Energy storage system power distribution method considering state coupling characteristics in dynamic positioning

Abstract

The invention relates to the field of all-electric ship power management, in particular to an energy storage system power distribution method considering state coupling characteristics in dynamic positioning, which comprises the following steps: S1, establishing a ship thrust power distribution model considering marine environment influence; s2, establishing a ship three-stage power distribution model considering energy storage state coupling characteristics; s3, constructing a ship power grid power balance model based on the ship thrust power demand output by the ship thrust power distribution model and the dynamic power feasible range output by the ship three-stage power distribution model; and S4, solving the ship power grid power balance model to obtain a dynamic power distribution strategy, and realizing power distribution of the ship hybrid energy storage system through the dynamic power distribution strategy. According to the method, the reasonability and comprehensiveness of power distribution of the ship hybrid energy storage system can be improved, violent power fluctuation of a ship power grid is relieved, and the reliability and stability of the ship DP system in a complex marine environment are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of all-electric ship power management, and particularly to a power allocation method for energy storage systems considering state coupling characteristics in dynamic positioning. BACKGROUND

[0002] All-electric ships (AESs), equipped with direct current electric power systems, exhibit superior maneuvering flexibility in a variable sailing environment, especially in low-speed dynamic positioning (DP) tasks. AESs use battery management systems (BMS) and energy management systems (EMS) to optimize energy distribution, ensuring that the required propulsion force can be maintained in the face of environmental uncertainties such as wind, waves, and ocean currents. However, these uncertainties can cause a sharp increase in ship propulsion, placing higher demands on the power system.

[0003] Due to the limitations of the speed regulation capability of the onboard main engine, uneven power distribution can cause a sharp drop in voltage, triggering an under-voltage protection, which in turn can cause a protective power outage, and even possibly leading to task failure. Under-voltage protection is a safety mechanism that cuts off power when the grid voltage is too low to protect electric motors and electrical systems from overload damage. Therefore, under uncertain sailing conditions such as DP operations, the requirements for control technology are more stringent to suppress severe power fluctuations. This requires the use of advanced control algorithms, such as model predictive control and Kalman state estimators, as well as energy storage unit battery energy storage systems to smooth out power fluctuations. Through these technologies, real-time monitoring of ship power system parameters can be achieved, and dynamic adjustments to power distribution can be made to maintain the stability and transient stability of the ship's power system.

[0004] Energy storage systems, as flexible allocators of power resources, play a crucial role in electrified DP systems. In particular, lithium-ion batteries, due to their widespread application, have a decisive influence on system performance due to their operating characteristics. First, land-based research results show that the internal states of lithium-ion batteries, such as state of charge (SoC), state of health (SoH), and state of power (SoP), are highly coupled and interact with each other on different time scales. Second, uncertain marine environmental factors, such as high temperature, rolling, vibration, humidity, and salt spray, greatly induce state coupling characteristics and continuously change the battery's safe operating power (SOP) range, leading to insufficient power supply.

[0005] Therefore, it is particularly important to quantify the dynamic influence of uncertain marine environment on the battery, which helps to achieve adaptive allocation of dynamic power for the onboard micro-grid. The battery energy storage system manages and maintains each battery unit intelligently through the battery management system, prevents overcharging and over-discharging of the battery, prolongs the service life of the battery, and monitors the state of the battery. The battery capacity refers to the charge Q that can be accommodated or released, that is, the battery capacity (Ah) = current (A) x discharge time.

[0006] During the operation of the battery, limiting the battery output power within a feasible operating range can avoid overcharging and over-discharging of the battery, and prolong the service life of the battery. However, limiting the battery output may cause power imbalance of the ship power grid, and additional power compensation means is needed to achieve source-load balance of the ship power grid. Therefore, in order to adapt to extreme conditions in the marine environment, advanced control strategies need to be developed. These control strategies can take into account the nonlinear characteristics and uncertainties of the battery, as well as disturbances from the external environment, so as to optimize the use efficiency and life of the battery, and ensure the reliability and stability of the DP system in the face of complex marine environments. SUMMARY

[0007] In view of the above problems of the prior art, the technical problem to be solved by the present application is to provide a power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning, which uses a hybrid energy storage system to provide flexible power support for the onboard power system, integrates the battery state coupling characteristics into the battery model to accurately depict the power supply capability of the energy storage system, and obtains a dynamic power allocation strategy by solving a power grid power balance model, thereby improving the rationality and comprehensiveness of the power allocation of the ship hybrid energy storage system, relieving the severe power fluctuations of the ship power grid, and ensuring the reliability and stability of the ship DP system in the face of complex marine environments.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0009] The power allocation method for the energy storage system considering state coupling characteristics in dynamic positioning comprises:

[0010] S1: establishing a ship thrust power allocation model considering the influence of marine environment; calculating the ship propulsion power demand through the ship thrust power allocation model;

[0011] S2: establishing a ship three-stage power allocation model considering the state coupling characteristics of the energy storage; solving the ship three-stage power allocation model to obtain the dynamic power feasible range of the ship hybrid energy storage system;

[0012] S3: based on the ship propulsion power demand output by the ship thrust power allocation model and the dynamic power feasible range output by the ship three-stage power allocation model, constructing a ship power grid power balance model;

[0013] S4: solving the ship power grid power balance model to obtain a dynamic power distribution strategy, and realizing power distribution of the ship hybrid energy storage system through the dynamic power distribution strategy.

[0014] Preferably, in step S1, the ship thrust power distribution model considering the influence of marine environment is established by the following steps:

[0015] S101: analyzing the mathematical relationship between the ship speed and the ground position and the mathematical relationship between the ship thrust and the speed under uncertain marine environment interference;

[0016] S102: constructing a ship state variable deviation model based on the mathematical relationship between the ship speed and the ground position and the mathematical relationship between the ship thrust and the speed;

[0017] S103: constructing a ship thrust power distribution model based on the ship state variable deviation model.

[0018] Preferably, in step S101, the mathematical relationship between the ship speed and the ground position is as follows:

[0019]

[0020] In the formula: η = [x η ,y η ,Ψ] T ∈R 3×1 represents the surge position x, sway y and yaw angle Ψ; U = [u U ,v U ,r] T ∈R 3 ×1 represents the surge, sway and yaw speed; R(Ψ) ∈ R 3×3 represents the position transfer matrix;

[0021] The mathematical relationship between the ship thrust and the speed is represented as:

[0022]

[0023] In the formula: M ∈ R 3×3 represents the mass matrix of the rigid body; M A ∈R 3×3 represents the added mass matrix; D ∈ R 3×3 represents the hydrodynamic damping matrix; E U ∈R 3×3 represents the noise amplitude of the speed; ω U = [ω u ,ω v ,ω w ] T ∈R 3×1 represents the noise matrix of the speed; b ∈ R3×1 This represents a set of uncertain marine environmental disturbances;

[0024] The formula for the uncertain marine environmental disturbance set b is expressed as:

[0025]

[0026] In the formula: f w ,f c ,f wav T represents the equivalent external forces of wind, ocean current, and ocean waves, respectively; b =diag[T t ,T t ,T t ] T ∈R 3×3 Represents the time constant matrix; E b ∈R 3×3 Indicates the amplitude of the environmental disturbance; ω b ∈R 3×1 Represents the noise matrix; ρ a and V rc These represent air density and relative wind speed, respectively; A Fw A Lw L oa Represent the frontal and lateral projection regions on the xz and yz planes, respectively; ρ w C represents the density of water. cx C cy C cr These represent the current drag coefficients in the surge, sway, and yaw directions, respectively; C wx C wy C wr L represents the dimensionless wind coefficients in the directions of surge, sway, and yaw, respectively; pp D T These represent the ship's length and draft, respectively; C vx C vy C vr These represent the average drift coefficients of the ship in its three degrees of freedom; H s Indicates wave height; γ wav Indicates the wave angle;

[0027] In step S102, the formula for the ship state variable deviation model is expressed as follows:

[0028]

[0029] in:

[0030]

[0031] In the formula: U eη e These represent the deviations in the three degrees of freedom: acceleration, navigation velocity, and position, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; τ=[τ1,τ2,τ3] represents the ship's three degrees of freedom thrust; azimuth angle α=[α1,α2,...,α i The propeller force Kf and the propeller force Kf are the control variables of the dynamic positioning controller, where K = diag[K1, K2, ..., Kf]. i ] and f = [f1, f2, ..., f i ] T .

[0032] Preferably, in step S103, the ship thrust power distribution model is as follows:

[0033]

[0034] in:

[0035]

[0036] In the formula: P s Indicates the ship's propulsion power requirement; P f Indicates the ship's power requirement; k g ω g ω0 and ω0 represent the proportional factor, fluctuation frequency, and steady-state frequency of the ship's main engine, respectively; α and α0 represent the azimuth angles of the current control cycle and the previous control cycle, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; D r Indicates diameter; η m Indicates efficiency; P i It is a non-linear term; K T and K Q These represent the thrust coefficient and torque coefficient, respectively; J represents the ship's advance ratio.

[0037] Preferably, in step S2, a three-stage power allocation model for the ship considering the energy storage state coupling characteristics is established through the following steps:

[0038] S201: Based on the analysis of the state coupling characteristics of the energy storage system during ship navigation, a state coupling model for the ship navigation process is constructed.

[0039] The state-coupled model is represented as:

[0040]

[0041] In the formula: variable x represents [SOC] bat SOC uc ] T That is, the system's state variables, SOC bat and SOC uc These represent the state of charge of the battery and the supercapacitor, respectively; the control variable u = [I bat ,I uc ] T I bat and I uc These represent the currents of the battery and the supercapacitor, respectively; the output variable y = [P] bat ,P uc ] T P bat and P uc Represent the output power of the battery and supercapacitor, respectively; ΔT represents the control time range; diag represents the diagonal matrix; η bat and η uc These represent the power efficiency of the battery and the supercapacitor, respectively. R uc and C uc These represent the initial voltage, resistance, and capacitance of the supercapacitor, respectively; OCV, R0, and U represent the open-circuit voltage, ohmic resistance, and polarization voltage of the battery, respectively; C bat and These represent the battery's current capacity and initial capacity, respectively. These represent the minimum charging power and maximum discharging power of the battery, respectively; Θ represents the state coupling function.

[0042] S202: Based on the state-coupled model, the state of charge (SOC) of the battery is estimated through a dynamic output model. bat ;

[0043] S203: Based on the state-coupled model, the battery health state (SOH) is estimated through the capacity degradation model;

[0044] S204: Battery State of Charge (SOC) bat The estimated results of the state of health (SOH) are combined with the hybrid constraints to calculate the feasible range of dynamic power of the battery.

[0045] The formula is expressed as:

[0046]

[0047] In the formula: SOP represents the feasible dynamic power range of the battery; and These represent the minimum charging power and maximum discharging power of the battery, respectively; U bat Indicates the battery voltage; N batIndicates the number of batteries; and I min These represent the state of charge, voltage, and minimum current range of current constraints during charging, respectively. and I max These represent the state of charge, voltage, and maximum current range of the current constraint during discharge, respectively.

[0048] Preferably, in step S202, the formula for the dynamic output model is expressed as follows:

[0049]

[0050] In the formula: U bat Indicates the battery voltage; C p R p and I p These represent polarization capacity, polarization resistance, and polarization current, respectively; OCV represents the battery open-circuit voltage; R0 represents the battery's ohmic resistance; I bat ΔT represents the battery current; ΔT represents the control time range.

[0051] Preferably, in step S203, the formula for the capacity degradation model is expressed as follows:

[0052]

[0053] In the formula: This represents the estimated initial capacity for period n; OCV represents the battery polarization voltage during period n. n χ represents the open-circuit voltage of the battery during period n. n The derivative of the OCV with period n; This represents the output efficiency for period n; Represents the battery current during period n; Represents the polarization capacity of period n; The polarization resistance represents the period n; w represents the process noise; and ΔT represents the control time range.

[0054] Preferably, in step S3, the ship's power grid power balance model is constructed through the following steps:

[0055] S301: The dynamic model of the ship's DC voltage is established as follows:

[0056]

[0057] In the formula: U dc Indicates bus voltage; C dc Indicates the capacitance of the DC-supported capacitor; P Gen P represents the power of a diesel engine. s Indicates the ship's propulsion power requirement; P pulIndicates ship pulse load; P hess P represents the output power of a ship's hybrid energy storage system. ser Indicates the shipboard service load; and These represent the minimum charging power and maximum discharging power of the battery, respectively.

[0058] S302: Input the ship's propulsion power requirements and dynamic power feasible range into the DC voltage dynamic model to calculate the output power of the ship's hybrid energy storage system;

[0059] S303: Calculate the battery power deviation between the battery output power and the actual power demand based on the battery state coupling model;

[0060] S304: Use a feedforward power control method to decompose power fluctuations at different time scales;

[0061] S305: Based on power fluctuations at different time scales and the output power and battery power deviation of the ship's hybrid energy storage system, a ship power grid power balance model is established by combining the state of supercapacitors and batteries.

[0062] Preferably, in step S303, the formula for the battery state coupling model is expressed as follows:

[0063]

[0064] In the formula: Δe bat Indicates battery power deviation; This indicates the battery's power requirement; P bat Indicates battery output; Indicates the minimum charging power of the battery; and These represent the minimum and maximum discharge power of the battery, respectively; N bat Indicates the number of batteries.

[0065] Preferably, in step S305, the formula for the ship's power grid power balance model is expressed as follows:

[0066] P hess (k)=P uc (k)+P bat (k)+i ILC (k)U uc (k);

[0067] In the formula: P hess P represents the output power of a ship's hybrid energy storage system. uc P bat Let P represent the output power of the supercapacitor and the battery, respectively. Solve the power balance model of the ship's power grid and obtain P. uc and P batAs a dynamic power allocation strategy; U uc Indicates the terminal voltage of the supercapacitor; i ILC Indicates the compensation current;

[0068] Wherein, the compensation current i ILC The calculation formula is as follows:

[0069]

[0070] Δe hess =Δe bat +Δe uc ;

[0071]

[0072] Where: G ILC =K ILC [1 / (1+T c s)] and CR*G I T represents the transfer functions of the ILC controller and the current closed-loop controller, respectively; c K represents the time constant. ILC Indicates the gain of the controller; Δe bat Indicates battery power deviation; Δe uc Indicates the power error of the supercapacitor; Δe hess This indicates the total power error of the ship's hybrid energy storage system; P uc These represent the power requirement and output power of the supercapacitor, respectively.

[0073] The power allocation method for energy storage systems that considers state coupling characteristics in dynamic positioning in this invention has the following advantages compared with existing technologies:

[0074] This invention establishes a ship thrust power allocation model that considers the impact of the marine environment, accurately calculating the ship's propulsion power requirements and ensuring that the power allocation is highly matched with actual navigation conditions, avoiding power waste or insufficiency. Simultaneously, a three-stage power allocation model considering the coupling characteristics of energy storage states is constructed to dynamically analyze the charging and discharging capabilities of the energy storage system, clarify the dynamic power feasible range of the hybrid energy storage system, effectively coordinate the power allocation among different energy storage units, and improve the overall efficiency of the ship system. Furthermore, based on the propulsion power requirements and the dynamic power feasible range, a ship power grid balance model is constructed. The resulting dynamic power allocation strategy comprehensively considers the ship's navigation state, energy storage system state, and grid balance requirements, thereby improving the rationality and comprehensiveness of the power allocation of the ship's hybrid energy storage system, mitigating severe power fluctuations in the ship's power grid, and ensuring the reliability and stability of the ship's power distribution system in complex marine environments.

[0075] Existing propulsion models rely on real-time pulse power for accurate positioning, which is crucial for dynamic positioning systems. However, this dependence also leads to increased pulse loads in actual operation, potentially putting stress on the ship's propulsion system. To address this issue, this invention proposes a flexible ship thrust power distribution model. This model fully considers the characteristics of ship dynamics, aiming to quantify the ship's control flexibility and optimize power output to reduce the impact of pulse loads. Simultaneously, the model can predict the ship's motion trends in the near future and adjust the thruster output accordingly to achieve a smoother power supply. This not only reduces reliance on real-time pulse power but also improves the response speed and stability of the ship's propulsion system, thereby maintaining positioning accuracy while reducing pulse loads caused by fluctuations in power demand. Furthermore, the model can adapt to different marine environments and operating conditions by dynamically adjusting propulsion through real-time monitoring and analysis of ship motion parameters such as speed, acceleration, and attitude angles, as well as environmental factors such as wind speed and ocean currents. This flexible propulsion power model, which comprehensively considers ship dynamics and environmental factors, can significantly improve the ship's maneuverability and propulsion system reliability, providing a more stable and economical solution for ship dynamic positioning.

[0076] This invention constructs a three-stage power allocation model for ships, considering the coupling characteristics of energy storage states, through a six-month battery cycling experiment. This model aims to accurately capture the dynamic power feasible range of the battery. The three-stage power allocation model focuses on the interaction between the battery's state of charge, state of health, and state of power, which are crucial to battery operation and performance. Furthermore, this three-stage power allocation model is based not only on theoretical analysis but also on test data from actual lithium-ion batteries. Therefore, this model has high practical value and can be widely applied to various types of lithium-ion batteries, including electric vehicles, grid energy storage, and marine operational equipment. This experimental approach allows for more accurate prediction of battery behavior under different application scenarios, providing a scientific basis for the design and optimization of battery management systems. Such research not only enhances the understanding of battery state coupling characteristics but also provides a powerful tool for the practical operation and management of batteries.

[0077] This invention constructs a ship power grid power balance model based on the ship propulsion power demand output by the ship thrust power allocation model and the dynamic power feasible range output by the ship three-stage power allocation model. It then solves the ship power grid power balance model to obtain a dynamic power allocation strategy. This strategy aims to integrate the supply of numerous power resources, reduce the risk of power imbalance, and prevent DC voltage drop—a problem often overlooked in the field of dynamic positioning due to insufficient research. The dynamic power allocation strategy has been validated in two different practical scenarios: firstly, simulation tests using a hardware-in-the-loop simulation system to verify its theoretical applicability; secondly, a small experimental setup equipped with various loads was constructed to further confirm the effectiveness and reliability of the control strategy through actual operation. Attached Figure Description

[0078] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0079] Figure 1 This is a logic block diagram of a power allocation method for an energy storage system that considers state coupling characteristics during dynamic positioning.

[0080] Figure 2 This is a structural block diagram of the object ship.

[0081] Figure 3 A block diagram of a three-stage power allocation model for ships. Detailed Implementation

[0082] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but only to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0083] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not mean that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0084] The following detailed explanation illustrates the specific implementation methods:

[0085] Example:

[0086] This embodiment discloses a power allocation method for an energy storage system that considers state coupling characteristics in dynamic positioning.

[0087] like Figure 1 As shown, the power allocation method for energy storage systems considering state coupling characteristics in dynamic positioning includes:

[0088] S1: Establish a ship thrust power allocation model that takes into account the impact of the marine environment; calculate the ship propulsion power demand using the ship thrust power allocation model;

[0089] S2: Establish a three-stage power allocation model for ships that considers the coupling characteristics of energy storage states; solve the three-stage power allocation model for ships to obtain the dynamic power feasible range of the ship hybrid energy storage system;

[0090] S3: Based on the ship propulsion power demand output by the ship thrust power allocation model and the dynamic power feasible range output by the ship three-stage power allocation model, construct a ship power grid balance model;

[0091] S4: Solve the ship's power grid power balance model to obtain a dynamic power allocation strategy, which is then used to achieve power allocation for the ship's hybrid energy storage system. This dynamic power allocation strategy includes the output power of the supercapacitors and batteries in the ship's hybrid energy storage system.

[0092] This invention establishes a ship thrust power allocation model that considers the impact of the marine environment, accurately calculating the ship's propulsion power requirements and ensuring that the power allocation is highly matched with actual navigation conditions, avoiding power waste or insufficiency. Simultaneously, a three-stage power allocation model considering the coupling characteristics of energy storage states is constructed to dynamically analyze the charging and discharging capabilities of the energy storage system, clarify the dynamic power feasible range of the hybrid energy storage system, effectively coordinate the power allocation among different energy storage units, and improve the overall efficiency of the ship system. Furthermore, based on the propulsion power requirements and the dynamic power feasible range, a ship power grid balance model is constructed. The resulting dynamic power allocation strategy comprehensively considers the ship's navigation state, energy storage system state, and grid balance requirements, thereby improving the rationality and comprehensiveness of the power allocation of the ship's hybrid energy storage system, mitigating severe power fluctuations in the ship's power grid, and ensuring that the electrified DP system can operate according to the preset ship position or navigation trajectory.

[0093] To better illustrate the technical solution of the present invention, this embodiment is described in the following parts.

[0094] This embodiment uses an 82.8-meter supply ship (Northern Clipper) as an example. Figure 2 As shown, this is used to verify the effectiveness of the proposed method. The ship's specific composition is as follows: five propellers, including one tunnel propeller below the bow and four azimuth propellers. A typical Level 5 marine scenario is used to simulate uncertain marine environmental disturbances. The test system of this invention includes a ship battery test system and a hardware-in-the-loop controller system.

[0095] I. Ship Thrust Power Distribution Model

[0096] In this embodiment, a ship thrust power distribution model based on ship dynamics is established through the following steps:

[0097] S101: Analyze the mathematical relationships between ship speed and ground position, and between ship thrust and speed, under uncertain marine environmental disturbances;

[0098] S102: Based on the mathematical relationship between ship speed and ground position and between ship thrust and speed, construct a ship state variable deviation model;

[0099] S103: Based on the ship state variable deviation model, construct a ship thrust power distribution model.

[0100] 1) The mathematical relationship between ship speed and ground position is expressed as:

[0101]

[0102] In the formula: η=[x η ,y η ,Ψ] T ∈R 3×1 Indicates the surge position x, yaw y, and yaw angle Ψ; U = [u U ,v U ,r] T ∈R 3 ×1 Represents surge, sway, and yaw speeds; R(Ψ)∈R 3×3 Represents the position transition matrix;

[0103] 2) The mathematical relationship between ship thrust and speed is expressed as:

[0104]

[0105] Where: M∈R 3×3 The mass matrix of a rigid body; M A ∈R 3×3 Table of additional quality matrix; D∈R 3×3 E represents the hydrodynamic damping matrix; U ∈R 3×3 The noise amplitude representing the speed; ω U =[ω u ,ω v ,ω w ] T ∈R 3×1 The noise matrix representing velocity; b∈R 3×1 This represents a set of uncertain marine environmental disturbances;

[0106] The formula for the uncertain marine environmental disturbance set b is expressed as:

[0107]

[0108] In the formula: f w ,f c ,f wav T represents the equivalent external forces of wind, ocean current, and ocean waves, respectively; b =diag[T t ,T t ,T t ] T ∈R 3×3 Represents the time constant matrix; Eb ∈R 3×3 Indicates the amplitude of the environmental disturbance; ω b ∈R 3×1 Represents the noise matrix; ρ a and V rc These represent air density and relative wind speed, respectively; A Fw A Lw L oa Represent the frontal and lateral projection regions on the xz and yz planes, respectively; ρ w C represents the density of water. cx C cy C cr These represent the current drag coefficients in the surge, sway, and yaw directions, respectively; C wx C wy C wr L represents the dimensionless wind coefficients in the directions of surge, sway, and yaw, respectively; pp D T These represent the ship's length and draft, respectively; C vx C vy C vr These represent the average drift coefficients of the ship in its three degrees of freedom; H s Indicates wave height; γ wav Indicates the wave angle.

[0109] 3) The formula for the ship state variable deviation model is expressed as follows:

[0110]

[0111] in:

[0112]

[0113] In the formula: U e η e These represent the deviations in the three degrees of freedom: acceleration, navigation velocity, and position, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; τ=[τ1,τ2,τ3] represents the ship's three degrees of freedom thrust; azimuth angle α=[α1,α2,...,α i The propeller force Kf and the propeller force Kf are the control variables of the dynamic positioning controller, where K = diag[K1, K2, ..., Kf]. i ] and f = [f1, f2, ..., f i ] T The azimuth angle of the tunnel propeller is always 90°;

[0114] After high-pass filtering, the estimated deviation between navigation speed and position is:

[0115]

[0116] In the formula: T represents the time constant, and represents the bandwidth for controlling the ship's motion.

[0117] 4) The ship's thrust power distribution model is as follows:

[0118]

[0119] in:

[0120]

[0121] K T = -0.106J 2 -0.3246J +0.4594;

[0122] K Q = -0.0186J 2 -0.0399J +0.0680;

[0123] In the formula: P s Indicates the ship's propulsion power requirement; P f Indicates the ship's power requirement; k g ω g ω0 and ω0 represent the proportional factor, fluctuation frequency, and steady-state frequency of the ship's main engine, respectively; α and α0 represent the azimuth angles of the current control cycle and the previous control cycle, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; D r Indicates diameter; η m Indicates efficiency; P i It is a non-linear term; K T and K Q These represent the thrust coefficient and torque coefficient (obtained from the sea trial data set), respectively; J represents the ship's advance ratio.

[0124] Existing propulsion models rely on real-time pulse power for accurate positioning, which is crucial for dynamic positioning systems. However, this dependence also leads to increased pulse loads in actual operation, potentially putting stress on the ship's propulsion system. To address this issue, this invention proposes a flexible ship thrust power distribution model. This model fully considers the characteristics of ship dynamics, aiming to quantify the ship's control flexibility and optimize power output to reduce the impact of pulse loads. Simultaneously, the model can predict the ship's motion trends in the near future and adjust the thruster output accordingly to achieve a smoother power supply. This not only reduces reliance on real-time pulse power but also improves the response speed and stability of the ship's propulsion system, thereby maintaining positioning accuracy while reducing pulse loads caused by fluctuations in power demand. Furthermore, the model can adapt to different marine environments and operating conditions by dynamically adjusting propulsion through real-time monitoring and analysis of ship motion parameters such as speed, acceleration, and attitude angles, as well as environmental factors such as wind speed and ocean currents. This flexible propulsion power model, which comprehensively considers ship dynamics and environmental factors, can significantly improve the ship's maneuverability and propulsion system reliability, providing a more stable and economical solution for ship dynamic positioning.

[0125] II. Three-Stage Power Allocation Model for Ships

[0126] like Figure 3 As shown, a three-stage power allocation model for ships considering energy storage state coupling characteristics is established through the following steps:

[0127] S201: Based on the analysis of the state coupling characteristics of the energy storage system during ship navigation, a state coupling model for the ship navigation process is constructed.

[0128] Specifically, based on the measured lithium-ion battery dataset, the relationship between battery states SOC, SOH, and SOP is fitted, and then based on the functional relationship between different battery states, a state coupling model considering the impact of navigation uncertainties is established.

[0129] The relationship between the battery states of charge (SOC), state of equilibrium (SOH), and state of operation (SOP) is as follows:

[0130] 1) The battery power operating range (SOP) will change with the change of SOC;

[0131] 2) As the number of cycles increases or the SOH decreases, the SOP will decrease significantly.

[0132] The state-coupled model is represented as:

[0133]

[0134] In the formula: variable x represents [SOC]bat SOC uc ] T That is, the system's state variables, SOC bat and SOC uc These represent the state of charge of the battery and the supercapacitor, respectively; the control variable u = [I bat ,I uc ] T I bat and I uc These represent the current in the battery and the supercapacitor, respectively. A positive current indicates the discharge process, and a negative current indicates the charging process; the output variable y = [P] bat ,P uc ] T P bat and P uc Represent the output power of the battery and supercapacitor, respectively; ΔT represents the control time range; diag represents the diagonal matrix; η bat and η uc These represent the power efficiency of the battery and the supercapacitor, respectively. R uc and C uc These represent the initial voltage, resistance, and capacitance of the supercapacitor, respectively; OCV, R0, and U represent the open-circuit voltage, ohmic resistance, and polarization voltage of the battery, respectively; C bat and These represent the battery's current capacity and initial capacity, respectively. Θ represents the minimum charging power and maximum discharging power of the battery, respectively; Θ represents the state coupling function, which is calculated by the following state estimation method;

[0135] S202: Based on the state-coupled model, the battery's state of charge (SOC) is estimated using a dynamic output model (based on the minimum error optimization method). bat ;

[0136] S203: Based on the state-coupled model, the battery's state of health (SOH) is estimated using a capacity degradation model (considering dynamic voltage decay).

[0137] S204: Battery State of Charge (SOC) bat The estimated results of the state of health (SOH) are combined with the hybrid constraints to calculate the feasible range of dynamic power of the battery.

[0138] The formula is expressed as:

[0139]

[0140] In the formula: SOP represents the feasible dynamic power range of the battery. and These represent the minimum charging power and maximum discharging power of the battery, respectively. and I min These represent the state of charge, voltage, and minimum current range of current constraints during charging, respectively. and I max These represent the state of charge, voltage, and maximum current range under current constraints during discharge, respectively; U bat Indicates the battery voltage; N bat Indicates the number of batteries.

[0141] 1) The formula for the dynamic output model is expressed as:

[0142]

[0143] In the formula: U bat Indicates the battery voltage; C p R p and I p These represent polarization capacity, polarization resistance, and polarization current, respectively; OCV represents the battery open-circuit voltage; R0 represents the battery's ohmic resistance; I bat Indicates battery current; ΔT represents the control time range;

[0144] Specifically, the processing steps for solving the dynamic output model include:

[0145] The SOC estimation process of the dynamic output model is modeled as the following minimum output error optimization problem:

[0146]

[0147] In the formula: Estimate state variables; G v and G i These represent the output voltage error and the output current error, respectively; Q1, Q2, and R are the weights. The cost function is defined as follows: N is the runtime within each cycle.

[0148] Solving the minimum output error optimization problem yields the following results: And extract the battery's state of charge (SOC) from it. bat .

[0149] 2) The formula for the capacity degradation model is expressed as:

[0150]

[0151] In the formula: This represents the estimated initial capacity for period n; OCV represents the battery polarization voltage during period n. n χ represents the open-circuit voltage of the battery during period n. nThe derivative of the OCV with period n; This represents the output efficiency for period n; Represents the battery current during period n; Represents the polarization capacity of period n; The polarization resistance represents the period n; w represents the process noise; and ΔT represents the control time range.

[0152] Specifically, the steps for solving the capacity degradation model include:

[0153] Convert the capacity degradation model into Equation 1;

[0154] Formula 1 is expressed as:

[0155]

[0156] In the formula: This represents the standard current in the j-th 1C with period n;

[0157] Solving Formula 1 above, we can obtain the battery's current capacity C. bat And through the formula in the state coupling model Calculate the battery's state of health (SOH).

[0158] 3) Based on the above model, the formula for calculating capacity degradation error is as follows:

[0159]

[0160] In the formula: K represents the actual capacity; K is the gain matrix; e U This is the voltage error.

[0161] This invention constructs a three-stage power allocation model for ships, considering the coupling characteristics of energy storage states, through a six-month battery cycling experiment. This model aims to accurately capture the dynamic power feasible range of the battery. The three-stage power allocation model focuses on the interaction between the battery's state of charge, state of health, and state of power, which are crucial to battery operation and performance. Furthermore, this three-stage power allocation model is based not only on theoretical analysis but also on test data from actual lithium-ion batteries. Therefore, this model has high practical value and can be widely applied to various types of lithium-ion batteries, including electric vehicles, grid energy storage, and marine operational equipment. This experimental approach allows for more accurate prediction of battery behavior under different application scenarios, providing a scientific basis for the design and optimization of battery management systems. Such research not only enhances the understanding of battery state coupling characteristics but also provides a powerful tool for the practical operation and management of batteries.

[0162] III. Power Balance Model of Shipboard Power Grid

[0163] In this embodiment, the power balance model of the ship's power grid is constructed through the following steps:

[0164] S301: Establish a dynamic model of the ship's DC voltage;

[0165] S302: Input the ship's propulsion power requirements and dynamic power feasible range into the DC voltage dynamic model to calculate the output power of the ship's hybrid energy storage system;

[0166] S303: Calculate the battery power deviation between the battery output power and the actual power demand based on the battery state coupling model;

[0167] S304: The feedforward power control method is used to decompose power fluctuations at different time scales; calculating power fluctuations provides basic data for building a power balance model of the ship's power grid, assists in achieving power balance and stability of the power grid, and supports the formulation of dynamic power allocation strategies.

[0168] S305: Based on power fluctuations at different time scales and the output power and battery power deviation of the ship's hybrid energy storage system, a ship power grid power balance model is established by combining the state of supercapacitors and batteries (using the MPC-ILC method).

[0169] 1) The formula for the DC voltage dynamic model is expressed as follows:

[0170]

[0171] In the formula: U dc Indicates bus voltage; C dc Indicates the capacitance of the DC-supported capacitor; P Gen P represents the power of a diesel engine. s Indicates the ship's propulsion power requirement; P pul Indicates ship pulse load; P hess P represents the output power of a ship's hybrid energy storage system. ser Indicates the shipboard service load; and These represent the minimum charging power and maximum discharging power of the battery, respectively.

[0172] 2) The formula for the battery state coupling model is expressed as:

[0173]

[0174] In the formula: Δe bat Indicates battery power deviation; This indicates the battery's power requirement; P bat Indicates battery output; Indicates the minimum charging power of the battery; and These represent the minimum and maximum discharge power of the battery, respectively; N bat Indicates the number of batteries.

[0175] 3) Establish a shipboard power grid power balance model through the following steps:

[0176] P hess (k)=P uc (k)+P bat (k)+i ILC (k)U uc (k);

[0177] In the formula: P hess P represents the output power of a ship's hybrid energy storage system. uc P bat Let P represent the output power of the supercapacitor and the battery, respectively. Solve the power balance model of the ship's power grid and obtain P. uc and P bat As a dynamic power allocation strategy; U uc Indicates the terminal voltage of the supercapacitor; i ILC Indicates the compensation current;

[0178] 4) Compensation current i ILC The calculation formula is as follows:

[0179]

[0180] Δe hess =Δe bat +Δe uc ;

[0181]

[0182] Where: G ILC =K ILC [1 / (1+T c s)] and CR*G I T represents the transfer functions of the ILC controller and the current closed-loop controller, respectively; c K represents the time constant. ILC Indicates the gain of the controller; Δe bat Indicates battery power deviation; Δe uc Indicates the power error of the supercapacitor; Δe hess This indicates the total power error of the ship's hybrid energy storage system; P uc These represent the power requirement and output power of the supercapacitor, respectively.

[0183] This invention constructs a ship power grid power balance model based on the ship's propulsion power demand output from the ship's thrust power allocation model and the dynamic power feasible range output from the ship's three-stage power allocation model. It then solves the ship power grid power balance model to obtain a dynamic power allocation strategy. This strategy aims to integrate the supply of numerous power resources, reduce the risk of power mismatch, and prevent DC voltage drop—a problem often overlooked in the field of dynamic positioning due to insufficient research. This dynamic power allocation strategy has been validated in two different practical scenarios: firstly, simulation testing using a hardware-in-the-loop simulation system to verify its theoretical applicability; secondly, a small experimental device equipped with various loads was constructed to further confirm the effectiveness and reliability of the control strategy through actual operation. Simultaneously, this invention considers the impact of complex marine environments on the coupling state of ship energy storage systems, designing a control strategy capable of instantaneously balancing ship power mismatch, thereby reducing the impact of pulsed loads on the ship's microgrid and improving the accuracy of ship dynamic positioning.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning, characterized in that, include: S1: Establish a ship thrust power allocation model that takes into account the impact of the marine environment; calculate the ship propulsion power demand using the ship thrust power allocation model; S2: Establish a three-stage power allocation model for ships that considers the coupling characteristics of energy storage states; solve the three-stage power allocation model for ships to obtain the dynamic power feasible range of the ship hybrid energy storage system; S3: Based on the ship propulsion power demand output by the ship thrust power allocation model and the dynamic power feasible range output by the ship three-stage power allocation model, construct a ship power grid balance model; S4: Solve the power balance model of the ship's power grid to obtain a dynamic power allocation strategy, and realize the power allocation of the ship's hybrid energy storage system through the dynamic power allocation strategy.

2. The power allocation method for energy storage systems considering state coupling characteristics in dynamic positioning as described in claim 1, characterized in that: In step S1, a ship thrust power distribution model considering the impact of the marine environment is established through the following steps: S101: Analyze the mathematical relationships between ship speed and ground position, and between ship thrust and speed, under uncertain marine environmental disturbances; S102: Based on the mathematical relationship between ship speed and ground position and between ship thrust and speed, construct a ship state variable deviation model; S103: Based on the ship state variable deviation model, construct a ship thrust power distribution model.

3. The power allocation method for energy storage systems considering state coupling characteristics in dynamic positioning as described in claim 2, characterized in that: In step S101, the mathematical relationship between the ship's speed and its position on the ground is as follows: In the formula: η=[x η ,y η ,Ψ] T ∈R 3×1 Indicates the surge position x, yaw y, and yaw angle Ψ; U = [u U ,v U ,r] T ∈R 3×1 Represents surge, sway, and yaw speeds; R(Ψ)∈R 3×3 Represents the position transition matrix; The mathematical relationship between ship thrust and speed is expressed as follows: Where: M∈R 3×3 The mass matrix of a rigid body; M A ∈R 3×3 Table of additional quality matrix; D∈R 3×3 E represents the hydrodynamic damping matrix; U ∈R 3×3 The noise amplitude representing the speed; ω U =[ω u ,ω v ,ω w ] T ∈R 3×1 The noise matrix representing velocity; b∈R 3 ×1 This represents a set of uncertain marine environmental disturbances; The formula for the uncertain marine environmental disturbance set b is expressed as: In the formula: f w ,f c ,f wav T represents the equivalent external forces of wind, ocean current, and ocean waves, respectively; b =diag[T t ,T t ,T t ] T ∈R 3×3 Represents the time constant matrix; E b ∈R 3×3 Indicates the amplitude of the environmental disturbance; ω b ∈R 3×1 Represents the noise matrix; ρ a and V rc These represent air density and relative wind speed, respectively; A Fw A Lw L oa Represent the frontal and lateral projection regions on the xz and yz planes, respectively; ρ w C represents the density of water. cx C cy C cr These represent the current drag coefficients in the surge, sway, and yaw directions, respectively; C wx C wy C wr L represents the dimensionless wind coefficients in the directions of surge, sway, and yaw, respectively; pp D T These represent the ship's length and draft, respectively; C vx C vy C vr These represent the average drift coefficients of the ship in its three degrees of freedom; H s Indicates wave height; γ wav Indicates the wave angle; In step S102, the formula for the ship state variable deviation model is expressed as follows: in: In the formula: U e η e These represent the deviations in the three degrees of freedom: acceleration, navigation velocity, and position, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; τ=[τ1,τ2,τ3] represents the ship's three degrees of freedom thrust; azimuth angle α=[α1,α2,...,α i The propeller force Kf and the propeller force Kf are the control variables of the dynamic positioning controller, where K = diag[K1, K2, ..., Kf]. i ] and f = [f1, f2, ..., f i ] T .

4. The power allocation method for energy storage systems considering state coupling characteristics in dynamic positioning as described in claim 3, characterized in that: In step S103, the ship thrust power distribution model is as follows: in: In the formula: P s Indicates the ship's propulsion power requirement; P f Indicates the ship's power requirement; k g ω g ω0 and ω0 represent the proportional factor, fluctuation frequency, and steady-state frequency of the ship's main engine, respectively; α and α0 represent the azimuth angles of the current control cycle and the previous control cycle, respectively; T s T e These represent the start and end times of the thrust control cycle, respectively; τ e Indicates the allowable thrust deviation; D r Indicates diameter; η m Indicates efficiency; P i It is a non-linear term; K T and K Q These represent the thrust coefficient and torque coefficient, respectively; J represents the ship's advance ratio.

5. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 1, characterized in that: In step S2, a three-stage power allocation model for ships considering the state coupling characteristics of energy storage is established through the following steps: S201: Based on the analysis of the state coupling characteristics of the energy storage system during ship navigation, a state coupling model for the ship navigation process is constructed. The state-coupled model is represented as: In the formula: variable x represents [SOC] bat SOC uc ] T That is, the system's state variables, SOC bat and SOC uc These represent the state of charge of the battery and the supercapacitor, respectively; the control variable u = [I bat ,I uc ] T I bat and I uc These represent the current in the battery and the supercapacitor, respectively. Output variable y = [P bat ,P uc ] T P bat and P uc Represent the output power of the battery and supercapacitor, respectively; ΔT represents the control time range; diag represents the diagonal matrix; η bat and η uc These represent the power efficiency of the battery and the supercapacitor, respectively. R uc and C uc These represent the initial voltage, resistance, and capacitance of the supercapacitor, respectively; OCV, R0, and U represent the open-circuit voltage, ohmic resistance, and polarization voltage of the battery, respectively; C bat and These represent the battery's current capacity and initial capacity, respectively. These represent the minimum charging power and maximum discharging power of the battery, respectively; Θ represents the state coupling function. S202: Based on the state-coupled model, the state of charge (SOC) of the battery is estimated through a dynamic output model. bat ; S203: Based on the state-coupled model, the battery health state (SOH) is estimated through the capacity degradation model; S204: Battery State of Charge (SOC) bat The estimated results of the state of health (SOH) are combined with the hybrid constraints to calculate the feasible range of dynamic power of the battery. The formula is expressed as: In the formula: SOP represents the feasible dynamic power range of the battery; and These represent the minimum charging power and maximum discharging power of the battery, respectively; U bat Indicates the battery voltage; N bat Indicates the number of batteries; and I min These represent the state of charge, voltage, and minimum current range of current constraints during charging, respectively. and I max These represent the state of charge, voltage, and maximum current range of the current constraint during discharge, respectively.

6. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 5, characterized in that: In step S202, the formula for the dynamic output model is expressed as follows: In the formula: U bat Indicates the battery voltage; C p R p and I p These represent polarization capacity, polarization resistance, and polarization current, respectively; OCV represents the battery open-circuit voltage; R0 represents the battery's ohmic resistance; I bat ΔT represents the battery current; ΔT represents the control time range.

7. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 6, characterized in that: In step S203, the formula for the capacity degradation model is expressed as follows: In the formula: This represents the estimated initial capacity for period n; OCV represents the battery polarization voltage during period n. n χ represents the open-circuit voltage of the battery during period n. n The derivative of the OCV with period n; This represents the output efficiency for period n; Represents the battery current during period n; Represents the polarization capacity of period n; The polarization resistance represents the period n; w represents the process noise; and ΔT represents the control time range.

8. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 1, characterized in that: In step S3, the power balance model of the ship's power grid is constructed through the following steps: S301: The dynamic model of the ship's DC voltage is established as follows: In the formula: U dc Indicates bus voltage; C dc Indicates the capacitance of the DC-supported capacitor; P Gen P represents the power of a diesel engine. s Indicates the ship's propulsion power requirement; P pul Indicates ship pulse load; P hess P represents the output power of a ship's hybrid energy storage system. ser Indicates the shipboard service load; and These represent the minimum charging power and maximum discharging power of the battery, respectively. S302: Input the ship's propulsion power requirements and dynamic power feasible range into the DC voltage dynamic model to calculate the output power of the ship's hybrid energy storage system; S303: Calculate the battery power deviation between the battery output power and the actual power demand based on the battery state coupling model; S304: Use a feedforward power control method to decompose power fluctuations at different time scales; S305: Based on power fluctuations at different time scales and the output power and battery power deviation of the ship's hybrid energy storage system, a ship power grid power balance model is established by combining the state of supercapacitors and batteries.

9. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 8, characterized in that: In step S303, the formula for the battery state coupling model is expressed as follows: In the formula: Δe bat Indicates battery power deviation; This indicates the battery's power requirement; P bat Indicates battery output; Indicates the minimum charging power of the battery; and These represent the minimum and maximum discharge power of the battery, respectively; N bat Indicates the number of batteries.

10. The power allocation method for an energy storage system considering state coupling characteristics in dynamic positioning as described in claim 8, characterized in that: In step S305, the formula for the ship's power grid balance model is expressed as follows: P hess (k)=P uc (k)+P bat (k)+i ILC (k)U uc (k); In the formula: P hess P represents the output power of a ship's hybrid energy storage system. uc P bat Let P represent the output power of the supercapacitor and the battery, respectively. Solve the power balance model of the ship's power grid and obtain P. uc and P bat As a dynamic power allocation strategy; U uc Indicates the terminal voltage of the supercapacitor; i ILC Indicates the compensation current; Wherein, the compensation current i ILC The calculation formula is as follows: Δe hess =Δe bat +Δe uc ; Where: G ILC =K ILC [1 / (1+T c s)] and CR*G I T represents the transfer functions of the ILC controller and the current closed-loop controller, respectively; c K represents the time constant. ILC Indicates the gain of the controller; Δe bat Indicates battery power deviation; Δe uc Indicates the power error of the supercapacitor; Δe hess This indicates the total power error of the ship's hybrid energy storage system; P uc These represent the power requirement and output power of the supercapacitor, respectively.

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