] Preferably, the alternator is converted into direct current through the controlled rectifier and charges the energy storage battery pack from the DC bus.

[0013] The present invention has at least the following beneficial effects: (1) The DC power supply system for fracturing of the present invention is particularly suitable for oil and gas fields with low grid capacity and no grid. An independent DC power system composed of an alternator and an energy storage battery provides power for electric fracturing equipment.

[0014] (2) The DC power supply system for fracturing of the present invention uses DC power supply to replace AC power supply. Transformers, 35kV switchyards, and 10kV switchyards do not need to be equipped at the well site, making the system structure simpler, the number of modules less, and reducing the purchase cost, transportation cost, and floor area.

[0015] (3) The DC power supply system for fracturing of the present invention uses low-voltage electricity instead of high-voltage electricity. High-voltage electricians do not need to be equipped at the fracturing operation site, reducing the risk of electrical safety.

[0016] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the AC power supply system for fracturing implemented in the prior art; Figure 2 Schematic diagram of the structure of the DC power supply system for fracturing of the present invention.

[0018] Figure marks in the specification: 1. 35kV switchgear, 2. 35kV / 10kV transformer, 3. 10kV switchgear, 4. Rectifier transformer, 5. Rectifier, 6. Inverter, 7. Fracturing pump motor, 1-1. The first AC generator, 1-2. The second AC generator, 1-N. The Nth AC generator, 2-1. The first energy storage battery, 2-N. The Nth energy storage battery, 3-1. The first controlled rectifier, 3-2. The second controlled rectifier, 3-N. The Nth controlled rectifier, 4-1. DC bus, 5-1. The first inverter, 5-2. The second inverter, 5-N. The Nth inverter, 6-1. The first fracturing pump, 6-2. The second fracturing pump, 6-N. The Nth fracturing pump. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0020] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] like Figure 2 As shown, the present invention provides a DC power supply system for fracturing, comprising a plurality of AC generators (1-1~1-N), a plurality of controllable rectifiers (3-1~3-N), an energy storage battery pack (2-1~2-N), a DC bus 4-1, a plurality of inverters (5-1~5-N) and a plurality of fracturing pump motors (6-1~6-N), wherein the input end of the controllable rectifier is electrically connected to an AC generator, and the output end is electrically connected to the DC bus, so as to convert the AC power generated by the AC generator into DC power and transmit it to the DC bus; the energy storage battery pack is electrically connected to the DC bus, so as to output DC power to the DC bus; the DC bus is used to supply DC power to the inverter; the inverter is used to convert DC power into adjustable AC power, and the output is used to drive the fracturing pump motor to operate.

[0022] The alternator converts the thermal energy of combustion sources such as diesel and gas into mechanical energy and then into electrical energy, generating three-phase alternating current; the controllable rectifier converts the three-phase alternating current into direct current with adjustable voltage and current through a controllable rectifier bridge; the energy storage battery pack is composed of multiple DC battery packs to form the DC voltage, current, and power required for fracturing to provide DC power for the fracturing equipment; the DC bus is used to converge the DC power converted by the alternator and the DC power of the energy storage battery pack to supply the required DC power for the fracturing equipment; the inverter is used to convert DC power into adjustable alternating current to control the variable-frequency motor on the fracturing pump, realizing speed control and protection of the variable-frequency motor; the fracturing pump motor is used to provide driving force for the plunger pump on the fracturing equipment, so that the fracturing pump outputs the required displacement.

[0023] The DC power supply system for fracturing realizes the operation of the fracturing pump motor through the following process: (1) The alternator generates 600V alternating current, which is converted into direct current through the controllable rectifier and independently supplies DC power to the DC bus, so that the inverter drives the fracturing pump motor to operate after being powered on.

[0024] (2) The energy storage battery and the alternator can jointly supply DC power to the DC bus, so that the inverter drives the fracturing pump motor to operate after being powered on.

[0025] (3) When the fracturing load is small, the excess power of the generator can be converted into direct current through the controllable rectifier and charged to the energy storage battery from the DC bus.

[0026] The DC power supply system for fracturing of the present invention includes several alternators, several controllable rectifiers, an energy storage battery pack, a DC bus, multiple inverters, and multiple fracturing pump motors. The alternator and the energy storage battery pack form a DC microgrid to form a DC power supply system, so that the fracturing equipment does not need to be powered by an AC power grid, does not use AC power transmission, does not need to be equipped with a 35kV switchgear, a 35kV / 10kV transformer, a 10kV switchgear, and a rectifier transformer, reducing the intermediate link of power transformation, simplifying the circuit design, reducing the number of modules, reducing the purchase cost and floor area, using low-voltage electricity instead of high-voltage electricity, eliminating the need for high-voltage electricians at the fracturing operation site, reducing the risk of electrical safety, and is especially suitable for oil and gas fields with low grid capacity and no power grid.

[0027] In another technical solution, as Figure 2 shown, one of the alternators is correspondingly provided with one of the controllable rectifiers, and one of the fracturing pump motors is correspondingly provided with one of the inverters. According to the load condition of the fracturing equipment, 1 or N of the alternators (1-1~1-N) can be put into operation to provide the required electric power for the fracturing load, and convert the alternating current into direct current through their respective controllable rectifiers (3-1~3-N) to supply DC power to the DC bus 4-1.

[0028] In another technical solution, as Figure 2 shown, the alternator (1-1~1-N) outputs 600V alternating current, meeting the working voltage requirements for specific fracturing equipment.

[0029] In another technical solution, as Figure 2 shown, the alternator (1-1~1-N) converts the thermal energy generated by a combustion source such as diesel or gas into mechanical energy, and then into electrical energy, generating three-phase alternating current.

[0030] The present invention also provides a DC power supply method for fracturing, including one of the following methods: A. The alternator (1-1~1-N) generates 600V alternating current, which is converted into direct current by the controllable rectifier (3-1~3-N) and independently supplies DC electrical energy to the DC bus 4-1. At this time, the energy storage battery pack (2-1~2-N) does not supply DC electrical energy.

[0031] B. The energy storage battery pack (2-1~2-N) and the alternator (1-1~1-N) jointly supply DC electrical energy to the DC bus 4-1.

[0032] C. The energy storage battery pack (2-1~2-N) independently supplies DC electrical energy to the DC bus line 4-1. At this time, the alternator does not work.

[0033] The alternator (1-1~1-N) is converted into direct current through the controllable rectifier (3-1~3-N) and charges the energy storage battery pack (2-1~2-N) from the DC bus line 4-1.

[0034] In the present invention, by setting up a DC power supply system, a controlled rectifier converts the alternating current generated by an alternator into direct current and transmits it to the DC bus. At the same time, the DC bus is connected to an energy storage battery pack. According to the fracturing load requirements of the fracturing pump motor of the actual terminal, the DC power supply mode can be flexibly selected, and the DC electrical energy can be supplied solely by the alternator or the energy storage battery pack, or jointly supplied by the alternator and the energy storage battery pack. When the fracturing load exceeds the total output power of the alternator, the energy storage battery pack can automatically and seamlessly respond to supplement electrical energy to the DC bus to ensure a stable output of the DC bus power supply. When the fracturing load is small, the excess power of the alternator can be converted into direct current through the controlled rectifier and used to charge the energy storage battery from the DC bus, providing power for the electric fracturing equipment. It is particularly suitable for oil and gas field fracturing operations in areas with low grid capacity and no power grid. By using DC power supply instead of AC power supply, there is no need to equip the well site with transformers, 35 kV switchyards, and 10 kV switchyards, making the system structure simpler and the number of modules fewer, reducing the floor area, purchase cost, and transportation cost.

[0035] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. A DC power supply system for fracturing, characterized in that, It includes several alternators, several controlled rectifiers, an energy storage battery pack, a DC bus, multiple inverters, and multiple fracturing pump motors. The input end of the controlled rectifier is electrically connected to an alternator, and the output end is electrically connected to the DC bus, which is used to convert the alternating current generated by the alternator into direct current and transmit it to the DC bus. The energy storage battery pack is electrically connected to the DC bus and is used to output DC power to the DC bus. The DC bus is used to supply DC power to the inverters, and the inverters are used to convert DC power into adjustable alternating current for output to drive the fracturing pump motors to operate.

2. The DC power supply system for fracturing according to claim 1, wherein One of the said controlled rectifiers is correspondingly provided for one of the said alternators, and one of the said inverters is correspondingly provided for one of the said fracturing pump motors.

3. The DC power supply system for fracturing according to claim 1, characterized in that, The said alternator outputs 600V alternating current.

4. The DC power supply system for fracturing according to claim 1, characterized in that, The said alternator converts the thermal energy generated by a combustion source into mechanical energy and then into electrical energy to generate three-phase alternating current.

5. The DC power supply method for fracturing according to claim 2, wherein The said alternator generates 600V alternating current, which is converted into direct current by the said controlled rectifier to independently supply DC electrical energy to the said DC bus. At this time, the energy storage battery pack does not supply DC electrical energy.

6. The DC power supply method for fracturing according to claim 1, wherein The energy storage battery pack and the alternator jointly supply DC electrical energy to the DC bus.

7. The DC power supply method for fracturing according to claim 1, wherein The energy storage battery pack independently supplies DC electrical energy to the DC bus. At this time, the alternator does not work.

8. The DC power supply method for fracturing according to claim 1, wherein The said alternator is converted into direct current through the said controlled rectifier and charges the energy storage battery pack from the DC bus.

Images