Energy distribution system

Abstract

An electrical energy distribution system (1) for a ship or a platform, comprising a plurality of DC buses (DC BB1, DC BB2, DC BB3, DC BB4), each coupled to a corresponding energy storage bus (ES BB1, ES BB2, ES BB3, ES BB4); each energy storage bus is coupled to an adjacent energy storage bus of the system by a first DC / DC converter (10, 11, 12, 13). The plurality of energy storage buses are connected together to form a ring. Each energy storage bus is also coupled to an energy storage device (14, 15, 16, 17) by a second DC / DC converter (18, 19, 20, 21).

Description

Technical Field

[0001] This disclosure relates to an energy distribution system, particularly an energy distribution system for distributing electrical energy on a ship or drilling rig, including a ship or platform, and a method of operating the energy distribution system. Background Technology

[0002] Operating a vessel, particularly a ship or platform such as an oil exploration platform, may require distributing electrical energy to multiple energy-consuming devices (e.g., propellers and pumps) that will operate on board. Additionally, the vessel or platform may perform other tasks, such as drilling, generating excess energy that needs to be dissipated. This electrical energy can be generated by prime movers, such as diesel engines and generators. Excess energy can be dissipated in braking resistors. The vessel or platform may include essential components that require electrical power even in the event of a failure in parts of the energy distribution system. An improved energy distribution system is desired. Summary of the Invention

[0003] According to a first aspect of the invention, an electrical power distribution system for a ship or platform includes a plurality of DC buses, each DC bus being coupled to a corresponding energy storage bus; each energy storage bus being coupled to an adjacent energy storage bus of the system via a first DC / DC converter; wherein the plurality of energy storage buses are connected together to form a loop; and wherein each energy storage bus is also coupled to an energy storage device via a second DC / DC converter.

[0004] The first DC / DC converter may include an arrangement of two pairs of parallel transistor diodes connected by an inductor.

[0005] The system may also include physically separated regions, each region being coupled to an adjacent region via a first DC / DC converter, the first DC / DC converter including either a parallel transistor diode arrangement or a pair of parallel transistor diode arrangements, and an inductor; and each region being coupled to another adjacent region via a third DC / DC converter, the third DC / DC converter including a pair of parallel transistor diode arrangements and an inductor.

[0006] The system may include at least three DC buses and at least three energy storage buses.

[0007] The system may also include at least a main energy source; wherein the main energy source includes an AC generator connected to an AC bus; wherein the AC bus is coupled to the DC bus or each DC bus via a transformer and an AC-to-DC converter.

[0008] The system may also include an intermediate AC bus with a voltage lower than that of the AC bus.

[0009] Energy storage devices may include one of the following: batteries, battery packs, capacitors, supercapacitors, or flywheels.

[0010] Multiple DC buses may include normally open switches between adjacent DC buses.

[0011] According to a second aspect of the invention, a method of operating an electrical power distribution system according to the first aspect includes detecting the voltage difference between an energy storage device and a DC bus, and allowing current to flow from a high voltage to a low voltage.

[0012] The energy storage device, or each energy storage device, can charge when there is excess energy on any DC bus, and discharge to a consuming device connected to any DC bus when the voltage of the DC bus is lower than the voltage of the energy bus of the energy storage device. Attached Figure Description

[0013] An example of an energy distribution system according to the present invention will now be described with reference to the accompanying drawings, wherein:

[0014] Figure 1 An example of an energy distribution system according to an embodiment of the present invention is shown;

[0015] Figure 2 Show in more detail Figure 1 A first example of a part of an energy distribution system;

[0016] Figure 3 Show in more detail Figure 1 A second example of a part of an energy distribution system; and

[0017] Figure 4 Show in more detail Figure 1 A third example of a part of an energy distribution system. Detailed Implementation

[0018] This disclosure addresses the need for a system for distributing electrical energy on a ship or platform, capable of maintaining the supply to essential consumable devices and reducing energy waste during drilling operations. In offshore drilling systems, significant amounts of braking energy are regenerated during drilling operations, otherwise the drill string would accelerate into the well, potentially causing damage to the rig or other equipment. Because braking resistors heat up and generate steam when dissipating braking energy, posing a hazard to deck operators and occupying considerable space on the rig or ship deck, operators desire to reduce or eliminate the use of braking resistors during drilling operations. Another problem is that seawater is a corrosive environment that corrodes and damages resistors over time.

[0019] Figure 1An example of an energy distribution system 1 for generating and distributing electrical energy on a ship or platform enhanced by the system of the present invention is shown. The system is shown as having a main AC switchboard including a series of AC buses AC BB1, AC BB2, AC BB3, and AC BB4, which can be looped together by pairs of normally closed switches 2. Prime movers such as diesel engines D1, D2, D3, and D4 feed AC generators G1, G2, G3, and G4 to generate AC power for the AC buses. For example, each diesel engine can supply up to 10 MW of power, and the power supplied to the AC buses can be up to 15 kV, 60 Hz AC. This loop arrangement allows one or more engines to shut down during low-load periods, and energy from the remaining minimal number of diesel engines is generated by operating these engines at near full power. Switches connecting the AC buses to each other, connecting generators or consumption devices, or transformers provide current isolation.

[0020] The AC bus can supply AC-consuming devices (not shown) and can supply power to DC buses DC BB1, DC BB2, DC BB3, and DC BB4 via unidirectional transformers T1, T2, T3, and T4 through AC-to-DC converter 3. AC-to-DC converter 3 is typically a diode rectifier arrangement that allows current to flow in only one direction. The rectifier can include a simple diode arrangement or other rectifier arrangements, wherein the diodes from the rectifier prevent energy from flowing from the DC bus back to the AC bus. An intermediate AC distribution panel (not shown) at a low voltage can be provided between the main AC distribution panel or AC bus and the DC distribution panel or bus, thus providing a first stage to reduce the AC voltage to, for example, 11kV. If needed, pairs of DC buses DC BB1, DC BB2 and DC BB3, DC BB4 can be connected together by closing switches 4 and 5 respectively.

[0021] This invention, through Figure 1 The energy distribution system 1, combined with the energy storage ring bus 6, provides an improvement over existing energy distribution arrangements. Traditionally, accumulators have been directly connected to the AC bus to smooth the supply to consuming devices also connected to these buses, and during drilling operations, braking resistors have been connected to the DC bus to dissipate the large amounts of excess energy regenerated during drilling operations as the drill string descends into the borehole. This is convenient because if the available amount is insufficient to handle the required or generated excess energy, it allows for the addition of accumulators in parallel with the AC bus, or the addition of more braking resistors in parallel with the DC bus.

[0022] The energy storage ring bus 6 can take several different forms. The first example is... Figure 2As shown in the example, four energy storage buses ES BB1, ES BB2, ES BB3, and ES BB4 are connected together in a ring via DC choppers (i.e., DC-to-DC converters 10, 11, 12, and 13, typically transistor-regulated converters). Energy buses ES BB1, ES BB2, ES BB3, and ES BB4 can be connected to their corresponding DC bus buses DC BB1, DC BB2, DC BB3, and DC BB4 via fuse 22. Each energy storage bus is also connected to energy storage units 14, 15, 16, and 17 via corresponding DC / DC converters or choppers 18, 19, 20, and 21. In the example shown, energy storage units 14, 15, 16, and 17 comprise batteries or battery packs, which are selected to have a predetermined capacity in kWh, depending on their application. Typical capacities for drilling operations will range from 400 kWh to 2000 kWh per energy storage unit. However, other forms of energy storage, such as capacitor banks, supercapacitors, or flywheels, can also be used. Control characteristics 22 of the DC bus voltage relative to the battery DC current for each DC bus and its associated battery are shown for battery choppers 18, 19, 20, and 21. This characteristic exhibits a positive DC current flowing from the battery to the DC bus. DC / DC converters can be used to control the charging supply to batteries 15, 16, 17, and 18 and to match the battery voltage to the operating voltage of the DC consuming devices on the DC bus. DC / DC choppers 10, 11, 12, and 13 in the loop have unique characteristics derived from the bus voltage difference between two buses, with the chopper positioned between these two buses, e.g., U2-U4 of chopper 11 plotted relative to the battery DC current of battery 15. In this example, this characteristic exhibits a positive DC current flowing from DC bus DC BB1 to DC bus DC BB4. For battery 16, only the level of the bus voltage connected to the battery will determine the battery current according to curve 23.

[0023] Current flow is controlled by the voltage difference at different points in the circuit. If the voltage is within the predetermined safe operating range of the components, current flow from high voltage to low voltage occurs automatically. For example, an increase in voltage in DC BB2 or ES BB2 (in reality, there is no voltage drop between these distribution panels) may cause current flow toward an adjacent bus (e.g., BB1 or BB3) that is at a lower voltage. During normal operation, control is performed solely by the voltage difference in the system. Excess voltage on BB2 by default will attempt to store the energy first in its own energy storage accumulator 15. Only when the capacity of this storage accumulator is nearly full will the excess voltage be directed to another energy storage bus, such as ES BB1 or ES BB3, via choppers 10 and 11, respectively.

[0024] Regenerated power from drilling operations returns to the DC bus and from there enters the corresponding island, where a storage loop allows regenerated energy to be supplied from the island to adjacent buses or adjacent accumulators. For example, if local accumulator 15 is near full capacity, e.g., charged to 85%, and a known drilling operation phase requires regeneration, one option is to reduce the battery charge level to closer to half by supplying power to the consuming device on the DC bus using stored energy, rather than drawing more energy from the AC bus for that consuming device. Then, as a last resort, the system can ensure each battery is fully charged before energy dissipation, for example by directing excess energy to a braking resistor connected to the DC bus. However, far fewer braking resistors are required compared to conventional drilling energy distribution systems, thus reducing operator concerns about the space occupied by braking resistors and decreasing the likelihood of injury to operators working on deck near the braking resistors.

[0025] If the voltage is outside the safe operating range of the component, other mechanisms are triggered to prevent overcharging. This can be achieved using overall system control, which may be a centralized or distributed control system, acquiring data from sensors (not shown) to enable appropriate action. Another advantage of having four islands in the power distribution network for drilling operations in this example is that there is no need for direct bus connections via switches 4 and 5 in the system. Choppers provide static protection in the event of a DC bus system failure and provide current or power regulation between the islands, allowing for different voltage levels in different DC systems. Therefore, if a single fault occurs, only one island fails, such as DC BB1, and choppers 10 and 13 disconnect that island from the others by current sensing and current level. The remaining islands can continue to store and extract energy, sharing excess energy via choppers 11 and 12 on the energy storage ring. The regulation principle of choppers 18, 19, 20, and 21 connected between the battery and the DC bus is conventional dropout regulation. The regulation of choppers 10, 11, 12, and 13 interconnecting the energy buses uses voltage differences to regulate current flow.

[0026] The advantage of using energy storage rings on a DC bus is that when DC drilling systems are interconnected via energy storage rings, braking energy flows freely throughout the entire DC system and can be reused by the consuming devices instead of being burned out in the braking resistors. In cases of excess energy from braking, this energy can be stored in the energy storage system. Another benefit is the increase in the total current that can be handled in the system. For typical 2000A rated components, such as DC choppers in offshore drilling applications, energy storage rings directly increase the number of choppers in the ring compared to conventional energy distribution systems, thus eliminating the need for an additional 6000A. Furthermore, this form of energy storage can be introduced into equipment with only minor modifications to existing DC systems, namely connecting each DC bus to its corresponding energy storage bus. Energy storage rings provide interconnection between buses in energy distribution systems, particularly for drilling operations or vessels with multiple thrusters that can then be interconnected for redundancy.

[0027] A second example of an energy storage ring used in an energy distribution system according to the invention. Figure 3 As shown in the image. Instead of Figure 1 The four DC buses are connected together in pairs. Figure 3 The example is adapted to use three DC buses with optional switches 30, 31 that allow the buses to be connected together. These switches are closed during normal operation. The energy storage ring 32 includes three batteries 33, 34, 35, each of which has a corresponding DC / DC converter 36, 37, 38 located between the battery and the bus, and choppers 39, 40, 41 located between paired energy buses ES BB1, ES BB2, ES BB3. Characteristics 23, 24 present a positive DC current from the battery to the energy bus, and for chopper 41, a current from energy bus ES BB3 to ES BB1. A similar presentation applies to chopper 40 (from ES BB2 to ES BB3) and chopper 39 (from ES BB1 to ES BB2). Each energy bus ES BB1, ES BB2, ES BB3 is connected to its corresponding DC bus DC BB1, DC BB2, DC BB3 via fuse 22.

[0028] The benefit of this invention lies in enhancing the robustness of drilling systems, where overall energy consumption is reduced through energy reuse and sharing between buses. This reduces the need for AC generators and prime movers. DC systems are most commonly used in offshore electrical applications, particularly offshore drilling. Another offshore application is on vessels where high reliability is required. One example is the electric propulsion drive and thruster, i.e., DP3, which is critical to operation, for example, when drive force decreases and the vessel must be able to maintain station and power. For a DC system with propulsion drives on a vessel, all islands can be disconnected for operation, one thruster per island. In another example, such as... Figure 4 As shown, there are physical separations of units at different locations on the ship, separated by bulkheads or fire-resistant walls to prevent flooding or fire.

[0029] Reference numerals for equivalent parts Figure 1 same.

[0030] In this example, two DC / DC converters are placed in each distinct area so that a fault does not propagate from one DC / DC converter to the other. Therefore, instead of a first DC / DC converter between each bus on the ring and a second DC / DC converter from each bus to the accumulator, each distinct area has a first DC / DC converter and a third DC / DC converter. This allows the diesel engines to operate closer to full load when not all engines are running, instead of each individual area having to have a running power source operating at 15% to 20% load as is currently the case. If a running engine fails, the battery pack in the energy storage ring covers the power requirement during the conversion when another engine starts. The converters in this example include choppers, and Figure 4 The type of chopper used at each end of the cable between the ES buses in the system only requires a two-quadrant chopper 80, although a four-quadrant chopper 81 can also be used. However, due to the higher cost, additional losses, and larger space requirements, a two-quadrant chopper is preferable in this case.

[0031] on the contrary, Figure 2 , Figure 3 and Figure 4 The battery chopper in the circuit needs to be a four-quadrant chopper 81. The four DC buses DC BB1, DC BB2, DC BB3, and DC BB4 are equivalent to... Figure 1 and Figure 2The buses in the circuit are connected to the power ring bus DP zone via fuse 22. BB1 is connected to zone 1 50, BB2 to zone 2 51, BB3 to zone 3 52, and BB4 to zone 4 53. In zone 1 50, the power bus ES BB1 has two partial choppers 60 and 61 that connect it to adjacent zones 2 51 and 3 52, and a full chopper 54 between the battery 70 and the power bus ES BB1. Connecting lines or connecting buses are provided between the partial choppers in different adjacent zones, i.e., between partial choppers 61 and 62 in zones 50 and 51, or between partial choppers 63 and 64 in zones 51 and 53, and similarly for the other choppers 65, 66, 67, and 60 in zones 53, 52, and 50.

[0032] In zone 2, 51, the energy bus ES BB2 has two partial choppers 62 and 63 connecting it to adjacent zones 1, 50 and 3, 52, and a full chopper 55 between battery 71 and the energy bus ES BB2. In zone 3, 52, the energy bus ES BB3 has two partial choppers 66 and 67 connecting it to adjacent zones 1, 50 and 4, 53, and a full chopper 56 between battery 72 and the energy bus ES BB3. In zone 4, 53, the energy bus ES BB4 has two partial choppers 64 and 65 connecting it to adjacent zones 2, 51 and 3, 52, and a full chopper 57 between battery 72 and the energy bus ES BB4.

[0033] The power distribution system described above can operate by detecting the voltage difference between the energy storage device and the DC bus, and allowing current to flow from high voltage to low voltage. The energy storage device, or each energy storage device, can charge when there is excess energy on any DC bus, and discharge to consuming devices connected to any DC bus when the voltage of the DC bus is lower than the voltage of the energy storage device's energy bus. Therefore, through sharing, the energy storage device and power supply can be utilized more efficiently.

[0034] Embodiments of the invention have been described with reference to various subjects. In particular, some embodiments have been described in conjunction with method-type claims, and others with apparatus-type claims. However, those skilled in the art will understand from the context that, unless otherwise stated, any combination of features relating to different subjects, particularly any combination of features between the features of method-type claims and the features of apparatus-type claims, is also considered to be disclosed in this document, except for any combination of features belonging to one type of subject matter.

[0035] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, elements described in conjunction with different embodiments may be combined. All features disclosed in this specification (including any appended claims, abstract, and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except for combinations in which at least some of such features and / or steps are mutually exclusive.

[0036] Unless otherwise expressly stated, each feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by an alternative feature having the same, equivalent, or similar purpose. Therefore, unless otherwise expressly stated, each disclosed feature is merely an example of a series of equivalent or similar features. It should also be noted that the reference numerals in the claims should not be construed as limiting the scope of the claims. The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification (including any appended claims, abstract, and drawings), or to any novel step or any novel combination of steps in any method or process so disclosed.

Claims

1. A power distribution system for a ship or platform, comprising multiple DC buses, each DC bus coupled to a corresponding energy storage bus; each energy storage bus being coupled to an adjacent energy storage bus of the system via a first DC / DC converter, wherein the regulation of the first DC / DC converter is based on the voltage difference between adjacent energy storage buses to achieve current flow control; wherein, The multiple energy storage buses are connected together to form a ring. The current flow in the ring is controlled by the voltage difference at different points in the circuit. When the voltage is within the predetermined safe operating range of the component, the current automatically flows from the high-voltage side to the low-voltage side. Each energy storage bus is also coupled to the energy storage unit through a second DC / DC converter.

2. The system according to claim 1, wherein, The first DC / DC converter includes two pairs of parallel transistor diodes connected by an inductor.

3. The system according to claim 1, wherein, The system further includes physical partitions, each partition being coupled to an adjacent partition via a first DC / DC converter, the first DC / DC converter including either a parallel transistor diode arrangement or a pair of parallel transistor diode arrangements, and an inductor; and each partition being coupled to another adjacent partition via a third DC / DC converter, the third DC / DC converter including a pair of parallel transistor diode arrangements and an inductor.

4. The system according to any one of the preceding claims, wherein, The system includes at least three DC buses and at least three energy storage buses.

5. The system according to any one of claims 1-3, wherein, The system also includes at least a main energy source; wherein the main energy source includes an AC generator connected to an AC bus; wherein the AC bus is coupled to the DC bus or each DC bus via a transformer and an AC-to-DC converter.

6. The system according to any one of claims 1-3, wherein, The system also includes an intermediate AC bus with a voltage lower than that of the AC bus.

7. The system according to any one of claims 1-3, wherein, The energy storage device includes one of a battery, a battery pack, a capacitor, a supercapacitor, or a flywheel.

8. The system according to any one of claims 1-3, wherein, The plurality of DC buses includes normally open switches between adjacent DC buses.

9. A method of operating an electrical power distribution system according to any one of the preceding claims, the method comprising detecting a voltage difference between an energy storage device and a DC bus, and allowing current to flow from a high voltage to a low voltage.

10. The method according to claim 9, wherein, The energy storage device or each energy storage device charges when there is excess energy on any of the DC buses, and discharges to consuming devices connected to any of the DC buses when the voltage of the DC bus is lower than the voltage of the energy bus of the energy storage device.

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