An ammonia-electric hybrid power system for a ship based on the integration design of fuel cell and engine gas circuit

Abstract

The application aims to provide a ship ammonia-electric hybrid power system based on the integrated design of a fuel cell and an engine gas circuit, comprising an ammonia fuel engine, a double-fed induction motor, a propeller, a gear box, a diesel generator set, a fuel cell, an ammonia gas storage and supply system, a power transformation device, a ship power grid, and hydraulic elements, etc. The technical scheme of the application can realize the hybrid propulsion of the ammonia fuel engine and the double-fed induction motor, the coordinated power supply of the diesel generator set and the fuel cell, and the lithium battery, and further improves the whole-ship propulsion efficiency. The application proposes a gas circuit coordination scheme of the engine and the fuel cell, which can realize the complementary advantages of the work of the two, simplifies the gas circuit design redundancy, and improves the integration degree of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to a ship power system, in particular to a ship hybrid power system. BACKGROUND

[0002] At present, the ship power system mainly based on diesel engine has the disadvantages of high pollution, low energy consumption and high carbon emission, so it is urgent to seek a low-carbon and efficient power system to meet the increasingly stringent carbon reduction demand and adapt to the future low-carbon or even zero-carbon target.

[0003] Ammonia fuel, as a clean fuel, is widely used in the chemical industry. As a zero-carbon fuel, ammonia fuel has gradually attracted widespread attention in the field of ship power in recent years. Although the ship industry has proposed the concept of ammonia fuel engine, there is still no mature product due to technical limitations. On the one hand, the performance of ammonia fuel engine lacks comprehensive research, and on the other hand, there is no clear technical solution for matching the ammonia fuel engine with a power system. Therefore, the research and development of ammonia fuel engine is still in the preliminary stage, and the hybrid power system of ammonia fuel engine is still in the technical blank stage.

[0004] The ship hybrid power system has the advantages of both traditional internal combustion engine propulsion and pure electric propulsion. The hybrid power system has obvious advantages in comprehensive energy efficiency, energy saving and emission reduction, and vibration and noise. Compared with the pure electric propulsion system, a small capacity battery can meet the long endurance mileage, and the cost is low. The hybrid power system based on ammonia fuel engine can meet the requirements of zero-carbon power, and can also solve the problems of low efficiency at low load, difficult cold start and other problems of ammonia fuel engine. The introduction of the motor can improve the dynamic characteristics of the ammonia fuel engine and realize the complementary advantages of multiple power sources. The hybrid power system based on ammonia fuel engine will become one of the best power forms of future zero-carbon power. Therefore, it is of great significance to layout the intellectual property rights of ammonia fuel engine hybrid power system to occupy the international technology highland in advance and protect the key technology of ammonia fuel engine hybrid power. SUMMARY

[0005] The purpose of the present application is to provide a ship ammonia-electric hybrid power system based on fuel cell and engine gas path integrated design, which can realize the hybrid propulsion of ammonia fuel engine, motor, ammonia diesel engine set, energy storage device and fuel cell.

[0006] The purpose of the present application is achieved as follows:

[0007] The application is a ship ammonia-electric hybrid power system based on the integration design of fuel cell and engine gas circuit, characterized by comprising a variable pitch propeller, an ammonia engine, an ammonia diesel engine set, a double-fed induction motor, an ammonia fuel cell, a lithium ion battery, an electric grid, an ammonia storage tank, and an oxygen storage tank; the ammonia engine is connected to the double-fed induction motor and the variable pitch propeller through a clutch; the rotor excitation winding of the double-fed induction motor is connected to the output end of the ammonia fuel cell through a double-fed induction motor frequency converter; the stator winding of the double-fed induction motor is connected to the electric grid; the lithium ion battery is connected to the electric grid through a lithium ion battery inverter; the ammonia fuel cell is connected to the electric grid through an ammonia fuel cell inverter; and the ammonia diesel engine set is directly connected to the electric grid; the ammonia storage tank is connected to the ammonia fuel cell through a first switch stop valve, a pressure stabilizing valve, a fire retardant valve, and a seventh three-way valve first outlet; the ammonia outlet of the ammonia fuel cell is connected to the ammonia diesel engine set through a first fuel pump, an eighth three-way valve first outlet, and a second flowmeter; the oxygen storage tank is connected to the ammonia fuel cell through a second stop valve and a second flowmeter; a part of exhaust gas in the exhaust pipe of the ammonia diesel engine set enters the ammonia fuel cell through a third three-way valve second outlet and a second three-way valve first outlet; the exhaust gas generated by the ammonia fuel cell and the exhaust gas generated by the ammonia diesel engine set are collected into the exhaust pipe of the ammonia diesel engine set through a three-way valve; a part of the exhaust gas in the exhaust pipe passes through a third three-way valve first outlet, a purification device, a first heat exchanger, a second exhaust gas recirculation pump, and a sixth three-way valve to enter the air inlet pipe of the ammonia diesel engine set; after the air is compressed by a turbocharger of the ammonia diesel engine set, a part of the air enters the exhaust pipe through a fifth three-way valve second outlet, and a part of the air enters the air inlet pipe through a fifth three-way valve first outlet, a second heat exchanger, and a sixth three-way valve first outlet; and the exhaust gas in the exhaust pipe is discharged into the atmosphere through a turbine, a part of the exhaust gas is directly discharged into the atmosphere through a fourth three-way valve, and the other part of the exhaust gas enters the ammonia fuel cell through the fourth three-way valve and a second three-way valve.

[0008] The application can further comprise:

[0009] 1. In the starting mode, the frequency converter controls the double-fed induction motor to drag the ammonia fuel engine for starting, the power source of the double-fed induction motor is directly provided by the inverter-controlled ammonia fuel cell, the ammonia fuel required by the fuel cell in the electric grid enters the ammonia fuel cell through the ammonia storage tank, a first stop valve, a pressure stabilizing valve, a fire retardant valve, a seventh three-way valve, and a first flowmeter, in a cold environment, the ammonia diesel engine set is started first, a part of the exhaust gas generated by the exhaust pipe enters the ammonia fuel cell for preheating through a fourth three-way valve and a second three-way valve or a third three-way valve, after the fuel cell is preheated to a preset temperature, the ammonia fuel cell is started again.

[0010] 2. In the mechanical mode, the clutch is combined, the double-fed induction motor does not work, and the ammonia engine drives the variable pitch propeller through a gear box.

[0011] 3. In the electric propulsion mode, the doubly-fed induction motor is started, the clutch is disconnected, the ammonia engine is not working, the doubly-fed induction motor drives the variable pitch propeller, when the ship speed is low, the gearbox selects the high speed ratio gear, when the ship speed is high, the low speed ratio gear is selected; when the ship is at the shore or at the berth, the pitch of the variable pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the high speed ratio gear of the gearbox is selected.

[0012] 4. In the hybrid propulsion mode, the clutch is connected, the doubly-fed induction motor and the ammonia engine drive the variable pitch propeller through the gearbox, the doubly-fed induction motor is controlled by the ship power grid through the frequency converter, the ammonia engine works in the constant power mode or the optimal economic curve mode, and the engine working interval is optimized by adjusting the pitch ratio of the variable pitch propeller and the speed of the doubly-fed induction motor.

[0013] 5. In the power generation mode, the clutch is connected, the ammonia engine drives the doubly-fed induction motor to generate power, and a part of the power drives the variable pitch propeller through the gearbox, the doubly-fed induction motor includes two ways to feed the power grid, when the ammonia engine speed is adjusted to the rated speed and the 50HZ frequency power is generated, the power is directly fed to the ship power grid, at this time the frequency converter does not work, and the doubly-fed induction motor works as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, the power is fed to the ship power grid through the voltage and frequency converter.

[0014] 6. The ship power grid includes a separate working mode and a joint mode, in the separate mode, according to the power demand of the ship power grid, the ammonia diesel engine group or the ammonia fuel cell or the lithium ion battery separately supplies power to the ship power grid; in the joint working mode, when the power demand of the ship is greater than that of one power generation source, two or three power generation sources are jointly supplied, at this time, according to the energy management strategy, the power output of each power generation source is optimized.

[0015] The advantages of the application are:

[0016] 1. The application provides a ship ammonia-electric hybrid power system based on fuel cell and engine gas path integrated design, which is provided with an ammonia fuel engine, a double-fed induction motor, a double-speed ratio gear box and a clutch, has a wide power coverage range and can meet the power demand of the ship under various working conditions, reduces the emission of pollutants and carbon dioxide and has obvious technical effects, that is, firstly, the double-fed induction motor can reduce the capacity of the frequency converter, compared with the PTO induction or synchronous motor provided in the traditional ship, the capacity of the frequency converter is reduced by 50%; meanwhile, since the ammonia fuel cell and the lithium ion battery are provided, the double-fed induction motor does not need to be provided with a starting generator set when starting and the alternating current required by the rotor winding of the double-fed induction motor is directly obtained from the ammonia fuel cell through the inverter frequency conversion, compared with the traditional double-fed induction motor, the double-fed induction motor is less in the AC-DC-AC conversion link, so that the energy transmission efficiency is improved. The design of the double-speed ratio gear box overcomes the problem that the double-fed induction motor has a small slip range and is difficult to meet the needs of the ship sailing at a low speed, and the design of the variable pitch propeller can avoid the problem that the double-fed induction motor has small torque at low speed, so that the demand for large torque at low speed sailing can be met and the propulsion efficiency of the power system is improved. The ammonia fuel engine and the double-fed induction motor can adjust the working space of the ammonia fuel engine through the double-fed induction motor, improve the working efficiency of the ammonia fuel engine, solve the problem that the high ignition point of the ammonia fuel leads to the difficulty in starting the high-power ammonia fuel engine, the ammonia fuel engine has insufficient combustion under low load working condition and poor dynamic characteristics, the double-fed induction motor can be used for torque coordination control through fast torque response to meet the sailing demand.

[0017] 2. The ship's power grid utilizes an ammonia-diesel generator set equipped with lithium-ion batteries and an ammonia fuel cell. The lithium-ion batteries can perform peak shaving and valley filling of the power grid, ensuring the ammonia-diesel generator set operates at its optimal efficiency point, thus improving the grid system efficiency. Simultaneously, the ammonia fuel cell, as one of the energy sources, can coordinate with the lithium-ion batteries to optimize the efficiency of the ammonia-diesel generator set, and can also optimize the operating point itself. This combined optimization approach improves the overall efficiency of the power grid and meets the grid's power demand. The specific technical effects are as follows: When grid power demand is low, the ammonia fuel cell and ammonia-diesel generator set operate in a high-efficiency range, with the remaining power charging the lithium-ion batteries. When grid power demand is high or exceeds the rated power of the ammonia-diesel generator set and ammonia fuel cell, the lithium-ion batteries discharge to meet the power demand, ensuring high-efficiency output from both the ammonia-diesel generator set and the ammonia fuel cell. The lithium-ion battery configuration leverages its high power output response to meet the dynamic power needs of the ship, thereby reducing operating fluctuations of the ammonia-diesel generator set and preventing increased engine emissions under extreme operating conditions. Furthermore, lithium-ion batteries and ammonia fuel cells can serve as backup power sources when diesel generators fail, meeting the requirements for black start in the power grid; the ammonia fuel cell is directly connected to the doubly fed motor through an inverter, making black start more reliable.

[0018] 3. The doubly-fed induction motor has two power feeding modes to the ship's power grid. First, when the ammonia-fueled engine operates at a constant speed, the ship can change speeds via variable pitch propellers, and the doubly-fed motor can be directly connected to the ship's power grid. Second, when both the ammonia-fueled engine and the variable-pitch propeller operate at variable speeds, the doubly-fed motor achieves grid connection by adjusting the frequency and phase of synchronous power generation in the rotor excitation windings via a frequency converter. Significant technical advantages can be seen in these two feeding methods. Both methods avoid power losses and rely solely on software control for grid connection. Furthermore, using a small-capacity frequency converter to control the doubly-fed induction motor rotor windings enables variable-speed power generation, improving power generation efficiency and cost. Selecting between these two modes allows for optimal efficiency optimization of the ammonia-fueled engine.

[0019] 4. This invention proposes a marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path. It achieves integrated design of the ammonia-diesel generator and ammonia fuel cell gas path, employing a shared ammonia fuel supply circuit to simplify the redundancy of the supply pipeline. Simultaneously, the exhaust gas generated by the fuel cell is introduced into the exhaust pipe of the ammonia-diesel generator, resulting in more efficient waste heat utilization and increased turbine work, which is beneficial for increasing compressed air and optimizing the performance of the ammonia-diesel generator. The exhaust gas recirculation circuit design can solve the problem of excessive nitrogen oxide emissions from the ammonia-diesel generator, while the cylinder bypass circuit can prevent compressor surge under partial load.

[0020] 5. Another advantage of the present application is that by introducing the exhaust gas after the turbine of the ammonia diesel engine set into the ammonia fuel cell preheating circuit, the cold start of the ammonia fuel cell can be realized without additional heat source, and the exhaust gas energy is reused.

[0021] 6. The ship hybrid power system provided by the present application is suitable for large ocean-going ship power systems, can meet the requirements of zero-carbon navigation, ensure low emission of pollutants such as nitrogen oxides, and ensure the endurance mileage of ocean navigation. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a structural schematic diagram of the present application. DETAILED DESCRIPTION

[0023] The present application will be described in more detail below with examples combined with the drawings:

[0024] Combined Figure 1The application discloses a ship ammonia-electric hybrid power system based on fuel cell and engine gas path integrated design, which comprises a variable pitch propeller 1, a gear box 2, a clutch 3, an ammonia engine 4, an ammonia diesel engine set 5, a double-fed induction motor 6, an ammonia fuel cell inverter 7, an ammonia fuel cell 8, a double-fed induction motor frequency converter 9, a lithium ion battery inverter 10, a lithium ion battery 11, three-way valves 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, an exhaust pipe 13, a turbocharger 14, flow meters 15a, 15b and 15c, switch stop valves 16a and 16b, an ammonia storage tank 17a, an oxygen storage tank 17b, a fire retardant valve 18, a pressure stabilizing valve 19, a fuel pump 20a, an exhaust gas recirculation pump 20b, a purification device 21, heat exchangers 22a and 22b and an air inlet pipe 23. The ammonia fuel engine 4 is mechanically connected with the double-fed induction motor 6 and the variable pitch propeller 1 through the clutch 3 in the gear box 2; the rotor excitation winding of the double-fed induction motor 6 is connected to the output end of the ammonia fuel cell 8 through the frequency converter 9, and the stator winding is directly connected to the power grid. The lithium ion battery 11 is connected to the power grid through the lithium ion battery inverter 10, the ammonia fuel cell 8 is connected to the power grid through the ammonia fuel cell inverter 7, and the ammonia diesel engine set is directly connected to the power grid 5. The ammonia fuel in the ammonia storage tank 17a enters the fuel cell 8 through the first outlet of the three-way valve 12g, the switch stop valve 16a, the pressure stabilizing valve 19 and the fire retardant valve 18. The ammonia outlet of the ammonia fuel cell 8 enters the ammonia diesel engine set 23 through the first outlet of the three-way valve 12h, the fuel pump 20a and the fuel flow meter 15c. The oxygen in the oxygen storage tank 17b enters the ammonia fuel cell 8 through the stop valve 16b and the flow meter 15b. Part of the exhaust gas in the exhaust pipe 13 of the ammonia diesel engine set enters the ammonia fuel cell through the second outlet of the three-way valve 12c and the first outlet of the three-way valve 12b, the exhaust gas generated by the ammonia fuel cell 8 and the exhaust gas generated by the ammonia diesel engine set 5 are collected into the exhaust pipe 13 through the three-way valve 12a. Part of the exhaust gas in the exhaust pipe 13 enters the air inlet pipe through the first outlet of the three-way valve 12c, the purification device 21, the heat exchanger 22a, the exhaust gas recirculation pump 20b and the three-way valve 12f, which is an exhaust gas recirculation loop. After the air in the environment is compressed by the turbocharger 14, part of the air enters the exhaust pipe through the second outlet of the three-way valve 12e, which is a cylinder bypass loop; part of the air enters the air inlet pipe 23 through the first outlet of the three-way valve 12e, the heat exchanger 22b and the first outlet of the three-way valve 12f. Most of the exhaust gas in the exhaust pipe 13 is discharged into the atmosphere through the turbine in the turbocharger 14, part of the exhaust gas is directly discharged into the atmosphere through the three-way valve 12d, and the other part of the exhaust gas enters the fuel cell through the three-way valve 12d and the three-way valve 12b, which is an ammonia fuel cell cold start loop.

[0025] In the embodiment, the ammonia fuel engine 4 is preferably a compression ignition engine, the ammonia diesel engine set 5 is preferably an ignition engine, and the lithium ion battery 11 is preferably a lithium iron phosphate battery with high power density and small volume weight.

[0026] The working modes of the present application mainly include the following modes

[0027] The starting mode is to start the ammonia fuel engine 4 by the double-fed induction motor 6 controlled by the frequency converter 9 when the ship is in the standby mode. The power source of the double-fed induction motor is directly provided by the ammonia fuel cell 8 controlled by the inverter 7. This setting can not only prevent the power shortage caused by the failure of the ship power grid, but also reduce the energy loss in the power transmission process. The ammonia fuel required by the fuel cell in the power grid enters the ammonia fuel cell through the ammonia storage tank 17a, the stop valve 16a, the pressure stabilizing valve 19, the fire retardant valve 18, the three-way valve 12g and the flow meter 15a. It should be noted that in cold environments, the ammonia diesel engine set 5 is started first at this time, and part of the exhaust gas generated by the exhaust pipe 13 enters the ammonia fuel cell through the three-way valves 12d, 12b or 12c for preheating. After the fuel cell is preheated to the appropriate temperature, the ammonia fuel cell is started.

[0028] In the mechanical mode, the clutch 3 is engaged, and at this time the double-fed induction motor 6 does not work, and the ammonia fuel engine 4 drives the variable pitch propeller 1 through the gear box 2.

[0029] In the electric propulsion mode, the double-fed induction motor 6 is started, the clutch 3 is disconnected, and the ammonia engine 4 does not work, and the double-fed induction motor 6 drives the variable pitch propeller 1, at this time the speed ratio of the gear box 2 can be selected according to the speed and pitch ratio. The control rule is that when the ship speed is low, the high speed ratio gear of the gear box 2 is selected at this time, and when the ship speed is high, the low speed ratio gear is selected; when the ship is at the shore or in the berth, the pitch of the variable pitch propeller 1 is reduced at this time to meet the speed range of the double-fed induction motor 6, and the speed ratio of the gear box 2 should also be selected as the high speed ratio gear.

[0030] In the hybrid propulsion mode, the clutch 3 is engaged, and the double-fed induction motor 6 and the ammonia fuel engine 4 jointly drive the variable pitch propeller 1 through the gear box 2. In this mode, the double-fed induction motor 6 is controlled by the ship power grid through the frequency converter 9. In this mode, the ammonia fuel engine 4 can work in the constant power mode or the optimal economic curve mode, and the engine working interval is optimized by adjusting the pitch ratio of the variable pitch propeller 1 and the speed of the double-fed induction motor 6.

[0031] In the power generation mode, the clutch 3 is engaged, and part of the power of the ammonia fuel engine 4 drives the double-fed induction motor 6 to generate electricity, and part of the power drives the variable pitch propeller 1 through the gear box 2. At this time, the double-fed induction motor 6 can feed power to the power grid in two ways. When the ammonia engine speed is adjusted to the rated speed to generate 50HZ frequency power, the power is directly fed to the ship power grid, and at this time the frequency converter 9 does not work, and at this time the double-fed induction motor 6 can work as an asynchronous motor; when the speed of the double-fed induction motor 6 is less than the rated speed, the power is fed to the ship power grid through the variable voltage and frequency converter 9.

[0032] The ship power grid includes ammonia diesel generator set 5, ammonia fuel cell 8, and lithium ion battery 11. The main working modes include a single working mode and a combined mode.

[0033] The single mode is that the ammonia diesel generator set 5, the ammonia fuel cell 8, or the lithium ion battery 11 supplies power to the ship power grid alone according to the power demand of the ship power grid. The combined working mode is that two or three of them supply power jointly when the power demand of the ship is greater than that of one power supply. At this time, the energy management strategy is used to optimize the power output of each power supply.

Claims

1. A marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path, characterized in that: The system includes a variable-pitch propeller, an ammonia engine, an ammonia-diesel generator set, a doubly-fed induction motor, an ammonia fuel cell, a lithium-ion battery, a power grid, an ammonia storage tank, and an oxygen storage tank. The ammonia engine is connected to the doubly-fed induction motor and the variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the output of the ammonia fuel cell via a doubly-fed induction motor inverter. The stator winding of the doubly-fed induction motor is connected to the power grid. The lithium-ion battery is connected to the power grid via a lithium-ion battery inverter, and the ammonia fuel cell is connected to the power grid via an ammonia fuel cell inverter. The ammonia-diesel generator set is directly connected to the power grid. The ammonia storage tank is connected to the ammonia fuel cell via a first shut-off valve, a pressure regulating valve, a flame-retardant valve, and the first outlet of a seventh three-way valve. The ammonia outlet of the ammonia fuel cell is connected to the ammonia-diesel generator set via a first fuel pump, the first outlet of an eighth three-way valve, and a second flow meter. The oxygen storage tank is connected to the ammonia fuel cell via a second shut-off valve and a second flow meter. The ammonia-diesel generator set... A portion of the exhaust gas in the exhaust pipe enters the ammonia fuel cell through the second outlet of the third three-way valve and the first outlet of the second three-way valve. The exhaust gas generated by the ammonia fuel cell and the exhaust gas generated by the ammonia diesel generator unit are collected through the three-way valve to the exhaust pipe of the ammonia diesel generator unit. A portion of the exhaust gas in the exhaust pipe passes through the first outlet of the third three-way valve, the purification device, the first heat exchanger, the second exhaust gas recirculation pump, and enters the intake pipe of the ammonia diesel generator unit through the sixth three-way valve. After the air is compressed by the turbocharger of the ammonia diesel generator unit, a portion enters the exhaust pipe through the second outlet of the fifth three-way valve, and a portion enters the intake pipe through the first outlet of the fifth three-way valve, the second heat exchanger, and the first outlet of the sixth three-way valve. The exhaust gas in the exhaust pipe is discharged into the atmosphere through the turbine, a portion is directly discharged into the atmosphere through the fourth three-way valve, and another portion enters the ammonia fuel cell through the fourth three-way valve and the second three-way valve. In startup mode, the inverter controls the doubly-fed induction motor to back-drive the ammonia fuel engine to start. The power source for the doubly-fed induction motor is directly provided by the ammonia fuel cell controlled by the inverter. The ammonia fuel required by the fuel cell in the grid enters the ammonia fuel cell through the ammonia storage tank, the first shut-off valve, the pressure regulating valve, the flame retardant valve, the seventh three-way valve, and the first flow meter. In cold environments, the ammonia diesel generator unit starts first. A portion of the exhaust gas produced by the exhaust pipe enters the ammonia fuel cell for preheating through the fourth three-way valve, the second three-way valve, or the third three-way valve. After the fuel cell is preheated to the preset temperature, the ammonia fuel cell starts.

2. The marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path as described in claim 1, characterized in that: In mechanical mode, the clutch engages, the doubly fed induction motor does not operate, and the ammonia engine drives the variable pitch propeller through the gearbox.

3. A marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path according to claim 1, characterized in that: In electric propulsion mode, the doubly-fed induction motor starts, the clutch disengages, the ammonia engine stops working, and the doubly-fed induction motor drives the variable-pitch propeller. When the ship's speed is low, the gearbox selects a high speed ratio gear, and when the ship's speed is high, it selects a low speed ratio gear. When the ship is docked or berthed, the pitch of the variable-pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the gearbox speed ratio is selected at a high speed ratio gear.

4. A marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path according to claim 1, characterized in that: In hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller via a gearbox. The doubly fed induction motor is controlled by the ship's electrical network via a frequency converter, and the ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the variable pitch propeller pitch ratio and the speed of the doubly fed induction motor.

5. A marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path according to claim 1, characterized in that: In power generation mode, the clutch engages, and part of the power from the ammonia fuel engine drives the doubly-fed induction motor to generate electricity, while another part of the power drives the variable-pitch propeller through the gearbox. The doubly-fed induction motor feeds power to the grid in two ways: when the ammonia engine speed is adjusted to the rated speed by adjusting the variable-pitch propeller pitch ratio to generate 50Hz frequency power, it directly feeds power to the ship's grid. At this time, the frequency converter does not work, and the doubly-fed induction motor acts as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, it feeds power to the ship's grid through a variable-voltage frequency converter.

6. A marine ammonia-electric hybrid power system based on the integrated design of fuel cell and engine gas path according to claim 1, characterized in that: Shipboard power grids include standalone and combined modes. In standalone mode, the ammonia-diesel generator, ammonia fuel cell, or lithium-ion battery supplies power to the shipboard power grid independently, based on the power demand of the shipboard power grid. In combined mode, when the shipboard power demand exceeds that of one of the generators, two or three generators supply power together, and the power output of each generator is optimized according to the energy management strategy.

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