A method and system for determining the short-circuit current of a grid-forming energy storage system device

Abstract

The present invention relates to the technical field of short-circuit current measurement, and discloses a method and system for determining the short-circuit current of a network-forming energy storage system device. The method includes obtaining pre-fault data of a target power grid; calculating the inverter capacity according to the pre-fault data; calculating an operation mode transfer coefficient according to the inverter capacity; calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data; calculating the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity; and summing the short-circuit current of the target power grid after the short circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the network-forming energy storage system device. The method can achieve accurate calculation of the short-circuit current and improve the real-time performance and accuracy of short-circuit current measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of short-circuit current measurement, and particularly to a method and system for determining the short-circuit current of a network-forming energy storage system device. Background Art

[0002] An energy storage system refers to a new type of power system composed of an energy conversion device, an electric energy conversion device, an energy storage device, a monitoring and auxiliary system, etc., which can realize periodic or non-periodic electrical energy storage or electrical energy conversion. The development of energy storage systems will give rise to a large number of innovations in power applications, bringing about the coordinated development of the power generation, grid, load, energy storage, and transportation ends of the power system, thus creating a future power network system with perfect functions, flexibility, and high efficiency.

[0003] Nowadays, determining the short-circuit current in a power grid energy storage system is of great significance. It is directly related to the safety of the system, the protection ability of equipment, and the design requirements of the system, ensuring that the current can be quickly cut off when a short circuit occurs, preventing equipment damage, fire, or more serious faults. Existing power grid short-circuit current measurement technologies include converting large currents into small current signals that are easy to measure through current transformers for monitoring short-circuit currents. However, existing measurement methods also have deficiencies. Traditional current transformers cannot accurately and timely capture the current peak when facing rapidly occurring short-circuit situations, and when the short-circuit current is too high, the sensors and transformers will saturate, resulting in distorted measurement results. Summary of the Invention

[0004] The present invention provides a method and system for determining the short-circuit current of a network-forming energy storage system device, which can combine target power grid data, inverter capacity, and operation mode transfer coefficient to achieve accurate calculation of short-circuit current and improve the real-time performance and accuracy of short-circuit current measurement.

[0005] In the first aspect, to solve the above technical problems, the present invention provides a method for determining the short-circuit current of a network-forming energy storage system device, including: obtaining pre-fault data of a target power grid; wherein, the pre-fault data includes pre-fault node voltage phasors, pre-fault short-circuit current, and pre-fault fault point voltage phasors;

[0006] Calculating the inverter capacity according to the pre-fault data;

[0007] Calculating the operation mode transfer coefficient according to the inverter capacity;

[0008] Calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data;

[0009] Calculating the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity;

[0010] Sum the short - circuit current of the target power grid after the short - circuit and the short - circuit current of the energy storage system to obtain the short - circuit current of the grid - forming energy storage system equipment.

[0011] Preferably, calculating the inverter capacity according to the pre - fault data includes:

[0012] Calculate the inverter capacity through the following formula:

[0013] , where is the overload factor; is the short - circuit current before the fault; is the pre - fault node voltage phasor; is the pre - fault fault point voltage phasor; is the inverter capacity.

[0014] Preferably, calculating the operation mode transfer coefficient according to the inverter capacity includes:

[0015] Calculate the operation mode transfer coefficient through the following formula:

[0016] , where is the inverter capacity; is the impedance of the target power grid; is the overload factor; is the operation mode transfer coefficient.

[0017] Preferably, calculating the short - circuit current of the energy storage system according to the operation mode transfer coefficient and the pre - fault data includes:

[0018] Calculate the short - circuit current of the energy storage system through the following formula:

[0019] , where is the short - circuit current before the fault; is the operation mode transfer coefficient; is the energy storage system regulation coefficient; is the short - circuit current of the energy storage system.

[0020] Preferably, the energy storage system regulation coefficient is calculated in the following way:

[0021] Calculate the post - short - circuit fault point voltage phasor according to the pre - fault data, the short - circuit current of the energy storage system and the operation mode transfer coefficient;

[0022] Calculate the energy storage system regulation coefficient according to the post - short - circuit fault point voltage phasor and the pre - fault data.

[0023] Preferably, calculating the post - short - circuit fault point voltage phasor according to the pre - fault data, the short - circuit current of the energy storage system, and the operation mode transfer coefficient includes:

[0024] Calculating the post - short - circuit fault point voltage phasor through the following formula:

[0025] , where is the pre - fault node voltage phasor; is the pre - fault short - circuit current; is the short - circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target power grid; is the post - short - circuit fault point voltage phasor.

[0026] Preferably, calculating the energy storage system regulation coefficient according to the post - short - circuit fault point voltage phasor and the pre - fault data includes:

[0027] Calculating the energy storage system regulation coefficient through the following formula:

[0028] , where is the post - short - circuit fault point voltage phasor; is the pre - fault node voltage phasor; is the pre - fault short - circuit current; is the impedance of the target power grid.

[0029] Preferably, calculating the short - circuit current of the target power grid after short - circuit according to the pre - fault data and the inverter capacity includes:

[0030] Calculating the short - circuit current of the target power grid after short - circuit through the following formula:

[0031] , where is the pre - fault short - circuit current; is the inverter capacity; is the overload coefficient; is the impedance of the target power grid.

[0032] In a second aspect, the present invention provides a system for determining the short - circuit current of a network - forming energy storage system device, including:

[0033] A data acquisition module, configured to acquire pre - fault data of a target power grid;

[0034] An inverter capacity calculation module, configured to calculate the inverter capacity according to the pre - fault data;

[0035] A transfer coefficient calculation module, configured to calculate the operation mode transfer coefficient according to the inverter capacity;

[0036] A short - circuit current calculation module for an energy storage system, which is used to calculate the short - circuit current of the energy storage system according to the operation mode transfer coefficient and the pre - fault data;

[0037] A short - circuit current calculation module for the target power grid after a short - circuit, which is used to calculate the short - circuit current of the target power grid after a short - circuit according to the pre - fault data and the inverter capacity;

[0038] A short - circuit current calculation module for a grid - forming energy storage system device, which is used to sum the short - circuit current of the target power grid after a short - circuit and the short - circuit current of the energy storage system to obtain the short - circuit current of the grid - forming energy storage system device.

[0039] In a third aspect, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the method for determining the short - circuit current of a grid - forming energy storage system device described in any one of the above is implemented.

[0040] In a fourth aspect, the present invention also provides a computer - readable storage medium, which includes a stored computer program. When the computer program runs, the device where the computer - readable storage medium is located is controlled to execute the method for determining the short - circuit current of a grid - forming energy storage system device described in any one of the above.

[0041] Compared with the prior art, the present invention has the following beneficial effects: The embodiments of the present invention provide a method and a system for determining the short - circuit current of a grid - forming energy storage system device. The method includes: obtaining pre - fault data of a target power grid; where the pre - fault data includes pre - fault node voltage phasors, pre - fault short - circuit currents, and pre - fault fault - point voltage phasors; calculating the inverter capacity according to the pre - fault data; calculating the operation mode transfer coefficient according to the inverter capacity; calculating the short - circuit current of the energy storage system according to the operation mode transfer coefficient and the pre - fault data; calculating the short - circuit current of the target power grid after a short - circuit according to the pre - fault data and the inverter capacity; and summing the short - circuit current of the target power grid after a short - circuit and the short - circuit current of the energy storage system to obtain the short - circuit current of the grid - forming energy storage system device.

[0042] In the present invention, the method can calculate the inverter capacity by acquiring the pre-fault data of the target power grid, further calculate the operation mode transfer coefficient using the inverter capacity, and thus determine the short-circuit current of the energy storage system in combination with the pre-fault data. Then, calculate the short-circuit current of the target power grid after the short circuit based on the pre-fault data and the inverter capacity. Finally, sum the short-circuit current of the energy storage system and the short-circuit current of the target power grid after the short circuit to obtain the short-circuit current of the network-forming energy storage system equipment. The beneficial effect of the method is that it can achieve accurate calculation of the short-circuit current and improve the real-time performance and accuracy of short-circuit current measurement. Brief Description of the Drawings

[0043] Figure 1 is a schematic flowchart of a method for determining the short-circuit current of network-forming energy storage system equipment provided by the first embodiment of the present invention;

[0044] Figure 2 is a schematic structural diagram of a system for determining the short-circuit current of network-forming energy storage system equipment provided by the second embodiment of the present invention. Detailed Embodiments

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Referring to Figure 1 , the first embodiment of the present invention provides a method for determining the short-circuit current of network-forming energy storage system equipment, including the following steps:

[0047] S11, acquire the pre-fault data of the target power grid.

[0048] S12, calculate the inverter capacity according to the pre-fault data.

[0049] S13, calculate the operation mode transfer coefficient according to the inverter capacity.

[0050] S14, calculate the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data.

[0051] S15, calculate the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity.

[0052] S16, sum the short-circuit current of the target power grid after the short circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the network-forming energy storage system equipment.

[0053] It should be noted that an energy storage system refers to a new type of power system composed of an energy conversion device, an electric energy conversion device, an energy storage device, a monitoring and auxiliary system, etc., which can realize periodic or non-periodic electrical energy storage or electrical energy conversion. The development of energy storage systems will give rise to a large number of innovations in power applications, bringing about the coordinated development of the power generation, grid, load, storage, and transportation in the power system, thus creating a future power network system with perfect functions, flexibility, and high efficiency.

[0054] Nowadays, it is of great significance to determine the short-circuit current in the grid energy storage system. It is directly related to the safety of the system, the protection ability of equipment, and the design requirements of the system, ensuring that the current can be quickly cut off when a short circuit occurs, preventing equipment damage, fire, or more serious faults.

[0055] To facilitate the understanding of the present invention, some preferred embodiments of the present invention will be further described below.

[0056] In step S11, the pre-fault data of the target grid is obtained.

[0057] Preferably, the pre-fault data includes the pre-fault node voltage phasor, the pre-fault short-circuit current, and the pre-fault fault point voltage phasor.

[0058] Specifically, the node voltage phasor refers to the voltage amplitude and phase information of a certain node in the target grid before a fault. The method for obtaining it can be to install a high-precision voltage sensor at the node to measure the voltage in real time and record its amplitude and phase angle, or it can be combined with a data acquisition system (such as SCADA) to store the voltage data measured by the sensor in phasor form. The node voltage phasor provides basic data for determining the stable operation state and pre-fault operation characteristics of the grid, and is used to calculate the dynamic changes of the grid when a fault occurs.

[0059] Specifically, the pre-fault short-circuit current refers to the short-circuit current value that occurs under the normal operation state of the grid, reflecting the load and current-carrying characteristics of the circuit. The method for obtaining it can be to install current transformers at key lines in the grid to monitor and record the value of the current flowing through in real time, especially the short-circuit situation under peak system load or specific scenarios, or it can be the short-circuit current situation extracted from the historical data of the grid operation, combined with the actual working conditions for evaluation. The pre-fault short-circuit current is used to calculate the fault response in the energy storage system and is an important basis for evaluating the effectiveness of protection measures.

[0060] Specifically, the pre-fault voltage phasor at the fault point refers to the voltage phasor information at the fault point when the fault is about to occur, including the amplitude and phase angle of the voltage. The acquisition method can be to install measuring equipment at the location where the fault occurs in the power grid, monitor and record the voltage phasor data in real time. It is also possible to use a data storage and analysis system to retrieve the voltage data at the fault point after the fault occurs to obtain the voltage state before the fault. The pre-fault voltage phasor at the fault point is used to accurately describe the voltage state of the power grid before the fault and plays an important role in subsequent short-circuit current calculation and fault handling.

[0061] It should be noted that the pre-fault short-circuit current refers to the "estimated short-circuit current under normal operating conditions" before the system fault is about to occur, which is calculated by the current and load conditions under normal operating conditions to obtain the short-circuit current generated by the fault. It is a prediction and pre-analysis of the current change after the fault, not the short-circuit current when the fault actually occurs. By analyzing the pre-fault operating state of the power grid (node voltage, current flowing through normal loads), the magnitude of the short-circuit current that will occur after the fault can be predicted and evaluated, providing a reference for system design and protection. This can estimate in advance the magnitude of the current impact on the power system and ensure that the system design meets safety requirements.

[0062] In step S12, the inverter capacity is calculated according to the pre-fault data.

[0063] Preferably, the calculating the inverter capacity according to the pre-fault data includes:

[0064] The inverter capacity is calculated by the following formula:

[0065] , where is the overload factor; is the pre-fault short-circuit current; is the pre-fault node voltage phasor; is the pre-fault voltage phasor at the fault point; is the inverter capacity.

[0066] It should be noted that the inverter capacity refers to the maximum power or energy output capacity that the inverter can handle or convert, expressed in power units such as kilowatts (kW) or megawatts (MW). It reflects the maximum output capacity of the inverter when converting direct current to alternating current, or the maximum current or power response that the inverter can provide under special circumstances such as grid short - circuit. In the present invention, the concept of inverter capacity is closely related to determining the short - circuit current of the grid - forming energy storage system equipment. It represents the maximum power or current output capacity that the energy storage system can provide in the face of a short - circuit fault and is one of the important parameters for evaluating and calculating the system response ability. By calculating the inverter capacity, the impact and contribution of the energy storage system under short - circuit conditions can be better evaluated, thereby accurately determining the overall short - circuit current response of the system. Specifically, the calculation of the inverter capacity is based on pre - fault data (such as pre - fault node voltage and short - circuit current, etc.), and the results are used in subsequent steps to calculate the operation mode transfer coefficient and the short - circuit current of the energy storage system. The inverter capacity determines the load - bearing capacity and response ability of the energy storage system and is an essential core parameter in the entire short - circuit current calculation process. It ensures that the energy storage system can accurately adjust its output under different operating conditions and has an important impact on the short - circuit current of the power grid.

[0067] Specifically, is the overload coefficient, which represents the coefficient of the maximum load - bearing capacity and the expected load - bearing capacity during system operation. It reflects the coefficient of the maximum load that the inverter bears under fault conditions compared to the normal operating state. Its function is to adjust and correct the calculation results to reflect the overload situation in the actual operating environment and ensure that the system has sufficient margin and stability. Exemplarily, the value of the overload coefficient is a positive number, and the specific value is determined according to the design requirements and operating conditions of the system. Generally, the typical value range is between 1.1 and 1.5. For example, represents that the system can withstand an additional 20% load capacity based on the normal load. In different application scenarios, the value will vary. If the system requires higher fault - tolerance or a larger load adjustment margin, a larger overload coefficient will be used. is the pre - fault short - circuit current, which refers to the value of the current flow in the system before the fault occurs, expressed as the estimated short - circuit current. It serves as a basic parameter to reflect the current situation before the fault and provides initial conditions for evaluating the system response after the fault. is the pre - fault node voltage phasor, which represents the voltage amplitude and phase angle of a certain node in the target power grid before the fault occurs, reflecting the electrical state of the node. It is used to calculate the stable operating state of the system and provides a reference for the calculation of the short - circuit current. is the pre - fault fault - point voltage phasor, which represents the voltage phasor information of the fault point before the fault occurs, including its amplitude and phase. It reflects the electrical state of the fault point before the fault and helps to evaluate the voltage distribution and electrical changes in the system. is the inverter capacity, which is the calculated value of the inverter capacity and reflects the load capacity of the inverter before and after a fault. It provides an input value for subsequent calculations of the operation mode transfer coefficient and the system short-circuit current, and serves as an indicator of the system's load-bearing and response capabilities.

[0068] After the inverter capacity is calculated, it is used to calculate the operation mode transfer coefficient, which can be further used to evaluate the short-circuit current of the energy storage system.

[0069] In step S13, the operation mode transfer coefficient is calculated according to the inverter capacity.

[0070] Preferably, the calculating the operation mode transfer coefficient according to the inverter capacity includes:

[0071] The operation mode transfer coefficient is calculated by the following formula:

[0072] , where is the inverter capacity; is the impedance of the target power grid; is the overload coefficient; is the operation mode transfer coefficient.

[0073] Specifically, is the impedance of the target power grid. The impedance of the target power grid refers to the network impedance value connected to the system, which reflects the current distribution and impedance characteristics in the power grid and is used to calculate the operation mode transfer coefficient, considering the influence of the electrical characteristics of the power grid on the short-circuit current distribution and regulation. Specifically, can be measured in the following ways: impedance measurement method, by introducing a known current signal into the power grid and measuring the voltage change caused thereby to calculate the impedance. A transformer or reactor is used as the signal source to inject a signal into the system. The specific steps are as follows: First, inject a test current with a known amplitude and frequency into the power grid. Then, use a voltage sensor to measure the voltage changes at the injection point and its nearby nodes. Finally, calculate the impedance value through Ohm's law. This method is applicable to scenarios where the power grid load is relatively stable or the introduction of test signals is allowed; short-circuit test method, conduct a controlled short-circuit test under safe conditions and calculate the power grid impedance through the fault current and the corresponding voltage drop. Exemplarily, the measurement steps can be to cause a short-circuit fault under controlled conditions, record the current and voltage during the short circuit, and use the formula , where is the voltage during the short circuit, is the short - circuit current; The harmonic injection method utilizes the non - linear characteristics of the system. By injecting harmonic signals of specific frequencies and measuring the system's response to these harmonics, the grid impedance is estimated. The steps are to inject a harmonic signal of a known frequency into the grid, record the voltage and current changes generated by the system response, and calculate the harmonic impedance of the grid by analyzing the changes in the harmonic frequency components. This method is suitable for measurement in an operating system without interrupting the system operation.

[0074] It should be noted that is the operation mode transfer coefficient, which is used to describe the system's ability to regulate the load and short - circuit current under different operating states. The operation mode transfer coefficient is used in the subsequent steps to calculate the short - circuit current of the energy storage system. It is a regulation parameter of the grid operating state and reflects the system's response ability under different working conditions.

[0075] In step S14, according to the operation mode transfer coefficient and the pre - fault data, calculate the short - circuit current of the energy storage system.

[0076] Preferably, the calculating the short - circuit current of the energy storage system according to the operation mode transfer coefficient and the pre - fault data includes:

[0077] Calculate the short - circuit current of the energy storage system through the following formula:

[0078] , where is the short - circuit current before the fault; is the operation mode transfer coefficient; is the energy storage system regulation coefficient; is the short - circuit current of the energy storage system.

[0079] It should be noted that is the energy storage system regulation coefficient, which needs to be obtained through joint calculation in subsequent steps. The energy storage system regulation coefficient is a parameter used to adjust and describe the energy storage system's response ability to short - circuit current in the face of grid faults or other changes. It analyzes and corrects the operation of the energy storage system under fault conditions to help achieve accurate calculation of the short - circuit current of the energy storage system. Simply put, it is a coefficient used to reflect how the energy storage system dynamically adjusts the short - circuit current output under different states. The response of the energy storage system during a grid fault is not fixed but is affected by various factors (such as pre - fault data, operation mode, etc.). The regulation coefficient can reflect the specific performance of the energy storage system in this dynamic change and help more accurately describe the actual value of the system short - circuit current. When calculating the short - circuit current of the energy storage system, the regulation coefficient is used to adjust and correct the calculation result so that the obtained short - circuit current can more realistically reflect the current output of the energy storage system under fault conditions. This adjustment needs to be based on a comprehensive consideration of system characteristics, operation mode, and external factors.

[0080] Preferably, the regulation coefficient of the energy storage system is calculated in the following manner:

[0081] Calculate the post-fault voltage phasor at the fault point according to the pre-fault data, the short-circuit current of the energy storage system, and the operation mode transfer coefficient;

[0082] Calculate the regulation coefficient of the energy storage system according to the post-fault voltage phasor at the fault point and the pre-fault data.

[0083] Specifically, this step is a combined calculation step, and the short-circuit current of the energy storage system here needs to be obtained through combined calculation with the above steps.

[0084] Preferably, calculating the post-fault voltage phasor at the fault point according to the pre-fault data, the short-circuit current of the energy storage system, and the operation mode transfer coefficient includes:

[0085] Calculate the post-fault voltage phasor at the fault point through the following formula:

[0086] , where in the formula, is the pre-fault node voltage phasor; is the pre-fault short-circuit current; is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target power grid; is the post-fault voltage phasor at the fault point.

[0087] Specifically, in the formula, first, the pre-fault node voltage phasor is used as a reference, which is the voltage state of the power grid before the short circuit occurs and provides a reference point for the changes after the short circuit. The adjustment coefficient and the interaction of other parameters indicate the response of the system under the short-circuit state, including the influence of current and the regulation of impedance factors. represents the ratio adjustment of the impedance influence, thus affecting the final post-short-circuit voltage result. represents the short-circuit current and the difference between the short-circuit current of the energy storage system , representing the adjustment or change range of the current. In the calculation method shown in the present invention, the combined effect of the calculation results will adjust the voltage state after the fault. By multiplying the adjusted current difference term by the regulation coefficient and the fractional term and adding it to , the voltage state at the fault point of the system after the short circuit is obtained. The post-fault voltage phasor at the fault point describes the voltage change situation of the system after the short circuit.

[0088] Preferably, calculating the regulation coefficient of the energy storage system according to the post-fault voltage phasor at the fault point and the pre-fault data includes:

[0089] The regulation coefficient of the energy storage system is calculated by the following formula:

[0090] , where is the voltage phasor at the fault point after the short circuit; is the node voltage phasor before the fault; is the short-circuit current before the fault; is the impedance of the target power grid.

[0091] It should be noted that this step and the above steps are combined calculation steps. By jointly calculating with three formulas, the regulation coefficient of the energy storage system, the voltage phasor at the fault point after the short circuit, and the short-circuit current of the energy storage system can be obtained.

[0092] In step S15, according to the pre-fault data and the inverter capacity, calculate the short-circuit current of the target power grid after the short circuit.

[0093] Preferably, the calculating the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity includes:

[0094] The short-circuit current of the target power grid after the short circuit is calculated by the following formula:

[0095] , where is the short-circuit current before the fault; is the inverter capacity; is the overload coefficient; is the impedance of the target power grid.

[0096] Specifically, is the calculated short-circuit current of the target power grid. It represents the short-circuit current calculated under specific conditions and is the current after the power grid short circuit. is the short-circuit current before the fault, representing the current state of the system before the short circuit occurs and is the reference current for calculating the short circuit. is the inverter capacity, reflecting the load capacity of the inverter in the energy storage system in the power grid and its influence on the short-circuit current. is the impedance of the target power grid, describing the impedance characteristics of the current path in the power grid, reflecting the distribution of current in the network and the resistance it encounters. The calculation of the current after the short circuit starts from the short-circuit current before the fault as the base value, representing the current state of the system before the short circuit occurs. It is a correction term affected by the inverter capacity, representing the correction or influence of the inverter capacity on the short-circuit current. The contribution of the inverter capacity is adjusted through the adjustment coefficient and the grid impedance. Specifically, the inverter capacity affects the current distribution and response of the system during a short circuit. The adjustment coefficient is used to regulate the influence of the inverter on the current and is a coefficient related to the load capacity or system configuration. The impedance describes the current distribution characteristics in the system grid. The current output by the inverter is affected by the grid impedance, resulting in different degrees of response during a short circuit. The finally calculated short-circuit current is determined by subtracting the correction term affected by the inverter, representing the short-circuit current response after considering the inverter capacity and grid characteristics. This calculation method can help reflect the regulating effect of the inverter on the system current during a short-circuit event and its influence on the overall system stability.

[0097] It should be noted that the short-circuit current of the target grid after a short circuit refers to the short-circuit current generated by the target grid itself after a short-circuit fault occurs in the grid. It is calculated based on the pre-fault data of the grid (such as the short-circuit current and inverter capacity before the fault), reflecting the current response ability of the grid itself under short-circuit conditions. The short-circuit current of the target grid after a short circuit is determined by the characteristics of each electrical component and system within the grid, and it represents the main current characteristics of the grid under short-circuit conditions. The short-circuit current of the energy storage system refers to the short-circuit current generated by the energy storage system under short-circuit conditions. As an independent power source or power regulation device, the energy storage system will provide a certain current response when the grid experiences a short circuit. The calculation of the short-circuit current of the energy storage system is based on parameters such as the operation mode transfer coefficient, the energy storage system regulation coefficient, and pre-fault data, describing the degree of participation and contribution of the energy storage system to the short-circuit event. In the power system, the short-circuit currents of the grid and the energy storage system are regarded as parallel current sources. When a short circuit occurs in the system, these current sources will all contribute to the short-circuit current. According to the superposition principle of the electrical system, the total current of multiple parallel current sources is the sum of the individual source currents. Therefore, in order to accurately describe the overall short-circuit response of the system, it is necessary to sum the short-circuit currents of the target grid and the energy storage system.

[0098] In step S16, the short-circuit current of the target grid after a short circuit and the short-circuit current of the energy storage system are summed to obtain the short-circuit current of the grid-forming energy storage system device.

[0099] In the method for determining the short-circuit current of a grid-forming energy storage system device, after calculating the short-circuit current of the target power grid and the short-circuit current of the energy storage system after a short circuit, the last step is to sum these two short-circuit currents to obtain the total short-circuit current of the grid-forming energy storage system device. Among them, the short-circuit current of the target power grid after a short circuit is calculated based on the pre-fault data and the inverter capacity. The short-circuit current of the target power grid after a short circuit describes the current value generated by the power grid when a short circuit occurs and is one of the main parameters of the power grid short-circuit state. The short-circuit current of the energy storage system is calculated through parameters such as the operation mode transfer coefficient and the energy storage system regulation coefficient. It reflects the short-circuit current generated by the energy storage system under short-circuit conditions and indicates the contribution and response ability of the energy storage system to the power grid short-circuit current. Summing the short-circuit current of the target power grid after a short circuit and the short-circuit current of the energy storage system yields the total short-circuit current of the grid-forming energy storage system device.

[0100] Specifically, the total short-circuit current obtained by summing reflects the overall current situation of the entire grid-forming energy storage system under short-circuit conditions. It combines the short-circuit currents of both the power grid and the energy storage system, providing a global short-circuit current evaluation value. Calculating the total short-circuit current is of great significance for the design of the system and the selection of short-circuit protection devices. It determines the electrical stress level of the system when a short circuit occurs, thus helping to determine the required protection measures (such as the capacity of the circuit breaker).

[0101] It should be noted that the short - circuit current of the grid - forming energy storage system equipment is obtained by summing the short - circuit current of the target power grid after short - circuit and the short - circuit current of the energy storage system, mainly based on the following physical and electrical principles: In a power system, when a short - circuit occurs, all current sources connected in parallel will participate and contribute to the short - circuit current. The short - circuit current of the target power grid and the short - circuit current of the energy storage system are equivalent to multiple parallel current sources at the short - circuit point, and their contributions will be superimposed. Therefore, by adding their current values, the total short - circuit current of the entire system can be obtained. This reflects the overall response of the system under short - circuit conditions and is the combined influence of all current sources in the grid - forming energy storage system on the total short - circuit current during a power grid short - circuit. At the same time, a grid - forming energy storage system refers to a combined operation system of energy storage equipment and the power grid. Under short - circuit conditions, the energy storage system will also participate in the formation and response of the short - circuit current according to its control strategy, operation mode, and electrical characteristics. Summing reflects the joint response of the energy storage system and the power grid to the short - circuit situation and is an expression of the overall system's comprehensive short - circuit behavior. To design the system and evaluate its safety, it is necessary to know the magnitude of the total current during short - circuit. Considering only the short - circuit current of the target power grid or only the short - circuit current of the energy storage system alone cannot accurately reflect the electrical stress level of the entire system. The total short - circuit current after summation provides the maximum current value of the system under short - circuit conditions and can be used to determine the capacity of the protection device and select appropriate protection measures. From a physical perspective, both the power grid and the energy storage system provide current paths. When a short - circuit occurs, all current paths will contribute current. The total short - circuit current is the sum of all paths, reflecting the short - circuit current distribution and response characteristics of the entire system. Therefore, in the present invention, summing the short - circuit current of the target power grid after short - circuit and the short - circuit current of the energy storage system can accurately describe the total current response of the grid - forming energy storage system equipment under short - circuit conditions, based on the superposition of parallel current sources, the unified representation of physical phenomena, and the need for a simplified analysis model. This method provides the short - circuit current performance of the entire system and provides important basic data for the design and operation of the system.

[0102] The working process of the present invention is described below by taking a relatively common scenario as an example. The working process is as follows:

[0103] A grid - forming energy storage system is connected to a power grid system. Suddenly, a short - circuit fault occurs in the power grid. At this time, it is necessary to determine the total short - circuit current of the entire system (including the power grid and the energy storage system) under such short - circuit conditions to ensure the safety and stability of the system and take corresponding protection measures.

[0104] First, the system collects the pre-fault data of the target power grid, including the voltage phasors of the nodes, the short-circuit current before the fault, and the voltage phasor of the fault point before the fault. These data are used to describe the electrical state of the system before the short circuit occurs. Based on the obtained pre-fault data, the capacity of the inverter in the energy storage system is calculated. The inverter capacity is an important parameter for the energy storage system to respond to the short circuit and determines the output ability of the energy storage system.

[0105] Using the calculated inverter capacity and combining with the power grid impedance parameters, the operation mode transfer coefficient is determined. This coefficient reflects the adjustment ability of the energy storage system to the load and short-circuit current under different operation states.

[0106] Using the operation mode transfer coefficient and the pre-fault data, the short-circuit current of the energy storage system under the short-circuit condition is calculated. This step can determine the response of the energy storage system to the power grid when the short circuit occurs.

[0107] Combining the pre-fault data and the inverter capacity, the short-circuit current of the target power grid after the short circuit is calculated. This value represents the current change situation of the power grid part under the short-circuit state.

[0108] Finally, the short-circuit current of the target power grid after the short circuit and the short-circuit current of the energy storage system are summed up to obtain the total short-circuit current of the grid-forming energy storage system equipment. This total short-circuit current is used to reflect the overall response of the entire system under the short-circuit condition.

[0109] In summary, the present invention provides a method for determining the short-circuit current of grid-forming energy storage system equipment, including: obtaining the pre-fault data of the target power grid; wherein, the pre-fault data includes the pre-fault node voltage phasor, the pre-fault short-circuit current, and the pre-fault voltage phasor of the fault point;

[0110] Calculating the inverter capacity according to the pre-fault data;

[0111] Calculating the operation mode transfer coefficient according to the inverter capacity;

[0112] Calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data;

[0113] Calculating the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity;

[0114] Summing up the short-circuit current of the target power grid after the short circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the grid-forming energy storage system equipment.

[0115] In the present invention, the method can calculate the inverter capacity by acquiring the pre-fault data of the target power grid, further calculate the operation mode transfer coefficient by using the inverter capacity, and thus determine the short-circuit current of the energy storage system in combination with the pre-fault data. Then, calculate the short-circuit current of the target power grid after the short circuit through the pre-fault data and the inverter capacity. Finally, sum up the short-circuit current of the energy storage system and the short-circuit current of the target power grid after the short circuit to obtain the short-circuit current of the network-forming energy storage system equipment. The beneficial effect of the method is that it can achieve accurate calculation of the short-circuit current and improve the real-time performance and accuracy of short-circuit current measurement.

[0116] Referring to Figure 2 , the second embodiment of the present invention provides a system for determining the short-circuit current of network-forming energy storage system equipment, including:

[0117] A data acquisition module for acquiring pre-fault data of the target power grid;

[0118] An inverter capacity calculation module for calculating the inverter capacity according to the pre-fault data;

[0119] A transfer coefficient calculation module for calculating the operation mode transfer coefficient according to the inverter capacity;

[0120] An energy storage system short-circuit current calculation module for calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data;

[0121] A short-circuit current calculation module of the target power grid after the short circuit for calculating the short-circuit current of the target power grid after the short circuit according to the pre-fault data and the inverter capacity;

[0122] A short-circuit current calculation module of the network-forming energy storage system equipment for summing up the short-circuit current of the target power grid after the short circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the network-forming energy storage system equipment.

[0123] In an optional implementation manner, the inverter capacity calculation module is specifically used for:

[0124] Calculating the inverter capacity through the following formula:

[0125] , where is the overload coefficient; is the short-circuit current before the fault; is the pre-fault node voltage phasor; is the pre-fault fault point voltage phasor; is the inverter capacity.

[0126] In an optional implementation manner, the transfer coefficient calculation module is specifically used for:

[0127] Calculate the operation mode transfer coefficient through the following formula:

[0128] , where is the inverter capacity; is the impedance of the target power grid; is the overload coefficient; is the operation mode transfer coefficient.

[0129] In an alternative embodiment, the energy storage system short-circuit current calculation module is specifically configured to:

[0130] Calculate the energy storage system short-circuit current through the following formula:

[0131] , where is the short-circuit current before the fault; is the operation mode transfer coefficient; is the energy storage system regulation coefficient; is the energy storage system short-circuit current.

[0132] In an alternative embodiment, the energy storage system short-circuit current calculation module is specifically configured to:

[0133] Calculate the voltage phasor at the fault point after the short circuit according to the pre-fault data, the energy storage system short-circuit current, and the operation mode transfer coefficient;

[0134] Calculate the energy storage system regulation coefficient according to the voltage phasor at the fault point after the short circuit and the pre-fault data.

[0135] In an alternative embodiment, the energy storage system short-circuit current calculation module is specifically configured to:

[0136] Calculate the voltage phasor at the fault point after the short circuit through the following formula:

[0137] , where is the pre-fault node voltage phasor; is the pre-fault short-circuit current; is the energy storage system short-circuit current; is the operation mode transfer coefficient; is the impedance of the target power grid; is the voltage phasor at the fault point after the short circuit.

[0138] In an alternative embodiment, the energy storage system short-circuit current calculation module is specifically configured to:

[0139] Calculate the energy storage system regulation coefficient through the following formula:

[0140] , where is the voltage phasor at the fault point after short - circuit; is the node voltage phasor before the fault; is the short - circuit current before the fault; is the impedance of the target power grid.

[0141] In an alternative embodiment, the short - circuit current calculation module of the target power grid after short - circuit is specifically configured to:

[0142] Calculate the short - circuit current of the target power grid after short - circuit through the following formula:

[0143] , where in the formula, is the short - circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target power grid.

[0144] It should be noted that a system for determining the short - circuit current of a grid - forming energy storage system device provided in an embodiment of the present invention is used to execute all the process steps of a method for determining the short - circuit current of a grid - forming energy storage system device in the above - mentioned embodiment. The working principles and beneficial effects of the two correspond one by one, so they will not be elaborated here.

[0145] An embodiment of the present invention also provides an electronic device. The electronic device includes: a processor, a memory, and a computer program stored in the memory and executable on the processor, such as a program for determining the short - circuit current of a grid - forming energy storage system device. When the processor executes the computer program, it implements the steps in each of the above - mentioned method embodiments for determining the short - circuit current of a grid - forming energy storage system device, such as Figure 1 the step S11 shown. Or, when the processor executes the computer program, it implements the functions of each module / unit in each of the above - mentioned device embodiments, such as the data acquisition module.

[0146] Exemplarily, the computer program can be divided into one or more modules / units. The one or more modules / units are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program in the electronic device.

[0147] The electronic device may be a computing device such as a desktop computer, notebook, palm computer, and smart tablet. The electronic device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that the above components are only examples of the electronic device and do not constitute a limitation on the electronic device. It may include more or fewer components than the above, or combine some components, or different components. For example, the electronic device may also include input / output devices, network access devices, buses, etc.

[0148] The so-called processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor is the control center of the electronic device and connects various parts of the entire electronic device through various interfaces and lines.

[0149] The memory can be used to store the computer program and / or module. The processor realizes various functions of the electronic device by running or executing the computer program and / or module stored in the memory, and by calling the data stored in the memory. The memory mainly includes a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the mobile phone (such as audio data, phone book, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one magnetic disk storage device, flash device, or other volatile solid-state storage devices.

[0150] Among them, if the modules / units integrated in the electronic device are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-mentioned embodiment methods of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0151] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that they have a communication connection, which can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0152] The above-mentioned specific embodiments have further elaborated on the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. It is particularly pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining the short-circuit current of a grid-forming energy storage system device, characterized in that, Executed by a computer, including: Obtain pre-fault data of the target power grid; wherein, the pre-fault data includes pre-fault node voltage phasors, pre-fault short-circuit current, and pre-fault fault point voltage phasors; Calculate the inverter capacity according to the pre-fault data; Calculate the operation mode transfer coefficient according to the inverter capacity; Calculate the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data; Calculate the short-circuit current of the target power grid after the short-circuit according to the pre-fault data and the inverter capacity; Sum up the short-circuit current of the target power grid after the short-circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the grid-forming energy storage system equipment; The calculating the operation mode transfer coefficient according to the inverter capacity includes: Calculate the operation mode transfer coefficient through the following formula: ， In the formula, is the inverter capacity; is the impedance of the target power grid; is the overload factor; is the operation mode transfer factor.

2. The method for determining the short-circuit current of the grid-forming energy storage system equipment according to claim 1, wherein The calculating the inverter capacity according to the pre-fault data includes: Calculate the inverter capacity through the following formula: ， Wherein, is the overload factor; is the short-circuit current before the fault; is the node voltage phasor before the fault; is the fault point voltage phasor before the fault; is the capacity of the inverter.

3. The method for determining the short-circuit current of the grid-forming energy storage system device according to claim 1, wherein The calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data includes: Calculate the short-circuit current of the energy storage system through the following formula: ， Wherein, is the short-circuit current before the fault; is the operation mode transfer coefficient; is the energy storage system regulation coefficient; is the short-circuit current of the energy storage system.

4. The method for determining the short-circuit current of the grid-forming energy storage system device according to claim 3, wherein The energy storage system regulation coefficient is calculated in the following manner: Calculate the fault point voltage phasor after the short-circuit according to the pre-fault data, the short-circuit current of the energy storage system, and the operation mode transfer coefficient; Calculate the energy storage system regulation coefficient according to the fault point voltage phasor after the short-circuit and the pre-fault data.

5. The method for determining the short-circuit current of the grid-forming energy storage system equipment according to claim 4, characterized in that, The calculating the fault point voltage phasor after the short-circuit according to the pre-fault data, the short-circuit current of the energy storage system, and the operation mode transfer coefficient includes: Calculate the fault point voltage phasor after the short-circuit through the following formula: ， Wherein, is the pre-fault node voltage phasor; is the pre-fault short-circuit current; is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target power grid; is the post-fault voltage phasor at the fault point.

6. The method for determining the short-circuit current of the grid-forming energy storage system equipment according to claim 5, characterized in that, The calculating the energy storage system regulation coefficient according to the fault point voltage phasor after the short-circuit and the pre-fault data includes: Calculate the energy storage system regulation coefficient through the following formula: ， Wherein, is the voltage phasor at the fault point after short circuit; is the node voltage phasor before the fault; is the short-circuit current before the fault; is the impedance of the target power grid.

7. The method for determining the short-circuit current of the grid-forming energy storage system equipment according to claim 1, wherein The calculating the short-circuit current of the target power grid after the short-circuit according to the pre-fault data and the inverter capacity includes: Calculate the short-circuit current of the target power grid after the short-circuit through the following formula: ， Wherein, is the short-circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target power grid.

8. A system for determining the short-circuit current of a grid-forming energy storage system device, characterized in that, Including: A data acquisition module for obtaining pre-fault data of the target power grid; An inverter capacity calculation module for calculating the inverter capacity according to the pre-fault data; A transfer coefficient calculation module for calculating the operation mode transfer coefficient according to the inverter capacity; An energy storage system short-circuit current calculation module for calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data; A short-circuit current calculation module of the target power grid after the short-circuit for calculating the short-circuit current of the target power grid after the short-circuit according to the pre-fault data and the inverter capacity; A grid-forming energy storage system equipment short-circuit current calculation module for summing up the short-circuit current of the target power grid after the short-circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the grid-forming energy storage system equipment; The transfer coefficient calculation module is specifically used for: Calculate the operation mode transfer coefficient through the following formula: ， Wherein, is the inverter capacity; is the impedance of the target power grid; is the overload factor; is the operation mode transfer factor.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the computer program runs, it controls the device where the computer-readable storage medium is located to execute the method for determining the short-circuit current of the grid-forming energy storage system device according to any one of claims 1 to 7.

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