Self-contained transportable electric heave compensation system

Abstract

A mobile active heave compensation system (10) provided with a first attachment device (12) allowing said mobile active heave compensation system (10) to be suspended from a load bearing device (14) and provided with a second attachment device (16) allowing said mobile active heave compensation system (10) to carry a payload (18), said mobile active heave compensation system (10) comprising: - a control unit (20), - a heave compensation part (22) comprising an electrically driven actuator (24), - a sensor arrangement (26) producing input signals for said control unit (20) to control the heave compensation part (22), - an electric power source (28) provided with supercapacitors (30), such that, in a first heave compensation phase, when the heave compensation part (22) generates energy, electric power is stored in said supercapacitors (30) and, in a second heave compensation phase, when the heave compensation part (22) requires energy, electric power stored in said supercapacitors (30) is supplied to said electrically driven actuator (24).

Description

TECHNICAL FIELD

[0001] The present invention relates an active heave compensation system.

[0002] The present invention relates more particularly to an in-line active heave compensation system.BACKGROUND

[0003] Heave compensation systems may comprise heave compensators that are connected between a load bearing device and the load. The compensation is in-line with the load and will be referred to as in-line active heave compensator (IAHC).

[0004] The purpose of heave compensators is to keep a load, held by equipment on a moving vessel, motionless with regard to the seabed, a fixed structure, or another vessel. Additionally, dynamic behavior and force control need to be managed during splash zone transition.

[0005] Transfer of load needs also to be managed. During load transfer there is a period of time where heave compensator needs to be force controlled, as position is defined by vessel movement and the load is still on the moving vessel, and there is a period of time, during hoisting and approaching of a vessel, where heave compensator needs to be position controlled, as the full load is in the hook.SUMMARY

[0006] The scope of protection is set out by the claims.

[0007] The invention propose a mobile active heave compensation system provided with a first attachment device allowing said mobile active heave compensation system to be suspended from a load bearing device and provided with a second attachment device allowing said mobile active heave compensation system to carry a payload, said mobile active heave compensation system comprising: a control unit, a heave compensation part comprising an electrically driven actuator, a sensor arrangement producing input signals for said control unit to control the heave compensation part, an electric power source provided with supercapacitors, such that, in a first heave compensation phase, when the heave compensation part generates energy, electric power is stored in said supercapacitors and, in a second heave compensation phase, when the heave compensation part requires energy, electric power stored in said supercapacitors is supplied to said electrically driven actuator.

[0008] According to various embodiments of the mobile active heave compensation system: the system comprises at least one of an auxiliary battery and an auxiliary power cable which are controlled by an energy management system; the electrically driven actuator uses spur gear mounted electric motors; the electrically driven actuator is supported by a non-adjustable passive system; the electric power source comprises a brake resistor device able to consumes excess of energy supply during the first heave compensation phase; each supercapacitor is provided with a bypass circuit to control pre-charge and discharge; the auxiliary battery is provided with a DC / DC converter to allow a bigger discharge of the auxiliary battery; an electric filter circuit is provided to protect the electrically driven actuator.

[0009] It is also proposed a control method for the mobile active heave compensation system mentioned above, comprising the steps of: storing electric power in said supercapacitors during a first heave compensation phase, when the heave compensation part generates energy, and supplying electric power to said electrically driven actuator during a second heave compensation phase, when the heave compensation part requires energy.

[0010] According to an embodiment, the mobile active heave compensation system is comprising a frame having top attachment device and bottom attachment device, and when in use, the bottom attachment device is suspended to at least one heave compensation part (a winch) attached to the frame. According to an embodiment, the mobile active heave compensation system is built with a multiple winch configuration as a modular unit: several electric winches are integrated into the "active hook" or "active heave compensator" (the mobile active heave compensation system) and synchronously controlled to dynamically distribute the load and actively compensate for wave motion.

[0011] According to an embodiment, the mobile active heave compensation system is autonomous. In other words, the mobile active heave compensation system is a all-in-one device to be suspended to a lifting device (eg a crane of a vessel) and capable to hang a load to provide active heave compensation. The mobile active heave compensation system (or device) is comprising at least (attached to or embarked onto the frame to be suspended) the control unit, the heave compensation part (eg at least one winch), the sensor arrangement, the electric power source with the supercapacitors to power the heave compensation part. Preferably, the system is free or devoid from any external power supply or the system is free of any electric connection with the craft or the crane. In other words, there is preferably no external power supply as a cable or power line between the mobile active heave compensation system and the vessel or crane or craft where the system is used.

[0012] According to a preferred embodiment, the mobile active heave compensation system (or device) is comprising at least one auxiliary battery. According to an embodiment, the at least one auxiliary battery is used to compensate for energetic or power losses, including notably electric losses, mechanic or fiction losses and the like, and is also attached to the frame and provided in the mobile active heave compensation system. However, in some embodiments, a power cable can be connected to the autonomous heave compensator for redundancy purposes.

[0013] According to an embodiment, the supercapacitors present or are capable to deliver a first peak power and the auxiliary battery presents or is capable to deliver a second peak power, and the first peak power is greater than the second peak power, preferably the first peak power is 50% greater than the second peak power, preferably the first peak power is 100% greater than the second peak power (the double), preferably the first peak power is three times, or four times greater than the second peak power. In such embodiment, the supercapacitors are the sole source of power for the heave compensation part (the winches) with strong and fast capacity to deliver power for fast and efficient active compensation, while the auxiliary battery is dedicated to charge the supercapacitors to compensate for energy losses for long autonomous use.

[0014] According to an embodiment, the supercapacitors present or are capable to store a first electric energy and the auxiliary battery presents or is capable to store a second electric energy, and the second electric energy is greater than the first electric energy, preferably the second electric energy is 50 times, 100 times, 200 times, 250 times greater than the first electric energy. According to an embodiment, the auxiliary battery is sized to be able to compensate energy losses during at least one hour, at least two hours, at least three hours of active compensation by the mobile active heave compensation system (during which the heave compensation part is operating 100% of the time).

[0015] According to an embodiment, the mobile active heave compensation system is comprising at least one loss estimating unit, arranged to monitor or calculate an energy loss based on monitoring the heave compensation part use (typically a winch). In particular, the loss estimating unit is arranged to estimate: a first loss during the first heave compensation phase (corresponding to joule losses in wires, capacitors losses during storage and winch or heave compensation part losses (ie friction) when recovering electricity), and / or a second loss during the second heave compensation phase (corresponding to joule losses in wires, capacitors losses during supply and winch losses (ie friction) when consuming electricity).

[0016] According to an embodiment, the control unit is arranged to control the auxiliary battery to provide power to the supercapacitors when the loss estimating unit has determined that an energy loss has exceeded a threshold. Preferably, the auxiliary battery remains disconnected from the electric circuit when the energy loss has not exceeded the threshold. In other words, the auxiliary battery is used only to compensate for the energy losses. The auxiliary battery is not used to power the heave compensation part or winches.

[0017] According to an embodiment, the heave compensation part is comprising several winches. This provides the capacity to compensate movement in multiple degrees of freedom (vertical, roll, and pitch). According to an embodiment, the heave compensation part is comprising as much winches as degrees of freedom to compensate. In a specific embodiment, the heave compensation part is comprising a first winch to compensate movement according to a first degree of freedom, a second winch to compensate movement according to a second degree of freedom, a third winch to compensate movement according to a third degree of freedom. In a more specific embodiment, the heave compensation part is comprising a first winch to compensate heave or vertical movement, a second winch to compensate pitch movement, a third winch to compensate roll movement. According to an embodiment, the mobile active heave compensation system is comprising a top frame and a lower frame, with one winch or preferably several winches in between.

[0018] According to an embodiment, the mobile active heave compensation system is free of passive compensation such as gas springs, and / or pressurized vessel connected to cylinders.

[0019] According to an embodiment, the mobile active heave compensation system is comprising an energy dissipating element, used to dissipate excess of recovered electricity, only when supercapacitors and battery are fully charged. One understands that such energy dissipating element is needed only at very beginning of use, if the system faces an important (unexpected) energy recovery during the first heave compensation phase.

[0020] According to an embodiment, the mobile active heave compensation system is capable of active compensation for movement having maximum amplitude of 15 meters, 10 meters, 8 meters, 6 meters (ie typical height of waves during normal weather or working conditions).

[0021] According to an embodiment, in the control method, the system is initially attached to the crane or lifting system with a at most 80%, preferably at most 90%, preferably at most 98% charged auxiliary battery. In other words, the auxiliary battery is never fully charged, even when the active heave compensator is initially attached to the crane, to make sure there is never energy recovery that cannot be absorbed by the auxiliary battery.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Example embodiments will be more fully understood from the detailed description provided herein and the accompanying drawings, which are given by way of illustration only. In the present description and in the drawings. FIG.1 is a schematic view showing a vessel equipped with a mobile active heave compensation system; FIG.2 is a schematic view showing a mobile active heave compensation system in accordance with the present invention and able to equip the vessel of FIG.1; FIG.3 is a schematic view showing an electrically driven actuator to be used in the mobile active heave compensation system of FIG.2 and comprising spur gear mounted electric motors; FIG.4 is a schematic view similar to the one of FIG.2 showing an alternative embodiment of the mobile active heave compensation system comprising additional components; FIG.5 is a schematic view showing an alternative embodiment for the compensator wherein the electrically driven actuator is supported by a non-adjustable passive system.

[0023] It should be noted that these figures are intended to illustrate the general characteristics of methods, structure and / or materials utilized in the described exemplary embodiments. The drawings are not to scale and should not be interpreted as limiting the range of values or properties encompassed by the exemplary embodiments.DETAILED DESCRIPTION

[0024] As shown on figures 1 and 2, the present invention proposes a mobile active heave compensation system 10 provided with a first attachment device 12 allowing said mobile active heave compensation system 10 to be suspended from a load bearing device 14. The mobile active heave compensation system 10 is provided with a second attachment device 16 allowing said mobile active heave compensation system 10 to carry a payload 18.

[0025] In the present application, mobile for the active heave compensation system 10 refers to the fact that the system is self-contained and can be swapped between load bearing devices. In the present case, the active heave compensation system 10 is an independent, separate unit that is not made as an integral part of a crane or a lifting unit. It may be transported between different lifting vessels if and when required. It can be temporarily suspended from a lifting device.

[0026] The mobile active heave compensation system 10 comprises: a control unit 20, a heave compensation part 22 comprising an electrically driven actuator 24, a sensor arrangement 26 producing input signals for said control unit to control the heave compensation part 22, an electric power source 28 provided with supercapacitors 30, such that, in a first heave compensation phase, electric power is stored in said supercapacitors 30 and, in a second heave compensation phase, electric power stored in said supercapacitors 30 is supplied to said electrically driven actuator 24.

[0027] During the first heave compensation phase, the heave compensation part 22 extends and generates electric energy. During the second heave compensation phase, the heave compensation part 22 retracts which consumes electric energy.

[0028] Advantageously, the mobile active heave compensation system 10 comprises an auxiliary battery 32. It allows for longer period of operation of the system 10 and compensate for energy losses. Additional power sources can also be provided to the system 10 as additional batteries, a generator, etc.

[0029] Advantageously, the mobile active heave compensation system 10 comprises an energy management system 34 which implement different strategies regarding the supply of electricity to the electrically driven actuator 24. The electricity can be supplied by the auxiliary battery 32 or by the supercapacitors 30. Also, electricity generated during the first heave compensation phase can be supplied to the auxiliary battery 32 or to the supercapacitors 30, or to both, depending on the strategy and charging status of these components.

[0030] In the present embodiment, electrical power is supplied by the electrical power source 28 to the heave compensation part 22 through a DC / AC converter 35 in order to supply alternative current.

[0031] The mobile active heave compensation system 10 is provided with at least one heave compensation part 22. Alternatively, additional heave compensation parts 22 could be included in the system 10. The system 10 is regulated by a sensor arrangement 26 and is driven by the electric driven actuator 24. Lowered load energy can be recovered and stored in the supercapacitors 30 in combination with the auxiliary battery 32.

[0032] Low loads can be hoisted using a rack-and pinion design. Higher loads can utilize a winch design or a rocker design where a pipe is bended over a radius.

[0033] Preferably, the electrically driven actuator 24 uses spur gear mounted electric motors 36 as shown on figure 3.

[0034] An alternative embodiment is shown on figure 4 wherein the electric power source 28 comprises additional components allowing more flexibility for managing the system power supply.

[0035] A power cable 38 connects the electric power source 28 of the system 10 to an external power source such as the power source of the vessel. It makes the system redundant and / or provides an auxiliary source for charging the auxiliary battery.

[0036] The electronic control unit 20 and the energy management system 34 are able to control force and / or position of the heave compensation part 22. The energy management system 34 manages the energy flow.

[0037] Advantageously, the electric power source 28 comprises a brake resistor device 40 which can consume energy excess during the first heave compensation phase by converting it into heat. This brake resistor device 40 is controlled by the energy management system 34.

[0038] Preferably, a bypass circuit 42, controlled by the energy management system 34 is connected to each supercapacitor 30 to control pre-charge and discharge of the supercapacitors 30.

[0039] According to the embodiment shown, a DC / DC converter 44 is arranged in the circuit to generate a voltage step between the auxiliary battery 32 and the remaining of the electric circuit, which allow better management of battery discharge phase.

[0040] According to the embodiment shown, an electric filter circuit 46 is provided between the electric power source 28 and the heave compensation part 22 to remove harmful harmonics and to prevent damage to the electrically driven actuator 24 by overheating.

[0041] Advantages of the mobile active heave compensation system 10 include: No need to load gas springs which provides for increased uptime, increase in operational availability of the system and facilitate fast transfer of loads, The energy system can be shared with the vessel via umbilical, Almost instantaneous torque / force on the system, Simple design allows for quick engineering process for new loads, Less complex system, therefore reduction in maintenance time and amount of spare parts required.

[0042] The mobile active heave compensation system 10 is characterized in that the compensator is powered by an electric power source in combination with the energy storage capacity of supercapacitors 30 that allows bi-directional energy flow to the electrically driven actuator 24.

[0043] The mobile active heave compensation system 10 allows to get rid of a complex passive compensation system using adjustable gas pressure systems. The mobile active heave compensation system 10 allows to recover the potential energy due to vessel motions in the supercapacitors 30.

[0044] In addition, the kinetic energy of the moving components can be stored in the supercapacitors 30 as well.

[0045] The mobile active heave compensation system 10 can do quick lifts, the process is reversable as long as power is available.

[0046] The mobile active heave compensation system 10 is simpler, not prone to leakage (environmental spillage) and requires less maintenance. Additionally, the response time of the system is almost instantaneous.

[0047] Other sources of energy can be connected to make the power supply redundant. This can be an auxiliary power cable 38 from the crane hook to vessel's deck or a battery system in the hook.

[0048] Another alternative embodiment is shown on figure 5 wherein the electrically driven actuator 24 is supported by a non-adjustable passive system 52. Said non-adjustable passive system 52 may comprise for example a gas spring cylinder 48 and a gas reservoir 50. This gas spring cylinder 48 could be very simple and calibrated to compensate only part of the load, for example 50% of the regular load for which the system 10 is designed. Such gas spring cylinder 48 is not adjustable like some complex and expensive device that are designed to compensate for approximately 100% of the load to be hoisted.LEGEND

[0049] 10 : mobile active heave compensation system 12 : first attachment device 14 : load bearing device 16 : second attachment device 18 : payload 20 : control unit 22 : heave compensation part 24 : electrically driven actuator 26 : sensor arrangement 28 : electric power source 30 : supercapacitors 32 : auxiliary battery 34 : energy management system 35: DC / AC converter 36: spur gear mounted electric motors 38: power cable 40: brake resistor device 42: bypass circuit 44: DC / DC converter 46: electric filter circuit 48: gas spring cylinder 50: gas reservoir 52: non-adjustable passive system

Claims

1. A mobile active heave compensation system (10) provided with a first attachment device (12) allowing said mobile active heave compensation system (10) to be suspended from a load bearing device (14) and provided with a second attachment device (16) allowing said mobile active heave compensation system (10) to carry a payload (18), said mobile active heave compensation system (10) comprising: - a control unit (20), - a heave compensation part (22) comprising an electrically driven actuator (24), - a sensor arrangement (26) producing input signals for said control unit (20) to control the heave compensation part (22), - an electric power source (28) provided with supercapacitors (30), such that, in a first heave compensation phase, when the heave compensation part (22) generates energy, electric power is stored in said supercapacitors (30) and, in a second heave compensation phase, when the heave compensation part (22) requires energy, electric power stored in said supercapacitors (30) is supplied to said electrically driven actuator (24).

2. The mobile active heave compensation system (10) according to claim 1 comprising at least one of an auxiliary battery (32) and an auxiliary power cable (38) which are controlled by an energy management system (34).

3. The mobile active heave compensation system (10) according to claim 1 or 2 wherein the electrically driven actuator (24) uses spur gear mounted electric motors (36).

4. The mobile active heave compensation system (10) according to any of the preceding claims, wherein the electrically driven actuator (24) is supported by a non-adjustable passive system (52).

5. The mobile active heave compensation system (10) according to any of the preceding claims, wherein the electric power source (28) comprises a brake resistor device (40) able to consumes excess of energy supply during the first heave compensation phase.

6. The mobile active heave compensation system (10) according to any of the preceding claims, wherein each supercapacitor (30) is provided with a bypass circuit (42) to control pre-charge and discharge.

7. The mobile active heave compensation system (10) according to any of the preceding claims, wherein the auxiliary battery (32) is provided with a DC / DC converter (44) to allow a bigger discharge of the auxiliary battery (32).

8. The mobile active heave compensation system (10) according to any of the preceding claims, wherein an electric filter circuit (46) is provided to protect the electrically driven actuator (24).

9. A control method for a mobile active heave compensation system (10) according to any of the preceding claims, comprising the steps of: - storing electric power in said supercapacitors (30) during a first heave compensation phase, when the heave compensation part (22) generates energy, and - supplying electric power to said electrically driven actuator (24) during a second heave compensation phase, when the heave compensation part (22) requires energy.

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