Ship hybrid power management method based on cooperation of axle power generation and lithium battery

Abstract

The invention relates to the technical field of ship power system control, in particular to a ship hybrid power management method based on shaft power generation and lithium battery collaboration, which comprises the following steps: acquiring load demand power of a ship power grid, output power of a shaft power generation system, a charge state of a lithium battery system and a rotating speed of a ship main engine in real time; adaptively deciding a current system operation mode; calculating a real-time power difference between the load demand power and the output power of the axle power generation system; generating a target charging and discharging power for the lithium battery system; a safe instruction charging and discharging power is obtained; and controlling the lithium battery system to execute the instruction charging and discharging power, and controlling the axle power generation system to operate according to the target of the current mode. Through precise power scheduling and adaptive switching of system operation modes, the ship power system is ensured to always operate in a state with optimal energy efficiency under different working conditions.

Description

Technical Field

[0001] This invention relates to the field of ship power system control technology, and in particular to a ship hybrid power management method based on shaft-driven power generation and lithium battery coordination. Background Technology

[0002] Traditional shipboard electrical systems typically use independent diesel generator sets to power all shipboard loads. To improve energy efficiency, some modern ships have adopted shaft generator systems (SGS), which utilize the surplus power of the ship's main propulsion engines to generate electricity. However, the output power of a shaft generator system is strongly correlated with the main engine speed (i.e., ship speed), exhibiting a rigid power output. When the ship is sailing at low speeds, maneuvering, or encountering rough sea conditions, the main engine speed decreases and fluctuates drastically, causing the output power of the shaft generator system to decrease and become unstable, making it difficult to meet the power and frequency requirements of the ship's electrical grid. In such cases, auxiliary diesel generator sets still need to be started, failing to fully realize their energy-saving potential.

[0003] While existing technologies employ batteries for auxiliary power supply, these are mostly limited to simple power supplementation or backup, failing to fundamentally address the issue of deep synergy between shaft-driven power generation systems and energy storage systems. Specific technical problems include: Response and power matching problem: The power output of the shaft-driven generator system passively depends on the main engine operating conditions, while the ship's electrical load demand changes actively, resulting in a real-time mismatch between the two. Existing solutions lack a mechanism that can accurately predict and coordinate the power difference between the two in real time.

[0004] The problem of simplistic energy dispatch strategies: Existing energy management strategies are mostly based on simple rules (such as constant voltage and frequency control) or do not fully consider the multimodal characteristics of ship navigation conditions (such as normal navigation, maneuvering, berthing and departure, loading and unloading, etc.). Under different operating conditions, the priorities and operational objectives of the shaft-driven power generation system, lithium battery system, and loads should be adjusted, but existing strategies lack this adaptive capability.

[0005] Lifespan and safety issues of lithium battery systems: The charge / discharge rate, depth of charge, and cycle life of lithium batteries directly affect their lifespan and safety. Existing solutions often fail to consider the real-time state of the lithium battery (such as State of Charge (SOC), State of Health (SOH), and temperature) as core control parameters when coordinating power distribution. This can lead to the lithium battery operating in an excessively stressed range, accelerating its performance degradation.

[0006] Therefore, there is an urgent need for an intelligent power management method that can deeply integrate ship operating conditions, achieve optimal coordination between shaft power generation and lithium batteries, and ensure system safety and economy. Summary of the Invention

[0007] In order to achieve the above purposes, the application provides a ship hybrid power management method based on shaft generator and lithium battery cooperation, comprising the following steps: Real-time collection of load demand power of the ship power grid, output power of the shaft generator system, state of charge of the lithium battery system and rotating speed of the ship main engine; Adaptive decision of the current system operation mode according to the rotating speed change trend of the ship main engine and the load demand power change trend of the ship power grid, wherein the system operation mode at least includes the high-efficiency cruising mode with power surplus and the maneuvering operation mode with power fluctuation; Calculation of the real-time power difference between the load demand power and the output power of the shaft generator system; Generation of a target charge-discharge power for the lithium battery system based on the decision of the system operation mode and the state of charge of the lithium battery system, wherein in the high-efficiency cruising mode, the target charge-discharge power is generated according to the real-time power difference and the state of charge by querying a pre-defined strategy, aiming at realizing the optimal system overall energy efficiency; in the maneuvering operation mode, the shaft generator system outputs a stable power, and the whole or most of the real-time power difference is allocated to the lithium battery system as the target charge-discharge power, aiming at maintaining the stability of the ship power grid frequency; Determination of the current allowed maximum charge-discharge power capacity of the lithium battery system according to its real-time internal state, and limitation of the target charge-discharge power within the power capacity range to obtain a safe instruction charge-discharge power; Control of the lithium battery system to execute the instruction charge-discharge power, and control of the shaft generator system to operate according to the target of the current mode.

[0008] Preferably, the adaptive decision of the current system operation mode according to the rotating speed change trend of the ship main engine and the load demand power change trend of the ship power grid specifically includes: Pre-analysis of the historical data of typical ship navigation conditions to statistically obtain the main engine rotating speed change rate threshold and the power grid power change rate threshold for distinguishing different conditions; Continuous calculation of the change rate of the current ship main engine rotating speed and the change rate of the power grid load demand power; Comparison of the two calculated change rates with the pre-set thresholds: if both of them continuously fall below the corresponding thresholds, it is determined that the ship is in a stable navigation state, and the high-efficiency cruising mode is decided; if any of the change rates exceeds the corresponding threshold, it is determined that the ship is in a disturbance state of speed change or load change, and the maneuvering operation mode is decided.

[0009] Preferably, the system operation mode further includes a port silent mode. The step of running the adaptive decision system mode further comprises: detecting the ship main engine speed and the shaft generator output power; when the main engine speed is zero and the shaft generator output power is continuously zero for a preset time length, deciding that the port is in the silent mode; In the port silent mode, the step of generating the target charge-discharge power is: setting the target charge-discharge power as a discharge power value equal to the load demand power size of the ship power grid.

[0010] Preferably, in the high-efficiency cruising mode, the target charge-discharge power is generated according to the real-time power difference and the state of charge by querying a pre-defined strategy, and the construction method of the pre-defined strategy comprises: In the system design stage, an energy flow simulation model of the ship hybrid power system is established; In the model, a series of different real-time power difference conditions and a series of different lithium battery system state of charge conditions are set; Taking the highest comprehensive efficiency of the entire ship power system and the minimum cycle life attenuation of the lithium battery system as a multi-objective optimization function, a multi-objective optimization algorithm is used to calculate an optimal lithium battery system power reference value under each power difference and state of charge combination; All combinations and their corresponding optimal power reference values are stored as a multi-dimensional database, which is the pre-defined strategy for online query during runtime.

[0011] Preferably, in the maneuvering operation mode, a stable power is output by the shaft generator system, and the determination method of the stable power comprises: A forward-backtracking sliding time window is set; A historical data sequence of the shaft generator output power in the time window is obtained; The historical data sequence is subjected to digital filtering processing to smooth out short-term violent fluctuations; The arithmetic mean or time-weighted mean of the filtered data sequence is taken as the stable power value that the shaft generator system should maintain.

[0012] Preferably, the method further comprises a coordinated start-stop control step of the diesel generator set: After the instruction charge-discharge power is generated, it is judged whether the instruction exceeds the actual physical limit of the lithium battery system; If the instruction charge-discharge power is a discharge power and its absolute value exceeds the absolute maximum discharge power that the lithium battery system can provide in the current state, a diesel generator set start signal is generated; start the diesel generator set and make it grid-connected, undertake a part of power shortage, and recalculate the real-time power difference, regenerate the target charge-discharge power of the lithium battery system based on the new power difference and the strategy of the current mode.

[0013] Preferably, the maximum charge-discharge power capability currently allowed by the lithium battery system is determined according to the real-time internal state thereof, wherein the real-time internal state includes battery temperature and internal resistance change trend; The method for determining the maximum charge-discharge power capability comprises: The temperature and voltage and current change of each battery module are detected in real time by the battery management system to estimate the internal impedance of the battery system; Based on the battery characteristic curve calibrated in advance through experiments, the curve reflects the peak charge-discharge power allowed by the battery at different temperatures and internal resistance levels to ensure safety and service life; The maximum instantaneous allowed charge power and the maximum instantaneous allowed discharge power of the lithium battery system at the current time are calculated by substituting the currently detected temperature and internal resistance estimation value into the characteristic curve.

[0014] Preferably, the method for establishing the battery characteristic curve calibrated in advance through experiments comprises: A representative sample of the lithium battery system is tested in a laboratory environment chamber; The temperature of the environment chamber is controlled so that the battery sample is at a series of different temperature points; At each temperature point, the battery sample is set at different state of charge points; At each temperature and state of charge combination, a pulse current of different amplitude is applied for charge-discharge test, and the voltage response of the battery is measured; Whether the pulse power is acceptable is determined according to whether the voltage change exceeds a safety window, so as to determine the maximum charge-discharge power allowed at the working point; The correspondence between all temperatures, state of charge and maximum allowed power is recorded to form a database for interpolation query, i.e. the battery characteristic curve.

[0015] Preferably, after the real-time acquisition step, the method further comprises a step of data preprocessing on the acquired raw data; The data preprocessing comprises the following sub-steps: A moving average filtering algorithm is used to smooth the load demand power, the output power of the shaft generator system and the main engine speed data to suppress measurement noise; Adopting the amplitude limiting filter method, each sampling value is compared with the previous sampling value, if the difference exceeds the reasonable limit value calculated according to the maximum possible change rate of the physical system, it is determined as abnormal data and is rejected, and the previous normal value or predicted value is replaced.

[0016] Preferably, the control of the shaft generator system according to the target operation of the current mode, in particular: By sending a set point signal to the excitation regulator of the shaft generator system; In the high-efficiency cruise mode, the set point signal is optimized to calculate the target of making the shaft generator system operate near its highest efficiency point; In the maneuvering operation mode, the set point signal is a constant power value or a constant voltage frequency value within the safe working range of the shaft generator system, to preferentially ensure the stability of the output.

[0017] The beneficial effects of the present application are: 1. The present application acquires the data of the load demand power of the ship power grid, the output power of the shaft generator system, the state of charge of the lithium battery system, etc. in real time, and combines the ship main engine speed change trend and the power grid load demand power change trend, to adaptively decide the system operation mode. On this basis, the power difference between the shaft generator system and the ship power grid can be coordinated in real time and accurately, and the mismatch between the two is solved. By calculating the real-time power difference between the load demand and the output power of the shaft generator system, the charging and discharging power of the lithium battery system is adjusted in real time, the system power is balanced, and the response ability of the system is significantly improved.

[0018] 2. The present application provides an adaptive energy scheduling strategy, for different navigation conditions, the system intelligently decides according to the current state of the ship, adjusts the operation mode of the system. In the high-efficiency cruise mode, the system takes the energy efficiency optimization as the target, to ensure the efficient operation of the ship; in the maneuvering operation mode, the system prioritizes maintaining the stability of the power grid frequency, and adjusts the power output. The implementation of this strategy overcomes the energy management method based on simple rules in the existing scheme, and has higher adaptability and flexibility.

[0019] 3、In the application, the charging and discharging process of the lithium battery is not only scheduled according to the real-time power difference, but also considers the real-time parameters such as the state of charge (SOC), the state of health (SOH) and the temperature of the lithium battery system. The system calculates the maximum charging and discharging power capability of the lithium battery according to the real-time internal state of the battery, avoids excessive charging and discharging of the lithium battery, thereby effectively prolongs the service life of the battery and improves the safety of the system. In addition, by pre-calibrating the battery characteristic curve, the application can accurately calculate the maximum safe charging and discharging power of the battery under each state, avoiding the problem that the lithium battery may run in a stress excessive interval in the traditional scheme, and reducing the risk of battery performance degradation. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0021] Fig. 1 The step flow chart of the method of the application; Fig. 2 The step flow chart of the method for determining the maximum charging and discharging power capability of the method of the application; Fig. 3 The step flow chart of the method of the application for controlling the shaft-mounted generator system to operate according to the target of the current mode. DETAILED DESCRIPTION

[0022] The application will be described in detail below in combination with the drawings and specific embodiments. It should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and other alternative ways can also be used by those skilled in the art to implement some known technologies; and the drawings are only used to more specifically describe the embodiments, and are not intended to specifically limit the application.

[0023] Please refer to Figs. 1-3 The embodiment of the application provides a ship hybrid power management method based on shaft-mounted generator and lithium battery cooperation. The system detects the load demand power of the ship power grid, the output power of the shaft-mounted generator system, the state of charge (SOC) of the lithium battery and the speed of the ship main engine in real time through sensors. These data provide an information basis for subsequent decision-making, ensuring that the system can accurately schedule according to the actual operation of the ship.

[0024] According to the trend of the ship's main engine speed and the change of the power grid load demand, the system automatically determines the current operation mode. It mainly includes two modes: when the ship is in good sailing state and the speed is stable, the system enters "high-efficiency cruising mode"; when the speed fluctuates or the ship is in maneuvering operation, the system enters "maneuvering operation mode". These two modes are respectively suitable for different working conditions, ensuring that the system can flexibly adjust the operation strategy according to the actual demand.

[0025] The system calculates the current power difference according to the real-time difference between the power grid load demand power and the shaft-mounted power generation system output power. In the "high-efficiency cruising mode", the system gives priority to overall energy efficiency optimization, queries the pre-defined strategy to generate target charging and discharging power, and tries to balance the power difference through lithium batteries as much as possible; in the "maneuvering operation mode", the system allocates all or most of the power difference to lithium batteries to stabilize the power grid frequency, ensuring that the ship can still operate stably under complex conditions.

[0026] To ensure the safety of lithium batteries and prolong their service life, the system monitors the state of health (SOH), state of charge (SOC), temperature and other parameters of lithium batteries in real time. Based on these real-time data, the system calculates the maximum charging and discharging power capacity allowed by lithium batteries. If the target charging and discharging power exceeds the safe operating range of lithium batteries, the system will automatically adjust to ensure that the charging and discharging power does not exceed the maximum safe capacity of lithium batteries, thereby avoiding excessive charging and discharging and reducing the risk of battery aging.

[0027] The system adjusts the charging and discharging power according to the safe instruction, schedules the lithium battery system to perform charging and discharging operations, and controls the shaft-mounted power generation system to operate according to the target of the current mode, maintaining the stability and efficiency of the ship's power system. Through precise power scheduling, the system avoids the power fluctuations and energy waste that may occur in traditional solutions.

[0028] Through precise power scheduling and adaptive switching of system operation modes, the system ensures that the ship's power system always operates in the most energy-efficient state under different conditions. By coordinating the power output of the shaft-mounted power generation and lithium battery systems in real time, the system avoids instability of the ship's power grid frequency, especially under maneuvering operation or complex sea conditions.

[0029] In one possible implementation, the system analyzes historical data of typical ship sailing conditions to obtain the changes of main engine speed and power grid load demand power under different conditions. These historical data include the actual performance of the ship under different speeds and load conditions. Through statistical analysis of these data, the system determines the speed change rate threshold and power grid power change rate threshold for distinguishing different conditions. The main engine speed change rate threshold represents a small range of fluctuations in the speed change amplitude under normal operating conditions, while the power grid power change rate threshold represents the maximum acceptable range of power grid load fluctuations.

[0030] The system continuously detects the real-time data of the ship's main engine speed and the power demand of the power grid load, and calculates the rate of change of the two parameters. The speed change rate represents the difference between the current time and the previous time, and the power demand of the power grid load change rate represents the fluctuation amplitude of the power demand of the power grid. By calculating the two change rates, the system can track the current running state of the ship in real time, and judge whether it has entered a steady state or a disturbance.

[0031] The calculated speed change rate and power demand of the power grid load change rate are compared with the preset threshold. When both change rates are continuously below their respective thresholds, it indicates that the ship is in a smooth sailing state, and the system will judge the current sailing condition as stable and decide on the high-efficiency cruising mode; if any change rate exceeds its corresponding threshold, it indicates that the main engine speed or the power demand of the power grid load has fluctuated greatly, and the ship may be in a variable speed or variable load disturbance state, at which time the system will switch to the maneuvering mode.

[0032] The adaptive decision-making method based on change rate threshold not only ensures the efficient operation of the ship's power system under different conditions, but also greatly improves the stability and adaptability of the system, optimizes the power management strategy, and ensures the efficient and safe use of energy.

[0033] In one possible implementation, the system continuously detects the ship's main engine speed and the output power of the shaft-mounted power generation system. These two parameters can effectively reflect the running state of the ship, especially whether the main engine is stopped and whether the power generation system is working normally. When the ship is parked in the port, the speed of the main engine is usually zero, and the output power of the shaft-mounted power generation system may also be zero. At this time, the system monitors these two key indicators in real time to determine whether the ship is in a stationary state.

[0034] When the main engine speed is detected to be zero and the output power of the shaft-mounted power generation system is continuously zero for a duration exceeding the preset time, the system automatically determines that the ship has completely docked and is no longer generating power. At this time, the system switches to the port silent mode. The core purpose of the port silent mode is to reduce the noise and pollution of the ship to the surrounding environment when it is parked in the port, especially to reduce the operating burden of the ship's engine and generator.

[0035] In the port silent mode, the working mode of the ship's power system is different from other sailing modes. The system no longer needs to provide additional power through the main engine or the shaft-mounted power generation system. On the contrary, the system will meet the load demand of the ship's power grid through the lithium battery system. In order to ensure the stable power supply of the ship's power grid, the system will set the target charge and discharge power to be equal to the load demand power of the ship's power grid, and the power direction will be discharge. That is, the lithium battery is in a discharge state at this time, providing the required power to the power grid.

[0036] The port silent mode not only provides an environmentally friendly and intelligent berthing power management solution for ships, but also improves the energy utilization efficiency of the system, reduces environmental pollution, and has significant economic and environmental double benefits.

[0037] In one possible implementation, during the system design phase, an energy flow simulation model of the ship's hybrid power system needs to be established first. This model is used to simulate the power flow under various operating conditions, including the energy conversion process between the main engine, shaft generator system, and lithium battery system. The simulation model needs to cover the operating conditions of the ship so that the power demand and supply of each component can be accurately predicted.

[0038] In the simulation model, a series of different real-time power difference conditions and state of charge conditions of the lithium battery system need to be defined. Real-time power difference refers to the difference between the actual power demand of the ship and the power that the power generation system can provide, and the state of charge refers to the current charge level of the lithium battery. These conditions will have a direct impact on the operation of the ship's power system under different operating conditions.

[0039] To ensure efficient operation of the system, a multi-objective optimization method is used when setting the optimization target. Under each pair of power difference and state of charge conditions, the goal is to maximize the overall efficiency of the entire ship power system while minimizing the cycle life degradation of the lithium battery system. The overall efficiency takes into account factors such as energy conversion efficiency and load balancing of the power generation system, while the cycle life degradation is related to the depth and frequency of lithium battery charging and discharging. The multi-objective optimization algorithm can calculate the optimal lithium battery power reference value by balancing these two objectives.

[0040] After obtaining the optimal power reference value under each combination of conditions, these results are stored in a multi-dimensional database. The database records all possible combinations of power difference and state of charge, and provides the corresponding optimal power reference value for each combination. This database is the pre-defined strategy, which can be quickly queried according to real-time conditions during actual operation and generate the target charging and discharging power.

[0041] Through precise simulation modeling, multi-objective optimization, and real-time query mechanism, not only the operation efficiency of the ship's power system is improved, but also the service life of the lithium battery is effectively prolonged, which has strong practical application value and technical advantages.

[0042] In one possible implementation, to achieve stable control of power, a sliding time window needs to be set first to backtrack historical data over a certain period of time. In this window, the system can obtain the power output data of the shaft generator system within a certain time range. The size of the window depends on the operating characteristics of the ship and the response speed of the system, and usually needs to be optimized according to actual conditions.

[0043] After setting the time window, the system will collect the power output history data sequence of the shaft generator system within the window. These data reflect the power fluctuation of the power generation system within a certain time range. By collecting these data, the system can analyze the actual output power of the power generation system and develop appropriate stable power control strategies.

[0044] In order to eliminate short-term power fluctuations and avoid sudden disturbances to the system, the historical data sequence will be processed by digital filtering. The purpose of filtering is to remove short-term fluctuations in the data caused by transient fluctuations, equipment interference or external environmental changes, so that the remaining data is smoother and more stable. Common digital filtering methods include low-pass filtering, weighted averaging, etc.

[0045] The filtered data will be used to calculate the stable power value that the shaft generator system should maintain. Here we can use two methods: one is to calculate the arithmetic mean of the data sequence, that is, to add all data values and take their average; the other method is to use time-weighted average, that is, to calculate the average value according to the weight of different time points. Weighted average can better consider the impact of power changes in different time periods, especially for longer-term fluctuations with better smoothing effect.

[0046] Finally, the stable power value calculated through the above steps will be used as a control signal to instruct the shaft generator system to maintain this power output, ensuring the smooth operation of the system and the stable supply of power.

[0047] By combining historical data, digital filtering and weighted averaging, etc. Technical means not only ensures the power stability of the system in the mobile operation, but also effectively improves the energy utilization rate, equipment life and the stability of the overall system, has good practicality and economy.

[0048] In one possible implementation, in a hybrid power management system of a ship, according to the current operating state and load demand of the ship, the charging and discharging power instruction is first generated. This power value reflects the power that the lithium battery system needs to output in the current state to maintain the operation of the ship.

[0049] The system needs to check whether the generated charging and discharging power instruction exceeds the physical limit of the lithium battery, especially the discharging power. If the instruction is the discharging power and its absolute value exceeds the maximum discharging power that the lithium battery system can currently provide, measures need to be taken to avoid damage to the lithium battery due to excessive discharging.

[0050] When it is found that the lithium battery cannot meet the required discharging power, the system will generate a start signal for the diesel generator set. This signal triggers the start-stop control system of the diesel generator set to start the diesel generator set to supplement the power shortage of the power system.

[0051] Once a start signal is received, the diesel generator set will begin operation and connect to the power grid. The diesel generator set will cover a portion of the power deficit, ensuring that the ship's power needs are met and avoiding the risk of insufficient system power.

[0052] After the diesel generator set starts up and is connected to the grid, the system will recalculate the real-time power difference. At this time, the system needs to adjust the power supply strategy according to the new power difference to ensure that all power generation equipment (including lithium batteries and diesel generator sets) work together.

[0053] Based on the new power differential and the strategy for the current operating mode, the system will regenerate the target charge and discharge power of the lithium battery system. This adjustment will take into account the power already provided by the diesel generator set and ensure that the lithium battery system operates within a safe range, avoiding over-discharge.

[0054] This hybrid power management method based on the coordinated start-stop control of diesel generator sets can effectively solve the problem of insufficient power of lithium battery systems when operating under high load, improve the stability and economy of the power management system, and is an important technical means to improve the reliability and performance of ship power systems.

[0055] In one possible implementation, the battery management system (BMS) will monitor the temperature, voltage, and current changes of each battery module in the ship's lithium battery system in real time. Changes in temperature and current directly affect the internal resistance of the lithium battery, which changes with battery usage and environmental variations.

[0056] Based on temperature and current changes, the battery management system (BMS) estimates the internal impedance of the battery system using a specific algorithm. The internal resistance of a battery is a key factor affecting its charge and discharge performance. As the internal resistance increases, the battery's charge and discharge efficiency decreases, and it may even lead to overheating and damage. Therefore, real-time estimation of the battery's internal resistance helps determine the battery's current health status.

[0057] The battery's characteristic curve was obtained through experimental calibration. This curve represents the battery's allowable peak charge and discharge power at different temperatures and internal resistance levels. Based on data from multiple experiments and combined with the battery's chemical characteristics, this curve reflects the battery's maximum charge and discharge capacity under various operating conditions.

[0058] By substituting the real-time detected battery temperature and internal resistance estimates into the battery characteristic curve, the system interpolates to calculate the maximum allowable instantaneous charging power and maximum instantaneous discharging power of the lithium battery system at the current moment. Interpolation provides more accurate power capability values, ensuring the battery operates within safe limits.

[0059] Based on the maximum charge / discharge power calculated through interpolation, the battery management system adjusts the actual charge / discharge power of the lithium battery to ensure it does not exceed safety limits. This process can be flexibly adjusted according to the ship's load requirements and the system's operating mode to prevent the battery from being overloaded.

[0060] Determining the maximum charge and discharge power capability based on the real-time internal state of the lithium battery system not only improves the system's safety and battery lifespan, but also optimizes power management and enhances the system's reliability and adaptability.

[0061] In one possible implementation, a representative set of lithium battery samples is first selected in a laboratory environmental chamber to ensure that the performance of these battery samples represents the battery system used in actual ship applications. The environmental chamber can simulate different environmental conditions such as temperature and humidity to ensure the controllability and consistency of experimental conditions.

[0062] The temperature inside the environmental chamber is controlled to test battery samples at a range of different temperature points. By setting multiple temperature points, the operating conditions of the battery in different environments can be simulated, such as extreme conditions like high and low temperatures, to obtain the battery's performance under diverse climatic conditions.

[0063] At each different temperature point, the battery samples were tested at different states of charge (SOC). The state of charge determines the remaining capacity and electrochemical state of the battery, and testing the battery at different SOCs can reflect its response to different charge and discharge conditions during actual use.

[0064] Charge-discharge tests were conducted by applying pulsed currents of varying amplitudes under each combination of temperature and state of charge. Pulse current testing is a method of simulating rapid charge-discharge loads on a battery, which helps to study voltage changes and response speed during rapid energy release or absorption.

[0065] The battery's voltage response is measured, and the acceptable pulse power is determined based on whether the battery voltage change exceeds a set safety window. During charging and discharging, the battery voltage should be maintained within a safe range; excessively high or low voltage may affect battery performance or safety. This determination ensures that the battery's maximum charge and discharge power under different operating conditions does not exceed safety limits.

[0066] A database is created by recording the correspondence between all temperatures, states of charge, and maximum permissible power. This database will serve as the basis for subsequent interpolation queries to generate battery characteristic curves. These curves provide detailed data on the maximum permissible charge and discharge power of the battery under different ambient temperatures and states of charge.

[0067] By calibrating the battery characteristic curves through experiments, we can accurately determine the working limits of the battery under different environments and charging states, providing reliable data support for the ship's hybrid electric management system. This ensures the safety of the battery system while optimizing its performance, and has significant practical application value.

[0068] In one possible implementation, the raw data collected, such as load demand power, shaft-driven generator output power, and main engine speed, are often affected by measurement noise. This noise can interfere with subsequent analysis and decision-making. Therefore, a moving average filtering algorithm is first used to smooth these data. Specifically, by weighted averaging of data within a certain time window, errors caused by instantaneous fluctuations or noise are reduced. The moving average filter can effectively smooth the trend of data changes, thereby highlighting the true system changes and reducing the interference of measurement noise.

[0069] For potentially outlier data, further processing is required. Amplitude limiting filtering compares each sampled value with the previous sampled value to determine if its change exceeds a reasonable limit calculated based on the maximum possible rate of change of the physical system. If the change exceeds this limit, it is considered outlier data. Outlier data may be caused by factors such as measurement errors or sensor malfunctions, and directly using this data may affect subsequent decisions and analysis. To avoid this problem, amplitude limiting filtering removes these outliers and replaces them with previous normal or predicted values, thereby ensuring data consistency and accuracy.

[0070] In the amplitude-limiting filtering method, if the change of a data point from the previous data point exceeds the system's physical rate of change limit, the system will determine that the data is abnormal and remove it. The removed data will not participate in subsequent analysis and calculations, and will be replaced by the previous normal value or a value calculated through a prediction algorithm. This avoids distortion of the entire system's output due to an error in a single data point.

[0071] Data preprocessing, especially the application of moving average filtering and amplitude limiting filtering, can effectively improve the reliability, stability, and operational efficiency of shipboard hybrid electric management systems. This not only reduces the impact of data noise and outliers on system decision-making but also provides more accurate operational data for the shipboard electric system, thereby enhancing the overall system performance.

[0072] In one possible implementation, when the ship is in high-efficiency cruise mode, the goal is to operate the shaft-driven power generation system near its peak efficiency point. This is because in cruise mode, ships typically require a stable and efficient energy supply, and the power generation system needs to minimize energy losses and provide a stable output. By optimizing the setpoint signal, the system adjusts the generator's excitation current to bring the power generation system's operating state closer to its optimal efficiency region. This optimization calculation takes into account load demand, generator performance curves, and operating environment factors to ensure that the generator always operates within the range that provides maximum efficiency.

[0073] In maneuvering operation mode, a ship's power demands are typically quite unstable; therefore, the control system focuses on ensuring stable output power. In this mode, the setpoint signal is set to a constant power or voltage frequency value, which must remain within the safe operating range of the shaft-driven generator system. In this way, the system prioritizes the stability of the generator output, preventing excessive power fluctuations from affecting normal system operation, especially under rapidly changing load demands on the ship. This control method ensures stable and reliable operation of the generator system even under high or low load conditions.

[0074] In both of the aforementioned modes, the excitation regulator plays a crucial role. The excitation regulator adjusts the generator's excitation current based on the setpoint signal, thereby altering the generator's output characteristics. Through precise setpoint signal input, the regulator can effectively control the generator's output power or voltage, ensuring it meets the expected performance requirements in different operating modes.

[0075] By precisely adjusting the setpoint signal, the shaft-driven power generation system can operate efficiently in different modes, which not only optimizes energy efficiency and ensures system stability, but also improves the flexibility of ship operation and the long-term reliability of the equipment.

[0076] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy, characterized in that, Includes the following steps: The system collects data on the load power demand of the ship's electrical grid, the output power of the shaft-driven power generation system, the state of charge of the lithium battery system, and the rotational speed of the ship's main engine. Based on the rotational speed of the ship's main engine and the load demand power of the ship's electrical network, the current system operating mode is adaptively determined. The system operating mode includes at least a high-efficiency cruise mode with surplus power and a maneuvering mode with power fluctuations. Calculate the real-time power difference between the load demand power and the output power of the shaft-driven power generation system. The real-time power difference is one of the factors in determining the target charging and discharging power. Based on the system operating mode and the state of charge of the lithium battery system determined by the decision, a target charge and discharge power is generated for the lithium battery system; wherein, under the high-efficiency cruise mode, the target charge and discharge power is generated by querying a predefined strategy based on the real-time power difference and the state of charge, with the goal of achieving the optimal overall energy efficiency of the system; Under the aforementioned maneuvering operation mode, with the primary objective of maintaining the stability of the ship's electrical grid frequency, the shaft-driven power generation system is controlled to output a stable power, and all the real-time power difference is allocated to the lithium battery system as the target charging and discharging power. Based on the real-time internal state of the lithium battery system, determine its current maximum allowable charge and discharge power capability, and limit the target charge and discharge power within the range of the maximum charge and discharge power capability to obtain a safe command charge and discharge power. The instructions are executed to control the charging and discharging power of the lithium battery and to control the shaft-driven power generation system to operate according to the target of the current mode.

2. The ship hybrid power management method based on shaft-driven power generation and lithium battery synergy as described in claim 1, characterized in that, The adaptive decision-making of the current system operating mode based on the rotational speed variation trend of the ship's main engine and the load demand power variation trend of the ship's electrical network specifically includes: By analyzing historical data of typical ship navigation conditions in advance, the thresholds for the rate of change of main engine speed and the rate of change of power grid are statistically obtained to distinguish different operating conditions. Calculate the rate of change of the current ship's main engine speed and the rate of change of the power demand of the power grid load; The rate of change of the current ship's main engine speed and the rate of change of the power demand of the power grid are compared with preset thresholds respectively: if both are continuously lower than their corresponding thresholds, the ship is determined to be in a stable navigation state and the decision is made to enter the efficient cruise mode; if either rate of change exceeds the corresponding threshold, the ship is determined to be in a disturbance state of variable speed or variable load and the decision is made to enter the maneuvering operation mode.

3. The ship hybrid power management method based on shaft-driven power generation and lithium battery synergy as described in claim 2, characterized in that, The system operation modes also include the port silent mode; The steps of the adaptive decision-making system operation mode further include: detecting the ship's main engine speed and the output power of the shaft-driven power generation system; when the main engine speed is zero and the output power of the shaft-driven power generation system remains zero for a preset duration, the decision is made to enter the port silent mode; In the port silent mode, the step of generating the target charging and discharging power is as follows: the target charging and discharging power is set to be equal to the load power demand of the ship's electrical grid as the discharge power value.

4. The ship hybrid power management method based on shaft-driven power generation and lithium battery synergy as described in claim 1, characterized in that, In the high-efficiency cruise mode, the target charge / discharge power is generated by querying a predefined strategy based on the real-time power difference and the state of charge. The method for constructing the predefined strategy includes: During the system design phase, an energy flow simulation model of the ship's hybrid electric system is established; In the model, a series of different real-time power difference conditions and a series of different state-of-charge conditions of the lithium battery system are set; Using the overall efficiency of the ship's electrical system and the cycle life decay of the lithium battery system as multi-objective optimization functions, a multi-objective optimization algorithm is adopted to calculate an optimal reference value for the lithium battery system power under each power difference and state of charge combination. All combinations and their corresponding optimal lithium battery system power reference values ​​are stored in a multidimensional database, which is the predefined strategy and is used for online querying at runtime.

5. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, In the motorized operation mode, the shaft-driven power generation system is controlled to output a stable power, wherein the method for determining the stable power includes: Set a sliding time window that goes back forward; Obtain the historical data sequence of the output power of the shaft-driven power generation system within this time window; The historical data sequence is digitally filtered to smooth out short-term, drastic fluctuations. The arithmetic mean or time-weighted average of the filtered data sequence is taken as the stable power value that the shaft-driven power generation system should maintain.

6. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, The method also includes a coordinated start-stop control step for the diesel generator set: After generating the charge / discharge power command, determine whether the command exceeds the actual physical limits of the lithium battery system; If the commanded charge / discharge power is discharge power, and the absolute value of the discharge power exceeds the absolute maximum discharge power that the lithium battery system can provide in the current state, then a diesel generator set start signal is generated. The diesel generator set is started and connected to the grid to take on part of the power deficit. The real-time power difference is recalculated, and the target charge and discharge power of the lithium battery system is regenerated based on the new power difference and the current mode strategy.

7. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, The maximum allowable charge and discharge power capability of the lithium battery system is determined based on its real-time internal state, wherein the real-time internal state includes the battery temperature and internal resistance change trends. Methods for determining maximum charge and discharge power capability include: The battery management system monitors the temperature and voltage / current changes of each battery module in real time to estimate the internal impedance of the battery system. Based on the battery characteristic curves that have been experimentally calibrated in advance, these curves reflect the peak charge and discharge power that the battery is allowed to ensure safety and lifespan under different temperatures and internal impedance levels. Substitute the currently detected temperature and internal resistance estimates into the battery characteristic curve, and interpolate to calculate the maximum instantaneous allowable charging power and the maximum instantaneous allowable discharging power of the lithium battery system at the current moment.

8. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 7, characterized in that, The method for establishing the pre-calibrated battery characteristic curves includes: Representative samples of the lithium battery system were tested in a laboratory environmental chamber. The temperature of the environmental chamber was controlled to keep the battery samples at a series of different temperature points; At each temperature point, the battery samples were set at different states of charge points; Under each combination of temperature and state of charge, a charge-discharge test was conducted by applying a pulse current of different amplitudes, and the voltage response of the battery was measured. The acceptable power of the pulse is determined by whether the voltage change exceeds the safety window, thereby determining the maximum allowable charging and discharging power at that operating point. Record the correspondence between all temperatures, states of charge, and maximum permissible power to form a database for interpolation queries, which is the battery characteristic curve.

9. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, Following the real-time acquisition step, the method further includes a data preprocessing step for the acquired raw data. The data preprocessing includes the following sub-steps: A moving average filtering algorithm is used to smooth the load demand power, the output power of the shaft-driven generator system, and the main engine speed data. The amplitude limiting filtering method is used to compare each sampled value with the previous sampled value. If the difference exceeds the limit calculated based on the rate of change of the physical system, it is judged as abnormal data and removed, and replaced with the previous normal value or predicted value.

10. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, The control of the shaft-driven power generation system to operate according to the target of the current mode specifically includes: This is achieved by sending a setpoint signal to the excitation regulator of the shaft-driven power generation system. The setpoint signal is used to adjust the excitation current of the generator so that the operating state of the power generation system is close to the optimal efficiency range. In the high-efficiency cruise mode, the setpoint signal is optimized with the goal of making the shaft-driven power generation system operate near its highest efficiency point; In the aforementioned motorized operation mode, the setpoint signal is a constant power value or a constant voltage frequency value within the safe operating range of the shaft-driven power generation system, in order to prioritize ensuring output stability.

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