Optimized operation method and system for multi-network-construction type energy storage system

Abstract

The invention belongs to the technical field of distributed energy storage control, and discloses an optimized operation method and system for a multi-network-constructed energy storage system, and the method comprises the steps: carrying out the equivalence of the multi-network-constructed energy storage system, and obtaining an equivalent energy storage system; wherein the equivalent energy storage system comprises an isomorphic network-following converter, an equivalent impedance R and an ideal voltage source which are sequentially connected in series; based on the equivalent energy storage system, obtaining a small signal stability boundary condition by adopting a Routh criterion; and taking the minimum operation cost as an objective function, solving the objective function under operation constraints including small signal stability boundary conditions, and obtaining J and D of each network construction type converter at different moments, so that each network construction type converter operates under the corresponding J and D. The method is suitable for optimized operation configuration of an energy storage system comprising a plurality of network following-constructing converters, and can effectively promote advantage complementation of renewable energy sources and energy storage, thereby improving system stability and operation economy.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed energy storage control, and more specifically, relates to a method and system for optimizing operation of a multi-grid-type energy storage system. Background Art

[0002] As the proportion of renewable energy connected to the grid with grid-following converters increases, not only does it reduce the grid inertia, but it also brings challenges to frequency support and system stability. Energy storage systems that use grid-connected converters are an effective way to solve the above problems. Grid-connected converters have flexible and fast bidirectional energy transfer capabilities and can provide inertia and frequency support. In addition, grid-connected converters do not need to use a phase-locked loop to synchronize with the grid, avoiding the small signal stability problems associated with phase-locked loops. Therefore, energy storage systems containing multiple grid-connected and grid-connected converters play a key role in shaping the future power system landscape.

[0003] However, multiple grid-connected and grid-connected converters not only significantly increase the state dimension of the energy storage system, but also there is interaction between the grid-connected and grid-connected converters, making the multi-grid-connected and grid-connected energy storage system relatively complex. Therefore, it is urgent to study the instability mechanism of the energy storage system of multiple heterogeneous grid-connected and grid-connected converters affected by phase-locked loop coupling in weak power grids. In the existing stability analysis research of multi-grid-connected and grid-connected energy storage systems, in order to simplify the model, the energy storage inertia parameters and droop parameters that affect the small signal stability of the energy storage system are generally directly taken as fixed quantities, which will cause the energy storage system to become unstable or collapse, reducing the safety and stability of the power system. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a method and system for optimizing the operation of a multi-grid-type energy storage system, the purpose of which is to improve the safety and stability of the operation of the multi-grid-type energy storage system.

[0005] To achieve the above object, according to a first aspect of the present invention, a method for optimizing operation of a multi-grid-type energy storage system is provided, wherein the multi-grid-type energy storage system comprises M grid-type converters and N heterogeneous grid-type converters, where M≥1 and N≥1; and comprises:

[0006] The multi-grid-type energy storage system is equivalent to obtain an equivalent energy storage system; wherein the equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R and an ideal voltage source connected in series in sequence; the control parameters and operating parameters of the homogeneous grid-type converter correspond to the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid-type converters; the voltage of the ideal voltage source is the same as the rated voltage of each of the grid-type converters; the equivalent impedance Δδ(J,D) is the grid strength disturbance caused by the synchronous impedance of M grid-connected converters. J and D correspond to the inertia parameter and droop parameter of each grid-connected converter. g is the grid-connected admittance of the equivalent energy storage system without considering inertia and droop;

[0007] Based on the equivalent energy storage system, the Routh criterion is used to obtain the small signal stability boundary conditions of the multi-grid-structured energy storage system;

[0008] Taking minimizing the operating cost as the objective function, under the operating constraints including the small signal stability boundary conditions, the objective function is optimized and solved to obtain the inertia parameter J and droop parameter D of each grid-type converter at different times, so that each grid-type converter operates under corresponding J and D.

[0009] Furthermore, the multiple grid-to-grid type energy storage systems are equivalent to obtain an equivalent energy storage system, including:

[0010] Each grid-type converter is equivalent to an ideal voltage source connected in series with an inductor, wherein the inductor includes an inductor with a fixed resistance and a variable inductor characterized by an inertia parameter J and a droop parameter D of each grid-type converter; the voltage of the ideal voltage source is the same as the rated voltage of each grid-type converter;

[0011] The N heterogeneous grid-type converters are converted into N homogeneous grid-type converters; wherein the control parameters and operating parameters of each homogeneous grid-type converter correspond to the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid-type converters respectively;

[0012] The energy storage system composed of the equivalent M grid-type converters and the N isomorphic grid-type converters is decoupled into N independent equivalent subsystems. The grid-connected reactance of the N independent equivalent subsystems and the reactance matrix Z of the multi-grid-type energy storage system are Lred The N eigenvalues ​​σ i Consistent, the order of magnitude is σ1≥σ2≥,...,≥σ N ≥0, i=1,...,N;

[0013] The equivalent subsystem with the maximum grid-connected reactance σ1 is used as the equivalent energy storage system; wherein σ1=R.

[0014] Furthermore, the equivalent impedance Z of the inductor is GFM for:

[0015] Z GFM =Z mdq α(s)+Z mδ (J,D)α(s)

[0016]

[0017] Among them, Z mdq The impedance of the fixed-resistance inductor, Z mδ (J, D) is the impedance of the variable inductor; U d0 ,I d0 , Y0(s), θ0, ω0 represent the d-axis voltage, d-axis current, dq coordinate admittance, terminal voltage steady-state angle, and rated angular velocity of each grid-type converter respectively; s represents a complex frequency domain variable.

[0018] Furthermore, the grid strength disturbance Δδ(J,D) caused by the synchronous impedance of M grid-connected converters is:

[0019]

[0020] Y δ (J,D)=1 / (Z mdq +Z mδ (J,D))-1 / Z mdq

[0021] in, is the matrix Q red The block matrix, Q red is the Krona-reduced reactance matrix of N+M dimensions; S BM =diag{S BMi},S BMi is the capacity ratio of the rated capacity of the i-th grid-connected converter to the unit calculation base capacity, diag represents a diagonal matrix; v1 and u1 are the reactance matrix Z Lred The normalized left eigenvector and right eigenvector corresponding to the maximum eigenvalue of M represents the M-order identity matrix; the matrix represents the conjugate transpose of Q.

[0022] Furthermore, the small signal stability boundary condition of the multi-grid-structured energy storage system is:

[0023]

[0024] Alternatively, the small signal stability boundary condition of the multi-grid-structured energy storage system is:

[0025]

[0026] Among them, U i0 、p i are the steady-state terminal voltage and participation factor of the ith heterogeneous grid-type converter, respectively; ω0 represents the rated angular velocity of each grid-type converter; For The steady-state weighted active power under For The steady-state weighted reactive power under Three-phase synchronous phase-locked loop PI constant k Lp,i and k Li,i Used to characterize the control parameters of the i-th heterogeneous grid-connected converter, and Used to characterize the control parameters of each isomorphic grid-type converter; P i0 is the steady-state active power of the i-th heterogeneous grid-type converter.

[0027] Furthermore, the operation constraints also include small signal constraints of N heterogeneous grid-type converters under different operating conditions:

[0028]

[0029] Wherein, σ1 is the reactance matrix Z of the multi-grid-structured energy storage system Lred The maximum eigenvalue of , and σ1=R.

[0030] Furthermore, the operation constraints also include frequency stability constraints:

[0031]

[0032] J min ≤J t ≤J max

[0033] J max ≤D t ≤D max

[0034] Among them, f0, RoCoF max are respectively the rated frequency, the maximum steady-state frequency, and the maximum frequency change rate of the multi-grid-type energy storage system; ΔP t is the disturbance power at time t, S BM,k is the capacitor of energy storage device k, which corresponds to the kth grid-type converter; J t and D t are the inertia parameters and droop parameters of each grid-connected converter at time t, J min , J max and D max are the minimum allowable inertia, maximum allowable inertia and maximum allowable droop parameters of each grid-connected converter respectively.

[0035] Furthermore, the objective function is:

[0036]

[0037] in, is the renewable energy curtailment penalty for renewable energy i at time t, where renewable energy i corresponds to the i-th heterogeneous grid-connected converter; is the power loss of energy storage device k at time t, and energy storage device k corresponds to the kth grid-connected converter.

[0038] According to a second aspect of the present invention, there is provided a multi-grid-type energy storage system optimization operation system, comprising a computer-readable storage medium and a processor;

[0039] The computer-readable storage medium is used to store executable instructions;

[0040] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the multi-grid-type grid-connected energy storage system optimization operation method described in any one of the first aspects.

[0041] According to a third aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, the method for optimizing operation of a multi-grid-type energy storage system as described in any one of the first aspects is implemented.

[0042] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0043] (1) The multi-grid-type energy storage system optimization operation method of the present invention, through analysis, equates the high-order complex multi-grid-type energy storage system to a low-order simple energy storage system, and the equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R and an ideal voltage source connected in series in sequence; since the control parameters and operating parameters of the homogeneous grid-type converter are obtained by weighted calculation of the different control parameters and operating parameters of the original N heterogeneous grid-type converters, it can reflect the influence of the control parameters and operating parameters of the original N heterogeneous grid-type converters on the stability of the multi-grid-type energy storage system; since the Δδ(J,D) in the equivalent impedance R includes The inertia parameter J and droop parameter D that affect the small signal stability of the multi-grid-type energy storage system are included. Based on the equivalent low-order simple energy storage system, the Routh criterion is used to obtain the small signal stability boundary conditions of the multi-grid-type energy storage system with the inertia parameter J and droop parameter D of each grid-type converter as decision variables. The small signal stability boundary conditions are used as one of the operating constraints to solve the optimization problem with minimizing the operating cost as the objective function. The inertia parameter J and droop parameter D of each grid-type converter can be optimized in real time. By reasonably allocating inertia and droop control, the stability and safety of multiple grid-type energy storage systems under small disturbances can be maintained.

[0044] (2) Furthermore, the present invention provides a specific method for equilibrating multiple grid-type energy storage systems. After equilibrating each grid-type converter, the influence of each grid-type converter on the grid-type converter can be concretized as an impedance voltage source model, which is convenient for clarifying the interaction between the grid and the grid-type converter; at the same time, N heterogeneous grid-type converters are equivalent to N homogeneous grid-type converters, and the control parameters and operating parameters of the equivalent homogeneous grid-type converters are obtained by controlling the different control parameters of the original N heterogeneous grid-type converters. The control parameters and operating parameters are weightedly calculated, which can reflect the influence of the control parameters and operating parameters of the original N heterogeneous grid-type converters on the stability of the energy storage system, and effectively simplify the stable operation analysis process of the energy storage system. In this way, based on the equivalent M grid-type converters and N homogeneous grid-type converters, the multi-grid-type energy storage system can be decoupled into N independent equivalent subsystems. If any of the equivalent subsystems is unstable, it means that the original multi-grid-type energy storage system before the equivalent is also unstable. In addition, σ i The larger it is, the greater the possibility of system instability. Therefore, the equivalent subsystem with the largest grid-connected reactance (σ1) among N independent equivalent subsystems is selected as the equivalent energy storage system. The high-order and complex multi-grid-structured energy storage system can be reduced to a low-order simple subsystem.

[0045] (3) Furthermore, the small signal stability boundary condition of the multi-grid-type energy storage system of the present invention reveals that the grid-type converter changes the equivalent impedance connected to the grid-type converter. To affect the stability of the grid-following converter, the inertia parameter J and the droop parameter D will affect the stability of the grid-following converter.

[0046] (4) Furthermore, the operation constraints also include small signal stability constraints of N heterogeneous grid-connected converters under different operating conditions. In this constraint, the weighted power and It can represent different operating conditions of different grid-connected converters. It quantifies the stability boundaries of multiple grid-connected converters under different operating conditions through weighted power and maximum grid-connected reactance σ1, enriching the connotation and application scenarios of small signal stability criteria.

[0047] (5) As a preference, compared with the existing frequency stability constraint that regards the frequency regulation parameters of the energy storage system as dispatching variables, which mainly focuses on the frequency response characteristics, the present invention introduces the inertia parameters and droop parameters of each grid-connected converter at each moment into the designed frequency stability constraint. By adjusting the inertia parameters and droop control parameters in real time, the power system can maintain a nearly constant frequency, which helps to ensure frequency synchronization between various devices and loads in the system and improve the operating efficiency of the system.

[0048] (6) As a preferred embodiment, the present invention comprehensively considers the penalty costs for abandoning wind and solar power of renewable energy, and the power loss costs of energy storage charging and discharging, which are the operating costs with the largest proportion and the most significant impact. By obtaining the minimum value of the objective function, the purpose of minimizing the operating costs is achieved, thereby optimizing the economic efficiency of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of a method for optimizing operation of a multi-grid-type energy storage system in an embodiment of the present invention.

[0050] Figure 2 Schematic diagram of an equivalent voltage source model of each grid-connected converter in an embodiment of the present invention.

[0051] Figure 3 It is an equivalent model of the decoupled equivalent subsystem in the embodiment of the present invention.

[0052] Figure 4 FIG. 4 is a schematic diagram of the topological structure of the IEEE 39 test network used in the embodiment of the present invention.

[0053] Figure 5 1 is the time domain response of multiple grid-following converters under different operating conditions in the embodiment of the present invention.

[0054] Figure 6 Schematic diagram of the effect of inertia and damping on grid strength in an embodiment of the present invention.

[0055] Figure 7 1 is the time domain response of multiple grid-connected and grid-forming converters under different inertia and droop parameter conditions in an embodiment of the present invention.

[0056] Figure 8 These are the results of different power dispatching models in the embodiments of the present invention. (a)-(d) respectively represent the active power, steady-state frequency, frequency change rate and damping ratio of different power dispatching models at different times. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] In the present invention, the terms "first", "second", etc. in the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0059] Example 1

[0060] like Figure 1 As shown, an embodiment of the present invention provides a method for optimizing the operation of a multi-grid-type energy storage system, wherein the multi-grid-type energy storage system includes M interconnected grid-type converters and N heterogeneous grid-type converters, M≥1, N≥1; the method for optimizing the operation of the multi-grid-type energy storage system includes:

[0061] Equivalent multiple grid-type energy storage systems to obtain an equivalent energy storage system; wherein the equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R and an ideal voltage source connected in series in sequence; the control parameters and operating parameters of the homogeneous grid-type converter correspond to the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of N heterogeneous grid-type converters; the voltage of the ideal voltage source is the same as the rated voltage of each grid-type converter; the equivalent impedance Δδ(J,D) is the grid strength disturbance caused by the synchronous impedance of M grid-connected converters. J and D correspond to the inertia parameter and droop parameter of each grid-connected converter. g is the grid-connected admittance of the equivalent energy storage system without considering inertia and droop;

[0062] Based on the equivalent energy storage system, the Routh criterion is used to obtain the small signal stability boundary conditions of the multi-grid-structured energy storage system.

[0063] An optimal operation model of a multi-grid-type energy storage system is constructed. The optimal operation model takes minimizing the operating cost as the objective function. Under the operating constraints including the small signal stability boundary conditions, the objective function is optimized and solved to obtain the inertia parameter J and droop parameter D of each grid-type converter at different times, so that each grid-type converter can operate under the corresponding inertia parameter J and droop parameter D.

[0064] Preferably, multiple grid-type energy storage systems are equivalent to obtain an equivalent energy storage system, including: each grid-type converter is equivalent to an ideal voltage source connected in series with an inductor; wherein the voltage of the ideal voltage source is the same as the rated voltage of each grid-type converter, and the inductor includes an inductor with a fixed resistance and a variable inductor characterized by the inertia parameter J and the droop parameter D of the current grid-type converter; in an embodiment of the present invention, the rated voltage, inertia parameter J and droop parameter D of the M grid-type converters are the same;

[0065] The control parameters of the N grid-type converters are weighted and used as the control parameters of each grid-type converter, and the operating parameters of the N grid-type converters are weighted and used as the operating parameters of each grid-type converter, so that the N heterogeneous grid-type converters are transformed into N homogeneous grid-type converters;

[0066] The energy storage system composed of M equivalent grid-type converters and N isomorphic grid-type converters is decoupled into N independent equivalent subsystems, and the equivalent subsystem with the largest grid-connected reactance among the N independent equivalent subsystems is taken as the most critical subsystem, and the most critical subsystem is used as the equivalent multi-grid-type energy storage system.

[0067] The multi-grid-type energy storage system optimization operation method of the present invention can be specific to the influence of the grid-type converter on the grid-type converter as an impedance voltage source model by making each grid-type converter equivalent, so as to clarify the interaction between the grid-type converter and the grid-type converter; at the same time, N heterogeneous grid-type converters are equivalent to N homogeneous grid-type converters, which effectively simplifies the stable operation analysis process of the energy storage system, and the control parameters of the equivalent homogeneous grid-type converter are obtained by weighted calculation of the different control parameters of the original N heterogeneous grid-type converters, and the operating parameters of the equivalent homogeneous grid-type converter are obtained by weighted calculation of the different operating parameters of the original N heterogeneous grid-type converters, which can reflect the influence of the control parameters and operating parameters of the original N heterogeneous grid-type converters on the stability of the energy storage system; in this way, based on the equivalent M grid-type converters and N homogeneous grid-type converters, the energy storage system can be decoupled into N There are N independent equivalent subsystems. Since the larger the grid-connected reactance is among the N independent equivalent subsystems, the greater the possibility of instability of the energy storage system. Therefore, the equivalent subsystem with the largest grid-connected reactance among the N independent equivalent subsystems is used as the equivalent multi-grid-type energy storage system. The high-order complex multi-grid-type energy storage system can be reduced to a low-order simple subsystem. Based on the low-order simple subsystem, the Routh criterion can be used to obtain the small signal stability boundary conditions of the multi-grid-type energy storage system with the inertia parameter J and droop parameter D of each grid-type converter as decision variables. The small signal stability boundary conditions are used as one of the operating constraints to solve the optimization problem with minimizing the operating cost as the objective function. The inertia parameter J and droop parameter D of each grid-type converter can be optimized in real time. Each grid-type converter operates under the corresponding inertia parameter J and droop parameter D, which can improve the operating stability and safety of the multi-grid-type energy storage system.

[0068] In the embodiment of the present invention, Figure 2 As shown, in the equivalent process, the inductor connected in series with the ideal voltage source of each grid-type converter includes an inductor with a fixed resistance and a variable inductor characterized by the inertia parameter J and droop parameter D of the current grid-type converter. Among them, the equivalent impedance Z of the inductor connected in series with the ideal voltage source GFM for:

[0069] Z GFM ≈Z mdq α(s)+Z mδ (J,D)α(s)

[0070]

[0071] Among them, Z mdq The impedance of an inductor with a fixed resistance, Z mδ (J, D) represents the impedance of the variable inductor characterized by inertia parameters and droop parameters; U d0 ,I d0 They represent the d-axis voltage and current of the current grid-connected converter respectively; L F , C F They represent the filter inductance and filter capacitance of the current grid-connected converter respectively; f VF (s) = 1 / (T VF s+1) represents the filter of the voltage feedforward signal in the current grid-connected converter, T VF Represents the filter time constant of the filter, s represents the complex frequency domain variable; PI CC (s) = K CCP +K CCI / s、PI VC (s) = K VCP +K VCI / s represent the PI controller transfer functions of the current loop and voltage loop of the current grid-connected converter, respectively, K CCP , K CCI Respectively represent the proportional and integral gains of the current loop PI controller, K VCP , K VCI They respectively represent the proportional and integral gains of the PI controller of the voltage loop; θ0 is the steady-state angle of the terminal voltage of the current grid-type converter, ω0 represents the rated angular velocity of the current grid-type converter, and the rated angular velocity of each grid-type converter is the same; Y0(s) represents the dq coordinate admittance of the current grid-type converter.

[0072] In the embodiment of the present invention, through theoretical analysis, each grid-forming converter is equivalent to an ideal voltage source connected in series with an internal inductor with a fixed resistance and a variable inductor characterized by inertia parameters and droop parameters, and the influence of the grid-forming converter on the grid-following converter is concretized as an impedance voltage source model, which facilitates the subsequent elaboration of the interaction between the grid-forming and grid-following converters, thereby greatly simplifying the analysis of the influence of the grid-forming converter on the small signal stability of the grid-following converter.

[0073] In order to further simplify the model of the grid-connected converter, in an embodiment of the present invention, N heterogeneous grid-connected converters are equivalent to N homogeneous grid-connected converters.

[0074] Based on the energy storage system composed of the equivalent M grid-connected converters and N isomorphic grid-connected converters, the energy storage system can be decoupled into N independent equivalent subsystems. Each equivalent subsystem has a different equivalent grid-connected reactance and corresponds to the reactance matrix Z of the energy storage system. Lred The characteristic value (σ i , i=1,...,N), the order of size is σ1≥σ2≥,...,≥σ N ≥0. If any of the equivalent subsystems is unstable, it means that the original energy storage system before the equivalent is also unstable. In addition, σ i The larger it is, the greater the possibility of system instability. Therefore, the subsystem with the largest grid-connected reactance (σ1) among the N independent equivalent subsystems is selected as the most critical subsystem;

[0075] In the embodiment of the present invention, the state matrix of the most critical subsystem can be expressed as:

[0076]

[0077] in,

[0078]

[0079] Where U x,i0 , U y,i0 , I x,i0 and I y,i0 is the operating parameter of the ith grid-type converter, and the subtable represents the steady-state terminal voltage and output current on the global xy coordinates. ω0 is the rated angular velocity of each grid-type converter, k Lp,i and k Li,i are the control parameters of the i-th grid-type converter, and represent the PI constants of the three-phase synchronous phase-locked loop of the i-th grid-type converter respectively; i is the participation factor, p i =u i1 v i1 (i=1,...,N),u i1 and v i1 are respectively the reactance matrix Z of the energy storage system Lred The i-th element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the maximum eigenvalue; U i0 represents the steady-state terminal voltage of the i-th grid-connected converter; I2 represents the second-order unit matrix, and σ1 is the largest grid-connected reactance among the N independent equivalent subsystems.

[0080] It can also be seen from the state matrix that by establishing an equivalent system consisting of N isomorphic grid-type converters, the analysis process can be effectively simplified, and the control parameters and operating parameters of the equivalent isomorphic grid-type converter are obtained by changing the different control parameters (k Lp,i and k Li,i ) and operating parameters (U x,i0 , U y,i0 , I x,i0 and I y,i0 ) is obtained by weighted calculation, which can reflect the influence of the control parameters and operating parameters of the original heterogeneous N grid-type converters on the stability of the energy storage system.

[0081] like Figure 3 As shown in the figure, it is a schematic diagram of the equivalent model of the most critical subsystem, which is the equivalent multi-grid-type energy storage system, including a series of isomorphic grid-type converters, equivalent impedance and an ideal voltage source; the voltage of the ideal voltage source is equal to the equivalent ideal voltage source voltage of each grid-type converter, and the equivalent impedance The equivalent admittance of each equivalent subsystem consists of two parts: one is the grid-connected admittance λ of the most critical subsystem without considering inertia and droop. g , and the other part is the grid strength disturbance Δδ(J,D) caused by the synchronous impedance of each grid-type converter.

[0082] Based on the effective multi-grid-type energy storage system, the Routh criterion is used to obtain the stable boundary conditions of N grid-type converters under different operating conditions and the small signal stable boundary conditions of the multi-grid-type energy storage system. Among them, the stable boundary conditions of N grid-type converters under different operating conditions can be used as the small signal stability criterion of N grid-type converters under different operating conditions; the small signal stable boundary conditions of the multi-grid-type energy storage system can be used as the small signal stability criterion of the multi-grid-type energy storage system. In the embodiment of the present invention, the corresponding criterion is used as one of the constraint conditions of the system optimization operation model.

[0083] Preferably, the stable boundary conditions of N heterogeneous grid-type converters under different operating conditions are:

[0084]

[0085] Where σ1 is the largest grid-connected reactance of N independent equivalent subsystems (considering inertia and droop), U i0 , k Lp,i and k Li,i 、p i are the steady-state terminal voltage, three-phase synchronous phase-locked loop PI constant and participation factor of the i-th grid-following converter, For The steady-state weighted active power under For The steady-state weighted reactive power under is the control parameter k of N grid-following converters Li,i (i=1,...,N) The control parameters of each isomorphic grid-type converter obtained after weighting, is the control parameter k of N grid-following converters Lp,i (i=1,...,N) The control parameters of each isomorphic grid-type converter obtained after weighting, and is the PI constant of the three-phase synchronous phase-locked loop of each isomorphic grid-type converter, which is used to characterize the control parameters of each isomorphic grid-type converter. Specifically, and is defined as:

[0086]

[0087] Among them, θ i0 ,θ j0 are the terminal voltage steady-state angles of the i-th and j-th grid-following converters respectively; k Lp,i and k Li,i They represent the PI parameters of the three-phase synchronous phase-locked loop of the i-th grid-following converter; U j0 , P j0 and Q j0 are the steady-state terminal voltage, active power and reactive power of the jth grid-following converter respectively; the participation factor p i =u i1 v i1 (i=1,...,N), p j =u j1 v j1 (i=1,...,N), where u i1 and v i1 are respectively the reactance matrix Z of the energy storage system Lred The i-th element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the maximum eigenvalue, u j1 and v j1 are respectively the reactance matrix Z of the energy storage system Lred The jth element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the maximum eigenvalue; is an intermediate variable.

[0088] In the embodiment of the present invention, the weighted power is defined and It can represent different operating conditions of different grid-connected converters, and quantify the stability boundaries of multiple grid-connected converters under different operating conditions by weighted power and the grid-connected reactance of the most critical subsystem (i.e., σ1), enriching the connotation and application scenarios of small signal stability criteria.

[0089] Preferably, the small signal stability boundary condition of the multi-grid-type energy storage system is:

[0090]

[0091] Among them, λ g is the grid-connected admittance of the most critical subsystem without considering inertia and droop, Δδ(J,D) is the grid strength disturbance caused by the synchronous impedance of each grid-type converter, and is defined as follows:

[0092]

[0093] in, is the matrix Q red The block matrix, Q red is the Krona-reduced reactance matrix of N+M dimensions; S BM =diag{S BMi},S BMi is the capacity ratio of the rated capacity of the i-th grid-connected converter to the unit calculation base capacity, diag represents a diagonal matrix; I M represents an M-order unit matrix. In the embodiment of the present invention, the matrix represents the conjugate transpose of Q. Y δ (J,D) and residual admittance Y δ (s) indicates that the relationship between them is:

[0094] Y δ (s)=Y δ (J,D)γ(s)

[0095] γ(s)=α(s) -1

[0096] Y δ (J,D)=1 / (Z mdq +Z mδ (J,D))-1 / Z mdq

[0097] Due to the steady-state angle difference (θ i0 -θ j0 ) is usually small, and the embodiment of the present invention focuses on the active power of the grid-type converter, so the small signal stability boundary condition of the above multi-grid-type energy storage system can be rewritten as:

[0098]

[0099] Among them, P i0 is the steady-state active power of the i-th heterogeneous grid-type converter.

[0100] The small signal stability boundary condition reveals that the grid-type converter changes the equivalent impedance connected to the grid-type converter. The value of Δδ(J,D) is less than zero. As the parameters J and D increase, Δδ(J,D) will increase, which indicates that the grid-connected admittance of the equivalent grid-connected converter (the isomorphic grid-connected converter) will increase, and J and D will affect the stability of the grid-connected converter.

[0101] Specifically, taking minimizing the operating cost as the objective function, preferably, the objective function of the multi-grid-type grid-connected energy storage system optimization operation model in the embodiment of the present invention is:

[0102]

[0103] Among them, t is the time index, ranging from 1 to T; i is the renewable energy index, ranging from 1 to N; k is the energy storage index, ranging from 1 to M; is the penalty for renewable energy curtailment of renewable energy i at time t, is the power loss of energy storage device k at time t. Energy storage device k corresponds to grid-connected converter k, and renewable energy source i corresponds to grid-connected converter i.

[0104] and The definition is as follows:

[0105]

[0106] Among them, rc is the penalty coefficient for abandoning solar and wind power of renewable energy; They represent the predicted power and planned power of renewable energy i at time t, and are the discharge loss and charging loss of energy storage device k at time t respectively; and are the discharge power and charging power of energy storage device k at time t respectively; η D,k and η C,k are the discharge efficiency and charging efficiency of energy storage device k respectively.

[0107] In the embodiment of the present invention, the penalty costs for abandoning wind and solar power of renewable energy and the power loss costs of energy storage charging and discharging are comprehensively considered. These are the operating costs with the largest proportion and the most significant impact. By taking the minimum value of the objective function, the purpose of minimizing the operating costs is achieved, thereby optimizing the economy of the system operation.

[0108] Taking the above-constructed small signal stability boundary condition as one of the operation constraints, the small signal stability constraint condition is:

[0109]

[0110] J min ≤J t ≤J max

[0111] J max ≤D t ≤D max

[0112] in, and is the planned power generation of the ith grid-connected converter at time t; J t and D t are the inertia parameter and droop parameter of the current grid-connected converter at time t, respectively, and are decision variables; J min , J max and D max are the minimum allowable inertia, maximum allowable inertia and maximum allowable droop parameters of the current grid-connected converter; Δδ(J t ,D t ) represents the grid strength disturbance caused by the synchronous impedance of each grid-type converter at time t.

[0113] In an embodiment of the present invention, based on the small signal stability constraints designed for the N decoupled subsystems, the energy storage inertia parameters and droop parameters that affect the stable operation of the energy storage system are used as optimization variables. The inertia parameters and droop parameters of each grid-type converter at each moment can be obtained by optimizing and solving the objective function. The system can achieve stable operation under the corresponding optimization parameters.

[0114] Preferably, the stability boundary conditions of the N grid-connected converters constructed above under different operating conditions are used as one of the operating constraints.

[0115] Preferably, the operation constraints of the multi-grid-grid energy storage system optimization operation model in the present invention also include frequency stability constraints, which can be expressed as:

[0116]

[0117] J min ≤J t ≤J max

[0118] J max ≤D t ≤D max

[0119] Where f0 is the rated frequency of the multi-grid-type energy storage system, is the maximum steady-state frequency of the multi-grid-type energy storage system, RoCoF max is the maximum frequency change rate of the multi-grid-type energy storage system; S BM,k is the capacitor of the energy storage device k; ΔP t is the disturbance power at time t, which is usually equal to the output power of the energy storage system at time t Related.

[0120] Compared with the existing frequency stability constraints that regard the frequency regulation parameters of the energy storage system as dispatching variables, which mainly focus on the frequency response characteristics, in the embodiments of the present invention, the inertia parameters and droop parameters of each grid-connected converter at each moment are introduced into the designed frequency stability constraints. By adjusting the inertia parameters and droop control parameters in real time, the power system can maintain a nearly constant frequency, which helps to ensure frequency synchronization between various devices and loads in the system and improve the operating efficiency of the system.

[0121] In the embodiment of the present invention, the operation constraints also include power balance constraints, renewable energy constraints, energy storage constraints and energy storage backup capacity constraints.

[0122] The power balance constraint is:

[0123]

[0124] in, is the output power of the energy storage system at time t, and are the discharge power and charging power of energy storage device k at time t respectively.

[0125] The renewable energy constraint is:

[0126]

[0127] in, The planned power generation of the i-th grid-connected converter cannot be greater than the predicted power generation

[0128] The energy storage constraint is:

[0129]

[0130] in, represents the remaining energy of energy storage device k at time t; Δt is the planned interval time; and is the minimum and maximum permissible residual energy of the energy storage device k; S BM,k is the capacitor of the energy storage device k; is the state of energy storage device k at time t, It means that the energy storage device k is in the charging state at time t. Indicates the discharge status; and are the discharge power and charging power of energy storage device k at time t, η D,k and η C,k are the discharge efficiency and charging efficiency of energy storage device k respectively.

[0131] The energy storage reserve capacity constraint is:

[0132]

[0133] in, It is the energy storage reserve power used to provide frequency support.

[0134] In the embodiment of the present invention, on the basis of considering the basic constraints of the energy storage power system (power balance constraints, renewable energy constraints, energy storage constraints and energy storage backup capacity constraints), through the designed small signal stability constraints and frequency stability constraints, the system optimal operation plan can take into account the system safety and stability and frequency fluctuation restrictions while pursuing the lowest operating cost, improve the power quality, improve the energy storage utilization rate, and realize the economic operation of the power grid.

[0135] The method of the present invention can improve the safety and stability of the power system: by reasonably allocating inertia and droop control, the stability of the power system containing multiple grid-following and grid-forming converters can be maintained under small disturbances, which helps prevent the system from becoming unstable or collapsing and improves the safety and reliability of the system.

[0136] The method of the present invention can achieve frequency control optimization: by adjusting the inertia parameters and droop control parameters in real time, the power system can maintain a nearly constant frequency, which helps to ensure frequency synchronization between various devices and loads in the system and improve the operating efficiency of the system.

[0137] The method of the present invention can reduce the operating cost of the energy storage system: by optimizing the operating methods of multiple grid-following and grid-forming converters, the system can reduce the power generation cost as much as possible while meeting the stability requirements, which helps to reduce the consumption of energy resources and improve the economic benefits of the power system.

[0138] The method of the present invention can achieve energy management optimization: by optimizing the operation of the power grid, various types of renewable energy can be managed and utilized more effectively, and the output power level of renewable resources and energy storage systems can be improved, which helps to promote the development of sustainable energy and reduce dependence on traditional energy.

[0139] In general, the present invention provides a theoretical basis and solution for the operation optimization problem of a multi-grid-type converter power system, which is of great significance for improving the small signal stability and operation economy of a multi-grid-type converter power system.

[0140] Below Figure 4 The multi-grid-type energy storage system shown in the figure is used as an example to verify the effectiveness of the stability boundary of the method proposed in the embodiment of the present invention under different operating conditions and different inertia-droop parameters. In this system, nine wind power plants are connected to the busbars 1-3, 5, 7-11 through the grid-type converter, and there are two energy storage systems connected to the grid-type converter at the busbars 4 and 6. Figure 4 The other numbers in the figure represent the busbars. The control parameters of the grid-following and grid-forming converters are detailed in Table 1-2. In addition, the capacities of the energy storage systems are 0.8 pu and 1.2 pu respectively. The time domain electromagnetic simulation of the system is carried out in MATLAB / Simulink.

[0141] Table 1 Parameters of grid-type converter

[0142]

[0143] Table 2 Parameters of grid-connected converter

[0144]

[0145] First, in order to verify the effectiveness of the method proposed in the embodiment of the present invention in analyzing the stability of multiple grid-connected converters under different operating conditions, the energy storage system connected to the grid through the grid-connected converter is not connected to the system. The value of the grid-connected admittance of the most critical subsystem without considering inertia and droop can be calculated as: g =2.8953. Table 3 lists three different operating conditions.

[0146] Table 3 Three scenarios of multiple grid-type converters under different operating conditions

[0147]

[0148] When all grid-connected converters have the same phase-locked loop parameters (8, 9500), the comparison of the system dominant poles evaluated by the full-order model (the model without decoupling equivalence) and the method of the present invention in three cases is shown in Table 4. Table 4 compares the system dominant poles in three scenarios. The results show that under all three operating conditions, the relative error between the dominant poles obtained by the full-order model and the method of the present invention is negligible. This proves the effectiveness of the decoupled model proposed in the present invention in evaluating the small signal stability of the entire system under different operating conditions.

[0149] The time domain electromagnetic simulation results under these three working conditions are shown in Figure 5 In scenario 1, divergent oscillations occurred, indicating that the system was unstable. In contrast, scenario 3 showed convergent oscillations, indicating that the system was stable. These time domain simulation results are consistent with the modal analysis results in Table 4, further verifying the effectiveness of this method.

[0150] When the phase-locked loop parameters of the grid-type converter are different, as shown in Table 5, modal analysis can be performed based on the full-order model and the simplified model (decoupled model) proposed by the present invention. Table 6 lists the dominant poles of the system under three working conditions. Lp / k Li The real part of the dominant pole is reduced compared with the dominant pole in Table 4, indicating that the system stability is improved. The modal analysis results are consistent with the proposed method. In addition, under all three operating conditions, the relative error between the dominant poles obtained by the full-order model and the dominant poles obtained by the proposed method is kept below 1%, which proves the effectiveness of the proposed method in multiple grid-following converters with different phase-locked loop parameters.

[0151] Table 4 The dominant poles obtained in three cases

[0152]

[0153] Table 5 Control parameters of multiple grid-following converter phase-locked loops

[0154]

[0155] Table 6 The dominant poles obtained in three different phase-locked loop situations

[0156]

[0157] Then, the effectiveness of this method in analyzing the stability of multiple grid-connected and grid-forming energy storage systems is verified under different inertia and droop parameters. In this case, the quantitative analysis of the proposed grid-forming converter inertia parameters and droop parameters on the stability of the grid-connected converter is verified. When the influence of the inertia parameters and droop parameters of the grid-forming converter on the grid strength is ignored, λ g The value of can be calculated as: g =3.5539. Compared with multiple grid-following converters, the grid strength is improved. According to the above grid parameters and this method, the influence of inertia and droop parameters on grid strength can be obtained as follows: Figure 6 As shown in Figure 2, as the inertia parameter and droop parameter of the grid-type converter increase, the degree of grid strength weakening also decreases. This shows that when the inertia parameter and droop parameter are large, the grid-type converter can be approximated as a series impedance Z GFMvoltage source.

[0158] Table 7 lists the dominant poles of the entire system under different inertia and droop parameters in case 1 and the dominant poles obtained by this method. From the results in the table, it can be seen that this method effectively approximates the dominant poles of the entire system. Figure 7 The corresponding time-domain electromagnetic simulation results are shown. When the inertia parameter of the grid-type converter is 0.7, the oscillation diverges faster. However, as the parameters of the grid-type converter increase, the speed of the divergent oscillation decreases, indicating that the dominant pole of the system moves to the left half of the complex plane. The time-domain electromagnetic simulation results further confirm that considering the inertia, droop parameters and their effects on the stability of the grid-type converter can improve the accuracy of quantitative analysis.

[0159] Table 7 Dominant poles obtained under different inertia and droop parameters

[0160]

[0161] Finally, the results of different power dispatch models are compared to verify the effectiveness of the optimization operation model of the present invention in a multi-grid-grid energy storage system. The program is developed using MATLAB R2020a with YALMIP, and Gurobi is used to solve the established MILP.

[0162] In order to demonstrate the advantages of this method, four power dispatching models were implemented in one day in the embodiment of the present invention:

[0163] Model 1: A model without small-signal stability constraints, that is, the effects of operating conditions and inertia and droop parameters on small-signal stability are not considered.

[0164] Model 2: Energy storage model with large fixed inertia and large droop parameter.

[0165] Model 3: A model that uses fixed small inertia and small droop parameters for energy storage.

[0166] Model 4: Using the optimization operation model proposed in the embodiment of the present invention, the energy storage inertia and droop parameters can be optimized within the allowable range to meet the frequency and small signal constraints in different time periods.

[0167] The rated frequency, frequency change rate, and steady-state deviation are 50 Hz, 2 Hz / s, and 0.25 Hz / s, respectively. The wind power generation data used in this study is from the National Renewable Energy Laboratory of the United States. The energy capacity to power capacity ratio of the energy storage system is fixed at 2, and the charge and discharge efficiency is set to 0.98. The power disturbance is set to 10% of the current output power of the entire system. The damping ratio is adopted σ is the real part of the eigenvalue, and ω is the imaginary part of the eigenvalue, which proves the small signal stability at different time points under different operating modes. The optimization results of different power dispatching models are shown in Figure 2. Figure 7 and as shown in Table 8.

[0168] like Figure 8 As shown in the figure, (a)-(d) represent the active power, steady-state frequency, frequency change rate and damping ratio of different models at different times. In case 1 (corresponding to model 1), without considering the small signal stability constraint, there is no wind power curtailment and all energy storage is used for frequency regulation reserve. However, during t = 1 to 14h, the damping ratio is lower than 0, indicating that the system is at risk of instability due to small disturbances. In case 2 (corresponding to model 2), wind power curtailment occurs when wind power resources are abundant, thereby controlling small disturbances within the constraint range. However, due to the large fixed inertia and droop parameters of the energy storage system, the energy storage is overused for frequency regulation, causing the frequency change rate and steady-state frequency values ​​to exceed the stability index. For case 3 (corresponding to model 3), the inertia and droop parameters are set to smaller values, resulting in a serious shortage of energy storage for frequency regulation. Therefore, wind power curtailment in the system increases. In case 4 (corresponding to model 4), small signal stability requires large inertia and droop parameters of the grid-type converter. The energy storage system absorbs electrical energy, and the smaller energy storage capacity is used as a frequency regulation reserve during t = 1 to 14 hours. When wind energy resources are less, the small signal stability has lower requirements on the inertia and droop parameters of the grid-type energy storage system, allowing it to release electrical energy. The results in Table 8 show that the method proposed in the present invention effectively utilizes the time-shift characteristics and variable parameters of the grid-type energy storage, and improves the utilization rate of renewable energy.

[0169] Table 8 Results of different operation modes

[0170]

[0171] Example 2

[0172] The embodiment of the present invention provides a multi-grid-type energy storage system optimization operation method system, including: a computer-readable storage medium and a processor;

[0173] Computer-readable storage media for storing executable instructions;

[0174] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the multi-grid-type grid-type energy storage system optimization operation method in Example 1. For related technical solutions, please refer to the corresponding description in Example 1.

[0175] Example 3

[0176] In an embodiment of the present invention, a computer readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the multi-grid-type grid-type energy storage system optimization operation method as in Embodiment 1 is implemented. For related technical solutions, please refer to the corresponding description in Embodiment 1.

[0177] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0178] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes 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 device that provides the functions specified in a block or multiple blocks.

[0179] 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 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0180] 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.

[0181] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0182] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0183] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing the operation of a multi-grid-type energy storage system, wherein the multi-grid-type energy storage system comprises M grid-type converters and N heterogeneous grid-type converters, M≥1, N≥1; characterized in that: include: The multi-grid-type energy storage system is equivalent to obtain an equivalent energy storage system; wherein the equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R and an ideal voltage source connected in series in sequence; the control parameters and operating parameters of the homogeneous grid-type converter correspond to the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid-type converters; the voltage of the ideal voltage source is the same as the rated voltage of each of the grid-type converters; the equivalent impedance Δδ(J,D) is the grid strength disturbance caused by the synchronous impedance of M grid-connected converters. J and D correspond to the inertia parameter and droop parameter of each grid-connected converter. g is the grid-connected admittance of the equivalent energy storage system without considering inertia and droop; Based on the equivalent energy storage system, the Routh criterion is used to obtain the small signal stability boundary conditions of the multi-grid-structured energy storage system; Taking minimizing the operating cost as the objective function, under the operating constraints including the small signal stability boundary conditions, the objective function is optimized and solved to obtain the inertia parameter J and droop parameter D of each grid-type converter at different times, so that each grid-type converter operates under corresponding J and D.

2. The method for optimizing operation of a multi-grid-type energy storage system according to claim 1, characterized in that: The multi-grid-structured energy storage system is equivalent to obtain an equivalent energy storage system, including: Each grid-type converter is equivalent to an ideal voltage source connected in series with an inductor, wherein the inductor includes an inductor with a fixed resistance and a variable inductor characterized by an inertia parameter J and a droop parameter D of each grid-type converter; the voltage of the ideal voltage source is the same as the rated voltage of each grid-type converter; The N heterogeneous grid-type converters are converted into N homogeneous grid-type converters; wherein the control parameters and operating parameters of each homogeneous grid-type converter correspond to the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid-type converters respectively; The energy storage system composed of the equivalent M grid-type converters and the N isomorphic grid-type converters is decoupled into N independent equivalent subsystems. The grid-connected reactance of the N independent equivalent subsystems and the reactance matrix Z of the multi-grid-type energy storage system are Lred The N eigenvalues ​​σ i Consistent, the order of magnitude is σ1≥σ2≥,...,≥σ N ≥0, i=1,...,N; The equivalent subsystem with the maximum grid-connected reactance σ1 is used as the equivalent energy storage system; wherein σ1=R.

3. The method for optimizing operation of a multi-grid-type energy storage system according to claim 2, characterized in that: The equivalent impedance Z of the inductor GFM for: Z GFM =Z mdq α(s)+Z mδ (J,D)α(s) Among them, Z mdq The impedance of the fixed-resistance inductor, Z mδ (J, D) is the impedance of the variable inductor; U d0 ,I d0 , Y0(s), θ0, ω0 represent the d-axis voltage, d-axis current, dq coordinate admittance, terminal voltage steady-state angle, and rated angular velocity of each grid-type converter respectively; s represents a complex frequency domain variable.

4. The method for optimizing operation of a multi-grid-type energy storage system according to claim 3, characterized in that: The grid strength disturbance Δδ(J,D) caused by the synchronous impedance of M grid-connected converters is: in, is the matrix Q red The block matrix, Q red is the Krona-reduced reactance matrix of N+M dimensions; S BM =diag{S BMi },S BMi is the capacity ratio of the rated capacity of the i-th grid-connected converter to the unit calculation base capacity, diag represents a diagonal matrix; v1 and u1 are the reactance matrix Z Lred The normalized left eigenvector and right eigenvector corresponding to the maximum eigenvalue of M represents the M-order identity matrix; the matrix represents the conjugate transpose of Q.

5. The method for optimizing operation of a multi-grid-type energy storage system according to claim 1, characterized in that: The small signal stability boundary condition of the multi-grid-type energy storage system is: Alternatively, the small signal stability boundary condition of the multi-grid-structured energy storage system is: Among them, U i0 、p i are the steady-state terminal voltage and participation factor of the ith heterogeneous grid-type converter, respectively; ω0 represents the rated angular velocity of each grid-type converter; For The steady-state weighted active power under For The steady-state weighted reactive power under Three-phase synchronous phase-locked loop PI constant k Lp,i and k Li,i Used to characterize the control parameters of the i-th heterogeneous grid-connected converter, and Used to characterize the control parameters of each isomorphic grid-type converter; P i0 is the steady-state active power of the i-th heterogeneous grid-type converter.

6. The method for optimizing operation of a multi-grid-type energy storage system according to claim 5, characterized in that: The operation constraints also include small signal constraints of N heterogeneous grid-type converters under different operating conditions: Wherein, σ1 is the reactance matrix Z of the multi-grid-structured energy storage system Lred The maximum eigenvalue of , and σ1=R.

7. The method for optimizing operation of a multi-grid-type energy storage system according to claim 1, characterized in that: The operating constraints also include frequency stability constraints: J min ≤J t ≤J max J max ≤D t ≤D max Among them, f0, RoCoF max are respectively the rated frequency, the maximum steady-state frequency, and the maximum frequency change rate of the multi-grid-type energy storage system; ΔP t is the disturbance power at time t, S BM,k is the capacitor of energy storage device k, which corresponds to the kth grid-type converter; J t and D t are the inertia parameters and droop parameters of each grid-connected converter at time t, J min , J max and D max are the minimum allowable inertia, maximum allowable inertia and maximum allowable droop parameters of each grid-connected converter respectively.

8. The method for optimizing operation of a multi-grid-type energy storage system according to claim 1, characterized in that: The objective function is: in, is the renewable energy curtailment penalty for renewable energy i at time t, where renewable energy i corresponds to the i-th heterogeneous grid-connected converter; is the power loss of energy storage device k at time t, and energy storage device k corresponds to the kth grid-connected converter.

9. A multi-grid-type energy storage system optimization operation system, characterized in that: comprising a computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the multi-grid-type grid-connected energy storage system optimization operation method described in any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, the method for optimizing operation of the multi-grid-type energy storage system as described in any one of claims 1 to 8 is implemented.

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