Small-signal frequency domain impedance rapid modeling method for grid-connected system of network construction type energy storage equipment

Abstract

The invention discloses a small-signal frequency domain impedance rapid modeling method for a grid-connected system of a network construction type energy storage device. The method comprises the following steps: obtaining topology and parameters of the grid-connected system of the network construction type energy storage device; constructing a time domain state space model of the network construction type energy storage equipment, wherein the time domain state space model comprises an equipment internal circuit structure parameter model and a control loop signal model; constructing a time domain state space model of the basic element of the power system; linearizing the time domain state space model of the networking type energy storage equipment and the time domain state space model of the basic element of the power system to obtain a small signal model, and further obtaining a port discrete time domain Norton equivalent model; and performing z change on the port discrete time domain Norton equivalent model to obtain a port discrete frequency domain impedance model, and performing mapping from a discrete domain to a continuous domain on the port discrete frequency domain impedance model to obtain a port continuous frequency domain impedance model. According to the invention, through a multi-mapping impedance analysis method, the complex power system modeling process is simplified, and the modeling efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of power system impedance modeling and analysis, and in particular to a method for rapid modeling of small signal frequency domain impedance of a grid-connected energy storage device system. Background Art

[0002] In order to solve the volatility problem of renewable energy power generation and balance the grid load, energy storage devices are widely used in power systems. Traditional grid-connected energy storage devices will cause the system inertia to decrease and the stability to deteriorate. Therefore, grid-connected energy storage devices with voltage source characteristics are increasingly valued and used to improve system stability. On the other hand, the interaction between power electronic equipment and the system is complex, which can easily cause oscillation, leading to system instability or even decoupling. Therefore, the study of the stability of the grid-connected system of grid-connected energy storage devices has received widespread attention, and impedance analysis method is one of the important means.

[0003] When studying the system where the inverter and the grid interact, the traditional impedance analysis method divides the two into two independent subsystems, and constructs their own frequency domain impedance models based on their respective control loops and circuit structures. Since the impedance models of the two subsystems are independent of each other and are not affected by each other, when the structure and parameters of one side change, the impedance model of the other side will not change. However, when studying large-scale complex systems containing grid-connected inverters, the traditional impedance analysis method has certain limitations. This method requires manual derivation of the frequency domain impedance transfer function of the subsystem port based on the series and parallel relationship of the devices within the subsystem. When the system structure changes, the series and parallel relationship of the component devices changes, and it is often necessary to manually derive the frequency domain impedance transfer function of the entire subsystem again, which is very inefficient. Summary of the invention

[0004] The purpose of the present invention is to overcome the disadvantage that the impedance analysis method in the prior art needs to manually derive the frequency domain impedance transfer function of the subsystem port according to the series and parallel relationship of the internal devices of the subsystem. When the system structure changes, the series and parallel relationship of the component devices changes, and it is often necessary to manually derive the frequency domain impedance transfer function of the entire subsystem again, which is very inefficient. A method for rapid modeling of small signal frequency domain impedance of a grid-connected system of a grid-connected energy storage device is provided.

[0005] The purpose of the present invention is achieved through the following technical solutions: The small signal frequency domain impedance rapid modeling method of the grid-connected system of the grid-connected energy storage device includes the following steps: Obtain the topology and parameters of the grid-connected system of the grid-connected energy storage device, perform steady-state power flow calculation based on the topology and parameters, and obtain the steady-state values ​​of voltage and current of each component as the balance point for subsequent linearization; Construct a time-domain state-space model of a grid-type energy storage device, which includes a device internal circuit structure parameter model and a control loop signal model; Construct time-domain state-space models of basic components of power systems; The time-domain state-space model of the grid-type energy storage device and the time-domain state-space model of the basic components of the power system are linearized to obtain a small signal model, and based on the small signal model, a discrete time-domain Norton equivalent model of the port is obtained; The port discrete time domain Norton equivalent model is z-transformed to obtain the port discrete frequency domain impedance model, and the port discrete frequency domain impedance model is mapped from discrete domain to continuous domain to obtain the port continuous frequency domain impedance model.

[0006] Preferably, the topology and parameters of the grid-connected system of the grid-connected energy storage device are obtained, steady-state power flow calculation is performed based on the topology and parameters, and the steady-state values ​​of voltage and current of each component are obtained as the balance point of subsequent linearization. This process is completed by iterative Newton-Raphson method.

[0007] Preferably, the time-domain state-space model of the grid-type energy storage device and the time-domain state-space model of the basic elements of the power system are linearized to obtain a small signal model, specifically: Differential algebraic equations are established for the independent and coupled relationships between the internal circuit structure of the device and the control loop. The differential terms of the differential algebraic equations are set to zero to solve the steady-state state variable values ​​for subsequent linearization initial values. The expression of the differential algebraic equation is: Among them, x, z and v are all the state variables, algebraic variables and input variables of the component respectively; According to the differential algebraic equation, differential linearization is performed to obtain the small signal model of the grid-type energy storage device and the basic components of the power system. The small signal model expression is: Among them, Δi dq and Δu dq They represent the current and voltage changes in dq coordinates determined by PLL respectively.

[0008] As a preferred embodiment, the process of obtaining the port discrete time-domain Norton equivalent model based on the small signal model is as follows: the small signal model is discretized to form a generalized discrete time-domain Norton equivalent model, the topological structure and subsystem division of the power grid are combined, some variables of the components in the subsystem are eliminated, and the port discrete time-domain Norton equivalent model is aggregated to form, wherein the small signal model is discretized to form a generalized discrete time-domain Norton equivalent model, specifically: The small signal model is discretized, and trapezoidal integration is performed according to the continuous time domain small signal model of the component. After sorting, the expression is as follows: Will Defined as the historical current term Δh(t), after sorting, the discrete time domain Norton equivalent model including the historical current term is obtained, and the expression is: The above formula is a unified expression of the generalized discrete time-domain Norton equivalent model of each component.

[0009] Preferably, the topological structure of the power grid is combined with the subsystem division, some variables of the components in the subsystem are eliminated, and the discrete time-domain Norton equivalent model of the port is aggregated to form, specifically: According to the generalized discrete time-domain Norton equivalent model of each non-resistance element of the subsystem, a subsystem equivalent model is integrated, and the expression is as follows: Δh tot (t) = A tot Δh tot (t-Dt)+B tot Δu dq,dyn (t-Dt) Among them, A tot and B tot are the A of the non-resistance components of the subsystem d and B d The block diagonal matrix, Δu dq,dyn is the Δu of the non-resistive elements of the subsystem dq The column vector formed by Using the node analysis method and the correlation matrix, the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current is obtained, and its expression is as follows: Among them, M nb 、M n_dyn and M np are the association matrices of node-branch, node-non-resistance branch and node-port, Δi dq,n and Δu dq,n are the subsystem node current and voltage column vectors, Δu dq,p and Δi dq,p are the column vectors of the subsystem port voltage and current, Δu dq,dyn is the voltage column vector of the non-resistance components of the subsystem, C tot C is the non-resistive element of the subsystem d The block diagonal matrix D tot is the D of all components of the subsystem d The block diagonal matrix formed; According to the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current, and the subsystem equivalent model, the subsystem internal voltage and current column vector is eliminated to obtain the subsystem port discrete time domain Norton equivalent model, whose mathematical expression is as follows: Among them, A D , B D , C D and D D It is a coefficient matrix that reflects the state variables of all components in the subsystem.

[0010] Preferably, the discrete time-domain Norton equivalent model of the port is subjected to z-change to obtain the discrete frequency-domain impedance model of the port, specifically: According to the subsystem port discrete time domain Norton equivalent model, mathematical processing is performed to obtain an equivalent model with the port current as the input variable and the port voltage as the output variable. The processed expression is as follows: To express it intuitively, the expression is rewritten as follows: Among them, each coefficient matrix can be obtained by substituting the matrix calculation described above; According to the above expression, z-transform is performed, with the port current as input and the port voltage as output, to obtain the matrix expression of the discrete frequency domain impedance transfer function of the subsystem, as shown below: H(z)=C sys (zI-A sys ) -1 B sys +D sys Among them, C sys A represents the coefficient matrix of the subsystem port output variables. sys Represents the coefficient matrix of the subsystem internal state variables, B sys The coefficient matrix representing the input variables of the subsystem port, D sys represents the direct transfer matrix of the subsystem port, and H(z) is a two-dimensional matrix of the following form: The four parameters of the two-dimensional matrix are solved separately, using H dd Taking the solution of (z) as an example, its zero-pole gain representation is as follows: Among them, w i 、v j and K zdd They are the zero, pole and gain of the discrete domain impedance transfer function, and the gain Kzdd The size is: K zdd =D sys，dd Pole v j A sys The characteristic root of corresponds to the following result: det|zI-A sys |=0 Zero point w i A D The characteristic root of corresponds to the following result: det|zI-A D |=0; The remaining two-dimensional matrix parameters can be obtained similarly.

[0011] Preferably, the discrete frequency domain impedance model of the port is mapped from the discrete domain to the continuous domain to obtain the continuous frequency domain impedance model of the port, which is specifically: The port discrete frequency domain impedance model is mapped from the discrete domain to the continuous domain using bilinear transformation, and the mathematical expression of the bilinear transformation is: The port impedance transfer function matrix expression of the continuous domain is: To solve Z dd (s) as an example, its zero-pole gain representation is as follows: According to the bilinear transformation process, the zeros, poles and gains of the continuous domain impedance transfer function are respectively obtained, and the mathematical expressions are as follows: Among them, z i 、p j and K sdd They are the zero, pole and gain of the impedance transfer function in the continuous domain, and z0 and s0 are 1 and 0 respectively.

[0012] The beneficial effects of the present invention are as follows: the present invention simplifies the complex power system modeling process and improves the modeling efficiency through the impedance analysis method of multiple mappings. When the topological structure of the system changes, it is only necessary to modify the corresponding association matrix and branch description without rebuilding the model of the entire system, so that the modeling method has stronger scalability. The present invention is applicable to systems containing different types of components, has high scalability, and can meet the modeling requirements of power systems of different complexities and scales. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a flow chart of the present invention; Figure 2 It is a schematic diagram of the circuit structure and control circuit of the grid-connected energy storage system; Figure 3 It is a schematic diagram of the discrete time-domain Norton equivalent model of the component aggregated into the discrete time-domain Norton equivalent model of the subsystem port; Figure 4 This is a comparison diagram of Bode plot results obtained by using port impedance theory analysis and frequency scanning in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0014] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concept of the example embodiments to those skilled in the art.

[0015] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0016] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0017] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0018] Example: A fast modeling method for small signal frequency domain impedance of grid-connected energy storage equipment, such as Figure 1 As shown, the following steps are included: S100, grid-connected energy storage device grid-connected system power flow calculation, obtain the voltage and current steady-state values ​​of each component port, this process is completed by the Newton-Raphson method iteration; S200, establishing differential algebraic equations based on the internal circuit structure of the grid-type energy storage device and the independence and coupling relationship of the control loop, and constructing a continuous time domain state space model; S300, constructing a continuous time-domain state-space model of common basic elements of a power system, wherein the common basic elements include three-phase resistance, three-phase impedance, and three-phase admittance; S400, linearizing the continuous time-domain state space model of the grid-type energy storage device and common basic components to obtain their small signal models, and then discretizing them in the time domain to obtain a discrete time-domain Norton equivalent model including a historical current term; S500, divides the system into two subsystems, uses node analysis and correlation matrix to eliminate the voltage and current of the internal components of the subsystem, and aggregates to form a discrete time-domain Norton equivalent model of the subsystem port; S600, z-transforming the discrete time-domain Norton equivalent model of the port to obtain a discrete frequency-domain second-order impedance matrix under dq coordinates, wherein four parameters of the matrix are expressed in the form of zero-pole gains, and their specific values ​​can be solved by the coefficient matrix of the discrete time-domain Norton model of the port; S700, mapping the discrete frequency domain second-order impedance matrix of the port to the s domain through bilinear transformation to obtain a continuous frequency domain second-order impedance matrix, wherein the four parameters of the matrix are also expressed in the form of zero-pole gains, and their specific values ​​are obtained by transforming the discrete frequency domain second-order impedance matrix of the port.

[0019] In S200 of this embodiment, as a preferred embodiment, differential algebraic equations are established according to the internal circuit structure of the grid-type energy storage device and the independence and coupling relationship of the control loop to construct a continuous time domain state space model. Figure 2 The circuit structure and control loop of a grid-type energy storage device in a preferred embodiment of the present invention are shown, and its differential algebraic equations include: According to the control loop, there is the following formula: Among them, θ k ,x1,x2,x3,x4 are the control loop state variables, k p,k ,k q,k ,K pvd ,K ivd ,K pvq ,K ivq ,K pcd ,K icd ,K pcq ,K icq They are Figure 2 The gain and PI parameters of the control loop in is a given reference value, u d ,u q ,i d ,iq ,i fd ,i fq They are Figure 2 The superscript "c" in PCC and the voltage and current values ​​of each branch indicates that the parameter is obtained through Park transformation in the control system. According to the circuit structure, the LCL filter circuit on the AC side of the grid-connected inverter has the following formula: Among them, L f ,C f ,L g for Figure 2 The filter circuit parameters in i Cd ,i Cq ,u Cd ,u Cq They are the current and voltage values ​​of the filter capacitor branch, respectively. The superscript "s" indicates that the parameter is obtained under the dq coordinate of the synchronous rotation of the power grid. According to the above two-part equation group, the continuous time domain state space model of the state variables of the grid-type energy storage device 11 is obtained.

[0020] In S300 of this embodiment, as a preferred embodiment, a continuous time domain state space model of common basic elements of the power system is constructed, including: For three-phase resistance, the equation is satisfied in dq coordinates: G R u dq =i dq According to the equation, the discrete time-domain Norton equivalent model of three-phase resistance can be obtained; For three-phase impedance, the equation is satisfied in dq coordinates: Writing the equation in matrix form: According to the equation, the discrete time-domain Norton equivalent model of three-phase impedance can be obtained; For the three-phase admittance, the equation is satisfied in dq coordinates: Writing the equation in matrix form: According to the equation, the discrete time-domain Norton equivalent model of three-phase admittance can be obtained; The above deduces the continuous time-domain state-space equations of three-phase resistance, three-phase impedance and three-phase admittance respectively. According to the time-domain state-space model of the aforementioned grid-type energy storage device and the resistance, impedance and admittance state-space models, the subsequent impedance modeling can be performed for any entire system without other complex components.

[0021] In S400 of this embodiment, as a preferred embodiment, a discrete time-domain Norton equivalent model of the component including a historical current term is obtained, including: According to the linearization of the continuous time domain state space equation at the steady-state point, the small signal model of the energy storage device and basic components is obtained, and the expression is as follows: Among them, x is a column vector consisting of component state variables, u dq and i dq are the voltage and current values ​​of the component port in dq coordinates, which are used as input variables and output variables respectively. A, B, C, and D are column vectors respectively. and i dq For x and u dq The Jacobian matrix is ​​obtained by partial derivative. Then discretization is performed, and trapezoidal integration is performed according to the continuous time domain small signal model of the component. After sorting, the expression is as follows: The second term on the right side of the expression is defined as the historical current term Δh(t). After sorting, the discrete time-domain Norton equivalent model including the historical current term is obtained, and the expression is: The above formula is a unified expression of the discrete time-domain Norton equivalent model of each component.

[0022] In S500 of this embodiment, as a preferred embodiment, Figure 3 As shown, the discrete time-domain Norton equivalent models of each component are aggregated to form a discrete time-domain Norton equivalent model of the subsystem port, including: According to the discrete time-domain Norton equivalent model formed by each non-resistance element of the subsystem, a subsystem equivalent model is integrated, and the expression is as follows: Δh tot (t) = A tot Δh tot (t-Dt)+B tot Δu dq,dyn (t-Dt) Among them, A tot and B tot are the A of the non-resistance components of the subsystem d and B d The block diagonal matrix, Δu dq,dyn is the Δu of the non-resistive elements of the subsystem dq The column vector formed by Using the node analysis method and the correlation matrix, the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current is obtained, and its expression is as follows: Among them, M nb 、M n_dyn and M np are the association matrices of node-branch, node-non-resistance branch and node-port, Δi dq,n and Δu dq,n are the subsystem node current and voltage column vectors, Δu dq,p and Δi dq,p are the column vectors of the subsystem port voltage and current, Δu dq,dyn is the voltage column vector of the non-resistance components of the subsystem, C tot C is the non-resistive element of the subsystem d The block diagonal matrix D tot is the D of all components of the subsystem d The block diagonal matrix formed; According to the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current, and the subsystem equivalent model, the subsystem internal voltage and current column vector is eliminated to obtain the subsystem port discrete time domain Norton equivalent model, whose mathematical expression is as follows: Among them, A D , B D , C D and D D It is a coefficient matrix that reflects the state variables of all components in the subsystem.

[0023] In S600 of this embodiment, as a preferred embodiment, the discrete time-domain Norton equivalent model of the port is z-transformed to obtain a discrete frequency-domain impedance model under dq coordinates, which is expressed by a second-order impedance matrix, including: According to the subsystem port discrete time domain Norton equivalent model, mathematical processing is performed to obtain an equivalent model with the port current as the input variable and the port voltage as the output variable. The processed expression is as follows: To express it intuitively, the expression is rewritten as follows: Among them, each coefficient matrix can be obtained by substituting the matrix calculation described above; According to the above expression, z-transform is performed, with the port current as input and the port voltage as output, to obtain the matrix expression of the discrete frequency domain impedance transfer function of the subsystem, as shown below: H(z)=C sys (zI-A sys ) -1 B sys +Dsys Wherein, H(z) is a two-dimensional matrix of the following form: The four parameters of the two-dimensional matrix can be solved separately, using H dd Taking the solution of (z) as an example, its zero-pole gain representation is as follows: Among them, the gain K zdd The size is: K zdd =D sys,dd Pole v j A sys The characteristic root of corresponds to the following result: det|zI-A sys |=0 Zero point w i A D The characteristic root of corresponds to the following result: det|zI-A D |=0 In S700 of this embodiment, as a preferred embodiment, obtaining the subsystem port continuous frequency domain impedance transfer function includes: The port discrete frequency domain impedance model is mapped from the z domain to the s domain using a bilinear transformation, and the mathematical expression of the bilinear transformation is: The port impedance transfer function matrix expression of the s-domain is: To solve Z dd (s) as an example, its zero-pole gain representation is as follows: According to the bilinear transformation process, the zero point, pole and gain of the s-domain impedance transfer function are respectively obtained, and the mathematical expressions are as follows: Among them, w i 、v j and K zdd are the zero, pole and gain of the impedance transfer function in the z domain, z i 、p j and K sdd They are the zero, pole and gain of the s-domain impedance transfer function, and z0 and s0 are 1 and 0 respectively.

[0024] For ease of understanding, the following will be Figure 2The examples shown are used as examples to illustrate the present invention, but should not be used to limit the protection scope of the present invention.

[0025] Table 1 shows the parameters of the grid-side components, and Table 2 shows the circuit structure and control loop parameters of the grid-type energy storage equipment: Table 1 Table 2 Then the whole system is initialized, including power flow calculation and assignment of internal state variables of each steady-state component. After the initialization is completed, the impedance modeling and analysis process is carried out, including building a continuous time domain state space model of the component, discretization processing, aggregation, z-transformation and bilinear transformation process, to obtain the port continuous frequency domain impedance transfer function of the subsystem, and draw the dq coordinate impedance characteristic curve.

[0026] like Figure 4 As shown, by comparing the theoretical analysis results of the present invention with the results obtained by the frequency scanning method, it can be verified that the present invention has high accuracy in the frequency range from a few hertz to thousands of hertz, and the results obtained by the present invention are continuous, which can more accurately describe the impedance characteristics than the scattered points obtained by the frequency scanning method. Table 3 shows the time comparison of the impedance characteristics obtained by the theoretical method provided by the present invention and the traditional frequency scanning method, which can verify that the present invention improves the efficiency of impedance modeling and characteristic analysis by a thousand times.

[0027] Table 3 Frequency sweep method The present invention analysis method Time(s) 720.21 0.49 It should be noted that the steps in the method provided by the present invention can be implemented by using corresponding modules, devices, units, etc. in the system. Those skilled in the art can refer to the technical solution of the method to realize the composition of the system, that is, the embodiments in the method can be understood as preferred examples for constructing the system, which will not be elaborated here.

[0028] An embodiment of the present invention provides a tool, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it can be used to execute any one of the methods in the above embodiments of the present invention.

[0029] The present invention is adaptable to grid-connected energy storage systems with different topologies and parameters. When the topology changes, only the association matrix and branch description need to be modified; when the parameters change, only the records of component parameters need to be modified.

[0030] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the embodiments disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not disclosed in the present application.

[0031] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A fast modeling method for small signal frequency domain impedance of grid-connected energy storage equipment, characterized by: The following steps are involved: Obtain the topology and parameters of the grid-connected system of the grid-connected energy storage device, perform steady-state power flow calculation based on the topology and parameters, and obtain the steady-state values ​​of voltage and current of each component as the balance point for subsequent linearization; Construct a time-domain state-space model of a grid-type energy storage device, which includes a device internal circuit structure parameter model and a control loop signal model; Construct time-domain state-space models of basic components of power systems; The time-domain state-space model of the grid-type energy storage device and the time-domain state-space model of the basic components of the power system are linearized to obtain a small signal model, and based on the small signal model, a discrete time-domain Norton equivalent model of the port is obtained; The port discrete time-domain Norton equivalent model is z-transformed to obtain the port discrete frequency-domain impedance model, and the port discrete frequency-domain impedance model is mapped from discrete domain to continuous domain to obtain the port continuous frequency-domain impedance model.

2. According to claim 1, the small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device grid-connected system is characterized in that: The topology and parameters of the grid-connected system of the grid-connected energy storage device are obtained, and steady-state power flow calculation is performed according to the topology and parameters to obtain the steady-state values ​​of voltage and current of each component as the balance point of subsequent linearization. This process is completed through the iteration of the Newton-Raphson method.

3. The small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device system according to claim 1 is characterized in that: The time-domain state-space model of the grid-type energy storage device and the time-domain state-space model of the basic components of the power system are linearized to obtain a small signal model, which is: Differential algebraic equations are established for the independent and coupled relationships between the internal circuit structure of the device and the control loop, and the differential terms of the differential algebraic equations are set to zero to solve the steady-state state variable values ​​for subsequent linearization initial values. The expression of the differential algebraic equation is: Among them, x, z and v are all the state variables, algebraic variables and input variables of the component respectively; According to the differential algebraic equation, differential linearization is performed to obtain the small signal model of the grid-type energy storage device and the basic components of the power system. The small signal model expression is: Among them, Δi dq and Δu dq They represent the current and voltage changes in the dq coordinates determined by the PLL, and A, B, C, and D are column vectors respectively. and i dq For x and u dq The Jacobian matrix obtained by taking partial derivatives.

4. According to the small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device system of claim 3, the process of obtaining the port discrete time domain Norton equivalent model based on the small signal model is: discretizing the small signal model to form a generalized discrete time domain Norton equivalent model, combining the topological structure and subsystem division of the power grid, eliminating some variables of the components in the subsystem, and aggregating to form a port discrete time domain Norton equivalent model, wherein, The small signal model is discretized to form a generalized discrete time-domain Norton equivalent model, which is: The small signal model is discretized, and trapezoidal integration is performed according to the continuous time domain small signal model of the component. After sorting, the expression is as follows: Will Defined as the historical current term Δh(t), after sorting, the discrete time domain Norton equivalent model including the historical current term is obtained, and the expression is: The above formula is a unified expression of the generalized discrete time-domain Norton equivalent model of each component.

5. The small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device system according to claim 4 is characterized in that: The above-mentioned topological structure of the power grid is combined with the subsystem division, some variables of the components in the subsystem are eliminated, and the discrete time domain Norton equivalent model of the port is aggregated, which is specifically: According to the generalized discrete time-domain Norton equivalent model of each non-resistance element of the subsystem, a subsystem equivalent model is integrated, and the expression is as follows: Δh tot (t)=A tot Δh tot (t-Dt)+B tot Δu dq,dyn (t-Dt) Among them, A tot and B tot are the A of the non-resistance components of the subsystem d and B d The block diagonal matrix, Δu dq,dyn is composed of the non-resistive elements of the subsystem Δu dq The column vector formed by Using the node analysis method and the correlation matrix, the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current is obtained, and its expression is as follows: Among them, M nb 、M n_dyn and M np are the association matrices of node-branch, node-non-resistance branch and node-port, Δi dq,n and Δu dq,n are the subsystem node current and voltage column vectors, Δu dq,p and Δi dq,p are the column vectors of the subsystem port voltage and current, Δu dq,dyn is the voltage column vector of the non-resistance components of the subsystem, C tot C is the non-resistive element of the subsystem d The block diagonal matrix D tot is the D of all components of the subsystem d The block diagonal matrix formed; According to the mathematical relationship between the subsystem port voltage and current and the internal component voltage and current, and the subsystem equivalent model, the subsystem internal voltage and current column vector is eliminated to obtain the discrete time domain Norton equivalent model of the subsystem port, and its mathematical expression is as follows: Among them, A D , B D , C D and D D It is a coefficient matrix that reflects the state variables of all components in the subsystem.

6. The small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device system according to claim 5 is characterized in that: The port discrete time-domain Norton equivalent model is subjected to z-change to obtain the port discrete frequency-domain impedance model, specifically: mathematical processing is performed on the subsystem port discrete time-domain Norton equivalent model to obtain an equivalent model with the port current as the input variable and the port voltage as the output variable. The processed expression is as follows: To express it intuitively, the expression is rewritten as follows: Among them, each coefficient matrix can be obtained by substituting the matrix calculation described above; According to the above expression, z-transform is performed, with the port current as input and the port voltage as output, to obtain the matrix expression of the discrete frequency domain impedance transfer function of the subsystem, as shown below: H(z)=C sys (zI-A sys ) -1 B sys +D sys Among them, C sys A represents the coefficient matrix of the subsystem port output variables. sys Represents the coefficient matrix of the subsystem internal state variables, B sys The coefficient matrix representing the input variables of the subsystem port, D sys represents the direct transfer matrix of the subsystem port, and H(z) is a two-dimensional matrix of the following form: Solve the four parameters of the two-dimensional matrix separately, H dd (z) Zero-pole gain is expressed as follows: Among them, w i 、v j and K zdd They are the zero, pole and gain of the discrete domain impedance transfer function, and the gain K zdd The size is: K zdd =D sys,dd Pole v j A sys The characteristic root of corresponds to the following result: det|zI-A sys |=0 Zero point w i A D The characteristic root of corresponds to the following result: det|zI-A D |=0。 7. The small signal frequency domain impedance rapid modeling method of the grid-connected energy storage device system according to claim 6 is characterized in that: The discrete frequency domain impedance model of the port is mapped from the discrete domain to the continuous domain to obtain the continuous frequency domain impedance model of the port, which is specifically: The port discrete frequency domain impedance model is mapped from the discrete domain to the continuous domain using bilinear transformation, and the mathematical expression of the bilinear transformation is: The port impedance transfer function matrix expression of the continuous domain is: To solve Z dd (s) as an example, its zero-pole gain representation is as follows: According to the bilinear transformation process, the zeros, poles and gains of the continuous domain impedance transfer function are respectively obtained, and the mathematical expressions are as follows: Among them, z i 、p j and K sdd are the zero, pole and gain of the continuous domain impedance transfer function, z0 and s0 are 1 and 0 respectively.

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