DISTRIBUTION OF ELECTRIC ENERGY ON A VESSEL

Abstract

A stored electric energy distribution arrangement for distribution of stored electric energy on a vessel having one or more AC consumers, in the event of failure of a primary electric energy supply to the AC consumers has a DC-circuit. The DC circuit has a plurality of backup electric energy storage elements connected in a ring, for supplying stored electric energy to one or more AC consumers in the event of failure of the primary electric energy supply. A plurality of breaker systems are provided in the DC circuit for disconnecting one or more backup electric energy storage elements from the DC-circuit, in the event of a fault associated with that backup element.

Claims

1. A stored electric energy distribution arrangement for distribution of stored electric energy on a vessel, the vessel comprising one or more AC consumers, in the event of failure, or insufficiency, of a primary electric energy supply to the AC consumers, the arrangement comprising: a DC-circuit comprising a plurality of backup electric energy storage elements connected in a ring, for supplying stored electric energy to one or more AC consumers in the event of failure of the primary electric energy supply; and a plurality of breaker systems in the DC circuit for disconnecting one or more backup electric energy storage elements from the DC-circuit, in the event of a fault associated with that backup element.

2. The stored electric energy distribution arrangement according to claim 1, wherein the primary electric energy supply comprises an AC main grid.

3. An arrangement for distribution of electric energy on a vessel, comprising: an AC main grid adapted to supply electric energy to one or more AC consumers in normal operation; a DC-circuit comprising a plurality of electric energy storage backup elements connected in a ring, for supplying electric energy to the one or more AC consumers in the event of failure of the main grid; and a plurality of breaker systems in the DC circuit for disconnecting one or more backup elements from the DC-circuit, in the event of a fault associated with that backup element.

4. The arrangement according to claim 1, wherein at least one breaker system comprises two breaker units connected on each side of a backup element connected within the DC-circuit.

5. The arrangement according to claim 4, wherein the breaker unit is adapted to, upon detection of a failure, disrupt, or break a connection to the DC-circuit in a time of between 5 μs and 500 μs,

6. The arrangement according to claim 5, wherein the connection is disrupted or broken in a time of between 10 μs and 100 μs,

7. The arrangement according to claim 5, wherein the connection is disrupted or broken in a time of between 10 μs and 20 μs.

8. The arrangement according to claim 4, wherein the breaker unit is adapted to detect a failure by measurement of current and/or voltage on each side at a frequency of between 50 kHz and 500 kHz,

9. The arrangement according to claim 8, wherein the measurement is at a rate of between 150 kHz and 250 kHz.

10. The arrangement according to claim 4, wherein the breaker unit is adapted to disrupt, or break a connection to the DC-circuit, if the current measured on at least one side is larger than a current threshold and/or if a voltage difference measured on both sides is larger than a voltage difference threshold.

11. The arrangement according to claim 1, wherein each of the backup elements comprises an energy storage unit, for storing electric energy for use in a failure situation.

12. The arrangement according to claim 11, wherein the energy storage unit comprises a battery.

13. The arrangement according to claim 11, wherein the energy storage unit is connected to the DC-circuit via a DC-DC-converter adapted to control input and output current and/or input and output voltage using pulse width modulation.

14. The arrangement according to claim 1, wherein an AC-consumer is connectable to the DC-circuit via an inverter system.

15. The arrangement according to claim 1 wherein the AC consumer comprises one or more of a variable speed drive, a thruster, or auxiliary equipment.

16. The arrangement according to claim 15, wherein the thruster receives energy from the DC-circuit via four inverters of the inverter system.

17. The arrangement according to claim 1, further comprising: an AC-bar, having plural generators connected thereto.

18. The arrangement according to claim 17, wherein the AC-bar is connectable to at least one other AC-bar to form an AC-ring.

19. The arrangement according to claim 17, wherein the AC-bar, is connectable to at least one of the backup elements via a transformer, a diode and a rectifier system, wherein the diode is adapted to block an energy stream from the DC-circuit to the AC-bar.

20. The arrangement according to claim 19, wherein the AC-bar operates at a voltage of between 5 kV and 15 kV.

21. The arrangement according to claim 19, wherein the transformer transforms to a voltage of between 500 V and 1000 V.

22. The arrangement according to claim 19, wherein the transformer has one set of primary windings and two sets of secondary windings, wherein the rectifier system comprises two rectifiers connected to the two sets of secondary windings of the transformer.

23. The arrangement according to claim 19, wherein the transformer and the rectifier system are separated from the backup element and housed in different casings.

24. The arrangement according to claim 19, wherein the transformer, is housed together with the backup element in one casing.

25. A method for operating a stored electrical energy distribution arrangement for distribution of electric energy on a vessel comprising one or more AC consumers, the method comprising: detecting a failure in a DC-circuit having a plurality of backup electrical energy storage elements connected in a ring for supplying stored electrical energy to the one or more AC consumers in the event of failure of the primary electric energy supply; and disconnecting one of the backup elements from the DC-circuit using a plurality of breaker systems, in the event of a fault associated with that backup element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Examples of an arrangement and method according to the present invention will now be described with reference to the accompanying drawings in which:

[0048] FIGS. 1a to 1d schematically illustrate a circuit diagram of an arrangement for distribution of electric energy according to an embodiment of the present invention; and

[0049] FIGS. 2a to 2d schematically illustrate a circuit diagram of an arrangement for distribution of electric energy according to another embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION

[0050] The illustration in the drawings is in schematic form. It is noted that in different figures, similar or identical elements are provided with the same reference signs or with reference signs, which are different from the corresponding reference signs only within the first digit.

[0051] The arrangement 100 for distribution of electric energy on a vessel illustrated in FIGS. 1a to 1d comprises a DC-circuit 101 having a plurality of backup elements 103 (assembled in a similar or the same way and having similar or the same components) connected in a ring, formed by cable sections or bar sections 105. The backup elements 103 are connected in a ring during normal operation. Each backup element comprises a breaker system 107 comprising two breaker units 109 on each side of each backup element 103. Each breaker unit 109 comprises two power transistors connected in series such that each breaker system is adapted to disrupt a connection from a backup element to the DC-circuit 101 within a few microseconds. In this example, the breaker units are ILC insulated gate bipolar transistor (IGBT) breakers, but other suitably fast breakers may be used. The disconnection may for example occur in the event of a failure. For detection of such a failure, each breaker unit 109 comprises measurement sensors and control logic that disconnects or disrupts a connection if, for example, a measured current is above a current threshold and/or a measured voltage difference between the two sides is above a voltage threshold. The voltage and/or current may be measured at a rate of between 150 kHz and 250 kHz.

[0052] The backup element 103 further comprises an energy storage unit 111, such as a battery or an accumulator. The energy storage unit 111 is connected to the DC-circuit 101 or a cable section 105 via a DC-DC-converter 113 and a further switch 115. For the example shown, the energy storage unit is able to provide 1.25 MW for up to 60 minutes, but other storage capacities may be chosen according to the requirement.

[0053] Via an inverter system 117 comprising four inverters 119, the DC-circuit 101 is connectable, via a switch 121, to an AC-consumer 123. I the example illustrated the AC consumer is an essential thruster 123, rated at 5.5 MW, but the actual type of consumer and its rating depend upon the application. For this example, the vessel being supplied with electric energy by the arrangement 100 comprises eight thrusters 123, in order to properly position the vessel on the sea, shown as two aft port thrusters and two forward port thrusters 123 in FIGS. 1a and 1b and two aft starboard thrusters and two forward starboard thrusters 123 in FIGS. 1c and 1d. More or fewer thrusters may be provided.

[0054] The arrangement 100 further comprises an AC-bar 125 (AC bus bar) that has a plurality of generators 127 connected or connectable thereto, in particular via switches 129. Via further switches 131, the AC-bar 125 is connectable to the DC-circuit 101 (and thus to the backup elements 103) via a transformer 133 which for example transforms an 11 kV AC power stream to a DC-voltage between 500 V and 1000 V, in particular about 930 V. Switches 131 also allow the AC-bar to be connected to a utility transformer 170, or drilling transformer 171.

[0055] The down transformed voltage is further rectified by a rectifier system 135 connected between the transformer and the DC-bar 105, i.e. the DC-circuit 101. Furthermore, a diode 136 is connected between the transformer 133 and the rectifier system 135, in order to block energy flow from the DC-circuit 101 to the AC-bar 125.

[0056] In particular, the rectifier system 135 comprises two rectifiers 137 which are connected to two secondary windings 139 of the transformer 133 having one primary winding 141 inductively coupled to the two secondary windings 139.

[0057] The backup element 103 further comprises a consumer inverter 163 connected to the DC-circuit 101 and providing an AC power stream via a filter element 165 and a consumer transformer 167 to an auxiliary consumer 169, such as a pump for a bearing or the like, or thruster auxiliary. In this example, the consumer is rated at 690V, but the rating depends upon the specific consumer.

[0058] As is illustrated in FIGS. 1c and 1d, the arrangement 100 further comprises another AC-bar 143 having further generators 145 connected thereto in a similar manner as for those connected to the AC-bar 125. Via a connection system 147 comprising switches 149, the AC-bar 125 may be connected with the other AC-bar 143. Similarly, the other AC-bar 143 may be connected, via other transformers 151 and another inverter system 153 to another DC-circuit 155 comprising other cable sections or DC-bars 158. Other backup systems 157, constructed as the backup systems 103, are connectable in a ring configuration to the other DC-circuit 155. Other breaker systems 159 each comprising two breaker units 161 are provided in the other backup elements 157, in order to disrupt a connection from the backup unit 157 to the other DC-circuit 155 in case of a failure, for example failure of an adjacent or another further backup element 157 in the DC-circuit 155 configured in a ring.

[0059] Features in the two sections of the arrangement 100 of FIG. 1 which are similar in structure and/or function are labeled with the same reference signs.

[0060] In the present invention, an arrangement for distribution of stored electric energy on a vessel is such that there is flow of energy from an AC bar main grid to an AC consumer in normal operation; and, there is flow of energy from a DC bar to the AC consumer, in the event of failure of the AC main grid, or failure of sub-components of the AC consumer. This failure may be addressed by a DC-circuit having a plurality of backup elements connected in a ring; and a plurality of breaker systems for disconnecting a particular backup element from the DC-circuit.

[0061] During normal operation, the generators 127 may generate electric energy which may flow via the AC-bar 125, the transformer 133, the rectifier system 135 and the inverter system 117 to the thrusters 123. Further, the energy from the generators 127 may flow via the transformer 133 and the rectifier 135 to the backup elements 103 and within the backup elements 103 via the DC-DC-converter 113 to the energy storage unit or battery 111 for charging the battery 111 under normal conditions.

[0062] In case of a failure in the AC-bar 125 (also called main grid), the switches 131 may be opened and the thrusters 123 may be powered from energy stored in the battery 111 which flows via the DC-DC-converter 113 and the inverter system 117 to the thrusters 123.

[0063] In case of a failure in one of the backup elements 103, the breaker system 107 comprising the breaker units 109 may disconnect the failed backup unit 103 from the DC-circuit 101 such that the failed backup system 103 does not interfere with the operation of the other backup systems 103.

[0064] FIG. 2 schematically illustrates a circuit diagram of another arrangement 200 for distributing electrical energy on a vessel according to an embodiment of the present invention.

[0065] The arrangement 200 has elements in common with the system 100 illustrated in FIG. 1 which are labeled with reference signs differing only in the first digit. A description of these elements can be taken from the description referring or associated with FIG. 1. The examples are given for the same ratings and consumer types as in FIG. 1, but as indicated above the specific voltage, battery capacity and types of essential consumers depend upon the application and are not limited to the values given in the examples.

[0066] A difference between the arrangements 100 and 200 is the assembly of several systems in one or several casings or switchboards. In FIG. 1, the transformer 133, the rectifier system 135, the inverter system 117 and the thrusters 123 are separated from the backup elements 103. The backup elements 103, including the battery 111, the DC-DC-converter 113 and also the elements 163, 165, 167 for powering auxiliary consumers 169 may for example be assembled into one casing or switchboard.

[0067] By contrast, in the arrangement 200 illustrated in FIG. 2, the transformer 233, the rectifier system 235 and the inverter system 217 are assembled together with the battery 211, the DC-DC-inverter 213 and also with the elements 263, 265, 267 together in one casing 271. The thrusters 223 and also the auxiliary AC-consumers 269 may be arranged outside the casing 271 and may be connectable thereto using appropriate sockets, plugs and cabling.

[0068] As in the arrangement 100 illustrated in FIG. 1, the DC-circuit 201 comprising the DC cable sections 205 is also configured in a ring harboring the backup elements 203 which may be disconnected by operating the breaker systems 207. When the breaker systems 207 disconnect a failed backup system, no interference with the main power grid 225 or 243 is present. The rectifier diodes 236 block power flowing back to the main grid 225, 243. The breaker systems 207 comprising breaker units 209 may disconnect the backup element 203, 257 in a very fast manner, such as within 10 to 20 μs. The batteries 211 may be arranged in the same fire zone as the auxiliary consumers, such as different thrusters 269. Thereby, high security and high reliability of the operation of the vessel may be achieved.

[0069] It should be noted that the term “comprising” does not exclude other elements or steps and “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.