Method, system and related device for calculating fault current of constructed network type energy storage

Abstract

The invention discloses a network construction type energy storage fault current calculation method and system and a related device, and belongs to the technical field of energy storage. The method comprises the following steps: obtaining power grid strength data of a network construction type energy storage grid-connected point based on a network construction type energy storage fault current transient model, and calculating to obtain network-side equivalent impedance based on the power grid strength data of the network construction type energy storage grid-connected point; analyzing the damping state of the second-order system which generates the phase angle variation at present; according to the initial internal potential amplitude and the phase angle during the steady-state period of the constructed network type energy storage, calculating to obtain a current instantaneous value at the last moment of the steady state; according to the damping state of the second-order system generating the phase angle variable quantity and the dynamic change relation of the internal potential amplitude when the power grid voltage amplitude suddenly changes, calculating the dynamic response of the internal potential amplitude and the phase angle of the constructed energy storage; and according to the internal potential amplitude and the phase angle dynamic response, a deconstruction network type energy storage fault current expression is solved. The method can provide a guidance basis for overload control design, parameter selection and device type selection of network-forming type energy storage.

Description

Technical Field

[0001] The invention proposes a grid-type energy storage fault current calculation method, system and related devices, belonging to the technical field of energy storage. Background Art

[0002] Grid-Forming Energy Storage System (GFM-ESS) usually adopts the power synchronization strategy of simulating synchronous generators, which can achieve synchronization without the help of phase-locked loops, and can improve the stability and flexibility of the system after a high proportion of new energy generators are connected to the grid. It can provide a variety of support functions for the power grid without additional cost investment, including maintaining the stability of the grid frequency, quickly adjusting the voltage, suppressing the oscillation of the power system, and enhancing the carrying capacity of short-circuit current, aiming to ensure the stable operation of the power grid and help increase the proportion of renewable energy in the power grid.

[0003] The grid-type energy storage presents voltage source characteristics to the outside, and the key parameters of its control link include the internal potential amplitude E m and phase angle i m. Under the VSG strategy, the internal potential amplitude E m is based on the reactive power reference value through the first-order inertia link Q mref and actual value Q Deviation generation of m; internal potential phase angle i m is based on the active power reference value P mref and actual value P m is generated by a second-order system simulating the swing characteristics of the generator. Before the fault occurs (denoted as t =0-), after (recorded as t =0+), E m and i m remains unchanged under the control system, while the grid-side voltage and phase angle may change suddenly due to a fault, resulting in a change in the potential amplitude and phase angle of the grid-type energy storage. t =0+, there is a deviation between the phase angle of the voltage amplitude on the grid side and the voltage on the grid side, which generates a large amount of fault current.

[0004] The current calculation of fault current for grid-type energy storage has the following limitations: (1) The calculation of fault current for grid-type energy storage in most literature is performed at the electromechanical transient scale. However, for fault current, it generally reaches its maximum value about half a cycle (10 ms) after the fault. The calculation at the electromechanical transient scale is difficult to reflect the dynamic characteristics of fault current at the millisecond level, and it is not easy to select and design parameters for grid-type energy storage equipment; (2) The existing control strategy model for grid-type energy storage does not accurately reflect the dynamic characteristics of the potential amplitude and phase angle of the grid-type energy storage under the disturbance of the grid-side voltage amplitude and phase angle, which makes it difficult to calculate the fault current based on the existing model; (3) Most current fault current calculations do not take phase angle jumps into account. When a short-circuit fault occurs near the grid-type energy storage, a large jump in the grid-side voltage phase angle will lead to a large instantaneous overcurrent, and at the same time cause a decrease in the active and reactive power control capabilities of the grid-type energy storage. Summary of the invention

[0005] In order to overcome the shortcomings of existing grid-type energy storage fault current calculation, the present invention provides a grid-type energy storage fault current calculation method taking into account amplitude and phase angle mutations. This method can provide guidance for overload control design, parameter selection and device selection of grid-type energy storage.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a method for calculating a grid-type energy storage fault current, comprising: Based on the transient model of grid-type energy storage fault current, the grid strength data of the grid-type energy storage grid connection point is obtained, and the grid-side equivalent impedance is calculated based on the grid strength data of the grid-type energy storage grid connection point; Obtain key parameters of grid-type energy storage, and analyze the damping state of the second-order system that currently generates phase angle variation based on the key parameters of grid-type energy storage and grid-side equivalent impedance; According to the initial internal potential amplitude and phase angle during the steady-state period of the grid-type energy storage, the instantaneous value of the current at the last moment of the steady-state is calculated; According to the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes, the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage is calculated; According to the dynamic response of internal potential amplitude and phase angle and combined with the instantaneous value of current, the fault current expression of grid-type energy storage is solved.

[0007] As a further improvement of the present invention, the grid-forming energy storage fault current transient model includes: an equivalent circuit of the grid-forming energy storage connected to the power grid and a strategy for generating the internal potential amplitude and phase angle of the grid-forming energy storage; In the grid-connected equivalent circuit of grid energy storage, the grid voltage phasor is recorded as U g =U g ∠ i g ,in, U g is the grid voltage phasor, U g is the grid voltage amplitude, i g is the grid voltage phase; The grid-side equivalent impedance is expressed as Z g = R g +j X g ,in, Z g is the grid-side equivalent impedance, R g is the grid-side equivalent resistance, X g is the grid-side equivalent reactance, is an imaginary number; The potential phasor in the grid-type energy storage is expressed as E m = E m ∠ i m ,in, E m is the potential phasor in the grid-type energy storage, U m is the potential amplitude of the grid-type energy storage, i m is the potential phase inside the grid-type energy storage; The machine side impedance is expressed as Z m = R m +j X m ,in, Z m is the equivalent impedance on the machine side, R m is the equivalent resistance on the machine side, X m is the equivalent reactance on the generator side. Since the equivalent resistance on the grid side is usually much smaller than the equivalent reactance on the grid side, Z g =j X g ; In the internal potential amplitude and phase angle generation strategy of grid-type energy storage, the output complex power of VSG strategy grid-type energy storage is expressed as:

[0008] in,I m is the output current phasor of the grid-type energy storage, and the symbol “^” represents conjugation; Δ i m Indicates the phase change of the potential in the grid-type energy storage; The active power output of the grid-connected energy storage is P m , the reactive power is Q m , respectively expressed as:

[0009] The active power change rate is Δ P m , the reactive power change is Δ Q m , the expression is as follows:

[0010]

[0011] in, E mref Indicates the potential amplitude command value in the grid-type energy storage; U g0 Indicates the steady-state value of the grid-side voltage amplitude; Δ i m , Δ E m , Δ U g They are respectively the phase change of the potential inside the grid-forming energy storage, the amplitude change of the potential inside the grid-forming energy storage, and the amplitude change of the voltage on the grid side; k p , m q , n q They are phase change gain coefficient, grid-type energy storage internal potential amplitude change gain coefficient, grid-side voltage amplitude change gain coefficient respectively; Δ i m , Δ E m The change in active power command value Δ P mref , grid side phase angle change Δ i g The change in reactive power command value Δ Q mref , the change of the internal potential amplitude command value Δ E mref , grid-side voltage amplitude change Δ U g The transfer function is as follows:

[0012]

[0013] in, oh 0 is the rated frequency of the power grid, J To construct the virtual inertia of network energy storage, D To construct a virtual damping network energy storage, k q is the reactive power coefficient of grid-type energy storage.

[0014] As a further improvement of the present invention, the key parameters of the grid-type energy storage include virtual inertia J , Virtual Damping D , reactive power coefficient k q .

[0015] As a further improvement of the present invention, the damping state of the second-order system currently generating the phase angle variation is analyzed based on the key parameters of the grid-type energy storage and the grid-side equivalent impedance, including: First, the dynamic change trend of the internal potential phase angle when the grid voltage phase angle changes suddenly is obtained, including: The change of potential phase angle in grid-type energy storage and Δ i g ( s ) is related to the transfer function of the term, Δ i g ( s ) is a second-order system, which is transformed as follows:

[0016] in, oh c is the undamped natural oscillation angular frequency of the second-order system, x is the equivalent damping ratio of the second-order system, expressed as:

[0017] When calculating the fault current, first consider the parameters involved. J , D Determine the damping characteristics of the second-order system and then solve Δ based on the equation i m The dynamic response of x The specific values ​​are as follows: like, x >1, it is an overdamped case, there are two negative real characteristic roots, the two characteristic roots are recorded as s 1,2 ,have:

[0018] Given a step change in the grid voltage phase angle, the phase angle change Δ i m The dynamic response in the time domain is:

[0019] like, x =1, which is the critical damping case, and there are two identical negative real characteristic roots:

[0020] Given a step change in the grid voltage phase angle, the phase angle change Δ i m The dynamic response in the time domain is:

[0021] like, x <1, it is an underdamped case, and there are two conjugate characteristic roots:

[0022] Given a step change in the grid voltage phase angle, the phase angle change Δ i m The dynamic response in the time domain is:

[0023] in, oh d is the oscillation frequency of the second-order system, β is the oscillation phase of the second-order system, expressed as: .

[0024] As a further improvement of the present invention, the instantaneous value of the current at the last moment of the steady state is calculated according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage, including: Changes in potential amplitude in grid-type energy storage and Δ U g ( s ) is related to the transfer function of the term, Δ U g ( s ) is a first-order system. U g exist t =0 + A step disturbance occurs at time , where t To express time, we have:

[0025] Potential change in grid-type energy storage ΔE m The dynamic response in the time domain is:

[0026] Determine the grid voltage before the fault and the potential amplitude and phase angle of the grid-type energy storage, which are recorded as U g0 = U g0 ∠ i g0 and E m0 = E m0 ∠ i m0 ,in, U g0 is the steady-state value of the grid-side voltage phasor before the fault, U g0 is the steady-state value of the grid-side voltage amplitude before the fault, i g0 is the steady-state value of the grid-side voltage phase before the fault; E m0 is the steady-state value of the potential phasor in the grid-type energy storage before the fault, U m0 is the steady-state value of the potential amplitude in the grid-type energy storage before the fault, i m0 is the steady-state value of the potential phase in the grid-type energy storage before the fault; the steady-state value of the line current phasor before the fault is I m0 , calculated by the following formula:

[0027] in, I m0 Indicates the steady-state value of the line current amplitude before the fault; i 0 is the steady-state value of the line current phase before the fault. I m0 Converted into the time domain equation, we have

[0028] remember t =0 + The instantaneous value of the line current at time I m0_end , t =0 - The instantaneous value of the line current at time t =0 + The instantaneous values ​​of the line currents at the same time.

[0029] As a further improvement of the present invention, the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage is calculated according to the damping state of the second-order system generating the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes, including: When a fault occurs, t =0 + The grid voltage amplitude and phase angle at the moment are given by U g0 = U g0 ∠ i g0 Jump to U g1 = U g1 ∠ i g1 , Δ U g = U g0 - U g1 , Δ i g = i g0 - i g1 ;in, U g1 is the steady-state value of the grid-side voltage phasor after the fault, U g1 is the steady-state value of the grid-side voltage amplitude after the fault, i g1 is the steady-state value of the grid-side voltage phase after the fault; the damping characteristics of the second-order system are determined based on the grid-type energy storage operation parameters. U g With Δ i g Calculate Δ i m ( t );and according to the change of potential in the grid-type energy storage Δ E m Dynamic response calculation in time domain Δ E m ( t ); Potential change in grid-type energy storage Δ E m The dynamic response in the time domain is: .

[0030] As a further improvement of the present invention, the method of solving the grid-type energy storage fault current expression based on the dynamic response of the internal potential amplitude and phase angle and combining the instantaneous value of the current includes: According to the transient AC component of the current i m_ac ( t )calculate t =0 + Initial value of time I m1_start ; Based on the principle that the inductor current cannot change suddenly before and after the fault occurs, the transient AC component of the current after the fault is solved i m_dc ( t ); Transient AC component i m_ac ( t ) and transient DC components i m_dc ( t ) and then get the grid-type energy storage fault current expression i m ( t ).

[0031] As a further improvement of the present invention, the dynamic response of the internal potential amplitude and phase angle, combined with the instantaneous value of the current, is used to solve the grid-type energy storage fault current expression, which specifically includes: Fault current includes transient AC component i m_ac ( t ) and transient DC components i m_dc ( t ), where the transient AC component of the current after the fault is solved based on the obtained Δ i m ( t ) and Δ E m ( t ) The expressions of the internal potential of the grid-type energy storage and the grid-side voltage after the fault are obtained:

[0032]

[0033]

[0034] in, e m1 ( t ), u g1 ( t ) represent the expressions of the internal potential of the grid-type energy storage and the grid voltage in the time domain respectively; the transient AC component of the current after the fault is obtained as:

[0035] After the failure t =0 + The initial value of the transient AC component of the current is I m1_start Based on the principle that the inductor current cannot change suddenly before and after the fault occurs, the transient AC component of the current after the fault is solved.

[0036] in, t is the time constant; thus the complete grid-type energy storage fault current expression is obtained through the following formula: .

[0037] In a second aspect, the present invention provides a grid-type energy storage fault current calculation system, comprising: A grid-side equivalent impedance calculation module is used to obtain grid strength data of grid-connected points of grid-connected energy storage based on a grid-connected energy storage fault current transient model, and calculate the grid-side equivalent impedance based on the grid strength data of grid-connected points of grid-connected energy storage; The damping state analysis module is used to obtain the key parameters of the grid-type energy storage and analyze the damping state of the second-order system that currently generates the phase angle variation based on the key parameters of the grid-type energy storage and the grid-side equivalent impedance; The current instantaneous value calculation module is used to calculate the current instantaneous value at the last moment of the steady state according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage; The dynamic response calculation module is used to calculate the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage according to the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes; The current expression solving module is used to solve the grid-type energy storage fault current expression according to the dynamic response of the internal potential amplitude and phase angle combined with the instantaneous value of the current.

[0038] In a third aspect, the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the method for calculating the grid-type energy storage fault current is implemented when the processor executes the computer program.

[0039] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the grid-type energy storage fault current calculation method is implemented.

[0040] In a fifth aspect, the present invention provides a computer program product, which includes computer instructions, and the computer instructions instruct a computer to execute the grid-type energy storage fault current calculation method.

[0041] The beneficial effects of the present invention compared with the prior art are as follows: The present invention comprehensively considers the potential amplitude and phase angle change Δ of the grid-type energy storage after the fault. E m , Δ i m Based on the dynamic characteristics of the VSG strategy, a transient model for fault current analysis suitable for VSG grid-type energy storage is established, and the VSG strategy includes virtual inertia. J , Virtual Damping D , reactive power coefficient K Q A fault current calculation method is proposed based on multiple key parameters such as the above. This method can provide guidance for the overload control design, parameter selection and device selection of grid-type energy storage, and can also provide a reference for grid operators, dispatching departments and other departments in the preliminary data collection for short-circuit current calculation of grid-type energy storage power stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 The equivalent circuit diagram of the present invention for calculating the grid-type energy storage fault current; Figure 2 The active power and reactive power control model diagram for calculating the grid-type energy storage fault current of the present invention is shown; Figure 3 It is a flow chart of the method for calculating fault current of grid-type energy storage according to the present invention; Figure 4 The comparison results of the potential amplitude and phase angle dynamic response of the grid-type energy storage obtained by the present invention through calculation and simulation; Figure 5 The figure is a comparison result between the instantaneous value of the three-phase fault current of the grid-type energy storage obtained by calculation and the simulation result. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0045] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0046] The invention relates to the fields of grid-type energy storage, virtual synchronous generator and fault current.

[0047] The present invention discloses a method for calculating fault current of grid-type energy storage taking into account sudden changes in amplitude and phase angle. Based on the transient model of virtual synchronous generator (VSG) control, a method for calculating fault current of grid-type energy storage taking into account sudden changes in amplitude and phase angle is established. U g ) and phase angle perturbation (Δ i g ) of reactive power and active power reference signal change (Δ Q mref , Δ P mref ) to the potential amplitude change and phase angle change (Δ E m , Δ i m ) transfer function model is established to make it suitable for fault current analysis of VSG strategy grid-type energy storage; based on the established transient model, the dynamic changes of grid-side and machine-side voltage amplitude and phase angle are considered through the principle that line inductance current cannot change suddenly, and a calculation method for three-phase fault current is further proposed.

[0048] To this end, an embodiment of the present invention provides a method for calculating a grid-type energy storage fault current, comprising the following steps: S101, obtaining grid strength data of a grid-connected point of a grid-connected energy storage based on a grid-connected energy storage fault current transient model, and calculating a grid-side equivalent impedance based on the grid strength data of a grid-connected point of a grid-connected energy storage; S102, obtaining key parameters of the grid-forming energy storage, and analyzing the damping state of the second-order system that currently generates the phase angle variation based on the key parameters of the grid-forming energy storage and the grid-side equivalent impedance; S103, calculating the instantaneous value of the current at the last moment of the steady state according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage; S104, calculating the dynamic response of the internal potential amplitude and phase angle of the grid-forming energy storage according to the damping state of the second-order system generating the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes; S105, according to the dynamic response of the internal potential amplitude and phase angle, combined with the instantaneous value of the current, the expression of the fault current of the grid-type energy storage is solved.

[0049] The core of the grid-type energy storage fault current calculation method of the present invention is to construct a transient model that fully considers the dynamic changes of the internal potential amplitude and phase angle, and calculate the fault current through this model. The specific principle analysis is as follows: Grid strength and grid-side equivalent impedance: In step S101, the grid strength data of the grid connection point is first obtained through the grid-connected energy storage fault current transient model, and then the grid-side equivalent impedance is calculated. This step is the basis for understanding the impact of the grid on grid-connected energy storage, because the strength of the grid will directly affect the dynamic response of the energy storage system.

[0050] Key parameter and damping state analysis: In step S102, the key parameters of the grid-type energy storage (such as virtual inertia J, virtual damping D, reactive coefficient KQ, etc.) are obtained, and the damping state of the second-order system that currently generates the phase angle variation is analyzed. These parameters and damping state directly determine the response speed and stability of the energy storage system to grid disturbances.

[0051] Transition from steady state to fault moment: In step S103, the initial internal potential amplitude and phase angle of the energy storage system during the steady state are used to calculate the instantaneous current value at the last moment of the steady state. This is to determine the state of the energy storage system before the fault occurs and provide a reference for the subsequent calculation of the fault current.

[0052] Dynamic response of internal potential amplitude and phase angle: In step S104, the dynamic response of internal potential amplitude and phase angle is calculated based on the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes. This is the core of the entire method. Through this step, the dynamic behavior of the energy storage system after a fault occurs can be accurately simulated.

[0053] Solution of fault current expression: In step S105, based on the dynamic response of internal potential amplitude and phase angle, the fault current expression of grid-connected energy storage is solved. This step is the output of the method and is also a key indicator for evaluating the ability of energy storage systems to respond to grid faults.

[0054] The present invention is applicable to the fault current estimation of grid-type energy storage systems / energy storage power stations. Through the present invention, it is helpful to reasonably select the current tolerance of grid-type energy storage system equipment and components; reasonably design the parameters of the control loop of the grid-type energy storage system; and provide a reference for power grid operators and dispatchers to evaluate the fault current risk of grid-type energy storage.

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] Firstly, a transient model of fault current of grid-type energy storage is constructed; The transient model used for fault current analysis of grid-connected energy storage is divided into two parts. One is the equivalent circuit diagram of grid-connected energy storage connected to the power grid, such as Figure 1 As shown in the figure. Among them, the grid voltage phasor is recorded as U g = U g ∠ i g , the grid-side equivalent impedance is expressed as Z g = R g +j X g ; The potential phasor in the grid-type energy storage is expressed as E m = E m ∠ i m , the machine side impedance is expressed as Z m = R m +j X m , usually generated by LC filters, etc. The equivalent impedance on the machine side is usually much smaller than the grid side impedance and can be ignored in the calculation; at the same time, R g Much smaller than X g Therefore, the machine side impedance is ignored in the subsequent calculation of the present invention. Z m , while only taking Z g =j X g .

[0057] Specifically, the grid voltage phasor is recorded as U g = U g ∠ i g ,in, U gis the grid voltage phasor, U g is the grid voltage amplitude, i g is the grid voltage phase; the grid-side equivalent impedance is expressed as Z g = R g +j X g ,in, Z g is the grid-side equivalent impedance, R g is the grid-side equivalent resistance, X g is the grid-side equivalent reactance, is an imaginary number; the potential phasor in the grid-type energy storage is expressed as E m = E m ∠ i m ,in, E m is the potential phasor in the grid-type energy storage, U m is the potential amplitude of the grid-type energy storage, i m is the potential phase in the grid-type energy storage; the machine-side impedance is expressed as Z m = R m +j X m ,in, Z m is the equivalent impedance on the machine side, R m is the equivalent resistance on the machine side, X m is the equivalent reactance on the generator side. Since the equivalent resistance on the grid side is usually much smaller than the equivalent reactance on the grid side, Z g =j X g .

[0058] Another part of the transient model for fault current analysis of grid-type energy storage is the internal potential amplitude and phase angle generation strategy of the grid-type energy storage, such as Figure 2 As shown. For VSG strategy grid-connected energy storage, its output complex power can be expressed as: (1) in, I m is the output current phasor of the grid-type energy storage, and the symbol “^” represents conjugation; Δ i mIt represents the phase change of the electric potential in the grid-type energy storage.

[0059] According to formula (1), the active power output of the grid-connected energy storage is P m , the reactive power is Q m , respectively expressed as: (2) For the convenience of analysis, equation (2) is linearized. Usually, the control link parameter design makes the potential amplitude and phase angle of the grid-type energy storage closely follow the change of the grid phase angle, that is, Δ E m ≈0,Δ i m ≈0, according to the following limit: (3) According to equations (3) and (4), the change in active power and reactive power Δ is obtained: P m , Δ Q m Respectively about Δ i m , Δ E mref , Δ U g The expression for (ignoring higher-order infinitesimals): (4) (5) in, E mref Indicates the potential amplitude command value in the grid-type energy storage; U g0 Indicates the steady-state value of the grid-side voltage amplitude; Δ i m , Δ E m , Δ U g They are respectively the phase change of the potential inside the grid-forming energy storage, the amplitude change of the potential inside the grid-forming energy storage, and the amplitude change of the voltage on the grid side; k p , m q , n q They are respectively the phase change gain coefficient, the grid-type energy storage internal potential amplitude change gain coefficient, and the grid-side voltage amplitude change gain coefficient. By combining equations (4) and (5) with Figure 2 Combined, we can get Δ i m , ΔE m The transfer functions of the change in active power command value, grid-side phase angle change, reactive power command value change, internal potential amplitude command value change, and grid-side voltage amplitude change are as follows: (6) (7) Among them, Δ i m , Δ E m The change in active power command value Δ P mref , grid side phase angle change Δ i g The change in reactive power command value Δ Q mref , the change of the internal potential amplitude command value Δ E mref , grid-side voltage amplitude change Δ U g The transfer function of oh 0 is the rated frequency of the power grid, J To construct the virtual inertia of network energy storage, D To construct a virtual damping network energy storage, k q is the reactive power coefficient of grid-type energy storage.

[0060] As an example, oh 0=100π, which is the rated frequency of the power grid.

[0061] The present invention focuses on the potential amplitude and phase angle changes in the grid-type energy storage caused by the grid-side disturbance, so only Δ i g ( s ) and Δ U g ( s ) item to Δ i m ( s ) and Δ E m ( s ) caused by.

[0062] The dynamic change of the internal potential phase angle when the grid voltage phase angle suddenly changes is described as follows: The change of the potential phase angle in the grid-type energy storage is related to Δ i g ( s ) term. Note that Δ i g ( s) is a second-order system, so it is transformed as follows: (8) in, oh c is the undamped natural oscillation angular frequency of the second-order system, x is the equivalent damping ratio of the second-order system, expressed as: (9) Focusing on the non-constant terms in equation (8), solving the differential equation shown requires the following x The specific value of is discussed in detail: x >1 (overdamped case), there are two negative real characteristic roots in equation (8), which are denoted as s 1,2 ,have: (10) At this time, the phase angle of the given grid voltage is a step change, and the phase angle change Δ i m The dynamic response in the time domain is: (11) ii) x =1 (critical damping case), equation (8) has two identical negative real characteristic roots: (12) At this time, the phase angle of the given grid voltage is a step change, and the phase angle change Δ i m The dynamic response in the time domain is: (13) iii) If, x <1, which is the underdamped case, which is the most common case of VSG strategy grid-type energy storage. At this time, equation (8) has two conjugate characteristic roots: (14) At this time, the phase angle of the given grid voltage is a step change, and the phase angle change Δ i m The dynamic response in the time domain is: (15) in, oh d is the oscillation frequency of the second-order system, β is the oscillation phase of the second-order system, expressed as: (16) When calculating the fault current, we should first consider the parameters involved. J , D Determine the damping characteristics of the second-order system and then solve Δ based on the equation i m Dynamic response.

[0063] The dynamic change of the internal potential amplitude when the grid voltage amplitude suddenly changes is described as follows: The change of the potential amplitude in the grid-type energy storage is related to Δ U g ( s ) term. Note that Δ U g ( s ) is a first-order system. U g exist t =0 + A step disturbance occurs at time , where t To express time, we have: (17) At this time, the change in potential Δ E m The dynamic response in the time domain is: (18) The method for calculating the fault current of the grid-type energy storage comprises the following steps: (1) Determine the grid voltage before the fault and the potential amplitude and phase angle of the grid-type energy storage, which are respectively expressed as U g0 = U g0 ∠ i g0 and E m0 = E m0 ∠ i m0 .

[0064] in, U g0 is the steady-state value of the grid-side voltage phasor before the fault, U g0 is the steady-state value of the grid-side voltage amplitude before the fault, i g0 is the steady-state value of the grid-side voltage phase before the fault; E m0 is the steady-state value of the potential phasor in the grid-type energy storage before the fault, U m0 is the steady-state value of the potential amplitude in the grid-type energy storage before the fault, im0 is the steady-state value of the potential phase in the grid-type energy storage before the fault; the steady-state value of the line current phasor before the fault is I m0 , can be calculated by the following formula: (19) in, I m0 Indicates the steady-state value of the line current amplitude before the fault; i 0 is the steady-state value of the line current phase before the fault. I m0 Converted into the time domain equation, we have (20) remember t =0 + The instantaneous value of the line current at time I m0_end , t =0 - The instantaneous value of the line current at time t =0 + The instantaneous values ​​of the line currents at the same time.

[0065] When a fault occurs, t =0 + The grid voltage amplitude and phase angle at the moment are given by U g0 = U g0 ∠ i g0 Jump to U g1 = U g1 ∠ i g1 , that is, Δ U g = U g0 - U g1 , Δ i g = i g0 - i g1 .in, U g1 is the steady-state value of the grid-side voltage phasor after the fault, U g1 is the steady-state value of the grid-side voltage amplitude after the fault, i g1 is the steady-state value of the grid-side voltage phase after the fault; according to formula (9), the damping characteristics of the second-order system are determined based on the grid-type energy storage operation parameters. Ug With Δ i g Calculate Δ i m ( t ) and calculate Δ according to formula (18) E m ( t ).

[0066] (2) Fault current calculation. Since the equivalent impedance on the grid side is inductive, and the inductive current cannot change suddenly before and after the fault occurs, the fault current contains transient AC components. i m_ac ( t ) (Phasor is expressed as I m_ac ), there is also a transient DC component i m_dc ( t ) (Phasor is expressed as I m_dc ). The transient AC component of the fault current is affected by the changes in the potential amplitude and phase angle within the grid-type energy storage.

[0067] To solve the transient AC component of the current after the fault, it is necessary to calculate the Δ i m ( t ) and Δ E m ( t ) Arrange the expressions of the internal potential of the grid-type energy storage and the grid-side voltage after the fault, and we have: (twenty one) (twenty two) (twenty three) in, e m1 ( t ), u g1 ( t ) represent the expressions of the internal potential of the grid-type energy storage and the grid voltage in the time domain. From this, the transient AC component of the current after the fault can be obtained as: (twenty four) After the fault ( t =0 + )The initial value of the transient AC component of the current is I m1_start Based on the principle that the inductor current cannot change suddenly before and after the fault occurs, the transient AC component of the current after the fault is solved. (25) in, t is the time constant. Therefore, the complete grid-type energy storage fault current expression can be obtained by the following formula: (26) In summary, the present invention arranges the grid-type energy storage fault current calculation according to the above short-circuit current calculation method, and the steps are as follows: Figure 3 As shown in the figure, the calculation process of grid-type energy storage fault current is as follows: i) Obtain the grid strength data of the grid-connected energy storage point through impedance scanning, historical data reading, etc., and calculate the grid-side equivalent impedance Z g = R g +j X g ; ii) Obtain key parameters of grid-connected energy storage, including virtual inertia, by collecting manufacturer converter data and reading on-site data J , Virtual Damping D , reactive power coefficient K Q ; iii) Based on key parameters, analyze the current generation Δ i m What is the damping state of the second-order system? iv) Input the initial internal potential amplitude and phase angle during the steady-state period of the grid-type energy storage, and calculate the instantaneous current value at the last moment of the steady-state I m_end ; v) Enter the desired t =0 + The voltage amplitude step change Δ calculated at the moment U g and phase angle jump value Δ i g ; vi) Generate Δ i m The second-order system is in a damping state and formula (18) to calculate the dynamic response Δ of the potential amplitude and phase angle in the grid-type energy storage. E m ( t ), Δ i m ( t ); vii) Substitute the internal potential amplitude and phase angle dynamic response into equations (23) and (24) to solve the transient AC component of the current after the fault i m_ac ( t ); viii) According to the transient AC component of the current i m_ac ( t )calculate t =0 + The initial value of the time is recorded as I m1_start ; ix) Solve the transient AC component of the current after the fault according to equation (25): i m_dc ( t ); x) According to formula (26), the fault current expression of grid-type energy storage is obtained: i m ( t ).

[0068] In order to prove the effectiveness of the proposed method for calculating fault current of grid-type energy storage taking into account sudden changes in amplitude and phase angle, a comparative analysis of theoretical calculation and simulation data was carried out. Figure 1 The circuit shown in the figure is constructed, and the grid-type energy storage adopts the VSG strategy, and does not adopt the fault current suppression strategies such as inner loop control, virtual impedance, and voltage limiting. The grid-type energy storage fault current calculation process described in 4.3 is operated as follows: 1) Take the grid strength SCR = 4.0, the grid voltage level 35 kV, X / R = 10, the grid side equivalent impedance under this parameter is Z g =3.0625+j30.625 Ω, the grid-side nominal voltage and the rated value of the potential inside the grid-type energy storage are both 1∠0°; 2) The control parameters of the grid-type energy storage are: virtual inertia J =20, virtual damping D =1000, reactive power coefficient K Q =0.01; 3) Gain coefficient under this parameter k p , m q , n q They are k p =4.00×10 7 , m q = n q =1.40×10 3 . x =0.3134<1, the second-order system is underdamped; 4) The initial internal potential amplitude and phase angle during the steady-state period of the grid-type energy storage are set to the rated value, 1∠0°, that is, t =0 - Initial line current at time I m_end is 0; 5) In order to fully verify the calculation effect of the fault current of the grid-connected energy storage under the sudden change of the grid voltage amplitude and phase angle, three voltage amplitude step changes Δ U g and phase angle jump value Δ i g The working conditions are: i) Condition 1: Δ U g =-0.3 U g0 , Δ i g =0; ii) Condition 2: Δ U g =0,Δ i g =-5°; iii) Condition 3: Δ U g =-0.4 U g0 , Δ i g =-10°.

[0069] 6) According to step vi) in 4.3, calculate the potential amplitude and phase angle Δ of the grid-type energy storage i m The dynamic response of E m ( t ), Δ i m ( t ), the comparison between the calculation results of the three working conditions and the simulation data is as follows Figure 4 As shown; 7) According to steps vii)~x) in 4.3, combined with the instantaneous value of current, calculate the fault current expression of the grid-type energy storage: i m ( t ), the comparison between the calculation results of the three working conditions and the simulation data is as follows Figure 5 shown.

[0070] The theoretical calculation and simulation results are analyzed, the maximum value of the three-phase fault current is used as the assessment basis, and the simulation results are used as the benchmark value for deviation calculation to verify the accuracy of the calculation method. The maximum values ​​of the three-phase fault current under the three working conditions are shown in the table below, and the deviation is no more than 15%. The reason for the deviation is that the voltage amplitude step and phase angle jump will affect the active and reactive power, while the active and reactive power links are ignored in the calculation process. Since the disturbance of the active and reactive power links is small, the calculation method is still of reference value and can be compensated by reasonably setting the fault current margin.

[0071]

[0072] Through the grid-type energy storage fault current small signal model and calculation method designed in this scheme, the grid-type energy storage short-circuit current under any voltage drop / rise and phase angle mutation can be calculated. After theoretical analysis and simulation comparison, the error does not exceed 15%. This method can provide a reference for the setting of energy storage and line protection parameters, the design of grid-type energy storage overload operation control parameters, and the selection of energy storage converter components.

[0073] The second object of the present invention is to provide a grid-type energy storage fault current calculation system, comprising: A grid-side equivalent impedance calculation module is used to obtain grid strength data of grid-connected points of grid-connected energy storage based on a grid-connected energy storage fault current transient model, and calculate the grid-side equivalent impedance based on the grid strength data of grid-connected points of grid-connected energy storage; The damping state analysis module is used to obtain the key parameters of the grid-type energy storage and analyze the damping state of the second-order system that currently generates the phase angle variation based on the key parameters of the grid-type energy storage and the grid-side equivalent impedance; The current instantaneous value calculation module is used to calculate the current instantaneous value at the last moment of the steady state according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage; The dynamic response calculation module is used to calculate the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage according to the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes; The current expression solving module is used to solve the grid-type energy storage fault current expression according to the dynamic response of the internal potential amplitude and phase angle combined with the instantaneous value of the current.

[0074] The system is based on the above-mentioned grid-type energy storage fault current calculation method. Therefore, the advantages of the present invention are as follows: Comprehensiveness and accuracy: This method comprehensively considers the dynamic changes of the potential amplitude and phase angle in the grid-type energy storage after the fault moment, and constructs a more comprehensive and accurate transient model. This helps to more accurately simulate the behavior of the energy storage system under grid faults and improve the accuracy of fault current calculation.

[0075] Parametric design: The method introduces key parameters such as virtual inertia, virtual damping, and reactive power coefficient, making the calculation method more flexible and adjustable. By adjusting these parameters, the dynamic response characteristics of the energy storage system under different parameter configurations can be studied, providing guidance for the design and optimization of the energy storage system.

[0076] Practical application value: This method can not only provide guidance for the overload control design, parameter selection and device selection of grid-type energy storage, but also provide a reference for the preliminary data collection of grid operators, dispatching departments, etc. for the short-circuit current calculation of grid-type energy storage power stations. This will help improve the safety and stability of the power grid and promote the widespread application of grid-type energy storage technology.

[0077] This method theoretically breaks through the limitations of traditional fault current calculation methods and proposes a new idea to consider the dynamic changes of internal potential amplitude and phase angle. This innovation brings a new perspective and methodology to the field of grid-type energy storage fault current calculation.

[0078] The third object of the embodiment of the present invention is to provide an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the grid-type energy storage fault current calculation method when executing the computer program. It also includes a communication interface and a bus.

[0079] A fourth objective of an embodiment of the present invention is to provide a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the grid-type energy storage fault current calculation method is implemented.

[0080] A fifth objective of an embodiment of the present invention is to provide a computer program product, wherein the computer program product comprises computer instructions, wherein the computer instructions instruct a computer to execute the grid-type energy storage fault current calculation method.

[0081] 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 one A process or multiple processes and / or boxes Figure one A function specified in one or more boxes.

[0082] 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 oneA process or multiple processes and / or boxes Figure one The steps for the functions specified in one or more boxes.

[0083] The present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, readable storage media, optical storage, etc.) containing computer-usable program codes.

[0084] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce 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 one A process or multiple processes and / or boxes Figure one A device that provides the functions specified in a block or multiple blocks.

[0085] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating fault current of grid-type energy storage, characterized in that: include: Based on the transient model of grid-type energy storage fault current, the grid strength data of the grid-type energy storage grid connection point is obtained, and the grid-side equivalent impedance is calculated based on the grid strength data of the grid-type energy storage grid connection point; Obtain key parameters of grid-type energy storage, and analyze the damping state of the second-order system that currently generates phase angle variation based on the key parameters of grid-type energy storage and the grid-side equivalent impedance; According to the initial internal potential amplitude and phase angle during the steady-state period of the grid-type energy storage, the instantaneous value of the current at the last moment of the steady-state is calculated; According to the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes, the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage is calculated; According to the dynamic response of internal potential amplitude and phase angle and combined with the instantaneous value of current, the fault current expression of grid-type energy storage is solved.

2. A method for calculating fault current of a grid-type energy storage according to claim 1, characterized in that: The grid-type energy storage fault current transient model includes: an equivalent circuit of the grid-type energy storage connected to the power grid and a strategy for generating the internal potential amplitude and phase angle of the grid-type energy storage; In the grid-connected equivalent circuit of grid energy storage, the grid voltage phasor is recorded as U g = U g ∠ θ g ,in, U g is the grid voltage phasor, U g is the grid voltage amplitude, θ g is the grid voltage phase; The grid-side equivalent impedance is expressed as Z g = R g +j X g ,in, Z g is the grid-side equivalent impedance, R g is the grid-side equivalent resistance, X g is the grid-side equivalent reactance, is an imaginary number; The potential phasor in the grid-type energy storage is expressed as E m = E m ∠ θ m ,in, E m is the potential phasor in the grid-type energy storage, U m is the potential amplitude of the grid-type energy storage, θ m is the potential phase inside the grid-type energy storage; The machine side impedance is expressed as Z m = R m +j X m ,in, Z m is the equivalent impedance on the machine side, R m is the equivalent resistance on the machine side, X m is the equivalent reactance on the generator side. Since the equivalent resistance on the grid side is usually much smaller than the equivalent reactance on the grid side, Z g =j X g ; In the internal potential amplitude and phase angle generation strategy of grid-type energy storage, the output complex power of VSG strategy grid-type energy storage is expressed as: in, I m is the output current phasor of the grid-type energy storage, and the symbol "^" represents conjugation; Δ θ m Indicates the phase change of the potential in the grid-type energy storage; The active power output of the grid-connected energy storage is P m , the reactive power is Q m , respectively expressed as: The active power change rate is Δ P m , the reactive power change is Δ Q m , the expression is as follows: in, E mref Indicates the potential amplitude command value in the grid-type energy storage; U g0 Indicates the steady-state value of the grid-side voltage amplitude; Δ θ m , Δ E m , Δ U g They are respectively the phase change of the potential inside the grid-forming energy storage, the amplitude change of the potential inside the grid-forming energy storage, and the amplitude change of the voltage on the grid side; k p , m q , n q They are phase change gain coefficient, grid-type energy storage internal potential amplitude change gain coefficient, grid-side voltage amplitude change gain coefficient respectively; Δ θ m , Δ E m The change in active power command value Δ P mref , grid side phase angle change Δ θ g The change in reactive power command value Δ Q mref , the change of the internal potential amplitude command value Δ E mref , grid-side voltage amplitude change Δ U g The transfer function is as follows: in, ω 0 is the rated frequency of the power grid, J To construct the virtual inertia of network energy storage, D To construct a virtual damping network energy storage, k q is the reactive power coefficient of grid-type energy storage.

3. A method for calculating grid-type energy storage fault current according to claim 1, characterized in that: The key parameters of the grid-type energy storage include virtual inertia J , Virtual Damping D , reactive power coefficient k q .

4. A method for calculating fault current of a grid-type energy storage according to claim 3, characterized in that: The damping state of the second-order system currently generating the phase angle variation is analyzed based on the key parameters of the grid-type energy storage and the grid-side equivalent impedance, including: First, the dynamic change trend of the internal potential phase angle when the grid voltage phase angle changes suddenly is obtained, including: The change of potential phase angle in grid-type energy storage and Δ θ g ( s ) is related to the transfer function of the term, Δ θ g ( s ) is a second-order system, which is transformed as follows: in, ω c is the undamped natural oscillation angular frequency of the second-order system, ξ is the equivalent damping ratio of the second-order system, expressed as: When calculating the fault current, first consider the parameters involved. J , D Determine the damping characteristics of the second-order system and then solve Δ based on the equation θ m The dynamic response of ξ The specific values ​​are as follows: like, ξ >1, it is an overdamped case, there are two negative real characteristic roots, the two characteristic roots are recorded as s 1,2 ,have: Given a step change in the grid voltage phase angle, the phase angle change Δ θ m The dynamic response in the time domain is: like, ξ =1, which is the critical damping case, and there are two identical negative real characteristic roots: Given a step change in the grid voltage phase angle, the phase angle change Δ θ m The dynamic response in the time domain is: like, ξ <1, it is an underdamped case, and there are two conjugate characteristic roots: Given a step change in the grid voltage phase angle, the phase angle change Δ θ m The dynamic response in the time domain is: in, ω d is the oscillation frequency of the second-order system, β is the oscillation phase of the second-order system, expressed as: 。 5. A method for calculating fault current of grid-type energy storage according to claim 1, characterized in that: The instantaneous value of the current at the last moment of the steady state is calculated according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage, including: Changes in potential amplitude in grid-type energy storage and Δ U g ( s ) is related to the transfer function of the term, Δ U g ( s ) is a first-order system. U g exist t =0 + A step disturbance occurs at time , where t To express time, we have: Potential change in grid-type energy storage Δ E m The dynamic response in the time domain is: Determine the grid voltage before the fault and the potential amplitude and phase angle of the grid-type energy storage, which are recorded as U g0 = U g0 ∠ θ g0 and E m0 = E m0 ∠ θ m0 ,in, U g0 is the steady-state value of the grid-side voltage phasor before the fault, U g0 is the steady-state value of the grid-side voltage amplitude before the fault, θ g0 is the steady-state value of the grid-side voltage phase before the fault; E m0 is the steady-state value of the potential phasor in the grid-type energy storage before the fault, U m0 is the steady-state value of the potential amplitude in the grid-type energy storage before the fault, θ m0 is the steady-state value of the potential phase in the grid-type energy storage before the fault; the steady-state value of the line current phasor before the fault is I m0 , calculated by the following formula: in, I m0 Indicates the steady-state value of the line current amplitude before the fault; θ 0 is the steady-state value of the line current phase before the fault. I m0 Converted into time domain equation, we have remember t =0 + The instantaneous value of the line current at time I m0_end , t =0 - The instantaneous value of the line current at time t =0 + The instantaneous values ​​of the line currents at the same time.

6. A method for calculating grid-type energy storage fault current according to claim 1, characterized in that: The method calculates the dynamic response of the internal potential amplitude and the phase angle of the grid-forming energy storage according to the damping state of the second-order system generating the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes, including: When a fault occurs, t =0 + The grid voltage amplitude and phase angle at the moment are given by U g0 = U g0 ∠ θ g0 Jump to U g1 = U g1 ∠ θ g1 , Δ U g = U g0 - U g1 , Δ θ g = θ g0 - θ g1 ;in, U g1 is the steady-state value of the grid-side voltage phasor after the fault, U g1 is the steady-state value of the grid-side voltage amplitude after the fault, θ g1 is the steady-state value of the grid-side voltage phase after the fault; the damping characteristics of the second-order system are determined based on the grid-type energy storage operation parameters. U g With Δ θ g Calculate Δ θ m ( t );and according to the change of potential in the grid-type energy storage Δ E m Dynamic response calculation in time domain Δ E m ( t ); Potential change in grid-type energy storage Δ E m The dynamic response in the time domain is: 。 7. A method for calculating fault current of grid-type energy storage according to claim 1, characterized in that: The method of solving the grid-type energy storage fault current expression based on the dynamic response of the internal potential amplitude and phase angle and combining the instantaneous value of the current includes: According to the transient AC component of the current i m_ac ( t )calculate t =0 + Initial value of time I m1_start ; Based on the principle that the inductor current cannot change suddenly before and after the fault occurs, the transient AC component of the current after the fault is solved i m_dc ( t ); Transient AC component i m_ac ( t ) and transient DC components i m_dc ( t ) and then get the grid-type energy storage fault current expression i m ( t ).

8. A method for calculating fault current of a grid-type energy storage according to claim 1 or 7, characterized in that: The method of solving the grid-type energy storage fault current expression based on the dynamic response of the internal potential amplitude and phase angle and combining the instantaneous value of the current specifically includes: Fault current includes transient AC component i m_ac ( t ) and transient DC components i m_dc ( t ), where the transient AC component of the current after the fault is solved based on the obtained Δ θ m ( t ) and Δ E m ( t ) The expressions of the internal potential of the grid-type energy storage and the grid-side voltage after the fault are obtained: in, e m1 ( t ), u g1 ( t ) represent the expressions of the internal potential of the grid-type energy storage and the grid voltage in the time domain respectively; the transient AC component of the current after the fault is obtained as: After the failure t =0 + The initial value of the transient AC component of the current is I m1_start Based on the principle that the inductor current cannot change suddenly before and after the fault occurs, the transient AC component of the current after the fault is solved. in, τ is the time constant; thus the complete grid-type energy storage fault current expression is obtained through the following formula: 。 9. A grid-type energy storage fault current calculation system, characterized in that: include: A grid-side equivalent impedance calculation module is used to obtain grid strength data of grid-connected points of grid-connected energy storage based on a grid-connected energy storage fault current transient model, and calculate the grid-side equivalent impedance based on the grid strength data of grid-connected points of grid-connected energy storage; The damping state analysis module is used to obtain the key parameters of the grid-type energy storage and analyze the damping state of the second-order system that currently generates the phase angle variation based on the key parameters of the grid-type energy storage and the grid-side equivalent impedance; The current instantaneous value calculation module is used to calculate the current instantaneous value at the last moment of the steady state according to the initial internal potential amplitude and phase angle during the steady state of the grid-type energy storage; A dynamic response calculation module is used to calculate the dynamic response of the internal potential amplitude and phase angle of the grid-type energy storage according to the damping state of the second-order system that generates the phase angle variation and the dynamic change relationship of the internal potential amplitude when the grid voltage amplitude suddenly changes; The current expression solving module is used to solve the grid-type energy storage fault current expression according to the dynamic response of the internal potential amplitude and phase angle combined with the instantaneous value of the current.

10. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the grid-type energy storage fault current calculation method as claimed in any one of claims 1 to 8 when executing the computer program.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for calculating the grid-type energy storage fault current according to any one of claims 1 to 8 is implemented.

12. A computer program product, comprising computer instructions, characterized in that: The computer instructions instruct the computer to execute the grid-type energy storage fault current calculation method described in any one of claims 1-8.

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