WO2018050227A1

WO2018050227A1 - Electric power system of a vessel

Info

Publication number: WO2018050227A1
Application number: PCT/EP2016/071807
Authority: WO
Inventors: Pasi Pohjanheimo; Klaus Vänskä; Matti Lehti
Original assignee: Abb Schweiz Ag
Priority date: 2016-09-15
Filing date: 2016-09-15
Publication date: 2018-03-22

Abstract

An electric power system of a vessel comprising an AC busbar arranged to carry AC power, the AC busbar comprising a first busbar section (102A, 102B) operable in a fixed frequency mode. The AC busbar comprises a second busbar section (102C) being either connectable to the first busbar section (102A, 102B) for operation in a fixed frequency mode, or being separable from the first busbar section for operation in a variable frequency mode simultaneously with the first busbar section being operated in a fixed frequency mode.

Description

ELECTRIC POWER SYSTEM OF A VESSEL

FIELD

The present invention relates to electric power system of vessel. BACKGROUND

Traditionally the power system of the vessel has been operated at a fixed frequency. That is, however, inefficient from the fuel consumption perspective. Some attempts to suggest variable frequency networks have been provided but they have the disadvantage of resulting into complicated overall network structures.

An improved system and method to operate a power system of a vessel is thus called for.

SUMMARY

An object of the present invention is to provide an apparatus and a method which are defined in the independent claims. Some embodiments are dis- closed in the dependent claims.

DRAWINGS

In the following, the invention will be described in greater detail by means of some embodiments with reference to the accompanying drawings, in which

Figure 1 shows an overview of a power system of a vessel;

Figure 2 shows an embodiment of operation of the power system;

Figure 3 shows an embodiment of operation of the power system;

Figure 4 shows an embodiment of operation of the power system;

Figure 5 shows an embodiment of operation of the power system;

Figure 6 shows an embodiment of operation of the power system; and

Figure 7 shows an overview of a power system of a vessel.

DETAILED DESCRIPTION

The embodiments relate to marine vessels/ships, both for civil and military use. Specifically, the embodiments relate to the electric power system of the vessel. In the embodiments, there is provided an alternating current (AC) busbar, and one or more power generators feeding electricity to the AC busbar. The generators are powered by respective prime movers, such as diesel motors.

In the embodiments, the AC busbar is provided with one or more bus-tie breakers, which are capable of splitting the busbar into one or more sections. Alternatively, when the tie-breakers are closed, the AC busbar sections are connected.

In the embodiments, the AC busbar can be operated in a first operation mode, where all the bus tie-breakers are closed and the whole AC network is op- erated with a fixed frequency. The nominal frequency can be 50 Hz or 60 Hz, for instance. In this operation mode, the number of power generators feeding the AC busbar can be increased or decreased according to the load on the busbar.

In another operation mode, the AC busbar can be divided into one more sections having the nominal fixed frequency.

Figure 1 shows an embodiment of a general structure of a power system 100 of a vessel/ship. In the exemplary embodiment of Figure 1 , the network is divided into two main sections. The first section is a fixed frequency section and comprises two mutually connectable subsections 102A, 102B. The nominal frequency in the fixed frequency network may be either 50 Hz or 60 Hz, for instance.

The fixed frequency network is arranged to serve consumers such as the hotel consumers 120 and auxiliary systems 130, such as transverse thrusters and air conditioning systems.

The second section is a variable frequency section 102C serving mainly the propulsion drives 122A, 122B accepting variable frequency. The frequency in the variable frequency section may vary between 10 to 90 Hz, preferably between 30 to 75 Hz, even more preferably between 45 to 65 Hz.

Figure 1 shows four generators 108A to 108D for providing electricity to the power system 100 of the ship. The set of generators may be arranged in a father-son configuration such that there is a set of main generators 108B, 108C for mainly supporting the propulsion units 122A, 122B, and a set of auxiliary generators 108A, 108D, which may be of smaller powering capacity than the main generators 108B, 108C. The auxiliary generators may be flexibly connected to either the fixed frequency sections 102A, 102B or to the variable frequency section 102C. There are illustrated two bus tie-breakers 106A, 106B for connecting the first auxiliary generator 108A to either the fixed frequency network 102A, 102B or the variable frequency network 102C, or to both networks. It is noted that by closing the tiebreakers 106A, 106B, also the generator 108B may be connected to the fixed fre- quency network 102A.

The network of Figure 1 can be operated in two basic operation modes. In a first operation mode, the bus tie-breakers in the bus 102A, 102B, 102C are closed and fixed frequency is applied in the whole network. In this embodiment, also the network section where the propulsion units are located, is fed with the fixed frequency.

In a second operation mode, at least some of the bus tie-breakers, such as the tie-breaker 106B is open and the network is divided into fixed frequency sections 102A, 102B and variable frequency section 102C. In an embodiment, the second operation mode when the network sections are separated is applied while at open sea. In port, either of the operation modes can be applied.

Although Figure 1 illustrates the main generators and auxiliary generators as having different power generation capacity, they can alternatively also be similar.

The various alternatives or operating the power system are further ex- plained with reference to the accompanying drawings.

Figure 2 shows an embodiment, which may be applied when the vessel is in port and is stationary. In this embodiment, the energy need is low, and for instance the main generators 108B, 108C may be offline so that they are not feeding the network.

In this embodiment, all the bus tie-breakers between and within the first

102A, 102B and second 102C network sections are closed such that the whole bus is operated with a common fixed frequency, such as 60 Hz. In this embodiment, one of the auxiliary generators 108A is sufficient for satisfying the energy needs of the hotel network 120 and the air conditioning (A/C) system that is the only auxiliary system connected to the bus 102A in Figure 2.

Figure 3 shows a first maneuvering state in which the main propulsion units 122A, 122B are being operated. To satisfy the power needs of the propulsion units, the main generators 108B, 108C are operational as well as one of the auxil- iary generators 108A. All the bus tie-breakers are closed and fixed frequency is applied through the network because the e.g. the hotel network needs invariable frequency. The propulsion motors can be operated with the supplied fixed frequency.

In the arrangement of Figure 3, the bow thrusters BT can connect to the bus without associated frequency converters, which provides a cost effective solution.

It is noted that the bow thrusters that are connected to the fixed frequency network have a great power consumption, whereby it is to be ensured that the power generation capacity to fulfil the power needs of the fixed frequency network is provided.

Figure 4 shows a second maneuvering state, where the main generators and two auxiliary generators are operational. However, the network is split to fixed and variable frequency sections such that the two main generators serve the variable frequency network and the two auxiliary generators are arranged to serve the fixed frequency network sections.

Figure 5 shows an embodiment applicable at sea, for instance. Compared to Figure 4, one of the auxiliary generators is offline and one of the generators is responsible for providing energy to the whole fixed frequency network.

Figure 6 shows a still further embodiment, which may be applied at sea in a situation where the propulsion system needs plenty of energy. In this embodiment, the two main generators and one of the auxiliary generators are arranged to feed the variable frequency network and the fixed frequency network is taken care by one auxiliary generator.

In Figure 7 the two network sections are connected and fixed frequency is applied in the whole network. All generators are arranged to feed the fixed frequency network.

In the embodiments, there is provided an electric power system of a vessel comprising an AC busbar arranged to carry AC power, the AC busbar com- prising a first busbar section operable in a fixed frequency mode, the AC busbar comprises a second busbar section being either connectable to the first busbar section for operation in a fixed frequency mode, or being separable from the first busbar section for operation in a variable frequency mode simultaneously with the first busbar section being operated in a fixed frequency mode. There may thus be a first busbar section that is always operated in the fixed frequency mode. Such network section may, for instance, comprise the so called hotel network serving the customers of a cruise ship, for example.

The power system may comprise one or more power generators for generating power to the AC busbar in the fixed frequency mode and in the variable frequency mode. The power system may comprise a plurality of power generators, which may have the same or different power generation capabilities. In a first embodiment all the power generators have the same power generation capability. In a second embodiment, some of the power generators may have a higher power generation capability than the others. In some embodiments, there are father generators mainly provided for feeding the propulsion system of the vessel, and son generators mainly feeding the hotel network of the vessel.

In some embodiments, the propulsion system is connected to the sec- ond busbar section being alternately operable in the fixed frequency mode or in the variable frequency mode.

In some embodiments, the power system comprises one or more propulsion systems, which propulsion systems are connected to the AC busbar via one or more frequency converters. Thereby the rotation rate of the propellers may be adjusted as desired being between 0-130 rpm, for instance. The rotation rate of the propellers may be thereby adjusted independent of the frequency of the AC network of the vessel.

In some embodiments, the power system comprises one or more bow thrusters connected to the fixed frequency network section without associated fre- quency converters. This is a cost effective solution as no frequency converters are needed. In order to achieve this, sufficient fixed power generation capacity may be arranged by providing flexibility in connecting the needed amount of power generators to the fixed frequency network.

In an embodiment, the power system comprises bus tie breakers on each side of a connection point of power generator to the busbar connecting and disconnecting each power generator to/from the busbar.

In some embodiments, the fixed frequency of the network may be either substantially 50 Hz or substantially 60 Hz. In some embodiments, the variable frequency when at least part of the AC network is operated in the variable frequency mode is between 10 to 90 Hz, preferably between 30 to 75 Hz, even more preferably between 45 to 65 Hz.

In the embodiments, there is provided a method of providing electric power for a vessel having an AC busbar arranged to carry AC power. The AC busbar can be operated in a first operation mode when a fixed frequency is applied in the whole busbar and in a second operation mode when one or more sections of the AC busbar are operated with a fixed frequency, and one or more sections of the busbar are operated with a variable frequency simultaneously when one or more sections of the busbar are operated with the fixed frequency.

In the embodiments, at least one of the power generators feeding the AC busbar is connectable to the AC busbar in the first operation mode and is con- nectable for feeding the variable frequency section in the second operation mode. There may thus be one or more generators that are flexibly connected to feed power to the network in all the operation modes of the network.

In some embodiments, when the vessel is stationary or operated in a manoeuvring operating mode, the AC busbar is operated in the first operation mode, that is, with a fixed frequency.

When the vessel is operated in a cruising operation mode, the AC bus- bar may be operated in the second operation mode and the propulsion units are connected to the AC busbar section having a variable frequency.

In the embodiments there is thus disclosed a power network system for a vessel. The network may be split into at least two sections, in which at least one of the networks is operated in fixed frequency, and one of the sections may alter- natively be operated in fixed or variable frequency modes.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. An electric power system of a vessel comprising an AC busbar arranged to carry AC power, the AC busbar comprising a first busbar section (102A, 102B) operable in a fixed frequency mode, characterized in that the AC busbar comprises a second busbar section (102C) being either connectable to the first busbar section (102A, 102B) for operation in a fixed frequency mode, or being separable from the first busbar section for operation in a variable frequency mode simultaneously with the first busbar section being operated in a fixed frequency mode.

2. An electric power system of a vessel according to claim 1, characterized in that the power system comprises one or more power generators (108A-108D) for generating power to the AC busbar in the fixed frequency mode and in the variable frequency mode.

3. An electric power system of a vessel according to any preceding claim, characterized in that the power system comprises a propulsion unit (122A, 122B) for providing propulsion power for the vessel, which propulsion unit is connected to the second busbar section (102C) being alternately operable in the fixed frequency mode or in the variable frequency mode.

4. An electric power system of a vessel according to any preceding claim, characterized in that the power system comprises a first set of power generators having one or more power generators (108B, 108C) having a first power generation capacity, and a second set of power generators having a second power generation capacity (108A, 108D), where the first power generation capacity is higher than the second power generation capacity.

5. An electric power system of a vessel according to any preceding claim, characterized in that at least one of the power generators (108B, 108C) of the first set of power generators is connected to the second busbar section (102C) when operated in a variable frequency mode.

6. An electric power system of a vessel according to any preceding claim, characterized in that the power system comprises one or more propulsion systems (122A, 122B), which propulsion systems (122A, 122B) are con- nected to the AC busbar via one or more frequency converters (124A, 124B).

7. An electric power system of a vessel according to any preceding claim, characterized in that the power system comprises one or more bow thrusters (BT) connected to the fixed frequency network section (102A) without associated frequency converters.

8. An electric power system of a vessel according to any preceding claim, characterized in that the power system comprises bus tie breakers (106A, 106B) on each side of a connection point of power generator (108A) to the busbar (102A) connecting and disconnecting each power generator to/from the busbar.

9. An electric power system of a vessel according to any preceding claim, characterized in that fixed frequency is either substantially 50 Hz or substantially 60 Hz.

10. An electric power system of a vessel according to any preceding claim, characterized in that variable frequency is between 30 Hz to 90 Hz.

11. A marine vessel comprising an electric power system according to any preceding claim.

12. A method of providing electric power for a vessel having an AC busbar arranged to carry AC power, characterized in that the AC busbar can be operated in a first operation mode when a fixed frequency is applied in the whole busbar (102A, 102B, 102C) and in a second operation mode when one or more sections (102A, 102B) of the AC busbar are operated with a fixed frequency, and one or more sections (102C) of the busbar are operated with a variable fre- quency simultaneously when one or more sections of the busbar are operated with the fixed frequency.

13. A method according to claim 12, characterized in that at least one of the power generators feeding the AC busbar is connectable to the AC busbar in the first operation mode and is connectable for feeding the variable frequency section (102C) in the second operation mode.

14. A method according to claim 12 or 13, characterized in that when the vessel is stationary or operated in a manoeuvring operating mode, the

AC busbar is operated in the first operation mode.

15. A method according to any of the claims 12 to 15, characterized in that when the vessel is operated in a cruising operation mode, the AC busbar is operated in the second operation mode and the propulsion units (122A, 122B) are connected to the AC busbar section (102C) having a variable frequency.