Ship propulsion system

Abstract

The present invention relates to a ship propulsion system, wherein a control unit controls driving of an auxiliary propulsion device on the basis of a comparison between fuel consumption of a power generation source to be increased by driving of the auxiliary propulsion device and fuel consumption of a main engine to be reduced by propulsion power assisted by the auxiliary propulsion device, so that the main engine is operated within an optimal efficiency output range, unnecessary fuel consumption is prevented, and fuel consumption efficiency of the entire propulsion system is improved.

Description

ship propulsion system

[0001] The present invention relates to a ship propulsion system.

[0002] In addition to the main engine for propulsion, ships require a separate power generation system to supply the power required for various equipment and systems. Accordingly, shaft generator systems, which are coupled to the main engine's propulsion shaft and utilize rotational force to generate electricity, are widely used. Shaft generators can continuously produce power through the rotation of the main engine during operation, providing power to system loads without the need for a separate diesel generator. This reduces fuel consumption and greenhouse gas emissions, contributing to environmentally friendly operation.

[0003] Meanwhile, the main engine exhibits different specific fuel consumption (SFC) depending on its output status. Typically, the optimal efficiency output, which achieves the highest fuel consumption efficiency, is achieved within a given output range. If the main engine operates outside this optimal efficiency output range, more fuel is consumed to secure the same propulsion power, resulting in a decrease in the energy efficiency of the entire system. Therefore, it is necessary to control the main engine to operate at the optimal efficiency output, thereby reducing fuel consumption and ultimately increasing the energy efficiency of the entire ship propulsion system.

[0004] The purpose of the present invention is to provide a ship propulsion system with improved efficiency in the ship's power system. The objectives of the present invention are not limited to those mentioned above, and other unmentioned objectives will be clearly understood by those of ordinary skill in the art from the description below.

[0005] A ship propulsion system according to one aspect of the present invention comprises: a main engine connected to a propulsion unit through a propulsion shaft and generating propulsion power of the ship by consuming fuel; a shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; an auxiliary propulsion device consuming electric power to assist the propulsion power of the ship; and a control unit controlling the operation of the auxiliary propulsion device based on a comparison of the fuel consumption of a power generation source to be increased by operation of the auxiliary propulsion device and the fuel consumption of the main engine to be reduced by propulsion power assisted by the auxiliary propulsion device.

[0006] The control unit can control the auxiliary propulsion device to be driven when it is determined as a result of the comparison that the fuel consumption of the main engine to be reduced is greater than the fuel consumption of the power generation source to be increased.

[0007] The auxiliary propulsion device is driven by consuming at least a portion of the power generated by the shaft generator, and the control unit can control the auxiliary propulsion device to be driven when it is determined that the fuel consumption of the main engine to be reduced by the propulsion power assisted by the auxiliary propulsion device is greater than the fuel consumption of the main engine to be increased by driving the shaft generator to drive the auxiliary propulsion device.

[0008] The above control unit can control the output of the main engine based on the speed of the ship with the auxiliary propulsion device driven and the target speed of the ship.

[0009] The above control unit can control the output of the main engine to be reduced when the speed of the ship exceeds the target speed of the ship while the auxiliary propulsion device is being driven.

[0010] The above control unit can control the output of the main engine to increase when the speed of the ship falls below the target speed of the ship while the auxiliary propulsion device is being driven.

[0011] The control unit can control to change at least one of the driving state of the auxiliary propulsion unit and the power source supplying power to the auxiliary propulsion unit when it is determined that the shaft generator cannot supply power to drive the auxiliary propulsion unit.

[0012] The auxiliary propulsion device is provided in multiple units, and the control unit can control to stop at least some of the multiple auxiliary propulsion devices or reduce the output of each auxiliary propulsion device when it is determined that the capacity of power that can be withdrawn from the main engine is limited and the shaft generator generates power less than the rated capacity.

[0013] The control unit, when it is determined that the shaft generator cannot supply power to drive the auxiliary propulsion device, calculates and compares, for each combination of auxiliary propulsion devices operable with the power generated by the shaft generator, the fuel consumption of the main engine to be increased to drive the auxiliary propulsion device of each combination and the fuel consumption of the main engine to be reduced by the propulsion power assisted by the auxiliary propulsion device of each combination, and, as a result of the comparison, controls to drive the auxiliary propulsion device of the most efficient combination among combinations in which the fuel decrease is greater than the fuel increase.

[0014] Further comprising a power generation unit that generates electricity by consuming fuel, wherein the control unit can change the power generation source of the auxiliary propulsion unit based on a comparison of the fuel consumption of the power generation unit that is to be increased for driving the auxiliary propulsion unit and the fuel consumption of the main engine that is to be reduced by the propulsion power assisted by the auxiliary propulsion unit, when it is determined that the fuel consumption of the main engine that is to be increased for driving the auxiliary propulsion unit is greater than the fuel consumption of the main engine that is to be reduced by the propulsion power assisted by the auxiliary propulsion unit.

[0015] The control unit may change the power source so that the auxiliary propulsion device is driven by the power generated by the power generation unit when it is determined that the fuel consumption of the main engine, which will be reduced by the propulsion power assisted by the auxiliary propulsion device, is greater than the fuel consumption of the power generation unit, which will be increased to drive the auxiliary propulsion device.

[0016] The auxiliary propulsion device may include at least one of a wind-assisted propulsion system (WAPS) that assists propulsion of the ship using wind power and an air lubrication system (ALS).

[0017] The above control unit can estimate the fuel consumption of the power generation source to be increased by driving the auxiliary propulsion device using a lookup table including fuel consumption characteristics according to the load rate of the main engine.

[0018] A ship propulsion system according to another aspect of the present invention comprises: a main engine connected to a propulsion unit through a propulsion shaft and consuming fuel to generate propulsion power for the ship; a generator for generating electric power; an auxiliary propulsion unit for consuming electric power to assist the propulsion power of the ship; and a control unit for controlling the operation of the auxiliary propulsion unit and the generator based on the influence of the operation of the auxiliary propulsion unit on the overall propulsion efficiency of the ship.

[0019] The present invention has the effect of improving the efficiency of ship power systems. The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those of ordinary skill in the art from the description of the claims.

[0020] Figure 1 is a schematic diagram of a ship propulsion system according to a first embodiment of the present invention.

[0021] Figure 2 is a drawing for explaining the optimal efficiency output operation of the main engine.

[0022] Figure 3 is a graph showing the output of the main engine according to the operation of the auxiliary propulsion device and the shaft generator according to the present embodiment.

[0023] Figure 4 is a graph showing changes in fuel consumption according to changes in the load of the main engine.

[0024] Figure 5 is a schematic diagram of a ship propulsion system according to a third embodiment of the present invention.

[0025] Figure 6 is a graph showing fuel consumption for unit output production according to the driving load of the main engine of the present invention.

[0026] Figure 7 is a schematic diagram of a ship propulsion system according to a fifth embodiment of the present invention.

[0027] Figure 8 is a schematic diagram of a ship propulsion system according to the sixth embodiment of the present invention.

[0028] The purpose, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments, taken in conjunction with the accompanying drawings. In this specification, when reference numerals are given to components in each drawing, it should be noted that, where possible, identical components are given the same reference numerals even if they appear in different drawings. Furthermore, in describing the present invention, if a detailed description of a related known technology is deemed to unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0029] In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0030] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0031] The present invention encompasses a vessel equipped with the ship propulsion system described below. The term "vessel" encompasses gas carriers, merchant ships transporting various cargoes or people, and offshore plants such as FLNG and FSRU.

[0032] In an embodiment of the present specification, the control unit includes an upper controller that performs a function of comprehensively monitoring and controlling the operating status of the entire propulsion and power system, including a plurality of generators, propulsion units, auxiliary devices, and power conversion devices installed on the ship. The control unit comprehensively considers the ship's operating conditions, power demand, fuel status, load characteristics, external environmental information, etc. to generate control commands for each component, and accordingly can perform generator output control, power application / recovery of a shaft generator, charge / discharge control of a fuel cell or battery, operation control of an auxiliary propulsion device, etc.

[0033] Furthermore, the control unit may be comprised of a single device, or it may be distributed and controlled in conjunction with multiple control systems, such as a main controller, a power management system (PMS), a propulsion control unit, an energy management system (EMS), and a supervisory controller installed on the ship. In this case, the supervisory controller can monitor the status of each subordinate controller, adjust control priorities, and perform integrated control to ensure operational efficiency, energy savings, and stability of the entire ship system.

[0034] Therefore, the control unit mentioned in the present invention does not simply mean a local controller that controls only a specific device, but is a concept that includes a hardware and software system that comprehensively controls the propulsion system and power system of the entire ship, and can comprehensively perform real-time analysis of the ship's operating status, power distribution determination, energy flow optimization, etc.

[0035]

[0036] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0037]

[0038] FIG. 1 is a schematic diagram of a ship propulsion system according to a first embodiment of the present invention. For reference, FIG. 1 is a conceptual diagram illustrating at least a portion of the components included in one embodiment. Referring to FIG. 1, the ship propulsion system according to the first embodiment of the present invention includes a main engine (10), a shaft generator (20), a first converter (30), a second converter (40), an auxiliary propulsion device (50), a power generation unit (60), and a control unit (not shown).

[0039] The main engine (10) is connected to a propulsion device installed at the stern of the ship via a propulsion shaft, and the rotational force generated by the main engine (10) is transmitted to the propulsion device via the propulsion shaft to propel the ship. At this time, the propulsion device may be a propeller, and the propeller can rotate through the rotational force from the main engine (10) to form a fluid flow and move the ship forward.

[0040] The main engine (10) is an internal combustion engine that generates power by burning oil fuel (HFO, MDO, etc.) and / or gas fuel (LNG, LPG, etc.), and in the present embodiment, may be a two-stroke propulsion engine such as a ME-GI engine (MAN Electronic-Gas Injection Engine).

[0041] The output of the main engine (10) may vary due to at least one of changes in the system load of the ship, changes due to sea conditions, and changes occurring in the main engine itself, and such changes in the output of the main engine (10) may be reflected in the torque applied to the propulsion shaft.

[0042] The shaft generator (20) generates electric power by extracting at least a portion of the power generated by the main engine (10). The shaft generator is a type of power take-off device (PTO) in that it extracts and uses a portion of the power supplied to the propulsion unit from the main engine (10). This method of generating power using the shaft generator is effective in saving energy through economical power generation during ship operation.

[0043] The shaft generator (20) may be either an engine mounted shaft generator (EMG) (20) installed at the free-end of the main engine (10) or an in-line type shaft generator (20) installed at the propulsion shaft between the main engine (10) and the propulsion unit.

[0044] Since the shaft generator (20) receives power from the rotation of the propulsion shaft and generates electric power, as the load of the shaft generator (20) increases, the amount of power drawn from the main engine (10) increases, and as the load of the shaft generator (20) decreases, the amount of power drawn from the main engine (10) decreases.

[0045] Meanwhile, the shaft generator (20) can operate not only in a power take-out (PTO) mode in which a portion of the power supplied to the propulsion unit from the main engine (10) is extracted, but also in a power take-in (PTI) mode in which the propulsion shaft is rotated when power is supplied from outside to assist the propulsion power of the main engine (10).

[0046] The first converter (30) converts the variable frequency AC power generated by the shaft generator (20) into DC power. This eliminates voltage and frequency fluctuations due to changes in rotational speed, enabling stable power conversion. Meanwhile, the first converter (30) can operate as an inverter that converts DC power into AC power and supplies it when power is supplied from the DC link to the shaft generator (20) (e.g., when the shaft generator operates in PTI mode). That is, the first converter (30) is an AC-DC / DC-AC dual-purpose conversion device configured to enable bidirectional power flow, and can flexibly control the power conversion direction according to the driving mode of the propulsion shaft.

[0047] The second converter (40) reconverts the direct current power transmitted via the DC link into alternating current power with the voltage, frequency, and phase conditions required by the ship's system and supplies it to the switchboard or system load. This enables the supply of power appropriate for the rated alternating current load and enables flexible response to various system demands.

[0048] Meanwhile, the second converter (40) performs a rectifier operation to convert AC power into DC power when power from the AC grid is supplied to the DC link. In other words, the second converter (40) is a DC-AC / AC-DC dual-purpose conversion device configured to enable bidirectional power flow, and can flexibly control the power conversion direction depending on the conditions of the system load or the operating mode.

[0049] The auxiliary propulsion device (50) is a device that consumes electric power to supplement the propulsion power of the ship. In the present embodiment, the auxiliary propulsion device may include at least one of a wind-assisted propulsion system (WAPS), such as a wing sail or a rotor sail, which assists the propulsion of the ship using wind power, and an air lubrication system (ALS) that forms a micro-bubble layer on the bottom of the ship to reduce frictional resistance.

[0050] This auxiliary propulsion device (50) functions as a load that consumes power while also assisting the propulsion power to indirectly reduce the operating load of the main engine (10). Meanwhile, the power consumption of this auxiliary propulsion device (50) (i.e., the amount of fuel used to drive the auxiliary propulsion device (50)) and the amount of propulsion power assisted by the auxiliary propulsion device (50) may vary depending on various conditions such as sea conditions, wind speed, wind direction, ship's operating speed, and cargo loading.

[0051] A power generation unit (60) is installed onboard and generates AC power under the control of the control unit. The power generation unit (60) includes a generator engine that consumes fuel to generate rotational power and a generator that rotates using the rotational power provided by the generator engine to generate AC power. In this case, the generator may be a diesel generator, but is not limited thereto.

[0052] Meanwhile, in the case of a device that generates power by consuming fuel, such as a main engine (10), the amount of fuel consumed to produce a certain output (specific fuel consumption; SFC) varies depending on the output (i.e., driving load). In other words, the fuel consumption efficiency of the main engine (10) varies depending on the output of the main engine (10).

[0053]

[0054] Fig. 2 is a graph showing the SFC curve according to the output of the main engine (10). Referring to Fig. 2, as the output of the main engine (10) gradually increases from 0, the SFC gradually decreases, and when the output of the main engine (10) passes the optimum efficiency output, the SFC gradually increases again.

[0055] In the embodiment of Fig. 2, the optimal efficiency output of the main engine (10) is formed at approximately 65% ​​of the rated output. This means that the main engine (10) is most fuel-efficient when operated at an output of approximately 65% ​​of the optimal efficiency output, and the fuel efficiency decreases as the engine deviates from the optimal efficiency output.

[0056] In this way, since the fuel consumption of the main engine (10) varies depending on the current output status of the main engine (10), the fuel amount of the main engine (10) required to drive the auxiliary propulsion device (50) also has a variable value depending on the output of the main engine (10).

[0057] Therefore, if the auxiliary propulsion device (50) is always driven, the fuel saving effect of the main engine (10) may be minimal or rather, the energy efficiency of the entire system may be reduced, so it is desirable to dynamically control the driving of the auxiliary propulsion device.

[0058] Meanwhile, in this embodiment, the optimal efficiency output refers to the output state in which the fuel consumption efficiency of the main engine (10) is the highest, and this may be a single specific output value or a certain range of output sections. For example, the optimal efficiency output may be defined as a section in which the output of the main engine (10) is 50% or more and 70% or less of the rated output.

[0059]

[0060] In this embodiment, the control unit controls the operation of the auxiliary propulsion unit (50) based on the influence of the operation of the auxiliary propulsion unit (50) on the overall propulsion efficiency of the ship. The control unit determines the operation of the auxiliary propulsion unit (50) by comparing the fuel consumption of the power generation source (e.g., shaft generator (20), power generation unit (60), etc.) to be increased to operate the auxiliary propulsion unit (50) with the fuel consumption of the main engine (10) to be reduced by the propulsion power assisted by the auxiliary propulsion unit (50).

[0061] In one embodiment of the present invention, the auxiliary propulsion device (50) may be driven by consuming at least a portion of the power generated by the shaft generator (20). As described above, the shaft generator (20) generates power by extracting at least a portion of the power generated from the main engine (10), so when the load of the shaft generator (20) increases, the load of the main engine (10) also increases, resulting in additional fuel consumption.

[0062] The control unit determines the operation of the auxiliary propulsion device by comparing the fuel consumption of the power generation source that will increase due to the operation of the auxiliary propulsion device (50) with the fuel consumption of the main engine (10) that will be reduced due to the propulsion power assisted by the auxiliary propulsion device (50).

[0063] When the control unit determines that the fuel consumption of the main engine (10) to be reduced is greater than the fuel consumption of the fuel amount of the power source to be increased to drive the auxiliary propulsion unit (50), it controls the auxiliary propulsion unit (50) to be driven.

[0064] If the amount of fuel consumption to be reduced of the main engine (10) is less than the amount of fuel consumption to be increased of the power source, it is determined that the operation of the auxiliary propulsion device (50) lowers the overall efficiency of the system, and the auxiliary propulsion device (50) is controlled not to be operated.

[0065] Meanwhile, in another embodiment of the present invention, the control unit can determine whether to drive the auxiliary propulsion device (50) based on a preset and stored lookup table, without calculating the fuel consumption of the power source and the main engine (10) in real time.

[0066] The lookup table includes fuel consumption characteristics such as fuel consumption, fuel consumption efficiency, SFOC, etc. according to the load ratio of each power generation source and main engine (10), and the control unit can estimate the fuel consumption of the power generation source and main engine (10) that will increase when the auxiliary propulsion device is operated using the lookup table.

[0067] More specifically, the control unit checks the amount of power required to drive the current auxiliary propulsion device (50), calculates the load factor of the currently operating power source and main engine (10), and then extracts a fuel consumption coefficient corresponding to the load factor from the lookup table.

[0068] Thereafter, by using the power amount and fuel consumption coefficient required to drive the auxiliary propulsion device (50), the fuel consumption of the power generation source required to drive the auxiliary propulsion device (50) is calculated, and by comparing this with the fuel consumption of the main engine (10) saved by driving the auxiliary propulsion device (50), it is possible to determine whether to drive the auxiliary propulsion device (50).

[0069] Meanwhile, the control unit does not predict and compare the fuel consumption of the power generation source that will increase due to the operation of the auxiliary propulsion device (50) and the fuel consumption of the main engine (10) that will decrease due to the operation of the auxiliary propulsion device (50) in advance, but instead calculates and compares the fuel consumption of the power generation source that will increase due to the operation of the auxiliary propulsion device (50) and the fuel consumption of the main engine (10) that will decrease due to the operation of the auxiliary propulsion device (50) in real time, thereby determining whether to operate the auxiliary propulsion device (50).

[0070] In this embodiment, the control unit can control the output of the main engine (10) based on the speed of the ship with the auxiliary propulsion device (50) driven and the target speed of the ship.

[0071] The control unit monitors the current speed of the vessel and the target speed of the vessel while the auxiliary propulsion device (50) is operating. If the monitoring results show that the vessel's speed falls short of the target speed even though the auxiliary propulsion device (50) is operating and providing propulsion assistance, the control unit increases the output of the main engine (10) so that the vessel's speed approaches the target speed.

[0072] On the other hand, if the monitoring results show that the auxiliary propulsion device (50) is driven and the propulsion is assisted, and the speed of the ship exceeds the target speed, the control unit reduces the output of the main engine (10) so that the speed of the ship approaches the target speed.

[0073]

[0074] Meanwhile, the amount of power generated by the shaft generator (20) may be less than the rated capacity of the shaft generator (20) if the capacity of power available for extraction from the main engine (10) is limited. Accordingly, a situation may arise where the power generated by the shaft generator (20) is insufficient to supply the system load and auxiliary propulsion device (50) of the ship.

[0075] In this way, when the shaft generator (20) cannot supply power to drive the auxiliary propulsion device (50), at least one of changing the driving state of the auxiliary propulsion device (50) or changing the power source that supplies power to the auxiliary propulsion device (50) is performed.

[0076] In one embodiment of the present invention, if the control unit determines that the auxiliary propulsion unit (50) is driven by the power generated by the shaft generator (20) and that the capacity of the power that can be withdrawn from the main engine (10) is limited and the shaft generator (20) generates power less than the rated capacity, the control unit may stop at least some of the auxiliary propulsion units (50) installed in the ship, or reduce the power consumption of each auxiliary propulsion unit (50), i.e., supply less power to each auxiliary propulsion unit (50). Accordingly, the operating load of the main engine (10) is reduced, but the amount of propulsion power assisted by the auxiliary propulsion unit (50) is also reduced. The control unit may calculate and compare, for each combination of auxiliary propulsion units (50) that can be operated by the power generation amount of the shaft generator (20), the amount of fuel to be additionally consumed by the main engine (10) to drive each combination and the amount of fuel to be reduced by the driving of each combination of the auxiliary propulsion units (50).

[0077] As a result of the comparison, the control unit can drive the auxiliary propulsion device (50) by selecting the most efficient combination among combinations in which the fuel decrease of the main engine (10) is greater than the fuel increase of the main engine (10).

[0078] For example, if three auxiliary propulsion units (50) are installed on a ship and the power generation of the shaft generator (20) is such that only two auxiliary propulsion units (50) can be driven, the control unit can calculate the fuel reduction amount and the fuel increase amount of the main engine (10) for each combination of the first auxiliary propulsion unit, the second auxiliary propulsion unit, the third auxiliary propulsion unit, the first auxiliary propulsion unit and the second auxiliary propulsion unit, the first auxiliary propulsion unit and the third auxiliary propulsion unit, and the second auxiliary propulsion unit and the third auxiliary propulsion unit, and drive the auxiliary propulsion unit (50) of the most efficient combination.

[0079] Meanwhile, when the amount of fuel to be increased for driving the auxiliary propulsion device (50) is compared with the amount of fuel to be saved by the auxiliary propulsion device (50), and the amount of fuel to be increased is higher, the control unit can control the power generation unit (60) to supply power to the auxiliary propulsion device (50) in consideration of the efficiency of the entire ship system.

[0080] Meanwhile, if driving the auxiliary propulsion device (50) with the power generation unit (60) increases the efficiency of the entire ship system, the control unit controls the auxiliary propulsion device (50) to be driven by the power generation unit (60). However, if driving the auxiliary propulsion device (50) with the power generation unit (60) decreases the efficiency of the entire ship system, the control unit controls the auxiliary propulsion device (50) not to be driven, thereby increasing the overall efficiency of the ship propulsion and power system.

[0081]

[0082] According to the second embodiment of the present invention, the control unit can control the power output of the shaft generator (20) based on the output of the main engine (10) and the operation of the auxiliary propulsion device (50). Below, the differences between this embodiment and the previous embodiment will be mainly explained, and any parts omitted will be replaced with the previous content. This also applies to other embodiments below.

[0083] As described above, the fuel consumption efficiency of the main engine (10) varies depending on the output of the main engine (10), and the control unit can improve the energy efficiency of the entire ship propulsion system by controlling the main engine (10) to operate at the optimal efficiency output with high fuel consumption efficiency.

[0084]

[0085] FIG. 3 is a graph for explaining a control operation according to a second embodiment of the present invention, showing the output of the main engine (10) that changes according to the driving of the auxiliary propulsion device (50) and the shaft generator (20).

[0086] The graph of Fig. 3 shows the output of the main engine (10) according to the rotation speed (i.e., rpm) of the main engine (10). Area A represents an area where the main engine (10) can operate stably, Area B represents an operating area where power can be extracted by the shaft generator (20), Area C represents an operating area requiring caution, and Area D represents a dangerous operating area where mechanical damage is a concern due to overload.

[0087] Here, even if the main engine (10) operates in area A, if the output of the main engine (10) is sufficiently high, power take-off by the shaft generator (20) is achieved within the rated limit, and sufficient power that can be taken out is secured, power take-off (PTO) by the shaft generator (20) can be achieved.

[0088] When the main engine (10) is operating to propel the ship at point a in FIG. 3, and power extraction by the shaft generator (20) is initiated, the rotation speed (rpm) of the main engine (10) does not increase, but the output increases as the torque increases, causing the operating point to move to point b.

[0089] Afterwards, as the power output by the shaft generator (20) continues to increase and reaches the rated PTO output, the output of the main engine (10) also increases, and point c, which is a cautionary operating range where excessive torque is required compared to the rotation speed of the main engine (10), is reached. Since such operating conditions are not desirable in terms of the mechanical stability of the engine, operation in that range is restricted for stable ship operation.

[0090] Meanwhile, when the main engine (10) is operating to propel the ship at point a, and propulsion assistance by the auxiliary propulsion device (50) is initiated, the operating load of the main engine (10) is reduced, the output is reduced, and the rotational speed (rpm) increases, causing the operating point to move to point d.

[0091] In this way, when the load on the main engine (10) is reduced by the propulsion assistance by the auxiliary propulsion device (50), the main engine (10) has room to provide higher torque at the same rotation speed, and accordingly, even if the rated PTO output is extracted by the shaft generator (20), the main engine (10) does not reach an overload state. Accordingly, the main engine (10) can extract the rated PTO output under the assistance of the auxiliary propulsion device (50) at point e.

[0092] Accordingly, the control unit controls the shaft generator (20) based on the output of the main engine (10) and the drive of the auxiliary propulsion device (50), thereby inducing the main engine (10) to stably operate at the optimal efficiency output, thereby stably extracting the rated PTO output.

[0093]

[0094] Fig. 4 is a graph for explaining the control operation of the control unit according to the present embodiment, and shows the fuel consumption according to the load of the main engine (10). Fig. 4(a) and Fig. 4(b) explain the fuel consumption characteristics based on the operating state of the main engine (10) under different operating conditions, respectively.

[0095] First, referring to Fig. 4(a), when the main engine (10) is operating to propel the ship at the operating point Point 1, the control unit initiates power extraction by the shaft generator (20) to increase the operating load of the main engine (10). Accordingly, the output of the main engine (10) increases, the operating point moves to Point 2, and the main engine (10) is operated with higher fuel consumption efficiency than at the existing operating point Point 1.

[0096] Meanwhile, when the control unit operates the auxiliary propulsion device (50) to assist the propulsion of the ship while the main engine (10) is operating at the operating point Point 1 to propel the ship, the operating load of the main engine (10) decreases, resulting in a decrease in output and an increase in rotational speed, and the operating point of the main engine (10) moves to Point 3.

[0097] In this state, the fuel consumption efficiency is lowered compared to when the main engine (10) is operated at the operating point Point 1. Accordingly, the control unit can control the main engine (10) to be operated at the operating point Point 4, which has a lower fuel consumption efficiency than the operating point Point 2 but higher than the existing operating point Point 1, by starting the power take-off by the shaft generator (20) to compensate for the output reduction by the auxiliary propulsion device (50) or by increasing the power take-off amount to increase the output of the main engine (10). In this way, the control unit can control the output of the main engine (10) to be the optimal efficiency output by controlling the power take-off amount of the shaft generator (20) in consideration of the output reduction of the main engine (10) due to the output of the auxiliary propulsion device (50).

[0098] In this embodiment, when the power generated by the shaft generator (20) is less than the power demand of the system load, the control unit can satisfy the power demand of the system load by stopping the auxiliary propulsion device (50) if it is being driven, or by driving the power generation unit (60).

[0099] On the other hand, when the power generated by the shaft generator (20) is greater than the power demand of the system load, the control unit can drive the auxiliary propulsion device (50) based on a comparison of the fuel consumption of the main engine (10) that will be increased by driving the auxiliary propulsion device (50) and the fuel consumption of the main engine (10) that will be reduced by the propulsion power assisted by the auxiliary propulsion device (50).

[0100]

[0101] Referring to Fig. 4(b), when the control unit controls the shaft generator (20) to extract power while the main engine (10) is operating at the operating point Point 1 to propel the ship, the output of the main engine (10) increases and the operating point moves to Point 2. In this state, the fuel consumption efficiency is lower than when the main engine (10) is operating at the operating point Point 1.

[0102] Meanwhile, when the control unit operates the auxiliary propulsion device (50) to assist the propulsion of the ship while the main engine (10) is operating at the operating point Point 1 to propel the ship, the operating load of the main engine (10) decreases, which reduces the output and moves the operating point of the main engine (10) to Point 3. In this case as well, the fuel consumption efficiency is lowered compared to when the main engine (10) is operating at the operating point Point 1.

[0103] Accordingly, the control unit can control the main engine (10) to operate at a similar level of fuel consumption efficiency as the existing operating point Point 1 by starting power extraction by the shaft generator (20) while the auxiliary propulsion device (50) is in operation, thereby increasing the output of the main engine (10), thereby moving the operating point of the main engine (10) from Point 3 to Point 4.

[0104] In other words, the control unit according to the present embodiment controls the power output of the propulsion generator (20) according to the output status of the main engine (10) and the operation of the auxiliary propulsion device (50), thereby allowing the main engine (10) to be operated at the optimal efficiency output.

[0105] In another embodiment of the present invention, when the output of the auxiliary propulsion device (50), i.e., the amount of output reduction of the main engine (10) due to the driving of the auxiliary propulsion device (50), is controllable, the control unit may control the main engine (10) to be stably operated at the optimal efficiency output by controlling the shaft generator (20) and the auxiliary propulsion device (50) in parallel based on the output of the main engine (10).

[0106]

[0107] Fig. 5 is a schematic diagram of a ship propulsion system according to a third embodiment of the present invention. Referring to Fig. 5, the ship propulsion system according to the present embodiment includes a main engine (10), a shaft generator (20), a power generation unit (60), and a control unit (not shown).

[0108] Typically, a ship's system load must be supplied with both active and reactive power. Active power is used to drive actual equipment, while reactive power is required to maintain the required electrical operating conditions for inductive loads. These active and reactive powers are generated by the generator of the power generation unit (60).

[0109] Meanwhile, the power factor, which indicates the operating efficiency of the generator, is the ratio of the active power to the apparent power. If it is low, power loss and fuel consumption increase, so the power factor of the power generation unit (60) must be maintained above a certain level.

[0110] However, the power generation unit (60) has limitations in finely adjusting the output of reactive power due to its mechanical characteristics, and in an environment where the active power and reactive power of the load fluctuate frequently, such as a ship system, it is difficult to maintain a stable target power factor with the power generation unit (60) alone.

[0111] In this embodiment, the control unit calculates the amount of active power and reactive power to be supplied to the system load of the ship, and controls the shaft generator (20) and the power generation unit (60) to each share and generate the active power and reactive power to be supplied to the system load. At this time, the control unit monitors the power factor of the operating power generation unit (60), and if the power factor of the power generation unit (60) is different from the target power factor, calculates reactive power for power factor correction, and then commands the calculated reactive power value to the shaft generator (20) to perform power factor correction, thereby allowing the power generation unit (60) to operate at the target power factor.

[0112] The control unit according to the present embodiment controls the shaft generator (20) to generate reactive power to increase the power factor of the power generation unit (60), thereby controlling the power factor of the power generation unit (60) to be equal to or greater than the target power factor.

[0113] In one embodiment of the present invention, when the shaft generator (20) and the power generation unit (60) are operated in parallel and in a symmetrical operation state in which the active power is equally shared, the power factor of the power generation unit (60) can be improved by allowing the shaft generator (20) to generate more reactive power than the power generation unit (60) to increase the power factor of the generator.

[0114] Meanwhile, in an asymmetrical operating state where the active power distribution of the shaft generator (20) and the power generation unit (60) is not equal, control is possible to improve the power factor by reducing the reactive power burden on the power generation unit (60) side even if the shaft generator (20) does not generate more reactive power than the power generation unit (60). In this way, the power factor reference value can be changed according to the operating conditions and load characteristics, and the control unit can control the power factor of the power generation unit (60) to be maintained above a set target value by appropriately supplying reactive power through the shaft generator (20).

[0115]

[0116] In one embodiment of the present invention, the control unit can control the generation of active power and reactive power to be supplied to the ship system load based on the respective capacities of the shaft generator (20) and the generation unit (60). First, the control unit allocates the amount of active power generated to the shaft generator (20) and the generation unit (60) in proportion to the respective capacities of the shaft generator (20) and the generation unit (60).

[0117] Thereafter, the control unit calculates the amount of reactive power to be generated by the power generation unit (60) based on the amount of active power generated and the target power factor of the power generation unit (60) allocated to the power generation unit (60), and allocates this to be generated by the power generation unit (60).

[0118] And, the remaining reactive power, excluding the reactive power allocated to the power generation unit (60) among the total reactive power required for the system load, is allocated to the shaft generator (20). That is, according to the present embodiment, the shaft generator (20) generates and supplies additional reactive power for power factor compensation of the power generation unit (60).

[0119] For example, it is assumed that the rated capacity of the power generation unit (60) is 600 kW, the rated capacity of the shaft generator (20) is 600 kW, the active power required for the entire system load is 1,000 kW, the total reactive power required for the system load is 500 kVAR, and the target power factor of the power generation unit (60) is 0.95.

[0120] The control unit allocates 500 kW of effective power to each of the power generation unit (60) and the shaft generator (20) by considering the rated capacity and operating margin of the two generators. This implements a symmetrical operating state based on the effective power.

[0121] Thereafter, the control unit calculates the reactive power amount of approximately 164 kVAR required when the power generation unit (60) generates 500 kW of active power at a power factor of 0.95, allocates the calculated 164 kVAR as the reactive power amount to be generated by the power generation unit (60), and allocates the remaining 336 kVAR as the reactive power amount to be generated by the shaft generator (20).

[0122] Accordingly, among the total reactive power of 500 kVAR required for the system load, the power generation unit (60) supplies only the minimum reactive power required to satisfy the power factor condition, and the shaft generator (20) supplies more additional reactive power, thereby performing power factor correction of the entire system.

[0123] As another example, it is assumed that the rated capacity of the power generation unit (60) is 1,000 kW, the rated capacity of the shaft generator (20) is 500 kW, the active power required for the entire system load is 1,200 kW, the total reactive power required for the system load is 600 kVAR, and the target power factor of the power generation unit (60) is 0.95. First, the control unit allocates active power generation amounts of 800 kW and 400 kW to the power generation unit (60) and the shaft generator (20), respectively, in proportion to the rated capacities of the two generators.

[0124] Thereafter, the control unit calculates the reactive power amount of approximately 263 kVAR required when the power generation unit (60) generates 800 kW of active power at a power factor of 0.95, allocates the calculated 263 kVAR as the reactive power amount to be generated by the power generation unit (60), and allocates the remaining 337 kVAR as the reactive power amount to be generated by the shaft generator (20).

[0125] Accordingly, when the reactive power of 600 kVAR to be supplied to the system load is allocated as 400 kVAR and 200 kVAR in proportion to the capacities of the power generation unit (60) and the shaft generator (20), respectively, the power generation unit (60) generates and supplies 37 kVAR less reactive power, and the shaft generator (20) additionally generates and supplies 37 kVAR of reactive power, thereby performing power factor compensation of the power generation unit (60).

[0126]

[0127] As another example, it is assumed that the rated capacity of the power generation unit (60) is 1,000 kW, the rated capacity of the shaft generator (20) is 500 kW, the active power required for the entire system load is 1,200 kW, the total reactive power required for the system load is 600 kVAR, and the target power factor of the power generation unit (60) is 0.90.

[0128] First, the control unit allocates effective power generation of 800 kW and 400 kW to the power generation unit (60) and the shaft generator (20), respectively, in proportion to the rated capacities of the two generators.

[0129] Thereafter, the control unit calculates the reactive power amount of approximately 387 kVAR required when the power generation unit (60) generates 800 kW of active power at a power factor of 0.90, allocates the calculated 387 kVAR as the reactive power amount to be generated by the power generation unit (60), and allocates the remaining 213 kVAR as the reactive power amount to be generated by the shaft generator (20).

[0130] From this, it can be seen that even if the shaft generator (20) generates less reactive power than the power generation unit (60), the power factor of the power generation unit (60) can reach the target value.

[0131]

[0132] Meanwhile, when the shaft generator (20) performs power factor compensation due to power withdrawal and additional reactive power generation at the same time, the control unit can control the amount of reactive power generated by the shaft generator (20) by variably controlling the amount of power withdrawal by the shaft generator (20) so that the amount of reactive power generated by the shaft generator (20) does not increase excessively.

[0133] For example, if there is a concern that the voltage state of the DC power system within the shaft generator may exceed an allowable range as the amount of reactive power generated by the shaft generator (20) increases, the control unit may control to limit the reactive power generation of the shaft generator (20).

[0134] In addition, when it is determined that the current in the shaft generator (20) will increase excessively due to an increase in the power output of the shaft generator (20), the control unit can secure the stability of the system by preferentially limiting the generation of reactive power while preferentially maintaining the effective power output of the shaft generator (20).

[0135]

[0136] In another embodiment of the present invention, the control unit can control the shaft generator (20) and the power generation unit (60) to generate effective power to be supplied to the ship system load by sharing the power generation based on the fuel consumption efficiency of each of the shaft generator (20) and the power generation unit (60).

[0137] The control unit performs simulations for various load combinations, from the load condition under which the power generation unit (60) can be operated with the highest fuel consumption efficiency, to the load condition under which the shaft generator (20) can be operated with the highest fuel consumption efficiency while gradually reducing the operating load of the power generation unit (60) and gradually increasing the operating load of the shaft generator (20), thereby calculating the fuel consumption efficiency of the entire ship propulsion system for each combination.

[0138] As a result of the calculation, a load combination that maximizes the fuel consumption efficiency of the entire system is derived, and accordingly, the control unit optimally distributes the effective power to the power generation unit (60) and the shaft generator (20).

[0139] Meanwhile, the amount of power that can be output by the shaft generator (20) may be limited depending on the rotation speed (rpm) of the main engine (10) or the power take-off limit (PTO limit). For example, when the rpm of the main engine (10) is low, the rotation speed and torque of the shaft generator (20) may be limited and may not reach the rated output, and even when the maximum allowable power take-off amount is exceeded, an output restriction occurs.

[0140] Accordingly, the control unit monitors the real-time operating conditions of the shaft generator (20) to calculate the upper limit of the current outputtable power, and sets the range of effective power that can be allocated to the shaft generator (20) within the calculated upper limit.

[0141] Thereafter, the control unit can maximize the fuel consumption efficiency of each generator by optimizing the effective power distribution to the shaft generator (20) and the power generation unit (60) by considering the allowable output of the shaft generator (20).

[0142]

[0143] The fourth embodiment of the present invention is different from the previous embodiment in that the shaft generator (20) operates in a power take-out (PTO) mode in which a portion of the power supplied to the propulsion unit from the main engine (10) is extracted, or in a power take-in (PTI) mode in which the propulsion shaft is rotated when power is supplied from the outside to assist the propulsion power of the main engine (10).

[0144] In ship operation, even if the ship moves at the same speed, the output of the main engine (10) continuously changes depending on sea conditions, etc., and this change in output reduces the fuel consumption efficiency of the main engine (10).

[0145] To solve this problem, the control unit according to the present embodiment switches the operation mode of the shaft generator (20) based on the operating load (i.e., output) of the main engine (10), thereby controlling the main engine (10) to be operated at the optimal efficiency load with the highest fuel consumption efficiency.

[0146]

[0147] Fig. 6 is a drawing to help understand the present embodiment, and is a graph showing fuel consumption per unit output according to the operating load of the main engine (10). Referring to Fig. 6, when the operating load of the main engine (10) has a value "A" exceeding the optimal efficiency load "C", the control unit controls the shaft generator (20) to operate in PTI mode, thereby reducing the operating load of the main engine (10), thereby allowing the main engine (10) to operate under load conditions close to the optimal efficiency load "C".

[0148] Meanwhile, when the driving load of the main engine (10) has a value “B” that is less than the optimal efficiency load “C”, the control unit controls the shaft generator (20) to operate in PTO mode to increase the driving load of the main engine (10), thereby allowing the main engine (10) to operate at a load close to the optimal efficiency load “C”.

[0149] In this way, the control unit according to the present embodiment switches the operation mode of the shaft generator (20) to PTO mode or PTI mode based on the operation load of the main engine (10), and accordingly, the operation load of the main engine (10) is adjusted, thereby controlling the main engine (10) to be operated at the optimal efficiency load.

[0150] Meanwhile, the ship can move at a speed different from the target speed while the operating mode of the shaft generator (20) is controlled by the control unit so that the main engine (10) is operated at the optimal efficiency load. At this time, the control unit can control the ship to move at the target speed by adjusting at least one of the power output of the shaft generator (20) and the output of the main engine (10).

[0151] More specifically, when the speed of the ship exceeds the target speed while the main engine (10) is operating at the optimal efficiency load, the control unit operates the shaft generator (20) in PTO mode to increase the power output, thereby reducing the speed of the ship while maintaining the main engine (10) at the optimal efficiency load operating state.

[0152] At this time, if the power output of the shaft generator (20) reaches the maximum, but the speed of the ship is still higher than the target speed, the control unit reduces the output of the main engine to control the speed of the ship.

[0153] On the other hand, when the speed of the ship falls short of the target speed while the main engine (10) is operating at the optimal efficiency load, the control unit operates the shaft generator (20) in PTI mode to apply rotational force to the propulsion shaft, thereby increasing the speed of the ship while maintaining the main engine (10) at the optimal efficiency load operating state.

[0154] Meanwhile, if the speed of the ship is still lower than the target speed even though the power supply of the shaft generator (20) has reached the maximum, the control unit controls the speed of the ship by increasing the output of the main engine (10).

[0155] In this way, according to the present embodiment, in order for the control unit to match the speed of the ship with the target speed, the control unit first controls the operation mode and operation state of the shaft generator (20), and if the speed of the ship still does not reach the target speed, secondarily controls the output of the main engine (10), thereby maintaining the main engine (10) to be operated at the maximum optimal efficiency load.

[0156] Meanwhile, in a situation where the main engine (10) is operated at an operating load other than the optimal efficiency load, if it is necessary to match the speed of the ship to the target speed, the control unit according to the present embodiment can preferentially control either the output of the main engine (10) or the operating state of the shaft generator (20) based on the direction of change in fuel consumption efficiency according to the output control of the main engine (10).

[0157] More specifically, in a situation where the main engine (10) is operated at an operating load other than the optimal efficiency load, when the output of the main engine (10) is increased or decreased for ship speed adjustment, if it is determined that the fuel consumption efficiency of the main engine (10) increases accordingly, the control unit preferentially controls the output of the main engine (10).

[0158] On the other hand, if the fuel consumption efficiency of the main engine (10) is rather reduced according to the output control of the main engine (10), the control unit adjusts the ship speed by preferentially controlling the operation mode or operation state of the shaft generator (20).

[0159] In this embodiment, the control unit controls the output of the main engine (10) so that it does not change according to the power output or power supply of the shaft generator (20) while the shaft generator (20) is operating in PTO or PTI mode, thereby allowing the main engine (10) to stably maintain an output state for reaching the target speed.

[0160]

[0161] Fig. 7 is a schematic diagram of a ship propulsion system according to a fifth embodiment of the present invention. Referring to Fig. 7, the ship propulsion system according to the present embodiment includes a main engine (10), a shaft generator (20), an auxiliary propulsion device (50), a fuel cell (70), and a control unit (not shown).

[0162] The fuel cell (70) outputs power according to the control of the control unit. In the present embodiment, the fuel cell (70) may be a solid oxide fuel cell (SOFC). The direct current power output by the fuel cell (70) is converted into a stable DC-link voltage by a DC-DC converter (71) and then supplied to the DC-link, and the power supplied to the DC-link is supplied to a shaft generator or a system load.

[0163] The control unit according to the present embodiment switches the operation mode of the shaft generator (20) based on the driving load of the main engine (10) and the propulsion power assisted by the auxiliary propulsion device (50), thereby controlling the main engine (10) to be operated at the optimal driving load with the highest fuel consumption efficiency.

[0164] As with the control unit of the first embodiment of the present invention, the control unit according to the present embodiment determines the driving of the auxiliary propulsion unit (50) by comparing the fuel consumption of the power generation source to be increased to drive the auxiliary propulsion unit (50) with the fuel consumption of the main engine (10) to be reduced by the propulsion power assisted by the auxiliary propulsion unit (50).

[0165] That is, if the control unit determines that the amount of fuel consumption to be reduced of the main engine (10) is greater than the amount of fuel of the power source to be increased to drive the auxiliary propulsion unit (50), it controls the auxiliary propulsion unit (50) to be driven.

[0166] In this embodiment, when the output of the main engine (10) is greater than the optimum efficiency output even though propulsion assistance is provided by driving the auxiliary propulsion device (50), the control unit reduces the load of the main engine (10) by controlling the shaft generator (20) to operate in PTI mode. Accordingly, the output of the main engine (10) is reduced, so that the main engine (10) can be operated at the optimum efficiency output.

[0167] Meanwhile, when the output of the main engine (10) is lower than the optimum efficiency output due to the propulsion assistance provided by the operation of the auxiliary propulsion device (50), the control unit controls the shaft generator (20) to operate in PTO mode, thereby increasing the load of the main engine (10). Accordingly, the output of the main engine (10) increases, so that the main engine (10) can be operated at the optimum efficiency output.

[0168] In one embodiment of the present invention, when the output of the main engine (10) is greater than the optimum efficiency output and the shaft generator (20) is operated in the PTI mode, the control unit can control at least a portion of the power output by the fuel cell (70) to be supplied to the shaft generator (20). Accordingly, the shaft generator (20) can reduce the output of the main engine (10) by rotating the propulsion shaft using the power output by the fuel cell (70).

[0169] Meanwhile, if the control unit determines that the power generated by the shaft generator (20) is insufficient to supply to the system load when the output of the main engine (10) is lower than the optimal efficiency output and operates the shaft generator (20) in PTO mode, the control unit can control the power output by the fuel cell (70) to be supplied to the system load as well. Accordingly, the output of the main engine (10) increases, and power can be stably supplied to the system load.

[0170]

[0171] Fig. 8 is a schematic diagram of a ship propulsion system according to a sixth embodiment of the present invention. Referring to Fig. 8, the ship propulsion system according to the sixth embodiment of the present invention differs from the previous embodiment in that it further includes a battery (80).

[0172] The battery (80) can store at least a portion of the power generated from the shaft generator (20) under the control of the control unit and discharge the stored power. The battery (80) stores and discharges direct current power, and the direct current power discharged from the battery (80) is converted into appropriate direct current power by the DC-DC converter (81) and then supplied to the direct current system. Here, the battery (80) can include a BMS (Battery Management System), a PCS (Power Conversion System), or an EMS (Energy Management System).

[0173] When the output of the main engine (10) is greater than the optimum efficiency output and the shaft generator (20) is operated in PTI mode, the control unit can control the shaft generator (20) to operate in PTI mode by discharging the battery (80) and using the power stored in the battery (80).

[0174] Accordingly, the shaft generator (20) can reduce the output of the main engine (10) by rotating the propulsion shaft using the power discharged by the battery (80).

[0175] Meanwhile, when the output of the main engine (10) is lower than the optimal efficiency output and the shaft generator (20) is operated in PTO mode, the control unit controls the power generated by the shaft generator (20) to be supplied to the system load and the remaining power to be stored in the battery (80), thereby increasing the output of the main engine (10) and efficiently managing power.

[0176] In this embodiment, the control unit monitors the remaining state of charge (SoC) and the charge and discharge rate (C-rate) of the battery, and when the SoC reaches an upper or lower threshold or the C-rate exceeds a limit, the control unit can limit the operation of the main engine (10) at the optimal efficiency output to protect the battery.

[0177]

[0178] The present invention encompasses all embodiments resulting from a combination of the above embodiments and known techniques, in addition to the embodiments described above.

[0179] Although the present invention has been described in detail through specific examples, this is intended to specifically explain the present invention, and the present invention is not limited thereto, and it will be apparent that modifications and improvements can be made by those skilled in the art within the technical spirit of the present invention.

[0180] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims

1. A main engine that is connected to the propulsion system through a propulsion shaft and consumes fuel to generate propulsion power for the ship; A shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; An auxiliary propulsion device that consumes electricity to assist the propulsion power of the vessel; and A ship propulsion system, comprising a control unit that controls the operation of the auxiliary propulsion device based on a comparison of the fuel consumption of the power generation source that will be increased by the operation of the auxiliary propulsion device and the fuel consumption of the main engine that will be reduced by the propulsion power assisted by the auxiliary propulsion device.

2. In paragraph 1, The above control unit A ship propulsion system that controls the auxiliary propulsion device to be operated when, as a result of the above comparison, it is determined that the fuel consumption of the main engine to be reduced is greater than the fuel consumption of the power generation source to be increased.

3. In paragraph 1, The auxiliary propulsion device is driven by consuming at least a portion of the power generated by the shaft generator, The above control unit A ship propulsion system that controls the auxiliary propulsion device to be driven when it is determined that the fuel consumption of the main engine to be reduced by the propulsion power assisted by the auxiliary propulsion device is greater than the fuel consumption of the main engine to be increased by operating the shaft generator to drive the auxiliary propulsion device.

4. In paragraph 1, The above control unit A ship propulsion system that controls the output of the main engine based on the speed of the ship with the auxiliary propulsion device driven and the target speed of the ship.

5. In paragraph 4, The above control unit While the above auxiliary propulsion device is operating, A ship propulsion system that controls the output of the main engine to be reduced when the speed of the ship exceeds the target speed of the ship.

6. In paragraph 4, The above control unit While the above auxiliary propulsion device is operating, A ship propulsion system that controls the output of the main engine to increase when the speed of the ship falls short of the target speed of the ship.

7. In paragraph 3, The control unit, if it is determined that the shaft generator cannot supply power to drive the auxiliary propulsion device, A ship propulsion system that controls to change at least one of the driving state of the auxiliary propulsion device and the power source that supplies power to the auxiliary propulsion device.

8. In paragraph 3, The above auxiliary propulsion device is provided in multiple units, A ship propulsion system, wherein the control unit controls to stop at least some of the plurality of auxiliary propulsion devices or reduce the output of each auxiliary propulsion device when it is determined that the capacity of power that can be withdrawn from the main engine is limited and the shaft generator generates power below the rated capacity.

9. In paragraph 7, The control unit, if it is determined that the shaft generator cannot supply power to drive the auxiliary propulsion device, For each combination of auxiliary propulsion devices that can be operated with the power generation of the above-mentioned shaft generator, the fuel consumption of the main engine that will be increased to drive the auxiliary propulsion device of each combination and the fuel consumption of the main engine that will be reduced by the propulsion power assisted by the auxiliary propulsion device of each combination are calculated and compared, A ship propulsion system that controls the operation of the auxiliary propulsion device of the most efficient combination among the combinations in which the fuel decrease is greater than the fuel increase as a result of comparison.

10. In paragraph 7, It further includes a power generation unit that consumes fuel to generate electricity, The above control unit A ship propulsion system that changes the power generation source of the auxiliary propulsion device based on a comparison of the fuel consumption of the power generation unit that is to be increased to drive the auxiliary propulsion device and the fuel consumption of the main engine that is to be reduced by the propulsion power assisted by the auxiliary propulsion device, when it is determined that the fuel consumption of the main engine that is to be increased to drive the auxiliary propulsion device is greater than the fuel consumption of the main engine that is to be reduced by the propulsion power assisted by the auxiliary propulsion device.

11. In paragraph 10, The above control unit A ship propulsion system that changes the power source so that the auxiliary propulsion device is driven by the power generated by the power generation unit when it is determined that the fuel consumption of the main engine to be reduced by the propulsion power assisted by the auxiliary propulsion device is greater than the fuel consumption of the power generation unit to be increased to drive the auxiliary propulsion device.

12. In paragraph 1, A ship propulsion system, wherein the auxiliary propulsion device includes at least one of a wind-assisted propulsion system (WAPS) that assists propulsion of the ship using wind power and an air lubrication system (ALS).

13. In paragraph 1, The above control unit A ship propulsion system that estimates the fuel consumption of a power generation source that will increase due to the operation of the auxiliary propulsion device using a lookup table that includes fuel consumption characteristics according to the load rate of the main engine.

14. The main engine, which is connected to the propulsion unit through the propulsion shaft and consumes fuel to generate propulsion power for the ship; A power generating device that generates electricity; An auxiliary propulsion device that consumes electricity to assist the propulsion power of the vessel; and A ship propulsion system, comprising a control unit that controls the operation of the auxiliary propulsion device and the power generation device based on the effect of the operation of the auxiliary propulsion device on the overall propulsion efficiency of the ship.

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