A Hybrid Power Management Method for Ships Based on the Synergy of Shaft-Driven Generation and Lithium-ion Batteries

Abstract

This invention relates to the field of marine power system control technology, and particularly to a hybrid power management method for ships based on the synergy of shaft-driven power generation and lithium batteries. The method includes: real-time acquisition of the ship's power grid load demand, 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; adaptively determining the current system operating mode; calculating the real-time power difference between the load demand and the output power of the shaft-driven power generation system; generating a target charge / discharge power for the lithium battery system; obtaining a safe command charge / discharge power; controlling the lithium battery system to execute the command charge / discharge power, and controlling the shaft-driven power generation system to operate according to the target of the current mode. Through precise power scheduling and adaptive switching of system operating modes, the method ensures that the ship's power system always operates in an energy-optimal state under different operating 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:

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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

[0008] To achieve the above objectives, the present invention provides a hybrid power management method for ships based on the synergy of shaft-driven power generation and lithium batteries, comprising the following steps:

[0009] Real-time data collection of the ship's electrical grid load demand, shaft generator output power, lithium battery system state of charge, and main engine speed;

[0010] Based on the speed variation trend of the ship's main engine and the load demand power variation trend of the ship's electrical network, the current system operation mode is adaptively determined. The system operation mode includes at least a high-efficiency cruise mode with power surplus and a maneuver operation mode with power fluctuation.

[0011] Calculate the real-time power difference between the load demand power and the output power of the shaft-driven power generation system;

[0012] Based on the system operating mode and the state of charge of the lithium battery system determined by the decision, a target charge / discharge power is generated for the lithium battery system. Specifically, in the high-efficiency cruise mode, with the goal of achieving optimal overall system energy efficiency, the target charge / discharge power is generated by querying a predefined strategy based on the real-time power difference and the state of charge. In the maneuvering operation mode, with the primary goal of maintaining stable shipboard power grid frequency, the shaft-driven power generation system is controlled to output a stable power, and all or most of the real-time power difference is allocated as the target charge / discharge power to the lithium battery system.

[0013] 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 this power capability range to obtain a safe command charge and discharge power.

[0014] The lithium battery system is controlled to execute the commanded charging and discharging power, and the shaft-driven power generation system is controlled to operate according to the target of the current mode.

[0015] Preferably, the step of adaptively determining the current system operating mode based on the changing trends of the ship's main engine speed and the changing trends of the ship's electrical grid load demand specifically includes:

[0016] 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.

[0017] Continuously calculate the rate of change of the ship's main engine speed and the rate of change of the power demand of the power grid load;

[0018] The two calculated rates of change are compared with preset thresholds: if both are consistently below 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 its 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.

[0019] Preferably, the system operation mode further includes a port silent mode;

[0020] 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;

[0021] 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.

[0022] Preferably, 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:

[0023] During the system design phase, an energy flow simulation model of the ship's hybrid electric system is established;

[0024] 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;

[0025] Using the highest overall efficiency of the entire ship's electrical system and the minimum cycle life decay of the lithium battery system as the multi-objective optimization function, 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.

[0026] All combinations and their corresponding optimal power reference values ​​are stored in a multidimensional database, which is the predefined strategy and is used for online querying at runtime.

[0027] Preferably, 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:

[0028] Set a sliding time window that goes back forward;

[0029] Obtain the historical data sequence of the output power of the shaft-driven power generation system within this time window;

[0030] The historical data sequence is digitally filtered to smooth out short-term, drastic fluctuations.

[0031] 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.

[0032] Preferably, the method further includes a coordinated start-stop control step for the diesel generator set:

[0033] After generating the commanded charge / discharge power, determine whether the command exceeds the actual physical limits of the lithium battery system;

[0034] If the commanded charge / discharge power is the discharge power, and its absolute value 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.

[0035] 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.

[0036] Preferably, the step of determining the current maximum allowable charge and discharge power capability of the lithium battery system based on its real-time internal state includes the battery temperature and internal resistance change trends.

[0037] The method for determining the maximum charge / discharge power capability includes:

[0038] 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.

[0039] 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 at different temperatures and internal resistance levels.

[0040] Substitute the currently detected temperature and internal resistance estimates into the 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.

[0041] Preferably, the method for establishing the pre-calibrated battery characteristic curve includes:

[0042] Representative samples of the lithium battery system were tested in a laboratory environmental chamber.

[0043] The temperature of the environmental chamber was controlled to keep the battery samples at a series of different temperature points;

[0044] At each temperature point, the battery samples were set at different states of charge.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Preferably, after the real-time acquisition step, a data preprocessing step is further included for the acquired raw data;

[0049] The data preprocessing includes the following sub-steps:

[0050] 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 to suppress measurement noise.

[0051] The amplitude limiting filtering method is used to compare each sampled value with the previous sampled value. If the difference exceeds the reasonable limit calculated based on the maximum possible 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.

[0052] Preferably, controlling the shaft-driven power generation system to operate according to the target of the current mode specifically involves:

[0053] This is achieved by sending a setpoint signal to the excitation regulator of the shaft-driven power generation system;

[0054] 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.

[0055] In the 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 output stability.

[0056] The beneficial effects of this invention are:

[0057] 1. This invention adaptively determines the system's operating mode by real-time acquisition of data such as the ship's electrical grid load demand power, the output power of the shaft-driven generator system, and the state of charge of the lithium battery system, combined with the trends in the ship's main engine speed and the power grid load demand. Based on this, it can coordinate the power difference between the shaft-driven generator system and the ship's electrical grid in real time and accurately, solving the mismatch problem between the two. By calculating the real-time power difference between the load demand and the output power of the shaft-driven generator system, the charging and discharging power of the lithium battery system is adjusted in real time, achieving system power balance and significantly improving the system's responsiveness.

[0058] 2. This invention provides an adaptive energy scheduling strategy. For different navigation conditions, the system intelligently makes decisions based on the ship's current state and adjusts the system's operating mode accordingly. In the high-efficiency cruise mode, the system aims for optimal energy efficiency to ensure efficient ship operation; in the maneuvering operation mode, the system prioritizes maintaining stable grid frequency and adjusts power output accordingly. The implementation of this strategy overcomes the limitations of existing energy management methods based on simple rules, offering greater adaptability and flexibility.

[0059] 3. In this invention, the charging and discharging process of the lithium battery is not only scheduled based on real-time power differences, but also considers real-time parameters such as the state of charge (SOC), state of health (SOH), and temperature of the lithium battery system. The system calculates the maximum charging and discharging power capability of the lithium battery based on the real-time internal state of the battery, avoiding overcharging and discharging, thereby effectively extending the battery's lifespan and improving system safety. Furthermore, through pre-calibrated battery characteristic curves, this invention can accurately calculate the maximum safe charging and discharging power of the battery under each state, avoiding the problem of lithium batteries potentially operating in excessively stressful ranges in traditional solutions, and reducing the risk of battery performance degradation. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0061] Figure 1 This is a flowchart of the steps of the method of the present invention;

[0062] Figure 2 A flowchart illustrating the steps of the method for determining the maximum charge / discharge power capability according to the present invention;

[0063] Figure 3 This is a flowchart illustrating the steps of controlling the shaft-driven power generation system to operate according to the target mode of the present invention. Detailed Implementation

[0064] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0065] Please see Figures 1-3 This invention provides a hybrid power management method for ships based on the synergy of shaft-driven power generation and lithium batteries. The system uses sensors to monitor in real time the load power demand of the ship's power grid, the output power of the shaft-driven power generation system, the state of charge (SOC) of the lithium batteries, and the rotational speed of the ship's main engine. This data provides an information basis for subsequent decision-making, ensuring that the system can make precise scheduling based on the actual operating conditions of the ship.

[0066] Based on the changing trends of the ship's main engine speed and the fluctuations in grid load demand, the system automatically determines the current operating mode. There are two main modes: when the ship is in good navigation condition and the speed is stable, the system enters "high-efficiency cruise mode"; while during speed fluctuations or maneuvering, the system enters "maneuvering operation mode." These two modes are designed for different operating conditions, ensuring that the system can flexibly adjust its operating strategy according to actual needs.

[0067] The system calculates the current power difference based on the real-time difference between the power demand of the power grid and the output power of the shaft-driven generator system. In the "high-efficiency cruise mode," the system prioritizes overall energy efficiency optimization, queries predefined strategies to generate target charge and discharge power, and balances 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 the lithium batteries to stabilize the grid frequency and ensure that the ship can still operate stably under complex conditions.

[0068] To ensure the safety and extend the lifespan of lithium batteries, the system monitors parameters such as the battery's state of health (SOH), state of charge (SOC), and temperature in real time. Based on this real-time data, the system calculates the maximum allowable charge and discharge power of the lithium battery. If the target charge and discharge power exceeds the safe operating range of the lithium battery, the system will automatically adjust to ensure that the charge and discharge power does not exceed the maximum safe capacity of the lithium battery, thereby avoiding overcharging and discharging and reducing the risk of battery aging.

[0069] The system schedules the lithium battery system to perform charging and discharging operations according to safe commanded charging and discharging power, while simultaneously controlling the shaft-driven power generation system to operate according to the target mode of the current operation, maintaining the stability and efficiency of the ship's power system. Through precise power scheduling, it avoids the power fluctuations and energy waste problems that may occur in traditional solutions.

[0070] Through precise power scheduling and adaptive switching of system operating modes, the ship's electrical system is ensured to always operate in an energy-efficient state under different operating conditions. By coordinating the power output of the shaft generator and the lithium battery system in real time, instability of the ship's power grid frequency is avoided, especially during maneuvering or in complex sea conditions.

[0071] In one possible implementation, the system performs in-depth analysis of historical data from typical ship navigation conditions to obtain data on changes in main engine speed and grid load demand under different conditions. This historical data includes the ship's actual performance under different speeds and loads. Through statistical analysis of this data, the system determines threshold values ​​for the rate of change of engine speed and the rate of change of grid power to distinguish between different operating conditions. The main engine speed rate of change threshold represents the small range of fluctuations in speed variation under normal operating conditions, while the grid power rate of change threshold represents the maximum acceptable range of grid load fluctuations.

[0072] The system continuously monitors real-time data on the ship's main engine speed and the power demand of the power grid, and calculates the rate of change of these two parameters. The rate of change of engine speed represents the difference in engine speed between the current moment and the previous moment, while the rate of change of power demand represents the fluctuation range of power demand in the power grid. By calculating these two rates of change, the system can track the ship's current operating status in real time and determine whether it has entered a steady state or whether a disturbance has occurred.

[0073] The calculated rate of change of engine speed and the rate of change of power demand from the power grid are compared with preset thresholds. When both rates of change remain below their respective thresholds, it indicates that the ship is in a stable navigation state, and the system will determine that the current navigation condition is stable and decide to switch to the efficient cruise mode. If either rate of change exceeds its corresponding threshold, it indicates that the ship's main engine speed or power grid load demand has fluctuated significantly, and the ship may be in a state of disturbance due to speed or load changes. At this time, the system will switch to the maneuvering operation mode.

[0074] The adaptive decision-making method based on the rate of change threshold not only ensures the efficient operation of the ship's electrical system under different operating conditions, but also greatly improves the system's stability and adaptability, optimizes the power management strategy, and ensures the efficient and safe use of energy.

[0075] In one possible implementation, the system continuously monitors the ship's main engine speed and the output power of the shaft-driven generator system. These two parameters effectively reflect the ship's operating status, particularly whether the main engine is shut down and whether the generator system is functioning properly. When the ship is anchored in port, the main engine speed is typically zero, and the output power of the shaft-driven generator system may also be zero. In this case, the system determines whether the ship is stationary by monitoring these two key indicators in real time.

[0076] When the main engine speed is detected to be zero and the output power of the shaft-driven generator system remains zero for a duration exceeding a preset time, the system automatically determines that the ship is fully docked and ceases all power generation. At this point, the system switches to port quiet mode. The core purpose of port quiet mode is to reduce noise and pollution to the surrounding environment when the ship is docked in port, especially to reduce the operating load on the ship's engines and generators.

[0077] In port silent mode, the ship's electrical system operates differently from other navigation modes. The system no longer needs additional power from the main engine or shaft generator. Instead, it uses a lithium-ion battery system to meet the load demands of the ship's electrical grid. To ensure stable power supply to the grid, the system sets the target charging / discharging power to be equal to the grid's load requirements, with the power direction being discharge. That is, the lithium-ion battery is discharging, providing the necessary power to the grid.

[0078] The port silent mode not only provides ships with an environmentally friendly and intelligent berthing power management solution, but also improves the system's energy efficiency and reduces environmental pollution, thus achieving significant economic and environmental benefits.

[0079] In one possible implementation, during the system design phase, it is first necessary to establish an energy flow simulation model of the ship's hybrid electric system. This model is used to simulate the power flow of the ship 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 ship's operating conditions in order to accurately predict the power demand and supply of each component.

[0080] The simulation model requires defining a series of different real-time power difference conditions and lithium battery system state-of-charge (SOC) conditions. Real-time power difference refers to the difference between the ship's actual power demand and the power that the power generation system can provide, while SOC refers to the current charge level of the lithium battery. These conditions will directly impact the operation of the ship's electrical system under different operating conditions.

[0081] To ensure efficient system operation, a multi-objective optimization method is employed when setting optimization objectives. Under each pair of power differentials and state of charge conditions, the objective is to maximize the overall efficiency of the ship's electrical system while simultaneously minimizing the cycle life degradation of the lithium battery system. Overall efficiency considers factors such as energy conversion efficiency and load balancing of the power generation system, while cycle life degradation is related to the depth and frequency of lithium battery charge and discharge. By weighing these two objectives, the multi-objective optimization algorithm can calculate the optimal lithium battery power reference value.

[0082] After obtaining the optimal power reference value for each combination of conditions, these results are stored in a multidimensional database. The database records all possible power differences and state-of-charge combinations, and provides the corresponding optimal power reference value for each combination. This database is a predefined strategy that can be quickly queried based on real-time conditions during actual operation to generate the target charge / discharge power.

[0083] Through precise simulation modeling, multi-objective optimization, and real-time query mechanisms, the operating efficiency of ship power systems has been improved, and the service life of lithium batteries has been effectively extended, demonstrating strong practical application value and technological advantages.

[0084] In one possible implementation, to achieve stable power control, a sliding time window is first needed to backtrack historical data over a certain period. Within this window, the system can acquire power output data from the shaft-driven generator system over a specific time range. The window size depends on the ship's operating characteristics and the system's response speed, and typically needs to be optimized based on actual conditions.

[0085] After setting the time window, the system will collect historical power output data sequences of the shaft-driven power generation system within the window. This data reflects the power fluctuations of the power generation system within a certain time range. By collecting this data, the system can analyze the actual output power of the power generation system and then formulate appropriate stable power control strategies.

[0086] To eliminate short-term power fluctuations and prevent sudden system interference, historical data sequences undergo digital filtering. The purpose of filtering is to remove short-term fluctuations caused by instantaneous changes, equipment interference, or external environmental changes, resulting in smoother and more stable data. Common digital filtering methods include low-pass filtering and weighted averaging.

[0087] The filtered data will be used to calculate the stable power value that the shaft-driven power generation system should maintain. Two methods can be used: one is to calculate the arithmetic mean of the data sequence, that is, to sum all the data values ​​and take the average; the other method is to use a time-weighted average, that is, to calculate the average value based on the weights of different time points. The weighted average can better account for the impact of power changes over different time periods, and it has a better smoothing effect, especially for fluctuations over longer periods.

[0088] Ultimately, the stable power value calculated through the above steps will serve as a control signal, instructing the shaft-driven power generation system to maintain this power output to ensure the smooth operation of the system and a stable power supply.

[0089] By combining historical data, digital filtering, and weighted averaging techniques, the system not only ensures power stability during operation but also effectively improves energy efficiency, equipment lifespan, and overall system stability, demonstrating excellent practicality and economy.

[0090] In one possible implementation, within the ship's hybrid electric management system, a commanded charge / discharge power is first generated based on the ship's current operating status and load requirements. This power value reflects the power that the lithium battery system needs to output under the current conditions to maintain the ship's operation.

[0091] The system needs to check whether the generated charge / discharge power commands exceed the physical limitations of the lithium battery, especially the discharge power. If the command is a discharge power command and its absolute value exceeds the maximum discharge power that the lithium battery system can currently provide, then measures need to be taken to prevent the lithium battery from being damaged by over-discharge.

[0092] When the system detects that the lithium battery cannot provide the required discharge power, it generates a start signal for the diesel generator set. This signal triggers the start-stop control system of the diesel generator set, starting the generator set to supplement the power shortage in the power system.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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 variation trend of the ship's main engine and the load demand power variation trend 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 power surplus and a maneuvering operation mode with power fluctuation. 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 determined system operating mode and the state of charge of the lithium battery system, a target charge / discharge power is generated for the lithium battery system. Specifically, in the high-efficiency cruise mode, with the goal of achieving optimal overall system energy efficiency, the target charge / discharge power is generated by querying a predefined strategy based on the real-time power difference and the state of charge. In the maneuvering operation mode, with the primary objective of maintaining stable shipboard power grid frequency, the shaft-driven power generation system is controlled to output a stable power, and the entire real-time power difference is allocated to the lithium battery system as the target charge / discharge 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; 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.

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 system operation modes also include the port silent mode; The step of adaptively determining the current system operating mode further includes: 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.

3. 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.

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 aforementioned 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.

5. 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.

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 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.

7. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy as described in claim 6, 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 maximum allowable charge and discharge power at the operating point corresponding to the temperature and state of charge combination is determined by judging whether the voltage change exceeds the safety window. 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.

8. A ship hybrid power management method based on shaft-driven power generation and lithium battery synergy according to claim 1, characterized in that, After collecting data on the load 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, the data also includes a step of preprocessing the collected 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.

9. 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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