Control strategy for droop-free distributed energy storage system considering mismatched line impedance

Abstract

This invention proposes a droop-free distributed energy storage system control strategy that considers mismatched line impedance. Through a consistency control module, each energy storage unit only needs to exchange information with its adjacent communication nodes to obtain the average SOC of the energy storage system without central control, thereby eliminating the dependence on global communication. Through the SOC balancing module and the current sharing module, SOC balancing of energy storage units with different capacities and precise distribution of output current according to the capacity of the energy storage units are achieved. Through the AC signal injection module and the line impedance detection module, the value of mismatched line impedance can be detected, and through the voltage compensation module, the bus voltage deviation caused by line impedance is effectively avoided, maintaining the bus voltage at the rated value and improving the reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of distributed energy storage systems for DC microgrids, and in particular to a droop-free distributed energy storage system control strategy that takes into account mismatched line impedance. Background Technology

[0002] With the large-scale application of new energy sources becoming inevitable and the generation, distribution, and consumption methods urgently needing innovation, microgrids, a new type of new energy utilization platform, have emerged. Compared to AC microgrids, DC microgrids reduce energy loss because they do not require repeated changes in power form, and they do not need to consider frequency, leading to a gradual increase in research on DC microgrids. Since the output power of distributed power sources is random, distributed energy storage systems are needed to ensure power balance in DC microgrids. When multiple energy storage units are used in parallel, the different states of charge (SOC) of units with different capacities will cause some energy storage units to over-discharge or deeply charge, shortening their lifespan. Furthermore, in DC microgrids, the presence of line impedance will prevent traditional droop control from accurately distributing current load according to droop gain, and will also cause a drop in bus voltage. Therefore, it is necessary to detect line impedance information and then adjust the output current of the energy storage units according to their own SOC to ensure that the output current of the energy storage units is accurately distributed proportionally to their capacity, SOC is balanced, and the bus voltage is maintained at the rated voltage. Summary of the Invention

[0003] In view of the defects and shortcomings of the existing technology, the purpose of this invention is to provide a droop-free distributed energy storage system control strategy that takes into account the impedance mismatch of the line.

[0004] The present invention specifically adopts the following technical solution:

[0005] First, a droop-free distributed energy storage system control strategy considering mismatched line impedance is provided, including the following steps:

[0006] 1) At the beginning of each sampling period, the DC-side inductor current i Li DC side output current i i DC side output voltage u i State of charge (SOC) of each energy storage unit i Samples were taken separately;

[0007] 2) The average value of the nth power of the state of charge (SOC) of each energy storage unit is obtained using a consensus algorithm. avg and the average state factor ε avg ;

[0008] 3) The average value of the nth power of the state of charge (SOC) of the energy storage system. avgand the state of charge (SOC) of the energy storage unit i n Subtract the two, multiply the result by the acceleration coefficient λ to obtain the intermediate coefficient x, then take the arctangent function (arctan) of the intermediate coefficient x and multiply it by... Multiply by the maximum rated capacity C of the energy storage unit. max and the rated capacity C of the energy storage unit bati The ratio of these values ​​is used to obtain the SOC adjustment coefficient e. i SOC adjustment coefficient e i The expression is:

[0009]

[0010] 4) Convert the DC side output current i i Divide by the maximum rated current i of the energy storage unit max The result is divided by the current gain b and then multiplied by the SOC adjustment factor e. i The process coefficient 'a' is obtained, and the flow equalization influence factor S is obtained by subtracting the process coefficient 'a' from the coefficient 1. i ;

[0011] 5) Convert the DC side output current i i and DC side output voltage u i The high-frequency ripple current i was obtained by fast Fourier transform. fi and high-frequency ripple voltage u fi The high-frequency ripple voltage u fi Divide by the high-frequency ripple current i fi Obtain the line impedance R linei The line impedance R linei Multiplied by the DC-side output current i i The impedance factor q is obtained, and the DC-side output voltage reference value u is added to the impedance factor q. * Obtain the impedance adjustment coefficient m i Impedance adjustment coefficient m i The expression is:

[0012] m i =u * +R linei i i

[0013] 6) The flow equalization influence factor S i Multiply by the DC-side output voltage u i Obtain the state factor ε i The average value of the state factor ε avg Divide by the flow equalization factor S i Obtain the voltage coefficient z, and then adjust the impedance adjustment coefficient m. iSubtracting the voltage coefficient z, the voltage compensation amount δu is obtained through integration. i ;

[0014] 7) Set the high-frequency rated frequency f * The phase angle θ is obtained through an integrator with an integration coefficient of 2π. k Phase angle θ k Take the sine function sin and multiply it by the amplitude B to obtain the injected AC voltage Δu. i Injected AC voltage Δu i The expression is:

[0015] Δu i =Bsinθ k

[0016] Voltage compensation amount δu i and DC side output voltage reference value u * Add them together, then subtract the DC-side output voltage u. i In addition, the injected AC voltage Δu i Then it passes through the voltage outer loop PI controller G c (s) Obtain the DC side reference current i refi This is compared with the DC-side inductor current i of the local energy storage unit. Li After subtraction, the current passes through the inner loop PI controller G. o (s) obtains the driving voltage u si Drive voltage u si The modulated signal is then obtained by comparing it with the triangular carrier wave.

[0017] Furthermore, in step 3), the acceleration coefficient λ has a range of 0.1 < λ < 1.

[0018] In step 4), the current gain b has a range of 1. <b<10。

[0019] In step 7), the range of amplitude B is 1. <B<10。

[0020] And, a control system for a droop-free distributed energy storage system considering mismatched line impedance, comprising:

[0021] The system includes a consistency control module, a SOC equalization module, a current sharing module, a line impedance detection module, an AC signal injection module, a voltage compensation module, and a voltage and current dual-loop control module.

[0022] The consistency control module obtains the average SOC of the energy storage system by exchanging information between each energy storage unit and its adjacent communication nodes, thereby eliminating the dependence on global communication. The SOC balancing module and current sharing module achieve SOC balancing of energy storage units with different capacities and distribute the output current according to the capacity of the energy storage units. The AC signal injection module and line impedance detection module detect the value of mismatched line impedance, and the voltage compensation module avoids the bus voltage deviation caused by line impedance, maintaining the bus voltage at the rated value.

[0023] Furthermore, at the beginning of each sampling period, the DC-side inductor current i Li DC side output current i i DC side output voltage u i State of charge (SOC) of each energy storage unit i Samples were taken separately;

[0024] In the consensus control module, a consensus algorithm is used to obtain the average value of the nth power of the state of charge (SOC) of each energy storage unit. avg and the average state factor ε avg ;

[0025] In the SOC balancing module, the average value of the nth power of the state of charge (SOC) of the energy storage system is used. avg and the state of charge (SOC) of the energy storage unit i n Subtract the two, multiply the result by the acceleration coefficient λ to obtain the intermediate coefficient x, take the arctangent function of the intermediate coefficient x (arctan), and multiply by... Multiply by the maximum rated capacity C of the energy storage unit. max and the rated capacity C of the energy storage unit bati The ratio of these values ​​is used to obtain the SOC adjustment coefficient e. i SOC adjustment coefficient e i The expression is:

[0026]

[0027] In the current sharing module, the DC side output current i i Divide by the maximum rated current i of the energy storage unit max The result is divided by the current gain b and then multiplied by the SOC adjustment factor e. i The process coefficient 'a' is obtained, and the flow equalization influence factor S is obtained by subtracting the process coefficient 'a' from the coefficient 1. i ;

[0028] In the line impedance detection module, the DC side output current i i and DC side output voltage u iThe high-frequency ripple current i was obtained by fast Fourier transform. fi and high-frequency ripple voltage u fi The high-frequency ripple voltage u fi Divide by the high-frequency ripple current i fi Obtain the line impedance R linei The line impedance R linei Multiplied by the DC-side output current i i The impedance factor q is obtained, and the DC-side output voltage reference value u is added to the impedance factor q. * Obtain the impedance adjustment coefficient m i Impedance adjustment coefficient m i The expression is:

[0029] m i =u * +R linei i i

[0030] In the voltage compensation module, the current sharing influence factor S is... i Multiply by the DC-side output voltage u i Obtain the state factor ε i The average value of the state factor ε avg Divide by the flow equalization factor S i Obtain the voltage coefficient z, and then adjust the impedance adjustment coefficient m. i Subtracting the voltage coefficient z, the voltage compensation amount δu is obtained through integration. i ;

[0031] In the injected AC voltage module, the high-frequency rated frequency f * The phase angle θ is obtained through an integrator with an integration coefficient of 2π. k Phase angle θ k Take the sine function sin and multiply it by the amplitude B to obtain the injected AC voltage Δu. i Injected AC voltage Δu i The expression is:

[0032] Δu i =Bsinθ k

[0033] In the voltage and current dual-loop control module, the voltage compensation amount δu i and DC side output voltage reference value u * Add them together, then subtract the DC-side output voltage u. i In addition, the injected AC voltage Δu i Then it passes through the voltage outer loop PI controller G c (s) Obtain the DC side reference current i refi This is compared with the DC-side inductor current i of the local energy storage unit.Li After subtraction, the current passes through the inner loop PI controller G. o (s) obtains the driving voltage u si Drive voltage u si The modulated signal is then obtained by comparing it with the triangular carrier wave.

[0034] Compared to existing technologies, this invention and its preferred embodiments mainly include a consistency control module, a SOC balancing module, a current sharing module, a line impedance detection module, an AC signal injection module, a voltage compensation module, and a voltage and current dual-loop control module. Through the consistency control module, each energy storage unit only needs to exchange information with its adjacent communication nodes to obtain the average SOC of the energy storage system without central control, thus eliminating dependence on global communication. The SOC balancing module and current sharing module achieve SOC balancing for energy storage units of different capacities and precise distribution of output current according to the capacity of the energy storage units. The AC signal injection module and line impedance detection module can detect the values ​​of mismatched line impedances, and the voltage compensation module effectively avoids bus voltage deviations caused by line impedance, maintaining the bus voltage at its rated value and improving system reliability. Attached Figure Description

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] Figure 1 This is the main circuit diagram of the distributed energy storage system in an embodiment of the present invention;

[0037] Figure 2 This is a control block diagram of a droop-free distributed energy storage system control strategy considering mismatched line impedance in an embodiment of the present invention.

[0038] Figure 3 The above is a waveform diagram of the SOC of the control strategy proposed in the embodiments of the present invention.

[0039] Figure 4 This is a waveform diagram of the DC-side output current of the control strategy proposed in this embodiment of the invention;

[0040] Figure 5 This is a bus voltage waveform diagram of the control strategy proposed in this embodiment of the invention;

[0041] Figure 6 The SOC waveform diagram for a traditional droop control strategy;

[0042] Figure 7 The waveform of the DC-side output current is shown in the traditional droop control strategy. Detailed Implementation

[0043] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0044] 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 exemplary embodiments according to this application. 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.

[0045] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below for detailed explanation:

[0046] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0047] Figure 1 The diagram shown is the main circuit diagram of a distributed energy storage system according to the present invention. The energy storage system consists of two energy storage units connected in parallel via a DC-DC converter. i As the first energy storage unit, R linei R is the line impedance of the first energy storage unit. The line impedances of the two energy storage units are 0.5Ω and 0.4Ω, respectively. load Let i be the load resistance. Li i is the DC-side inductor current. i For DC side output current, u i This is the DC-side output voltage.

[0048] Figure 2The diagram shown is a control block diagram of a droop-free distributed energy storage system control strategy considering mismatched line impedance according to an embodiment of the present invention. It includes a corresponding system for implementing the control strategy of the present invention, comprising the following execution flow:

[0049] At the beginning of each sampling period, the DC-side inductor current i Li DC side output current i i DC side output voltage u i State of charge (SOC) of each energy storage unit i Samples were taken separately;

[0050] In the consensus control module, the average value of the nth power of the state of charge (SOC) of each energy storage unit is obtained using a consensus algorithm. avg and the average state factor ε avg ;

[0051] In the SOC balancing module, the average value of the nth power of the state of charge (SOC) of the energy storage system is used. avg and the state of charge (SOC) of the energy storage unit i n Subtract the two, multiply the result by the acceleration coefficient λ to obtain the intermediate coefficient x, take the arctangent function of the intermediate coefficient x (arctan), and multiply by... Multiply by the maximum rated capacity C of the energy storage unit. max and the rated capacity C of the energy storage unit bati The ratio of these values ​​is used to obtain the SOC adjustment coefficient e. i SOC adjustment coefficient e i The expression is:

[0052]

[0053] In the current sharing module, the DC side output current i i Divide by the maximum rated current i of the energy storage unit max The result is divided by the current gain b and then multiplied by the SOC adjustment factor e. i The process coefficient 'a' is obtained, and the flow equalization influence factor S is obtained by subtracting the process coefficient 'a' from the coefficient 1. i ;

[0054] In the line impedance detection module, the DC side output current i i and DC side output voltage u i The high-frequency ripple current i was obtained by fast Fourier transform. fi and high-frequency ripple voltage u fi The high-frequency ripple voltage u fi Divide by the high-frequency ripple current i fi Obtain the line impedance R linei The line impedance Rlinei Multiplied by the DC-side output current i i The impedance factor q is obtained, and the DC-side output voltage reference value u is added to the impedance factor q. * Obtain the impedance adjustment coefficient m i Impedance adjustment coefficient m i The expression is:

[0055] m i =u * +R linei i i

[0056] In the voltage compensation module, the current sharing influence factor S is... i Multiply by the DC-side output voltage u i Obtain the state factor ε i The average value of the state factor ε avg Divide by the flow equalization factor S i Obtain the voltage coefficient z, and then adjust the impedance adjustment coefficient m. i Subtracting the voltage coefficient z, the voltage compensation amount δu is obtained through integration. i ;

[0057] In the AC voltage injection module, the high-frequency rated frequency f * The phase angle θ is obtained through an integrator with an integration coefficient of 2π. k Phase angle θ k Take the sine function sin and multiply it by the amplitude B to obtain the injected AC voltage Δu. i Injected AC voltage Δu i The expression is:

[0058] Δu i =Bsinθ k

[0059] In the voltage and current dual-loop control module, the voltage compensation amount δu i and DC side output voltage reference value u * Add them together, then subtract the DC-side output voltage u. i In addition, the injected AC voltage Δu i Then it passes through the voltage outer loop PI controller G c (s) Obtain the DC side reference current i refi This is compared with the DC-side inductor current i of the local energy storage unit. Li After subtraction, the current passes through the inner loop PI controller G. o (s) obtains the driving voltage u si Drive voltage u si The modulated signal is then obtained by comparing it with the triangular carrier wave.

[0060] Figure 3 and Figure 6 The figures show the SOC waveforms of the proposed control strategy and the traditional droop control strategy, respectively. When operating in discharge mode, the initial SOC1 and SOC2 of the energy storage unit are 90% and 87%, respectively. In the proposed control strategy, when the SOC is high, the energy storage unit should output a larger current to accelerate the discharge rate, resulting in a faster SOC drop. Conversely, when the SOC is low, the energy storage unit should output a smaller current to reduce the discharge rate, resulting in a slower SOC drop. Ultimately, SOC equilibrium is achieved in 1.26 seconds. In the traditional droop control strategy, the SOC of the two energy storage units reaches equilibrium in 2.14 seconds. Therefore, the SOC equilibrium speed of the proposed control strategy is 0.88 seconds faster than that of the traditional droop control strategy.

[0061] Figure 4 and Figure 7 The figures show the DC-side output current waveforms of the control strategy proposed in this invention and the traditional droop control strategy, respectively. The capacity ratio of the two energy storage units is 3:2. In discharge mode, under the proposed control strategy, the larger capacity energy storage unit releases more current, and the smaller capacity energy storage unit releases less current. The output currents of the two energy storage units eventually reach equilibrium at 1.26s, with output currents of 12A and 8A respectively, satisfying the 3:2 capacity distribution principle. In the traditional droop control strategy, due to the influence of line impedance, the output currents of the two energy storage units are 11.3A and 7.4A respectively after 2.14s, failing to satisfy the 3:2 capacity distribution principle.

[0062] Figure 5 This is a waveform diagram of the bus voltage under the control strategy proposed in this invention. In the proposed control strategy, due to the introduction of an AC signal module, a line impedance detection module, and a voltage compensation module, the bus voltage can be stabilized at 400V, the same as the rated reference voltage. In traditional control strategies, because a virtual impedance is introduced in the droop control, the bus voltage drops, ultimately reaching 373V, deviating from the rated reference voltage.

[0063] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

[0064] The system and method provided in this embodiment can be stored in a computer-readable storage medium in the form of code, implemented as a computer program, and the basic parameter information required for calculation can be input through computer hardware, and the calculation results can be output.

[0065] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0066] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0067] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0068] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0069] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

[0070] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of control strategies for droop-free distributed energy storage systems that take into account mismatched line impedances based on the teachings of this patent. All equivalent variations and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A control strategy for a droop-free distributed energy storage system considering mismatched line impedance, characterized in that, Includes the following steps: 1) At the beginning of each sampling period, the DC-side inductor current i Li DC side output current i i DC side output voltage u i State of charge (SOC) of each energy storage unit i Samples were taken separately; 2) The average value of the nth power of the state of charge (SOC) of each energy storage unit is obtained using a consensus algorithm. avg and the average state factor ε avg ; 3) The average value of the nth power of the state of charge (SOC) of the energy storage system. avg and the state of charge of the energy storage unit to the power of n Subtract the two, multiply the result by the acceleration coefficient λ to obtain the intermediate coefficient x, then take the arctangent function (arctan) of the intermediate coefficient x and multiply it by... Multiply by the highest rated capacity C of the energy storage unit. max and the rated capacity C of the energy storage unit bati The ratio of these values ​​is used to obtain the SOC adjustment coefficient e. i SOC adjustment coefficient e i The expression is: 4) Convert the DC side output current i i Divide by the maximum rated current i of the energy storage unit max The result is divided by the current gain b and then multiplied by the SOC adjustment factor e. i The process coefficient 'a' is obtained, and the flow equalization influence factor S is obtained by subtracting the process coefficient 'a' from the coefficient 1. i ; 5) Convert the DC side output current i i and DC side output voltage u i The high-frequency ripple current i was obtained by fast Fourier transform. fi and high-frequency ripple voltage u fi The high-frequency ripple voltage u fi Divide by the high-frequency ripple current i fi Obtain the line impedance R linei The line impedance R linei Multiplied by the DC-side output current i i The impedance factor q is obtained, and the impedance factor q is added to the DC-side output voltage reference value. Obtain the impedance adjustment coefficient m i Impedance adjustment coefficient m i The expression is: 6) The flow equalization influence factor S i Multiply by the DC-side output voltage u i Obtain the state factor ε i The average value of the state factor ε avg Divide by the flow equalization factor S i Obtain the voltage coefficient z, and then adjust the impedance adjustment coefficient m. i Subtracting the voltage coefficient z, the voltage compensation amount δu is obtained through integration. i ; 7) The high-frequency rated frequency The phase angle θ is obtained through an integrator with an integration coefficient of 2π. k Phase angle θ k Take the sine function sin and multiply it by the amplitude B to obtain the injected AC voltage Δu. i Injected AC voltage Δu i The expression is: Voltage compensation amount δu i and DC side output voltage reference value Add them together, then subtract the DC-side output voltage u. i In addition, the injected AC voltage Δu i Then it passes through the voltage outer loop PI controller G c (s) Obtain the DC side reference current i refi This is compared with the DC-side inductor current i of the local energy storage unit. Li After subtraction, the current passes through the inner loop PI controller G. o (s) obtains the driving voltage u si Drive voltage u si The modulated signal is then obtained by comparing it with the triangular carrier wave.

2. The control strategy for a droop-free distributed energy storage system considering mismatched line impedance as described in claim 1, characterized in that: In step 3), the acceleration coefficient λ has a range of 0.1 < λ < 1.

3. The control strategy for a droop-free distributed energy storage system considering mismatched line impedance as described in claim 1, characterized in that: In step 4), the current gain b has a range of 1. <b<10。 4. The control strategy for a droop-free distributed energy storage system considering mismatched line impedance as described in claim 1, characterized in that: In step 7), the range of amplitude B is 1. <B<10。 5. A control system for a droop-free distributed energy storage system considering mismatched line impedance, characterized in that, include: Consistency control module, SOC equalization module, current sharing module, line impedance detection module, AC signal injection module, voltage compensation module, and voltage and current dual-loop control module; The consistency control module obtains the average SOC of the energy storage system by exchanging information between each energy storage unit and its adjacent communication nodes, thereby eliminating the dependence on global communication. The SOC balancing module and current sharing module achieve SOC balancing of energy storage units with different capacities and distribute the output current according to the capacity of the energy storage units. The AC signal injection module and line impedance detection module detect the value of mismatched line impedance, and the voltage compensation module avoids the bus voltage deviation caused by line impedance and maintains the bus voltage at the rated value. At the beginning of each sampling period, the DC-side inductor current i Li DC side output current i i DC side output voltage u i State of charge (SOC) of each energy storage unit i Samples were taken separately; In the consensus control module, a consensus algorithm is used to obtain the average value of the nth power of the state of charge (SOC) of each energy storage unit. avg and the average state factor ε avg ; In the SOC balancing module, the average value of the nth power of the state of charge (SOC) of the energy storage system is used. avg and the state of charge of the energy storage unit to the power of n Subtract the two, multiply the result by the acceleration coefficient λ to obtain the intermediate coefficient x, take the arctangent function of the intermediate coefficient x (arctan), and multiply by... Multiply by the highest rated capacity C of the energy storage unit. max and the rated capacity C of the energy storage unit bati The ratio of these values ​​is used to obtain the SOC adjustment coefficient e. i SOC adjustment coefficient e i The expression is: In the current sharing module, the DC side output current i i Divide by the maximum rated current i of the energy storage unit max The result is divided by the current gain b and then multiplied by the SOC adjustment factor e. i The process coefficient 'a' is obtained, and the flow equalization influence factor S is obtained by subtracting the process coefficient 'a' from the coefficient 1. i ; In the line impedance detection module, the DC side output current i i and DC side output voltage u i The high-frequency ripple current i was obtained by fast Fourier transform. fi and high-frequency ripple voltage u fi The high-frequency ripple voltage u fi Divide by the high-frequency ripple current i fi Obtain the line impedance R linei The line impedance R linei Multiplied by the DC-side output current i i The impedance factor q is obtained, and the impedance factor q is added to the DC-side output voltage reference value. Obtain the impedance adjustment coefficient m i Impedance adjustment coefficient m i The expression is: In the voltage compensation module, the current sharing influence factor S is... i Multiply by the DC-side output voltage u i Obtain the state factor ε i The average value of the state factor ε avg Divide by the flow equalization factor S i Obtain the voltage coefficient z, and then adjust the impedance adjustment coefficient m. i Subtracting the voltage coefficient z, the voltage compensation amount δu is obtained through integration. i ; In the injected AC signal module, the high-frequency rated frequency is... The phase angle θ is obtained through an integrator with an integration coefficient of 2π. k Phase angle θ k Take the sine function sin and multiply it by the amplitude B to obtain the injected AC voltage Δu. i Injected AC voltage Δu i The expression is: In the voltage and current dual-loop control module, the voltage compensation amount δu i and DC side output voltage reference value Add them together, then subtract the DC-side output voltage u. i In addition, the injected AC voltage Δu i Then it passes through the voltage outer loop PI controller G c (s) Obtain the DC side reference current i refi This is compared with the DC-side inductor current i of the local energy storage unit. Li After subtraction, the current passes through the inner loop PI controller G. o (s) obtains the driving voltage u si Drive voltage u si The modulated signal is then obtained by comparing it with the triangular carrier wave.

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