Multi-port input electric ship energy equalization charging system

Abstract

The invention discloses an electric ship energy equalizing charging system based on multi-port input. The system comprises a multi-port input system, a detachable high-capacity energy storage system, a battery management system and a load system, the multi-port input system comprises a wharf power supply module, a photovoltaic cell module, a first bidirectional direct current converter module and a first unidirectional direct current converter module; the detachable high-capacity energy storage system comprises a detachable energy storage bin, a second bidirectional direct-current converter module and a detachable interface; the battery management system comprises a signal acquisition module, a computer and an execution unit. The signal acquisition module is connected with the computer which is connected with the execution unit. According to the electric ship energy equalization charging system, the charging speed is increased through multi-port input, the charging process is optimized through the energy equalization technology, and the health state and the charging efficiency of the battery are ensured. Rapid energy supplementation of the ship and energy balance of the energy storage bin can be achieved, long-time use of the battery is guaranteed, the charging efficiency of the electric ship is improved, and the overall energy management level is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric ship charging, and particularly relates to an energy-balanced charging system for electric ships with multi-port input. Background Art

[0002] With the rapid development of electric ships, the traditional single-port charging technology can no longer meet the requirements of large-scale and high-efficiency charging. The existing charging systems generally have problems such as long charging time, low charging efficiency, and uneven energy distribution. Especially during the charging process of large-capacity battery packs, it is easy to cause energy imbalance between batteries, resulting in shortened battery life and degraded performance. High-power fast charging is accompanied by serious problems such as overheating of the charging batteries, and it is necessary to consider heat dissipation for the batteries, increasing the redundancy of the system. Therefore, there is an urgent need for a charging system that can achieve multi-port input, optimize energy distribution, and ensure balanced charging of each battery unit in the battery pack, so as to improve the charging efficiency of electric ships, extend the battery life, and enhance the overall energy management level. In the prior art, Literature [1]: Li Hu. Research on the Technology of Inland River Ship Charging Stations in Jiangsu under the Background of Carbon Neutrality [J]. Jiangsu Ship, 2022, 39(06): 30-33+5. DOI: 10.19646 / j.cnki.32-1230.2022.06.010. Literature [2]: Zhou Tewei, Shen Yini, Shu Ying, etc. Design of High-Power DC Charging System and Analysis of Short-Circuit Protection [J]. Marine Electric & Electronic Engineering, 2024, 44(09): 25-30. DOI: 10.13632 / j.meee.2024.09.011. Literature [3]: Tian Ye, Liao Zhengyong, Xu Zhenyang, etc. Overview and Application of DC Charging Technology for Pure Battery Ships [J]. Mechanical and Electrical Equipment, 2025, 42(01): 1-7. DOI: 10.16443 / j.cnki.31-1420.2025.01.001.

[0003] Reference [1] points out the existing charging types of charging piles and explains that the capacity of electric ships is much larger than that of electric vehicles, and the charging time is limited. Reference [2] points out that at present, the AC380V AC system is mostly used to connect to the ship's shore power box type to realize the charging of energy storage devices. Although the AC380V power system is relatively conventional and easy to obtain, it uses a large number of cables, has a small charging power and a slow rate, and this type needs to arrange an inverter system in the engine room, occupying a large amount of cabin space. There is a scheme to adopt a containerized power battery replacement mode to reduce the ship's port charging time, but the operation and management mode of charging and replacement is not yet mature, and the lack of standardized power interfaces and plugging methods for replacement devices has led to the lack of large-scale application of this method. There is also a scheme to improve the charging rate by combining shore power, energy storage, and replacement heavy trucks to achieve DC charging, with a charge-discharge rate of 0.5C. For high-power equipment, the charging rate is slow. Reference [3] explains the different specifications of ship charging. High-voltage three-phase AC charging can reduce the number of devices, but the module capacity needs to be considered, and at the same time, the construction cost is increased; low-voltage three-phase AC charging can effectively suppress the influence of common-mode voltage on the onshore power grid, but more charging cables are required. And the use of multi-port charging can match most port equipment and improve the ship's charging rate without upgrading the port. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an energy-balanced charging system for electric ships based on multi-port input, which improves the charging speed through multi-port input, uses energy-balanced technology to optimize the charging process, and ensures the health status and charging efficiency of the battery. The system can realize rapid energy replenishment of the ship and energy balance of the energy storage bin, ensure the long-term use of the battery, improve the charging efficiency of the electric ship, and enhance the overall energy management level.

[0005] The technical solution adopted by the present invention is as follows:

[0006] An energy-balanced charging system for electric ships based on multi-port input, the system includes:

[0007] A multi-port input system, a detachable large-capacity energy storage system, a battery management system, and a load system;

[0008] The multi-port input system includes a dock power supply module, a photovoltaic cell module, a first bidirectional DC converter module, and a first unidirectional DC converter module;

[0009] The dock power supply module is connected to the first bidirectional DC converter module, and the first bidirectional DC converter module is connected to the ship's DC bus; the photovoltaic cell module is connected to the first unidirectional DC converter module, and the first unidirectional DC converter module is connected to the ship's DC bus;

[0010] The detachable large-capacity energy storage system includes a detachable energy storage bin, a second bidirectional DC converter module, and a disassembly interface; the detachable energy storage bin is connected to the disassembly interface, the disassembly interface is connected to the second bidirectional DC converter module, and the bidirectional DC converter module is connected to the ship's DC bus;

[0011] The battery management system includes a signal acquisition module, a computer, and an execution unit; the signal acquisition module is connected to the computer, and the computer is connected to the execution unit;

[0012] The load system includes a second unidirectional DC converter module, a DC load, an inverter module, and an AC load; the DC load is connected to the second unidirectional DC converter module, and the second unidirectional DC converter module is connected to the ship's DC bus to achieve energy transfer; the AC load is connected to the inverter module, and the inverter module is connected to the ship's DC bus. The inverter module converts the DC voltage of the ship's DC bus into an AC power grid to supply energy to the AC load.

[0013] The signal acquisition module is connected to the detachable energy storage bin. After the signal acquisition module collects the battery information of the detachable energy storage bin, it transmits the result to the computer, generates data and transmits it to the execution unit. The execution unit is connected to the second bidirectional DC converter module, and the execution unit controls the charging and discharging of the second bidirectional DC converter module in the detachable large-capacity energy storage system.

[0014] There are at least two sets of the dock power supply module and the first bidirectional DC converter module. The dock power supply module and the first bidirectional DC converter module are connected to the ship's DC bus to quickly charge the ship; the first bidirectional DC converter module converts the onshore power supply into a stable 800v DC voltage and transmits it to the ship's DC bus; the energy input interfaces of each set of the dock power supply module and the first bidirectional DC converter module can be connected to the onshore power supply to charge the ship, and the multi-port input system realizes multiple input of energy.

[0015] The photovoltaic cell module is connected to the ship's DC bus through the first unidirectional DC converter module, and the first unidirectional DC converter module adopts maximum power point tracking control to ensure the maximum input power.

[0016] There are at least two sets of the detachable energy storage bin and the second bidirectional DC converter module. Each set of detachable energy storage bins is connected in a distributed manner and can operate independently to transmit energy to the ship's DC bus. Droop control is adopted to ensure the storage bin and plug-and-use. When the port is equipped with battery swapping equipment, the detachable energy storage bin can be directly replaced to provide energy for the electric ship; when there is only dock charging equipment at the port, the traditional dock charging mode is adopted to supply energy to the detachable energy storage bin.

[0017] The DC loads include on-board instruments, marine electrical lighting, or power electronic devices. The AC loads include marine engines or marine living facilities. The connection method is as follows: Connect the loads and the converters with corresponding characteristics to the marine DC bus to achieve power supply.

[0018] The detachable energy storage bin uses intelligent BMS technology to accurately estimate the state of charge, internal resistance, capacity, and health state of the battery;

[0019] As Figure 3 shown, the battery model is:

[0020] x(t + 1) = Ax(t) + Bu(x) + w(t) (1);

[0021] In Equation (1), x(t + 1) represents the state value of the system at time T = t + 1; x(t) represents the known input variable; u(x) represents the known input variable; w(t) represents the state noise of the system at time t; A represents the state transition function of the battery system; B represents the observation function of the battery system.

[0022]

[0023] In Equation (2), V1(t + 1) represents the voltage of the R1C1 branch of the battery equivalent model at time T = t + 1, V2(t + 1) represents the voltage of the R2C2 branch of the battery equivalent model at time T = t + 1, z(t + 1) represents the state of charge of the battery at time T = t + 1, △T represents the sampling time, R1 represents the polarization internal resistance of the battery equivalent model, C1 represents the polarization capacitance of the battery equivalent model, R2 represents the diffusion resistance of the battery equivalent model, C2 represents the diffusion capacitance of the battery equivalent model, V1(t) represents the voltage of the R1C1 branch of the battery equivalent model at time t, V2(t) represents the voltage of the R2C2 branch of the battery equivalent model at time t, z(t) represents the measured state of charge of the battery at time t, Q1 represents the battery capacity, η(t) represents the battery efficiency, I(t) represents the measured current of the battery at time t, and w(t) represents the state noise of the system at time t.

[0024] The dual extended Kalman filter algorithm is used to solve the optimal estimation. Among them, the first extended Kalman filter is used to estimate the fast-changing state, and the second extended Kalman filter is used to estimate the slow-changing state; the first extended Kalman filter estimates the error, and the second extended Kalman filter estimates the parameters;

[0025] Let x represent the system state, θ represent the system parameters, and P, S, Q, R represent the state covariance error, parameter covariance error, process noise error, and measurement noise error respectively; K, A, C, y represent the Kalman gain, system Jacobian matrix, system Jacobian matrix, and system output respectively;

[0026] The initial conditions of the three parameters of the first extended Kalman filter are determined by Equations (1) and (2). When there is no current flowing in the initial state, the initial states of both RC circuits are 0.

[0027] The expression of the second extended Kalman filter is as follows:

[0028] θ k+1 = θ k + q k (3);

[0029] In Equation (3), θ k+1 represents the battery parameters at the moment T = t + 1; θ k represents the battery parameters at the moment T = t; q k represents the system noise;

[0030]

[0031] In Equation (4), θ represents the battery parameters; R0 and C p are the internal resistance and capacity of the battery, respectively.

[0032] For the convenience of analysis, the extended Kalman filters used for state of charge estimation and internal resistance and capacity estimation are named EKFx and EKFθ, respectively; EKFx is Equation (1); EKFθ is Equation (3);

[0033] To determine the health state of the battery, the SOH calculated based on the capacity degradation method is as follows:

[0034]

[0035] In Equation (5), C i and C o are the battery capacity estimated by the extended Kalman filter and the nominal rated capacity of the battery.

[0036] The battery health state determined by the internal resistance is:

[0037]

[0038] R eol = 1.6R b (7);

[0039] Among them, R eol is the internal resistance of the battery before retirement, R b is the measured internal resistance, and R n is the internal resistance of the unused battery.

[0040] In the battery management system, the system uses an improved droop control algorithm to achieve fast charging and energy balance of the detachable energy storage bin 5.

[0041] The improved droop control algorithm adopts a power-exponential function nested with an arctangent function: the power function accelerates the SOC balancing speed; the exponential function makes the droop curve tend to be smooth, which is conducive to parameter design; the arctangent function limits the output power within the allowable range. The combination of the characteristics of multiple functions realizes a significant improvement in the energy storage balancing speed while ensuring the reasonable distribution of the output power and the stability of the bus voltage;

[0042] The form of the power function is x 2 , which is expressed as (x oci ) n -(x ocavg ) n ;

[0043] The form of the exponential function is a x , which is expressed as

[0044] The form of the arctangent function is arctan(x), which is expressed as arctan[(S oci ) n -(S ocavg ) n ;

[0045] The improved droop coefficient expression is

[0046]

[0047] In Equation (8): R i represents the droop coefficient, and R0 is the initial droop coefficient; S ocavg is the average SOC of the energy storage system; C max is the maximum capacity in the energy storage unit; C i represents the current capacity of the i-th energy storage unit, k is the acceleration factor; n is the convergence factor; i dci < 0 indicates that the energy storage unit is in the charging state, and i dci > 0 indicates that the energy storage unit is in the discharging state; S oci represents the current SOC state of the i-th energy storage unit.

[0048] In the improved droop coefficient, C max / C i is the capacity adjustment factor, and the SOC expression of the energy storage unit during charging can be obtained as:

[0049]

[0050] In Equation (9): S oci (0) represents the initial SOC state of the i-th energy storage unit, U dcref represents the rated reference value of the DC bus voltage, and U dci represents the output voltage of the i-th energy storage unit;

[0051] As can be seen from Equation (9), the variable C is eliminated in the SOC expression i , solving the problem of the influence of the self-capacity difference of the energy storage unit on SOC balance. At the same time, combined with Equation (8), it can be seen that in the case of charging or discharging, the larger the capacity of the energy storage unit, the smaller R i , and the larger the output current.

[0052] The technical effects of an electric ship energy balance charging system based on multi-port input of the present invention are as follows:

[0053] 1) For the electric ship energy balance charging system of the present invention, the multi-port input design can flexibly adapt to different power access methods, such as multiple charging sources such as shore power AC charging piles and DC charging piles being connected simultaneously, ensuring the continuous charging ability of the ship in different environments, reducing the dependence on a single power source, and improving the reliability and adaptability of the system.

[0054] 2) For the electric ship energy balance charging system of the present invention, through the reasonable allocation and management of multiple input ports and the use of a detachable large-capacity energy storage bin, the system can effectively optimize the charging process, reduce the charging time, and improve the overall charging efficiency.

[0055] 3) The electric ship energy balance charging system of the present invention adopts an intelligent battery management system (BMS). By real-time monitoring the voltage, current, and SOC status of each battery, dynamically adjusting the charging strategy of the input port, and realizing precise control of the charging process, it ensures that each battery pack is charged in the optimal working state. This not only improves the charging efficiency but also reduces the risks of overcharging and over-discharging, ensuring the safety and stability of the ship's battery.

[0056] 4) The energy balance control technology of the electric ship energy balance charging system of the present invention can achieve the SOC balance of each single battery in the battery pack, avoiding overcharging and over-discharging phenomena caused by inconsistent voltage or uneven charging among batteries. Through balance control, the use efficiency of each battery unit can be maximized, the battery life can be extended, and the energy loss caused by battery aging can be reduced, thereby reducing the operation cost and maintenance cost. Brief Description of the Drawings

[0057] The present invention will be further described below in conjunction with the drawings and examples;

[0058] Figure 1 is a schematic structural diagram of the electric ship energy balance charging system of the present invention.

[0059] Figure 2 is an improved droop control block diagram of the energy storage system of the present invention.

[0060] Figure 3It is a schematic diagram of the battery equivalent model. Specific implementation mode

[0061] An energy-balanced charging system for electric ships based on multi-port input, which includes: a multi-port input system, a detachable large-capacity energy storage system, a battery management system, and a load system;

[0062] The multi-port input system includes a dock power supply module 1, a photovoltaic cell module 2, a first bidirectional DC converter module 3, and a first unidirectional DC converter module 6;

[0063] The dock power supply module 1 is an electric ship charging pile device that converts alternating current in the power grid into direct current voltage, with Vdc being 800v ± 10%. The input power is 350kW; three groups of FF600R12ME4 IGBT modules are connected in parallel, and the control adopts TMS320F28379D + FPGA real-time scheduling.

[0064] The photovoltaic cell module 2 is a device that converts solar energy into direct current electrical energy. The rated power output of a single photovoltaic cell is 300W, and the working voltage is 36.68v.

[0065] The first bidirectional DC converter module 3 is a device that performs bidirectional step-up and step-down conversion of the DC power supply. The direction from the dock power supply module 1 to the DC bus is step-up, and the direction from the DC bus to the dock power supply module is step-down. The step-up output DC bus voltage Vdc is 800v ± 10%, and the step-down output DC bus voltage Vdc is 400v ± 10%. The module includes several IGBTs, and the model of the IGBT is FF1400R12IP4, with a withstand voltage level of 1200v.

[0066] The first unidirectional DC converter module 6 is to boost the DC power supply output by the photovoltaic cell module and deliver it to the DC bus voltage, with the output DC bus voltage Vdc being 800v ± 10%. The module includes several IGBTs, and the model of the IGBT is FF1400R12IP4, with a voltage level of 1200v.

[0067] The detachable large-capacity energy storage system includes a detachable energy storage bin 5, a second bidirectional DC converter module 3', and a disassembly interface 11;

[0068] The detachable energy storage bin 5 is an energy storage unit composed of lead-acid batteries with a capacity of 3.44MWh, which is composed of 16 parallel-connected 215kW PCSs, and the input / output voltage is 350v - 450v.

[0069] The second bidirectional DC converter module 3' is a device for bidirectional step-up and step-down conversion of DC power. The direction from the detachable energy storage bin module 5 to the DC bus is for step-up, and the direction from the DC bus to the detachable energy storage bin is for step-down. The step-up output DC bus voltage Vdc is 800V ± 10%, and the step-down output DC bus voltage Vdc is 400V ± 10%. The module includes several IGBTs, and the model of the IGBT is FF1400R12IP4, with a withstand voltage rating of 1200V.

[0070] The disassembly interface 11 uses a snap-fastener structure to fasten the low-voltage input module of the bidirectional DC converter to the energy storage bin.

[0071] The battery management system includes a signal acquisition module 9, a computer 12, and an execution unit 13;

[0072] The signal acquisition module 9 is responsible for collecting the ship's voltage, current, and the SOC state of the energy storage. The module includes a DC voltage sensor using LEM LV25-P (±25V input, ±4kV isolation, accuracy 0.2%), and a current sensor using CSLW6B (±600A, 0.5% accuracy, IP67 protection).

[0073] The execution unit 13 is responsible for converting the control signal output by the computer into an action signal. The module includes a relay with the model G4Q, and the withstand voltage exceeds 2400V.

[0074] The load system includes a second unidirectional DC converter module 6', a DC load 7, an inverter module 10, and an AC load 8; The second unidirectional DC converter module 6' is for step-down transmission of the DC bus voltage to the DC load, and the output voltage Vdc is 48V ± 5%. The module includes several MOSFETs, and the model of the MOSFET is OptiMOS TM IPB180N04S4, 40V / 180A. The inverter module 10 converts the DC bus voltage into a 380V AC power supply for use by the on-board AC load. The module includes MOSFETs, using Wolfspeed's CAS325M12HM2 (1200V / 325A, half-bridge module), and the gate drive circuit uses ADI's ADuM4135 (5kV isolation, supporting ns-level switching of SiC MOSFETs).

[0075] Figure 2 It is an improved droop control block diagram for the energy storage system. By multiplying i dci with R i to obtain the virtual voltage drop U vi caused by introducing the droop coefficient, subtracting it from the average virtual voltage drop U avg and then passing it through PI regulation to obtain the virtual voltage drop compensation amount ΔU vi . Figure 2 In GPI2 The transfer function of the PI controller for dynamic current sharing. Through PI regulation, the influence of line impedance is eliminated, enabling the energy storage unit to achieve precise current distribution in proportion. The improved droop control reconstructs the relationship between the droop coefficient and SOC on the basis of traditional droop control to achieve adaptive regulation. In addition, voltage compensation and dynamic current sharing secondary control are introduced. Finally, PWM drive signals are output through a double closed-loop of voltage and current to achieve the stable operation of the energy storage system and the DC microgrid.

[0076] The multi-port input electric ship energy equalization charging system described in the present invention is of great significance for solving the problems of rapid charging of high-power electric ships to reduce battery heating, achieving energy equalization of energy storage units to extend the service life of energy storage units, effectively improving the charging efficiency of electric ships, and achieving energy equalization of each unit in the energy storage bin.

Claims

1. An electric ship energy balancing charging system based on multi-port input, characterized in that The system includes: A multi-port input system, a detachable large-capacity energy storage system, a battery management system, and a load system; The multi-port input system includes a dock power supply module (1), a photovoltaic cell module (2), a first bidirectional DC converter module (3), and a first unidirectional DC converter module (6); The dock power supply module (1) is connected to the first bidirectional DC converter module (3), and the first bidirectional DC converter module (3) is connected to the ship DC bus (4); the photovoltaic cell module (2) is connected to the first unidirectional DC converter module (6), and the first unidirectional DC converter module (6) is connected to the ship DC bus (4); The detachable large-capacity energy storage system includes a detachable energy storage bin (5), a second bidirectional DC converter module (3'), and a disassembly interface (11); The detachable energy storage bin (5) is connected to the disassembly interface (11), the disassembly interface (11) is connected to the second bidirectional DC converter module (3'), and the bidirectional DC converter module (3) is connected to the ship DC bus (4); The battery management system includes a signal acquisition module (9), a computer (12), and an execution unit (13); the signal acquisition module (9) is connected to the computer (12), and the computer (12) is connected to the execution unit (13); The load system includes a second unidirectional DC converter module (6'), a DC load (7), an inverter module (10), and an AC load (8); the DC load (7) is connected to the second unidirectional DC converter module (6'), and the second unidirectional DC converter module (6') is connected to the ship DC bus (4) to achieve energy transfer; the AC load (8) is connected to the inverter module (10), the inverter module (10) is connected to the ship DC bus (4), and the inverter module (10) converts the DC voltage of the ship DC bus (4) into an AC power grid to supply energy to the AC load (8).

2. The electric ship energy balance charging system based on multi-port input according to claim 1, characterized in that: The signal acquisition module (9) is connected to the detachable energy storage bin (5). After the signal acquisition module (9) collects the battery information of the detachable energy storage bin (5), the result is transmitted to the computer (12), and data is generated and transmitted to the execution unit (13). The execution unit (13) is connected to the second bidirectional DC converter module (3), and the execution unit (13) controls the charge and discharge of the second bidirectional DC converter module (3) in the detachable large-capacity energy storage system.

3. The electric ship energy balancing charging system based on multi-port input according to claim 1, characterized in that: The dock power supply module (1) and the first bidirectional DC converter module (3) are at least two groups. The dock power supply module (1) and the first bidirectional DC converter module (3) are connected to the ship DC bus (4) to quickly charge the ship; the first bidirectional DC converter module (3) converts the onshore power supply into a stable 800v DC voltage and transmits it to the ship DC bus (4); the energy input interfaces of each group of the dock power supply module (1) and the first bidirectional DC converter module (3) can be connected to the onshore power supply to charge the ship, and the multi-port input system realizes multiple input of energy.

4. The electric ship energy balancing charging system based on multi-port input according to claim 1, wherein: The detachable energy storage bin (5) and the second bidirectional DC converter module (3') are at least two groups. Each group of detachable energy storage bins (5) is connected in a distributed manner and can operate independently to transmit energy to the ship DC bus (4). When the port is equipped with battery swapping equipment, the detachable energy storage bin (5) is directly replaced to provide energy for the electric ship. When there is only dock charging equipment at the port, the dock charging mode is used to supply energy to the detachable energy storage bin (5).

5. The electric ship energy balance charging system based on multi-port input according to claim 1, characterized in that: The DC load (7) includes on-board instruments, ship electrical lighting, or power electronic devices.

6. The electric ship energy balance charging system based on multi-port input according to claim 1, characterized in that: The AC load (8) includes marine engines or marine living equipment. The connection method is: connecting the load and the converter with corresponding characteristics to the ship DC bus (4) to achieve power supply.

7. The electric ship energy balancing charging system based on multi-port input according to claim 1, characterized in that: The detachable energy storage bin (5) uses intelligent BMS technology to accurately estimate the state of charge, internal resistance, capacity, and health state of the battery. The battery model is: x(t + 1) = Ax(t) + Bu(x) + w(t) (1); In formula (1), x(t + 1) represents the state value of the system at time T = t + 1; x(t) represents the known input variable; u(x) represents the known input variable; w(t) represents the state noise of the system at time t; A represents the state transition function of the battery system; B represents the observation function of the battery system. In formula (2), V1(t + 1) represents the voltage of the R1C1 branch of the battery equivalent model at time T = t + 1, V2(t + 1) represents the voltage of the R2C2 branch of the battery equivalent model at time T = t + 1, z(t + 1) represents the state of charge of the battery at time T = t + 1, △T represents the sampling time, R1 represents the polarization internal resistance of the battery equivalent model, C1 represents the polarization capacitance of the battery equivalent model, R2 represents the diffusion resistance of the battery equivalent model, C2 represents the diffusion capacitance of the battery equivalent model, V1(t) represents the voltage of the R1C1 branch of the battery equivalent model at time t, V2(t) represents the voltage of the R2C2 branch of the battery equivalent model at time t, z(t) represents the measured state of charge of the battery at time t, Q1 represents the battery capacity, η(t) represents the battery efficiency, I(t) represents the measured current of the battery at time t, and w(t) represents the state noise of the system at time t.

8. The electric ship energy balancing charging system based on multi-port input according to claim 1, characterized in that: The dual extended Kalman filter algorithm is used to solve the optimal estimation. Among them, the first extended Kalman filter is used to estimate the fast-changing state, and the second extended Kalman filter is used to estimate the slow-changing state; the first extended Kalman filter estimates the error, and the second extended Kalman filter estimates the parameters. Let x represent the system state, θ represent the system parameters, and P, S, Q, R represent the state covariance error, parameter covariance error, process noise error, and measurement noise error respectively; K, A, C, y represent the Kalman gain, system Jacobian matrix, system Jacobian matrix, and system output respectively. The three parameters of the first extended Kalman filter are determined by formulas (1) and (2) for the initial conditions. There is no current flowing through in the initial state, so the initial states of both RC circuits are 0. The expression of the second extended Kalman filter is as follows: θ k+1 = θ k + q k (3); In formula (3), θ k+1 represents the battery parameters at time T = t + 1; θ k represents the battery parameters at time T = t; q k represents the system noise; In Equation (4), θ represents the battery parameter; R0 and C p are the internal resistance and capacity of the battery, respectively; The extended Kalman filters for state of charge estimation and internal resistance and capacity estimation are named EKFx and EKFθ respectively; EKFx is given by Equation (1); EKFθ is given by Equation (3); To determine the state of health of the battery, the SOH calculated based on the capacity degradation method is as follows: In Equation (5), C i and C o are the battery capacity estimated by the extended Kalman filter and the battery nominal rated capacity, respectively; The state of health of the battery determined by the internal resistance is: R eol = 1.6R b (7); Among them, R eol is the internal resistance before the battery is returned, R b is the measured internal resistance, and R n is the internal resistance of the unused battery.

9. The electric ship energy balancing charging system based on multi-port input according to claim 1, wherein: In the battery management system, the system uses an improved droop control algorithm to achieve fast charging and energy balancing of the detachable energy storage bin (5); The improved droop control algorithm uses a power-exponential function nested with an arctangent function: the power function speeds up the SOC balancing speed; The exponential function makes the droop curve tend to be smooth; the arctangent function limits the output power within the allowable range; The expression for the improved droop coefficient is: In formula (8): R i represents the sag coefficient, and R0 is the initial sag coefficient; S ocavg is the average value of the SOC of the energy storage system; C max is the maximum capacity in the energy storage unit; C i represents the current capacity of the i-th energy storage unit, k is the acceleration factor; n is the convergence factor; i dci < 0 indicates that the energy storage unit is in the charging state, i dci > 0 indicates that the energy storage unit is in the discharging state; S oci represents the current SOC state of the i-th energy storage unit.

10. The electric ship energy balancing charging system based on multi-port input according to claim 1, wherein: Improve C in the sag coefficient max / C i is the capacity adjustment factor, and the SOC expression during the charging of the energy storage unit can be obtained as follows: In formula (9): S oci (0) represents the initial SOC state of the i-th energy storage unit, U dcref represents the rated reference value of the DC bus voltage, U dci represents the output voltage of the i-th energy storage unit; As can be seen from Equation (9), the variable C is eliminated in the SOC expression i , and combined with Equation (8), it can be seen that in the case of charging or discharging, the larger the capacity of the energy storage unit, the smaller the R i , and the larger the output current.

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