A method and system for optimizing the operation of a multi-grid-based energy storage system

Abstract

This invention belongs to the field of distributed energy storage control technology and discloses an optimized operation method and system for a multi-grid-connected energy storage system. The method includes: equivalencing the multi-grid-connected energy storage system to obtain an equivalent energy storage system; wherein the equivalent energy storage system includes a homogeneous grid-connected converter, an equivalent impedance R, and an ideal voltage source connected in series; based on the equivalent energy storage system, obtaining small-signal stability boundary conditions using the Routh criterion; and solving the objective function, with minimizing operating cost as the objective function, under operating constraints including the small-signal stability boundary conditions, to obtain the J and D values ​​of each grid-connected converter at different times, so that each grid-connected converter operates under the corresponding J and D values. This invention is applicable to the optimized operation configuration of energy storage systems containing multiple grid-connected converters, and can effectively promote the complementary advantages of renewable energy and energy storage, thereby improving system stability and operational economy.

Description

Technical Field

[0001] This invention belongs to the field of distributed energy storage control technology, and more specifically, relates to a method and system for optimizing the operation of a multi-grid-based energy storage system. Background Technology

[0002] As the proportion of renewable energy connected to grid-connected converters increases, it not only reduces grid inertia but also poses challenges to frequency support and system stability. Grid-connected energy storage systems using grid-connected converters are an effective way to address these issues. Grid-connected converters offer flexible and rapid bidirectional energy transfer capabilities, providing both inertia and frequency support. Furthermore, grid-connected converters do not require phase-locked loops (PLLs) for grid synchronization, avoiding the small-signal stability problems associated with PLLs. Therefore, energy storage systems containing multiple grid-connected converters play a crucial 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 create interactions between the grid-connected and grid-connected converters, making multi-grid-connected and grid-connected energy storage systems quite complex. Therefore, it is urgent to study the instability mechanisms of energy storage systems with multiple heterogeneous grid-connected and grid-connected converters in weak power grids, which are affected by phase-locked loop coupling. In existing stability analysis studies of multi-grid-connected and grid-connected energy storage systems, to simplify the model, the energy storage inertia parameter and droop parameter, which affect the small-signal stability of the energy storage system, are generally directly treated as fixed quantities. This can lead to instability or collapse of the energy storage system, reducing the safety and stability of the power system. Summary of the Invention

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

[0005] To achieve the above objectives, according to a first aspect of the present invention, a method for optimizing the operation of a multi-grid-connected energy storage system is provided. The multi-grid-connected energy storage system includes M grid-connected converters and N heterogeneous grid-connected converters, where M ≥ 1 and N ≥ 1; comprising:

[0006] The multi-grid-type energy storage system is equivalently transformed to obtain an equivalent energy storage system. The equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R, and an ideal voltage source connected in series. The control and operating parameters of the homogeneous grid-type converter correspond to the weighted control 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 grid-type converter. The equivalent impedance R... Δδ(J,D) represents the grid strength disturbance caused by the synchronous impedance of the M grid-connected converters, where J and D correspond to the inertia and droop parameters of each grid-connected converter, respectively, and λ. g The grid-connected admittance of the equivalent energy storage system without considering inertia and sag;

[0007] Based on the equivalent energy storage system, the small-signal stability boundary conditions of the multi-grid-structured energy storage system are obtained using the Routh criterion.

[0008] With minimizing operating cost as the objective function, and under operating constraints including the small-signal stability boundary condition, 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 the corresponding J and D.

[0009] Furthermore, the multi-grid-structured energy storage system is equivalently transformed 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 a fixed-resistance inductor and a variable inductor characterized by the inertia parameter J and 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 converters are transformed into N homogeneous grid converters; wherein, the control parameters and operating parameters of each homogeneous grid converter are the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid converters respectively.

[0012] The energy storage system, consisting 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 is related to the reactance matrix Z of the multi-grid-type energy storage system. Lred N eigenvalues ​​σ i Consistent, the order of magnitude is σ1≥σ2≥,...,≥σ N ≥0, i=1,...,N;

[0013] The equivalent subsystem with the largest grid-connected reactance σ1 is taken as the equivalent energy storage system; where σ1 = R.

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

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

[0016]

[0017] Among them, Z mdq Z represents the impedance of the inductor with a fixed resistance value. mδ (J,D) represents the impedance of the variable inductor; U d0 I d0 Y0(s), θ0, and 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 the complex frequency domain variable.

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

[0019]

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

[0021] in, It is matrix Q red The block matrix, Q red It is an N+M dimensional Cronowski reduced reactance matrix; S BM =diag{S BMi}, S BMi The ratio of the rated capacity to the unit calculated base capacity of the i-th grid-type converter is given by diag, where diag represents the diagonal matrix; v1 and u1 are the reactance matrix Z. Lred The normalized left and right eigenvectors corresponding to the largest eigenvalue; I M Denotes an M-order identity matrix; matrix This 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 for the multi-grid-structured energy storage system is:

[0025]

[0026] Among them, U i0 p i ωi represents the steady-state terminal voltage and participation factor of the i-th heterogeneous grid converter, respectively; ω0 represents the rated angular velocity of each grid converter. In order to be in steady-state weighted active power In order to be in steady-state weighted reactive power Three-phase synchronous phase-locked loop PI constant k Lp,i and k Li,i Control parameters used to characterize the i-th heterogeneous grid converter and Control parameters used to characterize each isomorphic grid converter; P i0 Let be the steady-state active power of the i-th heterogeneous grid converter.

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

[0028]

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

[0030] Furthermore, the operational 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 These are the rated frequency, maximum steady-state frequency, and maximum frequency change rate of the multi-grid-structured energy storage system, respectively; ΔP t Let S be the disturbance power at time t. BM,k It is the capacitor of energy storage unit k, which corresponds to the kth grid-type converter; J t and D t J represents the inertial parameters and droop parameters of each grid-type converter at time t. min J max and D max These are the minimum allowable inertia, maximum allowable inertia, and maximum allowable droop parameters for each grid-type converter.

[0035] Furthermore, the objective function is:

[0036]

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

[0038] According to a second aspect of the present invention, an optimized operation system for a multi-grid-structured energy storage system is provided, 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 executable instructions stored in the computer-readable storage medium and execute the multi-grid-based energy storage system optimization operation method as described in any one of the first aspects.

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

[0042] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

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

[0044] (2) Further, this invention provides a specific method for equivalent transformation of a multi-grid-connected energy storage system. After equivalence of each grid-connected converter, the influence of each grid-connected converter on the grid-connected converter can be concretized into an impedance voltage source model, which facilitates the clarification of the interaction between the grid-connected and grid-connected converters. At the same time, N heterogeneous grid-connected converters are equivalent to N homogeneous grid-connected converters. The control parameters and operating parameters of the equivalent homogeneous grid-connected converters are obtained by applying different control parameters to the original N heterogeneous grid-connected converters. The weighted calculation of control and operating parameters reflects the impact of the original N heterogeneous grid-connected converters on the stability of the energy storage system, effectively simplifying the stability analysis process. Thus, based on the equivalent M grid-connected converters and N homogeneous grid-connected converters, the multi-grid-connected energy storage system can be decoupled into N independent equivalent subsystems. Instability in any one of these equivalent subsystems implies instability in the original multi-grid-connected energy storage system before equivalence. Furthermore, σ... i The larger the value, the greater the possibility of system instability. Therefore, by selecting the equivalent subsystem with the largest grid-connected reactance (σ1) among N independent equivalent subsystems as the equivalent energy storage system, the high-order complex multi-grid-structured energy storage system can be reduced to a low-order simple subsystem.

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

[0046] (4) Furthermore, the operating constraints also include small-signal stability constraints for 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. By using weighted power and maximum grid-connected reactance σ1, it quantifies the stability boundary of multiple grid-connected converters under different operating conditions, enriching the connotation and application scenarios of small-signal stability criteria.

[0047] (5) As a preferred option, compared with the existing frequency stability constraints that treat the frequency regulation parameters of the energy storage system as scheduling variables, which mainly focus on frequency response characteristics, the present invention introduces the inertial parameters and droop parameters of each grid-type converter at each moment into the designed frequency stability constraints. By adjusting the inertial 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) Preferably, the present invention takes into account the cost of wind and solar curtailment penalties for renewable energy curtailment and the cost of energy storage charging and discharging power loss. These are the operating costs with the largest proportion and the most significant impact. By finding the minimum value of the objective function, the purpose of minimizing the operating costs is achieved, thereby optimizing the economic efficiency of system operation. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the optimized operation method of a multi-grid-structured energy storage system in an embodiment of the present invention.

[0050] Figure 2 This is a schematic diagram of the equivalent voltage source model of each grid-type converter in the embodiments of the present invention.

[0051] Figure 3 This is the equivalent model of the decoupled equivalent subsystem in the embodiments of the present invention.

[0052] Figure 4 This is a schematic diagram of the topology of the IEEE 39 test network used in this embodiment of the invention.

[0053] Figure 5 The time-domain response of multiple grid-connected converters under different operating conditions in the embodiments of the present invention is shown.

[0054] Figure 6 This is a schematic diagram illustrating the influence of inertia and damping on power grid strength in an embodiment of the present invention.

[0055] Figure 7 The present invention provides the time-domain response of multiple grid-connected converters under different inertia and droop parameters in embodiments of the present invention.

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

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0058] In this invention, the terms "first," "second," etc., used in the invention and 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, this embodiment of the invention provides an optimized operation method for a multi-grid-connected energy storage system. The multi-grid-connected energy storage system includes M interconnected grid-connected converters and N heterogeneous grid-connected converters, where M ≥ 1 and N ≥ 1. The optimized operation method for this multi-grid-connected energy storage system includes:

[0061] The multi-grid-type energy storage system is equivalently transformed to obtain the equivalent energy storage system. The equivalent energy storage system includes a homogeneous grid-type converter, an equivalent impedance R, and an ideal voltage source connected in series. The control and operating parameters of the homogeneous grid-type converter correspond to the weighted control 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 R... Δδ(J,D) represents the grid strength disturbance caused by the synchronous impedance of the M grid-connected converters, where J and D correspond to the inertia and droop parameters of each grid-connected converter, respectively, and λ. g The grid-connected admittance of the energy storage system after neglecting inertia and sag;

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

[0064] Preferably, the multi-grid-type energy storage system is equivalently represented to obtain an equivalent energy storage system, which includes: each grid-type converter being 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 droop parameter D of the current grid-type converter; in this embodiment of the invention, the rated voltage, inertia parameter J and droop parameter D of the M grid-type converters are all the same;

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

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

[0067] The multi-grid-connected grid-type energy storage system optimization operation method of the present invention, by equivalentizing each grid-connected converter, can concretize the influence of the grid-connected converter on the grid-connected converter into an impedance voltage source model, which facilitates the understanding of the interaction between the grid-connected and grid-connected converters. Simultaneously, by equivalentizing N heterogeneous grid-connected converters into N homogeneous grid-connected converters, the stability operation analysis process of the energy storage system is effectively simplified. The control parameters of the equivalent homogeneous grid-connected converters are obtained by weighted calculation of the different control parameters of the original N heterogeneous grid-connected converters, and the operating parameters of the equivalent homogeneous grid-connected converters are obtained by weighted calculation of the different operating parameters of the original N heterogeneous grid-connected converters, which can reflect the influence of the control and operating parameters of the original N heterogeneous grid-connected converters on the stability of the energy storage system. Thus, based on the equivalent M grid-connected converters and N homogeneous grid-connected converters, the energy storage system can be decoupled into N... Since the grid-connected reactance is larger among the N independent equivalent subsystems, the energy storage system is more likely to be unstable. Therefore, the equivalent subsystem with the largest grid-connected reactance among the N independent equivalent subsystems is taken as the equivalent multi-grid-structured energy storage system. This can reduce the high-order complex multi-grid-structured energy storage system to a low-order simple subsystem. Based on this low-order simple subsystem, the Routh criterion can be used to obtain the small-signal stability boundary conditions of the multi-grid-structured energy storage system with the inertial parameter J and droop parameter D of each grid-type converter as decision variables. Using this small-signal stability boundary condition as one of the operating constraints, the optimization problem with minimizing the operating cost as the objective function can be solved. The inertial 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 inertial parameter J and droop parameter D, which can improve the operational stability and safety of the multi-grid-structured energy storage system.

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

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

[0070]

[0071] Among them, Z mdq Z represents the impedance of an inductor with a fixed resistance value. mδ (J,D) represents the impedance of a variable inductor characterized by its inertia and droop parameters; U d0 I d0 These represent the d-axis voltage and current of the current grid-type converter, respectively; L F C F These represent the filter inductance and filter capacitor of the current grid-type converter, respectively; f VF (s)=1 / (T VF s+1) represents the filter for the voltage feedforward signal in the current grid-type converter, T VF PI represents the filter's time constant, s represents the complex frequency domain variable; 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-type converter, respectively, and K CCP K CCI K represents the proportional and integral gain of the current loop PI controller, respectively. VCP K VCI θ0 and ω0 represent the proportional and integral gains of the PI controller in the voltage loop, respectively; 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 this embodiment of the invention, through theoretical analysis, each grid-type 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 and droop parameters. The influence of the grid-type converter on the follow-up grid converter is concretized into an impedance voltage source model, which facilitates the subsequent explanation of the interaction between the grid-type and follow-up grid converters, thereby greatly simplifying the analysis of the influence of the grid-type converter on the small-signal stability of the follow-up grid converter.

[0073] To further simplify the model of the grid converter, in this embodiment of the invention, N heterogeneous grid converters are equivalent to N homogeneous grid converters.

[0074] Based on the energy storage system composed of M equivalent 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, which corresponds to the reactance matrix Z of the energy storage system. Lred eigenvalues ​​(σ) i (i = 1, ..., N), the order of magnitude is σ1 ≥ σ2 ≥, ..., ≥ σ N ≥0. If any equivalent subsystem is unstable, it means that the original energy storage system prior to the equivalent is also unstable. Furthermore, σ i The larger the value, the greater the possibility of system instability. Therefore, the subsystem with the largest grid-connected reactance (σ1) among N independent equivalent subsystems is selected as the most critical subsystem.

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

[0076]

[0077] in,

[0078]

[0079] In the formula, U x,i0 U y,i0 I x,i0 and I y,i0 The operating parameters of the i-th grid converter are shown in separate tables, representing the steady-state terminal voltage and output current in the global xy coordinate system. ω0 is the rated angular velocity of each grid converter, and k... Lp,i and k Li,i Let p be the control parameters of the i-th grid converter, and let p be the PI constant of the three-phase synchronous phase-locked loop of the i-th grid converter. i As a participating factor, p i =u i1 v i1 (i = 1, ..., N), u i1 and v i1 These are the reactance matrices Z of the energy storage system. Lred The i-th element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the largest eigenvalue; U i0 Ii represents the steady-state terminal voltage of the i-th grid-connected converter; I2 represents the second-order identity matrix; and σ1 is the largest grid-connected reactance in the N independent equivalent subsystems.

[0080] As can be seen from this state matrix, establishing an equivalent system containing N homogeneous grid converters effectively simplifies the analysis process. Furthermore, the control and operating parameters of the equivalent homogeneous grid converters are obtained by applying different control parameters (k) to the original heterogeneous N grid converters. Lp,i and k Li,i ) and operating parameters (U x,i0 U y,i0 I x,i0 and I y,i0 The weighted calculation is obtained and can reflect the impact of the control parameters and operating parameters of the original heterogeneous N grid-connected converters on the stability of the energy storage system.

[0081] like Figure 3 The diagram shown is an equivalent model of the most critical subsystem, which is also the equivalent multi-grid-type energy storage system. It includes a series-connected isomorphic grid-type converter, an equivalent impedance, and an ideal voltage source. The voltage of this ideal voltage source is equal to the equivalent ideal voltage source voltage of each grid-type converter. The equivalent impedance... The equivalent admittance of each equivalent subsystem consists of two parts: one part is the grid connection admittance λ of the most critical subsystem when inertia and droop are not considered. g 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 optimized multi-grid-connected energy storage system, the Routh criterion is used to obtain the stability boundary conditions of the N grid-connected converters under different operating conditions and the small-signal stability boundary conditions of the multi-grid-connected energy storage system. The stability boundary conditions of the N grid-connected converters under different operating conditions can serve as the small-signal stability criteria for the N grid-connected converters under different operating conditions; the small-signal stability boundary conditions of the multi-grid-connected energy storage system can serve as the small-signal stability criteria for the multi-grid-connected energy storage system. In this embodiment of the invention, the corresponding criteria are used as one of the constraints of the system optimization operation model.

[0083] Preferably, the stability boundary conditions for N heterogeneous grid converters under different operating conditions are:

[0084]

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

[0086]

[0087] Where, θ i0 θ j0 The steady-state angles of the terminal voltages of the i-th and j-th grid-connected converters are respectively; k Lp,i and k Li,i U represents the PI parameters of the three-phase synchronous phase-locked loop of the i-th grid converter; j0 P j0 and Q j0 These represent the steady-state terminal voltage, active power, and reactive power of the j-th grid-connected converter, respectively; 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 These are the reactance matrices Z of the energy storage system. Lred The i-th element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the largest eigenvalue, u j1 and v j1 These are the reactance matrices Z of the energy storage system. Lred The j-th element of the normalized left eigenvector u1 and right eigenvector v1 corresponding to the largest eigenvalue; It is an intermediate variable.

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

[0089] Preferably, the small-signal stability boundary condition for a multi-grid-based energy storage system is:

[0090]

[0091] Where, λ g For 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, defined as follows:

[0092]

[0093] in, It is matrix Q red The block matrix, Q red It is an N+M dimensional Cronowski reduced reactance matrix; S BM =diag{S BMi}, S BMi Let diag be the ratio of the rated capacity of the i-th grid-type converter to the unit calculated base capacity, and let diag denote the diagonal matrix; M This represents an M-order identity matrix. In this embodiment of the invention, the matrix... Y represents the conjugate transpose of Q. δ (J,D) and residual admittance Y δ (s) indicates the relationship between them:

[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 different steady-state angle difference (θ) of the grid converter i0 -θ j0 The small signal stability boundary conditions of the multi-grid-connected energy storage system are typically small, and since the focus of this embodiment is on the active power of the grid-connected converter, the small signal stability boundary conditions can be rewritten as follows:

[0098]

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

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

[0101] Specifically, taking minimizing operating costs as the objective function, and preferably, the objective function of the optimized operation model of the multi-grid-structured energy storage system in this embodiment of the invention is:

[0102]

[0103] Where t is the time index, from 1 to T; i is the renewable energy index, from 1 to N; and k is the energy storage index, from 1 to M. It is the penalty for curtailment of renewable energy (solar and wind) at time t. It represents the power loss of energy storage device k at time t. Energy storage device k corresponds to grid-connected converter k, and renewable energy i corresponds to grid-connected converter i.

[0104] and The definition is as follows:

[0105]

[0106] Where rc is the penalty coefficient for curtailment of renewable energy (solar and wind power); Let i represent the predicted power and planned power of renewable energy i at time t, respectively. and Let $t$ be the discharge loss and the charging loss of energy storage device $k$ at time $t$. and Let η be the discharge power and charging power of energy storage device k at time t, respectively; D,k and η C,k These represent the discharge efficiency and charging efficiency of energy storage device k, respectively.

[0107] In this embodiment of the invention, the penalty costs for curtailing wind and solar power and the power loss costs of energy storage charging and discharging are comprehensively considered. These are the operating costs that account for the largest proportion and have the most significant impact. By finding the minimum value of the objective function, the goal of minimizing operating costs is achieved, thereby optimizing the economic efficiency of system operation.

[0108] Taking the constructed small-signal stability boundary conditions as one of the operational constraints, the small-signal stability constraint conditions are as follows:

[0109]

[0110] J min ≤J t ≤J max

[0111] J max ≤D t ≤D max

[0112] in, and J represents the planned power generation of the i-th grid-connected converter at time t; t and D t Let J be the inertial parameters and droop parameters of the grid-type converter at time t, respectively, and be the decision variables; min J max and D max These are the minimum allowable inertia, maximum allowable inertia, and maximum allowable droop parameters for the current grid-type converter; Δδ(J t D t The value t represents the grid strength disturbance caused by the synchronous impedance of each grid-type converter at time t.

[0113] In this embodiment of the invention, based on the small-signal stability constraints designed for the decoupled N subsystems, the energy storage inertia parameters and droop parameters that affect the stable operation of the energy storage system are used as optimization variables. By optimizing and solving the objective function, the inertia parameters and droop parameters of each grid-type converter at each time step can be obtained. The system can achieve stable operation under the corresponding optimized 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 operational constraints of the multi-grid-based energy storage system optimization operation model in this 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-based energy storage system. For multi-grid-based energy storage systems, RoCoF max The maximum frequency change rate of a multi-grid-based energy storage system; S BM,k It is the capacitor of energy storage k; ΔP t The disturbance power at time t is typically related to the output power of the energy storage system at time t. Related.

[0120] Compared to existing frequency stability constraints that treat the frequency regulation parameters of energy storage systems as scheduling variables and mainly focus on frequency response characteristics, this invention incorporates the inertial parameters and droop parameters of each grid-type converter at each moment into the designed frequency stability constraints. By adjusting the inertial parameters and droop control parameters in real time, the power system can maintain a nearly constant frequency, which helps ensure frequency synchronization between various devices and loads within the system and improves the system's operating efficiency.

[0121] In this embodiment of the invention, the operational 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, It is the output power of the energy storage system at time t. and Let be the discharge power and charging power of energy storage device k at time t, respectively.

[0125] The constraints for renewable energy are:

[0126]

[0127] in, The planned power generation of the i-th grid-connected converter cannot exceed the predicted power generation.

[0128] Energy storage constraints are:

[0129]

[0130] in, Δt represents the remaining energy of energy storage device k at time t; Δt is the planned interval time. and S represents the minimum and maximum allowable residual energy of the energy storage device k; BM,k It is the capacitor of energy storage device k; It is the state of energy storage device k at time t. This indicates that the energy storage device k is in a charging state at time t. Indicates the discharge state; and Let η be the discharge power and charging power of energy storage device k at time t. D,k and η C,k These represent the discharge efficiency and charging efficiency of energy storage device k, respectively.

[0131] The energy storage backup capacity constraint is:

[0132]

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

[0134] In this embodiment of the invention, based on the basic constraints of the energy storage power system (power balance constraints, renewable energy constraints, energy storage constraints, and energy storage reserve capacity constraints), the optimal system operation scheme, through the design of small-signal stability constraints and frequency stability constraints, can achieve the lowest operating cost while taking into account system safety and stability and frequency fluctuation limits, thereby improving power quality, increasing energy storage utilization, and realizing the economical operation of the power grid.

[0135] The method of this invention can improve the safety and stability of power systems: by rationally allocating inertia and droop control, it can maintain the stability of power systems with multiple grid-connected converters under small disturbances, which helps to prevent system instability or collapse and improve system safety and reliability.

[0136] The method of this invention enables frequency control optimization: by adjusting the inertia parameters and droop control parameters in real time, the power system can maintain a near-constant frequency, which helps ensure frequency synchronization between various devices and loads within the system and improves the system's operating efficiency.

[0137] The method of this invention can reduce the operating cost of energy storage systems: by optimizing the operation of multiple grid-connected converters, the system can reduce power generation costs as much as possible while meeting stability requirements, which helps to reduce the consumption of energy resources and improve the economic efficiency of the power system.

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

[0139] Overall, this invention provides a theoretical basis and solution for the operation optimization problem of multi-grid converter power systems, and is of great significance for improving the small-signal stability and operating economy of multi-grid converter power systems.

[0140] The following is based on Figure 4 Taking the multi-grid-connected grid-type energy storage system shown as an example, the effectiveness of the stability boundary of the proposed method under different operating conditions and different inertia-droop parameters is verified. In this system, nine wind power plants are connected to grid-connected converters at buses 1-3, 5, and 7-11, and two energy storage systems are connected to grid-connected converters at buses 4 and 6. Figure 4 All other numbers in the table represent bus parameters. Control parameters for grid-connected and grid-connected converters are detailed in Table 1-2. Furthermore, the energy storage system capacities are 0.8 pu and 1.2 pu, respectively. Time-domain electromagnetic simulations of the system were performed using MATLAB / Simulink.

[0141] Table 1 shows the parameters of the grid converter.

[0142]

[0143] Table 2 Parameters of Network Converters

[0144]

[0145] First, to verify the effectiveness of the method proposed in this embodiment of the invention in analyzing the stability of multiple grid-connected converters under different operating conditions, the energy storage system connected to the grid via the grid-connected converter was not connected to the system. The grid-connected admittance of the most critical subsystem, neglecting inertia and droop, can be calculated as: λ g =2.8953. Table 3 lists three different operating conditions.

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

[0147]

[0148] When all grid-type converters have the same PLL parameters (8, 9500), the comparison of the system dominant poles evaluated by the full-order model (the model without decoupling equivalence) and the method in this invention under the three cases is shown in Table 4. Table 4 compares the system dominant poles under the three scenarios. The results show that the relative error between the dominant poles obtained by the full-order model and the method in this invention is negligible under all three operating conditions. This proves the effectiveness of the decoupled model proposed in this 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 operating conditions are shown below. Figure 5 In Scenario 1, divergent oscillations occurred, indicating system instability. In contrast, Scenario 3 showed convergent oscillations, indicating system stability. These time-domain simulation results are consistent with the modal analysis results in Table 4, further validating the effectiveness of this method.

[0150] When the phase-locked loop parameters differ from those of the grid converter, as shown in Table 5, modal analysis can be performed based on the full-order model and the simplified model proposed in this invention (the decoupled model). Table 6 lists the dominant poles of the system under three operating conditions. Lp / k Li The increase indicates an expansion of the system's stability boundary. Compared to the dominant poles in Table 4, the real parts of the dominant poles are smaller, indicating improved system stability. The modal analysis results are consistent with our method. Furthermore, under all three operating conditions, the relative error between the dominant poles derived from the full-order model and those derived by our method remains below 1%, demonstrating the effectiveness of our method in applying it to multiple grid-type converters with different PLL parameters.

[0151] Table 4 shows the dominant poles obtained in three cases.

[0152]

[0153] Table 5 Control parameters of multiple phase-locked loops for grid-connected converters

[0154]

[0155] Table 6 shows the dominant poles obtained under three different conditions of the phase-locked loop.

[0156]

[0157] Then, the effectiveness of this method in analyzing the stability of multiple grid-connected energy storage systems was verified under different inertia and droop parameters. In this case, the quantitative analysis of the stability of the grid-connected converter using the proposed grid-connected converter inertia and droop parameters was validated. When the influence of the grid-connected converter's inertia and droop parameters on grid strength is ignored, λ... g The value can be calculated as: λ g =3.5539. Compared with multiple grid-connected converters, the grid strength is improved. Based on the aforementioned grid parameters and this method, the influence of inertia and droop parameters on grid strength can be obtained as follows: Figure 6 As shown, with the increase of the inertia and droop parameters of the grid-connected converter, the degree of grid strength weakening decreases. This indicates that when the inertia and droop parameters are large, the grid-connected converter can be approximated as a converter connected in series with impedance Z. GFMThe voltage source.

[0158] Table 7 lists the dominant poles of the entire system under different inertia and droop parameters in Case 1, as well as the dominant poles obtained by this method. The results in the table show 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 converter is 0.7, the oscillation diverges faster. However, as the parameters of the grid converter increase, the rate of divergent oscillation decreases, indicating that the dominant pole of the system shifts to the left half of the complex plane. The time-domain electromagnetic simulation results further confirm that considering inertia, droop parameters, and their effects on the stability of the grid converter can improve the accuracy of quantitative analysis.

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

[0160]

[0161] Finally, results from different power dispatch models were compared to verify the effectiveness of the optimized operation model of this invention in multi-grid-grid energy storage systems. The program was developed using MATLAB R2020a with YALMIP, and Gurobi was used to solve the established MILP.

[0162] To demonstrate the advantages of this method, in this embodiment of the invention, four power dispatch models were implemented within one day:

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

[0164] Model 2: An 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 optimized operation model proposed in the embodiments 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 at different time periods.

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

[0168] like Figure 8 As shown, (a)-(d) represent the active power, steady-state frequency, rate of frequency change, and damping ratio of different models at different times. In Case 1 (corresponding to Model 1), without considering small-signal stability constraints, there is no wind power reduction, and all energy storage is used for frequency regulation reserves. However, during t = 1–14 h, the damping ratio is below 0, indicating a risk of instability due to small disturbances. In Case 2 (corresponding to Model 2), wind power reduction occurs when wind resources are abundant, thus keeping small disturbances within constraints. However, due to the large fixed inertia and droop parameters of the energy storage system, excessive use of energy storage for frequency regulation leads to the rate of frequency change and steady-state frequency exceeding stability indicators. For Case 3 (corresponding to Model 3), the inertia and droop parameters are set to small values, resulting in a severe shortage of energy storage for frequency regulation. Therefore, wind power reduction in the system increases. In Case 4 (corresponding to Model 4), small-signal stability requires larger inertia and droop parameters for the grid-connected converter. The energy storage system absorbs electrical energy, with a relatively small storage capacity serving as frequency regulation reserve during the period t = 1–14 h. When wind energy resources are scarce, the small-signal stability requirements for the inertia and droop parameters of the grid-type energy storage system are lower, allowing it to release electrical energy. The results in Table 8 show that the method proposed in this invention effectively utilizes the time-shift characteristics and variable parameters of grid-type energy storage, improving the utilization rate of renewable energy.

[0169] Table 8 Results of different operating modes

[0170]

[0171] Example 2

[0172] This invention provides a method for optimizing the operation of a multi-grid-based energy storage system, comprising: a computer-readable storage medium and a processor;

[0173] Computer-readable storage media are used to store executable instructions;

[0174] The processor is used to read executable instructions stored in a computer-readable storage medium and execute the multi-grid-based energy storage system optimization operation method in Embodiment 1. Related technical solutions are described in the corresponding section of Embodiment 1.

[0175] Example 3

[0176] This invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the optimized operation method for a multi-grid-based energy storage system as described in Embodiment 1. Related technical solutions are described in the corresponding section of Embodiment 1.

[0177] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take 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.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0178] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0179] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0180] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0181] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0182] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0183] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A method for optimizing the operation of a multi-grid-connected energy storage system, wherein the multi-grid-connected energy storage system comprises M grid-connected converters and N heterogeneous grid-connected converters, M≥1, N≥1; characterized in that, include: The multi-grid-structured energy storage system is equivalently transformed to obtain an equivalent energy storage system; wherein, the equivalent energy storage system includes a homogeneous grid-type converter connected in series, and an equivalent impedance. A single ideal voltage source; the control parameters and operating parameters of the homogeneous grid converter correspond to the weighted control parameters and operating parameters of the N heterogeneous grid converters; the voltage of the ideal voltage source is the same as the rated voltage of each grid converter; the equivalent impedance , The grid strength disturbance is caused by the synchronous impedance of the M grid-connected converters. J and D Corresponding to the inertial and droop parameters of each grid-type converter, λ g The grid-connected admittance of the equivalent energy storage system without considering inertia and sag; Based on the equivalent energy storage system, the small-signal stability boundary conditions of the multi-grid-structured energy storage system are obtained using the Routh criterion. Using minimizing operating cost as the objective function, and under operational constraints including the small-signal stability boundary conditions, the objective function is optimized and solved to obtain the inertial parameters of each grid-type converter at different times. J and droop parameters D To ensure that each grid-type converter operates at the corresponding inertial parameters J and droop parameters D Run it.

2. The optimized operation method for a multi-grid-structured energy storage system according to claim 1, characterized in that, The multi-grid-structured energy storage system is then converted into an equivalent energy storage system, which includes: 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 an inertia parameter of each grid-type converter. J and droop parameters D A variable inductor characterized by the ideal voltage source having the same voltage as the rated voltage of each of the grid-type converters; The N heterogeneous grid converters are transformed into N homogeneous grid converters; wherein, the control parameters and operating parameters of each homogeneous grid converter are the control parameters and operating parameters obtained by weighting the control parameters and operating parameters of the N heterogeneous grid converters respectively. The energy storage system, consisting 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 is related to the reactance matrix Z of the multi-grid-type energy storage system. Lred N eigenvalues ​​σ i Consistent, size order is σ 1 ≥σ 2 ≥ ,..., ≥σ N ≥0, i= 1,..., N ; Will have the largest grid-connected reactance σ The equivalent subsystem of 1 serves as the equivalent energy storage system; wherein, .

3. The optimized operation method for a multi-grid-structured energy storage system according to claim 2, characterized in that, The equivalent impedance of the inductor for: in, This represents the impedance of the inductor with a fixed resistance value. The impedance of the variable inductor; U d0 , I d0 , , , These represent the d-axis voltage, d-axis current, dq coordinate admittance, terminal voltage steady-state angle, and rated angular velocity for each grid-type converter, respectively; s represents the complex frequency domain variable.

4. The optimized operation method for a multi-grid-structured energy storage system according to claim 3, characterized in that, Grid strength disturbance caused by the synchronous impedance of M grid-type converters for: in, , , , It is matrix Q red The block matrix, Q red yes N+M The Kronen reduction of the reactance matrix in dimensionality; , S BMi For the first i The ratio of the rated capacity of a grid-type converter to the unit calculated base capacity. Represents a diagonal matrix; and The reactance matrix Z is respectively Lred The normalized left and right eigenvectors corresponding to the largest eigenvalue; express M identity matrix; matrix express The conjugate transpose of .

5. The optimized operation method for a multi-grid-structured energy storage system according to claim 1, characterized in that, The small-signal stability boundary condition for the multi-grid-structured energy storage system is: Alternatively, the small-signal stability boundary condition for the multi-grid-structured energy storage system is: in, U i0 , p i The first i Steady-state terminal voltage and participation factor of a heterogeneous grid converter; This indicates the rated angular velocity of each grid-type converter; In order to be in steady-state weighted active power In order to be in steady-state weighted reactive power , PI constant of three-phase synchronous phase-locked loop k Lp,i and k Li,i Used to characterize the i Control parameters for heterogeneous and grid-type converters and Control parameters used to characterize each isomorphic grid converter; For the first i The steady-state active power of a heterogeneous grid converter.

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

7. The optimized operation method for a multi-grid-structured energy storage system according to claim 1, characterized in that, The operational constraints also include frequency stability constraints: in, f 0、 , These are the rated frequency, steady-state maximum frequency, and maximum frequency change rate of the multi-grid-structured energy storage system, respectively. for t The power of the disturbance at any given moment. It is an energy storage device k capacitors, energy storage devices k Corresponding to the k Individual grid-type converter; and They are respectively t The inertial parameters and droop parameters of each grid-type converter at any given time. , and These are the minimum allowable inertia, maximum allowable inertia, and maximum allowable droop parameters for each grid-type converter.

8. The optimized operation method for a multi-grid-structured energy storage system according to claim 1, characterized in that, The objective function is: in, It is a renewable energy source i exist t Penalties for curtailing solar and wind power in the meantime; renewable energy i Corresponding to the i A heterogeneous grid converter; It is an energy storage device k exist t Power loss at any moment, energy storage k Corresponding to the k Individual grid-type converter.

9. A multi-grid-based energy storage system for optimized operation, characterized in that, Includes computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the optimized operation method of the multi-grid-structured energy storage system according to 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, it implements the optimized operation method of the multi-grid-structured energy storage system as described in any one of claims 1-8.

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