An improved distributed collaborative control method for ship-mounted hybrid energy storage system

Abstract

The application discloses an improved distributed collaborative control method for a ship-mounted hybrid energy storage system, and comprises the following steps: obtaining actual current and voltage on a direct-current bus; obtaining current and voltage at an output port of a direct-current converter to obtain output power of the direct-current converter; obtaining voltage output by a storage battery and a super capacitor respectively based on proportional droop and integral droop control methods; obtaining a state of charge of the super capacitor based on the voltage output by the super capacitor; compensating a bus voltage regulation factor to the proportional droop control to accelerate the recovery speed of the state of charge of the super capacitor; obtaining a SoC dynamic adjustment factor based on a novel SoC dynamic adjustment algorithm, so that the storage battery gradually realizes SoC balance in the charging and discharging process, and no circulating current phenomenon occurs; and transient power distribution is realized between the storage battery and the super capacitor, and a high-frequency part of load power change is automatically distributed to the super capacitor, and a low-frequency part is compensated by the storage battery.

Description

Technical Field

[0001] This invention belongs to the field of shipborne microgrids and relates to an improved distributed collaborative control method for shipborne hybrid energy storage systems. Background Technology

[0002] With the development and advancement of DC power systems, dual-electric ships powered by a combination of batteries and supercapacitors have emerged. Supercapacitors have high power density but relatively low energy density. Lithium batteries have high energy density but low power density. Hybrid energy storage systems combine the advantages of both to ensure the sharing of transient power required by the ship's electrical system, achieving peak shaving and valley filling of bus voltage fluctuations. This can effectively reduce pollutant emissions and represents an important research direction for the future development of green shipping.

[0003] Control methods for hybrid energy storage systems can be categorized into three types based on their dependence on communication networks. The first type is distributed control. Distributed control does not rely on any communication infrastructure, thus improving system scalability. For example, the paper "Frequency-coordinating virtual impedance for autonomous power management of DC microgrid" illustrates this. [1] Integrating high-pass and low-pass filters into a hybrid energy storage system divides the load power into high-frequency and low-frequency components. However, the paper employs distributed control, resulting in low control accuracy and failing to consider potential overcharging and over-discharging issues when multiple energy storage units are connected in parallel. The second type is centralized control, which uses a central controller to collect information from the entire system and flexibly implement various control schemes. This is discussed in the paper "A model predictive control system for a hybrid battery-ultracapacitor power source". [2] The first method proposes a model-predictive control scheme that allocates the high-frequency component of the load power to the supercapacitor, while the battery responds to the low-frequency component. This effectively extends the battery's lifespan. However, this method is complex to control and has high communication requirements. The third type is distributed control. Analyzing the above two control methods, distributed control has low accuracy, making it easy for DC bus voltage deviations to exceed allowable limits, potentially damaging voltage-sensitive loads. (See the paper "ASemi-Consensus Strategy Toward Multi-Functional Hybrid Energy Storage System in DC Microgrids") [3]A distributed control scheme based on proportional-integral droop control is introduced, which realizes transient power distribution between batteries and supercapacitors and restores the DC bus voltage to the nominal value. However, circulating current phenomenon occurs when achieving SoC balancing between batteries.

[0004] Meanwhile, due to differences in production, usage, and storage conditions, inconsistencies in the System-on-Chips (SoC) of different energy storage units can easily occur. This may lead to circulating currents in the hybrid energy storage system during operation, and in severe cases, may cause some energy storage units to shut down, affecting the system's lifespan and reducing the stability of the ship's DC microgrid. Furthermore, compared to terrestrial DC microgrids, shipboard DC microgrids require higher stability due to the complex and variable operating conditions and loads. This necessitates faster SoC balancing and recovery speeds for batteries and supercapacitors. To address these issues, a new control method needs to be developed. Summary of the Invention

[0005] To address the above problems, the present invention provides an improved distributed collaborative control method for a shipborne hybrid energy storage system, comprising the following steps:

[0006] Obtain the actual current and voltage on the DC bus;

[0007] Obtain the current and voltage at the output port of the DC-DC converter to get the output power of the DC-DC converter;

[0008] The actual current and voltage on the DC bus are compared with the rated current and voltage to obtain the comparison voltage and comparison current of the DC bus. Based on the proportional droop and integral droop control methods, the output voltages of the battery and supercapacitor are obtained respectively.

[0009] The state of charge of the supercapacitor is obtained based on the voltage output by the supercapacitor.

[0010] The bus voltage regulation factor is compensated into the proportional droop control to accelerate the recovery speed of the supercapacitor's state of charge.

[0011] Based on a novel SoC dynamic adjustment algorithm, a SoC dynamic adjustment factor is obtained, enabling the battery to gradually achieve SoC balance during charging and discharging without circulating current.

[0012] Furthermore, the expression for the bus voltage regulation factor is as follows:

[0013] δ i =G V e vi (14)

[0014] e vi =g i (V th -VOBi (15)

[0015]

[0016] In the formula: V th and V OBi G represents the rated DC bus voltage and the actual output voltage of the i-th battery converter, respectively. v It is a PI regulator, where gi is the pinning gain. It is set to 1 or 0 according to the actual situation of the ship's microgrid. When gi is set to 1, it indicates that the local battery will increase the output power and speed up the recovery of the DC bus voltage. When gi is set to 0, the local battery will not increase the output power for the recovery of the DC bus voltage.

[0017] Furthermore, the expression for the SoC dynamic adjustment factor is as follows:

[0018] ε i =β i ∫∑(X j -X i (18)

[0019]

[0020]

[0021] Where: ε i It is the SoC adjustment factor, C Bi and S avgi Let |N| represent the SoC, rated capacity, and locally measured average SoC of the i-th battery, respectively. i | is the number of neighboring nodes of node i, a s It is the average SoC consistency gain.

[0022] An improved distributed collaborative control device for a shipborne hybrid energy storage system includes:

[0023] Acquisition Module I: Acquires the actual current and voltage on the DC bus;

[0024] Acquisition Module II: Acquires the current and voltage at the output port of the DC-DC converter to obtain the output power of the DC-DC converter;

[0025] Comparison module: Used to compare the actual current and voltage on the DC bus with the rated current and voltage, respectively, to obtain the comparison voltage and comparison current of the DC bus.

[0026] Control module: Used for comparing voltage and current of DC bus, and obtains the output voltage of battery and supercapacitor based on proportional droop and integral droop control methods respectively;

[0027] The module is used to obtain the state of charge of the supercapacitor based on the voltage output by the supercapacitor.

[0028] Compensation module: Used to compensate the bus voltage regulation factor into the proportional droop control, thereby accelerating the recovery speed of the supercapacitor's state of charge.

[0029] Adjustment module: Based on the new SoC dynamic adjustment algorithm, it obtains the SoC dynamic adjustment factor, so that the battery can gradually achieve SoC balance during charging and discharging without circulating current phenomenon.

[0030] The beneficial effects of this invention are as follows: This invention proposes an improved distributed cooperative control method for shipborne hybrid energy storage systems, achieving transient power distribution between batteries and supercapacitors. High-frequency components of load power changes are automatically allocated to the supercapacitors, while low-frequency components are compensated by the batteries. Simultaneously, it enables the supercapacitors to quickly recover their System of Total Energy (SoC) to their initial value after discharge, thus coping with frequent power fluctuations on the bus. Furthermore, it achieves autonomous power distribution and SoC balancing among multiple parallel batteries. It overcomes the circulating current problem by proportionally distributing power based on battery capacity even with different initial SoCs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 Diagram of a DC microgrid for an all-electric ship;

[0033] Figure 2 This is a proportional-integral droop control chart;

[0034] Figure 3 Diagram of battery controller;

[0035] Figure 4 (a) Pole-zero diagram of battery 1, (b) Pole-zero diagram of battery 2, (c) Pole-zero diagram of supercapacitor.

[0036] Figure 5 (a) Bode plot of supercapacitor with varying kvp, (b) Bode plot of battery with varying kvp;

[0037] Figure 6 (a) is the Bode plot of the supercapacitor when Kvi changes, and (b) is the Bode plot of the battery when Kvi changes.

[0038] Figure 7 (a) is the dynamic characteristic diagram of the SoC of battery 1, and (b) is the dynamic characteristic diagram of the SoC of battery 2.

[0039] Figure 8 This is a dynamic characteristic diagram of the DC bus voltage;

[0040] Figure 9 (a) is the discharge current test diagram of the hybrid energy storage system, (b) is the discharge voltage test diagram of the hybrid energy storage system, and (c) is the discharge SOC test diagram of the hybrid energy storage system.

[0041] Figure 10 (a) is the experimental diagram of line impedance current of hybrid energy storage system; (b) is the experimental diagram of line impedance voltage of hybrid energy storage system; (c) is the experimental diagram of line impedance Soc of hybrid energy storage system.

[0042] Figure 11 (a) is the test diagram of charging current of hybrid energy storage system, (b) is the test diagram of line impedance voltage of hybrid energy storage system, and (c) is the test diagram of charging SOC of hybrid energy storage system. Detailed Implementation

[0043] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0044] 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 embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0047] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0048] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0049] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0050] An improved distributed cooperative control method for a shipborne hybrid energy storage system includes the following steps:

[0051] S1: Obtain the actual current and voltage on the DC bus;

[0052] S2: Obtain the current and voltage at the output port of the DC-DC converter to obtain the output power of the DC-DC converter;

[0053] S3: Compare the actual current and voltage on the DC bus with the rated current and voltage respectively to obtain the comparison voltage and comparison current of the DC bus. Based on the proportional droop and integral droop control methods, obtain the output voltage of the battery and the supercapacitor respectively.

[0054] S4: Based on the voltage output by the supercapacitor, obtain the state of charge of the supercapacitor;

[0055] S5: Compensate the bus voltage regulation factor into the proportional droop control to accelerate the recovery speed of the supercapacitor's state of charge.

[0056] S6: Based on a novel SoC dynamic adjustment algorithm, the SoC dynamic adjustment factor is obtained, enabling the battery to gradually achieve SoC balance during charging and discharging without circulating current.

[0057] Steps S1 / S2 / S3 / S4 / S5 / S6 are executed sequentially;

[0058] Figure 1 A diagram of a DC microgrid for an all-electric ship, such as... Figure 1 In the illustrated dual-electric marine DC microgrid, all loads are powered by a hybrid energy storage system, where DC loads, AC loads, other important loads, and propulsion motors are considered loads on the DC bus. In this application's dual-electric marine DC microgrid, all loads are powered by a hybrid energy storage system, where DC loads, AC loads, other important loads, and propulsion motors are considered loads on the DC bus.

[0059] P L =P D +P C +P E (1)

[0060]

[0061] In the formula: P L It is the total load of the hybrid energy storage system, P D P C and P E These represent DC load, AC load, and propulsion motor load, respectively. Bi and P SCi denoted as the output power of the i-th battery and the supercapacitor, respectively.

[0062] Figure 2 The diagram shows the proportional-integral droop control; the DC-DC converters corresponding to the battery and supercapacitor use proportional droop and integral droop control, respectively.

[0063] The DC-DC converters corresponding to the battery and supercapacitor employ proportional droop and integral droop control, respectively. The droop controller generates a voltage reference value V for the voltage control loop. ref Then V ref With the actual output voltage V of the converter o The voltage error is compared, and the corresponding voltage error is further processed by a PI to generate a current reference value for the current control loop. Another PI processes the corresponding current error to generate a control signal for the converter.

[0064]

[0065]

[0066] V ref =V OBi =V OSCi (5)

[0067] In the formula: V OBi and V OSCi Let V be the output voltage of the i-th battery and the supercapacitor converter, respectively, and s be the Laplace operator. th It is the rated value of the DC bus voltage, ΔV max P is the maximum allowable voltage deviation of the system. Bimax It is the maximum output power of the i-th battery, m i and n i These are the droop coefficients for batteries and supercapacitors, respectively.

[0068] According to formulas (3) and (4), the overall droop formula for multiple batteries and supercapacitors connected in parallel can be derived as follows:

[0069]

[0070]

[0071] Where: m eq and n eq It is the equivalent droop factor when multiple batteries and supercapacitors are connected in parallel, and P B and P SC These are their respective output powers, and the power distribution among them is as follows:

[0072]

[0073]

[0074] As shown in formulas (8) and (9), the load power is divided by a high-pass filter and a low-pass filter, where the battery compensates for the low-frequency part of the load power and the supercapacitor undertakes the high-frequency part.

[0075] To address the inherent voltage drop problem of traditional droop control and the long recovery time of supercapacitor SoCs, this application designs a bus voltage regulation factor δ. i The detailed explanation is as follows:

[0076] The SoC of a supercapacitor is defined as:

[0077]

[0078] In the formula: S SCi0 ,P SCi Let and be the initial SoC, output power, and rated capacity of the supercapacitor, respectively. Then, in steady state, equation (3) will become:

[0079]

[0080] Therefore, when the converter's output voltage equals the DC bus voltage, the supercapacitor's output power is zero. This means that in steady state, the supercapacitor's SoC (System-on-Chips) returns to its initial value. This allows the supercapacitor to operate continuously without worrying about SoC depletion.

[0081] However, the self-recovery speed of DC bus voltage is very slow and cannot meet the requirements of frequent load switching on ships. Therefore, this application proposes a bus voltage regulation factor to solve the above problems.

[0082] δ i =G V e vi (14)

[0083] e vi =g i (V th -V OBi (15)

[0084]

[0085] In the formula V th and V OBi These represent the rated DC bus voltage and the actual output voltage of the i-th battery converter, respectively. v It is a PI controller, g i The pinning gain can be set to 1 or 0 depending on the actual conditions of the ship's microgrid. When gi is set to 1, it indicates that the local battery will increase its output power and accelerate the recovery speed of the DC bus voltage. Conversely, when g... iWhen set to 0, the local battery will not increase output power for the recovery of DC bus voltage.

[0086] Figure 3 The diagram shows the battery controller. Based on proportional-integral droop control, the battery controller incorporates a consistency adjustment factor and a DC bus secondary adjustment factor.

[0087] During system operation, the battery output power of different SoCs may be uneven, which may cause some batteries to exit system operation. Therefore, this application proposes a novel SoC dynamic adjustment algorithm to gradually achieve SoC balance during battery charging and discharging without circulating current. The detailed principle is explained below:

[0088] The SoC of the battery is defined as:

[0089]

[0090] The SoC dynamic adjustment factor is:

[0091] ε i =β i ∫∑(X j -X i (18)

[0092]

[0093]

[0094] Where: ε i It is the SoC adjustment factor, S Bi Let , , and Savgi be the SoC, rated capacity, and locally measured average SoC of the i-th battery, respectively. |N i | is the number of neighboring nodes of node i, a s It is the average SoC consistency gain.

[0095] To demonstrate the effectiveness of the proposed SoC dynamic adjustment algorithm, we performed the following verifications:

[0096] From formula (18), it can be seen that when the system is stable,

[0097] ΔX=X j -X i =0 (21)

[0098] Assume C B =C Bi =C Bj S Bi >S Bj Then we have:

[0099]

[0100] Combining formulas (21) and (22), we can obtain: P Bj >P Bi This indicates that the battery will automatically adjust its output power according to different SoCs; the larger the SoC, the more power it will output, until the SoCs are consistent.

[0101] An improved distributed collaborative control device for a shipborne hybrid energy storage system includes:

[0102] Acquisition Module I: Acquires the actual current and voltage on the DC bus;

[0103] Acquisition Module II: Acquires the current and voltage at the output port of the DC-DC converter to obtain the output power of the DC-DC converter;

[0104] Comparison module: Used to compare the actual current and voltage on the DC bus with the rated current and voltage, respectively, to obtain the comparison voltage and comparison current of the DC bus.

[0105] Control module: Used for comparing voltage and current of DC bus, and obtains the output voltage of battery and supercapacitor based on proportional droop and integral droop control methods respectively;

[0106] The module is used to obtain the state of charge of the supercapacitor based on the voltage output by the supercapacitor.

[0107] Compensation module: Used to compensate the bus voltage regulation factor into the proportional droop control, thereby accelerating the recovery speed of the supercapacitor's state of charge.

[0108] Adjustment module: Based on the new SoC dynamic adjustment algorithm, it obtains the SoC dynamic adjustment factor, so that the battery can gradually achieve SoC balance during charging and discharging without circulating current phenomenon.

[0109] Figure 4 (a) Pole-zero plot of battery 1, (b) Pole-zero plot of battery 2, (c) Pole-zero plot of supercapacitor. To clearly analyze the power distribution characteristics and system stability between the batteries and supercapacitor, we assume that the system-on-chip (SoC) of the batteries is the same. We can also draw the corresponding pole-zero plots based on the transfer functions of the output power of the batteries and supercapacitors to the load power. Because poles less than -1 have a relatively small impact on the system, poles less than -1 are not shown in the plots. From the plots, we can see that the poles of the transfer functions of both the batteries and supercapacitors are in the left half-plane, indicating that the system is stable.

[0110] Figure 5(a) Bode plot of the supercapacitor with varying kvp, (b) Bode plot of the battery with varying kvp; as kvp increases, the bandwidth of GB also increases, reducing the overshoot of Gsc, indicating that the supercapacitor reduces the charging current and increases the charging time. Keeping kvp constant and changing kvi, we get... Figure 6 , Figure 6 (a) is the Bode plot of the supercapacitor as Kvi changes, and (b) is the Bode plot of the battery as Kvi changes; from Figure 6 As can be seen, increasing kvi increases the overshoot of GB and decreases the bandwidth of Gsc, indicating that the supercapacitor increases the maximum charging current, reduces the charging time, and accelerates the charging rate. Therefore, we can select appropriate kvp and kvi to enable the supercapacitor to handle suitable high-frequency power while also quickly restoring the SoC.

[0111] Figure 7 (a) is the dynamic characteristic diagram of SoC of battery 1, and (b) is the dynamic characteristic diagram of SoC of battery 2. When the battery is discharging, as λ increases, the amplitude of PB2 decreases continuously, while the amplitude of PB1 remains unchanged. This indicates that under the condition of constant load, increasing λ can enable PB1 to bear more power, that is, accelerate the SoC balance between batteries.

[0112] Figure 8 The figure shows the dynamic characteristics of the DC bus voltage. At both high and low frequencies, the amplitude-frequency response of the DC bus voltage is 20log(400) = 52.0412, indicating that the system maintains a steady-state voltage of 400V. Simultaneously, there is a dip of approximately 0.05Hz in the amplitude-frequency response, indicating that the DC bus voltage drops from 400V during load changes and then recovers to 400V in steady state. These two phenomena demonstrate the automatic recovery function of the DC bus voltage in the hybrid energy storage system.

[0113] To verify the effectiveness of the proposed method, this paper constructs an experimental platform for a shipborne DC microgrid hybrid energy storage system based on StarSim HIL, such as... Figure 9 As shown, Figure 9 (a) shows the discharge current test diagram of the hybrid energy storage system, (b) shows the discharge voltage test diagram of the hybrid energy storage system, and (c) shows the discharge SOC test diagram of the hybrid energy storage system. The system includes modules such as a bidirectional DC / DC converter, DC power supply, resistive load, and supercapacitor. The power supply circuit was simulated based on the NI-PXIe-FPGA-7846R, and the control circuit was implemented based on the TMS320F28379D DSP. While maintaining general applicability, three different experimental cases were studied, and the waveforms obtained from each case were derived.

[0114] from Figure 9To verify the stability and SoC (System-on-Chips) balancing characteristics of the hybrid energy storage system under discharge conditions, the following experiment was designed. The initial SoCs of the two batteries and the supercapacitor were set to 0.9, 0.8, and 0.7, respectively. The line impedances of battery 1, battery 2, and the supercapacitor to the DC bus were all 0. Initially, a 20Ω load was applied, which increased to 80Ω after 16 seconds.

[0115] Figure 10 (a) is the experimental diagram of line impedance current of the hybrid energy storage system; (b) is the experimental diagram of line impedance voltage of the hybrid energy storage system; (c) is the experimental diagram of line impedance Soc of the hybrid energy storage system; from Figure 10 As shown in (a) and (c), due to their different System of Total Energy (SoC), the output current of the batteries differs initially when a load is applied, but both the output current and SoC reach consistency at 8 seconds. At 16 seconds, load fluctuations do not affect the SoC balance among the batteries, and the output current remains consistent. Meanwhile, after the supercapacitor is initially applied to the load, it discharges from 0 to 3 seconds and charges from 3 to 8 seconds. During this phase, its SoC also exhibits a decline and recovery process, eventually remaining at its initial value, and the output current becomes 0. At 16 seconds, the load suddenly increases, showing that the supercapacitor first charges and then discharges, and the SoC ultimately remains at 0.7. This indicates that with a sudden increase in load, the output current and output power of the hybrid energy storage system decrease abruptly, and the supercapacitor absorbs the high-frequency portion of the load power fluctuation. Figure 9 (b) Throughout the test, the DC bus voltage fluctuations caused by load changes were less than 10V.

[0116] Figure 10 To verify the stability and SoC equalization characteristics of the hybrid energy storage system during discharge under inconsistent line impedances, the following experiment was designed. Based on Experiment 1, the line impedances of battery 1, battery 2, and the supercapacitor line were changed to 0.4, 0.1, and 0, respectively.

[0117] Figure 11 (a) is the charging current test diagram of the hybrid energy storage system; (b) is the line impedance voltage test diagram of the hybrid energy storage system; (c) is the charging SOC test diagram of the hybrid energy storage system. Figure 11 As can be seen, the current and SoC results are basically consistent with those of Experiment 1. However, due to the influence of line impedance, there is a voltage difference of about 5V between the output voltages of Battery 1 and Battery 2 converters, and the voltage difference gradually decreases to 0 over time.

[0118] Figure 11To verify the stability and SoC (System-on-Chips) balancing characteristics of the hybrid energy storage system under charging conditions, the following experiment was designed. The initial SoC and line impedance settings of the battery and supercapacitor were the same as in Experiment 1. An initial 100Ω load was applied, and 3kW of power was injected into the system using a constant power supply (CPS) after 13 seconds.

[0119] from Figure 11 As can be seen, at the moment the CPS is activated, to reduce the impact on the battery, the supercapacitor's current becomes negative, then slowly increases to a positive value. This indicates that the supercapacitor is discharging after the emergency charging process ends. Eventually, the output current drops to 0, meaning the supercapacitor's output power is zero at this point. During this process, the battery current slowly decreases to a negative value, and the SoC (System-on-Chips) also slowly increases, indicating that the battery is currently charging, and the power generated by the CPS is evenly distributed among the batteries. The DC bus voltage fluctuates briefly before settling at 400V.

[0120] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0121] [1] YG, WL,

[0122] [2]HREDAK B,AGELID V,MA model predictive control system for a hybridbattery-ultracapacitor power source[J].IEEE Transactions on PowerElectronics.2014,29(3):1469–1479.

[0123] [3]LIN P F,ZHAO T Y.A.Semi-Consensus Strategy Toward Multi-FunctionalHybrid Energy Storage System in DC Microgrids[J].IEEE Transaction on EnergyConversion.2020,35(1):336-346.

Claims

1. An improved distributed cooperative control method for a shipborne hybrid energy storage system, characterized in that: Includes the following steps: Obtain the actual current and voltage on the DC bus; Obtain the current and voltage at the output port of the DC-DC converter to get the output power of the DC-DC converter; The actual current and voltage on the DC bus are compared with the rated current and voltage to obtain the comparison voltage and comparison current of the DC bus. Based on the proportional droop and integral droop control methods, the output voltages of the battery and supercapacitor are obtained respectively. The state of charge of the supercapacitor is obtained based on the voltage output by the supercapacitor. The bus voltage regulation factor is compensated into the proportional droop control to accelerate the recovery speed of the supercapacitor's state of charge. Based on the SoC dynamic adjustment algorithm, the So C dynamic adjustment factor is obtained, enabling the battery to gradually achieve SoC balance during charging and discharging without circulating current phenomenon; The expression for the bus voltage regulation factor is as follows: （14） （15） （16） In the formula: V th and V OBi G represents the rated DC bus voltage and the actual output voltage of the i-th battery converter, respectively. v It is a PI regulator, where gi is the pinning gain. It is set to 1 or 0 according to the actual situation of the ship's microgrid. When gi is set to 1, it indicates that the local battery will increase the output power and speed up the recovery of the DC bus voltage. When gi is set to 0, the local battery will not increase the output power for the recovery of the DC bus voltage. The expression for the SoC dynamic adjustment factor is as follows: （18） （19） （20） In the formula: i It is the SoC adjustment factor, C Bi and S avgi Let |N| represent the SoC of the i-th battery and the locally measured average SoC, respectively. i | is the number of neighboring nodes of node i, a s It is the average SoC consistency gain.

2. The apparatus for an improved distributed cooperative control method for a shipborne hybrid energy storage system according to claim 1, characterized in that: include: Acquisition Module I: Acquires the actual current and voltage on the DC bus; Acquisition Module II: Acquires the current and voltage at the output port of the DC-DC converter to obtain the output power of the DC-DC converter; Comparison module: Used to compare the actual current and voltage on the DC bus with the rated current and voltage, respectively, to obtain the comparison voltage and comparison current of the DC bus. Control module: Used for comparing voltage and current of DC bus, and obtains the output voltage of battery and supercapacitor based on proportional droop and integral droop control methods respectively; The module is used to obtain the state of charge of the supercapacitor based on the voltage output by the supercapacitor. Compensation module: Used to compensate the bus voltage regulation factor into the proportional droop control, thereby accelerating the recovery speed of the supercapacitor's state of charge. Adjustment module: Used to obtain the So C dynamic adjustment factor based on the SoC dynamic adjustment algorithm, so that the battery can gradually achieve SoC balance during charging and discharging, and there is no circulating current phenomenon.

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