WO2026010449A1 - Ship propulsion system - Google Patents

Abstract

The present invention relates to a ship propulsion system wherein, when a change in the output of a main engine occurs or is expected, a controller variably controls the power withdrawal force of a shaft generator in a direction in which the change in the output of the main engine is counterbalanced, thereby maintaining the output of the main engine to be smooth, and the main engine's fuel efficiency and power supply stability engine can thus be improved.

Description

ship propulsion system

The present invention relates to a ship propulsion system.

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

Meanwhile, when the main engine uses a two-stroke direct-drive propulsion system, its structural characteristics tend to cause periodic fluctuations in output. Furthermore, the load detected by the main engine fluctuates constantly due to various external conditions, such as changes in sea conditions, sudden changes in the ship's system load, and the operation of auxiliary propulsion systems. This further amplifies output fluctuations. These output fluctuations can lead to uneven fuel injection and shift engine operating conditions away from optimal conditions, ultimately reducing fuel efficiency.

The purpose of the present invention is to provide a ship propulsion system that improves the overall efficiency of the ship propulsion and power system. The objectives of the present invention are not limited to those mentioned above, and other unmentioned objectives will be clearly understood by those of ordinary skill in the art from the description below.

A ship propulsion system according to one aspect of the present invention comprises: a main engine connected to a propulsion unit through a propulsion shaft and generating propulsion power for the ship; a shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; and a control unit controlling a power output amount of the shaft generator, wherein the control unit variably controls the power output amount of the shaft generator to offset the output fluctuation of the main engine when a fluctuation in the output of the main engine occurs or is expected.

The control unit can offset the output fluctuation of the main engine by increasing the load of the shaft generator when the output of the main engine is reduced or is expected to be reduced, and can offset the output fluctuation of the main engine by reducing the load of the shaft generator when the output of the main engine is increased or is expected to be increased.

The ship further includes a battery that stores at least a portion of the power generated from the shaft generator or discharges the stored power, and the control unit controls the battery to supply the stored power to the system load of the ship or to store at least a portion of the power generated by the shaft generator in response to a change in the power output of the shaft generator, thereby covering the difference between the power generated by the shaft generator and the power required by the system load.

The ship further includes a generator engine that supplies power to the system load, and the control unit controls the power supplied by the generator engine in response to a change in the power output of the shaft generator, thereby covering the difference between the power generated by the shaft generator and the power required by the system load.

A battery for storing at least a portion of the power generated from the shaft generator or discharging the stored power; and a generator engine for supplying power to the system load of the ship, wherein the control unit controls at least one of the battery and the generator engine in response to a change in the power output of the shaft generator, thereby covering the difference between the power generated by the shaft generator and the power required by the system load.

The control unit can cover the difference between the amount of power generated by the shaft generator and the power required by the system load by storing surplus power excluding the power required by the system load in the battery when the amount of power generated by the shaft generator is greater than the power required by the system load according to the variable control of the shaft generator, and by causing the battery to discharge the power already stored or the generator engine to produce power when the amount of power generated by the shaft generator is less than the power required by the system load.

The control unit can select a power source to supply power to the system load preferentially among the battery and the generator engine based on the state of charge of the battery.

The control unit may control the battery to preferentially discharge stored power when the state of charge of the battery is higher than a predetermined threshold value, and may control the generator engine to produce power when the state of charge of the battery is lower than the predetermined threshold value.

The control unit extracts a torque fluctuation component corresponding to a target band based on the torque applied to the propulsion shaft, and adjusts the load of the shaft generator to offset the extracted torque fluctuation component, thereby variably controlling the power output of the shaft generator in a direction that offsets the output fluctuation of the main engine.

The torque applied to the propulsion shaft reflects the output fluctuation of the main engine, and the output fluctuation of the main engine may be caused by at least one of a fluctuation in the system load of the ship, a fluctuation due to the sea conditions, and a fluctuation generated by the main engine itself.

According to another aspect of the present invention, a ship propulsion system includes a main engine that generates propulsion power for the ship; a shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; and a control unit that controls a load of the shaft generator, wherein the control unit can variably control the load of the shaft generator to offset a change in the output of the main engine when a change in the output of the main engine occurs or is expected.

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

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

Figure 2 is a drawing showing the output and fuel consumption of the main engine illustrated in Figure 1.

Figure 3 is a schematic diagram of a ship propulsion system according to a second embodiment of the present invention.

Figure 4 is a schematic diagram of a ship propulsion system according to a third embodiment of the present invention.

Figure 5 is a schematic diagram of a ship propulsion system according to a fourth embodiment of the present invention.

Figure 6 is a schematic diagram of a ship propulsion system according to a fifth embodiment of the present invention.

Figure 7 is a schematic diagram of a ship propulsion system according to a sixth embodiment of the present invention.

Fig. 8 is a graph showing the output of the main engine of the ship propulsion system of Fig. 3.

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.

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.

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

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.

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

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.

Referring to FIG. 1, a ship propulsion system (1) according to a first embodiment of the present invention includes a main engine (10), a shaft generator (20), a first converter (30), a second converter (40), and a control unit (50).

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

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

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

Referring to Fig. 2, which shows the variation in output and fuel consumption of the main engine (10), it can be confirmed that the variation in output and fuel consumption of the main engine (10) occurs over time in both cases where power extraction by the shaft generator (20) does not occur (Fig. 2a) and where power extraction by the shaft generator (20) occurs (Fig. 2b).

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

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

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

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

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

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

The control unit (50) variably controls the power output of the shaft generator (20). In the present embodiment, the control unit (50) can variably control the power output of the shaft generator (20) by adjusting the load of the shaft generator (20). When a change in the output of the main engine (10) occurs or is expected to occur, the control unit (50) can control the output of the main engine (10) to be maintained more smoothly by adjusting the load of the shaft generator (20) in a direction that offsets the change in the output of the main engine (10).

More specifically, the control unit (50) can control the output of the main engine (10) to be maintained constant by increasing the load of the shaft generator (20) to increase the output of the main engine (10) when the output of the main engine (10) is reduced or is expected to be reduced. Meanwhile, the control unit (50) can control the output of the main engine (10) to be maintained constant by decreasing the load of the shaft generator (20) to decrease the output of the main engine (10) when the output of the main engine (10) is increased or is expected to be increased.

In this embodiment, the control unit (50) sets a target output level based on an average output value or an RMS (root mean square) output value, etc., for overall output smoothing, and controls the main engine (10) to compensate for output in the low-frequency band and the shaft generator (20) to compensate for output fluctuations in the high-frequency band, thereby enabling smoothing of the overall output.

In this embodiment, the control unit (50) can adjust the load of the shaft generator (20) by changing the current control value of the first converter (30) and the current command value of the second converter (40). For example, the control unit (50) can increase the electrical load of the shaft generator (20) by increasing the current command value applied to the second converter (40) and thereby increasing the current drawn from the shaft generator (20) through the first converter (30), and can reduce the electrical load of the shaft generator (20) by decreasing the current command value applied to the second converter (40) and thereby decreasing the current drawn from the shaft generator (20) through the first converter (30).

In an embodiment of the present invention, the control unit (50) can smoothly maintain the output of the main engine (10) by variably controlling the power output of the shaft generator (20) based on the torque applied to the propulsion shaft. For example, when a change in the output of the main engine (10) occurs or is expected to occur, the control unit (50) can measure the torque applied to the propulsion shaft and extract a torque fluctuation component corresponding to a target band based on the measured torque. Thereafter, the control unit (50) can control the load of the shaft generator (20) to offset the extracted torque fluctuation component, thereby controlling the amount of torque extracted at that point in time, thereby controlling the power output of the shaft generator (20) and smoothly maintaining the output of the main engine (10).

In one embodiment of the present invention, the control unit (50) can extract a torque fluctuation component corresponding to a target band using a mid-pass filter. The control unit (50) can extract a torque vibration component corresponding to an intermediate frequency band using the mid-pass filter and determine this as a torque fluctuation component to be compensated.

Thereafter, the control unit (50) suppresses the increase in torque of the propulsion shaft by increasing the load of the shaft generator (20) at a timing when the torque increases, and smooths the output of the main engine (10) by compensating for the decrease in torque of the propulsion shaft by reducing the load of the shaft generator (20) at a timing when the torque decreases.

In this way, the control unit (50) can efficiently smooth the output of the main engine (10) by selectively controlling only the torque vibration components of the intermediate frequency range, excluding the low frequency range caused by slow fluctuations such as sea level changes and the high frequency range caused by sensor noise, using a mid-pass filter.

Meanwhile, in another embodiment of the present invention, the control unit (50) may extract torque vibration components contained in a high-frequency band using a high-pass filter to simplify the control algorithm or improve the response speed, and determine these as torque fluctuation components to be compensated. Thereafter, the control unit may smooth the output of the main engine (10) by adjusting the load of the shaft generator (20) for the determined torque fluctuation components.

As mentioned above, the configuration in which the control unit (50) determines the torque fluctuation component to be compensated for using a mid-pass filter or a high-pass filter has been exemplified, but the control unit (50) can determine the torque fluctuation component to be compensated for using a band-pass filter capable of filtering a specific target other than the mid-pass filter and the high-pass filter, and of course, detecting the torque fluctuation component in a way other than a filter is not limited.

Figure 3 is a schematic diagram of a ship propulsion system (1) according to a second embodiment of the present invention. Below, the differences between this embodiment and the previous embodiment will be primarily described. Any omitted portions will be replaced with the previous description. This also applies to other embodiments below.

Referring to FIG. 3, a ship propulsion system (1) according to a second embodiment of the present invention includes a main engine (10), a shaft generator (20), a first converter (30), a second converter (40), and a control unit (50) of the ship propulsion system (1) according to the first embodiment, and may further include a battery (60).

The battery (60) can store at least a portion of the power generated from the shaft generator (20) under the control of the control unit (50) and discharge the stored power. The battery (60) stores and discharges direct current power, and the direct current power discharged from the battery (60) is converted into appropriate direct current power by the DC-DC converter (61) and then supplied to the direct current system. Here, the battery (60) can include a BMS (Battery Management System), a PCS (Power Conversion System), or an EMS (Energy Management System).

As described in the ship propulsion system (1) according to the first embodiment, the control unit (50) smooths the output of the main engine (10) by variably controlling the power output of the shaft generator (20). At this time, as the power output of the shaft generator (20) varies over time, a difference may occur between the power generated by the shaft generator (20) and the power required by the system load.

That is, if the amount of power generated by the shaft generator (20) is greater than the power required by the system load, surplus power is generated, and if the amount of power generated by the shaft generator (20) is less than the power required by the system load, sufficient power cannot be supplied to the system load.

In this embodiment, the control unit (50) controls the battery (60) to supply stored power to the system load of the ship or to store at least a portion of the power generated by the shaft generator (20) in response to a change in the power output of the shaft generator (20), thereby covering the difference between the power generated by the shaft generator (20) and the power required by the system load.

For example, the control unit (50) stores surplus power excluding the power demand of the system load in the battery (60) when the amount of power generated from the shaft generator (20) is greater than the power demand of the system load according to variable control of the shaft generator (20) for smoothing the output of the main engine (10), and covers the difference between the power generated by the shaft generator (20) and the power demand of the system load by causing the battery (60) to discharge the amount of power already stored by the amount of the shortfall when the amount of power generated from the shaft generator (20) is less than the power demand of the system load.

According to this embodiment, there is a technical effect that can additionally improve the fuel efficiency of the main engine (10) by using a low-capacity battery (60). In addition, according to this embodiment, the power output of the shaft generator (20) is variably controlled, and the battery (60) compensates for the fluctuations in the power output of the shaft generator (20), thereby smoothing the output of the main engine (10), and thus fuel consumption can be optimized. Therefore, although the equipment cost for installation (CAPEX) increases, there is an effect that the ship operating cost (OPEX) decreases.

Fig. 8 shows the output fluctuation of the main engine (10), the result of output smoothing by the control unit (50), and the difference between the smoothed output and the power demand of the system load. In Fig. 8, P _m represents the output used for propulsion of the main engine (10), i.e., the output in the case where there is no power extraction by the shaft generator (20), P _r represents the sum of the output used for propulsion of the main engine (10) and the output extracted by the shaft generator (20), i.e., the total output of the main engine (10), and P _m' represents the output of the main engine (10) smoothed according to the variable control of the shaft generator (20) by the control unit (50).

If the auxiliary propulsion device (80) described later is included in the system load, the load change due to the auxiliary propulsion device (80) may be included in P _r .

Referring to FIG. 8, the output smoothing of the main engine (10) is achieved by variable control of the shaft generator (20) of the control unit (50), so that in some time sections, the power P _SG generated by the shaft generator (20) is greater than the power P _grid required by the system, and in some time sections, the power P _SG generated by the shaft generator (20) is less than the power P _grid required by the system.

Accordingly, the control unit (50) controls the battery (60) to discharge the stored power when P _grid exceeds P _SG , as in the P _B- section of FIG. 8, and controls the battery (60) to store surplus power when P _grid is less than P _SG , as in the P _B+ section, thereby effectively compensating for the difference between the power generation of the shaft generator (20) and the total power demand. Accordingly, the power system within the ship is stabilized.

FIG. 4 is a schematic diagram of a ship propulsion system (1) according to a third embodiment of the present invention. Referring to FIG. 4, the ship propulsion system (1) according to the third embodiment of the present invention includes the main engine (10), shaft generator (20), first converter (30), second converter (40), and control unit (50) of the ship propulsion system (1) according to the first embodiment, and may further include a generator engine (70).

A generator engine (70) is installed on board and drives a generator under the control of a control unit (50) to generate AC power. At this time, the generator may be a diesel generator, but is not limited thereto.

In this embodiment, the control unit (50) controls the power supply of the generator engine (70) in response to the change in the power output of the shaft generator (20), thereby covering the difference between the power generated by the shaft generator (20) and the power required by the system load.

For example, the control unit (50) can cover the difference between the power generated by the shaft generator (20) and the power required by the system load by controlling the generator engine (70) to supply the insufficient power when the power generated from the shaft generator (20) is less than the power required by the system load according to the variable control of the shaft generator (20) for smoothing the output of the main engine (10).

Meanwhile, since the power generated by the generator engine (70) can sufficiently supply power to the system load, and the generator engine (70) cannot store surplus power when the power generation amount of the shaft generator (20) exceeds the power required by the system load, it is possible to use a shaft generator (20) with a smaller capacity than the shaft generator (20) of the second embodiment in this embodiment.

According to this embodiment, the fuel efficiency of the main engine (10) is improved by compensating for fluctuations in the power generation of the shaft generator (20) without using an expensive battery (60).

FIG. 5 is a schematic diagram of a ship propulsion system (1) according to a fourth embodiment of the present invention. Referring to FIG. 5, the ship propulsion system (1) according to the fourth embodiment of the present invention includes the main engine (10), shaft generator (20), first converter (30), second converter (40), control unit (50), and battery (60) of the ship propulsion system (1) according to the second embodiment, and may further include a generator engine (70) according to the third embodiment.

In this embodiment, the control unit (50) controls the battery (60) and the generator engine (70) in response to changes in the power output of the shaft generator (20), thereby covering the difference between the power generated by the shaft generator (20) and the power required by the system load.

The control unit (50) stores surplus power excluding the power demand of the system load in the battery (60) when the amount of power generated from the shaft generator (20) is greater than the power demand of the system load according to variable control of the shaft generator (20) for smoothing the output of the main engine (10), and when the amount of power generated from the shaft generator (20) is less than the power demand of the system load, the control unit (50) can cover the difference between the power generated by the shaft generator (20) and the power demand of the system load by discharging the power already stored by the battery (60) to the amount of the shortfall or by causing the generator engine (70) to produce power.

In this embodiment, the control unit (50) can select a power source to supply power to the system load preferentially among the battery (60) and the generator engine (70) based on the state of charge of the battery (60).

In one embodiment, the control unit (50) may control the battery (60) to preferentially discharge pre-stored power when the state of charge (SOC) of the battery (60) is equal to or greater than a predetermined threshold value, and then sequentially allow the generator engine (70) to supply the insufficient power when the discharge of the battery (60) does not satisfy the power demand of the system load. On the other hand, the control unit (50) may control the battery (60) not to discharge power when the state of charge of the battery (60) is less than a predetermined threshold value, and allow the generator engine (70) to supply the difference between the power generation amount of the shaft generator (20) and the power demand of the system load.

According to this embodiment, the capacity of the shaft generator (20) itself is reduced, and instead, the generator engine (70) is used efficiently, thereby reducing the equipment cost (CAPEX), while the operating cost (OPEX) is also reduced through effective use of fuel as the output of the main engine (10) is smoothed, which is particularly advantageous in LNG fuel propulsion ships.

Fig. 6 is a schematic diagram of a ship propulsion system (1) according to a fifth embodiment of the present invention. Referring to Fig. 6, the ship propulsion system (1) according to the fifth embodiment of the present invention includes the main engine (10), shaft generator (20), first converter (30), second converter (40), and control unit (50) of the ship propulsion system (1) according to the first embodiment, and may further include an auxiliary propulsion device (80).

The auxiliary propulsion device (80) consumes electric power to generate propulsion power for the vessel. In the present embodiment, the auxiliary propulsion device (80) is a wind-assisted propulsion device that generates propulsion power for the vessel using wind power, and may include at least one of a rotor and a wing sail, but is not limited thereto.

In this embodiment, the auxiliary propulsion device (80) consumes power during operation, thereby increasing the torque load transmitted from the propulsion shaft to the shaft generator, but simultaneously reducing the overall load on the propulsion shaft by assisting the propulsion power. Meanwhile, the power consumed and the magnitude of the generated propulsion power of the auxiliary propulsion device (80) may vary depending on the maritime environment and operating conditions.

When a change in the output of the main engine (10) due to the power consumption and propulsion power generation of the auxiliary propulsion device (80) occurs or is expected, the control unit (50) variably controls the power output of the shaft generator (20) in a direction that offsets the change in the output of the main engine (10), thereby smoothing the output of the main engine (10).

Meanwhile, in the present embodiment, the control unit (50) receives in real time at least one of the operating status of the auxiliary propulsion device (80), the expected propulsion force and power consumption information according to the wind speed and wind direction, and adjusts the power output of the shaft generator (20) in advance based on the received information, thereby predicting output fluctuations according to the operation of the auxiliary propulsion device (80) in advance and performing smoothing control more precisely.

Fig. 7 is a schematic diagram of a ship propulsion system (1) according to a sixth embodiment of the present invention. Referring to Fig. 7, the ship propulsion system (1) according to the sixth embodiment of the present invention includes the main engine (10), shaft generator (20), first converter (30), second converter (40), control unit (50), and auxiliary propulsion device (80) of the ship propulsion system (1) according to the fifth embodiment, and may further include a battery (60) according to the second embodiment.

As previously explained, when the ship propulsion system (1) includes an auxiliary propulsion device (80), the fluctuations in the output of the main engine (10) may increase due to the power consumption and propulsion assistance effect of the auxiliary propulsion device (80). At this time, when the control unit (50) variably controls the power output of the shaft generator (20) to smooth the output of the main engine (10), a difference may occur between the power generation of the shaft generator (20) and the power demand of the system load. As previously mentioned, the difference between the power generation of the shaft generator (20) and the power demand of the system load can be effectively compensated for by charging and discharging the battery (60).

According to the ship propulsion system (1) according to the present embodiment, when a change in the output of the main engine (10) occurs or is expected, the control unit (50) can smoothly maintain the output of the main engine (10) by variably controlling the power output of the shaft generator (20) in a direction that offsets the change in the output of the main engine (10), thereby improving the fuel efficiency and power supply stability of the main engine (10).

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

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.

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 (11)

The main engine, which is connected to the propulsion system through the propulsion shaft and generates the propulsion power of the ship; A shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; and It includes a control unit that controls the power output of the above-mentioned shaft generator, The above control unit A ship propulsion system that variably controls the power output of the shaft generator to offset the output fluctuation of the main engine when a fluctuation in the output of the main engine occurs or is expected. In the first paragraph, The above control unit When the output of the main engine is reduced or expected to be reduced, the output fluctuation of the main engine is offset by increasing the load of the shaft generator, A ship propulsion system that compensates for fluctuations in the output of the main engine by reducing the load of the shaft generator when the output of the main engine is increased or is expected to increase. In the first paragraph, Further comprising a battery for storing at least a portion of the power generated from the above-mentioned shaft generator or discharging the stored power, The above control unit A ship propulsion system that covers the difference between the power generated by the shaft generator and the power required by the system load by controlling the battery to supply the stored power to the system load of the ship or to store at least a portion of the power generated by the shaft generator in response to a change in the power output of the shaft generator. In the first paragraph, Further comprising a generator engine for supplying power to the system load of the above vessel, The above control unit A ship propulsion system that covers the difference between the power generated by the shaft generator and the power required by the system load by controlling the power supply of the generator engine in response to the change in the power output of the shaft generator. In the first paragraph, A battery for storing at least a portion of the power generated from the above-mentioned shaft generator or discharging the stored power; and Further comprising a generator engine for supplying power to the system load of the above vessel, The above control unit A ship propulsion system that covers the difference between the power generated by the shaft generator and the power required by the system load by controlling at least one of the battery and the generator engine in response to a change in the power output of the shaft generator. In paragraph 5, The above control unit When the power generated by the shaft generator is greater than the power required by the system load according to the variable control of the shaft generator, the surplus power excluding the power required by the system load is stored in the battery. A ship propulsion system that covers the difference between the power generated by the shaft generator and the power required by the system load by discharging the stored power from the battery or causing the generator engine to produce power when the power generated by the shaft generator is less than the power required by the system load. In paragraph 6, The above control unit A ship propulsion system that selects a power source to supply power to the system load preferentially among the battery and the generator engine based on the state of charge of the battery. In paragraph 7, The above control unit If the state of charge of the above battery is higher than a predetermined threshold value, the battery is controlled to preferentially discharge the stored power, A ship propulsion system that controls the generator engine to produce power when the state of charge of the battery is below a predetermined threshold. In the first paragraph, The above control unit A ship propulsion system that extracts a torque fluctuation component corresponding to a target band based on the torque applied to the propulsion shaft, and variably controls the power output of the shaft generator in a direction that offsets the output fluctuation of the main engine by adjusting the load of the shaft generator to offset the extracted torque fluctuation component. In paragraph 9, The torque applied to the above propulsion shaft reflects the output fluctuation of the above main engine, A ship propulsion system, wherein the output fluctuation of the main engine is caused by at least one of fluctuations in the system load of the ship, fluctuations due to sea conditions, and fluctuations generated by the main engine itself. The main engine that generates the ship's propulsion power; A shaft generator coupled to the main engine and generating electric power by extracting at least a portion of the power generated by the main engine; and It includes a control unit that controls the load of the above-mentioned shaft generator, The above control unit A ship propulsion system that variably controls the load of the shaft generator to offset the output fluctuation of the main engine when the output fluctuation of the main engine occurs or is expected.