Ship propulsion system

Abstract

The present invention relates to a ship propulsion system and, more specifically, to a ship propulsion system in which a fuel cell is provided so as to be capable of outputting power equal to or greater than the electric power demand of a system load required during normal seagoing of a ship, and a control unit controls the supply of power generated by the fuel cell to the system load and the shaft generator on the basis of the seagoing mode of the ship, thereby reducing unnecessary operation of a power generation unit and improving ship system efficiency.

Description

ship propulsion system

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

[0002] Conventional ship propulsion systems typically utilize an internal combustion engine-based main engine to rotate a propulsion shaft, which in turn drives propellers and other propulsive devices to generate propulsion. Additionally, independent generator systems are installed and operated separately onboard the ship to supply power to various system loads, such as navigation, lighting, communications, and cargo handling.

[0003] These power generation systems are typically based on diesel generators, which consume diesel fuel to produce electricity. This leads to high fuel costs and significant greenhouse gas emissions, posing a significant environmental burden. Consequently, various eco-friendly technologies are being developed to reduce fuel consumption and carbon emissions. As part of this effort, efforts are actively underway to introduce fuel cells to ships.

[0004] Fuel cells are devices that generate electricity through the electrochemical reaction of hydrogen and oxygen. They boast the advantages of high efficiency and zero carbon dioxide emissions. Solid oxide fuel cells (SOFCs), in particular, offer the advantage of high-temperature operation, enabling them to be integrated with cogeneration and various heat management technologies. However, fuel cells are generally optimized for constant output operation, making it difficult to actively respond to real-time load fluctuations, a technical limitation.

[0005] Meanwhile, conventional shaft generators, which generate electricity using the rotational power of the main engine, offer the economic advantage of being able to generate electricity without additional fuel consumption during operation. Recently, dual-use systems, where shaft generators are used not only for power supply (PTO; Power Take-Off) but also for propulsion assistance (PTI; Power Take-In), utilizing external power to re-supply power to the propulsion shaft, are becoming more common.

[0006] In line with this technological trend, fuel cell-based power generation systems, hybrid propulsion systems with shaft generators and PTI / PTO functions, high-efficiency power conversion converter technology, and peak load supplement technology using batteries are being integrated, increasing the need for smart power control and distribution systems that can adapt to various operating conditions on board ships (e.g., sailing, entering and leaving port, unloading, waiting).

[0007] The purpose of the present invention is to provide a ship propulsion system with improved efficiency using a fuel cell. 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.

[0008] A ship propulsion system according to one aspect of the present invention comprises: a shaft generator that generates power using the rotational power of a propulsion shaft or receives power from an external source and applies rotational power to the propulsion shaft; a fuel cell capable of outputting power exceeding the power demand of a system load required during normal seagoing of a ship; and a control unit that controls the supply of power to the system load and the shaft generator, wherein the control unit controls the supply of power generated by the fuel cell to the system load and the shaft generator based on the operation mode of the ship.

[0009] The above control unit can control the power supplied by the fuel cell to be supplied to the system load with priority when the ship is operating in a normal operation mode, and the remaining power supplied to the system load to be supplied to the shaft generator.

[0010] The ship further includes a power generation unit that supplies power by consuming fuel, and the control unit can control the power generation unit to supply the insufficient power by driving the power generation unit when the ship is operating in a loading mode or an unloading mode and the power supplied by the fuel cell is less than the power demand of the system load required in the loading mode or the unloading mode.

[0011] The control unit can control the supply of power generated by the fuel cell based on the power demand of the system load when the ship is operating in port in / out mode.

[0012] The control unit can control the power generated by the fuel cell to be supplied to the system load in full when the ship is operating in the port entry / exit mode and the power demand of the system load is greater than the maximum output of the fuel cell, and the power generation unit to supply the insufficient power.

[0013] The control unit can control the ship to supply power generated by the fuel cell to the system load with priority and to supply the remaining power to the shaft generator to assist propulsion when the ship is operating in the port entry / exit mode and the power demand of the system load is less than the maximum output of the fuel cell.

[0014] The fuel cells are provided in two numbers, and the control unit can control the power supply of the fuel cells and the power generation unit based on the system efficiency according to the use of the fuel cells and the power generation unit when the ship is operating in port entry and departure mode, the output of each fuel cell is less than the power demand of the system load, and the total output of the two fuel cells exceeds the power demand of the system load.

[0015] The control unit calculates the system efficiency when the ship is operating in the entry / exit mode, supplies power to the system load using the two fuel cells, and then supplies the remaining power to the shaft generator to assist propulsion, and the system efficiency when the power is supplied to the system load using one of the fuel cells, and then supplies the shortfall by generating it with the power generation unit, and can control the power supply by the fuel cell and the power generation unit in a manner that has a higher system efficiency.

[0016] The above control unit can control the fuel cell to stop generating power and to operate only the power generation unit to supply power while the ship is operating in a harbor idle mode.

[0017] The above-mentioned shaft generator and the above-mentioned fuel cell can be connected to each other by the same DC link (DC-link).

[0018] The invention further includes a converter that converts direct current power output by the fuel cell into the DC link voltage and supplies it to the DC link, and the control unit can control the fuel cell to operate at constant output by controlling the output current of the converter.

[0019] A ship propulsion system according to another aspect of the present invention includes: a shaft generator that generates power using the rotational power of a propulsion shaft or receives power from an external source and applies rotational power to the propulsion shaft; a fuel cell capable of outputting power exceeding the power demand of a system load required during normal seagoing of a ship; and a control unit that controls the supply of power to the system load and the shaft generator, wherein the control unit controls the supply of power generated by the fuel cell to the system load and the shaft generator based on whether rotational power is applied by the shaft generator and the size of the power demand of the system load.

[0020] The present invention has the effect of improving the efficiency of a propulsion system using a fuel cell. 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.

[0021] Figure 1 is a schematic diagram of a ship propulsion system according to a first embodiment of the present invention.

[0022] Figure 2 is a schematic diagram of a ship propulsion system according to a third embodiment of the present invention.

[0023] Figure 3 is a schematic diagram of a ship propulsion system according to a fourth embodiment of the present invention.

[0024] Figure 4 is a schematic diagram of a ship propulsion system according to a fifth embodiment of the present invention.

[0025] Figure 5 is a schematic diagram of a ship propulsion system according to a sixth embodiment of the present invention.

[0026] Figure 6 is an operation state diagram of a ship propulsion system according to a sixth embodiment of the present invention.

[0027] Figure 7 is a schematic diagram of a ship propulsion system according to the seventh embodiment of the present invention.

[0028] Figure 8 is an operation state diagram of a ship propulsion system according to the seventh embodiment of the present invention.

[0029] Figure 9 is a schematic diagram of a ship propulsion system according to the eighth embodiment of the present invention.

[0030] Figure 10 is an operation state diagram of a ship propulsion system according to the eighth embodiment of the present invention.

[0031] Figure 11 is an operation state diagram of a ship propulsion system according to the eighth embodiment of the present invention.

[0032] The objects, 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 assigned 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.

[0033] 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.

[0034] Additionally, terms that include 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0040]

[0041] FIG. 1 is a conceptual 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.

[0042] Referring to FIG. 1, a ship propulsion system (1) according to an embodiment of the present invention includes a main engine (10), a shaft generator (20), a first converter (30), a fuel cell (40), a second converter (45), a third converter (50), a transformer (60), a power generation unit (70), and a control unit (not shown).

[0043] The main engine (10) is connected to a propulsion device installed at the stern via a propulsion shaft, and the rotational force generated by the main engine is transmitted to the propulsion device via the propulsion shaft to propel the vessel. At this time, the propulsion device may be a propeller, and the propeller can rotate by the rotational force from the main engine, thereby forming a fluid flow and moving the vessel forward.

[0044] 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 (Power Take-Off 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 power generation using the shaft generator is effective in saving energy through economical power generation during ship operation.

[0045] Meanwhile, the shaft generator (20) can operate as a motor that rotates the propulsion shaft when power is supplied from the outside, thereby assisting the propulsion power of the main engine (10), and in this case, it functions as a power take-in (PTI).

[0046] That is, the shaft generator (20) functions as a generator that produces electricity by utilizing the surplus power of the main engine (10) in PTO mode, and can operate as a boost motor that applies rotational force to the propulsion shaft together with the main engine (10) in PTI mode.

[0047] The shaft generator (20) may be an engine mounted type (Engine Mounted Shaft Generator, EMG) installed at the free end of the main engine (10) or an in-line type (In-line type shaft generator) installed on the propulsion shaft between the main engine (10) and the propulsion unit.

[0048] The first converter (30) converts the variable frequency AC power generated by the shaft generator (20) into DC power and supplies it to the DC link. This eliminates fluctuations in voltage and frequency due to changes in rotational speed, thereby enabling stable power conversion.

[0049] 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 depending on the driving mode of the propulsion shaft.

[0050] A fuel cell (40) generates and supplies electricity. The fuel cell (40) may be a solid oxide fuel cell (SOFC). In the present embodiment, the fuel cell (40) is connected to the same DC link as the shaft generator (20), and the DC power output by the fuel cell (40) is converted into a stable DC link voltage by a second converter (45) and then supplied to the DC link.

[0051] In this embodiment, the fuel cell (40) can output power exceeding the power demand of the system load required during normal seagoing of the vessel. Therefore, according to this embodiment, even if power is not supplied from the shaft generator (20) or the power generation unit (70) during normal seagoing of the vessel, sufficient power can be supplied to the system load using only the output of the fuel cell (40).

[0052] In addition, the fuel cell (40) according to the present embodiment can simultaneously supply power to the system load and the shaft generator (20) under the control of the control unit. That is, some of the power generated by the fuel cell (40) is supplied to the system load and some is supplied to the shaft generator (20) under the control of the control unit, so that the shaft generator (20) can operate in PTI mode.

[0053] The second converter (45) converts the DC power output by the fuel cell (40) into a stable DC link voltage and supplies it to the DC link.

[0054] The third converter (50) reconverts the direct current power transmitted via the DC link into alternating current power at the voltage, frequency, and phase conditions required by the ship's system and supplies it to the switchboard or system load. This ensures a stable supply of power suitable for the rated alternating current load and enables flexible response to various system demands.

[0055] Meanwhile, the third converter (50) 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 third converter (50) 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.

[0056] In the following embodiment, the DC link refers to a DC bus between the first converter (30) and the third converter (50).

[0057] The transformer (60) converts the AC power converted by the third converter (50) into a required voltage level and supplies it to the distribution panel. Accordingly, power loss is minimized and stable power transmission is enabled.

[0058] A power generation unit (70) is installed on board and generates AC power under the control of a control unit. The power generation unit (70) includes a generator engine that consumes fuel to generate rotational power and a generator that rotates by 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. The control unit controls the supply of power to the system load and the shaft generator (20). In the present embodiment, the control unit controls the power generated by the fuel cell (40) to be supplied to the system load and the shaft generator (20) based on the ship operation mode.

[0059] First, when the ship is operating in normal seagoing mode, the control unit supplies power generated by the fuel cell (40) to the system load with priority, and controls the remaining power after supplying it to the system load to be supplied to the shaft generator (20).

[0060] Accordingly, the power demand of the system load can be met without driving a separate power generation unit (70), and the remaining power can be used to assist propulsion. In addition, since the control unit controls to supply the output of the fuel cell (40) to the system load with priority and supply the remaining amount to the shaft generator (20), it is possible to flexibly respond to fluctuations in the system load.

[0061] Meanwhile, when the ship is operating in loading mode or unloading mode and the power generated by the fuel cell (40) falls short of the power demand of the system load in loading mode or unloading mode, the control unit controls the power generation unit (70) to supply the shortfall.

[0062] In this way, when the ship is operating in loading mode or unloading mode, the control unit supplies the power generated by the fuel cell (40) to the system load with priority, and when the power demand of the system load cannot be met with the output of the fuel cell (40) alone, the shortfall is controlled to be supplied by the power generation unit (70), thereby minimizing the operation of the power generation unit (70) with relatively low energy efficiency. In addition, by using the power generation unit (70), it is possible to flexibly respond to fluctuations in the system load.

[0063] In addition, when the ship is operating in port in mode or port out mode, the control unit can control the operation of the fuel cell (40) by considering the power demand of the system load and the efficiency of the entire system.

[0064] In one embodiment, when a ship is equipped with one fuel cell (40), the control unit can control the ship to supply all of the power generated by the fuel cell (40) to the system load when the power demand of the system load is greater than the maximum output of the fuel cell (40) in the ship's arrival mode or departure mode, and supply the shortfall by the power generation unit (70).

[0065] On the other hand, when the power demand of the system load is less than the maximum output of the fuel cell (40) in the ship's arrival or departure mode, the control unit can control to supply the power generated by the fuel cell (40) to the system load with priority and supply the remaining power to the shaft generator (20) to assist propulsion.

[0066] In another embodiment of the present invention, a vessel may be equipped with two or more fuel cells (40). In this case, the control unit may control the operation of the fuel cells (40) in consideration of the overall efficiency of the system when the power demand of the system load can be supplied by the output of all fuel cells (40) in the port arrival mode or the port departure mode, but the output of only some fuel cells (40) is insufficient.

[0067] For example, the control unit can control the system to be operated in a manner with high overall efficiency among supplying power to the system load using all fuel cells (40) and then supplying the remaining amount to the shaft generator (20) to assist propulsion, or supplying power to the system load using some fuel cells (40) and then generating and supplying the remaining amount to the power generation unit (70).

[0068] Meanwhile, when the ship is operating in harbor idle mode, the control unit can control the fuel cell (40) to stop generating power and operate only the power generation unit (70) to supply the required power. This is a control method that takes into account that the power required in harbor idle mode is at a very low level, such as a hotel load, and when the fuel cell is operated with a constant output power size, i.e., constant output operation, more power than necessary may be supplied, which may lower the efficiency of the entire system.

[0069] According to this embodiment, as the control unit controls the supply of power generated by the high-efficiency fuel cell and the operation of the power generation unit (70) based on the ship's operating mode, the operation of the power generation unit (70) is reduced, and thus the efficiency of the entire system can be increased.

[0070] Meanwhile, by supplying power to a system load using a fuel cell and applying the remaining power after power supply to the shaft generator (20) so that the shaft generator (20) operates in PTI mode, the capacity of the shaft generator (20) and the first converter (30) can be reduced. In addition, since the fuel cell (40) is connected to the same DC link as the shaft generator (20), the power generated by the fuel cell (40) can be supplied to the shaft generator (20) and the system load with less loss, thereby increasing system efficiency.

[0071]

[0072] Meanwhile, in the ship propulsion system (1) according to the present embodiment, the fuel cell (40), the shaft generator (20), and the power generation unit (70) are configured to operate selectively according to the operation mode, and the power supply path between these power sources and the load is configured to be integratedly controlled by the control unit, and the power supply target and distribution ratio can be adjusted according to the operation mode.

[0073] Accordingly, the DC link of this embodiment is not limited to a wiring structure that simply transmits power between individual devices, but can function as a common DC power network, i.e., a DC grid, to which each component is electrically connected.

[0074] More specifically, the shaft generator (20) converts the AC power generated through the first converter (30) into DC power and supplies it to the DC link, and the fuel cell (40) supplies the DC power output through the second converter by connecting it to the same DC link. In addition, the third converter (50) connected to the DC link converts the DC power into AC power required by the system load or switchboard and outputs it, and when necessary, the shaft generator (20) can receive power from the DC link and operate in PTI mode.

[0075] In this way, since the shaft generator (20), fuel cell (40), system load, and various power conversion devices are electrically connected through a DC link, which is a single DC power distribution line, the DC link functions as a common DC power grid that is electrically connected for power conversion and distribution, and accordingly, not only is high-efficiency power operation based on the fuel cell (40) possible, but the power flow within the system can be flexibly controlled according to the operating mode, thereby improving overall energy efficiency.

[0076] Since this DC link is a common power grid to which multiple power sources and loads are simultaneously connected, it is essential for the normal operation of the entire system that the voltage of the DC link be maintained stably. In particular, since the fuel cell (40) has the characteristic of operating while maintaining a constant current, it is also important to prevent the output current of the fuel cell (40) from excessively fluctuating. Accordingly, it is necessary to control so that both the DC link voltage and the output current of the fuel cell (40) are maintained stably.

[0077] In this embodiment, the control unit controls the output of the first converter (30) and the second converter so that the voltage of the DC link and the output current of the fuel cell (40) are constant. In this embodiment, the first converter (30) is a machine side converter (MSC) that performs control to keep the voltage of the DC link constant, and the third converter (50) connected to the grid side is a grid side converter (GSC) that operates to secure the voltage stability of the DC link in conjunction with the external AC grid voltage.

[0078] Meanwhile, since the fuel cell (40) has a characteristic of maintaining a constant output current, current control-based output stabilization is required in order for the output power of the fuel cell (40) to be supplied to the DC link without disturbance. To this end, the second converter connected to the fuel cell (40) stably controls the output current of the fuel cell (40) in conjunction with the power conversion operation of the third converter (50) in response to the DC link status that fluctuates according to the grid power demand.

[0079] In this embodiment, the control unit monitors the voltage status of the DC link in real time, and when it rises or falls below the reference voltage, controls the amount of power flowing into the DC link by adjusting the output current of the first converter (30). For example, when the shaft generator (20) is operating in PTO mode and the DC link voltage remains higher than the reference value, the control unit needs to suppress the power supplied to the DC link to prevent the voltage from rising.

[0080] To this end, the control unit reduces the current output to the DC link through the first converter (30) to thereby reduce the power supplied to the DC link from the shaft generator (20), thereby suppressing the voltage increase of the DC link. At this time, when the output current of the first converter (30) decreases, the electrical load applied to the shaft generator (20) decreases, and accordingly, the output torque of the shaft generator (20) also decreases. In other words, the output current control performed by the control unit is substantially the same as controlling the output torque of the shaft generator (20), and the two controls are physically linked and operated.

[0081] Conversely, when the DC link voltage falls below the reference value, the control unit increases the output current of the first converter (30) to increase the generated power, and accordingly, the power flowing into the DC link from the shaft generator (20) increases, and the DC link voltage is recovered.

[0082] Meanwhile, in the present embodiment, the third converter (50) operates as an inverter that converts direct current power supplied from the DC link into alternating current power and supplies power to the AC grid. At this time, the control unit controls the modulation method (PWM), the magnitude of the output current, and the phase angle of the third converter (50) so as to be synchronized with the target voltage, frequency, and phase of the AC grid, thereby enabling stable power to be supplied to the AC grid under rated conditions.

[0083] This conversion operation can be stably performed only when the voltage of the DC link is maintained at a constant reference value, and if the DC link voltage fluctuates, the output voltage quality or waveform distortion of the third converter (50) may occur. Therefore, the control unit maintains the DC link voltage stably by controlling the first converter (30) or the second converter (45), and controls the third converter (50) to supply power while maintaining phase synchronization with the AC grid based on the stable DC voltage.

[0084] Meanwhile, in the present embodiment, the control unit comprehensively controls the power flowing through each component, such as the first converter (30), the second converter (45), the third converter (50), the DC link, and the system load, included in the system, and manages the power so that it does not exceed the allowable capacity of each of the shaft generator (20), the fuel cell (40), and the third converter (50).

[0085] For example, if the power required from the system load increases and there is a concern that the power drawn into the AC system through the third converter (50) may exceed the rated capacity of the third converter (50), the control unit prevents operation exceeding the rated capacity by limiting the output power of the third converter (50).

[0086] In addition, the control unit monitors the operating status of the entire system in real time, and dynamically adjusts the output and distribution of each power converter to prevent abnormal conditions such as exceeding the rated power of the third converter (50), overpower of the fuel cell (40), and overdischarge of the DC link. At this time, the fuel cell (40) maintains constant output operation, and even if the power drawn from the DC link increases due to an increase in the system load, the output of the fuel cell (40) does not fluctuate. Accordingly, when the amount of power accumulated in the DC link is insufficient, the control unit can operate the shaft generator (PTO) to supply the insufficient power to the DC link, thereby maintaining the overall power supply and demand balance. In addition, the control unit can variably control the power generation amount of the shaft generator (20) so that the sum of the power generated by the shaft generator (20) and the power generated by the fuel cell (40) does not exceed the rated power of the third converter (50).

[0087]

[0088] In this embodiment, the shaft generator (20) can operate in a PTI mode in which it receives power from an external source and applies rotational force to the propulsion shaft. At this time, the power applied to the shaft generator (20) is supplied from a DC link, converted into AC power through a first converter (30), and transmitted to the shaft generator (20).

[0089] For stable operation of the system, the voltage of the DC link must be maintained at a constant reference value. Accordingly, when the voltage of the DC link falls below the reference value, the control unit suppresses the voltage drop by controlling the third converter (50) to draw power from an external AC system, convert it into direct current, and supply it to the DC link. On the other hand, when the DC link voltage rises, the control unit prevents the voltage increase by controlling the third converter (50) to draw power from the DC link and transmit it to the external AC system.

[0090] Accordingly, the DC link voltage is maintained constant, providing a stable power environment for PTI operation of the shaft generator.

[0091] In addition, in this embodiment, the control unit is configured to control the output torque of the shaft generator (20) by adjusting the power applied to the shaft generator (20) through the first converter (30). For example, when the control unit increases the output current of the first converter (30) while the voltage of the DC link is maintained constant, the power supplied to the shaft generator (20) increases, and accordingly, the output torque of the shaft generator (20) increases, so that the rotational force applied to the propulsion shaft increases. Conversely, when the control unit decreases the output current of the first converter (30), the power applied to the shaft generator (20) decreases, the output torque decreases, and the rotational force also decreases.

[0092] In this embodiment, the control unit controls the output current of the second converter (45) connected to the fuel cell (40) so that the fuel cell (40) operates at constant output. In addition, the control unit controls the operation of the second converter (45) in conjunction with the load status of the first converter (30) and the shaft generator (20), so that the constant output operation of the fuel cell (40) is stably maintained.

[0093] Meanwhile, in addition to the fuel cell (40), each component, such as the shaft generator (20), the first converter (30), and the third converter (50), has its own unique rated capacity. If any one of these operates in an overloaded state, system stability may be degraded or device damage may occur. To prevent this, the control unit dynamically controls the power required by the entire system so that it does not exceed the rated power of each device, taking into account the output and supplyable power amount of each device.

[0094] For example, the control unit combines and limits the power flowing in from the system and the power supplied to the fuel cell (40) so that the rated power of the first converter (30) is not exceeded. If the total required power increases while the constant output power of the fuel cell is maintained, the remaining power is supplied through the third converter (50), and distribution control is performed so that the amount of power to be processed on the first converter (30) side does not exceed the rated power.

[0095] In this way, by performing real-time load distribution so as not to exceed the rated power limit of the entire system while maintaining the constant power operation characteristics of the fuel cell, system stability and equipment protection can be achieved simultaneously.

[0096]

[0097] The ship propulsion system (1) according to the second embodiment of the present invention may differ from the previous embodiment in that the fuel cell (40) has a maximum output that is less than the minimum power demand of the system load required by the ship. Below, the differences between this embodiment and the previous embodiment will be described, and any omitted portions will be replaced with the previous content. This also applies to other embodiments below.

[0098] In this embodiment, the fuel cell (40) may have a maximum output that is less than the minimum power demand of the system load required by the vessel, for example, the power demand of the system load when the vessel is in port standby mode. Therefore, even when the fuel cell (40) is operated at maximum output, it cannot independently supply the entire power required for the system load in all operating modes of the vessel.

[0099] In this embodiment, the control unit can control the fuel cell (40) to always generate power at a constant power, for example, at maximum output, regardless of the ship's operating mode, and to supply auxiliary power to the shaft generator (20) by operating in PTO mode for the remaining power that is not satisfied even with the output of the fuel cell (40).

[0100] In this way, since power supply by the fuel cell (40) is always provided, the PTO capacity of the shaft generator (20) can be reduced at the design stage in consideration of the output of the fuel cell (40).

[0101] For example, if the power supply of the fuel cell (40) is not considered and the required PTO capacity of the shaft generator (20) is A [MW], in a structure where power of B [MW] is constantly supplied from the fuel cell (40), the shaft generator (20) can be designed with a capacity of (AB) [MW], so that the rated capacity of the generator and the corresponding first converter (30) can be reduced.

[0102] In addition, the control unit can control the power generated by the fuel cell (40) to be supplied preferentially to the auxiliary propulsion device when the ship uses an auxiliary propulsion device such as a wind-assisted propulsion system (WAPS) or an air lubrication system (ALS).

[0103] In this way, when the auxiliary propulsion device is driven, the output of the main engine (10) used for propulsion is reduced due to the propulsion assistance by the auxiliary propulsion device, thereby increasing the power output of the shaft generator (20), thereby expanding the power operation range.

[0104] Meanwhile, if the power demand of the system load cannot be met even with the power supplied by the fuel cell (40) and the power supplied by the shaft generator (20), the control unit can control the power generation unit (70) to supply the insufficient power.

[0105] According to this embodiment, since the fuel cell (40) with high operating efficiency operates at a constant output, the efficiency of the entire system is increased. In addition, since the system load is assisted by the fuel cell (40), the capacity restriction on the PTO operation of the shaft generator is relaxed, and since the operating frequency or operating time of the relatively low-efficiency power generation unit (70) is reduced, there is an effect of improving the energy efficiency of the entire system.

[0106] In addition, according to the present embodiment, by connecting the fuel cell (40) to the same DC link as the shaft generator (20), a portion of the power supplied to the system is shared by the fuel cell (40), so that the design capacity of the first converter (30) that supplies power from the shaft generator (20) to the DC link can be reduced, thereby reducing the component size and cost of the entire system.

[0107]

[0108] Fig. 2 is a conceptual diagram of a ship propulsion system (1) according to a third embodiment of the present invention. The ship propulsion system (1) according to the third embodiment of the present invention may be different from the previous embodiment in that it further includes a battery (80) and a fourth converter (85), and a control unit controls the power supply by the fuel cell (40) and the battery (80).

[0109] The battery (80) according to the present embodiment is charged by receiving power or discharges previously stored power. The battery (80) according to the present embodiment is connected to the same DC link as the shaft generator (20) and the fuel cell (40).

[0110] The fourth converter (85) is a DC / DC converter and is connected between the battery (80) and the DC link. The fourth converter (85) converts the power discharged by the battery (80) to a voltage that matches the voltage of the DC link and supplies it to the DC link, or converts the power supplied from the DC link and charges the battery (80). Through this, stable charging and discharging of the battery (80) is possible even if the terminal voltage of the battery (80) and the voltage of the DC link are different.

[0111] Accordingly, when the voltage of the DC link is higher than the terminal voltage of the battery (80), the battery (80) is charged by receiving power from the DC link, and when the voltage of the DC link is lower than the terminal voltage of the battery (80), the battery (80) is discharged and supplies power to the DC link. Therefore, the control unit maintains the power balance of the DC link by controlling the output of the shaft generator (20) and the fuel cell (40) or the operating state of the load, and thereby controls the voltage of the DC link to control the charging and discharging operation of the battery (80).

[0112] In this embodiment, the fuel cell (40) outputs constant power, and the control unit controls the charging and discharging operation of the battery (80) based on the amount of power generated by the shaft generator (20) or the amount of power supplied to the shaft generator (20).

[0113] For example, when the power generated by the shaft generator (20) and the fuel cell (40) and supplied to the DC link exceeds the power demand of the system load, surplus power is accumulated in the DC link, causing the voltage to rise. The control unit detects this rise in the DC link voltage and controls the fourth converter (85) to operate in a step-down mode to convert the power of the DC link to the charging voltage level of the battery (80) and supply it. Accordingly, current flows from the DC link toward the battery (80), and the battery (80) is charged.

[0114] On the other hand, if the power generated by the shaft generator (20) and the fuel cell (40) and supplied to the DC link falls short of the power demand of the system load, the remaining power of the DC link becomes insufficient, which causes the voltage of the DC link to decrease. The control unit detects this voltage drop and controls the fourth converter (85) to operate in boost mode to convert and supply the power of the battery (80) to a voltage higher than that of the DC link. Accordingly, current flows from the battery (80) toward the DC link, and the insufficient power is supplemented.

[0115] This also applies when power generated by the fuel cell (40) is supplied to the shaft generator (20). The control unit compares the amount of power that can be supplied to the system load with the power demand of the system load, and if the amount of power that can be supplied as a result of the comparison exceeds the power demand of the system load, the control unit controls the excess power to be stored in the battery (80), and conversely, if the amount is insufficient, the control unit controls the insufficient power to be discharged from the battery (80) and supplied to the DC link.

[0116] Meanwhile, the control unit according to the present embodiment can control the power generation unit (70) to supply the insufficient power by driving the power generation unit (70) when the power demand of the system load cannot be met even by discharging the battery.

[0117] In one embodiment of the present invention, the constant output of the fuel cell (40) may be smaller than the power demand of the system load in the cargo handling mode of the ship, and larger than the power demand of the system load in the normal seagoing and port in / out modes of the ship. In this case, the control unit may control the charging and discharging of the battery (80) based on the ship's operating mode.

[0118] For example, when the ship is operating in normal operation mode or in port entry or departure mode, the control unit can control the DC link voltage so that it is supplied to the system load and the remaining power is charged to the battery (80).

[0119] Meanwhile, when the vessel is operating in unloading operation mode, the control unit can control the DC link voltage to discharge the battery (80), thereby supplying the power supplied to the DC link by the fuel cell (40) and the battery (80) to the system load. In addition, when the discharge of the battery (80) is insufficient, the control unit can additionally control the power generation unit (70) to supply the insufficient power.

[0120] According to this embodiment, when using a fuel cell (40) whose output control is difficult, a battery (80) capable of charging and discharging power can be used together, thereby enabling flexible response to load fluctuations. In addition, since the battery (80) is connected to the same DC link as the shaft generator (20) and the fuel cell (40), charging and discharging of the battery (80) can be achieved with less conversion loss, thereby improving the efficiency of the entire system.

[0121]

[0122] Meanwhile, in this embodiment, the DC link is connected in parallel with the first converter (30) and the battery (80), and the control unit is configured to control the current supplied to the DC link from each of these power conversion devices so that the DC link voltage is maintained at a constant reference value.

[0123] In one embodiment of the present invention, when the shaft generator (20) operates in PTO mode, the control unit monitors the voltage status of the DC link in real time, and when the voltage rises or falls below a reference value, determines a current reference value for each device so that the current output of the first converter (30) and the fourth converter (85) is autonomously adjusted.

[0124] In this embodiment, the control unit can be configured to apply a droop control method to each power source so that the shaft generator (20) and battery (80) connected to the DC link autonomously share current according to the DC link voltage.

[0125] Droop control is based on the linear relationship between the voltage and current of the DC link, so that when the DC link voltage falls below a reference value, the current supplied by the power source increases, and conversely, when the DC link voltage rises above the reference value, the current decreases. Accordingly, the control unit automatically adjusts the current reference value according to a preset droop coefficient for each of the first converter (30) and the fourth converter (85), and allows more current to flow in or be absorbed as the deviation of the DC link voltage increases.

[0126] By this droop control, current sharing between the shaft generator (20) and the battery (80) is performed autonomously and stably, and the voltage of the DC link is maintained stably.

[0127] Meanwhile, in the present embodiment, the third converter (50) operates as an inverter that converts direct current power supplied from the DC link into alternating current power and supplies power to the AC grid. At this time, the control unit controls the modulation method (PWM), the magnitude of the output current, and the phase angle of the third converter (50) so as to be synchronized with the target voltage, frequency, and phase of the AC grid, thereby enabling stable power to be supplied to the AC grid under rated conditions.

[0128] In this embodiment, the control unit monitors the power flow of the entire system in real time and controls power distribution so as not to exceed the rated capacity of each component. In particular, the third converter (50) connected to the DC link is an inverter that transmits power to an external AC system. If its rated output power is exceeded, problems such as output voltage distortion, heat generation, and protection operation may occur. Therefore, the control unit performs load limit control to adjust the output level of each power source so as not to exceed the rated capacity of the third converter (50).

[0129] More specifically, the control unit comprehensively manages the output power of the fuel cell (40), shaft generator (20), battery (80), etc., so that the power drawn through the third converter (50) does not exceed certain standards (ratings).

[0130] For example, the control unit reduces the output power of the shaft generator (20) or the battery (80) while maintaining the output of the fuel cell (40), or controls the absorption of DC link power through the charging operation of the battery (80), thereby preventing the total amount of power applied to the third converter (50) from exceeding the rating. Conversely, when the output of the fuel cell (40) alone is insufficient, additional power is supplied within the remaining output range of the shaft generator (20) and the battery (80), thereby balancing the power supply and demand.

[0131] In this way, the control unit can perform stable power distribution control that satisfies the load limit of the entire system by flexibly adjusting the output power from the shaft generator (20) and the battery (80) within the allowable power range of the third converter (50) while assuming constant output operation of the fuel cell (40).

[0132] In addition, in this embodiment, the battery (80) is connected to the DC link and configured to perform a charging or discharging operation through the fourth converter (85) according to changes in the DC link voltage. The control unit monitors the DC link voltage in real time, and when the voltage rises or falls below a reference value, controls the fourth converter (85) so that the flow direction and size of the DC link current are adjusted, thereby preventing the DC link voltage from going beyond the reference range.

[0133] For example, if the total power supplied to the DC link through the fuel cell (40) and the shaft generator (20) exceeds the rated output power of the third converter (50), and surplus power is accumulated in the DC link, the DC link voltage rises above a reference value. At this time, the control unit controls the fourth converter (85) to allow current to flow from the DC link to the battery (80) to charge the battery (80), thereby suppressing the voltage increase of the DC link.

[0134] Conversely, if the power drawn through the third converter (50) exceeds the power supplied to the fuel cell (40) and the shaft generator (20) due to an increase in external system load, etc., the DC link power remaining amount becomes insufficient and the voltage drops. Accordingly, the control unit controls the fourth converter (85) to supply current from the battery (80) to the DC link, thereby discharging the battery (80) and recovering the DC link voltage.

[0135] In this way, in this embodiment, the control unit controls the charging or discharging operation of the battery (80) through the fourth converter (85) to be performed according to the DC link voltage status, thereby configuring the DC link voltage to be stably maintained within the reference value range, thereby improving the power supply and demand balance and voltage quality of the entire system.

[0136]

[0137] Meanwhile, in another embodiment of the present invention, when the shaft generator (20) operates in PTI mode, the power applied to the shaft generator (20) is converted and supplied by the first converter (30) through a DC link. The first converter (30) is a power conversion device that provides AC power to the shaft generator (20) and has a certain rated power capacity, so if it is exceeded, system damage or a protective operation may occur.

[0138] Accordingly, the control unit controls so that the sum of the power flowing into the DC link from each of the fuel cell (40), the third converter (50), and the fourth converter (85) connected to the DC link does not exceed the rated power of the first converter (30). At this time, since the fuel cell (40) has a constant power operation characteristic that continuously outputs a constant power, the control unit can manage the total power supply by maintaining the output of the fuel cell (40) at a fixed value and adjusting the current output of the third converter (50) and the fourth converter (85) that additionally supply power to the DC link.

[0139] More specifically, when the total power flowing into the DC link through the fuel cell (40), the third converter (50), and the fourth converter (85) exceeds the rated power of the first converter (30), the control unit can control the total DC link power not to exceed the allowable power of the first converter (30) by reducing the amount of power flowing into the third converter (50) that draws power from an external AC system or by limiting the discharge current of the fourth converter (85) to control the power discharged from the battery (80).

[0140] Conversely, when the rotational power demand of the shaft generator (20) increases and the power supply through the first converter (30) is insufficient, the control unit controls to draw in more power from the AC system through the third converter (50) or to discharge additional power from the battery (80) through the fourth converter (85) while maintaining the output of the fuel cell (40), thereby supplementing the insufficient remaining power.

[0141] At this time, the control unit applies a droop control method to the third converter (50) and the fourth converter (85) so that the current sharing between the AC system and the battery (80) is performed autonomously and stably.

[0142] In this embodiment, the control unit monitors the DC link voltage in real time, and when the voltage rises or falls below a reference value, controls the fourth converter (85) to perform a charging or discharging operation of the battery (80).

[0143] For example, when the total power supplied to the DC link through the fuel cell (40) and the third converter (50) exceeds the rated power of the first converter (30), surplus power is accumulated in the DC link, causing the voltage to rise. At this time, the control unit suppresses the voltage rise by allowing current to flow into the battery through the fourth converter (85) to charge the battery.

[0144] Conversely, if the power that the first converter (30) must supply to the shaft generator (20) is greater than the power that can be supplied from the fuel cell (40) and the third converter (50), the voltage drops due to a lack of DC link power, and at this time, the control unit controls the fourth converter (85) to supply current from the battery (80) to the DC link, thereby performing battery discharge.

[0145] This power supply operation corresponds to a control for stably supplying power corresponding to the rotational torque required for the shaft generator (20) to operate in PTI mode through the first converter (30). The control unit appropriately distributes and controls the outputs of the second converter (45), the third converter (50), and the fourth converter (85) so that the power level applied to the first converter (30) matches the torque demand of the shaft generator (20), thereby maintaining a stable torque operation state so that the rotational power required for the propulsion shaft is neither excessive nor insufficient.

[0146]

[0147] Fig. 3 is a conceptual diagram of a ship propulsion system (1) according to a fourth embodiment of the present invention. The ship propulsion system (1) according to the fourth embodiment of the present invention may be different from the previous embodiment in that it further includes an auxiliary propulsion device (90), and the control unit distributes and supplies power generated by the fuel cell (40) to a grid including a shaft generator (20) and the auxiliary propulsion device (90).

[0148] The auxiliary propulsion device (90) is a device that supplements the propulsion power of a ship by consuming power generated by a power source (e.g., a shaft generator (20), a power generation unit (70), etc.). 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 a ship using wind power, and an air lubrication system (ALS) that forms a microbubble layer on the bottom of the ship to reduce frictional resistance.

[0149] This auxiliary propulsion device (90) functions as a load that consumes power and at the same time assists the propulsion power, thereby indirectly reducing the operating load of the main engine (10). Meanwhile, the power consumption of this auxiliary propulsion device (90) (i.e., the amount of fuel used by the power generation source used to drive the auxiliary propulsion device (90)) and the amount of propulsion power assisted by the auxiliary propulsion device (90) may vary depending on various conditions such as sea conditions, wind speed, wind direction, ship's operating speed, and cargo loading.

[0150] In this embodiment, the control unit controls the power distribution to the grid and shaft generator (20) connected to the auxiliary propulsion unit (90) by considering the amount of fuel consumption reduction of the main engine (10) due to the operation of the auxiliary propulsion unit (90). Hereinafter, the operation of the control unit distributing the power generated by the fuel cell (40) will be specifically examined.

[0151] When power is generated by the fuel cell (40), the control unit first determines whether to drive the auxiliary propulsion device (90) based on the effect of the drive of the auxiliary propulsion device (90) on the overall propulsion efficiency of the ship.

[0152] As previously described, the auxiliary propulsion unit (90) can be driven by consuming at least a portion of the power generated by the power generation unit (70) or the shaft generator (20). Since the shaft generator (20) generates power by extracting at least a portion of the power generated from the main engine (10), when the auxiliary propulsion unit (90) is driven by the power generated by the shaft generator (20), the load of the shaft generator (20) increases, and accordingly, the load of the main engine (10) also increases, resulting in additional fuel consumption. When the auxiliary propulsion unit (90) is driven by the power generation unit (70), the power generation unit (70) also consumes additional fuel.

[0153] In this embodiment, the control unit determines the driving of the auxiliary propulsion device (90) by comparing the fuel consumption of the power generation source that will increase due to the driving of the auxiliary propulsion device (90) with the fuel consumption of the main engine (10) that will be reduced due to the propulsion power assisted by the auxiliary propulsion device (90).

[0154] At this time, in the case of devices that generate power by consuming fuel, such as the main engine (10) and the power generation unit (70), the amount of fuel consumed to produce a certain output (specific fuel consumption; SFC) differs depending on the output (i.e., the driving load). That is, since the fuel consumption efficiency of the main engine (10) and the power generation unit (70) differs depending on the respective outputs, the fuel consumption of the main engine (10) and the power generation source must be determined by considering the respective SFCs.

[0155] In another embodiment of the present invention, the control unit may predict the fuel consumption of each of the power source and the main engine (10) to be changed based on a lookup table that is set and stored in advance, without predicting the change in fuel consumption of the power source and the main engine (10) through calculation, and may determine whether to drive the auxiliary propulsion device (90).

[0156] 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.

[0157] More specifically, the control unit checks the amount of power required to drive the current auxiliary propulsion device (90), 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.

[0158] Thereafter, the fuel consumption required to drive the auxiliary propulsion device (90) is calculated using the power amount and fuel consumption coefficient of the power source required to drive the auxiliary propulsion device (90), and by comparing this with the fuel consumption of the main engine (10) saved by driving the auxiliary propulsion device (90), it is possible to determine whether to drive the auxiliary propulsion device (90).

[0159] 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 (90) and the fuel consumption of the main engine (10) that will decrease due to the operation of the auxiliary propulsion device (90) 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 (90) and the fuel consumption of the main engine (10) that will decrease due to the operation of the auxiliary propulsion device (90) in real time and determines whether to operate the auxiliary propulsion device (90).

[0160] If it is determined that the fuel consumption to be reduced of the main engine (10) is greater than the fuel consumption of the power source to be increased to drive the auxiliary propulsion device (90), the control unit supplies some of the power generated by the fuel cell (40) to the grid to which the auxiliary propulsion device (90) is connected to drive the auxiliary propulsion device (90) and supplies the remainder to the shaft generator (20) to control the shaft generator (20) to operate in PTI mode.

[0161] In this embodiment, other system loads other than the auxiliary propulsion device (90) may be connected to the grid to which the auxiliary propulsion device (90) is connected, and 'other system loads' hereinbelow may refer to other system loads connected to the grid other than the auxiliary propulsion device (90).

[0162] That is, when it is determined that the auxiliary propulsion device (90) satisfies the driving conditions, the control unit supplies power corresponding to the power demand of the auxiliary propulsion device (90) and other system loads among the output of the fuel cell (40) to the grid to which the auxiliary propulsion device (90) is connected, and supplies the remaining power to the shaft generator (20) so that the shaft generator (20) applies rotational force to the propulsion shaft.

[0163] 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 generator, i.e., if the driving conditions of the auxiliary propulsion device (90) are not satisfied, the control unit determines that the driving of the auxiliary propulsion device (90) lowers the overall efficiency of the system and controls the auxiliary propulsion device (90) not to be driven. In this case, the control unit supplies power corresponding to the power demand of other system loads among the output of the fuel cell (40) to the grid to which the auxiliary propulsion device (90) is connected, and supplies the remaining power to the shaft generator (20).

[0164] Meanwhile, when the auxiliary propulsion device (90) is driven, the speed of the ship changes due to the propulsion assistance of the auxiliary propulsion device (90). 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 (90) driven and the target speed of the ship.

[0165] The control unit monitors the current speed of the vessel and the target speed of the vessel while the auxiliary propulsion device (90) is operating. If the monitoring results show that the vessel's speed falls short of the target speed even though the auxiliary propulsion device (90) 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.

[0166] On the other hand, if the monitoring results show that the auxiliary propulsion device (90) 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.

[0167] However, exceptionally, when the output of the main engine (10) is required to exceed a certain level to secure the target speed, the increase in output by the control unit may deviate from the optimal efficiency operating conditions of the main engine (10), resulting in a decrease in fuel efficiency, or the increase in output itself may be limited due to the mechanical limitations of the engine.

[0168] In this way, if it is inefficient or impossible to increase the output of the main engine (10) beyond a certain level, the control unit can preferentially distribute the power generated by the fuel cell (40) to the shaft generator (20).

[0169] More specifically, the control unit may preferentially distribute the power required for the PTI operation of the shaft generator (20) to supplement the insufficient propulsion power that cannot be satisfied by the main engine (10), and supply the remaining power to the grid to which the auxiliary propulsion unit (90) is connected. In this case, depending on the amount of remaining power supplied to the grid, only a part of the auxiliary propulsion unit (90) may be driven, or the entire drive may not be possible, and the power supplied to the auxiliary propulsion unit (90) may be reduced. That is, the distribution ratio of the power transmitted from the fuel cell (40) to the grid or the shaft generator (20) may be considered as the operating condition of the auxiliary propulsion unit (90). For example, the maximum power that the auxiliary propulsion unit (90) can consume may be reflected as a control variable and considered as the operating condition of the auxiliary propulsion unit (90).

[0170] According to the present embodiment, the control unit first determines whether to operate the auxiliary propulsion device (90) by considering the amount of fuel consumption reduction of the main engine (10), and, depending on whether the auxiliary propulsion device (90) is operated, the output of the fuel cell (40) is preferentially supplied to the grid to which the auxiliary propulsion device (90) is connected, and the remaining residual power is supplied to the shaft generator (20). Accordingly, the utilization of the auxiliary propulsion device (90) based on the fuel cell (40) can be maximized.

[0171]

[0172] Fig. 4 is a conceptual diagram of a ship propulsion system (1) according to a fifth embodiment of the present invention. The ship propulsion system (1) according to the fifth embodiment of the present invention is different from the previous embodiment in that the auxiliary propulsion device (90), the shaft generator (20), the fuel cell (40), and the battery (80) are electrically connected to a common DC link. At this time, the DC link is not simply a wiring structure that transmits power between each device, but can function as a common DC power grid, i.e., a DC grid, in which a plurality of power conversion devices and loads are interconnected to share power.

[0173] In the present embodiment, the fuel cell (40) is configured to be constantly operated at a constant output, and the control unit controls the power generated by the fuel cell (40) to be preferentially supplied to a load driven by a VFD (Variable Frequency Drive) connected to a DC link (i.e., a VFD load), such as an auxiliary propulsion device (90). In the present embodiment, the auxiliary propulsion device (90) includes at least one of an air lubrication system (ALS) and a wind-assisted propulsion system (WAPS), and in the case of an air lubrication system, a compressor that compresses air to high pressure may be connected to the DC link.

[0174] Accordingly, only the power excluding the power consumed by the VFD loads among the output power of the fuel cell (40) is supplied to the shaft generator (20) through the first converter (30) or to the external AC system through the third converter (50).

[0175] Accordingly, the control unit can control the power processing capacity of the first converter (30) and the third converter (50) to be limited within the residual power range of the fuel cell, so that the rated capacity of the first converter (30) and the third converter (50) can be designed to be relatively small, and the cost and installation space of the system can be reduced.

[0176] More specifically, the rated capacity of the first converter (30) and the third converter (50) can be set to be less than the residual power obtained by subtracting the maximum power demand of the VFD loads from the rated output power of the fuel cell (40).

[0177] In another embodiment of the present invention, when the power generated by the fuel cell satisfies the power demand of the VFD loads, the control unit can control the fourth converter (85) so that the remaining power is supplied to the VFD loads and the battery (80) is charged. On the other hand, when the power generated by the fuel cell falls short of the power demand of the VFD loads, the control unit can control the fourth converter (85) to discharge the battery (80) so that the insufficient power is supplemented from the battery (80).

[0178] In this way, the control unit supplies the power generated by the fuel cell (40) to the VFD load with priority, and charges the remaining power to the battery (80) or supplements the insufficient power from the battery (80), thereby enabling efficient use of energy resources and stable operation of the VFD load.

[0179]

[0180] Fig. 5 is a conceptual diagram of a ship propulsion system (1) according to a sixth embodiment of the present invention. The ship propulsion system (1) according to the sixth embodiment differs from the previous embodiments in that the fuel cell (40) is described in detail as a fuel cell module unit.

[0181] Referring to FIG. 5, in the ship propulsion system (1) according to the sixth embodiment, the fuel cell (40) includes a plurality of fuel cell modules (401), a plurality of converters (451) each provided corresponding to each fuel cell module (401), a switching circuit (41) provided between the plurality of fuel cell modules (401) and the plurality of converters (451), and a control unit that controls the switching circuit.

[0182] Each fuel cell module (401) includes a plurality of fuel cell cells, which can be connected in parallel with each other.

[0183] Each converter (451) is provided corresponding to each fuel cell module (401) and converts the DC power generated by each fuel cell module (401) and supplies it to the distribution board. More specifically, each converter (451) is a DC / DC converter and converts the DC power output by the corresponding fuel cell (40) into a stable DC voltage and supplies it to the DC bus. That is, each converter (451) is connected to one fuel cell module (401) in a state in which the switching circuit (41) described below does not exist or in a state in which all switches (412) of the switching circuit (41) are open, and at this time, each converter (451) and each fuel cell module (401) correspond to each other.

[0184] A switching circuit (41) is provided between each fuel cell module (401) and a converter (451) corresponding to each fuel cell module (401), and connects each fuel cell module (401) to at least one converter selected from among a plurality of converters (451). That is, the switching circuit (41) can form a power supply path so that power generated by each fuel cell module (401) can be supplied not only to the converter (451) corresponding to the fuel cell module (401), but also to other converters (451).

[0185] In this embodiment, the switching circuit (41) may include a circuit (411) through which current can flow, a switch (412) that connects or blocks a path by an opening and closing operation, and a diode (413) for preventing reverse current due to a voltage difference.

[0186] The control unit controls the switching circuit (41) so that the power generated by each fuel cell module (401) is supplied to the determined converter (451). In this embodiment, the control unit can detect an abnormal state inside the fuel cell (40) through a current voltage sensor. For example, the control unit can detect an abnormal state of each converter (451) by monitoring changes in the input current and voltage of each converter (451) using a current sensor and a voltage sensor installed at the input terminal of each converter (451).

[0187] In this embodiment, when all of the plurality of converters (451) are operating normally, the control unit controls the switching circuit so that the power generated by each fuel cell module (401) is supplied to each corresponding converter (451). The switching circuit (41) at this time is as illustrated in Fig. 5. That is, the control unit controls so that the power generated by each fuel cell (40) is supplied one-to-one to the corresponding converter (451) by opening all the switches of the switching circuit (41).

[0188] Meanwhile, if it is determined that at least some of the plurality of converters (451) are faulty, the control unit stops the faulty converter (451) and the corresponding fuel cell module (401). At this time, even if the operation of the fuel cell module (401) is stopped, the hydrogen supplied before the stop may not react and remain inside the fuel cell module (401). Therefore, the control unit controls the switching circuit (41) to connect the fuel cell module (401) corresponding to the faulty converter (451) with another converter (451) that is operating normally, thereby enabling power generation using the residual hydrogen remaining in the fuel cell module (401), and supplying the generated power to another converter (451) that is operating normally.

[0189] In an embodiment of the present invention, if it is determined that one of the converters (451) is faulty, the control unit can control the switch (412) of the switching circuit (41) so that the fuel cell module (401) corresponding to the faulty converter (451) is connected to one of the converters (451) located in the path with the lowest resistance in the power wiring path among the remaining normally operating converters (451). Accordingly, loss during the power transmission process is minimized, unnecessary heat generation is prevented, and thermal stress on the switching element and wiring configuration is reduced.

[0190] In this embodiment, if there are multiple converters among the normally operating converters located on the path with the smallest resistance in the power wiring path from the faulty converter (451), the control unit can control the switch (412) of the switching circuit (41) to preferentially select the converter (451) with the largest remaining capacity among the converters so that the fuel cell module (401) corresponding to the faulty converter (451) is connected to the corresponding converter (451).

[0191] If the remaining capacity is the same, the stability of the system and the efficiency of power flow can be improved by determining the converter (451) to be bypassed by additionally considering the preset priority or the thermal condition of the converter.

[0192] A plurality of converters (451) according to the present embodiment are connected in parallel with each other, and each of the converters (451) connected in parallel performs a current control function, so that each converter (451) can autonomously consume the output of the fuel cell module (401) without a separate command from the control unit.

[0193] Accordingly, the converter (451) that receives power from the fuel cell module (401) that does not respond by the control of the switching circuit (41) of the control unit accepts the current flowing in from the fuel cell module (401) according to its own current control function. At this time, the hydrogen remaining inside the fuel cell module (401) can be naturally consumed through an electrochemical reaction, and the converter (451) can control the consumption speed and consumption time of the remaining hydrogen by adjusting the input current.

[0194] In this embodiment, the control unit controls the switching circuit (41) so that the fuel cell module (401) corresponding to the faulty converter (451) is electrically connected to another normally operating converter (451), thereby allowing the residual hydrogen inside the corresponding fuel cell module (401) to be converted into electricity through an electrochemical reaction via the normally operating converter (451).

[0195] In this case, the converter (451) in normal operation will receive more instantaneous current than usual, and thus output a relatively large instantaneous power. Therefore, in the ship propulsion system (1) according to the present embodiment, each converter (451) can be designed to have sufficient instantaneous input capacity so that it can stably receive not only the power of its own corresponding fuel cell module (401), but also additional instantaneous power generated by other fuel cell modules (401).

[0196] The control unit opens all switching circuits (41) to block the bypass circuit when the output voltage of the stopped fuel cell module (401) falls below the reference voltage as a result of monitoring the current sensor and voltage sensor installed at the output terminal of each fuel cell module (401).

[0197] Meanwhile, in another embodiment of the present invention, when an abnormal state of one converter (451) is detected, the control unit may, depending on the situation, stop the operation of only the converter (451) in which the abnormality is detected, and allow the corresponding fuel cell module (401) to operate normally. In this case, the control unit may control the switching circuit (41) to connect the fuel cell module (401) corresponding to the faulty converter (451) to another normally operating converter (451), thereby allowing the power generated by the fuel cell module (401) corresponding to the faulty converter (451) to be converted and supplied through the other normally operating converter (451).

[0198] According to the present embodiment, the control unit controls the switching circuit (41) so that the fuel cell module connected to the faulty converter (451) is electrically connected to another converter (451) that is operating normally. Accordingly, even when the output of the fuel cell module (401) is cut off due to the faulty converter (451), the hydrogen remaining in the fuel cell module (401) can be converted into electric power and output through the normally operating converter (451), thereby protecting the fuel cell module (401) when a fault occurs, while improving the energy utilization of the entire system.

[0199]

[0200] Below, with reference to FIG. 6, the control operation of the control unit when the converter (451) fails will be examined in more detail.

[0201] FIG. 6 shows a ship propulsion system (1) having a total of four fuel cell modules (401a, 401b, 401c, 401d) from the first fuel cell module (401a) to the fourth fuel cell module (401d), and four converters (451a, 451b, 451c, 451d) corresponding to each fuel cell module (401a, 401b, 401c, 401d).

[0202] The control unit can detect an abnormal state of the converter (451a) by monitoring the current sensor and voltage sensor provided at the input terminal of each converter (451a, 451b, 451c, 451d). The control unit that detects the abnormal state of the converter (451a) stops the operation of the converter (451a) and the first fuel cell module (401a), and then closes only the first switch (412a) connecting between the converter (451a) and the converter (451b), and opens all the remaining switches (412b, 412c, 412d), thereby connecting the first fuel cell module (401a) and the converter (451b). Accordingly, the power generated by the residual hydrogen of the first fuel cell module (401a) is output to the outside through the converter (451b).

[0203] Thereafter, when the voltage of the output terminal of the first fuel cell module (401a) is lower than the reference voltage, the control unit opens the first switch (412a) of the switching circuit (41) to block the path to the converter (451b).

[0204]

[0205] Fig. 7 is a conceptual diagram of a ship propulsion system (1) according to a seventh embodiment of the present invention. The ship propulsion system (1) according to the seventh embodiment differs from the previous embodiments in that it includes two independent propulsion units (1a, 1b) and a switch (43) provided between the two propulsion units (1a, 1b). Referring to Fig. 7, each propulsion unit (1a, 1b) includes a main engine (10), a shaft generator (20), a first converter (30), a fuel cell (40), a second converter (45), and a third converter (50).

[0206] The main engine (10) is connected to a propeller installed at the stern through a propeller shaft, and the rotational power generated from the main engine is transmitted to the propeller through the propeller shaft to propel the ship.

[0207] The shaft generator (20) can generate electric power by extracting at least a portion of the power generated by the main engine (10), or can assist the propulsion power of the main engine (10) by receiving electric power from an external source and rotating the propulsion shaft.

[0208] In this embodiment, the two propulsion units (1a, 1b) are connected to each other through a switch, i.e., the main switch board, and the AC grid, so that, depending on the closing of the switch, the two propulsion units can perform mutual power sharing or grid-connected operation through the main switch board.

[0209] A switching circuit (42) is provided between two propulsion units (1a, 1b) and connects the fuel cell (40) of one propulsion unit to the second converter (45) of the other propulsion unit connected in parallel. That is, the switching circuit (42) can form a power supply path so that the power generated by each fuel cell (40) can be supplied not only to the second converter (45) of the propulsion unit to which the fuel cell (40) belongs, but also to the second converter (45) of another propulsion unit.

[0210] In this embodiment, the switching circuit (42) may include a circuit through which current can flow, a switch (421a, 421b) that connects or blocks a path by an opening and closing operation, and a diode for preventing reverse current due to a voltage difference.

[0211] In this embodiment, the control unit can detect an abnormal state of each converter (30, 45, 50) by monitoring a plurality of current sensors and voltage sensors provided within the system. In this embodiment, a current sensor and a voltage sensor may be provided at the input terminal of each converter (30, 45, 50), and the control unit can detect an abnormal state of each converter (30, 45, 50) by monitoring these current sensors and voltage sensors.

[0212] In this embodiment, if an abnormal condition of the second converter (45) of one propulsion unit is detected, or if it is determined that the power generated by the fuel cell (40) cannot be supplied to the DC link or is inappropriate due to an abnormality in the DC link, the control unit stops the operation of the fuel cell (40) of one propulsion unit and the second converter (45).

[0213] Thereafter, the control unit controls the switching circuit (42) to connect the fuel cell (40) of one propulsion unit and the second converter (45) of the other propulsion unit. Accordingly, the hydrogen remaining in the fuel cell (40) of one propulsion unit is converted into electric power through the second converter (45) of the other propulsion unit and supplied to the DC link, so that even if a problem occurs in the second converter (45) or the DC link, the remaining hydrogen in the fuel cell (40) can be stably processed.

[0214] Afterwards, when the input voltage of the faulty second converter (45) falls below the reference voltage, the control unit opens all switching circuits (42) to block the bypass path.

[0215] In this embodiment, as the remaining hydrogen of the fuel cell (40) of one propulsion unit is converted into electric power through the second converter (45) of the other propulsion unit by the control of the switching circuit (42) of the control unit, the second converter (45) of the other propulsion unit receives more current than usual, thereby outputting relatively large electric power. Therefore, in the ship propulsion system (1) according to this embodiment, each converter (30, 45, 50) must be designed to have sufficient input allowable capacity so that each converter (30, 45, 50) can receive instantaneous power generated by the fuel cell (40) of the other propulsion unit in addition to the corresponding fuel cell (40).

[0216] According to the present embodiment, the control unit controls the switching circuit (42) to connect the fuel cell (40) to the second converter (45) of the other propulsion unit when a failure occurs in the second converter (45) of one propulsion unit or an abnormal state occurs in the DC link. Accordingly, even when the operation of the fuel cell (40) is stopped due to a failed second converter (45), the hydrogen remaining in the fuel cell (40) can be converted into electric power and output through the normally operating second converter (45), thereby protecting the fuel cell (40) when a failure occurs, while improving the energy utilization of the entire system.

[0217] Meanwhile, in the present embodiment, when a short circuit fault occurs in the DC link of one propulsion unit, the control unit can control the system to cut off the power supply to the VFD so that the VFD can perform a self-protection operation, or so that the protection operation of the VFD that has recognized the abnormal state can be performed effectively.

[0218]

[0219] Hereinafter, with reference to FIG. 8, the control operation of the control unit in the event of an abnormality in the second converter (30) or DC link of one propulsion unit will be examined in more detail.

[0220] When the control unit detects an abnormality in the second converter (30a) of the first propulsion unit (1a), it closes only the first switch (421a) among the open first switch (421a) and second switch (421b) of the switching circuit (42) and maintains the second switch (421b) in an open state, thereby controlling the connection of the fuel cell (40a) of the first propulsion unit (1a) and the second converter (45b) of the second propulsion unit (1b). Accordingly, the remaining hydrogen of the fuel cell (40a) of the first propulsion unit (1a) is converted into electric power through the second converter (45b) of the second propulsion unit (1b).

[0221] Thereafter, when the voltage at the input terminal of the second converter (45a) of the first propulsion unit (1a) is lower than the reference voltage, the control unit opens the first switch (421a) of the switching circuit (42) to block the path to the second converter (45a) of the second propulsion unit (1b). Accordingly, after the supply of residual hydrogen is terminated, unnecessary power flow is blocked, thereby ensuring system safety.

[0222]

[0223] Fig. 9 is a schematic diagram of a ship propulsion system according to an eighth embodiment of the present invention. The ship propulsion system (1) according to the eighth embodiment of the present invention differs from the previous embodiment in that the DC links of each of the two independent propulsion units (1a, 1b) are configured to be selectively connected via a switch (43). Accordingly, when the switch (43) is closed, the DC links of the two propulsion units (1a, 1b) are interconnected, enabling power sharing or grid-connected operation.

[0224] In this embodiment, the control unit can detect an abnormal state of each converter (30, 45, 50) by monitoring the current sensor and voltage sensor provided at the input / output terminal of each converter (30, 45, 50). If the control unit detects an abnormal state of at least one of the first converter (30) and the third converter (50) of one propulsion unit as a result of monitoring the current sensor and the voltage sensor, the control unit stops the operation of the converter in which a failure is detected.

[0225] Thereafter, the control unit distributes the power generated by the fuel cell (40) based on the failure status of the converter of one propulsion unit. Specifically, the control unit performs switch (43) control and power distribution based on which converter of one propulsion unit is faulty.

[0226] When distributing power, the control unit can refer to the rated input power or rated current that each converter (30, 45, 50) can accept based on a previously stored reference value, and perform distribution control so that the power generated by the fuel cell (40) is not excessively concentrated in a specific converter (30, 45, 50).

[0227] For example, if the power generated from the fuel cell (40) must be distributed to other converters that are operating normally, the control unit can comprehensively consider the current input status, rated allowance, thermal margin status, etc. of each converter (30, 45, 50) that is operating normally, and determine the power supply path so that the power is distributed and supplied to one or more converters (30, 45, 50).

[0228] At this time, if there is a concern that the rating of a specific converter (30, 45, 50) may be exceeded, power transmission to the relevant path can be restricted or the distribution ratio can be adjusted to other converters (30, 45, 50) according to priority, thereby preventing system overload and converter damage. According to this rating-based distribution control, the output power of the fuel cell (40) can be stably distributed to multiple converters, thereby maintaining the energy utilization efficiency and operational stability of the system even in a failure situation.

[0229] Meanwhile, if the load ratio is not recovered even after distributing power and a certain amount of time has passed, the control unit can stably stop the fuel cell by stopping the operation of the fuel cell (40) of one propulsion unit including the faulty converter (30, 45, 50).

[0230] According to this embodiment, even when the first converter (30) or the third converter (50) fails, the fuel cell is not suddenly stopped, but power is continuously supplied through a bypass path, thereby ensuring system stability and minimizing the reduction in the lifespan of the fuel cell and energy loss.

[0231]

[0232] Fig. 10 is a diagram schematically illustrating the control and power transfer path of the control unit when an abnormal condition of the third converter (50a) of the first propulsion unit (1a) is detected in the eighth embodiment. Referring to Fig. 10, when an abnormal condition of the third converter (50a) of the first propulsion unit (1a) is detected, the control unit stops the operation of the third converter (50a).

[0233] Thereafter, the control unit electrically connects the DC links of the first propulsion unit (1a) and the second propulsion unit (1b) to each other by closing the switch (43) provided between the DC links of the two propulsion units. Accordingly, the power generated by the fuel cell (40a) of the first propulsion unit (1a) is distributed to the first converter (30a) of the first propulsion unit (1a) and the DC link of the second propulsion unit (1b).

[0234] Meanwhile, if a sufficient load ratio to accommodate the power output by the fuel cell (40a) of the first propulsion unit (1a) is not recovered even after a certain period of time has passed since the power was distributed, the control unit can stably stop the fuel cell by stopping the operation of the fuel cell (40a) of the first propulsion unit (1a).

[0235] According to this embodiment, the power generated from the fuel cell (40a) of the first propulsion unit (1a) is supplied to the shaft generator (20a) of the first propulsion unit (1a) to perform PTI (Power Take-In) operation, and can also be supplied to the load or shaft generator (20b) of the second propulsion unit (1b), so that the output of the fuel cell (40a) of the first propulsion unit (1a) can be stably utilized even in a failure situation of the third converter (50a) of the first propulsion unit (1a).

[0236]

[0237] Fig. 11 is a diagram schematically illustrating the control and power transfer path of the control unit when an abnormal condition of the first converter (30a) of the first propulsion unit (1a) is detected in the eighth embodiment. Referring to Fig. 11, when an abnormal condition of the first converter (30a) of the first propulsion unit (1a) is detected, the control unit stops the operation of the first converter (30a).

[0238] Thereafter, the control unit controls the power generated by the fuel cell (40a) of the first propulsion unit (1a) to be converted through the third converter (50a) and supplied to the AC grid of the first propulsion unit (1a).

[0239] Meanwhile, even if the power generated by the fuel cell (40a) of the first propulsion unit (1a) is supplied to the AC system of the first propulsion unit (1a) through the third converter (50a), a portion of the output of the fuel cell (40a) may not be received due to insufficient system load. In this case, the control unit can control the remaining power among the output of the fuel cell (40a) of the first propulsion unit (1a) to be directly distributed to the DC link of the second propulsion unit (1b) by closing the switch (43) between the DC links of the two propulsion units.

[0240] Through this, the energy output of the fuel cell is effectively utilized, energy loss is reduced, and stable operation of the fuel cell is maintained.

[0241] Meanwhile, if a sufficient load ratio to accommodate the power output by the fuel cell (40a) of the first propulsion unit (1a) is not recovered even after a certain period of time has passed since the power was distributed, the control unit can stably stop the fuel cell by stopping the operation of the fuel cell (40a) of the first propulsion unit (1a).

[0242]

[0243] The present invention encompasses all embodiments resulting from a combination of the above embodiments and known techniques, in addition to the embodiments described above.

[0244] 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.

[0245] 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 shaft generator that generates power by utilizing the rotational force of a propulsion shaft or receives power from an external source and applies rotational force to the propulsion shaft; A fuel cell capable of outputting power exceeding the power demand of the system load required during normal seagoing of the ship; and It includes a control unit that controls the power supply to the above system load and the shaft generator, The above control unit A ship propulsion system that controls the supply of power generated by the fuel cell to the system load and the shaft generator based on the operation mode of the ship.

2. In paragraph 1, The above control unit A ship propulsion system that controls power supplied by the fuel cell to be supplied to the system load with priority when the ship is operating in normal operation mode, and the remaining power supplied to the system load to be supplied to the shaft generator.

3. In paragraph 1, It further includes a power generation unit that consumes fuel to supply electricity, The above control unit A ship propulsion system that controls the power generation unit to supply the insufficient power by driving the power generation unit when the ship is operating in loading mode or unloading mode and the power supplied by the fuel cell is less than the power demand of the system load required in the loading mode or unloading mode.

4. In paragraph 3, The above control unit A ship propulsion system that controls the supply of power generated by the fuel cell based on the power demand of the system load when the ship is operating in port in / out mode.

5. In paragraph 4, The above control unit A ship propulsion system that supplies all power generated by the fuel cell to the system load and controls the power generation unit to supply the remaining power when the ship is operating in port entry / exit mode and the power demand of the system load is greater than the maximum output of the fuel cell.

6. In paragraph 4, The above control unit A ship propulsion system that, when the ship is operating in port entry / exit mode and the power demand of the system load is less than the maximum output of the fuel cell, controls the power generated by the fuel cell to be supplied to the system load with priority and the remaining power to be supplied to the shaft generator to assist propulsion.

7. In paragraph 3, The above fuel cells are equipped with two, The above control unit A ship propulsion system that controls the power supply of the fuel cell and the power generation unit based on the system efficiency according to the use of the fuel cell and the power generation unit when the ship is operating in the entry / exit mode, the output of each fuel cell is less than the power demand of the system load, and the total output of the two fuel cells exceeds the power demand of the system load.

8. In paragraph 7, The above control unit, The above vessel is operating in port entry / exit mode, A ship propulsion system in which the system efficiency is calculated when power is supplied to the system load using the two fuel cells and the remaining power is supplied to the shaft generator to assist propulsion, and the system efficiency is calculated when power is supplied to the system load using one of the fuel cells and the shortfall is generated and supplied by the power generation unit, and the fuel cell and the power generation unit control the power supply in a manner that has a higher system efficiency.

9. In paragraph 4, The above control unit A ship propulsion system that controls the fuel cell to stop generating power and to supply power by operating only the power generation unit while the ship is operating in harbor idle mode.

10. In paragraph 1, A ship propulsion system in which the above-mentioned shaft generator and the above-mentioned fuel cell are connected to each other by the same DC link (DC-link).

11. In paragraph 10, Further comprising a converter that converts the DC power output by the fuel cell into the DC link voltage and supplies it to the DC link, The above control unit A ship propulsion system that controls the fuel cell to operate at constant output by controlling the output current of the converter.

12. A shaft generator that generates power by utilizing the rotational force of a propulsion shaft or receives power from an external source and applies rotational force to the propulsion shaft; A fuel cell capable of outputting power exceeding the power demand of the system load required during normal seagoing of the ship; and It includes a control unit that controls the power supply to the above system load and the shaft generator, The above control unit A ship propulsion system that controls the supply of power generated by the fuel cell to the system load and the shaft generator based on whether rotational power is applied by the shaft generator and the size of the power demand of the system load.

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