KR20190142738A - Lng carrier applied with low-voltage distribution - Google Patents

Abstract

Embodiments relate to an LNG carrier having an essence load and a service load, which includes: a first power system associated with the essence load; and a second power system associated with the service load. A thruster motor is associated with the second power system. The LNG carrier further includes a switching part formed to be switched and transmitting power generated in the first power system to the thruster motor of the second power system.

Description

LNG Carrier with Low Pressure Distribution {LNG CARRIER APPLIED WITH LOW-VOLTAGE DISTRIBUTION}

The present invention relates to LNG carriers to which low-voltage distribution is applied, and more specifically, LNG carrier power loads divided into essential loads and service loads are separated into different power systems according to load characteristics. A power system capable of low voltage distribution (e.g., 440V) and capable of powering the load through alternating and / or direct current distribution optimized for load power requirements within the essential load system and / or service load system It is related to the LNG carrier applied.

LNG is generally stored in specially designed cargo tanks for transport by sea at cryogenic temperatures (eg -160 ° C). It is impossible to transport LNG by sea without controlling the temperature and pressure of the cargo tank during normal sailing.

Thus, the LNG Carrier is configured to be propelled to operate the ship and at the same time configured to safely transport the LNG.

Power loads in LNG carriers may include mandatory loads associated with operations (eg, Essential & Important Load-Fuel oil supply pumps, Fuel valve cooling pumps, etc.) and service loads not associated with operation (eg, Service Load).

Essential loads in LNG carriers are electric motors for propulsion and navigation, such as a Thruster Motor, a Propulsion Motor, a Cooling Sea Water Pump, and an L.O Pump. Service loads in LNG carriers are designed to use LNG storage loads configured to operate cooling and compression process systems according to the external temperatures of pipelines and cargo tanks of LNG carriers, and to use BOG (Boil-Off Gas) generated from LNG as fuel. Contains loads for LNG fuel.

The essential load and the service load of the LNG carrier may include a continuous load consuming a constant power during operation, and a variable load whose power consumption varies according to the driving characteristics. Typically, LNG carriers are powered by an AC power supply system and are linked to a single power system with a mixture of continuous and variable loads.

In the conventional case, the essential load for propulsion and service loads such as LNG storage loads and LNG fuel loads are configured in a single system, and the power capacity of the entire system is very large. Powering all the loads of large LNG carriers in a single system will lead to a surge in power supply cables. In addition, most of the power load of LNG carriers except the large motor load has a low voltage of 690V or less as a rated voltage. When the power system is designed to supply power at low voltage below 690V directly from the generator, very high current flows through the switchboard due to the low distribution voltage to the grid capacity. Therefore, in order to protect the system accident due to the high current in the system, an expensive high-pressure cut-off facility is required. If the rated rectification is more than 4000 ~ 5000A, there is no commercial shutdown facility, so the single power system has a limitation in the low voltage-based power supply due to the capacity limitation.

Therefore, in the case of LNG carriers to which a power system of a certain size or more is applied, power is supplied to the load by generating power at a high voltage and converting it to a low pressure in order to solve the cable capacity and system capacity limitation due to the high current of the low voltage system. Have a system

Therefore, in order to supply power to all the loads of the LNG carrier, a high voltage distribution that transfers the power generated from the generator to high pressure is applied.

FIG. 1 is a diagram illustrating a system structure diagram of an LNG carrier power supply system configured as a single system by mixing essential loads and service loads according to an exemplary embodiment.

Referring to FIG. 1, a conventional LNG carrier power supply system in which essential loads and service loads are mixed in a single power system includes a high pressure power generation unit 10; High pressure switchboard 21; Transformers 31, 32, 33, 34 for depressurizing the high voltage electrical signal of the high voltage switchboard 21; Low pressure switchboards 41, 42, 43; It includes a load unit 50 in which a continuous load and a variable load are mixed.

As shown in FIG. 1, when the power supply system for a single-line LNG carrier is applied to an LNG carrier, when the system size is a certain size or more, even if the rated voltage of the load is low, the main distribution applies a high-voltage distribution and is connected to a sub-grid to which the load is connected. Power is supplied through the decompression transformers 31, 32, 33, 34 which decompress the high pressure to low pressure when branched.

If 6.6kV high voltage is applied to the switchboard 20 of FIG. 1, the power supply process to the load is as follows: 6.6kV generator-> 6.6kV high voltage main switchboard-> 6.6kV / 440V transformer- Low voltage sub-switchboard> 440V. That is, the power supply system for the LNG carrier of FIG. 1 generates power at high pressure, and decompresses it to low pressure to supply power to the load.

FIG. 2 is a diagram for explaining the internal structure of a conventional LNG carrier having the power supply system for the LNG carrier of FIG. 1.

Referring to FIG. 2, the LNG carrier 1000 includes an engine room 1030. The engine room 1030 includes various engine facilities such as generators, and other facilities connected to the engine facility, and the ECR switchboard room 1005, which is a space in which an engine control room (ECR) and / or a switchboard for controlling the engine is disposed. And a transformer room 1007, which is a space in which the decompression transformers 31, 32, 33, and 34 are disposed.

As described above, the power system of FIG. 1 to which the high voltage distribution is partially applied requires a large-capacity pressure reducing transformer 31, 32, 33, 34 to supply power to the load. Since the high pressure distribution is performed in the LNG carrier having a large load, the size of the transformer chamber 1007 in which the decompression transformers 31, 32, 33, 34 are arranged is considerable.

As a result, the available space in the ship is reduced by the space occupied by the plurality of pressure reducing transformers (31, 32, 33, 34 of FIG. 1).

In addition, the power supply system of Figure 1 is composed of a single power system has a low performance in terms of power generation efficiency.

Generators applied to LNG carriers are typically fixed RPM generators. The fixed RPM generator has a high fuel efficiency when generating power in the case where the load factor is a value between approximately 75 to 85%.

On the other hand, the power generation capacity of the fixed RPM generator included in the power generation unit 10 is calculated based on the maximum load power of the continuous load, variable load. Since most essential loads of LNG carriers are continuous loads, the load ratio of the essential loads is not large.

On the other hand, most of the service loads of LNG carriers, which perform operations related to LNG tank operation and LNG fuel supply, are irrelevant to the propulsion of the vessel, and correspond to variable loads in which the load rate changes over time.

For example, the LNG carrier may include a cargo part load as a service load. The load capacity of the entire cargo part in the LNG carrier to which the system of FIG. 1 is applied is approximately 5.5 MW, and has an abrupt load factor of about 30 to 100 in operation mode.

As a result, in the power supply system of FIG. 1 to which a fixed RPM generator is applied, service and essential loads are mixed in a single system, and there is a problem that power generation efficiency of the power supply system is deteriorated in a heavy or low load section.

Patent Publication No. 10-2017-0118285

According to another aspect of the present invention, the ship power load divided into essential load (Essential, Important Load) and service load (Service Load) is separated into the essential load power system and the service load power system (for example, 440V) to lower the voltage Distribution can provide LNG carriers with a power supply system for LNG carriers that can power the load.

In another embodiment according to the second aspect of the invention, an LNG carrier having a mandatory load and a service load comprises: a first power system associated with the mandatory load; And a second power system associated with the service load. Here, the thruster motor is associated with the second power system.

In one embodiment, the LNG carrier may further include: a switching unit configured to switch to transfer power generated in the first power system to the thruster motor of the second power system.

In one embodiment, the switching unit is configured to switch to transfer power generated in the first power system to the thruster motor of the second power system when the thruster motor starts to operate.

In one embodiment, the switching unit is configured to switch to transfer power generated in the first power system to the essential load when the thruster motor ends the operation.

In one embodiment, the switching unit may include a single pole double throw (SPDT).

In one embodiment, the first power system may be configured to perform low voltage distribution, and the second power system may be configured to perform high voltage distribution. The LNG carrier may further include a transformer that receives the low voltage electric signal from the switching unit and boosts the voltage to a high voltage electric signal.

 According to an aspect of the present invention, the LNG carrier has a low-voltage distribution-based power system is divided into an essential load power system, and a service load power system according to the load characteristics. Essential load The power system includes the essential loads associated with the operation of the LNG Carrier (eg thrust motors, propulsion motors, engine lubricating oil pump motors, etc.), and most of the essential loads are continuous loads. Service load power systems are not essential to the operation of LNG carriers, but include loads associated with providing services by LNG carriers (eg, Cargo Pumps, HD Compressors, LD Compressors, Vaporizers, etc.) Most of the service loads are variable loads.

This load separation reduces the capacity of each power grid compared to a single single grid, so that only low-voltage distribution can supply power to each load in the power grid. Therefore, high pressure distribution is not necessary, and a large capacity pressure reducing transformer for reducing the high pressure to low pressure is not required. By not using a pressure reducing transformer, cost savings can be achieved in terms of capital expenditures (CAPEX).

In addition, the space previously provided for the decompression transformer (ie the transformer compartment) can be used for a variety of other purposes. In general, the decompression transformer is located in an engine room with high equipment density, which greatly affects onboard space utilization.

In addition, by separating the essential load power system and the service load power system to increase the stability of each system. In the conventional case, if a system accident occurs at the service load end, the system is composed of a single system, which affects the required load. If the system is separated, the accident of the service load stage spreads only in the service load power system, and thus does not affect the essential load power system. Likewise, the accident does not spread to the service load stage even in the event of an essential load stage disconnection.

In addition, since the power systems are separated, each power system may have an independent system configuration. For example, the generator type, voltage for distribution or electrical signal type of each power system can be configured and operated independently.

In one embodiment, the system is configured to configure and operate a generator optimized for load characteristics so as to have a high power generation efficiency. For example, in a power system that mainly includes continuous loads, a fixed RPM generator more suitable for continuous load power supply is installed to operate at a fixed RPM so as to have a power generation capacity that shows optimum efficiency for continuous load power supply. The power system includes a variable RPM generator that is more suitable for variable load power supply, and operates at a variable RPM having optimum efficiency for variable load power supply.

As a result, the amount of fuel consumed in the LNG carrier can be reduced.

In another embodiment, the system can also supply power to a power system that mainly includes variable loads using a fixed RPM generator. Due to the use of the fixed RPM generator, the cost of the generator is reduced, it is possible to obtain the effect that the power converter required when applying a variable speed generator is not required.

Further, the power distribution system in each power system may be configured to enable low voltage DC distribution and / or low voltage AC distribution. That is, unlike the conventional power supply system in which DC distribution is difficult, the distribution type may be freely set, and thus flexible power supply may be possible according to characteristics of the power generation unit and the load.

In one embodiment, the system is configured to provide power to a thruster motor, located in the bow and operating only at entry / departure, in the service load power system. As a result, it is possible to reduce the generating capacity of the essential load power system.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

BRIEF DESCRIPTION OF DRAWINGS To describe the technical solutions in the embodiments of the present invention or in the prior art more clearly, the drawings required in the description of the embodiments are briefly introduced below. It is to be understood that the drawings below are for the purpose of describing the embodiments herein and are not intended to be limiting. In addition, some elements to which various modifications, such as exaggeration and omission, may be shown in the following drawings for clarity of explanation.
FIG. 1 is a diagram illustrating a system structure diagram of an LNG carrier power supply system configured as a single system by mixing essential loads and service loads according to an exemplary embodiment.
FIG. 2 is a diagram for explaining the internal structure of a conventional LNG carrier having the power supply system for the LNG carrier of FIG. 1.
3 is a schematic system structure diagram of a power supply system for an LNG carrier including a separate power system according to an embodiment of the present invention.
4 is a schematic system structure diagram of a power supply system for an LNG carrier configured to have a variable RPM generator according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a relationship between a load ratio of a load stage in a power system and a fuel consumption of a generator for powering the load stage.
Figure 6, according to one embodiment of the present invention, the mandatory load power system is configured to perform alternating current distribution with a fixed RPM generator, the service load power system has a variable RPM generator and LNG configured to perform partial DC distribution A schematic system structure diagram of a power supply system for a carrier ship is shown.
7 is a schematic system structural diagram of a power supply system of an LNG carrier including a separate power system according to other embodiments of the present invention.
8 is a schematic system structure diagram of a power supply system of an LNG carrier including a separate power system according to still another embodiment of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to embody the described features, regions, numbers, steps, actions, components, and / or components, and include one or more other features, regions, numbers, It is not intended to exclude the presence or addition of steps, actions, components, and / or components.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal sense unless clearly defined herein. .

In this specification, the division of the load system into the essential load system and the service load system means that the essential load and the service load are not mixed in the same system, but are included in different systems and configured to be powered by different main distribution boards. . Separation of the load grid is not permanent, and different load grids can be connected by any component that can be electrically connected between the power supply components (e.g., an SPDT switch, or a bus-tie breaker, etc.). have.

Embodiments herein relate to the power system of an LNG carrier. In the case of LNG carriers, the range of low pressure is specified in the international regulations, the DC low pressure of 1500V or less, and the AC low pressure of 1000V or less, so unless otherwise specified, the term "low pressure" is 1500V or less, DC In the case of refers to the voltage corresponding to less than 1000V.

The power supply system for an LNG carrier according to the embodiments of the present invention mainly consists of an essential load power system including an essential load, and a power system mainly comprising a service load power system including a service load. The essential load and the service load do not share the switchboard. The separation of the systems reduces the load capacity compared to a single power system, enabling low voltage distribution.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic system structure diagram of a power supply system for an LNG carrier including a separate power system according to an embodiment of the present invention.

Referring to FIG. 3, the power supply system 1 for an LNG carrier includes one or more power systems 100, 200, and the like. The power system 100 includes a power generation unit 110, a distribution panel 130 including a main distribution panel, and an essential load unit 150 including an essential load. The power system 200 includes a power generation unit 210, a distribution board 230 including a main distribution board, and a service load unit 250 including a service load.

In addition, the LNG carrier ship power supply system 1 may further include a control unit (not shown) for monitoring the state of the power system and control the power supply. The controller may include one or more of a power management system (PMS), an energy management system (EMS), and an energy power management system (EPMS).

Hereinafter, for clarity of explanation, the power supply system 1 for an LNG carrier is described as including two power systems 100 and 200, but is not to be construed as limited thereto. In addition, in some cases, a detailed description of the two components is represented by representing a detailed description of the one component.

As shown in FIG. 3, the power supply system 1 for an LNG carrier has a state in which a power system is separated for each of an essential load and a service load.

The power generation unit 110 supplies power to the essential load unit 150 through the switchboard 130 so that the load of the essential load unit 150 consumes and drives power.

The generator 110 outputs an alternating current electrical signal, and includes a plurality of generators (eg, generators 111 and 112 of Fig. 3. The power generation type and power generation capacity of the generators 111 and 112 depend on the load. For example, an alternator can be used when the motor load for the operation of an LNG carrier is a constant output load, and when the capacity of the generator is 85% and the load capacity is 1 MW, the generator capacity is about. May be 1.2 MW.

The capacity of one generator included in the power generation unit 110 has sufficient capacity to supply power to the essential load unit 150 in the general navigation mode. In this case, at least one of the plurality of generators 111 and 112 is designated as a standby generator, and the standby generator is set not to operate during normal sailing.

In one embodiment, in the event of an accident of a generator (eg, 111) operating in the required load power system 100, the power supply system 1 may be a standby generator (eg, included in the required load power system 100). , 112 is configured to supply power to the required load 150.

In one embodiment, the standby generator of the mandatory power system 100 may operate to supply power to the service load of the service load power system 200. This will be described in more detail with reference to FIGS. 7 and 8 below.

The generators 111 and 112 may include, but are not limited to, a diesel generator, a combined fuel generator, a gas fuel generator, a gas turbine, and the like. In addition, the power generation unit 110 may further include one or more switches, and / or disconnectors for power supply control according to a situation. For example, as shown in FIG. 3, when the LNG carrier power supply system 1 includes two generators 111 and 112, the switch may further include two switches.

In the switchboard 130, power is supplied to AC. In one embodiment, the switchboard 130 may include a main switchboard of the power system 100. The main switchboard is composed of a bus cable, in which case the bus cable may be referred to as a main bus.

Also, in some embodiments, switchboard 130 may include a plurality of bus cables. For example, the switchboard 130 may include a plurality of bus cables, such as a main bus 131 electrically connected to the generator 111 and a main bus 132 electrically connected to the generator 112. In this case, the switchboard 130 is electrically connected to the plurality of main buses 131 and 132 as usual, but further includes a bus tie breaker 133 that is electrically disconnected in case of emergency and / or accident. can do.

Low voltage can be applied to the switchboard 130, the power system 100 is capable of low voltage distribution. For example, a low voltage of 440V may be applied to the main bus 131 and the main bus 132 of FIG. 3 to supply power to the load.

Components of the power system 100 may be electrically connected to interact. For example, the LNG carrier power supply system 1 may supply power to the essential load by using a power supply line that electrically connects the power generation unit 110 to the essential load unit 150 through the switchboard 130. have.

The mandatory load part 150 of the power system 100 includes an essential load (Essential, Important Load) which is essentially required for operation of the ship. The essential load (Essential, Important Load) is essentially required for the essential load and the ship operation defined by the ship regulations, but semi-mandatory load that is not included in the essential load in ship regulations secondary essential load (e.g., important load).

Essential loads used for the operation of LNG carriers may include, but are not limited to, for example, propulsion motors, ballast pumps, lubricant pumps, engine fueling pumps, cooling pumps, water spray pumps, and the like. It doesn't work. Most of the essential loads included in the essential load unit 150 correspond to continuous loads in which the load rate hardly changes.

In some embodiments, the mandatory load unit 150 may further include a variable frequency drive (VFD) based load. A variable frequency control-based load is an essential load that optimizes the power consumption of the load stage according to the operating characteristics, such as a central cooling system.For example, a VFD load is a cooling pump configured to control the temperature of the cooling water. Essential loads configured to control temperature, pressure, and the like.

As described above, the switchboard 130 is configured to perform low voltage distribution. Thus, as shown in FIG. 3, at least some required loads can be electrically connected and powered without the need for a separate transformer.

In addition, the essential load unit 150 may include one or more lower switchboards that supply power to a voltage equal to or lower than that of the switchboard 130. In this case, the essential load unit 150 may further include a transformer 155 disposed between the switchboard 130 and the lower switchboard to reduce the voltage. For example, as shown in FIG. 2, the mandatory load 150 includes a transformer 155A, 155B, 155C, between the switchboard 130 (eg, 450V applied) and the lower switchboard (eg, 220V applied). 155D).

The transformer 155 is a transformer for reducing the low pressure to a lower voltage (for example, 220V), and compared to the pressure reducing transformers 31, 32, 33, and 34 of FIG. Have

In addition, the power system 100 may further include an emergency generator for supplying power in an emergency situation such as black out, and an emergency switchboard including a load operating at this time. The emergency switchboard may include shore power, emergency load, and the like.

Since components and operations of the power system 200 are substantially similar to those of the power system 100, the following description will focus on differences.

On the other hand, the service load unit 250 of the power system 200 includes a service load additionally used in addition to the operation of the LNG carrier. In addition, the variable load unit 250 may further include one or more lower switchboards (not shown) for supplying power at a lower voltage than the switchboard 230.

The service load unit 250 includes an LNG storage load used to store LNG, a user convenience load generated from LNG and used for the convenience of a passenger of an LNG carrier.

LNG is a flammable material, and LNG carriers must control the temperature and pressure of cargo tanks or pipelines to easily load or unload LNG. In addition, in order to safely transport LNG by sea, it is necessary to continuously control the temperature and pressure of the cargo tank during normal sailing.

Thus, the load for LNG storage, including loads that operate to load, unload, and store LNG on LNG carriers, and loads that operate for management of LNG stored during operation (eg, LNG cooling, compression, etc.), corresponds to variable loads. do.

In addition, the service load unit 250 may include a load for LNG fuel for using the BOG (Boil-Off Gas) as a fuel.

Due to environmental regulations, LNG carriers are equipped with a dual fuel engine system. The dual fuel engine system may control at least a part of the load for the LNG fuel in Gas Mode or HFO Mode. Here, the gas mode is a mode in which the naturally occurring BOG in the cargo tank and the forced vaporized BOG is used as a fuel for the LNG carrier, and the HFO mode is a high fuel oil (HFO) such as high sulfur fuel oil and bunker oil. This mode is used as fuel for carrier ships.

Therefore, the load for LNG fuel for using such BOG as fuel also corresponds to a variable load. For this reason, most of the service loads correspond to variable loads with a variable load rate.

The LNG storage load may include, but is not limited to, for example, a high duty compressor, a cargo pump, a cargo auxiliary machine, and the like.

The load for LNG fuel includes, but is not limited to, for example, a LD compressor, a vaporizer, and the like.

In addition, the variable load unit 250 may further include one or more lower switchboards (not shown) for supplying power at a lower voltage than the switchboard 230.

In some embodiments, as shown in FIG. 3, at least some of the power load of the essential load 150 or the service load 250 may control a component (eg, a starter panel) that controls the amount of power received during operation of the load. Starter Panel, S / T).

In addition, since each of the separated power systems 100 and 200 of the LNG carrier power supply system 1 has an independent system configuration, the stability of each system is also increased. In the conventional case, if a system accident occurs at the service load end, the system is composed of a single system, which affects the required load. If the system is separated, the accident of the service load stage spreads only in the service load power system, and thus does not affect the essential load power system. Likewise, the accident does not spread to the service load stage even in the event of an essential load stage disconnection.

In addition, the size of individual power systems is reduced compared to a single power system. For example, when a single power system having a power capacity of 14 MW is separated into a mandatory load power system 100 at 9 MW and a service load power system 200 at 5 MW as shown in FIG. 3, the size of the individual power system is 14 MW. To 9MW and 14MW to 5MW respectively.

And, instead of the high voltage of 6.6kV or more, a low voltage (eg, 440V) is applied to the power supply through the main switchboard. This no longer requires the large capacity pressure reducing transformers 31, 32, 33, 34 of FIG. 1. Thus, cost savings in terms of capital expenditures (CAPEX) can be achieved.

Moreover, large capacity pressure reducing transformers 31, 32, 33, 34 are not required, so that the space occupied by the existing pressure reducing transformers 31, 32, 33, 34 of the transformer chamber 1007 shown in FIG. It can be used efficiently. For example, if the power supply system 1 of FIG. 3 is applied to an LNG carrier, the space in the transformer compartment 1007 may be utilized for other purposes (eg, cargo ships, etc.) instead of for the placement of multiple pressure reducing transformers. Can be.

Furthermore, the power system 100, 200 may be configured in various ways or differently depending on the design purpose due to the separation of the system.

In one embodiment, each power system 100, 200 is configured to configure and operate a generator that is primarily optimized for the load characteristics involved. For example, the required load power system 100 may include a fixed RPM generator, and the service load power system 200 may include a variable RPM generator.

4 is a schematic system structure diagram of a power supply system for an LNG carrier configured to have a variable RPM generator according to an embodiment of the present invention.

Since the power supply system 1 of FIG. 4 is similar to the power supply system 1 of FIG. 3, the description will be mainly given of differences.

4, the generators 111 and 112 of the mandatory load power system are fixed RPM generators, and the generators 211 and 212 of the service load power system 200 are variable RPM generators. In the case of continuous load, there is no load variation due to the constant output characteristics, so that there is almost no change in the load ratio, while the variable load is characterized by a change in the load ratio.

Since most of the load of the essential load power system 100 corresponds to a continuous load in which the load rate does not change, the fixed RPM generator is operated to operate in an optimum efficiency range (ie, a load rate range of 75 to 85%).

In the conventional single grid-based power supply system shown in FIG. 1, the power load of the LNG carrier is mixed in a single grid, resulting in a load section having a low load ratio of the entire system due to the variable load. As a result, the power generation efficiency of the fixed RPM power generation is lowered.

On the other hand, in the power supply system 1 of FIG. 4, since most variable loads of the LNG carrier are separated from the power system 100, a change in the load rate due to the variable load of the service load power system 200 is required. Does not affect the required load of

Therefore, even if a fixed RPM generator is applied to the essential load power system 100, it has a high power generation efficiency in the heavy load or low load section.

On the other hand, as described above, most of the load of the service load power system 200 is a variable load in which the load rate changes.

Accordingly, the service load power system 200 of the power supply system 1 of FIG. 3 is configured to drive a variable RPM generator capable of variable speed operation in accordance with a load rate variation of the power system 200.

In the service load power system 200 including such a variable RPM generator, when controlling the rotational speed of the variable RPM generator with RPM having an optimal power generation efficiency for each load section, when the continuous load, variable load is mixed in a single system In comparison, the fuel efficiency of the generator for supplying power to the variable load can be improved.

FIG. 5 is a diagram illustrating a relationship between a load ratio of a load stage in a power system and a fuel consumption of a generator for powering the load stage.

As described above, in the conventional single power system, a fixed RPM generator was used to supply a variable load (eg, an LNG storage load). The service load of the whole cargo part has an average load rate of 30 to 100%.

As such, when electric power is supplied to the entire service load of the LNG carrier which is changed to a heavy load or a low load using a fixed RPM generator as in the related art, it has a low power generation efficiency in a heavy load or a low load section having a low load ratio.

On the other hand, when power is supplied to a service load in which the load rate is changed by using a variable RPM generator as in an embodiment of the present invention, power generation efficiency is improved in a low load section having a low load rate compared to the power supply system of FIG. 1. .

Referring to FIG. 5, the power supply system of FIG. 1 has a fuel efficiency corresponding to P _F at a load rate of 45% as an example of a low load period. On the other hand, the power supply system 1 of FIG. 4 has a fuel efficiency corresponding to P _V. When comparing P _F and P _V , it is shown that the power supply system 1 of FIG. 4 consumes less fuel amount to generate 1 kwh of power. As a result, the power supply system 1 of FIG. 4 is calculated to have an improvement in fuel consumption of approximately 8% compared to the power supply system of FIG. 1 in generating the same power for service load of the LNG carrier.

The above 8% is merely an example, when the service load is configured to have a load section in which the load ratio fluctuates with time, the power generation efficiency is further increased by controlling the generator rotational speed with an RPM having an optimal generation efficiency corresponding to the load section. It can be improved.

In the LNG carrier load, the low load section L1 is a section with a load rate of 10 to 40% and has a fuel consumption of approximately 285 to 210 g / kwh. The heavy load section L2 is a section with a load ratio of 40 to 60% and has a fuel consumption of approximately 210 to 194 g / kwh. The high load section L3 is a section with a load ratio of 80 to 100% and has a fuel consumption of approximately 185 to 190 g / kwh. The power supply system 1 of FIG. 3 has a fuel consumption similar to that of the power supply system of FIG. 1 in the high load section L3. However, in the low load section L1, the fuel consumption rate per kwh is improved by about 6 to 10%, and in the heavy load section L2, the fuel consumption per kwh is improved by about 10 to 35%.

As such, the variable RPM generator of the service power system 200 of FIG. 4 may control the RPM based on the load ratio of each load section, thereby improving power generation efficiency of the power generation unit 210.

Meanwhile, when the service load power system 200 performs AC distribution, the switchboard 230 may be configured to have a specific frequency (eg, 50 Hz or 60 Hz). In this case, the power generation unit 210 generates AC power based on the load ratio of each load section, and alternating current (AC) electric signal having a frequency (eg, 50 Hz or 60 Hz) matching the frequency of the switchboard 230. It is configured to output.

In one embodiment, the power generation unit 210 includes an alternating current (AC) / AC (AC) converter 214 located between the generator 211 and the switchboard 230. The AC / AC converter 214 is configured to convert the frequency of the alternating current (AC) electrical signal generated in the variable RPM generator to a specific frequency (eg, 50 Hz or 60 Hz) of the switchboard 230.

As a result, even if there is a change in RPM of the variable RPM generator 211 based on the load ratio of each load section, the power generation unit 210 may output an alternating current (AC) electric signal having a specific frequency of the switchboard 230.

In addition, since the power supply system 1 for LNG carriers is capable of low voltage distribution, the low voltage direct current (DC) distribution and / or low voltage alternating current (AC) distribution of the power distribution system in each of the power systems 100 and 200 is possible. Can be configured to

6, the mandatory load power system is configured to perform alternating current distribution with a fixed RPM generator, and the service load power system is configured to perform DC distribution partially with a variable RPM generator, according to one embodiment of the invention. A schematic system structure diagram of a power supply system for a carrier ship is shown.

Since the power supply system 1 of FIG. 6 is similar to the power supply system 1 of FIG. 4, the following description will focus on differences.

Referring to FIG. 6, the service load power system 200 is further configured to partially allow DC distribution. In the power supply system 1, the generators 111 and 112 are fixed RPM generators, and the generators 211 and 212 are variable RPM generators.

In one embodiment, the power generation unit 210 further includes an AC (AC) / DC (DC) inverter 216 for receiving an AC (AC) electrical signal and converts it into a DC (DC) electrical signal, the second The load unit may further include a direct current (DC) / AC (AC) inverter 226 for receiving a direct current (DC) electric signal and converting the signal into an alternating current (AC) electric signal.

When DC distribution is performed as described above, power loss due to frequency and phase synchronization and reactive power can be prevented.

In addition, as shown in FIG. 6, the power system 200 further includes a direct current (DC) switchboard 220 including a direct current (DC) main bus 221 between the power generation unit 210 and the switch panel 230. can do. The DC switchboard 220 may efficiently supply power to a plurality of service loads disposed in a carrier. In this case, the power system 200 may include a plurality of direct current (DC) / AC (AC) inverters 226A to 226B for electrically connecting the service load of each of the switchboard 220 and the switchboard 230.

By the alternating current (AC) / direct current (DC) inverter 216 and the direct current (DC) / alternating current (AC) inverter 226, in the power system 200 in the portion between the power generation unit 210 and the switchboard 230 DC distribution is possible .

As such, the power supply system 1, the mandatory load power system may be composed of a fixed RPM generator-based AC distribution, the service load power system may be of a variable RPM generator-based DC or AC distribution.

In addition, the power supply system 1 may configure different voltages for power distribution of the respective power systems 100 and 200.

In one embodiment, the power supply system 1 performs low-voltage distribution through the switchboard 130 in the essential load power system 100, and performs high-voltage distribution through the switchboard 230 in the service load power system 200. It is configured to. Here, the low pressure distribution of the essential load power system 100 may be performed using a fixed RPM generator, and the high pressure distribution of the service load power system 200 may be performed using a variable RPM generator. In this case, the power generation unit 210 of the service load power system 200 is configured to output a high voltage (eg, 6.6 kV) electrical signal to the switchboard 230.

In addition, power systems 100 and 200 may be configured to be efficient in terms of component supply.

In one embodiment, the service load power system 200 performs low-voltage distribution through the switchboard 230, the low-pressure distribution may be performed using a fixed RPM generator. Referring back to FIG. 3, the service load power system 200 includes a power generation unit 210, a low voltage switchgear 230, and a service load unit 250.

In the switchboard 230, low pressure distribution according to system separation is performed. When the switchboard 230 distributes AC power, the frequency of the switchboard 230 is a specific frequency (for example, 50 Hz or 60 Hz).

The power generation unit 210 is configured to generate power having a frequency (eg, 50 Hz or 60 Hz) matching the frequency of the switchboard 230. For example, the power generation unit 210 may include a fixed RPM generator for driving at a fixed RPM for a frequency matching the frequency of the switchboard 230. In the case of large-capacity generators, fixed RPM generators have the advantages of being cheaper and easier to supply than variable RPM generators.

In some embodiments, the power generation unit 210 may include a plurality of fixed RPM generators 211 and 212. The power generation capacity of the fixed RPM generators 211 and 212 may be greater than or equal to the power capacity of the service load 250. The fixed RPM generator 211 or 212 has a power generation capacity sufficient to supply power to the service load power system 200 in a heavy load or low load section.

Due to the frequency matching structure between the power generation unit 210 and the switchboard 230, the service load power system 200 does not require additional power devices (eg, power converters) for frequency matching between the low voltage switchgear and the power generation unit. In the distribution board 230, low-voltage alternating current (AC) distribution may be performed.

For example, the generator 211 or 212 of the service load power system 200 is a variable RPM generator, and may generate power having a frequency in a variable frequency range (for example, 37 Hz to 60 Hz) according to the speed. In this case, between the switchboard 230 having a specific frequency (for example, 50Hz or 60Hz) and the variable RPM generator 211, the frequency of the power output from the power generation unit 210 for frequency matching is the frequency of the switchboard 230. A power converter (eg, a matrix converter) is required to convert the power supply into an electric power source, and it is not easy to supply a large capacity converter that converts a power generation capacity (eg, 3MW) of a generator used in a ship. Moreover, the price of a variable RPM generator is typically higher than the price of a fixed RPM generator.

As a result, the service load power system 200 including the fixed RPM generator maintains the advantages of low-voltage distribution and at the same time does not require an additional power device (eg, a power converter) for frequency matching with the low-voltage switchgear, which is required when applying a variable speed generator. In addition, lower cost distribution-based power supply systems can be built on board ships at lower cost. Furthermore, a part of the service load power system 200 can be configured based on a fixed RPM generation standard that can be supplied in the existing, and there is ease of design.

On the other hand, the service load power system 200 including the fixed RPM generator is applied to a low voltage is applied to the switchboard 230 is not limited to the low-voltage alternating current (AC) distribution structure, the AC (AC) distribution. In another embodiment, the service load power system 200 including the fixed RPM generator, similar to Figure 6, may be configured in a low voltage direct current (DC) distribution structure. In another embodiment, the service load power system 200 including the fixed RPM generator may be configured as a high-voltage alternating current (AC) distribution structure.

In addition, the marine power supply system 1 may be configured such that the thruster motor 152 and the essential load power system 100 are not connected.

7 is a schematic system structural diagram of a power supply system of an LNG carrier including a separate power system according to other embodiments of the present invention.

Since the power supply system 1 of FIG. 7 is similar to the configuration of the power supply system 1 of FIG. 3, the differences will be mainly described.

In FIG. 3, the power generation capacity of the mandatory load power system 100 associated with the thruster motor 152 is a continuous, defined as the mandatory load in the thruster motor 152, and the ship rule (Rule). The power supply is set based on all of the power capacities of the continuous loads required to be supplied. The thruster motor 152 is operated only for a short time at the time of entry / departure, but is included in the essential load power system 100 in the power supply system 1 of FIG.

On the other hand, when the thruster motor 152 is linked to the essential load power system 100 including most of the continuous load, most ships in which the thruster motor 152 does not operate in the essential load power system 100 are operated. There is a significant difference between the power capacity and generation capacity consumed at the load over time. That is, since the generator of the over-spec than the power generation capacity required in the substantially required load power system 100 is to be installed, a generator cost that is higher than the required generator cost is required.

In one embodiment, the thruster motor 152 is linked to the service load power system 200, which is a power system other than the required load power system 100, so as to set down the generation capacity of the required load power system 100. The power capacity of the stur motor 152 is configured not to be considered. Further, although the service load power system 200 is associated with a large load (that is, the thruster motor 152) by cross-using power for a short time when the thruster motor 152 is operated, the additional generation capacity It is configured so that there is no increase. In this case, the LNG carrier ship power supply system 1 is further configured to control the power supply according to the operation of the thruster motor 152.

Referring to FIG. 7, the thruster motor 152 receives the power of the generator 210 through the switchboard 230. In one embodiment, the power generation unit 210 includes a variable RPM generator. In another embodiment, the power generation unit 210 includes a fixed RPM generator.

The thruster motor 152 is an important important load (Important Load) in ship operation in terms of functionality, but corresponds to a semi-essential load (Secondary Essential Load) that does not require continuous power supply during ship operation. Therefore, a configuration that is not linked to the required load power system 100 that continuously supplies power to the required load is possible. For example, as shown in FIG. 7, thruster motors 152A, 152B are associated with switchboard 230 of service load power system 200.

As such, since the essential load power system 100 and the thruster motor 152 are not connected, the essential load power system 100 may increase the load rate during normal sailing. As a result, fuel efficiency can be further increased and operating costs can be reduced. In addition, since the power generation capacity of the essential load power system 100 is reduced compared to the case where the thrust motor 152 is connected (for example, FIG. 3), a more compact generator can be applied to the essential load power system 100. Thereby, the generator cost can be reduced.

In addition, the service load power system 200 includes a switching unit 125 so that there is no addition of the generating capacity of the generator 210 according to the additional linkage of the thruster motor 152. By the switching unit 125, even when the thruster motor 152 connected to the service load power system 200 is operated, power supply to other service loads is not insufficient.

In one embodiment, the switching unit 125 allows the power of the power generation unit 110 to supply the thruster motor 152 through the switchboard 230. As illustrated in FIG. 7, the switching unit 125 may include a single pole double throw (SPDT). The SPDT is a first path from the power generation unit 110 (eg, the generator 112) to the switchboard 130, or the service load power system 200 from the power generation unit 110 (eg, the generator 112). It is configured to connect a second path to the switchboard 230 of the).

The power supply by the switching unit 125 may be described as follows: For the departure of the LNG carrier, the switching unit 125 is switched by the control unit to connect the second path, and the Power is supplied to the thruster motor 152 through the switchboard 230. After the departure, the switching unit 125 is switched by the controller to connect the first path, and the thruster motor 152 does not operate during normal sailing. In order to re-enter the LNG carrier, the switching unit 152 is switched by the controller to connect the second path, and the power of the power generation unit 110 is supplied to the thruster motor 152 through the switchboard 230. .

Due to this switching structure, even if the thruster motor 152 is further connected to the service load power system 200, the power generation capacity of the service load power system 200 is not further increased.

Meanwhile, the power systems 100 and 200 of FIG. 7 are not limited to low voltage alternating current (AC) distribution. As described above, a fixed RPM generator or a variable RPM generator may be applied according to the characteristics of the power system 200. In addition, it may be configured as a low pressure alternating current (AC) distribution, a high pressure alternating current (AC) distribution, or a low pressure direct current (DC) structure.

In one embodiment, the power grids 100, 200 of FIG. 7 are configured to perform high voltage alternating current (AC) distribution. In this case, the power generation units 110 and 210 are configured to output a high voltage electric signal (eg, 6.6 KV).

8 is a schematic system structure diagram of a power supply system of an LNG carrier including a separate power system according to still another embodiment of the present invention.

Since the power supply system 1 of FIG. 8 is similar to the power supply system 1 of FIG. 7, the differences will be mainly described.

Referring to FIG. 8, the essential load power system 100 performs low voltage distribution through the distribution panel 130, and the service load power system 200 is configured to perform high voltage distribution through the distribution panel 230. In this case, the power generation unit 110 is configured to output a low voltage electric signal (eg, 440V), and the power generation unit 21 is configured to output a high voltage electric signal (eg, 6.6 kV).

In this embodiment, the power output from the power generation unit 110 is provided to the thruster motor 152 through the cross-power transformer 126. The cross power transformer 126 boosts a low voltage electric signal output from the power generation unit 110 and provides the thruster motor 152 through the switchboard 230 to which the high pressure is applied. The input voltage of the cross power transformer 126 depends on the output voltage of the power generation unit 110, and the output voltage of the transformer 126 depends on the applied voltage of the switchboard 230.

As described with reference to FIG. 7 and FIG. 8, the LNG carrier power supply system 1 links the thruster motor 152 to a power system other than the essential load power system 100, while in the service load power system. Apply various generators (e.g., fixed RPM or variable RPM generators) to suit the characteristics of the load stage, or use a variety of distribution structures (e.g., low voltage direct current (DC) distribution, low pressure alternating current (AC) distribution or high pressure alternating current (AC) distribution) Can be configured.

In the present specification, the structure of the power supply system 1 shown around FIG. 3 may be different depending on the LNG carrier environment such as the load capacity included in the LNG carrier. For example, three generators may be included in the power system 100. In addition, the generating capacity of the three generators may be the same or not all the same.

In addition, 440V applied to the switchboard 130 of FIG. 3 is merely an exemplary voltage indicating a lower voltage than the 6.6kV of FIG. 1, and the switchboards 130 and 230 may supply power at different voltages in some cases. For example, 450V may be applied to the switchboard 130 depending on the rated voltage of the different loads, or 690V may be applied to the switchboard 230 by an alternating current (AC) / direct current (DC) inverter.

In addition, the power supply system 1 may control the operation of the generator according to the time zone (or the operation mode) and adjust the amount of power supplied to the load unit. For example, when the essential load 150 of the power system 100 does not require the power generation capacity of the two generators 111 and 112, the power supply system 1 for the LNG carriers includes at least one generator ( For example, the generator 111 may be set as a standby generator to stop operation, and when necessary, the generator 111 may be used to supply power to the essential load unit 150 and other purposes using the standby generator.

Although the present invention described above has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1: LNG Carrier Power Supply System 200: Service Load Power System
100: required load power system 210: service load generation unit
110: required load generation unit 211, 212: generator
111, 112: generator 213: switch
125: switching unit 216: AC / DC converter
130: switchboard 230: switchboard
131, 132: main bus 231, 232: main bus
133: bus link breaker 233: bus link breaker
150: mandatory load 250: service load
152: thruster motor
155: transformer

Claims (6)

In LNG carrier having essential load and service load,
A first power system associated with the required load; And
A second power system associated with the service load,
A thruster motor is LNG carrier, characterized in that associated with the second power system.
The method of claim 1,
And a switching unit configured to switch to transfer power generated in the first power system to the thruster motor of the second power system.
The method of claim 2, wherein the switching unit,
When the thruster motor starts to operate the LNG carrier, characterized in that for switching to transfer the power generated in the first power system to the thruster motor of the second power system.
The method of claim 2, wherein the switching unit,
When the thruster motor is terminated operation LNG carrier, characterized in that for switching to transfer the power generated in the first power system to the essential load.
The method of claim 2, wherein the switching unit,
LNG carrier comprising a single pole double throw (SPDT).
The method of claim 2,
The first power system is configured to perform low voltage distribution, the second power system is configured to perform high voltage distribution,
And a transformer for receiving the low voltage electric signal from the switching unit and boosting the voltage with a high voltage electric signal.

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