Method and device for calculating short-circuit current of inverter power supply based on virtual impedance control

Abstract

The invention relates to a virtual impedance control-based inverter power supply short-circuit current calculation method and device, and the method comprises the steps: obtaining a topological structure of an inverter power supply, and building a mathematical model corresponding to the inverter power supply; calculating the voltage drop based on the mathematical model of the inverter power supply to obtain a virtual impedance value; based on the virtual impedance value, a filter circuit equation and a virtual impedance control equation are combined to obtain a solving equation of the inverter current; and obtaining a short-circuit current expression of the inverter power supply according to the solving equation of the inverter current so as to obtain the short-circuit current of the corresponding inverter power supply. According to the method, the fault current characteristics of the grid-forming type inverter power supply are analyzed, the solving equation of the short-circuit current of the grid-forming type inverter power supply is obtained, and accurate calculation of the short-circuit current of the inverter power supply in a corresponding scene can be realized according to the fault control parameters of the grid-forming type inverter power supply in combination with the solving equation of the short-circuit current of the grid-forming type inverter power supply. The accuracy of a calculation result is improved, and stable control of the power grid during a fault period is realized.

Description

Technical Field

[0001] The present application relates to the technical field of power system monitoring, and in particular to a method and device for calculating short-circuit current of an inverter power supply based on virtual impedance control. Background Art

[0002] At present, with the rapid growth of the scale of new energy grid connection and the continuous improvement of new energy penetration, the characteristics of ultra-high proportion of new energy power supply access and reduced grid strength are becoming more and more obvious, which brings severe challenges to the safe and stable operation of the power system. The grid-connected inverter power supply adopts power synchronization mode, which has good stability margin and synchronization characteristics under weak power grid, showing strong stability, and can support the strength of the power grid to a certain extent.

[0003] However, there is a lack of research on the output current characteristics of grid-connected inverters during short-circuit faults. When a grid fault occurs, the grid-connected converters of new energy sources have weak fault current tolerance capabilities. To prevent them from disconnecting from the grid due to overcurrent during the fault, a limiting link must be added. However, the fault characteristics of this process are unclear and cannot be analyzed in real time. Therefore, it is necessary to conduct a systematic analysis of the fault current controlled by the grid-connected inverter, further clarify the factors that affect the short-circuit current, and accurately calculate the short-circuit current. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a method and device for calculating the short-circuit current of an inverter power supply based on virtual impedance control, which specifically adopts the following technical solutions:

[0005] A method for calculating short-circuit current of an inverter power supply based on virtual impedance control comprises the following steps:

[0006] Acquire the topological structure of the inverter power supply, and establish a mathematical model of the corresponding inverter power supply according to the topological structure, wherein in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control;

[0007] The voltage drop is calculated based on the mathematical model of the inverter power supply to obtain the virtual impedance value;

[0008] A solution equation for the inverter current is obtained based on the virtual impedance value simultaneous filter circuit equation and the virtual impedance control equation;

[0009] The short-circuit current expression of the inverter power supply is obtained according to the solution equation of the inverter current, and the short-circuit current of the corresponding inverter power supply is obtained based on the short-circuit current expression of the inverter power supply.

[0010] Optionally, the fault ride-through control strategy is a low voltage ride-through control strategy, and the low voltage ride-through control strategy includes:

[0011]

[0012] in is the d-axis voltage reference value in the synchronous rotating coordinate system after voltage reduction; u is the reference value of the q-axis voltage in the synchronous rotating coordinate system after voltage reduction; d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; R v is the resistance component; L v is the virtual inductance; ω is the actual value of the virtual speed of the virtual synchronous generator.

[0013] Optionally: the inverter power supply adopts virtual synchronous machine control, the virtual synchronous machine control includes active power-frequency control and reactive power-voltage control, and the basic equation of the virtual synchronous machine control includes:

[0014]

[0015] Where P ref is the active reference value; P e is the actual value of active power; D is the damping coefficient; ω N is the virtual speed rated value of the virtual synchronous generator; ω is the virtual speed actual value of the virtual synchronous generator; J is the virtual inertia, which is used to simulate the time delay caused by the magnetic flux of the virtual synchronous generator; θ ref is the virtual internal potential phase angle; k q is the reactive power-voltage droop coefficient; Q ref is the reactive power reference value; Q e is the actual reactive power value; E ref is the virtual internal potential; U0 is the voltage base value.

[0016] Optional: The filter circuit equation includes:

[0017]

[0018] Where E ref is the virtual internal potential; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; R f is the resistance of the filter; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; X fis the impedance of the filter; L f is the inductance of the filter.

[0019] Optionally, the virtual impedance is a variable impedance, and the calculation step of the virtual impedance includes:

[0020] Z v =R v +jX v ;

[0021] The resistance component R v for:

[0022] X v =n X / R R v ;

[0023] Where Z v is the virtual impedance value; R v is the resistance component; X v is the reactance component; j is the imaginary unit; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

[0024] Optional: When solving the virtual impedance, the short-circuit current during the fault period needs to be limited to the safety range of the converter device, and the resistance component of the virtual impedance is solved by the current limiting amplitude and the starting threshold of the inverter power supply:

[0025]

[0026] Where R v is the resistance component; E is the difference between the virtual internal potential and the grid connection point voltage; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

[0027] Optionally: the solution equation for the inverter current includes:

[0028]

[0029] where i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronously rotating coordinate system; s is the complex domain operator; L is the equivalent inductance; R is the equivalent resistance; X is the equivalent reactance; E ref is the virtual internal potential; i q (0) is the q-axis current value of the short-circuit current at time 0; i d (0) is the d-axis current value of the short-circuit current at time 0; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; uq is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system.

[0030] Optionally: the step of obtaining the short-circuit current expression of the inverter power supply according to the calculation result of the solution equation of the inverter current comprises:

[0031] The calculation result of the inverter current solution equation is subjected to an inverse Park transformation to obtain the short-circuit current expression of the inverter power supply, namely:

[0032]

[0033] in:

[0034]

[0035] Where i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; t is the time variable; R is the equivalent resistance; X is the equivalent reactance; E ref is the virtual internal potential; i q (0) is the q-axis current value of the short-circuit current at time 0; i d (0) is the d-axis current value of the short-circuit current at time 0; ω is the actual value of the virtual speed of the virtual synchronous generator; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; Z is the virtual impedance value; τ is the decay time constant.

[0036] Furthermore, the present application also discloses a device for calculating short-circuit current of an inverter power supply based on virtual impedance control, the device comprising:

[0037] A model building module, used to obtain the topological structure of the inverter power supply, and establish a mathematical model of the corresponding inverter power supply according to the topological structure, wherein in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control;

[0038] An impedance calculation module, used for calculating the voltage drop based on a mathematical model of the inverter power supply to obtain a virtual impedance value;

[0039] A current solving module, used for obtaining a solution equation of an inverter current based on a virtual impedance value simultaneous filter circuit equation and a virtual impedance control equation;

[0040] The current output module is used to obtain the short-circuit current expression of the inverter power supply according to the solution equation of the inverter current, and obtain the short-circuit current of the corresponding inverter power supply based on the short-circuit current expression of the inverter power supply.

[0041] Beneficial Effects

[0042] The technical solution of this application has the following beneficial effects:

[0043] The method for calculating the short-circuit current of the inverter power supply based on virtual impedance control of the present application analyzes the fault current characteristics of the grid-type inverter power supply and obtains the solution equation of the short-circuit current of the grid-type inverter power supply. The short-circuit current of the inverter power supply can be accurately calculated in the corresponding scenario according to the fault control parameters of the grid-type inverter current and the solution equation of the short-circuit current of the grid-type inverter power supply, thereby improving the accuracy of the calculation results and realizing stable control of the power grid during faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of a method for calculating short-circuit current of an inverter power supply based on virtual impedance control in an embodiment of the present application.

[0045] Figure 2 It is a topological structure diagram of the grid-type inverter power supply in the embodiment of the present application.

[0046] Figure 3 It is a comparison chart of the short-circuit current simulation value and the calculated value based on the virtual impedance in the embodiment of the present application.

[0047] Figure 4 Schematic diagram of the structure of a device for calculating short-circuit current of an inverter power supply based on virtual impedance control in an embodiment of the present application.

[0048] Figure 5 This is a structural diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and cannot be used to limit the scope of protection of the present application. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanation of the present application.

[0050] In power systems, the correct operation of protection devices (such as circuit breakers, fuses, etc.) is crucial to isolating faults. Short-circuit current calculation can provide accurate data support for the selection and setting of protection devices. By calculating the short-circuit current, the action time and action current of the protection device under different fault conditions can be determined to avoid false action or refusal of the protection device.

[0051] With the rapid growth of the scale of new energy grid connection and the increase in the proportion of new energy power supply access, the safe and stable operation of the power system has been severely challenged. New energy power generation systems are usually connected to the power grid through inverter power supplies. The access of a large number of new energy sources has changed the structure of the power grid and the power distribution, causing the size and distribution of short-circuit current to change. After the new energy is connected to the power grid, the calculation of short-circuit current becomes more complicated due to the intermittent and uncertain output power and the diversity of inverter power supply control strategies. When calculating the short-circuit current, it is necessary to consider multiple factors such as the operating state, control parameters and grid fault type of the new energy power generation system. The traditional short-circuit current calculation method may no longer be applicable, and new calculation methods and models need to be studied. Therefore, this application analyzes the fault current characteristics of the grid-forming inverter power supply and constructs a solution equation for the short-circuit current of the grid-forming inverter power supply. According to the fault control parameters of the grid-forming inverter current and the solution equation of the short-circuit current of the grid-forming inverter power supply, the short-circuit current of the inverter power supply can be accurately calculated in the corresponding scenario, and the accuracy of the calculation results can be improved, thereby achieving stable control of the power grid during the fault.

[0052] Combination Figure 1 As shown, the embodiment of the present application specifically discloses a method for calculating short-circuit current of an inverter power supply based on virtual impedance control, which comprises the following steps:

[0053] Step 1: Obtain the topological structure of the inverter power supply and establish the mathematical model of the corresponding inverter power supply according to the topological structure. Figure 2 As shown, it is a topological structure diagram of the grid-type inverter power supply in this embodiment. In this embodiment, in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control;

[0054] Specifically, the fault ride-through control strategy of the inverter power supply described in step 1 of the present application is a low voltage ride-through control strategy. During the fault period, the grid-type inverter power supply control relies on the low voltage ride-through control loop to ensure the safe operation of the equipment. The specific control equation is:

[0055]

[0056] in is the d-axis voltage reference value in the synchronous rotating coordinate system after voltage reduction; is the q-axis voltage reference value in the synchronous rotating coordinate system after voltage reduction; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; R v is the resistance component; L vis the virtual inductance; ω is the actual value of the virtual speed of the virtual synchronous generator.

[0057] Furthermore, the inverter power supply described in the present application adopts virtual synchronous machine control, and the virtual synchronous machine control includes active power-frequency control and reactive power-voltage control. The basic equation of the virtual synchronous machine control includes:

[0058]

[0059] Where P ref is the active reference value; P e is the actual value of active power; D is the damping coefficient; ω N is the virtual speed rated value of the virtual synchronous generator; ω is the virtual speed actual value of the virtual synchronous generator; J is the virtual inertia, which is used to simulate the time delay caused by the magnetic flux of the virtual synchronous generator; θ ref is the virtual internal potential phase angle; k q is the reactive power-voltage droop coefficient; Q ref is the reactive power reference value; Q e is the actual reactive power value; E ref is the virtual internal potential; U0 is the voltage base value.

[0060] Step 2: Calculate the voltage drop based on the mathematical model of the inverter power supply to obtain the virtual impedance value;

[0061] Specifically, the virtual impedance in step 2 is a variable impedance, and the calculation step of the virtual impedance includes:

[0062] Z v =R v +jX v ;

[0063] The resistance component R v for:

[0064] X v =n X / R R v ;

[0065] Where Z v is the virtual impedance value; R v is the resistance component; X v is the reactance component; j is the imaginary unit; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

[0066] Furthermore, when solving the virtual impedance, the short-circuit current during the fault period needs to be limited within the safety range of the converter device, and the resistance component of the virtual impedance is solved by the current limiting amplitude and the starting threshold of the inverter power supply:

[0067]

[0068] Where R v is the resistance component; E is the difference between the virtual internal potential and the grid connection point voltage; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

[0069] Step 3: Based on the virtual impedance value, the filter circuit equation and the virtual impedance control equation are combined to obtain the solution equation of the inverter current;

[0070] The filter circuit equation in step 3 includes:

[0071]

[0072] Where E ref is the virtual internal potential; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; R f is the resistance of the filter; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; X f is the impedance of the filter; L f is the inductance of the filter.

[0073] Furthermore, the solution equation for the inverter current in step 3 of the present application is:

[0074]

[0075] where i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronously rotating coordinate system; s is the complex domain operator; L is the equivalent inductance; R is the equivalent resistance; X is the equivalent reactance; E ref is the virtual internal potential; i q (0) is the q-axis current value of the short-circuit current at time 0; i d (0) is the d-axis current value of the short-circuit current at time 0; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronously rotating coordinate system.

[0076] Step 4: Obtain an expression for the short-circuit current of the inverter power supply according to the solution equation of the inverter current, and obtain the short-circuit current of the corresponding inverter power supply based on the expression for the short-circuit current of the inverter power supply.

[0077] Specifically, when the short-circuit current expression of the inverter power supply is obtained according to the calculation result of the solution equation of the inverter current in the step 4, the short-circuit current expression of the inverter power supply is obtained by performing an inverse Park transformation on the calculation result of the solution equation of the inverter current. Specifically, the short-circuit current expression of the inverter power supply is:

[0078]

[0079] in:

[0080]

[0081] Where i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; t is the time variable; R is the equivalent resistance; X is the equivalent reactance; E ref is the virtual internal potential; i q (0) is the q-axis current value of the short-circuit current at time 0; i d (0) is the d-axis current value of the short-circuit current at time 0; ω is the actual value of the virtual speed of the virtual synchronous generator; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; Z is the virtual impedance value; τ is the decay time constant.

[0082] In addition, combined Figure 3 As shown, this embodiment simulates and calculates the short-circuit current of the grid-forming inverter power supply under the fault state based on the above-mentioned inverter power supply short-circuit current calculation method. It can be seen that the simulation results and calculation results for the inverter power supply are almost completely consistent, which shows that the inverter power supply short-circuit current calculation method of this embodiment can realize the accurate calculation of the short-circuit current of the inverter power supply in the corresponding scenario, and its calculation result is highly accurate, so it can achieve stable control of the power grid during the fault.

[0083] Further, combined with Figure 4 As shown, the present application also discloses a device for calculating short-circuit current of an inverter power supply based on virtual impedance control, the device comprising:

[0084] A model building module, used to obtain the topological structure of the inverter power supply, and establish a mathematical model of the corresponding inverter power supply according to the topological structure, wherein in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control;

[0085] An impedance calculation module, used for calculating the voltage drop based on a mathematical model of the inverter power supply to obtain a virtual impedance value;

[0086] A current solving module, used for obtaining a solution equation of an inverter current based on a virtual impedance value simultaneous filter circuit equation and a virtual impedance control equation;

[0087] The current output module is used to obtain the short-circuit current expression of the inverter power supply according to the solution equation of the inverter current, and obtain the short-circuit current of the corresponding inverter power supply based on the short-circuit current expression of the inverter power supply.

[0088] The device provided in the embodiment of the present application can achieve Figure 1 To avoid repetition, the various processes implemented by the method embodiment will not be described again here.

[0089] like Figure 5 As shown, the embodiment of the present application also provides an electronic device, including a processor and a memory, a program or instruction stored in the memory and executable on the processor, and when the program or instruction is executed by the processor, the following is achieved: Figure 1 The various processes of the method embodiment shown in the figure can achieve the same technical effect. To avoid repetition, they will not be described again here.

[0090] The embodiment of the present application also provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0091] The present application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0092] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned sequence numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

[0093] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0094] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another device, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0095] The units described above as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units; they may be located in one place or distributed on multiple network units; some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0096] In addition, all functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may be a separate unit, or two or more units may be integrated into one unit; the above-mentioned integrated units may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0097] A person skilled in the art can understand that all or part of the steps of implementing the above method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM), magnetic disks or optical disks, etc., various media that can store program codes.

[0098] Alternatively, if the above-mentioned integrated unit of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application can essentially or in other words, the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a device (which can be a terminal or a platform, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0099] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for calculating short-circuit current of an inverter power supply based on virtual impedance control, characterized in that: The steps include: Acquire the topological structure of the inverter power supply, and establish a mathematical model of the corresponding inverter power supply according to the topological structure, wherein in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control; The voltage drop is calculated based on the mathematical model of the inverter power supply to obtain the virtual impedance value; A solution equation for the inverter current is obtained based on the virtual impedance value simultaneous filter circuit equation and the virtual impedance control equation; The short-circuit current expression of the inverter power supply is obtained according to the solution equation of the inverter current, and the short-circuit current of the corresponding inverter power supply is obtained based on the short-circuit current expression of the inverter power supply.

2. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 1, characterized in that: The fault ride-through control strategy is a low voltage ride-through control strategy, and the low voltage ride-through control strategy includes: in is the d-axis voltage reference value in the synchronous rotating coordinate system after voltage reduction; is the q-axis voltage reference value in the synchronous rotating coordinate system after voltage reduction; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; R v is the resistance component; L v is the virtual inductance; ω is the actual value of the virtual speed of the virtual synchronous generator.

3. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 1, characterized in that: The inverter power supply adopts virtual synchronous machine control, and the virtual synchronous machine control includes active power-frequency control and reactive power-voltage control. The basic equation of the virtual synchronous machine control includes: Where P ref is the active reference value; P e is the actual value of active power; D is the damping coefficient; ω N is the virtual speed rated value of the virtual synchronous generator; ω is the virtual speed actual value of the virtual synchronous generator; J is the virtual inertia, which is used to simulate the time delay caused by the magnetic flux of the virtual synchronous generator; θ ref is the virtual internal potential phase angle; k q is the reactive power-voltage droop coefficient; Q ref is the reactive power reference value; Q e is the actual reactive power value; E ref is the virtual internal potential; U0 is the voltage base value.

4. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 1, characterized in that: The filter circuit equation includes: Where E ref is the virtual internal potential; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronous rotating coordinate system; R f is the resistance of the filter; i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronous rotating coordinate system; X f is the impedance of the filter; L f is the inductance of the filter.

5. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 1, characterized in that: The virtual impedance is a variable impedance, and the calculation step of the virtual impedance includes: Z v =R v +jX v ; The resistance component R v for: X v =n X / R R v ; Where Z v is the virtual impedance value; R v is the resistance component; X v is the reactance component; j is the imaginary unit; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

6. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 5, characterized in that: When solving the virtual impedance, the short-circuit current during the fault period needs to be limited to the safety range of the converter equipment. The resistance component of the virtual impedance is solved by the current limiting amplitude and the starting threshold of the inverter power supply: Where R v is the resistance component; E is the voltage difference between the virtual internal potential and the grid connection point; I max The maximum current value allowed by the inverter; n X / R is the proportionality coefficient.

7. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 1, characterized in that: The solution equation of the inverter current includes: where i d is the d-axis current output in the synchronous rotating coordinate system; i q is the q-axis current output in the synchronously rotating coordinate system; s is the complex domain operator; L is the equivalent inductance; R is the equivalent resistance; X is the equivalent reactance; E ref is the virtual internal potential; i q (0) is the q-axis current value of the short-circuit current at time 0; i d (0) is the d-axis current value of the short-circuit current at time 0; u d is the d-axis voltage of the grid-connected point in the synchronous rotating coordinate system; u q is the q-axis voltage of the grid-connected point in the synchronously rotating coordinate system.

8. The method for calculating short-circuit current of an inverter power supply based on virtual impedance control according to claim 7, characterized in that: The step of obtaining the short-circuit current expression of the inverter power supply according to the calculation result of the solution equation of the inverter current comprises: The calculation result of the solution equation of the inverter current is subjected to an inverse Park transformation to obtain the short-circuit current expression of the inverter power supply.

9. A device for calculating short-circuit current of an inverter power supply based on virtual impedance control, characterized in that: The device comprises: A model building module, used to obtain the topological structure of the inverter power supply, and establish a mathematical model of the corresponding inverter power supply according to the topological structure, wherein in a fault state, the inverter power supply adopts a fault ride-through control strategy based on virtual impedance control; An impedance calculation module, used for calculating the voltage drop based on a mathematical model of the inverter power supply to obtain a virtual impedance value; A current solving module, used for obtaining a solution equation of an inverter current based on a virtual impedance value simultaneous filter circuit equation and a virtual impedance control equation; The current output module is used to obtain the short-circuit current expression of the inverter power supply according to the solution equation of the inverter current, and obtain the short-circuit current of the corresponding inverter power supply based on the short-circuit current expression of the inverter power supply.

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