Propulsion system, control program, and control method for vessel

Abstract

To provide a propulsion system, a control program, and a control method for a vessel capable of carrying out operation with a high fuel consumption rate while suppressing reduction in heat efficiency of an engine in a vessel generating propulsion force by using the engine.SOLUTION: A propulsion system for a vessel includes: an engine mechanically connected to a propulsion propeller and having rotation number controlled according to a propulsion force command value; a power generator mechanically connected to the engine and capable of generating power by using driving force of the engine; a power converter electrically connected to the power generator; and a control unit for controlling the engine and the power converter, wherein a processing circuit for the controller acquires the propulsion force command value, determines weather or not the propulsion force command value is within a prescribed range lower than a reference value, and controls the rotation number of the engine to maintain the rotation number in the reference value as well as controls the power converter so as to increase a power generation amount in the power generator to be more than a power generation amount in the reference value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a ship propulsion system, a control program, and a control method. [Background technology]

[0002] 2. Description of the Related Art In a ship that uses driving force generated by an engine as propulsion, it is important to reduce fuel consumption.

[0003] The following Patent Document 1 proposes adopting a variable pitch propeller with a changeable blade angle as the propulsion propeller, and controlling the generated power when the motor generator generates power based on engine power or the electric power for driving the motor generator based on the power from a storage battery connected to the motor generator, based on whether the blade angle command value is changing in an increasing or decreasing direction when the blade angle of the variable pitch propeller is changed. As a result, the following Patent Document 1 claims that it is possible to reduce engine load fluctuations caused by changing the blade angle of the variable pitch propeller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6697218 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned Patent Document 1 does not propose any measures to improve fuel consumption efficiency during steady operation. In a ship, when there is sufficient time before reaching a destination, it is possible to operate the ship at a low speed to suppress fuel consumption by reducing the engine speed. Fuel consumption can be reduced by lowering the engine speed in response to a decrease in the thrust command value, but when the engine speed is reduced, the engine operates in a low load range, which may reduce the thermal efficiency of the engine. In particular, when the engine is a gas engine that uses liquefied gas such as liquefied natural gas as fuel by vaporizing it, combustion becomes unstable in the low load range, and a large amount of unburned gas is generated, making continuous operation difficult. On the other hand, in the case of a ship equipped with a controllable pitch propeller, the ship speed can be reduced by adjusting the blade angle of the controllable pitch propeller without reducing the engine speed, but fuel consumption efficiency cannot be increased by reducing the ship speed.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a ship propulsion system, a control program, and a control method that can operate a ship that uses an engine to generate propulsive force with high fuel efficiency while suppressing a reduction in the thermal efficiency of the engine. [Means for solving the problem]

[0007] A propulsion system according to one aspect of the present disclosure is a ship propulsion system comprising an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion force command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, wherein the controller includes a processing circuit that acquires the propulsion force command value and determines whether the propulsion force command value is within a predetermined range lower than a reference value, and if the propulsion force command value is within the predetermined range, controls the engine to maintain the engine rotational speed at the reference value and controls the power converter to increase the amount of power generated by the generator above the amount of power generated at the reference value.

[0008] A control program according to another aspect of the present disclosure is a control program for a ship including an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion force command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, wherein the control program causes the controller to acquire the propulsion force command value, determine whether the propulsion force command value is within a predetermined range lower than a reference value, and, if the propulsion force command value is within the predetermined range, control the engine so as to maintain the engine rotational speed at the reference value and control the power converter so as to increase the amount of power generated by the generator above the amount of power generated at the reference value.

[0009] A control method according to another aspect of the present disclosure is a control method for a ship including an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, the control method acquiring the propulsion command value, determining whether the propulsion command value is within a predetermined range lower than a reference value, and if the propulsion command value is within the predetermined range, controlling the engine to maintain the rotational speed of the engine at the rotational speed at the reference value, and controlling the power converter to increase the amount of power generated by the generator above the amount of power generated at the reference value. Effect of the Invention

[0010] According to the present disclosure, in a ship that generates propulsive force using an engine, it is possible to operate the engine with high fuel efficiency while suppressing a decrease in thermal efficiency of the engine. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a block diagram showing a schematic configuration of a marine vessel propulsion system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a flowchart showing a control mode in the first control mode in this embodiment. [Diagram 3] FIG. 3 is an image diagram that shows engine output, thrust force command value, and power generation target value during control based on a reference value and during rotation speed maintenance control in the first embodiment. [Figure 4] FIG. 4 is an image diagram that shows engine output, thrust force command value, and power generation target value during control based on a reference value and during rotation speed maintenance control in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. In the following, the same or corresponding elements are denoted by the same reference numerals throughout the drawings, and duplicated descriptions thereof will be omitted.

[0013] [Embodiment 1] 1 is a block diagram showing a schematic configuration of a ship propulsion system according to an embodiment of the present disclosure. In this embodiment, a hybrid propulsion ship in which an engine 3 and a motor generator 4 can be used as a source of driving force for a propulsion propeller 2 is exemplified as the ship.

[0014] The propulsion system 1 in this embodiment includes a propulsion propeller 2, an engine 3, a motor generator 4, and a first power converter 7. The propulsion propeller 2 is a controllable pitch propeller configured so that the blade angle can be changed in accordance with a thrust force command value.

[0015] The engine 3 is a gas engine that generates driving force using a fuel including a fuel gas obtained by vaporizing liquefied natural gas. The engine 3 may be a gas-fired engine that burns only the fuel gas obtained by vaporizing liquefied natural gas, a dual-fuel engine that can switch between burning the fuel gas and a liquid fuel such as heavy oil, or a diesel engine that burns a liquid fuel.

[0016] The engine 3 and the motor generator 4 are mechanically connected to the propulsion propeller 2 via a reduction gear 5. The motor generator 4 is electrically connected to a first power converter 7. The first power converter 7 is interposed between the DC wiring 6 and the motor generator 4. The motor generator 4 can transmit power to the propulsion propeller 2 by generating power from electric power supplied through the DC wiring 6. At this time, the first power converter 7 converts the DC voltage in the DC wiring 6 to an AC voltage and outputs it to the motor generator 4. Furthermore, the motor generator 4 can also generate power using the driving force of the engine 3 and supply the power to the DC wiring 6. At this time, the first power converter 7 converts the AC voltage generated by the electric power generated by the motor generator 4 to a DC voltage and outputs it to the DC wiring 6.

[0017] Furthermore, a power storage device 9 is connected to the DC wiring 6. The power storage device 9 is a secondary battery, a capacitor, or the like, and may include a power converter such as a DC-DC converter that converts the DC voltage of the DC wiring 6 into a predetermined DC voltage. Furthermore, an AC wiring 11 is connected to the DC wiring 6 via a second power converter 10. The second power converter 10 converts the DC voltage of the DC wiring 6 into an AC voltage and outputs it to the AC wiring 11, and converts the AC voltage of the AC wiring 11 into a DC voltage and outputs it to the DC wiring 6. An onboard load may be connected to the AC wiring 11 or the DC wiring 6.

[0018] Such a propulsion system 1 can generate propulsive force for the ship in cooperation between the engine 3, which is a mechanical propulsion unit, and the motor generator 4, which is an electric propulsion unit. Also, the propulsion system 1 can recover surplus propulsive force generated by the engine 3 as electric power by the motor generator 4, and supply the electric power to the AC wiring 11 or store it in the capacitor 9.

[0019] The propulsion system 1 includes a controller 14. The controller 14 includes a processing circuit 15 that performs various types of signal processing. The processing circuit 15 includes a computer such as a microcontroller, a personal computer, or a PLC (Programmable Logic Controller). More specifically, the processing circuit 15 includes a processor, a memory, and peripheral circuits. The processor includes, for example, a CPU or an MPU. The memory includes, for example, a ROM, a RAM, a register, a non-volatile storage, and the like. The peripheral circuits include an input / output interface, and the like. The controller 14 is connected to an operation input device 16 that operates the hybrid propulsion ship. The controller 14 may be connected to a monitor that displays a control state, a speaker that outputs audio, or the like.

[0020] It should be noted that the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit, since it includes transistors and other circuits. In this specification, a circuit, unit, means, or part is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed in this specification, or other known hardware that is programmed or configured to perform the recited functions. In the case where the hardware is a processor, which is considered a type of circuit, the circuit, unit, or means is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0021] A control program for controlling the controlled objects is stored in the memory of the controller 14. The controller 14 controls the controlled objects based on the control program. The controlled objects of the controller 14 include the propulsion propeller 2, the engine 3, and the first power converter 7. The controller 14 may be configured as one controller that controls these components 2, 3, and 7, or may be configured by two or more controllers. The controller 14 may also be configured to be capable of controlling the storage battery 9, the second power converter 10, or a load connected to the AC wiring 11.

[0022] The controller 14 controls the blade angle of the propulsion propeller 2, the output of the engine 3, and the first power converter 7 based on the propulsion force command value Fo. The propulsion force command value Fo is input from an operation input device 16. The operation input device 16 may be configured, for example, with an operation lever or an operation handle for adjusting the speed of the vessel and switching between forward and reverse. For example, the operation lever is configured so that the position where it is operated a maximum amount in a first direction corresponds to the maximum vessel speed on the forward side, the position where it is operated a maximum amount in a second direction opposite to the first direction corresponds to the maximum vessel speed on the reverse side, and the neutral position corresponds to a vessel speed of 0.

[0023] The operation input device 16 generates a larger propulsive force command value Fo as the vessel speed corresponding to the operation position of the operation lever increases. The processing circuit 15 generates a blade angle target value Wo of the propulsion propeller 2 based on the propulsive force command value Fo. The processing circuit 15 generates a blade angle target value Wo such that the blade angle increases as the propulsive force command value Fo increases. For example, when the operation lever is in a position in the first direction, a blade angle target value Wo that is a positive blade angle is generated, and when the operation lever is in a position in the second direction, a blade angle target value Wo that is a negative blade angle is generated.

[0024] In this embodiment, the propulsion system 1 is equipped with a blade angle sensor 17 that detects the blade angle of the propulsion propeller 2. The controller 14 acquires the value detected by the blade angle sensor 17 and performs feedback control so that the blade angle of the propulsion propeller 2 becomes the blade angle target value Wo.

[0025] Furthermore, the controller 14 controls the rotation speed of the engine 3 according to the thrust force command value Fo. The processing circuit 15 generates an engine rotation speed target value Eo from the thrust force command value Fo. The controller 14 controls the engine 3 so that the rotation speed of the engine 3 is maintained at the engine rotation speed target value Eo.

[0026] Furthermore, the controller 14 controls the first power converter 7 according to the power conversion command value. For example, in the normal control mode during navigation, the controller 14 controls the motor generator 4 to generate a predetermined amount of power and supply it to the DC wiring 6. In the present embodiment, the control mode for the first power converter 7 during normal navigation is referred to as the first control mode. In the first control mode, the motor generator 4 always generates power. Therefore, the engine speed target value Eo is set to a speed that generates an output greater than the output generated by the propulsion propeller 2.

[0027] In the first control mode, the power supplied from the first power converter 7 to the DC wiring 6 is supplied to the AC wiring 11 via the second power converter 10. The surplus power is supplied from the DC wiring 6 to the capacitor 9 and stored in the capacitor 9. When the charge rate of the capacitor 9 is equal to or greater than a predetermined value, the controller 14 can control the capacitor 9 to supply the power stored in the capacitor 9 to the AC wiring 11 or the motor generator 4. In this case, the controller 14 reduces the power supplied from the motor generator 4 to the DC wiring 6 compared to the first control mode, or controls to supply power from the DC wiring 6 to the motor generator 4.

[0028] In the present embodiment, the control mode for the first power converter 7 during discharge of the capacitor 9 is referred to as the second control mode. The second control mode is a hybrid mode that generates propulsion force using the driving force of the engine 3 and the driving force of the motor generator 4.

[0029] The processing circuit 15 performs a rotation speed maintenance control to maintain the rotation speed of the engine 3 when the propulsion force command value Fo is within a predetermined range lower than the reference value in the first control mode. In the following example, the reference value of the propulsion force command value Fo is the first command value Fo1, and the range for performing the rotation speed maintenance control is equal to or greater than the second command value Fo2 smaller than the first command value Fo1 and smaller than the first command value Fo1, that is, Fo2 ≤ Fo < Fo1. For example, the first command value Fo1 corresponds to the propulsion force command value when the operation position of the operation lever is Navigation Full (Nav. FULL), and the second command value Fo2 corresponds to the propulsion force command value when the operation position of the operation lever is Full (FULL).

[0030] Fig. 2 is a flow chart showing the control mode in the first control mode in this embodiment. Fig. 3 is an image diagram showing the engine output, the thrust command value, and the power generation target value in the control by the reference value and in the control to maintain the rotation speed in the first embodiment. Note that the engine output is an engine output value converted from the engine rotation speed target value Eo, and is represented by the engine rotation speed target value Eo in Fig. 3.

[0031] As described above, in the first control mode, the motor generator 4 constantly generates power, so the engine speed target value Eo is set to a rotation speed that generates an output greater than the output generated by the propulsion propeller 2. That is, when the thrust force command value Fo is the first command value Fo1 that is a reference value, the processing circuit 15 generates an engine speed target value Eo1 from the engine 3 that is greater than the rotation speed corresponding to the first command value Fo1, and controls the engine 3 to achieve the engine speed target value Eo1. Furthermore, the processing circuit 15 controls the first power converter 7 to generate power in the motor generator 4 by using the surplus driving force output from the engine 3.

[0032] As shown in Fig. 3, if the engine speed target value when the thrust force command value Fo is the first command value Fo1 is Eo1, then Eo1 = Fo1 + Go1 is obtained in terms of torque or power. Go1 is a power generation amount target value indicating a target value for the amount of power generated by the motor generator 4. The processing circuit 15 generates a power conversion command value such that the first power converter 7 receives power according to the power generation amount target value Go1 from the motor generator 4 and supplies it to the DC wiring 6. In this embodiment, Fo1 is a reference value of the thrust force command value Fo, Eo1 is a reference value of the engine speed target value Eo, and Go1 is a reference value of the power generation amount target value Go.

[0033] In the first control mode, the processing circuit 15 acquires a thrust command value Fo (step S1). The processing circuit 15 determines whether the thrust command value Fo is within a predetermined range, that is, whether the thrust command value Fo satisfies Fo2 ≦ Fo < Fo1 (step S2). When the thrust command value Fo is outside the predetermined range (No in step S2), the processing circuit 15 sets an engine speed target value Eo, a blade angle target value Wo, and a power generation amount target value Go according to the acquired thrust command value Fo (step S7). For example, when the thrust command value Fo is the first command value Fo1, the processing circuit 15 sets the power generation amount target value Go to Go1 and the engine speed target value Eo to Eo1 as described above. The same applies when the thrust command value Fo is greater than the first command value Fo1 and when the thrust command value Fo is less than the second command value Fo2.

[0034] On the other hand, when the thrust command value Fo is within the predetermined range (Yes in step S2), the processing circuit 15 executes rotational speed maintenance control. In this case, the processing circuit 15 sets the engine speed target value Eo to a constant value regardless of the acquired thrust command value Fo (step S3). The engine speed target value Eo at this time is the engine speed target value Eo1 which is a reference value. Further, the processing circuit 15 sets the blade angle target value Wo according to the acquired thrust command value Fo (step S4).

[0035] Furthermore, the processing circuit 15 generates a power generation amount target value Go such that the power generation amount in the motor generator 4 is increased from the power generation amount at the reference value. More specifically, the processing circuit 15 calculates a thrust difference Fd between the thrust command value Fo and the first command value Fo1 which is the reference value (step S5). The thrust difference Fd is represented by Fd = Fo1 - Fo. The processing circuit 15 calculates the power generation amount obtained by adding the power generation amount corresponding to the thrust difference Fd to the power generation amount target value Go1 at the reference value as the power generation amount target value Go (step S6). The power generation amount target value Go is represented by Go = G1 + Fd.

[0036] As shown in FIG. 3, when the propulsive force command value Fo is within a predetermined range, the engine speed target value Eo is maintained at the reference value Eo1 of the engine speed target value, even though the propulsive force command value Fo is smaller than the first command value Fo1, which is a reference value. Therefore, in this embodiment, the ratio of the driving force of the engine 3 used for power generation is increased. This allows low-speed operation to be performed to reduce the speed of the ship while maintaining the rotation speed of the engine 3. Since the propulsive force is proportional to the cube of the ship speed, low-speed operation can reduce fuel consumption. Therefore, according to this embodiment, in a ship that generates propulsive force using the engine 3, it is possible to perform operation with high fuel consumption efficiency while suppressing a decrease in the thermal efficiency of the engine 3. This makes it possible to realize a ship with low environmental impact. In addition, since the driving force of the engine 3 can be efficiently used for power generation, it is also possible for the configuration for generating power in the propulsion system 1 to be only the motor generator 4 that generates power using the driving force of the engine 3, which is the main engine. In this case, the ship can be made smaller and lighter than a configuration that includes a separate generator.

[0037] [Embodiment 2] A second embodiment of the present disclosure will be described below. In this embodiment, the configuration of the propulsion system 1 is the same as that of the first embodiment shown in Fig. 1. In the description of this embodiment, the same components as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

[0038] This embodiment differs from embodiment 1 in that the specified range for performing rotation speed maintenance control includes both a rotation speed target value range in a first control mode in which the driving force of the engine 3 is allocated to the propulsion force of the ship and power generation by the motor generator 4, and a rotation speed target value range in a second control mode in which propulsion force is generated by the driving force of the engine 3 and the driving force of the motor generator 4.

[0039] FIG. 4 is an image diagram that shows the engine output, the thrust command value, and the power generation target value during control based on a reference value and during rotation speed maintenance control in the second embodiment. In this embodiment, the processing circuit 15 switches between the first control mode and the second control mode according to the thrust command value Fo. In the example of FIG. 4, the reference value of the thrust command value Fo is the first command value Fo1, as in the example of FIG. 3. When the thrust command value Fo is equal to or greater than the second command value Fo2 and less than the first command value Fo1, the processing circuit 15 executes the rotation speed maintenance control for low-speed operation, as in the example of FIG. 3.

[0040] Furthermore, when the propulsive force command value Fo is greater than the first command value Fo1 and less than the third command value Fo3, the processing circuit 15 executes control to reduce the power generation target value Go while maintaining the engine speed target value Eo at the reference value Eo1. When the propulsive force command value Fo is the third command value Fo3, the processing circuit 15 sets the power generation target value Go to zero. In other words, the third command value Fo3 is set to a propulsive force value equivalent to the engine output at the reference value Eo1 of the engine speed target value Eo.

[0041] In this way, the processing circuit 15 executes the first control mode when the thrust command value Fo is less than the third command value Fo3. On the other hand, the processing circuit 15 executes the second control mode when the thrust command value Fo is greater than the third command value Fo3. That is, the processing circuit 15 switches between the first control mode and the second control mode with the thrust command value Fo being based on the third command value Fo3. In this example, the fourth command value Fo4 set to a value greater than the third command value Fo3 is a reference value when the motor generator 4 generates a driving force in the second control mode. The driving force generated by the motor generator 4 at the fourth command value Fo4, i.e., the applied force target value Ao4, becomes a reference value for the applied force of the motor generator 4 on the engine 3. The processing circuit 15 generates a power conversion command value such that the first power converter 7 supplies power according to the applied force target value Ao from the DC wiring 6 to the motor generator 4.

[0042] In the second control mode, when the propulsion force command value Fo decreases from the fourth command value Fo4, the processing circuit 15 controls the first power converter 7 to reduce the driving force generated by the motor generator 4 while maintaining the engine speed of the engine 3 at the current speed. More specifically, when the propulsion force command value Fo is greater than the third command value Fo3 and less than the fourth command value Fo4, the processing circuit 15 maintains the engine speed target value Eo at the reference value Eo1. In this case, the processing circuit 15 calculates a propulsion force difference Fda between the acquired propulsion force command value Fo and the fourth command value Fo4. The propulsion force difference Fda is represented by Fda = Fo4 - Fo. The processing circuit 15 calculates the boosting force target value Ao by subtracting the boosting force corresponding to the propulsion force difference Fda from the boosting force target value Ao4 at the fourth command value Fo4. The boosting force target value Ao is represented by Ao = Ao4 - Fda.

[0043] According to the above embodiment, similar to the first embodiment, when the propulsion force command value Fo is within a predetermined range lower than the first command value Fo1 which is the reference value in the first power generation mode, that is, when Fo2 ≤ Fo < Fo1, although the propulsion force command value Fo is smaller compared to the first command value Fo1 which is the reference value, the engine speed target value Eo is maintained at the reference value Eo1 of the engine speed target value. Therefore, in the present embodiment, the ratio of the driving force of the engine 3 used for power generation is increased. As a result, it is possible to perform a low-speed operation in which the speed of the ship is reduced while maintaining the engine speed of the engine 3. Therefore, according to the present embodiment, it is possible to perform an operation with high fuel consumption efficiency while suppressing a reduction in the thermal efficiency of the engine 3 in a ship that generates propulsion force using the engine 3.

[0044] Furthermore, even in the second control mode in which the output of the motor generator 4 is used to boost the output of the engine 3, the output of the motor generator 4 is changed while maintaining the engine speed of the engine 3 constant. As a result, even in the second control mode, the speed of the ship can be increased or decreased while maintaining the engine speed of the engine 3. In this way, the propulsion force can be continuously changed while maintaining the engine speed of the engine 3, and the switching between the first control mode and the second control mode can be performed smoothly.

[0045] In this embodiment, as described above, the predetermined range in which the rotation speed maintenance control is performed includes not only the rotation speed target value range in the first control mode but also the rotation speed target value range in the second control mode, so that the range in which the ship speed can be changed while maintaining the rotation speed of the engine 3 can be widened. This makes it possible to keep the maximum output of the engine 3 low even if the maximum output that can be output by the propulsion system 1 is the same. Therefore, the maximum output can be maintained while downsizing the engine 3 installed in the same class of ship.

[0046] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various improvements, changes, and modifications are possible without departing from the spirit and scope of the present disclosure.

[0047] [Other embodiments] For example, in the above embodiment, the propulsion system 1 for a hybrid propulsion ship is provided with a motor-generator 4 configured to be capable of transmitting power to the propulsion propeller 2 as a generator, but any propulsion system may be used as long as the generator is capable of generating power using the driving force of the engine 3. For example, the control aspect of the present disclosure is also applicable to a propulsion system 1 that does not output driving force to the propulsion propeller 2, that is, that is, that is provided with a generator that only has the function of generating power using the driving force of the engine 3.

[0048] In the above embodiment, the engine 3 and the motor generator 4 are connected in parallel to the propulsion propeller 2 via the reduction gear 5, but the configuration is not limited to this. For example, the propulsion system 1 may include an intermediate shaft type motor generator 4 in which a rotor of a generator is fixed to an intermediate shaft connected between the output shaft of the engine 3 and the rotating shaft of the propulsion propeller 2.

[0049] Furthermore, in the above embodiment, the propulsion system 1 equipped with a controllable pitch propeller as the propulsion propeller 2 has been exemplified, but the propulsion system may be equipped with a propulsion propeller with a fixed blade angle.

[0050] The control program in the above embodiment may be configured as a program product provided by downloading from an external computer or recorded on a recording medium, or may be configured as a computer product with the control program pre-installed.

[0051] [Summary of this disclosure] [Item 1] A propulsion system according to one aspect of the present disclosure is a ship propulsion system comprising an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion force command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, wherein the controller includes a processing circuit that acquires the propulsion force command value and determines whether the propulsion force command value is within a predetermined range lower than a reference value, and if the propulsion force command value is within the predetermined range, controls the engine to maintain the engine rotational speed at the reference value and controls the power converter to increase the amount of power generated by the generator above the amount of power generated at the reference value.

[0052] According to the above configuration, when the propulsive force command value is within a predetermined range lower than the reference value, the engine speed is maintained at the speed corresponding to the reference value even though the propulsive force command value is smaller than the reference value. The proportion of the engine driving force used for power generation is increased accordingly. This allows low-speed operation in which the ship speed is reduced while maintaining the engine speed. Therefore, in a ship that generates propulsive force using an engine, it is possible to operate with high fuel consumption efficiency while suppressing a decrease in the engine thermal efficiency.

[0053] [Item 2] In the propulsion system of item 1, the processing circuit may calculate a thrust difference between the thrust command value and the reference value, and calculate a power generation amount by adding a power generation amount corresponding to the thrust difference to the power generation amount at the reference value as a power generation amount target value.

[0054] [Item 3] In the propulsion system of item 1 or 2, the generator may be a motor generator configured to be capable of transmitting power to the propulsion propeller, and when the propulsion force command value is reduced while the motor generator is transmitting power to the propulsion propeller, the processing circuit may control the power converter to reduce the driving force generated by the motor generator while maintaining the engine speed at a current speed. According to this, even when the driving force output from the motor generator is used to assist the output of the engine, the output of the motor generator is changed while maintaining the engine speed constant. This makes it possible to increase or decrease the speed of the ship while maintaining the engine speed regardless of whether the motor generator is in an assisting state or a generating state.

[0055] [Item 4] In any of the propulsion systems of items 1 to 3, when the thrust force command value is the reference value, the processing circuit may control the engine to rotate at a speed higher than a speed corresponding to the thrust force command value, and control the power converter to generate power in the generator using surplus driving force output from the engine.

[0056] [Item 5] In the propulsion system of any one of items 1 to 4, the engine may be a gas engine that generates driving force using a fuel including a fuel gas obtained by vaporizing a liquefied gas.

[0057] [Item 6] A control program for a ship according to another aspect of the present disclosure is a control program for a ship including an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, wherein the control program causes the controller to acquire the propulsion command value, determine whether the propulsion command value is within a predetermined range lower than a reference value, and, if the propulsion command value is within the predetermined range, control the engine so as to maintain the engine rotational speed at the reference value and control the power converter so as to increase the amount of power generated by the generator above the amount of power generated at the reference value.

[0058] [Item 7] A ship control method according to another aspect of the present disclosure is a control method for a ship including an engine mechanically connected to a propulsion propeller and whose rotational speed is controlled in accordance with a propulsion command value, a generator mechanically connected to the engine and capable of generating electricity using the driving force of the engine, a power converter electrically connected to the generator, and a controller that controls the engine and the power converter, the control method acquiring the propulsion command value, determining whether the propulsion command value is within a predetermined range lower than a reference value, and if the propulsion command value is within the predetermined range, controlling the engine to maintain the rotational speed of the engine at the rotational speed at the reference value, and controlling the power converter to increase the amount of power generated by the generator above the amount of power generated at the reference value. [Explanation of symbols]

[0059] 1 Propulsion System 2 thrust propeller 3 Engine 4. Motor generator (generator) 7 First power converter (power converter) 14 Controller 15 Processing circuit

Claims

1. an engine mechanically connected to the propulsion propeller and having a rotation speed controlled in accordance with a thrust command value; a generator mechanically connected to the engine and capable of generating electricity by utilizing a driving force of the engine; a power converter electrically connected to the generator; A controller for controlling the engine and the power converter, The controller includes a processing circuit; The processing circuitry includes: Acquire the thrust command value; determining whether the thrust command value is within a predetermined range lower than a reference value; a propulsion system that, when the thrust command value is within the predetermined range, controls the engine so as to maintain a rotation speed of the engine at the rotation speed at the reference value, and controls the power converter so as to increase an amount of power generated by the generator above the amount of power generated at the reference value.

2. The processing circuitry includes: Calculating a thrust difference between the thrust command value and the reference value; The propulsion system according to claim 1 , wherein an amount of power generation is calculated as a power generation target value by adding an amount of power generation corresponding to the thrust force difference to an amount of power generation at the reference value.

3. the generator is a motor-generator configured to be capable of transmitting power to the propulsion propeller, 3. The propulsion system according to claim 1, wherein when the thrust force command value is reduced in a state in which the motor generator is transmitting power to the propulsion propeller, the processing circuit controls the power converter to reduce the driving force generated by the motor generator while maintaining the engine speed at a current speed.

4. 3. The propulsion system according to claim 1, wherein, when the thrust force command value is the reference value, the processing circuit controls the engine to rotate at a speed higher than a speed corresponding to the thrust force command value, and controls the power converter to generate power in the generator using surplus driving force output from the engine.

5. 3. The propulsion system according to claim 1, wherein the engine is a gas engine that generates driving force using fuel including a fuel gas obtained by vaporizing a liquefied gas.

6. an engine mechanically connected to the propulsion propeller and having a rotation speed controlled in accordance with a thrust command value; a generator mechanically connected to the engine and capable of generating electricity by utilizing a driving force of the engine; a power converter electrically connected to the generator; A control program for a ship including a controller for controlling the engine and the power converter, The control program causes the controller to obtaining the thrust command value; determining whether the thrust command value is within a predetermined range lower than a reference value; and a control program for controlling the engine so as to maintain a rotation speed of the engine at the rotation speed at the reference value when the thrust force command value is within the predetermined range, and for controlling the power converter so as to increase the amount of power generated by the generator above the amount of power generated at the reference value.

7. an engine mechanically connected to the propulsion propeller and having a rotation speed controlled in accordance with a thrust command value; a generator mechanically connected to the engine and capable of generating electricity by utilizing a driving force of the engine; a power converter electrically connected to the generator; a controller for controlling the engine and the power converter, Acquire the thrust command value; determining whether the thrust command value is within a predetermined range lower than a reference value; a control method for controlling the engine so as to maintain a rotation speed of the engine at a rotation speed at the reference value when the thrust force command value is within the predetermined range, and for controlling the power converter so as to increase an amount of power generated by the generator above the amount of power generated at the reference value.

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