Method and system for improving quality stability of energy storage access electric energy

Abstract

The invention discloses a method and a system for improving the quality stability of energy storage access electric energy. The method comprises the following steps: establishing a relational expression between the output current of an energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter; based on the established relational expression of the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, obtaining an energy storage grid-connected converter quantity state equation; and designing a novel self-adaptive sliding mode controller based on the energy storage grid-connected converter quantity state equation so as to realize the effective grid-connected control process of the energy storage grid-connected converter. The system comprises a first calculation module, a second calculation module and a control module. The problem that an existing control method is poor in control effect under the complex power grid working condition is solved, and stable tracking and high-quality grid connection of the output current of the energy storage grid-connected converter are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a method and system for improving the stability of power quality connected to energy storage. Background Art

[0002] With the rapid development of renewable energy and smart grids, energy storage systems play an increasingly important role in power systems. Energy storage systems can balance grid loads, improve power supply reliability, and promote the consumption of renewable energy. However, the current control of the grid-connected converter of the energy storage system is directly related to the stability and efficiency of its grid-connected operation. Existing control methods such as BP neural network control and proportional integral control often have problems such as unsatisfactory control effects, slow response speeds, and large tracking errors when dealing with complex and changeable grid conditions. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for improving the stability of power quality of energy storage access, so as to solve the problem that the existing control method has poor control effect under complex power grid conditions, and to achieve stable tracking of the output current of the energy storage grid-connected converter and high-quality grid connection.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for improving the stability of power quality when energy storage is connected, comprising:

[0006] Establishing the relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter;

[0007] Based on the established relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, the state equation of the energy storage grid-connected converter is obtained;

[0008] Based on the state equation of the energy storage grid-connected converter, a new adaptive sliding mode controller is designed to achieve effective control of the energy storage grid-connected converter during grid connection.

[0009] A further improvement of the present invention is to establish a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, as follows:

[0010]

[0011] Where: U e Output voltage of energy storage grid-connected converter; The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dc is the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

[0012] A further improvement of the present invention is that based on the established relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, a state equation of the energy storage grid-connected converter is obtained, including:

[0013] Adoption I e , U dc , U e and the DC side current I of the energy storage grid-connected converter dc Composition of state variables y1, y2: Energy storage grid-connected converter state equation:

[0014]

[0015] In the formula, R in , C in are the filter resistor and capacitor on the AC side of the energy storage grid-connected converter; y(t)=Z1-Z2; wherein Z1 and Z2 represent the states of the switch devices; when switches S1 and S2 are opened and the other two switches are closed, the switch function Z1 is 1; otherwise, the switch function Z2 is 0.

[0016] A further improvement of the present invention is that, based on the state equation of the energy storage grid-connected converter, a new adaptive sliding mode controller is designed to realize the effective control of the energy storage grid-connected converter, including: constructing the new adaptive sliding mode controller in which the error variables are: x1, x2, respectively expressed as: Where: is the derivative of x1 and y1; β1 is the intermediate stability term, which represents the control quantity; let the error variable in the formula Keep stable and set the Lyapunov function W1(t) of the first stage of system operation to:

[0017] A further improvement of the present invention is to derive the Lyapunov function of the first stage of the set system operation: Assume β1=-y1ε=-x1ε, where ε is a design constant and ε>0, and the derivative of the Lyapunov function is rewritten as: The sliding surface λ is set to the error function: λ=x1k1+x2k2; where: k1 and k2 are coefficient constants, which are set to be greater than 0.

[0018] A further improvement of the present invention is that, according to the obtained Lyapunov function derivation and the set Lyapunov function of the first stage of system operation, the Lyapunov function W(t) of the novel adaptive sliding mode controller is obtained and expressed as: Where: is the adaptive sliding mode control law; is the estimated value of the adaptive sliding mode control law; γ is the adaptive gain coefficient; in order to ensure the stability of the operation process of the energy storage grid-connected converter, reduce the impact of harmonics on the stability of the control system, and make the output current of the energy storage grid-connected converter approach the reference current value faster, the appropriate exponential approach law is selected to achieve this. It is expressed as: Where: ρ, p are approximation coefficient constants, which are set to be greater than 0; sgn(λ) is the sign function.

[0019] A further improvement of the present invention is that, according to the exponential reaching law obtained, an adaptive sliding mode control law is obtained. Expressed as: Where: y = [y1y2] T is the set of state variables of the energy storage grid-connected converter; θ(y) is the state function after passing through the sliding surface; f(y) and h(y) are nonlinear functions; the derivative of the Lyapunov function W(t) of the new adaptive sliding mode controller is obtained as follows: Define the intermediate matrix V as: The intermediate matrix V has the following relationship:

[0020] A further improvement of the present invention is that, according to the derivative of the Lyapunov function W(t) of the novel adaptive sliding mode controller and the intermediate matrix V, the intermediate variable expression of the Lyapunov function W(t) of the novel adaptive sliding mode controller is obtained: By selecting appropriate values ​​of k1, k2 and p, we can make |V|>0, thereby ensuring that the matrix V is a positive definite matrix. Then The output current of the energy storage grid-connected converter is controlled under harmonic interference to improve the stability of the power quality of the energy storage access.

[0021] A system for improving the stability of power quality when energy storage is connected, comprising:

[0022] The first calculation module establishes a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter;

[0023] The second calculation module obtains the energy storage grid-connected converter quantity state equation based on the established relationship between the energy storage grid-connected converter output current and the energy storage grid-connected converter output voltage;

[0024] The control module, designs a new adaptive sliding mode controller based on the state equation of the energy storage grid-connected converter to achieve effective control of the energy storage grid-connected converter during grid connection.

[0025] A further improvement of the present invention is that, in the first calculation module, a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter is established as follows:

[0026]

[0027] Where: U e Output voltage of energy storage grid-connected converter; The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dc is the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

[0028] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0029] 1. Adoption of efficient and accurate control solutions:

[0030] The present invention innovatively introduces an efficient and precise control solution, the core of which is the use of a new adaptive sliding mode controller. By designing a specific sliding mode surface and control law, the controller can quickly adjust the control signal when the system changes dynamically, ensuring that the system state slides along the preset sliding mode surface, thereby achieving precise control of the output current of the energy storage grid-connected converter. Traditional control methods often have problems such as response lag and insufficient control accuracy when facing complex working conditions such as power grid fluctuations and load mutations. The present invention effectively solves these problems through the application of an adaptive sliding mode controller, achieving high-precision and rapid tracking of the output current. The present invention significantly improves the current tracking accuracy and response speed, enhances the dynamic response capability of the energy storage system, and provides more stable and reliable power support for the power grid.

[0031] 2. Enhanced robustness of the new adaptive sliding mode controller:

[0032] The adaptive mechanism built into the controller of the present invention is the key to its enhanced robustness. The mechanism can automatically adjust control parameters, such as sliding mode gain, switching function, etc., according to real-time changes in grid conditions (such as voltage fluctuations, frequency offsets, etc.) to maintain stable control of the system. When faced with frequent changes in grid conditions, traditional controllers often require manual intervention or preset multiple control modes for switching, which not only increases the complexity of operation, but may also cause system instability due to untimely response. The adaptive mechanism of the present invention realizes the intelligent adjustment of control parameters and significantly improves the adaptability and stability of the control system. The present invention enhances the robustness and stability of the control system, so that the energy storage grid-connected converter can continue to operate stably in various complex grid environments, thereby improving the reliability and availability of the system.

[0033] 3. Optimize control strategy to improve overall system performance:

[0034] The present invention is not only limited to the innovation of control algorithms, but also comprehensively improves the operating efficiency and grid-connected stability of the energy storage system by optimizing control strategies, such as energy management strategies and grid-connected coordination strategies. These strategies comprehensively consider multiple factors such as the energy state of the energy storage system, grid demand, and renewable energy power generation, and achieve optimal configuration and efficient utilization of energy storage resources. Traditional energy storage systems often lack systematic control strategies, resulting in low utilization of energy storage resources and poor grid-connected stability. The present invention effectively solves these problems by optimizing control strategies, promoting the full absorption of renewable energy and reliable power supply to the power grid. The present invention improves the operating efficiency and grid-connected stability of the energy storage system, and provides strong support for large-scale access to renewable energy and intelligent management of the power grid. At the same time, it also makes positive contributions to promoting the transformation of the energy structure and achieving sustainable development goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a method for improving the stability of power quality of energy storage access.

[0036] Figure 2 Schematic diagram of the overall structure of the grid-connected converter control of the energy storage system.

[0037] Figure 3 This is a comparison chart between the output current of the energy storage grid-connected converter and the reference current.

[0038] Figure 4 Schematic diagram of THD of output current of energy storage grid-connected converter.

[0039] Figure 5 The present invention is a structural block diagram of a system for improving the stability of power quality of energy storage access. DETAILED DESCRIPTION

[0040] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0041] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0042] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0043] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0044] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0045] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0046] Example 1

[0047] like Figure 1 As shown, this embodiment provides a method for improving the stability of power quality of energy storage access, including:

[0048] Establishing the relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter;

[0049] Based on the established relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, the state equation of the energy storage grid-connected converter is obtained;

[0050] Based on the state equation of the energy storage grid-connected converter, a new adaptive sliding mode controller is designed to achieve effective control of the energy storage grid-connected converter during grid connection.

[0051] In this embodiment, the energy storage grid-connected converter output current I e The output voltage U of the energy storage grid-connected converter e The following relationship exists:

[0052]

[0053] Where: The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dcis the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

[0054] In order to obtain the state equation of the energy storage grid-connected converter, I e , U dc , U e and the DC side current I of the energy storage grid-connected converter dc Composition of state variables y1, y2:

[0055]

[0056] Energy storage grid-connected converter state equation:

[0057]

[0058] In the formula, R in , C in is the AC side filter resistor and capacitor of the energy storage grid-connected converter; y(t) = Z1-Z2. Where Z1 and Z2 represent the states of the switch devices. When switches S1 and S2 are open and the other two switches are closed, the switch function Z1 is 1; otherwise, the switch function Z2 is 0.

[0059] In this embodiment, if Figure 2 As shown in the figure, in the process of designing a new adaptive sliding mode controller to achieve effective grid-connected control of energy storage grid-connected converters, the appropriate selection of Lyapunov function plays a vital role. According to the dynamic characteristics and control requirements of energy storage grid-connected converters, an accurate mathematical model is constructed. In order to ensure that the system can stably reach and remain on the sliding surface, it is necessary to select a suitable Lyapunov function. By minimizing the derivative of the function (that is, the rate of change of the system energy function over time), it is ensured that the system state gradually converges to the sliding surface during the control process and remains stable thereafter. The specific process is:

[0060] The error variables in constructing a new adaptive sliding mode controller are: x1, x2, which can be expressed as:

[0061]

[0062] Where: is the derivative of x1 and y1; β1 is the intermediate stability term, which represents the control amount.

[0063] Let the error variable in formula (4) be Keep stable and set the Lyapunov function W1(t) of the first stage of system operation to:

[0064]

[0065] Derivative of formula (5):

[0066]

[0067] Assume β11 = -y1ε = -x1ε, where ε is a design constant and ε>0, then formula (6) can be rewritten as:

[0068]

[0069] The present invention sets the sliding surface λ as the error function:

[0070] λ=x1k1+x2k2 (8)

[0071] Where: k1 and k2 are coefficient constants, which are set to be greater than 0 in the present invention. The Lyapunov function W(t) of the novel adaptive sliding mode controller can be expressed as:

[0072]

[0073] Where: is the adaptive sliding mode control law; is the estimated value of the adaptive sliding mode control law; γ is the adaptive gain coefficient. In order to ensure the stability of the operation process of the energy storage grid-connected converter, reduce the impact of harmonics on the stability of the control system, and make the output current of the energy storage grid-connected converter approach the reference current value faster, this can be achieved by selecting an appropriate exponential approaching law. Exponential approaching law It can be expressed as:

[0074]

[0075] Where: ρ, p are approach coefficient constants, which are set to be greater than 0 in the present invention; sgn(λ) is the sign function. Then the adaptive sliding mode control law It can be expressed as:

[0076]

[0077] Where: y = [y1 y2] T is the set of state variables of the energy storage grid-connected converter; θ(y) is the state function after passing through the sliding surface; f9y) and h(y) are nonlinear functions. Based on this, the derivative of the Lyapunov function W(t) of the new adaptive sliding mode controller is:

[0078]

[0079] Define the intermediate matrix V as:

[0080]

[0081] The intermediate matrix V has the following relationship:

[0082]

[0083] According to formula (14), another expression of formula (12) can be obtained:

[0084]

[0085] By selecting appropriate values ​​of k1, k2 and p, we can make |V|>0, thereby ensuring that the matrix V is a positive definite matrix. Then Controlling the output current of the energy storage grid-connected converter under harmonic interference can effectively improve the stability of the power quality of energy storage access.

[0086] Example 2

[0087] Under normal grid-connected operation conditions, after the control method of the present invention is implemented, the comparison between the output current of the energy storage grid-connected converter and the current reference value and the total harmonic distortion rate (THD) of the output current are as follows: Figure 3 and Figure 4 shown.

[0088] Under the unique control strategy of the present invention, the energy storage grid-connected converter exhibits excellent current tracking performance, and can accurately lock and closely follow the grid-connected reference current value of the power generation system in a very short time - only 0.025 seconds, and the error in the tracking process is extremely small, only 0.012, reflecting a high degree of accuracy and response speed. Furthermore, the control method ensures the quality of the output current, and its total harmonic distortion (THD) is as low as 0.46%, which is significantly lower than the threshold usually required, indicating that the output current has almost no obvious harmonic distortion phenomenon, which perfectly meets the strict requirements of actual grid access and provides a strong guarantee for the stable operation of the power system.

[0089] Example 3

[0090] like Figure 5 As shown, this embodiment provides a system for improving the stability of power quality of energy storage access, including:

[0091] The first calculation module establishes a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter;

[0092] The second calculation module obtains the energy storage grid-connected converter quantity state equation based on the established relationship between the energy storage grid-connected converter output current and the energy storage grid-connected converter output voltage;

[0093] The control module, designs a new adaptive sliding mode controller based on the state equation of the energy storage grid-connected converter to achieve effective control of the energy storage grid-connected converter during grid connection.

[0094] In this embodiment, in the first calculation module, a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter is established as follows:

[0095]

[0096] Where: U e Output voltage of energy storage grid-connected converter; The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dc is the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

[0097] Example 4

[0098] This embodiment provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for improving the stability of power quality connected to energy storage are implemented.

[0099] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0100] The present application is described with reference to the flowcharts and / or block diagrams of the methods, systems and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A system that specifies the functions of a box or multiple boxes.

[0101] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0102] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0103] In summary, the present invention has the following advantages:

[0104] 1. The present invention adopts an efficient and accurate control scheme and a new adaptive sliding mode controller, which can achieve efficient and accurate control of the output current of the energy storage grid-connected converter and improve the current tracking accuracy and response speed.

[0105] 2. The present invention adopts a novel adaptive sliding mode controller with strong robustness. The controller has an adaptive mechanism that can automatically adjust parameters to adapt to changes in power grid conditions, thereby improving the robustness and stability of the control system.

[0106] 3. The present invention improves the operating efficiency and grid-connected stability of the grid-connected converter of the energy storage system by optimizing the control strategy, thereby promoting the consumption of renewable energy and the reliable power supply of the power grid.

[0107] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0108] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for improving the stability of power quality when energy storage is connected, characterized in that: include: Establishing the relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter; Based on the established relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter, the state equation of the energy storage grid-connected converter is obtained; Based on the state equation of the energy storage grid-connected converter, a new adaptive sliding mode controller is designed to achieve effective control of the energy storage grid-connected converter during grid connection.

2. A method for improving the stability of power quality of energy storage access according to claim 1, characterized in that: The relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter is established as follows: Where: U e Output voltage of energy storage grid-connected converter; The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dc is the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

3. A method for improving the stability of power quality of energy storage access according to claim 2, characterized in that: Based on the established relationship between the output current and the output voltage of the energy storage grid-connected converter, the state equation of the energy storage grid-connected converter is obtained, including: Adoption I e , U dc , U e and the DC side current I of the energy storage grid-connected converter dc Composition of state variables y1, y2: Energy storage grid-connected converter state equation: In the formula, R in , C in are the filter resistor and capacitor on the AC side of the energy storage grid-connected converter; y(t)=Z1-Z2; wherein Z1 and Z2 represent the states of the switch devices; when switches S1 and S2 are opened and the other two switches are closed, the switch function Z1 is 1; otherwise, the switch function Z2 is 0.

4. A method for improving the stability of power quality of energy storage access according to claim 3, characterized in that: Based on the state equation of the energy storage grid-connected converter, a new adaptive sliding mode controller is designed to achieve effective grid-connected control of the energy storage grid-connected converter, including: the error variables in the construction of the new adaptive sliding mode controller are: x1, x2, respectively expressed as: Where: is the derivative of x1 and y1; β1 is the intermediate stability term, which represents the control quantity; let the error variable in the formula Keep stable and set the Lyapunov function W1(t) of the first stage of system operation to:

5. A method for improving the stability of power quality of energy storage access according to claim 4, characterized in that: Run the first stage of Lyapunov function derivation for the set system: Assume β1=-y1ε=-x1ε, where ε is a design constant and ε>0, and the derivative of the Lyapunov function is rewritten as: The sliding surface λ is set to the error function: λ=x1k1+x2k2; where: k1 and k2 are coefficient constants, which are set to be greater than 0.

6. A method for improving the stability of power quality of energy storage access according to claim 5, characterized in that: According to the obtained Lyapunov function derivative and the set Lyapunov function of the first stage of system operation, the Lyapunov function W(t) of the new adaptive sliding mode controller is expressed as: Where: is the adaptive sliding mode control law; is the estimated value of the adaptive sliding mode control law; γ is the adaptive gain coefficient; in order to ensure the stability of the operation process of the energy storage grid-connected converter, reduce the impact of harmonics on the stability of the control system, and make the output current of the energy storage grid-connected converter approach the reference current value faster, the appropriate exponential approach law is selected to achieve this. It is expressed as: Where: ρ, p are approximation coefficient constants, which are set to be greater than 0; sgn(λ) is the sign function.

7. A method for improving the stability of power quality of energy storage access according to claim 6, characterized in that: According to the exponential reaching law obtained, the adaptive sliding mode control law is obtained Expressed as: Where: y = [y1 y2] T is the set of state variables of the energy storage grid-connected converter; θ(y) is the state function after passing through the sliding surface; f(y) and h(y) are nonlinear functions; the derivative of the Lyapunov function W(t) of the new adaptive sliding mode controller is obtained as follows: Define the intermediate matrix V as: The intermediate matrix V has the following relationship:

8. A method for improving the stability of power quality of energy storage access according to claim 7, characterized in that: According to the derivative of the Lyapunov function W(t) of the new adaptive sliding mode controller and the intermediate matrix V, the intermediate variable expression of the Lyapunov function W(t) of the new adaptive sliding mode controller is obtained: By selecting appropriate values ​​of k1, k2 and p, we can make |V|>0, thereby ensuring that the matrix V is a positive definite matrix. Then The output current of the energy storage grid-connected converter is controlled under harmonic interference to improve the stability of the power quality of the energy storage access.

9. A system for improving the stability of power quality when connected to energy storage, characterized in that: include: The first calculation module establishes a relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter; The second calculation module obtains the energy storage grid-connected converter quantity state equation based on the established relationship between the energy storage grid-connected converter output current and the energy storage grid-connected converter output voltage; The control module, designs a new adaptive sliding mode controller based on the state equation of the energy storage grid-connected converter to achieve effective control of the energy storage grid-connected converter during grid connection.

10. A system for improving the stability of power quality when energy storage is connected to the power supply according to claim 9, characterized in that: In the first calculation module, the relationship between the output current of the energy storage grid-connected converter and the output voltage of the energy storage grid-connected converter is established as follows: Where: U e Output voltage of energy storage grid-connected converter; The output current I of the energy storage grid-connected converter e The differential of; μ is the operating state coefficient of the switching device in the energy storage grid-connected converter; U dc is the DC side voltage of the energy storage grid-connected converter; L in It is the filter inductor on the AC side of the energy storage grid-connected converter.

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