Method and system for determining short-circuit current of network construction type energy storage system equipment

Abstract

The invention relates to the technical field of short-circuit current measurement, and discloses a method and a system for determining short-circuit current of network-forming type energy storage system equipment. The method comprises the following steps: acquiring pre-fault data of a target power grid; calculating the capacity of the inverter according to the data before the fault; 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 data before the fault; calculating a target power grid short-circuit current after short circuit according to the data before the fault and the inverter capacity; and summing the short-circuit current of the target power grid after short circuit and the short-circuit current of the energy storage system to obtain the short-circuit current of the network construction type energy storage system equipment. According to the method, accurate calculation of the short-circuit current can be realized, and the real-time performance and the accuracy of short-circuit current measurement are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of short-circuit current measurement, and in particular to a method and system for determining the short-circuit current of grid-type energy storage system equipment. Background Art

[0002] Energy storage system refers to a new type of power system that is composed of energy conversion devices, electric energy conversion devices, energy storage devices, monitoring and auxiliary systems, etc., and can achieve periodic or non-periodic storage of electric energy or electric energy conversion. The development of energy storage system will give rise to a large number of innovations in power applications, bringing about the coordinated development of the five ends of the power system: source, network, load, storage, and transportation, thereby creating a functionally complete, flexible and efficient future power network system.

[0003] 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 capability of the equipment and the design requirements of the system, ensuring that the current can be quickly cut off when a short circuit occurs to prevent equipment damage, fire or more serious failures. The existing grid short-circuit current measurement technology includes converting large currents into small current signals that are easy to measure through current transformers, which are used to monitor short-circuit currents. However, the existing measurement methods also have shortcomings. When faced with a fast-occurring short circuit, traditional current transformers cannot accurately and timely capture the current peak, and when the short-circuit current is too high, the sensor and transformer will be saturated, 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 grid-connected energy storage system device, which can combine target grid data, inverter capacity, and operation mode transfer coefficient to achieve accurate calculation of the short-circuit current and improve the real-time and accuracy of short-circuit current measurement.

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

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

[0007] Calculating an 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 target power grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity;

[0010] 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 to obtain the short-circuit current of the grid-type energy storage system equipment.

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

[0012] Calculate the inverter capacity using the following formula: , where is the overload factor; is the short-circuit current before the fault; is the node voltage phasor before the fault; is the voltage phasor at the fault point before the fault; is the inverter capacity.

[0013] Preferably, the calculating of the operation mode transfer coefficient according to the inverter capacity includes:

[0014] The operating mode transfer coefficient is calculated using the following formula: , where is the inverter capacity; is the impedance of the target grid; is the overload factor; is the operation mode transfer coefficient.

[0015] 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:

[0016] The short-circuit current of the energy storage system is calculated by the following formula: , where is the short-circuit current before the fault; is the operation mode transfer coefficient; is the regulation coefficient of the energy storage system; It is the short-circuit current of the energy storage system.

[0017] Preferably, the energy storage system adjustment coefficient is calculated in the following manner:

[0018] Calculating the voltage phasor of the fault point 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;

[0019] The regulation coefficient of the energy storage system is calculated according to the voltage phasor of the fault point after the short circuit and the data before the fault.

[0020] Preferably, the calculating of the voltage phasor at the fault point 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 comprises:

[0021] The voltage phasor at the fault point after short circuit is calculated by the following formula: , where is the node voltage phasor before the fault; is the short-circuit current before the fault; It is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target grid; It is the voltage phasor at the fault point after short circuit.

[0022] Preferably, the calculating of the energy storage system regulation coefficient according to the voltage phasor at the fault point after the short circuit and the data before the fault includes:

[0023] The energy storage system regulation coefficient is calculated using the following formula: , 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 grid.

[0024] Preferably, the calculating of the target grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity includes:

[0025] The target grid short-circuit current after short circuit is calculated by the following formula: , where is the short-circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target grid.

[0026] In a second aspect, the present invention provides a system for determining a short-circuit current of a grid-connected energy storage system device, comprising:

[0027] A data acquisition module, used to acquire pre-fault data of the target power grid;

[0028] An inverter capacity calculation module, used to calculate the inverter capacity according to the pre-fault data;

[0029] A transfer coefficient calculation module, used to calculate the operation mode transfer coefficient according to the inverter capacity;

[0030] An energy storage system short-circuit current calculation module, used to calculate the energy storage system short-circuit current according to the operation mode transfer coefficient and the pre-fault data;

[0031] A short-circuit current calculation module for the target power grid after short circuit, used to calculate the short-circuit current of the target power grid after short circuit according to the pre-fault data and the inverter capacity;

[0032] The short-circuit current calculation module of the grid-type energy storage system equipment is used to sum the target grid short-circuit current after the short circuit and the energy storage system short-circuit current to obtain the short-circuit current of the grid-type energy storage system equipment.

[0033] In a third aspect, the present invention also provides an electronic device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements any one of the methods described above for determining the short-circuit current of a grid-connected energy storage system device.

[0034] In a fourth aspect, the present invention also provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute any one of the methods for determining the short-circuit current of a grid-type energy storage system device described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects: the embodiment of the present invention provides a method and system for determining the short-circuit current of a grid-type energy storage system device. The method includes: obtaining pre-fault data of the target power grid; wherein the pre-fault data includes pre-fault node voltage phasor, pre-fault short-circuit current, and pre-fault fault point voltage phasor; calculating the inverter capacity according to the pre-fault data; calculating the operation mode transfer coefficient according to the inverter capacity; calculating the energy storage system short-circuit current according to the operation mode transfer coefficient and the pre-fault data; calculating the target power grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity; summing the target power grid short-circuit current after the short circuit and the energy storage system short-circuit current to obtain the short-circuit current of the grid-type energy storage system device.

[0036] In the present invention, the method can calculate the inverter capacity by obtaining the pre-fault data of the target power grid, and further calculate the operation mode transfer coefficient using the inverter capacity, so as to determine the short-circuit current of the energy storage system in combination with the pre-fault data. Then, the short-circuit current of the target power grid after the short circuit is calculated by the pre-fault data and the inverter capacity, and finally the short-circuit current of the energy storage system and the short-circuit current of the target power grid after the short circuit are summed to obtain the short-circuit current of the grid-type energy storage system equipment. The beneficial effect of the method is that it can realize the accurate calculation of the short-circuit current and improve the real-time and accuracy of the short-circuit current measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1It is a flow chart of a method for determining short-circuit current of a grid-type energy storage system device provided by a first embodiment of the present invention;

[0038] Figure 2 It is a structural schematic diagram of a system for determining short-circuit current of a grid-type energy storage system device provided by a second embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Reference Figure 1 The first embodiment of the present invention provides a method for determining the short-circuit current of a grid-connected energy storage system device, comprising the following steps:

[0041] S11, obtaining pre-fault data of the target power grid.

[0042] S12: Calculate the inverter capacity according to the pre-fault data.

[0043] S13, calculating an operation mode transfer coefficient according to the inverter capacity.

[0044] S14, calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data.

[0045] S15, calculating the target grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity.

[0046] S16, summing the target power grid short-circuit current after the short circuit and the energy storage system short-circuit current to obtain the short-circuit current of the grid-connected energy storage system equipment.

[0047] It is worth noting that the energy storage system refers to a new type of power system that is composed of energy conversion devices, electric energy conversion devices, energy storage devices, monitoring and auxiliary systems, etc., and can achieve periodic or non-periodic storage of electric energy or electric 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 five ends of the power system: source, network, load, storage, and transportation, thereby creating a functionally complete, flexible and efficient future power network system.

[0048] 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 capability of the equipment and the design requirements of the system, ensuring that the current can be quickly cut off when a short circuit occurs to prevent equipment damage, fire or more serious failures.

[0049] In order to facilitate the understanding of the present invention, some preferred embodiments of the present invention are further described below.

[0050] In step S11 , pre-fault data of the target power grid is acquired.

[0051] 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.

[0052] Specifically, the node voltage phasor refers to the voltage amplitude and phase information of a node in the target power grid before the fault. It can be obtained by installing a high-precision voltage sensor at the node to measure the voltage in real time and record its amplitude and phase angle, or by combining a data acquisition system (such as SCADA) to store the voltage data measured by the sensor in the form of a phasor. The node voltage phasor provides basic data for determining the stable operating state and pre-fault operating characteristics of the power grid, and is used to calculate the dynamic changes of the power grid when a fault occurs.

[0053] Specifically, the short-circuit current before the fault refers to the short-circuit current value that occurs when the power grid is in normal operation, reflecting the load and flow characteristics of the circuit. It can be obtained by installing current transformers at key lines in the power grid to monitor and record the current value in real time, especially the short-circuit conditions at system load peaks or in specific scenarios, or it can be extracted from the historical data of the power grid operation and evaluated in combination with actual working conditions. The short-circuit current before the fault is used to calculate the fault response in the energy storage system and is an important basis for evaluating whether the protection measures are effective.

[0054] Specifically, the voltage phasor at the fault point before the fault refers to the voltage phasor information at the fault point when the fault is about to occur, including the voltage amplitude and phase angle. Its acquisition method can be to install measurement 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 the data storage and analysis system to trace back the voltage data at the fault point after the fault occurs to obtain the voltage state before the fault. The voltage phasor at the fault point before the fault is used to accurately describe the voltage state of the power grid before the fault, which plays an important role in the subsequent short-circuit current calculation and fault handling.

[0055] It is worth noting that the short-circuit current before the fault refers to the "estimated short-circuit current under normal operating conditions" before the system fault is about to occur. It is the short-circuit current caused by the fault calculated through the current and load conditions under normal operating conditions. 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 operating status of the power grid before the fault (node ​​voltage, current flowing under normal load), it is possible to predict and evaluate the size of the short-circuit current that occurs after the fault occurs, providing a reference for system design and protection. In this way, the size of the current impact that the power system will withstand can be estimated in advance to ensure that the system design meets safety requirements.

[0056] In step S12, the inverter capacity is calculated based on the pre-fault data.

[0057] Preferably, the calculating the inverter capacity according to the pre-fault data includes:

[0058] Calculate the inverter capacity using the following formula: , where is the overload factor; is the short-circuit current before the fault; is the node voltage phasor before the fault; is the voltage phasor at the fault point before the fault; is the inverter capacity.

[0059] It is worth noting that the inverter capacity refers to the maximum power or energy output capacity that the inverter can handle or convert. It is 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-type energy storage system equipment. It represents the maximum power or current output capacity that the energy storage system can provide when facing a short-circuit fault, and is one of the important parameters for evaluating and calculating the system response capability. By calculating the inverter capacity, the impact and contribution of the energy storage system in the case of a short circuit 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 operating mode transfer coefficient and the short-circuit current of the energy storage system. The inverter capacity determines the load capacity and response capability of the energy storage system, and is an indispensable 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 a significant impact on the short-circuit current of the power grid.

[0060] Specifically, is the overload coefficient, which represents the coefficient of the maximum load capacity and expected load capacity of the system during operation. It reflects the coefficient of the maximum load that the inverter bears in the event of a fault compared to the normal operating state. Its function is to adjust and correct the calculation results to reflect the overload conditions in the actual operating environment and ensure that the system has sufficient margin and stability. For example, 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 speaking, the typical value range is between 1.1 and 1.5. For example, Indicates that the system can withstand an additional 20% load capacity on the basis of normal load. The value will vary in different application scenarios. If the system requires higher fault tolerance or greater load adjustment room, a larger overload factor will be used. It is the short-circuit current before the fault, which refers to the current flow value of the system before the fault occurs. It is expressed as the estimated short-circuit current. As a basic parameter, it reflects the current condition before the fault and provides initial conditions for evaluating the system response after the fault. It is the node voltage phasor before the fault, indicating the voltage amplitude and phase angle of a node in the target power grid before the fault occurs, reflecting the electrical state of the node. It is used to calculate the stable operation state of the system and provide a reference for the calculation of short-circuit current. It is the voltage phasor of the fault point before the fault occurs, indicating 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 occurs, and helps evaluate the voltage distribution and electrical changes in the system. is the inverter capacity, which is the calculated inverter capacity value, reflecting the load capacity of the inverter before and after the fault. It provides input values ​​for the subsequent calculation of the operation mode transfer coefficient and the system short-circuit current, as an indicator of the system's load and response capabilities.

[0061] After the inverter capacity calculation is completed, the inverter capacity will be used to calculate the operating mode transfer coefficient, which can be further used to evaluate the short-circuit current of the energy storage system.

[0062] In step S13, the operation mode transfer coefficient is calculated according to the inverter capacity.

[0063] Preferably, the calculating of the operation mode transfer coefficient according to the inverter capacity includes:

[0064] The operating mode transfer coefficient is calculated using the following formula: , where is the inverter capacity; is the impedance of the target grid; is the overload factor; is the operation mode transfer coefficient.

[0065] Specifically, The impedance of the target grid refers to the network impedance value of the system connection, which reflects the distribution and impedance characteristics of the current in the grid. It is used to calculate the operation mode transfer coefficient and takes into account the influence of the electrical characteristics of the grid on the distribution and regulation of short-circuit current. Specifically, It can be measured in the following ways: Impedance measurement, by introducing a known current signal into the power grid and measuring the resulting voltage change to calculate the impedance. Use a transformer or reactor as a signal source to inject a signal into the system. The specific steps are: first inject a test current of known amplitude and frequency into the power grid. Then use a voltage sensor to measure the voltage change at the injection point and its nearby nodes. Finally, calculate the impedance value using Ohm's law. This method is suitable for scenarios where the power grid load is relatively stable or the introduction of test signals is allowed; short-circuit test method, a controlled short-circuit test is performed under safe conditions, and the grid impedance is calculated by the fault current and the corresponding voltage drop. Exemplarily, the measurement steps may be to cause a short-circuit fault under controlled conditions, record the current and voltage during the short circuit, and use the formula ,in is the voltage during the short circuit, The harmonic injection method uses the nonlinear characteristics of the system to estimate the grid impedance by injecting harmonic signals of a specific frequency and measuring the system's response to these harmonics. The steps are to inject a harmonic signal of a known frequency into the grid, record the voltage and current changes caused 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 measurements in a running system without interrupting the system operation.

[0066] It is worth mentioning that The operating mode transfer coefficient is used to describe the system's ability to regulate load and short-circuit current under different operating conditions. The operating mode transfer coefficient is used to calculate the short-circuit current of the energy storage system in the subsequent steps. It is a regulating parameter of the grid operating state and reflects the system's response capability under different working conditions.

[0067] In step S14, the short-circuit current of the energy storage system is calculated according to the operation mode transfer coefficient and the pre-fault data.

[0068] 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:

[0069] The short-circuit current of the energy storage system is calculated by the following formula: , where is the short-circuit current before the fault; is the operation mode transfer coefficient; is the regulation coefficient of the energy storage system; It is the short-circuit current of the energy storage system.

[0070] It is worth mentioning that The energy storage system regulation coefficient needs to be calculated jointly through subsequent steps. The energy storage system regulation coefficient is a parameter used to adjust and describe the energy storage system's ability to respond to short-circuit current when facing grid faults or other changes. It helps to accurately calculate the short-circuit current of the energy storage system by analyzing and correcting the operation of the energy storage system under fault conditions. Simply put, it is a coefficient used to reflect how the energy storage system dynamically adjusts the short-circuit current output under different conditions. The response of the energy storage system to a grid fault is not fixed, but is affected by a variety of factors (such as pre-fault data, operating mode, etc.). The regulation coefficient can reflect the specific performance of the energy storage system in this dynamic change and help to more accurately describe the actual value of the system's 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 results so that the obtained short-circuit current can more truly 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, operating modes and external factors.

[0071] Preferably, the energy storage system adjustment coefficient is calculated in the following manner:

[0072] Calculating the voltage phasor of the fault point 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;

[0073] The regulation coefficient of the energy storage system is calculated according to the voltage phasor of the fault point after the short circuit and the data before the fault.

[0074] Specifically, this step is a joint calculation step, and the short-circuit current of the energy storage system here needs to be calculated jointly with the above steps.

[0075] Preferably, the calculating of the voltage phasor at the fault point 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 comprises:

[0076] The voltage phasor at the fault point after short circuit is calculated by the following formula: , where is the node voltage phasor before the fault; is the short-circuit current before the fault; It is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target grid; It is the voltage phasor at the fault point after short circuit.

[0077] Specifically, the formula first uses the node voltage phasor before the fault as the reference, which is the voltage state of the power grid before the short circuit occurs, providing a reference point for the changes after the short circuit. The interaction with other parameters indicates the response of the system under short-circuit conditions, including the impact of current and the regulation of impedance factors. Represents the ratio adjustment of the impedance effect, thereby affecting the final short-circuit voltage result. Indicates short circuit current and energy storage system short-circuit current The difference between represents 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 adjustment coefficient and the fractional term, and Add them together to get the voltage state of the system at the fault point after the short circuit. The voltage phasor at the fault point after the short circuit describes the voltage change of the system after the short circuit.

[0078] Preferably, the calculating of the energy storage system regulation coefficient according to the voltage phasor at the fault point after the short circuit and the data before the fault includes:

[0079] The energy storage system regulation coefficient is calculated using the following formula: , 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 grid.

[0080] It is worth noting that this step and the above steps are joint calculation steps. By jointly calculating the three formulas, the regulation coefficient of the energy storage system, the voltage phasor at the fault point after short circuit and the short-circuit current of the energy storage system can be obtained.

[0081] In step S15, a target grid short-circuit current after a short circuit is calculated according to the pre-fault data and the inverter capacity.

[0082] Preferably, the calculating of the target grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity includes:

[0083] The target grid short-circuit current after short circuit is calculated by the following formula: , where is the short-circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target grid.

[0084] Specifically, is the calculated target grid short-circuit current. It indicates the short-circuit current calculated under specific conditions, which is the current after the grid is short-circuited. It 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, which reflects the load capacity of the inverter in the energy storage system in the power grid and its impact on the short-circuit current. The impedance of the target grid describes the impedance characteristics of the current path in the grid, reflecting the distribution of the current in the network and the resistance it encounters. The calculation of the current after the short circuit starts with the short circuit current before the fault as the basic value, representing the current state of the system before the short circuit occurs. It is a correction term for the influence of inverter capacity, which indicates the correction or influence of the inverter capacity on the short-circuit current. The contribution of the inverter capacity is adjusted by the adjustment coefficient and the grid impedance. Specifically, the inverter capacity will affect the current distribution and response of the system during a short circuit. The adjustment coefficient is used to adjust the influence of the inverter on the current, which is a coefficient related to the load capacity or system configuration. Impedance describes the current distribution characteristics in the system grid. The current output by the inverter will be affected by the grid impedance, resulting in different degrees of response during a short circuit. The short-circuit current finally calculated is determined by subtracting the correction term for the influence of the inverter, which indicates 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 and the impact on the overall system stability during a short-circuit event.

[0085] It is worth noting that the short-circuit current of the target power grid after a short circuit refers to the short-circuit current generated by the target power grid itself after a short-circuit fault occurs in the power grid. It is calculated based on the pre-fault data of the power grid (such as the short-circuit current and inverter capacity before the fault), reflecting the current response capability of the power grid itself under the short-circuit condition. The short-circuit current of the target power grid after a short circuit is determined by the characteristics of each electrical component and system in the power grid, and it represents the main current characteristics of the power grid under the short-circuit condition. The short-circuit current of the energy storage system refers to the short-circuit current generated by the energy storage system under the short-circuit condition. As an independent power source or power regulation device, the energy storage system will provide a certain current response when the power grid is short-circuited. The short-circuit current calculation of the energy storage system is based on parameters such as the operation mode transfer coefficient, the energy storage system regulation coefficient and the pre-fault data, which describes the participation and contribution of the energy storage system to the short-circuit event. In the power system, the short-circuit current of the power grid and the energy storage system is regarded as a parallel current source. When a short circuit occurs in the system, these current sources will 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 currents of each source. Therefore, in order to accurately describe the short-circuit response of the entire system, it is necessary to sum the short-circuit currents of the target power grid and the energy storage system.

[0086] In step S16, the short-circuit target grid short-circuit current and the energy storage system short-circuit current are summed to obtain the short-circuit current of the grid-connected energy storage system equipment.

[0087] In the method for determining the short-circuit current of the grid-type energy storage system equipment, after calculating the short-circuit current of the target grid after the short circuit and the short-circuit current of the energy storage system, the last step is to sum the two short-circuit currents to obtain the total short-circuit current of the grid-type energy storage system equipment. Among them, the short-circuit current of the target grid after the short circuit is calculated based on the pre-fault data and the inverter capacity. The short-circuit current of the target grid after the short circuit describes the current value generated by the grid when the short circuit occurs, and is one of the main parameters of the grid short-circuit state. The short-circuit current of the energy storage system is calculated by parameters such as the operating mode transfer coefficient and the energy storage system adjustment coefficient. It reflects the short-circuit current generated by the energy storage system under short-circuit conditions, indicating the contribution and response capability of the energy storage system to the short-circuit current of the grid. The short-circuit current of the target grid after the short circuit and the short-circuit current of the energy storage system are summed to obtain the total short-circuit current of the grid-type energy storage system equipment.

[0088] Specifically, the summed total short-circuit current reflects the overall current of the entire grid-type energy storage system under short-circuit conditions. It combines the short-circuit currents of the grid and the energy storage system to provide a global short-circuit current assessment 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, thereby helping to determine the required protection measures (such as the capacity of the circuit breaker).

[0089] It is worth noting that the short-circuit current of the grid-type energy storage system equipment is obtained by summing the short-circuit current of the target grid and the short-circuit current of the energy storage system after the short circuit, which is mainly based on the following physical and electrical principles: In the 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 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 in the case of a short circuit, and is the common influence of all current sources of the grid-type energy storage system on the total short-circuit current when the grid is short-circuited. At the same time, the grid-type energy storage system refers to a joint operation system of energy storage equipment and the grid. In the case of a short circuit, 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. The summation reflects the response of the energy storage system and the grid to the short-circuit situation, which is the manifestation of the comprehensive short-circuit behavior of the overall system. In order to design and evaluate the safety of the system, it is necessary to know the total current size during short circuit. Considering the short-circuit current of the target power grid alone or the short-circuit current of the energy storage system alone cannot accurately reflect the electrical stress level of the entire system. The summed total short-circuit current provides the maximum current value of the system under short-circuit conditions, which can be used to determine the capacity of the protection device and select appropriate protection measures. From a physical point of view, both the power grid and the energy storage system provide current paths, and when a short circuit occurs, all current paths 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, the short-circuit current of the target power grid and the short-circuit current of the energy storage system after the short circuit are summed, which can accurately describe the total current response of the grid-type energy storage system equipment under short-circuit conditions, which is based on the superposition of parallel current sources, the unified representation of physical phenomena, and the need to simplify the analysis model. This method provides the short-circuit current performance of an overall system, providing important basic data for the design and operation of the system.

[0090] The following describes the working process of the present invention by taking a relatively common scenario as an example. The working process is as follows:

[0091] A grid-connected energy storage system is connected to a power grid system. Suddenly, a short circuit occurs in the grid. At this time, it is necessary to determine the total short-circuit current of the entire system (including the grid and the energy storage system) under this short-circuit condition to ensure the safety and stability of the system and take corresponding protection measures.

[0092] First, the system collects pre-fault data of the target power grid, including the voltage phasor of the node, 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 acquired pre-fault data, the capacity of the inverter in the energy storage system is calculated. The inverter capacity is an important parameter when the energy storage system responds to a short circuit, which determines the output capacity of the energy storage system.

[0093] The calculated inverter capacity is combined with the grid impedance parameters to determine the operation mode transfer coefficient, which reflects the energy storage system's ability to regulate load and short-circuit current under different operating conditions.

[0094] Using the operating mode transfer coefficient and pre-fault data, the short-circuit current of the energy storage system in the event of a short circuit is calculated. This step can determine the response of the energy storage system to the grid when a short circuit occurs.

[0095] Combine the pre-fault data and inverter capacity to calculate the short-circuit current of the target grid after the short circuit. This value represents the current change of the grid part under the short-circuit state.

[0096] Finally, the short-circuit current of the target power grid after the short circuit is summed with the short-circuit current of the energy storage system to obtain the total short-circuit current of the grid-connected energy storage system equipment. This total short-circuit current is used to reflect the overall response of the entire system under short-circuit conditions.

[0097] In summary, the present invention provides a method for determining the short-circuit current of a grid-type energy storage system device, comprising: obtaining pre-fault data of a target power grid; wherein the pre-fault data includes a pre-fault node voltage phasor, a pre-fault short-circuit current, and a pre-fault fault point voltage phasor;

[0098] Calculating the inverter capacity according to the pre-fault data;

[0099] Calculating an operation mode transfer coefficient according to the inverter capacity;

[0100] Calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data;

[0101] Calculating the target power grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity;

[0102] 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 to obtain the short-circuit current of the grid-type energy storage system equipment.

[0103] In the present invention, the method can calculate the inverter capacity by obtaining the pre-fault data of the target power grid, and further calculate the operation mode transfer coefficient using the inverter capacity, so as to determine the short-circuit current of the energy storage system in combination with the pre-fault data. Then, the short-circuit current of the target power grid after the short circuit is calculated by the pre-fault data and the inverter capacity, and finally the short-circuit current of the energy storage system and the short-circuit current of the target power grid after the short circuit are summed to obtain the short-circuit current of the grid-type energy storage system equipment. The beneficial effect of the method is that it can realize the accurate calculation of the short-circuit current and improve the real-time and accuracy of the short-circuit current measurement.

[0104] Reference Figure 2 The second embodiment of the present invention provides a system for determining the short-circuit current of a grid-connected energy storage system device, comprising:

[0105] A data acquisition module, used to acquire pre-fault data of the target power grid;

[0106] An inverter capacity calculation module, used to calculate the inverter capacity according to the pre-fault data;

[0107] A transfer coefficient calculation module, used to calculate the operation mode transfer coefficient according to the inverter capacity;

[0108] An energy storage system short-circuit current calculation module, used to calculate the energy storage system short-circuit current according to the operation mode transfer coefficient and the pre-fault data;

[0109] A short-circuit current calculation module for the target power grid after short circuit, used to calculate the short-circuit current of the target power grid after short circuit according to the pre-fault data and the inverter capacity;

[0110] The short-circuit current calculation module of the grid-type energy storage system equipment is used to sum the target grid short-circuit current after the short circuit and the energy storage system short-circuit current to obtain the short-circuit current of the grid-type energy storage system equipment.

[0111] In an optional implementation manner, the inverter capacity calculation module is specifically used to:

[0112] Calculate the inverter capacity using the following formula: , where is the overload factor; is the short-circuit current before the fault; is the node voltage phasor before the fault; is the voltage phasor at the fault point before the fault; is the inverter capacity.

[0113] In an optional implementation, the transfer coefficient calculation module is specifically used to:

[0114] The operating mode transfer coefficient is calculated using the following formula: , where is the inverter capacity; is the impedance of the target grid; is the overload factor; is the operation mode transfer coefficient.

[0115] In an optional implementation, the energy storage system short-circuit current calculation module is specifically used to:

[0116] The short-circuit current of the energy storage system is calculated by the following formula: , where is the short-circuit current before the fault; is the operation mode transfer coefficient; is the regulation coefficient of the energy storage system; It is the short-circuit current of the energy storage system.

[0117] In an optional implementation, the energy storage system short-circuit current calculation module is specifically used to:

[0118] Calculating the voltage phasor of the fault point 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;

[0119] The regulation coefficient of the energy storage system is calculated according to the voltage phasor of the fault point after the short circuit and the data before the fault.

[0120] In an optional implementation, the energy storage system short-circuit current calculation module is specifically used to:

[0121] The voltage phasor at the fault point after short circuit is calculated by the following formula: , where is the node voltage phasor before the fault; is the short-circuit current before the fault; It is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target grid; It is the voltage phasor at the fault point after short circuit.

[0122] In an optional implementation, the energy storage system short-circuit current calculation module is specifically used to:

[0123] The energy storage system regulation coefficient is calculated using the following formula: , 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 grid.

[0124] In an optional implementation manner, the post-short-circuit target power grid short-circuit current calculation module is specifically used to:

[0125] The target grid short-circuit current after short circuit is calculated by the following formula: , where is the short-circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target grid.

[0126] It should be noted that a system for determining the short-circuit current of a grid-type 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-type energy storage system device in the above embodiment. The working principles and beneficial effects of the two correspond one to one, and therefore will not be repeated here.

[0127] An embodiment of the present invention further 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 method program for determining the short-circuit current of a grid-type energy storage system device. When the processor executes the computer program, the steps in the above-mentioned method embodiments for determining the short-circuit current of a grid-type energy storage system device are implemented, such as Figure 1 Alternatively, when the processor executes the computer program, the functions of the modules / units in the above-mentioned device embodiments are realized, such as the data acquisition module.

[0128] Exemplarily, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program in the electronic device.

[0129] The electronic device may be a computing device such as a desktop computer, a notebook, a PDA, and a smart tablet. The electronic device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that the above components are merely examples of electronic devices and do not constitute a limitation on the electronic device. The electronic device may include more or fewer components than the above components, or may combine certain components, or different components. For example, the electronic device may also include input and output devices, network access devices, buses, etc.

[0130] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the electronic device, and uses various interfaces and lines to connect various parts of the entire electronic device.

[0131] The memory can be used to store the computer program and / or module, and the processor realizes various functions of the electronic device by running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0132] Wherein, if the module / unit integrated in the electronic device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained 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, computer-readable media do not include electric carrier signals and telecommunication signals.

[0133] It should be noted that the device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which may be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art may understand and implement it without paying any creative effort.

[0134] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the short-circuit current of a grid-connected energy storage system device, characterized in that: Executed by a computer, including: Acquire pre-fault data of the target power grid; wherein the pre-fault data includes pre-fault node voltage phasor, pre-fault short-circuit current, and pre-fault fault point voltage phasor; 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 target power grid short-circuit current after the short circuit according to the pre-fault data and the inverter capacity; 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 to obtain the short-circuit current of the grid-type energy storage system equipment.

2. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 1, characterized in that: The step of calculating the inverter capacity according to the pre-fault data includes: Calculate the inverter capacity using the following formula: , where is the overload factor; is the short-circuit current before the fault; is the node voltage phasor before the fault; is the voltage phasor at the fault point before the fault; is the inverter capacity.

3. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 1, characterized in that: The step of calculating the operation mode transfer coefficient according to the inverter capacity includes: The operating mode transfer coefficient is calculated using the following formula: , where is the inverter capacity; is the impedance of the target grid; is the overload factor; is the operation mode transfer coefficient.

4. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 1, characterized in that: The calculating the short-circuit current of the energy storage system according to the operation mode transfer coefficient and the pre-fault data includes: The short-circuit current of the energy storage system is calculated by the following formula: , where is the short-circuit current before the fault; is the operation mode transfer coefficient; is the regulation coefficient of the energy storage system; It is the short-circuit current of the energy storage system.

5. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 4, characterized in that: The energy storage system adjustment coefficient is calculated in the following way: Calculating the voltage phasor of the fault point 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; The regulation coefficient of the energy storage system is calculated according to the voltage phasor of the fault point after the short circuit and the data before the fault.

6. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 5, characterized in that: The calculating the voltage phasor of the fault point 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 comprises: The voltage phasor at the fault point after short circuit is calculated by the following formula: , where is the node voltage phasor before the fault; is the short-circuit current before the fault; It is the short-circuit current of the energy storage system; is the operation mode transfer coefficient; is the impedance of the target grid; It is the voltage phasor at the fault point after short circuit.

7. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 6, characterized in that: The calculating the energy storage system regulation coefficient according to the voltage phasor at the fault point after the short circuit and the data before the fault includes: The energy storage system regulation coefficient is calculated using the following formula: , 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 grid.

8. The method for determining the short-circuit current of a grid-connected energy storage system device according to claim 1, characterized in that: The calculating, according to the pre-fault data and the inverter capacity, a target grid short-circuit current after a short circuit, comprises: The target grid short-circuit current after short circuit is calculated by the following formula: , where is the short-circuit current before the fault; is the inverter capacity; is the overload factor; is the impedance of the target grid.

9. A system for determining short-circuit current of a grid-connected energy storage system device, characterized in that: include: A data acquisition module, used to acquire pre-fault data of the target power grid; An inverter capacity calculation module, used to calculate the inverter capacity according to the pre-fault data; A transfer coefficient calculation module, used to calculate the operation mode transfer coefficient according to the inverter capacity; An energy storage system short-circuit current calculation module, used to calculate the energy storage system short-circuit current according to the operation mode transfer coefficient and the pre-fault data; A short-circuit current calculation module for the target power grid after short circuit, used to calculate the short-circuit current of the target power grid after short circuit according to the pre-fault data and the inverter capacity; The short-circuit current calculation module of the grid-type energy storage system equipment is used to sum the target grid short-circuit current after the short circuit and the energy storage system short-circuit current to obtain the short-circuit current of the grid-type energy storage system equipment.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, 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-connected energy storage system device according to any one of claims 1 to 8.

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