A Coordinated Control Strategy for Switching Between Gas-Electric Hybrid Power Modes in Ships

Abstract

This invention provides a hybrid power ship mode switching control strategy, which first divides the hybrid power operation into four modes: electric motor-only propulsion, gas turbine-only propulsion, combined gas turbine and electric motor propulsion, and charging propulsion. The main features of this strategy are: first, calculating the total torque demand required for ship operation; and then, based on the required torque and the state of charge (SOC) of the power battery, formulating mode switching control rules with the principle of optimizing gas turbine operating efficiency. When the operating conditions of the hybrid power system change and the mode switching conditions are met, the hybrid powertrain controller coordinates the switching of various components of the power system to the target mode. This invention, by formulating the target mode of the hybrid power system when operating conditions change based on the ship's required torque and the power battery, is beneficial for improving system operating efficiency, saving fuel, improving the operating performance of hybrid power ships, and extending the service life of the power battery.

Description

Technical Field

[0001] This invention relates to a control strategy for switching between gas-electric hybrid power modes in ships, and more particularly to a switching control method and system for hybrid power ships operating in multiple modes. Background Technology

[0002] In recent years, with the increasing prominence of global environmental and energy issues, as well as the rapid rise in international oil prices, developing new types of ships with low emissions and low fuel consumption has become the primary task for the development of the shipbuilding industry today.

[0003] Pure electric propulsion ships offer advantages such as good economy, maneuverability, safety, low noise, and low pollution, making them one of the future directions for research in marine power technology. However, due to limitations in power generation methods, power density, and energy storage technology, current pure electric propulsion ships cannot fully meet people's demands for speed, acceleration, and maneuverability, and their range is also constrained by battery capacity.

[0004] Hybrid power systems are a new type of marine propulsion developed to address the energy crisis and ship emissions problems. They combine the advantages of electric motors and traditional internal combustion engines, meeting the power requirements of ships while improving fuel economy and emissions. They also inherit the long driving range of traditional fuel-powered ships, making them the most promising low-emission, low-energy-consumption marine propulsion system today and representing an important direction for future ship development.

[0005] Hybrid gas-electric ships integrate gas engines and electric motors to propel the vessel. They possess two or more energy sources and coordinate the operation of each component through energy management strategies. By combining two or more power sources and one or more energy storage technologies, they switch between different operating modes according to the needs of the operating conditions to fully utilize the advantages of both gas engines and electric motors. This ensures power performance while also considering fuel economy and emissions, ultimately achieving optimal energy distribution.

[0006] Natural gas as an engine fuel represents a future trend in engine development, offering advantages such as being environmentally friendly, economical, and safe. However, due to current technological limitations, gas engines still suffer from drawbacks such as poor power response and insufficient power output.

[0007] Hybrid power technology for ships helps resolve the contradiction between energy issues and technological immaturity. It allows for the switching of hybrid ships between different operating modes based on the ship's sailing conditions and the operational status of its components, thus maximizing the advantages of the hybrid power system. However, if a reasonable mode-switching control strategy is not formulated during the switching process, the advantages of hybrid power in fuel economy and emissions cannot be fully realized. Instead, it may lead to frequent mode switching, impacting the ship's transmission system and reducing its lifespan. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of the aforementioned problems by providing a marine gas-electric hybrid power mode switching control strategy. Based on the torque demand during ship operation and the remaining charge of the power battery, and with the goal of optimizing the gas engine's operating efficiency, a reasonable mode switching control strategy is formulated for the hybrid power system when operating conditions change. This reduces ship exhaust emissions, saves fuel, accelerates the development of environmentally friendly and green ships, and improves the range of hybrid power vessels.

[0009] The objective of this invention is achieved as follows:

[0010] Hybrid ships with multiple functions

[0011] The energy switching control method under the new mode first identifies the torque demand of the hybrid power ship during operation; second, based on the characteristics of the power battery, the operating range of the power battery is divided into different regions according to the state of charge (SOC); finally, based on the control strategy, it is determined whether the operating state of the hybrid power system meets the mode switching conditions. If the hybrid power system meets the state switching conditions, a mode switching control request is sent to the powertrain controller, thereby controlling the various components of the system to switch to the target state and changing the operating state of the hybrid power system.

[0012] The torque demand of a ship during operation mainly includes the demand for driving torque and the torque demand for charging the power battery.

[0013] During ship navigation, the demand for driving torque is mainly determined by the position of the push rod based on the ship's navigation characteristic function.

[0014] When the power battery needs to be charged, it sends a charging request to the hybrid power system control assembly. The hybrid power control assembly determines the target power for the electric motor to operate as a generator based on the battery's SOC value, and converts the demand for charging power provided by the gas engine into a demand for charging torque.

[0015] To extend the lifespan of the power battery and ensure it operates within a high-efficiency range, the power battery is divided into several zones based on its State of Charge (SOC). (1) Unusable zone: SOC less than 15%; (2) Low-efficiency zone: SOC between 15% and 45% and SOC greater than 80%; (3) High-efficiency zone: SOC between 45% and 80%. Definition: 0 is the unusable zone; 1 is the 15%-45% low-efficiency zone; 2 is the high-efficiency zone; 3 is the low-efficiency zone greater than 80%.

[0016] The default initial mode of the marine hybrid power system is electric motor-only propulsion. Specific conditions for switching hybrid power modes are determined based on the total demand torque, state of charge (SOC), and the gas turbine steady-state efficiency MAP. In this mode-switching control strategy, the operating modes of the gas turbine and electric motor are primarily determined by optimizing the gas turbine's efficiency. Based on the drive torque demand, braking torque demand, charging torque demand, and the gas turbine steady-state efficiency MAP, the operating modes of the gas turbine and electric motor can be determined, thereby defining the system's operating state.

[0017] 1) The current operating mode is motor-driven.

[0018] When the total required torque is greater than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

[0019] When the total required torque is greater than the minimum auxiliary working torque of the electric motor, and SOC = SOC1, SOC2, or SOC3, the system switches to a combined gas engine and electric motor drive mode.

[0020] When the total required torque is greater than the minimum operating torque of the gas engine, and SOC = SOC0 or SOC1, switch to charging propulsion mode.

[0021] 2) The current operating mode is gas engine propulsion alone.

[0022] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to the motor-only propulsion mode.

[0023] When the total required torque is greater than the minimum auxiliary working torque of the electric motor, and SOC = SOC1, SOC2, or SOC3, the system switches to a combined gas engine and electric motor drive mode.

[0024] When the total required torque is greater than the minimum operating torque of the gas engine but less than the minimum auxiliary operating torque of the electric motor, and SOC = SOC0 or SOC1, switch to charging propulsion mode.

[0025] 3) The current mode involves the gas engine driving the vehicle independently and charging the power battery.

[0026] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC1, the system switches to electric motor-only propulsion mode.

[0027] When the total required torque is greater than the minimum operating torque of the gas engine but less than the minimum auxiliary operating torque of the electric motor, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

[0028] 4) The current mode is a combined drive of gas engine and electric motor.

[0029] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to the motor-only propulsion mode.

[0030] When the total required torque is less than the minimum auxiliary working torque of the electric motor, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

[0031] The aforementioned gas-electric hybrid power mode switching control strategy determines the minimum operating torque line of the gas engine and the minimum auxiliary operating curve of the electric motor on the gas engine's steady-state efficiency diagram based on the principle of minimizing efficiency loss. The optimal economic torque range of the gas engine is obtained by looking up a table based on the gas engine speed and the optimal economic characteristic curve of the gas engine. The optimal economic characteristic curve of the gas engine is an inherent characteristic curve of the gas engine. In the mode where the gas engine participates in operation, it is necessary to always ensure that the torque value output by the gas engine is within the optimal economic torque range of the gas engine.

[0032] If either the total driving torque demand or the charging torque demand changes, causing the system operating conditions to be invalid, it indicates that the current operating modes of the gas engine and electric motor can no longer optimize system efficiency. In this case, the mode switching management strategy will change the operating modes of the gas engine and electric motor based on the principle of optimal efficiency, thereby causing a state switch.

[0033] The aforementioned gas-electric hybrid power mode switching control strategy is characterized by prioritizing the demand for drive torque over the battery's demand for charging torque. For example, when the demand for drive torque exceeds the minimum auxiliary torque of the electric motor, requiring the electric motor to provide power, even if the battery is at SOC1 and needs charging, the battery must still operate in a discharging state so that the electric motor operates in drive mode to meet the power requirements.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] This invention discloses a gas-electric hybrid power ship system, including a gas engine, a reversible motor, a clutch, a power battery, a reducer, and a drive shaft. The system has a wide power range, meeting the power requirements of ships under various operating conditions. It enables the gas engine and reversible motor to operate in their high-efficiency range, reducing fuel consumption and improving the ship's economy and emissions. Simultaneously, it effectively improves the ship's dynamic response during navigation and enhances its performance during acceleration, deceleration, and berthing.

[0036] This invention provides a specific mode-switching control strategy for gas-electric hybrid power vessels under different operating conditions. It allows for the selection of a suitable operating mode based on actual power requirements and the vessel's navigation environment, enabling switching between multiple operating modes and effectively improving the efficiency of the vessel's hybrid power system. This solution not only meets the emission standards of different ports and sea areas but also effectively alleviates the contradiction between immature technology and increasingly stringent emission standards, improving both the vessel's economy and emissions performance.

[0037] This invention presents a rule-based mode switching control strategy for gas-electric hybrid power systems. The specific rules are derived from extensive engineering experience and have high engineering applicability. They can be directly used as a mode switching control strategy for hybrid power ships, reducing the initial manufacturing cost of hybrid power ships. Attached Figure Description

[0038] Figure 1 This is a system control flowchart during the mode switching process described in this invention;

[0039] Figure 2 This is a circular diagram showing the system mode switching direction described in this invention. In the diagram, T... 总 T represents the total torque demand; e_min T represents the minimum operating torque of the gas engine. m_ass SOC0 represents the minimum auxiliary operating torque of the motor; SOC0 is the unusable zone; SOC1 is the low efficiency zone of 15%-45%; SOC2 is the high efficiency zone; and SOC3 is the low efficiency zone of greater than 80%. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] To address the power conversion issues of marine gas-electric hybrid power systems under multiple modes, and to improve hybrid power efficiency, reduce fuel consumption, and extend the lifespan of hybrid power components, a mode switching control strategy for marine gas-electric hybrid power systems is proposed, mainly including the following steps:

[0042] Step 1) Identify the torque requirements of hybrid-powered vessels during operation.

[0043] Step 2) In order to extend battery life and optimize battery efficiency, the battery's operating range is divided into different regions according to the SOC value based on the characteristics of the power battery.

[0044] Step 3) Based on the established mode switching control strategy, determine whether the current state of the power system meets the switching conditions. If the state switching conditions are met, send a mode switching control request to the powertrain controller to control each component in the system to switch to the target state and change the operating state of the hybrid power system.

[0045] The gas-electric hybrid power mode switching control strategy requires calculating the total torque demand required by the ship during operation.

[0046] Requirements for drive torque

[0047] During ship navigation, the demand for driving torque is mainly determined by the position of the pushrod based on the ship's navigation characteristic function.

[0048] The torque requirement of the power battery

[0049] When the power battery needs to be charged, it sends a charging request to the hybrid power system control assembly. The hybrid power control assembly determines the target power for the electric motor to operate as a generator based on the battery's SOC value, and converts the demand for charging power provided by the gas engine into a demand for charging torque.

[0050] To extend the lifespan of the power battery and ensure it operates within a high-efficiency range, the power battery is divided into several zones based on its State of Charge (SOC). (1) Unusable zone: SOC less than 15%; (2) Low-efficiency zone: SOC between 15% and 45% and SOC greater than 80%; (3) High-efficiency zone: SOC between 45% and 80%. Definition: SOC0 is the unusable zone; SOC1 is the 15%-45% low-efficiency zone; SOC2 is the high-efficiency zone; SOC3 is the greater than 80% low-efficiency zone.

[0051] The default initial mode of the marine hybrid power system is electric motor-only propulsion. Specific conditions for switching hybrid power modes are determined based on the ship's total torque demand, SOC value, and the gas turbine steady-state efficiency MAP. In this mode switching control strategy, the operating modes of the gas turbine and electric motor are primarily determined by optimizing the gas turbine's efficiency. Based on the driving torque demand, braking torque demand, charging torque demand, and the gas turbine steady-state efficiency MAP, the operating modes of the gas turbine and electric motor can be determined, thereby defining the system's operating state.

[0052] 1) The current operating mode is motor-driven.

[0053] When the total required torque is greater than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

[0054] When the total required torque is greater than the minimum auxiliary working torque of the electric motor, and SOC = SOC1, SOC2, or SOC3, the system switches to a combined gas engine and electric motor drive mode.

[0055] When the total required torque is greater than the minimum operating torque of the gas engine, and SOC = SOC0 or SOC1, switch to charging propulsion mode.

[0056] 2) The current operating mode is gas engine propulsion alone.

[0057] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to the motor-only propulsion mode.

[0058] When the total required torque is greater than the minimum auxiliary working torque of the electric motor, and SOC = SOC1, SOC2, or SOC3, the system switches to a combined gas engine and electric motor drive mode.

[0059] When the total required torque is greater than the minimum operating torque of the gas engine but less than the minimum auxiliary operating torque of the electric motor, and SOC = SOC0 or SOC1, switch to charging propulsion mode.

[0060] 3) The current mode is charging propulsion.

[0061] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC1, the system switches to electric motor-only propulsion mode.

[0062] When the total required torque is greater than the minimum operating torque of the gas engine but less than the minimum auxiliary operating torque of the electric motor, and SOC = SOC2 / SOC3, the system switches to gas engine-only propulsion mode.

[0063] 4) The current mode is a combined drive of gas engine and electric motor.

[0064] When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to the motor-only propulsion mode.

[0065] When the total required torque is less than the minimum auxiliary working torque of the electric motor, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

[0066] Based on the principle of minimizing efficiency loss, the minimum operating torque line of the gas engine and the minimum auxiliary operating curve of the electric motor are determined on the steady-state efficiency diagram of the gas engine. The optimal economic torque range of the gas engine is obtained by looking up a table based on the gas engine speed and the optimal economic characteristic curve of the gas engine. The optimal economic characteristic curve of the gas engine is an inherent characteristic curve of the gas engine. In the mode where the gas engine participates in the operation, it is necessary to always ensure that the torque value output by the gas engine is within the optimal economic torque range of the gas engine.

[0067] If either the total driving torque demand or the charging torque demand changes, causing the system operating conditions to no longer be met, it indicates that the current operating modes of the gas engine and electric motor are no longer optimal for the hybrid power system's efficiency. In this case, the mode-switching management strategy will change the operating modes of the gas engine and electric motor based on the principle of optimal efficiency, thus triggering a state switch.

[0068] The marine gas-electric hybrid power system of this invention includes two independent drive systems: a gas engine and an electric motor. The engine and electric motor are combined in a power coupling device, thereby enabling individual and combined drive of the gas engine and electric motor. Each component of the hybrid power system sends its operating status to the hybrid power system master controller, which then performs corresponding mode switching according to a predetermined hybrid power system mode switching control strategy.

[0069] The hybrid power system mode switching control strategy described in this invention has a simple structure and is easy to apply to existing hybrid power ships. This hybrid power system mode switching control strategy can effectively reduce exhaust emissions, reduce fuel consumption, and extend the life of power system components without affecting power and driving range.

[0070] In summary, this invention discloses a hybrid power ship mode switching control strategy. This strategy first divides the hybrid power operation into four modes: electric motor-only propulsion, gas turbine-only propulsion, combined gas turbine and electric motor propulsion, and charging propulsion. The main features of this strategy are: first, calculating the total torque demand required for ship operation; and then, based on the required torque and the state of charge (SOC) of the power battery, formulating mode switching control rules with the principle of optimizing gas turbine operating efficiency. When the operating conditions of the hybrid power system change and the mode switching conditions are met, the hybrid powertrain controller coordinates the switching of each component of the power system to the target mode. This invention, by formulating the target mode of the hybrid power system when operating conditions change based on the ship's required torque and the power battery, is beneficial for improving system operating efficiency, saving fuel, improving the operating performance of hybrid power ships, and extending the service life of the power battery.

Claims

1. A coordinated control strategy for switching between gas-electric hybrid power modes in ships, characterized in that, Includes the following steps: Step 1) Identify the torque demand of hybrid-powered vessels during operation; Step 2) In order to extend battery life and optimize battery efficiency, the battery's operating range is divided into different regions according to the SOC value based on the characteristics of the power battery. Step 3) Based on the established mode switching control strategy, determine whether the current state of the power system meets the switching conditions. If the state switching conditions are met, send a mode switching control request to the powertrain controller to control each component in the system to switch to the target state and change the operating state of the hybrid power system; The default initial mode of the marine hybrid power system is the electric motor-only propulsion mode. The specific conditions for switching the hybrid power mode are determined based on the total torque demand of the ship, the SOC value, and the gas engine steady-state efficiency MAP diagram. In this mode switching control strategy, the operating modes of the gas engine and the electric motor are mainly determined by optimizing the efficiency of the gas engine. Based on the driving torque demand, braking torque demand, charging torque demand, and the gas engine steady-state efficiency MAP diagram, the operating modes of the gas engine and the electric motor can be determined, thereby determining the operating state of the system. In order to extend the life of the power battery and keep it in a high-efficiency operating range, the power battery is divided into several ranges according to the SOC: (1) unusable zone, SOC less than 15%; (2) low efficiency zone, SOC between 15% and 45% and SOC greater than 80%; (3) high efficiency zone, SOC between 45% and 80%; Definition: SOC0 is the unusable zone; SOC1 is the low efficiency zone of 15%-45%; SOC2 is the high efficiency zone; SOC3 is the low efficiency zone of greater than 80%. The system's operating status includes: 1) The current operating mode is motor-driven. When the total required torque is greater than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode; When the total required torque is greater than the minimum auxiliary working torque of the electric motor, and SOC = SOC1 or SOC2 or SOC3, switch to the combined drive mode of gas engine and electric motor. When the total demand torque is greater than the minimum operating torque of the gas engine, and SOC = SOC0 or SOC1, switch to charging propulsion mode; 2) The current operating mode is gas engine propulsion alone. When the total required torque is less than the minimum operating torque of the gas engine, and SOC = SOC2 or SOC3, switch to the electric motor-only propulsion mode. When the total demand torque is greater than the minimum working torque of the gas engine and less than the minimum auxiliary working torque of the electric motor, and SOC = SOC0 or SOC1, switch to charging propulsion mode. 3) The current mode is charging propulsion. When the total required torque is less than the minimum operating torque of the gas engine and SOC = SOC1, switch to the motor-only propulsion mode. When the total required torque is greater than the minimum operating torque of the gas engine and less than the minimum auxiliary operating torque of the electric motor, and SOC = SOC2 / SOC3, switch to gas engine-only propulsion mode; 4) The current mode is a combined drive of gas engine and electric motor. When the total required torque is less than the minimum auxiliary working torque of the electric motor, and SOC = SOC2 or SOC3, switch to gas engine-only propulsion mode.

2. The ship gas-electric hybrid power mode switching coordinated control strategy according to claim 1, characterized in that, Calculate the total torque required by the ship during operation; a) Demand for driving torque During ship navigation, the demand for driving torque is mainly determined by the position of the push rod based on the ship's navigation characteristic function; b) Torque requirements of the power battery When the power battery needs to be charged, it sends a charging request to the hybrid power system control assembly. The hybrid power control assembly determines the target power for the electric motor to operate as a generator based on the battery's SOC value, and converts the demand for charging power provided by the gas engine into a demand for charging torque.

3. The ship gas-electric hybrid power mode switching coordinated control strategy according to claim 1, characterized in that, Based on the principle of minimizing efficiency loss, the minimum operating torque line of the gas engine and the minimum auxiliary operating curve of the electric motor are determined on the steady-state efficiency diagram of the gas engine. The optimal economic torque range of the gas engine is obtained by looking up the table based on the gas engine speed and the optimal economic characteristic curve of the gas engine. The optimal economic characteristic curve of the gas engine is an inherent characteristic curve of the gas engine. In the mode in which the gas engine participates in the operation, it is necessary to always ensure that the torque value output by the gas engine is within the optimal economic torque range of the gas engine.

4. The ship gas-electric hybrid power mode switching coordinated control strategy according to claim 3, characterized in that, If either the total driving torque demand or the charging torque demand changes, causing the system operating conditions to be invalid, it indicates that the current operating modes of the gas engine and electric motor can no longer optimize the efficiency of the hybrid power system. In this case, the mode switching management strategy will change the operating modes of the gas engine and electric motor according to the principle of optimal efficiency, thereby causing a state switch.

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