Graded current-limiting control method, device and equipment for network construction type energy storage converter

Abstract

The invention provides a hierarchical current-limiting control method, device and equipment for a network construction type energy storage converter, and belongs to the technical field of energy storage converter control. The method comprises the following steps: acquiring output voltage, current and battery cluster temperature; calculating direct-axis and quadrature-axis components and active / reactive power based on the voltage / current; determining the maximum overload current of the converter by combining the maximum temperature and the current; a virtual synchronous machine strategy is adopted, and equivalent voltage components are generated through the voltage components and the power parameters; virtual voltage drop is calculated through a virtual impedance strategy; deducting the equivalent component to obtain a voltage reference value; generating a current reference value through PI control; if the limit value is exceeded, carrying out coordinate transformation constraint according to the maximum overload current; finally, the limited current reference value is input into a current inner loop for closed-loop control, and it is ensured that the output current does not exceed the limit. Through a three-stage cooperation mechanism of overload verification of temperature sensing, virtual impedance active current limiting and saturation limit value forced constraint, graded current limiting protection of the energy storage system under different working conditions is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage converter control, and particularly relates to a hierarchical current limiting control method for a network-forming energy storage converter, a hierarchical current limiting control device for a network-forming energy storage converter, and an electronic device. Background Art

[0002] With the high proportion of new energy connected to the power system, the network-forming energy storage has become the core equipment for maintaining the stability of the power grid due to its characteristics such as independent voltage regulation and inertia simulation. However, the power grids in high-penetration new energy areas show the characteristics of "double highs" (high proportion of new energy and high proportion of power electronic devices), resulting in insufficient short-circuit capacity and weakened inertia response ability of the system. During power grid faults, new energy units are extremely prone to cascaded disconnection from the grid. According to statistics, in recent years, the proportion of new energy power stations with a short-circuit ratio lower than 2.0 has exceeded 30%, and the voltage drop amplitude during their faults has increased by 40%-60% compared with conventional power grids, leading to multiple energy storage battery thermal runaway accidents caused by the failure of the overcurrent protection of the network-forming energy storage system, seriously threatening the safe operation of the power grid.

[0003] Currently, the current limiting technologies for energy storage systems mainly include the following two methods: (1) By dynamically adjusting the impedance parameters (K = 0.8 to 1.2, ), the fault current is limited within the tolerance range of the converter (such as 3 times the rated current for 10 s). Further, when the voltage drops to 0.3 p.u., the power reference value is adjusted (ΔP = 0.2 - 0.5 p.u., ΔQ = 0.3 - 0.6 p.u.) to control the current tracking error within 5%; (2) Oversizing the coefficient by 1.2 - 1.5 times or using N + 1 redundant PCSs to extend the 3 - times current support time to 15 s. At the same time, the fuse (operating < 2 ms) cooperates with the IGBT desaturation protection to suppress the transient overcurrent (di / dt < 500 A / μs).

[0004] However, the existing current limiting technologies for energy storage systems have the following problems: (1) When the network-forming energy storage converter forcibly switches the current limiting mode during a power grid fault, it will lose the power grid support ability and is prone to cause system instability; (2) The multi-cluster parallel batteries in the energy storage system may trigger thermal runaway due to uneven temperature, posing a safety risk; (3) The power grid transient overcurrent needs to take into account both instantaneous suppression and long-term current limiting protection, and it is difficult for traditional methods to adapt; (4) When the power device of the converter is rapidly charged and discharged with a large current, it may be damaged due to instantaneous overcurrent. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a hierarchical current limiting control method, device, and equipment for a network-forming energy storage converter to solve the above problems.

[0006] To achieve the above purpose, the embodiments of the present invention provide a hierarchical current limiting control method for a network-forming energy storage converter, including:

[0007] S100, obtain the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters;

[0008] S200, based on the output voltage of the energy storage system, determine the direct-axis component and quadrature-axis component of the output voltage of the energy storage system, and based on the output current of the energy storage system, determine the direct-axis component and quadrature-axis component of the output current of the energy storage system; and based on the output voltage and output current of the energy storage system, determine the active power, reactive power, and AC voltage amplitude of the energy storage system;

[0009] S300; based on the maximum temperature and output current of multiple battery clusters of the energy storage system, determine the maximum overload current of the grid-forming energy storage converter;

[0010] S400, based on the direct-axis component of the output voltage, quadrature-axis component of the output voltage, active power, reactive power, and AC voltage amplitude of the energy storage system, according to the virtual synchronous machine control strategy, obtain the equivalent direct-axis component and equivalent quadrature-axis component of the output voltage of the energy storage system;

[0011] S500, based on the maximum overload current of the grid-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system, according to the virtual impedance control strategy, obtain the direct-axis virtual voltage drop and quadrature-axis virtual voltage drop of the energy storage system;

[0012] S600, subtract the direct-axis virtual voltage drop of the energy storage system from the equivalent direct-axis component of the output voltage of the energy storage system to obtain the reference value of the direct-axis component of the output voltage of the energy storage system, and subtract the quadrature-axis virtual voltage drop of the energy storage system from the equivalent quadrature-axis component of the output voltage of the energy storage system to obtain the reference value of the quadrature-axis component of the output voltage of the energy storage system;

[0013] S700, based on the reference value of the direct-axis component of the output voltage, reference value of the quadrature-axis component of the output voltage, direct-axis component of the output voltage, and quadrature-axis component of the output voltage of the energy storage system, after PI control, obtain the reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system, and based on the reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system, obtain the reference value of the output current of the energy storage system;

[0014] S800, if the reference value of the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter, then based on the maximum overload current of the grid-forming energy storage converter and the reference value of the direct-axis component of the output current, reference value of the quadrature-axis component of the output current, and reference value of the output current of the energy storage system, obtain the limit value of the direct-axis component of the output current and the limit value of the quadrature-axis component of the output current of the energy storage system;

[0015] S900, restrict the reference value of the direct-axis component of the output current of the energy storage system not to exceed the limit value of the direct-axis component of the output current of the energy storage system, and restrict the reference value of the quadrature-axis component of the output current of the energy storage system not to exceed the limit value of the quadrature-axis component of the output current of the energy storage system, to obtain the finally generated reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system, and use the finally generated reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system as the closed-loop control instructions of the current inner loop. Through the current inner loop and the modulation module, control the output current of the energy storage system not to exceed the maximum overload current of the grid-forming energy storage converter.

[0016] Optionally, step S300 includes:

[0017] S310, delimit the current limit level based on the maximum value of the temperature of the battery cluster within the preset temperature range, and determine the current current limit level of the grid-forming energy storage converter;

[0018] S320, determine whether the current current limit level of the grid-forming energy storage converter is in an available state;

[0019] S330, if so, based on the current current limit level of the grid-forming energy storage converter, multiple preset overload capabilities, and multiple preset re-availability interval durations, determine the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the grid-forming energy storage converter at the current current limit level;

[0020] S340, if the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter at the current current limit level, start overcurrent timing until the overcurrent timing duration is greater than the maximum continuous overcurrent duration of the grid-forming energy storage converter at the current current limit level, increment the current current limit level of the grid-forming energy storage converter, mark the current current limit level of the grid-forming energy storage converter as unavailable, return to step S330, and at the same time start cooling timing until the cooling timing duration is greater than the re-availability interval duration of the grid-forming energy storage converter at the current current limit level, mark the current current limit level of the grid-forming energy storage converter as available, and return to step S310;

[0021] S350, if not, increment the current current limit level of the grid-forming energy storage converter and return to step S320.

[0022] Optionally, step S310 includes:

[0023] Based on the preset temperature range and multiple preset temperature variables, delimit multiple temperature ranges of the battery cluster; where each temperature range corresponds to a different current limit level;

[0024] By determining the temperature range of the battery cluster to which the maximum value of the battery cluster temperature belongs, the current current limit level of the grid-forming energy storage converter is determined.

[0025] Optionally, the multiple preset temperature variables include: a first preset temperature variable, a second preset temperature variable, a third preset temperature variable, and a fourth preset temperature variable; the first preset temperature variable < the second preset temperature variable < the third preset temperature variable < the fourth preset temperature variable;

[0026] Based on the preset temperature range and the multiple preset temperature variables, multiple temperature ranges of the battery cluster are delimited, including:

[0027] Taking the minimum value of the preset temperature range as the left endpoint of the range and the sum value of the minimum value of the preset temperature range and the first preset temperature variable as the right endpoint of the range, a first temperature range of the battery cluster is constructed, and the current limit level of the first temperature range of the battery cluster is determined as the first current limit level;

[0028] Taking the sum value of the minimum value of the preset temperature range and the first preset temperature variable as the left endpoint of the range and the difference value between the maximum value of the preset temperature range and the first preset temperature variable as the right endpoint of the range, a second temperature range of the battery cluster is constructed, and the current limit level of the second temperature range of the battery cluster is determined as the second current limit level;

[0029] Taking the difference value between the maximum value of the preset temperature range and the first preset temperature variable as the left endpoint of the range and the maximum value of the preset temperature range as the right endpoint of the range, a third temperature range of the battery cluster is constructed, and the current limit level of the third temperature range of the battery cluster is determined as the third current limit level;

[0030] Taking the maximum value of the preset temperature range as the left endpoint of the range and the sum value of the maximum value of the preset temperature range and the second preset temperature variable as the right endpoint of the range, a fourth temperature range of the battery cluster is constructed, and the current limit level of the fourth temperature range of the battery cluster is determined as the fourth current limit level;

[0031] Taking the sum value of the maximum value of the preset temperature range and the second preset temperature variable as the left endpoint of the range and the sum value of the maximum value of the preset temperature range and the third preset temperature variable as the right endpoint of the range, a fifth temperature range of the battery cluster is constructed, and the current limit level of the fifth temperature range of the battery cluster is determined as the fifth current limit level;

[0032] Taking the sum value of the maximum value of the preset temperature range and the third preset temperature variable as the left endpoint of the range and the sum value of the maximum value of the preset temperature range and the fourth preset temperature variable as the right endpoint of the range, a sixth temperature range of the battery cluster is constructed, and the current limit level of the sixth temperature range of the battery cluster is determined as the sixth current limit level;

[0033] Taking the sum of the maximum value of the preset temperature range and the fourth preset temperature variable as the left endpoint of the interval, construct the seventh temperature range of the battery cluster, and determine that the current limit level of the seventh temperature range of the battery cluster is the seventh current limit level.

[0034] Optionally, the multiple preset overload capabilities include: a first preset overload capability, a second preset overload capability, and a third preset overload capability;

[0035] The first preset overload capability includes: a first overload current and a first maximum continuous overcurrent duration; the second preset overload capability includes: a second overload current and a second maximum continuous overcurrent duration; the third preset overload capability includes: a third overload current and a third maximum continuous overcurrent duration;

[0036] The multiple preset re-availability interval durations include: a first preset re-availability interval duration, a second preset re-availability interval duration, a third preset re-availability interval duration, a fourth preset re-availability interval duration, a fifth preset re-availability interval duration, a sixth preset re-availability interval duration, and a seventh preset re-availability interval duration;

[0037] The first overload current > the second overload current > the third overload current; the first maximum continuous overcurrent duration < the second maximum continuous overcurrent duration < the third maximum continuous overcurrent duration; the first preset re-availability interval duration > the second preset re-availability interval duration > the third preset re-availability interval duration > the fourth preset re-availability interval duration > the fifth preset re-availability interval duration > the sixth preset re-availability interval duration > the seventh preset re-availability interval duration.

[0038] Optionally, step S320 includes:

[0039] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the grid-forming energy storage converter under the first current limit level are the first overload current, the first maximum continuous overcurrent duration, and the first preset re-availability interval duration, respectively;

[0040] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the grid-forming energy storage converter under the second current limit level are the second overload current, the second maximum continuous overcurrent duration, and the second preset re-availability interval duration, respectively;

[0041] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the grid-forming energy storage converter under the third current limit level are the third overload current, the third maximum continuous overcurrent duration, and the third preset re-availability interval duration, respectively;

[0042] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the fourth current limit level are respectively the product of the third overload current and the first preset coefficient, the quotient of the third maximum continuous overcurrent duration and the first preset coefficient, and the fourth preset re-availability interval duration;

[0043] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the fifth current limit level are respectively the product of the third overload current and the second preset coefficient, the quotient of the third maximum continuous overcurrent duration and the second preset coefficient, and the fifth preset re-availability interval duration;

[0044] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the sixth current limit level are respectively the product of the third overload current and the third preset coefficient, the quotient of the third maximum continuous overcurrent duration and the third preset coefficient, and the sixth preset re-availability interval duration;

[0045] Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the seventh current limit level are respectively the product of the third overload current and the fourth preset coefficient, the quotient of the third maximum continuous overcurrent duration and the fourth preset coefficient, and the seventh preset re-availability interval duration;

[0046] Wherein, the first preset coefficient > the second preset coefficient > the third preset coefficient > the fourth preset coefficient.

[0047] Optionally, step S500 includes:

[0048] Use the following formula to calculate the maximum overload current of the network-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the current difference;

[0049] Wherein, ΔI represents the current difference, id represents the direct-axis component of the output current of the energy storage system, iq represents the quadrature-axis component of the output current of the energy storage system, and I max represents the maximum overload current of the network-forming energy storage converter;

[0050] Calculate the product of the current difference, the preset gain, and the preset impedance control coefficient to obtain the virtual reactance;

[0051] Respectively calculate the quotient of the virtual reactance and the preset impedance control coefficient and the angular frequency of the inverter output voltage to obtain the virtual resistance and the virtual inductance;

[0052] Use the following formula to calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductance, and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the direct-axis virtual voltage drop of the energy storage system;

[0053] Among them, Δ ud represents the direct-axis virtual voltage drop of the energy storage system, Rv represents the virtual resistance, Lv represents the virtual inductance, represents the angular frequency of the inverter output voltage;

[0054] Using the following formula, calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductance, and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the quadrature-axis virtual voltage drop of the energy storage system;

[0055] Among them, Δ uq represents the quadrature-axis virtual voltage drop of the energy storage system.

[0056] Optionally, step S800 includes:

[0057] Calculate the quotients of the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current and the reference value of the output current respectively to obtain the direct-axis direction cosine and quadrature-axis direction sine of the energy storage system;

[0058] Calculate the products of the direct-axis direction cosine and quadrature-axis direction sine of the energy storage system and the maximum overload current of the grid-forming energy storage converter respectively to obtain the limit value of the direct-axis component of the output current and the limit value of the quadrature-axis component of the output current of the energy storage system.

[0059] In the second aspect of the embodiments of the present invention, a grid-forming energy storage converter hierarchical current limiting control device is provided, including:

[0060] A data acquisition module for acquiring the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters;

[0061] A parameter determination module for determining the direct-axis component and quadrature-axis component of the output voltage of the energy storage system based on the output voltage of the energy storage system, and determining the direct-axis component and quadrature-axis component of the output current of the energy storage system based on the output current of the energy storage system; and determining the active power, reactive power and AC voltage amplitude of the energy storage system based on the output voltage and output current of the energy storage system;

[0062] A current determination module for determining the maximum overload current of the grid-forming energy storage converter based on the maximum temperature of multiple battery clusters of the energy storage system and the output current;

[0063] A voltage drop determination module for obtaining the equivalent direct-axis component and equivalent quadrature-axis component of the output voltage of the energy storage system according to the virtual synchronous machine control strategy based on the direct-axis component of the output voltage, quadrature-axis component of the output voltage, active power, reactive power and AC voltage amplitude of the energy storage system;

[0064] An impedance control module, configured to obtain a direct-axis virtual voltage drop and a quadrature-axis virtual voltage drop of the energy storage system according to a virtual impedance control strategy based on the maximum overload current of the network-forming energy storage converter, the direct-axis component of the output current of the energy storage system, and the quadrature-axis component of the output current of the energy storage system;

[0065] A voltage deduction module, configured to deduct the direct-axis virtual voltage drop of the energy storage system from the direct-axis component of the equivalent voltage of the energy storage system to obtain a reference value of the direct-axis component of the output voltage of the energy storage system, and deduct the quadrature-axis virtual voltage drop of the energy storage system from the quadrature-axis component of the equivalent voltage of the energy storage system to obtain a reference value of the quadrature-axis component of the output voltage of the energy storage system;

[0066] A first control module, configured to, based on the reference value of the direct-axis component of the output voltage of the energy storage system, the reference value of the quadrature-axis component of the output voltage of the energy storage system, the direct-axis component of the output voltage, and the quadrature-axis component of the output voltage, after PI control, obtain a reference value of the direct-axis component of the output current of the energy storage system and a reference value of the quadrature-axis component of the output current of the energy storage system, and based on the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system, obtain a reference value of the output current of the energy storage system;

[0067] A current calculation module, configured to, when the reference value of the output current of the energy storage system is greater than the maximum overload current of the network-forming energy storage converter, based on the maximum overload current of the network-forming energy storage converter, the reference value of the direct-axis component of the output current of the energy storage system, the reference value of the quadrature-axis component of the output current of the energy storage system, and the reference value of the output current of the energy storage system, obtain a limit value of the direct-axis component of the output current of the energy storage system and a limit value of the quadrature-axis component of the output current of the energy storage system;

[0068] A second control module, configured to constrain the reference value of the direct-axis component of the output current of the energy storage system not to exceed the limit value of the direct-axis component of the output current of the energy storage system and constrain the reference value of the quadrature-axis component of the output current of the energy storage system not to exceed the limit value of the quadrature-axis component of the output current of the energy storage system, obtain a finally generated reference value of the direct-axis component of the output current of the energy storage system and a finally generated reference value of the quadrature-axis component of the output current of the energy storage system, and use the finally generated reference value of the direct-axis component of the output current of the energy storage system and the finally generated reference value of the quadrature-axis component of the output current of the energy storage system as a closed-loop control instruction for the current inner loop, and through the current inner loop and the modulation module, control the output current of the energy storage system not to exceed the maximum overload current of the network-forming energy storage converter.

[0069] In a third aspect of the embodiments of the present invention, an electronic device is provided, including: a processor and a memory, where the memory stores machine-readable instructions executable by the processor, and when the machine-readable instructions are executed by the processor, the above-mentioned hierarchical current limiting control method for the network-forming energy storage converter is executed.

[0070] Advantages of the present invention:

[0071] (1) By means of the virtual impedance current limiting method, the output voltage component is dynamically adjusted to actively reduce the output current without switching the control mode. At the same time, the saturated current limit method is combined to hierarchically constrain the current component, avoiding the operation of the traditional forced switching to the grid-following mode. This design enables the grid-forming converter to still maintain the active regulation ability of the grid voltage and frequency during the current limiting process, solves the problem of the loss of grid support ability caused by mode switching, and thus significantly improves the transient stability of the system.

[0072] (2) By real-time collecting the temperatures of multiple battery clusters and dynamically calculating the maximum overload current based on the highest temperature cluster, the temperature parameter is directly associated with the output current limit. When the temperature of a certain battery cluster rises abnormally, the system automatically reduces the overall output power, forcibly balances the load distribution among multiple clusters, and suppresses the local overheating phenomenon. Starting from the thermodynamic source, this method realizes the temperature-current coordinated control among battery clusters, effectively reducing the risk of thermal runaway caused by uneven temperature.

[0073] (3) The virtual impedance current limiting method quickly responds to transient overcurrent and suppresses current spikes through virtual voltage drops within milliseconds. If the overcurrent persists, the saturated current limit method is further used to perform steady-state constraint on the current component. The two methods respectively target instantaneous and long-term overcurrent scenarios, forming a hierarchical current limiting timing strategy of "first dynamic adjustment, then hard limiting", solving the adaptation contradiction of the traditional single current limiting method on the time scale, and achieving the dual goals of rapid decay of transient overcurrent and reliable protection of steady-state current limiting.

[0074] (4) In the transient large current scenario, the virtual impedance current limiting method quickly reduces the current peak by reducing the output voltage component, avoiding the short-term overcurrent impact on power devices. For the continuous large current condition, the saturated current limit method hard truncates the output current through the direct axis / quadrature axis current limit values. The two cooperate to construct a dual protection mechanism of "transient peak shaving + steady-state limiting", ensuring that the power devices do not exceed their maximum withstand current under transient and steady-state conditions, and significantly reducing the probability of device damage.

[0075] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent specific implementation part. Brief Description of the Drawings

[0076] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. They are used together with the following specific implementation to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0077] Figure 1 is a schematic flow chart of the hierarchical current limiting control method of the grid-forming energy storage converter provided by the embodiments of the present invention;

[0078] Figure 2 It is a control schematic diagram of a network-forming energy storage system converter provided by an embodiment of the present invention;

[0079] Figure 3 It is a structural schematic diagram of a hierarchical current limiting control device for a network-forming energy storage converter provided by an embodiment of the present invention. Specific embodiments

[0080] The following will describe in detail the specific embodiments of the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0081] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit this application.

[0082] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means more than two, unless otherwise specifically defined.

[0083] Embodiment 1

[0084] Please refer to Figure 1 , Figure 1 It is a flow schematic diagram of a hierarchical current limiting control method for a network-forming energy storage converter provided by an embodiment of the present invention. The method includes the following steps:

[0085] S100, obtain the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters;

[0086] The output voltage of the energy storage system refers to the voltage value at its output terminal when the system is operating (discharging or charging).

[0087] The output current of the energy storage system refers to the magnitude of the current flowing through its port during the process of electrical energy output.

[0088] The temperatures of multiple battery clusters of the energy storage system refer to the temperature states of each independent battery cluster (composed of multiple battery modules) in the energy storage system, which are usually monitored in real time by built-in sensors.

[0089] S200. Determine the direct-axis component and quadrature-axis component of the output voltage of the energy storage system based on the output voltage of the energy storage system, and determine the direct-axis component and quadrature-axis component of the output current of the energy storage system based on the output current of the energy storage system; and determine the active power, reactive power, and AC voltage amplitude of the energy storage system based on the output voltage and output current of the energy storage system.

[0090] As Figure 2 shown, in the control of the energy storage system, the three-phase voltage / current (Uabc, Iabc) is transformed from the stationary coordinate system (abc) to the synchronous rotating coordinate system (dq) through coordinate transformation (such as Clark-Park transformation) to obtain the direct-axis component (Ud, Id) and quadrature-axis component (Uq, Iq). Among them, Ud and Uq respectively correspond to the active and reactive voltage components synchronized with the power grid, and Id and Iq reflect the corresponding current characteristics; further calculate the active power P = 1.5(Ud * Id + Uq * Iq) and reactive power Q = 1.5(Uq * Id - Ud * Iq) based on the dq components, and measure the AC side voltage level through the voltage amplitude to finally achieve power decoupling control and precise regulation of grid interaction.

[0091] Clarke transformation: Transform the three-phase stationary coordinate system (abc) into a two-phase stationary coordinate system (αβ) to reduce the number of variables and facilitate analysis.

[0092] Park transformation: Transform the two-phase stationary coordinate system (αβ) into a two-phase rotating coordinate system (dq) to convert AC quantities into DC quantities and simplify the control design.

[0093] The direct-axis component of the output current of the energy storage system refers to the current component in the direct-axis direction, which mainly affects the magnetic field of the motor. In a synchronous motor, the direct-axis current component is usually related to the excitation current and is used to generate or adjust the magnetic field of the motor.

[0094] The quadrature-axis component of the output current of the energy storage system refers to the current component in the quadrature-axis direction, which mainly affects the torque output of the motor. In a synchronous motor, the quadrature-axis current component is proportional to the torque of the motor and is used to drive the mechanical load of the motor.

[0095] The direct-axis component of the output voltage of the energy storage system refers to the voltage component in the direct-axis direction. It is usually related to the voltage drop of the magnetic field of the motor and the voltage drop generated by the direct-axis current component. In motor control, the direct-axis voltage component can be used to adjust the magnetic field of the motor, thereby affecting the performance of the motor.

[0096] The quadrature-axis component of the output voltage of the energy storage system refers to the voltage component in the quadrature axis direction. It is usually related to the torque voltage drop of the motor and the voltage drop generated by the quadrature-axis current component. In motor control, the quadrature-axis voltage component can be used to adjust the torque output of the motor to meet different load requirements.

[0097] In one embodiment, as Figure 2 shown, based on the output voltage of the energy storage system, determining the direct-axis component and the quadrature-axis component of the output voltage of the energy storage system includes:

[0098] Convert the three-phase voltage Uabc (with a phase difference of 120°) to Uα and Uβ in the two-phase stationary coordinate system (αβ):

[0099] Clarke transformation:

[0100] Uα = 2 / 3(Ua - 1 / 2Ub - 1 / 2Uc);

[0101] Uβ = √3 / 3(Ub - Uc).

[0102] Park transformation:

[0103] Use a phase-locked loop (PLL) to obtain the grid voltage phase angle θ, and rotate Uα and Uβ to the synchronous rotating coordinate system (dq):

[0104] Ud = Uαcosθ + Uβsinθ;

[0105] Uq = -Uαsinθ + Uβcosθ.

[0106] In one embodiment, as Figure 2 shown, based on the output current of the energy storage system, determining the direct-axis component and the quadrature-axis component of the output current of the energy storage system includes:

[0107] Convert the three-phase voltage Iabc (with a phase difference of 120°) to Iα and Iβ in the two-phase stationary coordinate system (αβ):

[0108] Clarke transformation:

[0109] Iα = 2 / 3(Ia - 1 / 2Ib - 1 / 2Ic);

[0110] Iβ = √3 / 3(Ib - Ic).

[0111] Park transformation:

[0112] Use a phase-locked loop (PLL) to obtain the grid voltage phase angle θ, and rotate Iα and Iβ to the synchronous rotating coordinate system (dq):

[0113] Id = Iαcosθ + Iβsinθ;

[0114] Iq = _Iαsinθ + Iβcosθ.

[0115] In one embodiment, as Figure 2 shown, based on the output voltage and output current of the energy storage system, determining the active power, reactive power, and AC voltage amplitude of the energy storage system includes:

[0116] Active power P: P = 3 / 2(UdId + UqIq). If grid voltage orientation control (Uq = 0) is adopted, it is simplified to: P = 3 / 2UdId.

[0117] Reactive power Q: Q = 3 / 2(UqId - UdIq). When Uq = 0, it is simplified to: Q = -3 / 2UdIq.

[0118] AC voltage amplitude Um: Um = √Ud 2 + Uq 2 . Under grid voltage orientation control, Uq ≈ 0, so Um ≈ Ud.

[0119] S300. Based on the maximum temperature and output current of multiple battery clusters of the energy storage system, determining the maximum overload current of the grid-forming energy storage converter;

[0120] In one embodiment, step S300 includes:

[0121] S310: Based on a preset temperature range, delimiting the current limit level for the maximum temperature of the battery cluster to determine the current current limit level of the grid-forming energy storage converter;

[0122] Specifically, step S310 includes:

[0123] S311. Based on the preset temperature range and multiple preset temperature variables, delimiting multiple temperature ranges of the battery cluster; wherein, each temperature range corresponds to a different current limit level;

[0124] In one embodiment, step S311 includes:

[0125] The multiple preset temperature variables include: a first preset temperature variable, a second preset temperature variable, a third preset temperature variable, and a fourth preset temperature variable; the first preset temperature variable < the second preset temperature variable < the third preset temperature variable < the fourth preset temperature variable;

[0126] Taking the minimum value of the preset temperature range as the left endpoint of the interval and the sum value of the minimum value of the preset temperature range and the first preset temperature variable as the right endpoint of the interval, constructing the first temperature range of the battery cluster and determining the current limit level of the first temperature range of the battery cluster as the first current limit level;

[0127] Taking the sum of the minimum value of the preset temperature range and the first preset temperature variable as the left endpoint of the interval, and the difference between the maximum value of the preset temperature range and the first preset temperature variable as the right endpoint of the interval, construct the second temperature range of the battery cluster, and determine that the current limit level of the second temperature range of the battery cluster is the second current limit level;

[0128] Taking the difference between the maximum value of the preset temperature range and the first preset temperature variable as the left endpoint of the interval, and the maximum value of the preset temperature range as the right endpoint of the interval, construct the third temperature range of the battery cluster, and determine that the current limit level of the third temperature range of the battery cluster is the third current limit level;

[0129] Taking the maximum value of the preset temperature range as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the second preset temperature variable as the right endpoint of the interval, construct the fourth temperature range of the battery cluster, and determine that the current limit level of the fourth temperature range of the battery cluster is the fourth current limit level;

[0130] Taking the sum of the maximum value of the preset temperature range and the second preset temperature variable as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the third preset temperature variable as the right endpoint of the interval, construct the fifth temperature range of the battery cluster, and determine that the current limit level of the fifth temperature range of the battery cluster is the fifth current limit level;

[0131] Taking the sum of the maximum value of the preset temperature range and the third preset temperature variable as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the fourth preset temperature variable as the right endpoint of the interval, construct the sixth temperature range of the battery cluster, and determine that the current limit level of the sixth temperature range of the battery cluster is the sixth current limit level;

[0132] Taking the sum of the maximum value of the preset temperature range and the fourth preset temperature variable as the left endpoint of the interval, construct the seventh temperature range of the battery cluster, and determine that the current limit level of the seventh temperature range of the battery cluster is the seventh current limit level.

[0133] For the sake of easy understanding, the following is an example:

[0134] Suppose the preset temperature range is [20°C, 30°C], the first temperature variable is 3.3°C, the second temperature variable is 5°C, the third temperature variable is 10°C, and the fourth temperature variable is 20°C, then the temperature range is divided as follows:

[0135] The first temperature range of the battery cluster is [-∞, 20 + 3.3°C], and the current limit level is the first current limit level;

[0136] The second temperature range of the battery cluster is [20 + 3.3°C, 30 - 3.3°C], and the current limit level is the second current limit level;

[0137] The third temperature range of the battery cluster is [30 - 3.3°C, 30°C], and the current limit level is the third current limit level;

[0138] The fourth temperature range of the battery cluster is [30°C, 30 + 5°C], and the current limit level is the fourth current limit level;

[0139] The fifth temperature range of the battery cluster is [30 + 5°C, 30 + 10°C], and the current limit level is the fifth current limit level;

[0140] The sixth temperature range of the battery cluster is [30 + 10°C, 30 + 20°C], and the current limit level is the sixth current limit level;

[0141] The seventh temperature range of the battery cluster ≥ 30 + 20°C, and the current limit level is the seventh current limit level.

[0142] S312. Determine the current current limit level of the grid-forming energy storage converter by judging the temperature range of the battery cluster to which the maximum value of the temperature of the battery cluster belongs.

[0143] Specifically, for example, if the maximum value of the temperature of the battery cluster is 22°C, according to the temperature range of the battery cluster divided in step 311, it can be known that 22°C falls within the first temperature range of the battery cluster, then the current limit level of the grid-forming energy storage converter is the first current limit level.

[0144] S320. Judge whether the current current limit level of the grid-forming energy storage converter is in an available state;

[0145] S330. If so, based on the current current limit level of the grid-forming energy storage converter, multiple preset overload capabilities, and multiple preset re-availability interval durations, determine the maximum overload current, maximum continuous overcurrent duration, and re-availability interval duration of the grid-forming energy storage converter at the current current limit level;

[0146] The multiple preset overload capabilities include: the first preset overload capability, the second preset overload capability, and the third preset overload capability;

[0147] The first preset overload capability includes: the first overload current and the first maximum continuous overcurrent duration; the second preset overload capability includes: the second overload current and the second maximum continuous overcurrent duration; the third preset overload capability includes: the third overload current and the third maximum continuous overcurrent duration;

[0148] The multiple preset re-availability interval durations include: the first preset re-availability interval duration, the second preset re-availability interval duration, the third preset re-availability interval duration, the fourth preset re-availability interval duration, the fifth preset re-availability interval duration, the sixth preset re-availability interval duration, and the seventh preset re-availability interval duration;

[0149] The first overload current > the second overload current > the third overload current; the first maximum continuous overcurrent duration < the second maximum continuous overcurrent duration < the third maximum continuous overcurrent duration; the first preset re-availability interval duration > the second preset re-availability interval duration > the third preset re-availability interval duration > the fourth preset re-availability interval duration > the fifth preset re-availability interval duration > the sixth preset re-availability interval duration > the seventh preset re-availability interval duration.

[0150] For better understanding, the following uses actual data to give examples to illustrate the magnitude relationships of the overload capabilities among multiple preset overload capabilities and the magnitude relationships of the re-availability interval durations among multiple preset re-availability interval durations:

[0151] The first overload current is 160A, the first maximum continuous overcurrent duration is 10S, the second overload current is 140A, the second maximum continuous overcurrent duration is 60S, the third overload current is 100A, and the third maximum continuous overcurrent duration is 120S.

[0152] The first preset re-availability interval duration is 300s, the second preset re-availability interval duration is 240s, the third preset re-availability interval duration is 180, the fourth preset re-availability interval duration is 120s, the fifth preset re-availability interval duration is 60s, the sixth preset re-availability interval duration is 30s, and the seventh preset re-availability interval duration is 10s.

[0153] In one embodiment, step S330 includes:

[0154] S331, determining that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter under the first current limit level are the first overload current, the first maximum continuous overcurrent duration, and the first preset re-availability interval duration, respectively;

[0155] S332, determining that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter under the second current limit level are the second overload current, the second maximum continuous overcurrent duration, and the second preset re-availability interval duration, respectively;

[0156] S333, determining that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter under the third current limit level are the third overload current, the third maximum continuous overcurrent duration, and the third preset re-availability interval duration, respectively;

[0157] S334, determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - availability interval duration of the grid - forming energy storage converter at the fourth current limit level are respectively the product of the third overload current and the first preset coefficient, the quotient of the third maximum continuous overcurrent duration and the first preset coefficient, and the fourth preset re - availability interval duration;

[0158] S335, determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - availability interval duration of the grid - forming energy storage converter at the fifth current limit level are respectively the product of the third overload current and the second preset coefficient, the quotient of the third maximum continuous overcurrent duration and the second preset coefficient, and the fifth preset re - availability interval duration;

[0159] S336, determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - availability interval duration of the grid - forming energy storage converter at the sixth current limit level are respectively the product of the third overload current and the third preset coefficient, the quotient of the third maximum continuous overcurrent duration and the third preset coefficient, and the sixth preset re - availability interval duration;

[0160] S337, determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - availability interval duration of the grid - forming energy storage converter at the seventh current limit level are respectively the product of the third overload current and the fourth preset coefficient, the quotient of the third maximum continuous overcurrent duration and the fourth preset coefficient, and the seventh preset re - availability interval duration;

[0161] Among them, the first preset coefficient > the second preset coefficient > the third preset coefficient > the fourth preset coefficient.

[0162] For the sake of easy understanding, the following takes actual data as an example to illustrate steps S321 - S327:

[0163] Suppose the first overload current is 160A, the first maximum continuous overcurrent duration is 10S, the second overload current is 140A, the second maximum continuous overcurrent duration is 60S, the third overload current is 100A, and the third maximum continuous overcurrent duration is 120S.

[0164] Suppose the first preset re - availability interval duration is 300s, the second preset re - availability interval duration is 240s, the third preset re - availability interval duration is 180, the fourth preset re - availability interval duration is 120s, the fifth preset re - availability interval duration is 60s, the sixth preset re - availability interval duration is 30s, and the seventh preset re - availability interval duration is 10s.

[0165] The first preset coefficient is 0.8, the second preset coefficient is 0.5, the third preset coefficient is 0.3, and the fourth preset coefficient is 0.1.

[0166] The grid-forming energy storage converter is at the first current limit level: 160 A (overload current), 10 s (continuous overcurrent duration), and 300 s (reusable interval duration).

[0167] The grid-forming energy storage converter is at the second current limit level: 140 A (overload current), 60 s (continuous overcurrent duration), and 240 s (reusable interval duration).

[0168] The grid-forming energy storage converter is at the third current limit level: 100 A (overload current), 120 s (continuous overcurrent duration), and 180 s (reusable interval duration).

[0169] The grid-forming energy storage converter is at the fourth current limit level: 100 * 0.8 A (overload current), 120 / 0.8 s (continuous overcurrent duration), and 120 s (reusable interval duration).

[0170] The grid-forming energy storage converter is at the fifth current limit level: 100 * 0.5 A (overload current), 120 / 0.5 s (continuous overcurrent duration), and 60 s (reusable interval duration).

[0171] The grid-forming energy storage converter is at the sixth current limit level: 100 * 0.3 A (overload current), 120 / 0.3 s (continuous overcurrent duration), and 30 s (reusable interval duration).

[0172] The grid-forming energy storage converter is at the seventh current limit level: 100 * 0.1 A (overload current), 120 / 0.1 s (continuous overcurrent duration), and 10 s (reusable interval duration).

[0173] In one embodiment, a grid-forming energy storage converter overload capacity matrix table is provided. Users can directly determine the maximum overload current, continuous overcurrent duration, and reusable interval duration of the grid-forming energy storage converter according to this table, as shown in Table 1 below:

[0174] Table 1 Grid-forming energy storage converter overload capacity matrix table

[0175]

[0176]

[0177] S340, if the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter at the current current limit level, start overcurrent timing. When the overcurrent timing duration is greater than the maximum continuous overcurrent duration of the grid-forming energy storage converter at the current current limit level, increment the current current limit level of the grid-forming energy storage converter, mark the current current limit level of the grid-forming energy storage converter as an unavailable state, return to step S330, and at the same time start cooling timing. When the cooling timing duration is greater than the re-availability interval duration of the grid-forming energy storage converter at the current current limit level, mark the current current limit level of the grid-forming energy storage converter as an available state and return to step S310;

[0178] It should be noted that step S340 solves the drawback of the "one-size-fits-all" protection of traditional current limiting methods. If the circuit is directly cut off with a single current threshold, although it can prevent equipment damage, it will cause the system to stop frequently, affecting power supply continuity; while if overcurrent is allowed, permanent damage will be caused due to overheating of the device. Therefore, this step seeks a balance between the two through a hierarchical current limiting and cooling recovery mechanism, allowing short-term controllable overloads (such as supporting voltage during grid transient faults), quantifying the overload risk through a timer, and gradually increasing the current limiting intensity to protect the hardware progressively; at the same time, the forced cooling interval provides heat dissipation time for the device to avoid temperature accumulation from breaking down the insulation, so as to maximize the grid-connected operation ability of the energy storage system under overload conditions while ensuring equipment safety and improving its active support reliability for the grid.

[0179] S350, if not, increment the current current limit level of the grid-forming energy storage converter and return to step S320.

[0180] It should be noted that the function of step S360 is to find the current current limit level of the grid-forming energy storage converter in the available state.

[0181] S400, based on the direct-axis component of the output voltage of the energy storage system, the quadrature-axis component of the output voltage, the active power, the reactive power, and the AC voltage amplitude, obtain the equivalent direct-axis component and the equivalent quadrature-axis component of the output voltage of the energy storage system according to the virtual synchronous generator control strategy;

[0182] Specifically, as Figure 2 shown, the virtual synchronous generator (VSG) control strategy simulates the dynamic characteristics of a synchronous generator, generates a frequency deviation by adjusting the active power deviation of the energy storage system through virtual inertia and damping, and then adjusts the phase angle to determine the direct-axis (d-axis) component Ud of the output voltage; at the same time, using the error between the reactive power deviation and the AC voltage amplitude, generates the quadrature-axis (q-axis) component Uq through a voltage regulator, so that Ud and Uq can equivalently represent the internal electromotive force of the VSG, thereby realizing the active support for the grid and the adaptive control of power-voltage.

[0183] S500. Based on the maximum overload current of the network-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system, according to the virtual impedance control strategy, obtain the direct-axis virtual voltage drop and quadrature-axis virtual voltage drop of the energy storage system.

[0184] It should be noted that, as Figure 2 shown, the virtual impedance current limiting method is an active control strategy that simulates the equivalent impedance characteristics in a power electronic converter (such as a network-forming energy storage system) through a control algorithm. Its core is to introduce virtual impedance (such as resistance, inductance, or a combination thereof) into the output voltage command. When the output current increases, the virtual impedance will generate a voltage drop in proportion and reduce the actual output voltage through negative feedback, thereby suppressing the current amplitude, limiting the overload or short-circuit current, and maintaining the system stability at the same time. This method does not require physical impedance devices, can flexibly adjust the direct and quadrature-axis current components, and is applicable to dynamic current limiting and fault protection in scenarios such as microgrids and new energy grid connection.

[0185] Specifically, in the embodiment of the present invention, first determine the maximum overload current threshold I max according to the capacity and thermal limit of the network-forming energy storage converter. Subsequently, decompose the output current into a direct-axis component Id and a quadrature-axis component Iq through coordinate transformation. When the output current exceeds I max , use the preset virtual impedance parameters (such as resistance Rv or impedance Zv) to calculate the direct-axis virtual voltage drop ΔVd = Id * Rv and the quadrature-axis virtual voltage drop ΔVq = Iq * Rv respectively.

[0186] In one embodiment, step S500 includes:

[0187] S510. Use the following formula to calculate the maximum overload current of the network-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the current difference;

[0188] where, ΔI represents the current difference, id represents the direct-axis component of the output current of the energy storage system, iq represents the quadrature-axis component of the output current of the energy storage system, and I max represents the maximum overload current of the network-forming energy storage converter;

[0189] S520. Calculate the product of the current difference, a preset gain, and a preset impedance control coefficient to obtain the virtual reactance;

[0190] S530. Calculate the quotient of the virtual reactance and the product of the preset impedance control coefficient and the angular frequency of the inverter output voltage respectively to obtain the virtual resistance and virtual inductance;

[0191] S540, using the following formula, calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductor, and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the direct-axis virtual voltage drop of the energy storage system;

[0192] where, Δ ud represents the direct-axis virtual voltage drop of the energy storage system, Rv represents the virtual resistance, Lv represents the virtual inductor, represents the angular frequency of the inverter output voltage;

[0193] S550, using the following formula, calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductor, and the direct-axis component and quadrature-axis component of the output current of the energy storage system to obtain the quadrature-axis virtual voltage drop of the energy storage system;

[0194] where, Δ uq represents the quadrature-axis virtual voltage drop of the energy storage system.

[0195] S600, subtract the direct-axis virtual voltage drop of the energy storage system from the direct-axis component of the equivalent voltage of the energy storage system to obtain the reference value of the direct-axis component of the output voltage of the energy storage system, and subtract the quadrature-axis virtual voltage drop of the energy storage system from the quadrature-axis component of the equivalent voltage of the energy storage system to obtain the reference value of the quadrature-axis component of the output voltage of the energy storage system;

[0196] Specifically, in the control of the energy storage system, by subtracting the direct-axis virtual voltage drop generated by the virtual impedance from the direct-axis (d-axis) component of the output voltage, and at the same time subtracting the quadrature-axis virtual voltage drop from the quadrature-axis (q-axis) component of the output voltage, and subtracting these voltage drops from the output voltage command through the voltage control loop to form a negative feedback to suppress the current amplitude, so as to achieve dynamic current limiting protection and active regulation of the direct (d)-axis and quadrature (q)-axis current components, thereby suppressing the current amplitude, enhancing the system stability, and achieving current limiting protection or power dynamic balance, which is applicable to current control and fault ride-through in microgrid or grid-connected scenarios.

[0197] S700, based on the reference value of the direct-axis component of the output voltage of the energy storage system, the reference value of the quadrature-axis component of the output voltage, the direct-axis component of the output voltage, and the quadrature-axis component of the output voltage, after PI control, obtain the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current, and based on the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current, obtain the reference value of the output current of the energy storage system;

[0198] It can be understood that, as Figure 2As shown, in the energy storage system control, through the voltage outer loop (double closed-loop structure) and the dq decoupling strategy, the direct-axis (d-axis) and quadrature-axis (q-axis) components of the output voltage are compared with their reference values. After the error is processed by the PI controller, the direct-axis and quadrature-axis current reference values (Id_dref, Iq_dref) of the current inner loop are generated. The voltage outer loop adjusts the output voltage amplitude or power, and the current inner loop quickly tracks the command. Combining the feedforward decoupling to eliminate the d-q axis coupling, finally, the precise control of voltage or power is achieved through inverter modulation, which is applicable to scenarios such as islanding or grid connection.

[0199] Specifically, where I represents the reference value of the output current of the energy storage system, I_dref represents the reference value of the direct-axis component of the output current of the energy storage system, and I_qref represents the reference value of the quadrature-axis component of the output current of the energy storage system.

[0200] S800, if the reference value of the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter, then based on the maximum overload current of the grid-forming energy storage converter, the reference value of the direct-axis component of the output current of the energy storage system, the reference value of the quadrature-axis component of the output current of the energy storage system, and the reference value of the output current of the energy storage system, the limit value of the direct-axis component of the output current of the energy storage system and the limit value of the quadrature-axis component of the output current of the energy storage system are obtained.

[0201] It should be noted that, as Figure 2 shown, the saturated current limit method is a protection strategy implemented by presetting the maximum current threshold (saturation value). When the system detects that the output current (such as the direct-axis Id component or the quadrature-axis Iq component) exceeds the set safety limit, by forcibly limiting the current command or adjusting the control signal (such as reducing the modulation ratio, clamping the PWM output, etc.), the actual current no longer increases and stabilizes below the threshold, thereby avoiding equipment overload or damage. This method directly "cuts off" the over-limit current, which belongs to hard protection and is commonly used for fast overcurrent protection in scenarios such as power electronic converters and motor drives, but it needs to cooperate with dynamic control strategies to avoid system oscillation or performance deterioration.

[0202] In one embodiment, step S800 includes:

[0203] S810, respectively calculate the quotients of the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system divided by the reference value of the output current of the energy storage system to obtain the direct-axis direction cosine and the quadrature-axis direction sine of the energy storage system;

[0204] S820, respectively calculate the products of the direct-axis direction cosine and the quadrature-axis direction sine of the energy storage system and the maximum overload current of the grid-forming energy storage converter to obtain the limit value of the direct-axis component of the output current of the energy storage system and the limit value of the quadrature-axis component of the output current of the energy storage system.

[0205] Specifically, in the embodiments of the present invention, when the output current reference value of the energy storage system still exceeds the maximum overload current I of the converter max first, set I according to the equipment capacity and thermal limit max , and obtain the current direct-axis current Id and quadrature-axis current Iq through coordinate transformation. If the total current amplitude Id 2 + Iq 2 > I max , then allocate the limit values according to proportion or priority (such as giving priority to active power), and calculate the direct-axis current limit value Id_lim = I max * Id / I and the quadrature-axis current limit value Iq_lim = I max * Iq (Id 2 + Iq 2 ≤ 1).

[0206] S900, restrict the reference value of the direct-axis component of the output current of the energy storage system not to exceed the limit value of the direct-axis component of the output current of the energy storage system and restrict the reference value of the quadrature-axis component of the output current of the energy storage system not to exceed the limit value of the quadrature-axis component of the output current of the energy storage system, obtain the finally generated reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system, and use the finally generated reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system as the closed-loop control command of the current inner loop. Through the current inner loop and the modulation module, control the output current of the energy storage system not to exceed the maximum overload current of the grid-forming energy storage converter.

[0207] Specifically, as Figure 2 shown, by dynamically restricting the reference values of the direct-axis (d-axis) and quadrature-axis (q-axis) components of the output current of the energy storage system, ensure that when the output current reference value exceeds the maximum overload capacity of the converter, first recalculate the upper limits of the allowable d-axis and q-axis current components according to the vector constraint conditions of the maximum overload current, then clamp the original reference value within this limit range, and finally use the adjusted current components as the closed-loop control command, and output through the current inner loop regulation and PWM modulation, so as to achieve the protection goal that the amplitude of the converter output current never exceeds its maximum overload capacity, taking into account the system dynamic response and the equipment safe operation requirements.

[0208] For ease of understanding, a specific embodiment of the present invention is given below:

[0209] The first step (data acquisition):

[0210] The direct-axis current component of the energy storage system: 90 A.

[0211] The quadrature-axis current component of the energy storage system: 60 A.

[0212] The direct-axis voltage component of the energy storage system: 300 V.

[0213] Quadrature-axis voltage component of the energy storage system: 20V.

[0214] Temperatures of multiple battery clusters: maximum value T max = 38°C.

[0215] Second step (overload capacity verification):

[0216] 1. Define current levels:

[0217] Assume the preset temperature range is [20°C, 30°C], the first temperature variable is 3.3°C, the second temperature variable is 5°C, the third temperature variable is 10°C, and the fourth temperature variable is 20°C.

[0218] Temperature range division:

[0219] The first temperature range of the battery cluster is [-∞, 20 + 3.3°C], and the current limit level is the first current limit level;

[0220] The second temperature range of the battery cluster is [20 + 3.3°C, 30 - 3.3°C], and the current limit level is the second current limit level;

[0221] The third temperature range of the battery cluster is [30 - 3.3°C, 30°C], and the current limit level is the third current limit level;

[0222] The fourth temperature range of the battery cluster is [30°C, 30 + 5°C], and the current limit level is the fourth current limit level;

[0223] The fifth temperature range of the battery cluster is [30 + 5°C, 30 + 10°C], and the current limit level is the fifth current limit level;

[0224] The sixth temperature range of the battery cluster is [30 + 10°C, 30 + 20°C], and the current limit level is the sixth current limit level;

[0225] The seventh temperature range of the battery cluster ≥ 30 + 20°C, and the current limit level is the seventh current limit level.

[0226] 2. Determine the current limit level:

[0227] T max = 38°C belongs to the fifth temperature range and is the fifth current limit level.

[0228] 3. Set overload parameters:

[0229] Preset parameters: the first preset coefficient is 0.8, the second preset coefficient is 0.5, the third preset coefficient is 0.3, and the fourth preset coefficient is 0.1.

[0230] First current limit level: First maximum overload current = 160 A, First maximum overload duration = 10 s, First available again interval duration = 300 s.

[0231] Second current limit level: Second maximum overload current = 140 A, Second maximum overload duration = 60 s, Second available again interval duration = 240 s.

[0232] Third current limit level: Third maximum overload current = 100 A, Third maximum overload duration = 120 s, Third available again interval duration = 180 s.

[0233] Fourth current limit level: Fourth maximum overload current = 100 * 0.8 = 80 A, Fourth maximum overload duration = 120 / 0.8 = 150 s, Fourth available again interval duration = 120 s.

[0234] Fifth current limit level: Fifth maximum overload current = 100 * 0.5 A = 50 A, Fifth maximum overload duration = 120 / 0.5 = 240 s, Fifth available again interval duration = 60 s.

[0235] Sixth current limit level: Sixth maximum overload current = 100 * 0.3 = 30 A, Sixth maximum overload duration = 120 / 0.3 = 400 s, Sixth available again interval duration = 30 s.

[0236] Seventh current limit level: Seventh maximum overload current = 100 * 0.1 = 10 A, Seventh maximum overload duration = 120 / 0.1 = 1200 s, Seventh available again interval duration = 10 s.

[0237] Parameters of the fifth current limit level: Maximum overload current 50 A, Maximum continuous overcurrent duration 240 s, and Available again interval duration 60 s.

[0238] 4. Overcurrent verification:

[0239] Current output by the energy storage system currently:

[0240] Since 108.17 A > 50 A, overcurrent timing is triggered. If it lasts for more than 240 s, it is necessary to upgrade to the sixth current limit level and start cooling timing (recovery after 60 s).

[0241] The third step (virtual impedance current limiting):

[0242] 1. Calculate the current difference:

[0243] 2. Calculate the virtual impedance: Let the gain Kp = 0.5 and the impedance control coefficient Z = 0.1 Ω; Virtual reactance

[0244] 3. Calculate the virtual resistance and inductance:

[0245] Let the angular frequency of the inverter be

[0246] Virtual resistance = virtual reactance ÷ impedance control coefficient = 2.9085 ÷ 0.1 = 29.085 Ω.

[0247] Virtual reactance = virtual reactance ÷ angular frequency of the inverter = 2.9085 ÷ 314.15 ≈ 0.009 H.

[0248] 4. Calculate the virtual voltage drop:

[0249]

[0250] Fourth step (output voltage adjustment):

[0251] Adjusted voltage:

[0252] New direct-axis voltage: 300 V - 2448.009 V = -2148.009 V.

[0253] New quadrature-axis voltage: 20 V - 1999.562 V = -1979.562 V.

[0254] Fifth step (current reduction effect):

[0255] The adjusted current components need to be recalculated, but the actual system will force the current to decrease through negative voltage feedback. Assume that after adjustment: the reference value of the direct-axis current component is 50 A, and the reference value of the quadrature-axis current component is 30 A.

[0256] Adjusted total current reference value:

[0257] Sixth step (saturated current limit (if still exceeding the limit after adjustment)):

[0258] It is necessary to allocate the direct-axis and quadrature-axis limits:

[0259] Direct-axis direction cosine = 50 / 58.31 ≈ 0.857.

[0260] Quadrature-axis direction cosine = 30 / 58.31 ≈ 0.514.

[0261] Direct-axis current limit value: 0.857 * 50 A ≈ 42.85 A.

[0262] Quadrature-axis current limit value: 0.514 * 50 A ≈ 25.7 A.

[0263] Summary: The temperature triggers the fifth current limit level, and the maximum allowable current is 50A. The virtual impedance significantly increases the voltage demand, forcing the current to decrease. If it still exceeds the limit, the saturation limit method limits the direct-axis and quadrature-axis currents to 42.85A and 25.7A respectively, ensuring that the total current ≤ 50A.

[0264] The system continuously monitors the temperature. If the overcurrent exceeds 240 seconds, the limit level is upgraded and cooling is started.

[0265] Advantages of the present invention:

[0266] (1) By using the virtual impedance current limiting method to dynamically adjust the output voltage component, the output current is actively reduced without switching the control mode. At the same time, combined with the saturated current limit method to hierarchically restrict the current component, the operation of the traditional forced switch to the grid-following mode is avoided. This design enables the grid-forming converter to still maintain the active regulation ability of the grid voltage and frequency during the current limiting process, solves the problem of the loss of grid support ability caused by mode switching, and thus significantly improves the transient stability of the system.

[0267] (2) By real-time collecting the temperatures of multiple clusters of batteries and dynamically calculating the maximum overload current based on the highest temperature cluster, the temperature parameter is directly associated with the output current limit. When the temperature of a certain battery cluster rises abnormally, the system automatically reduces the overall output power, forcibly balances the load distribution among multiple clusters, and suppresses the local overheating phenomenon. This method starts from the thermodynamic source and realizes the temperature-current co-control between battery clusters, effectively reducing the risk of thermal runaway caused by uneven temperature.

[0268] (3) By using the virtual impedance current limiting method to quickly respond to transient overcurrent, the current peak is suppressed by the virtual voltage drop within a few milliseconds. If the overcurrent persists, the saturated current limit method is further used to perform steady-state constraint on the current component. The two methods are respectively aimed at instantaneous and long-term overcurrent scenarios, forming a hierarchical current limiting time sequence strategy of "first dynamic adjustment, then hard limit", solving the adaptation contradiction of the traditional single current limiting method on the time scale, and realizing the dual goals of rapid decay of transient overcurrent and reliable protection of steady-state current limiting.

[0269] (4) In the transient large current scenario, the virtual impedance current limiting method quickly reduces the current peak by reducing the output voltage component, avoiding the short-time overcurrent impact on the power device. For the continuous large current condition, the saturated current limit method hard cuts off the output current through the direct-axis / quadrature-axis current limit values. The two cooperate to construct a dual protection mechanism of "transient peak shaving + steady-state limiting", ensuring that the power device does not exceed its maximum withstand current under transient and steady-state conditions, and significantly reducing the probability of device damage.

[0270] Embodiment 2

[0271] Based on the same inventive concept, asFigure 3 As shown in Figure 3 , an embodiment of the present invention further provides a hierarchical current limiting control device 200 for a grid-forming energy storage converter, including:

[0272] A data acquisition module 210, configured to acquire the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters;

[0273] A parameter determination module 220, configured to determine the direct-axis component and quadrature-axis component of the output voltage of the energy storage system based on the output voltage of the energy storage system, and determine the direct-axis component and quadrature-axis component of the output current of the energy storage system based on the output current of the energy storage system; and determine the active power, reactive power, and AC voltage amplitude of the energy storage system based on the output voltage and output current of the energy storage system;

[0274] A current determination module 230, configured to determine the maximum overload current of the grid-forming energy storage converter based on the maximum temperature of multiple battery clusters of the energy storage system and the output current;

[0275] A voltage drop determination module 240, configured to obtain the direct-axis equivalent voltage component and quadrature-axis equivalent voltage component of the energy storage system according to the virtual synchronous machine control strategy based on the direct-axis component of the output voltage of the energy storage system, quadrature-axis component of the output voltage, active power, reactive power, and AC voltage amplitude;

[0276] An impedance control module 250, configured to obtain the direct-axis virtual voltage drop and quadrature-axis virtual voltage drop of the energy storage system according to the virtual impedance control strategy based on the maximum overload current of the grid-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system;

[0277] A voltage subtraction module 260, configured to subtract the direct-axis virtual voltage drop of the energy storage system from the direct-axis equivalent voltage component of the energy storage system to obtain the reference value of the direct-axis component of the output voltage of the energy storage system, and subtract the quadrature-axis virtual voltage drop of the energy storage system from the quadrature-axis equivalent voltage component of the energy storage system to obtain the reference value of the quadrature-axis component of the output voltage of the energy storage system;

[0278] A first control module 270, configured to obtain the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system after PI control based on the reference value of the direct-axis component of the output voltage of the energy storage system, reference value of the quadrature-axis component of the output voltage, direct-axis component of the output voltage, and quadrature-axis component of the output voltage, and obtain the reference value of the output current of the energy storage system based on the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system;

[0279] The current calculation module 280 is used to obtain the output current direct-axis component limit value and the output current quadrature-axis component limit value of the energy storage system based on the maximum overload current of the grid-type energy storage converter and the output current direct-axis component reference value, the output current quadrature-axis component reference value and the output current reference value of the energy storage system when the output current reference value of the energy storage system is greater than the maximum overload current of the grid-type energy storage converter;

[0280] The second control module 290 is used to constrain the reference value of the output current direct-axis component of the energy storage system not to exceed the output current direct-axis component limit value of the energy storage system and to constrain the reference value of the output current quadrature-axis component of the energy storage system not to exceed the output current quadrature-axis component limit value of the energy storage system, obtain the final generated output current direct-axis component reference value and output current quadrature-axis component reference value of the energy storage system, and use the final generated output current direct-axis component reference value and output current quadrature-axis component reference value of the energy storage system as closed-loop control instructions of the current inner loop, and control the output current of the energy storage system to not exceed the maximum overload current of the grid-type energy storage inverter through the current inner loop and the modulation module.

[0281] It should be understood that the device corresponds to the above-mentioned embodiment of the hierarchical current limiting control method for the grid-type energy storage converter, and can execute the various steps involved in the above-mentioned method embodiment. The specific functions of the device can be found in the description above. To avoid repetition, the detailed description is appropriately omitted here. The device includes at least one software function module that can be stored in a memory in the form of software or firmware or solidified in the operating system (OS) of the device.

[0282] Embodiment 3

[0283] Based on the same inventive concept, an embodiment of the present invention also provides an electronic device, including: a processor and a memory, the memory storing machine-readable instructions executable by the processor, and the machine-readable instructions executing the above-mentioned grid-type energy storage inverter graded current limiting control method when the processor executes them.

[0284] In a typical configuration, an electronic device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0285] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0286] A computer-readable medium includes permanent and non-permanent, removable and non-removable media and can implement information storage by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer-readable medium does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0287] Embodiment 4

[0288] Based on the same inventive concept, an embodiment of the present invention also provides a computer-readable storage medium storing computer instructions, which, when run on a computer, cause the computer to execute the above-mentioned hierarchical current limiting control method for a network-forming energy storage converter.

[0289] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present 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.

[0290] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0291] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the block or blocks.

[0292] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, such that a series of operational steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the block or blocks.

[0293] It should be further noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the embodiments of the present invention do not separately describe various possible combinations.

[0294] In addition, each functional module in the embodiments of the present application can be integrated together to form an independent part, or each module can exist separately, or two or more modules can be integrated to form an independent part.

[0295] It should also be noted that the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus including a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or apparatus including the element.

[0296] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A hierarchical current limiting control method for a grid-forming energy storage converter, characterized in that, Including: S100, obtaining the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters; S200, determining the direct-axis component and quadrature-axis component of the output voltage of the energy storage system based on the output voltage of the energy storage system, and determining the direct-axis component and quadrature-axis component of the output current of the energy storage system based on the output current of the energy storage system; And determining the active power, reactive power, and AC voltage amplitude of the energy storage system based on the output voltage and output current of the energy storage system; S300; determining the maximum overload current of the grid-forming energy storage converter based on the maximum temperature and output current of multiple battery clusters of the energy storage system; S400, obtaining the equivalent direct-axis component and equivalent quadrature-axis component of the energy storage system according to the virtual synchronous machine control strategy based on the direct-axis component of the output voltage, quadrature-axis component of the output voltage, active power, reactive power, and AC voltage amplitude of the energy storage system; S500, obtaining the direct-axis virtual voltage drop and quadrature-axis virtual voltage drop of the energy storage system according to the virtual impedance control strategy based on the maximum overload current of the grid-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system; S600, subtracting the direct-axis virtual voltage drop of the energy storage system from the equivalent direct-axis component of the energy storage system to obtain the reference value of the direct-axis component of the output voltage of the energy storage system, and subtracting the quadrature-axis virtual voltage drop of the energy storage system from the equivalent quadrature-axis component of the energy storage system to obtain the reference value of the quadrature-axis component of the output voltage of the energy storage system; S700, obtaining the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system after PI control based on the reference value of the direct-axis component of the output voltage of the energy storage system, the reference value of the quadrature-axis component of the output voltage of the energy storage system, the direct-axis component of the output voltage, and the quadrature-axis component of the output voltage, and obtaining the reference value of the output current of the energy storage system based on the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system; S800, if the reference value of the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter, then obtaining the limit value of the direct-axis component of the output current of the energy storage system and the limit value of the quadrature-axis component of the output current of the energy storage system based on the maximum overload current of the grid-forming energy storage converter and the reference value of the direct-axis component of the output current of the energy storage system, the reference value of the quadrature-axis component of the output current of the energy storage system, and the reference value of the output current of the energy storage system; S900, restricting that the reference value of the direct-axis component of the output current of the energy storage system does not exceed the limit value of the direct-axis component of the output current of the energy storage system and restricting that the reference value of the quadrature-axis component of the output current of the energy storage system does not exceed the limit value of the quadrature-axis component of the output current of the energy storage system, obtaining the finally generated reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system, and using the finally generated reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current of the energy storage system as the closed-loop control command of the current inner loop, and controlling the output current of the energy storage system not to exceed the maximum overload current of the grid-forming energy storage converter through the current inner loop and the modulation module.

2. The hierarchical current limiting control method for a grid-forming energy storage converter according to claim 1, wherein Step S300 includes: S310. Based on a preset temperature range, delimit the current limit level for the maximum temperature of the battery cluster, and determine the current current limit level of the network-forming energy storage converter. S320. Determine whether the current current limit level of the network-forming energy storage converter is in an available state. S330. If so, based on the current current limit level of the network-forming energy storage converter, multiple preset overload capabilities, and multiple preset re-availability interval durations, determine the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the current current limit level. S340. If the output current of the energy storage system is greater than the maximum overload current of the network-forming energy storage converter at the current current limit level, start overcurrent timing. When the overcurrent timing duration is greater than the maximum continuous overcurrent duration of the network-forming energy storage converter at the current current limit level, increment the current current limit level of the network-forming energy storage converter, mark the current current limit level of the network-forming energy storage converter as unavailable, return to step S330, and at the same time start cooling timing. When the cooling timing duration is greater than the re-availability interval duration of the network-forming energy storage converter at the current current limit level, mark the current current limit level of the network-forming energy storage converter as available, and return to step S310. S350. If not, increment the current current limit level of the network-forming energy storage converter and return to step S320.

3. The hierarchical current limiting control method of the grid-forming energy storage converter according to claim 2, characterized in that Step S310 includes: Based on a preset temperature range and multiple preset temperature variables, delimit multiple temperature ranges of the battery cluster; where each temperature range corresponds to a different current limit level. By determining the temperature range of the battery cluster to which the maximum temperature of the battery cluster belongs, determine the current current limit level of the network-forming energy storage converter.

4. The hierarchical current limiting control method of the grid-forming energy storage converter according to claim 3, characterized in that The multiple preset temperature variables include: a first preset temperature variable, a second preset temperature variable, a third preset temperature variable, and a fourth preset temperature variable; the first preset temperature variable < the second preset temperature variable < the third preset temperature variable < the fourth preset temperature variable. Based on a preset temperature range and multiple preset temperature variables, delimiting multiple temperature ranges of the battery cluster includes: Taking the minimum value of the preset temperature range as the left endpoint of the range and the sum value of the minimum value of the preset temperature range and the first preset temperature variable as the right endpoint of the range, construct the first temperature range of the battery cluster, and determine that the current limit level of the first temperature range of the battery cluster is the first current limit level. Taking the sum value of the minimum value of the preset temperature range and the first preset temperature variable as the left endpoint of the range and the difference value between the maximum value of the preset temperature range and the first preset temperature variable as the right endpoint of the range, construct the second temperature range of the battery cluster, and determine that the current limit level of the second temperature range of the battery cluster is the second current limit level. Taking the difference value between the maximum value of the preset temperature range and the first preset temperature variable as the left endpoint of the range and the maximum value of the preset temperature range as the right endpoint of the range, construct the third temperature range of the battery cluster, and determine that the current limit level of the third temperature range of the battery cluster is the third current limit level. Taking the maximum value of the preset temperature range as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the second preset temperature variable as the right endpoint of the interval, construct the fourth temperature range of the battery cluster, and determine that the current limit level of the fourth temperature range of the battery cluster is the fourth current limit level; Taking the sum of the maximum value of the preset temperature range and the second preset temperature variable as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the third preset temperature variable as the right endpoint of the interval, construct the fifth temperature range of the battery cluster, and determine that the current limit level of the fifth temperature range of the battery cluster is the fifth current limit level; Taking the sum of the maximum value of the preset temperature range and the third preset temperature variable as the left endpoint of the interval, and the sum of the maximum value of the preset temperature range and the fourth preset temperature variable as the right endpoint of the interval, construct the sixth temperature range of the battery cluster, and determine that the current limit level of the sixth temperature range of the battery cluster is the sixth current limit level; Taking the sum of the maximum value of the preset temperature range and the fourth preset temperature variable as the left endpoint of the interval, construct the seventh temperature range of the battery cluster, and determine that the current limit level of the seventh temperature range of the battery cluster is the seventh current limit level.

5. The hierarchical current limiting control method of the grid-forming energy storage converter according to claim 2, wherein The multiple preset overload capabilities include: the first preset overload capability, the second preset overload capability, and the third preset overload capability; The first preset overload capability includes: the first overload current and the first maximum continuous overcurrent duration; the second preset overload capability includes: the second overload current and the second maximum continuous overcurrent duration; the third preset overload capability includes: the third overload current and the third maximum continuous overcurrent duration; The multiple preset re - available interval durations include: the first preset re - available interval duration, the second preset re - available interval duration, the third preset re - available interval duration, the fourth preset re - available interval duration, the fifth preset re - available interval duration, the sixth preset re - available interval duration, and the seventh preset re - available interval duration; The first overload current > the second overload current > the third overload current; the first maximum continuous overcurrent duration < the second maximum continuous overcurrent duration < the third maximum continuous overcurrent duration; the first preset re - available interval duration > the second preset re - available interval duration > the third preset re - available interval duration > the fourth preset re - available interval duration > the fifth preset re - available interval duration > the sixth preset re - available interval duration > the seventh preset re - available interval duration.

6. The hierarchical current limiting control method for a grid-forming energy storage converter according to claim 5, characterized in that, Step S320 includes: Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - available interval duration of the grid - forming energy storage converter under the first current limit level are the first overload current, the first maximum continuous overcurrent duration, and the first preset re - available interval duration respectively; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - available interval duration of the grid - forming energy storage converter under the second current limit level are the second overload current, the second maximum continuous overcurrent duration, and the second preset re - available interval duration respectively; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re - available interval duration of the grid - forming energy storage converter under the third current limit level are the third overload current, the third maximum continuous overcurrent duration, and the third preset re - available interval duration respectively; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the fourth current limit level are respectively the product of the third overload current and the first preset coefficient, the quotient of the third maximum continuous overcurrent duration and the first preset coefficient, and the fourth preset re-availability interval duration; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the fifth current limit level are respectively the product of the third overload current and the second preset coefficient, the quotient of the third maximum continuous overcurrent duration and the second preset coefficient, and the fifth preset re-availability interval duration; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the sixth current limit level are respectively the product of the third overload current and the third preset coefficient, the quotient of the third maximum continuous overcurrent duration and the third preset coefficient, and the sixth preset re-availability interval duration; Determine that the maximum overload current, the maximum continuous overcurrent duration, and the re-availability interval duration of the network-forming energy storage converter at the seventh current limit level are respectively the product of the third overload current and the fourth preset coefficient, the quotient of the third maximum continuous overcurrent duration and the fourth preset coefficient, and the seventh preset re-availability interval duration; Wherein, the first preset coefficient > the second preset coefficient > the third preset coefficient > the fourth preset coefficient.

7. The hierarchical current limiting control method for a grid-forming energy storage converter according to claim 1, characterized in that, Step S500 includes: Using the following formula, calculate the maximum overload current of the network-forming energy storage converter, the direct-axis component of the output current of the energy storage system, and the quadrature-axis component of the output current to obtain a current difference; Wherein, ΔI represents the current difference, id represents the direct-axis component of the output current of the energy storage system, iq represents the quadrature-axis component of the output current of the energy storage system, and I max represents the maximum overload current of the grid-forming energy storage converter; Calculate the product of the current difference, the preset gain, and the preset impedance control coefficient to obtain a virtual reactance; Respectively calculate the quotient of the virtual reactance and the preset impedance control coefficient and the angular frequency of the inverter output voltage to obtain a virtual resistance and a virtual inductor; Using the following formula, calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductor, the direct-axis component of the output current of the energy storage system, and the quadrature-axis component of the output current to obtain the direct-axis virtual voltage drop of the energy storage system; Among them, Δ ud represents the direct-axis virtual voltage drop of the energy storage system, Rv represents the virtual resistance, and Lv represents the virtual inductance, represents the angular frequency of the inverter output voltage; Using the following formula, calculate the virtual resistance, the angular frequency of the inverter output voltage, the virtual inductor, the direct-axis component of the output current of the energy storage system, and the quadrature-axis component of the output current to obtain the quadrature-axis virtual voltage drop of the energy storage system; Among them, Δ uq represents the quadrature-axis virtual voltage drop of the energy storage system.

8. The hierarchical current limiting control method of the network-forming energy storage converter according to claim 1, characterized in that, Step S800 includes: Respectively calculate the quotient of the reference value of the direct-axis component of the output current of the energy storage system and the reference value of the quadrature-axis component of the output current and the reference value of the output current to obtain the direct-axis direction cosine and the quadrature-axis direction sine of the energy storage system; Respectively calculate the product of the direct-axis direction cosine and the quadrature-axis direction sine of the energy storage system and the maximum overload current of the network-forming energy storage converter to obtain the limit value of the direct-axis component of the output current of the energy storage system and the limit value of the quadrature-axis component of the output current of the energy storage system.

9. A hierarchical current limiting control device for a grid-forming energy storage converter, characterized in that, It includes: A data acquisition module for acquiring the output voltage and output current of the energy storage system and the temperatures of multiple battery clusters; A parameter determination module for determining the direct-axis component and the quadrature-axis component of the output voltage of the energy storage system based on the output voltage of the energy storage system, and determining the direct-axis component and the quadrature-axis component of the output current of the energy storage system based on the output current of the energy storage system; Determine the active power, reactive power, and AC voltage amplitude of the energy storage system based on the output voltage and output current of the energy storage system; A current determination module, configured to determine the maximum overload current of the grid-forming energy storage converter based on the maximum temperature and output current of multiple battery clusters of the energy storage system; A voltage drop determination module, configured to obtain the direct-axis equivalent voltage component and quadrature-axis equivalent voltage component of the energy storage system according to the virtual synchronous machine control strategy based on the direct-axis component of the output voltage, quadrature-axis component of the output voltage, active power, reactive power, and AC voltage amplitude of the energy storage system; An impedance control module, configured to obtain the direct-axis virtual voltage drop and quadrature-axis virtual voltage drop of the energy storage system according to the virtual impedance control strategy based on the maximum overload current of the grid-forming energy storage converter and the direct-axis component and quadrature-axis component of the output current of the energy storage system; A voltage deduction module, configured to deduct the direct-axis virtual voltage drop of the energy storage system from the direct-axis equivalent voltage component of the energy storage system to obtain the reference value of the direct-axis component of the output voltage of the energy storage system, and deduct the quadrature-axis virtual voltage drop of the energy storage system from the quadrature-axis equivalent voltage component of the energy storage system to obtain the reference value of the quadrature-axis component of the output voltage of the energy storage system; A first control module, configured to obtain the reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system after PI control based on the reference value of the direct-axis component of the output voltage, reference value of the quadrature-axis component of the output voltage, direct-axis component of the output voltage, and quadrature-axis component of the output voltage of the energy storage system, and obtain the reference value of the output current of the energy storage system based on the reference value of the direct-axis component of the output current and the reference value of the quadrature-axis component of the output current of the energy storage system; A current calculation module, configured to, when the reference value of the output current of the energy storage system is greater than the maximum overload current of the grid-forming energy storage converter, obtain the limit value of the direct-axis component of the output current and the limit value of the quadrature-axis component of the output current of the energy storage system based on the maximum overload current of the grid-forming energy storage converter, the reference value of the direct-axis component of the output current, the reference value of the quadrature-axis component of the output current, and the reference value of the output current of the energy storage system; A second control module, configured to constrain the reference value of the direct-axis component of the output current of the energy storage system not to exceed the limit value of the direct-axis component of the output current of the energy storage system and constrain the reference value of the quadrature-axis component of the output current of the energy storage system not to exceed the limit value of the quadrature-axis component of the output current of the energy storage system, obtain the finally generated reference value of the direct-axis component of the output current and the finally generated reference value of the quadrature-axis component of the output current of the energy storage system, and use the finally generated reference value of the direct-axis component of the output current and the finally generated reference value of the quadrature-axis component of the output current of the energy storage system as the closed-loop control instruction of the current inner loop, and control the output current of the energy storage system not to exceed the maximum overload current of the grid-forming energy storage converter through the current inner loop and the modulation module.

10. An electronic device, characterized in that, Including: A processor and a memory, where the memory stores machine-readable instructions executable by the processor, and when the machine-readable instructions are executed by the processor, the grid-forming energy storage converter hierarchical current limiting control method according to any one of claims 1-8 is executed.

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