Method and apparatus for suppressing transient current of grid-forming converter, computing device, computer-readable storage medium, and computer program product

Abstract

Embodiments of the present invention provide a method and apparatus for suppressing transient current of a grid-forming converter, a computing device, a computer-readable storage medium, and a computer program product. The suppressing method comprises: calculating first virtual impedance on the basis of an actual voltage instantaneous value of a point of common coupling; calculating second virtual impedance on the basis of an actual current maximum amplitude of the point of common coupling; and suppressing the transient current of the grid-forming converter on the basis of the first virtual impedance and the second virtual impedance. In this way, by combining the actual voltage instantaneous value of the point of common coupling and the actual current maximum amplitude of the point of common coupling, transient current can be suppressed at the moment when a fault occurs in a grid-forming converter, thereby avoiding misoperation triggering of a protection apparatus, and ensuring that the grid-forming converter can restore stable operation once the fault is removed.

Description

A method for suppressing transient current of a grid-type converter, a suppression device, a computing device, a computer-readable storage medium, and a computer program product

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The embodiments of the present disclosure are based on Chinese patent application number 202410316308.0, application date March 20, 2024, and application name “A method and device for suppressing transient current of a grid-type converter”, and claim the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into the present disclosure as a reference. Technical Field

[0003] The present disclosure relates to, but is not limited to, the field of converters, and in particular to a method, a suppression device, a computing device, a computer-readable storage medium, and a computer program product for suppressing transient current in a grid-type converter. Background Art

[0004] With the rapid development of DC transmission technology, grid-type converters and grid-type converters have been widely used in the field of grid connection. The grid-type converter maintains synchronization with the power grid through a phase-locked loop. Therefore, when the phase, frequency, and voltage disturbances occur in the power grid, the grid-type converter will not spontaneously provide support. The grid-type converter exhibits voltage source characteristics and can be equivalent to a controlled voltage source. As shown in Figure 1, the grid-type converter 10 is connected to the power grid (PG) through the point of common coupling (PCC). u_(v_ref) represents the internal potential of the grid-type converter, U_ref represents the amplitude of the internal potential of the grid-type converter, and θ_ref represents the phase of the internal potential of the grid-type converter. Z_con represents the impedance of the grid-type converter, Z_sys represents the system impedance, and u_s represents the grid voltage. As can be seen from Figure 1, the grid-type converter can spontaneously provide active and reactive power support, which is conducive to the stable operation of the power grid.

[0005] When a short-circuit fault such as a single-phase grounding fault occurs in a grid-type converter, the grid-type converter maintains the internal potential unchanged and causes a large transient current. However, the transient current that the grid-type converter can tolerate is about 1.5 pu (per unit). Therefore, a transient current exceeding the tolerable transient current will endanger the safe operation of the grid-type converter. The related technology usually switches from a grid-connected grid-type converter to a grid-following converter. The grid-following converter uses inner-loop current control and outer-loop voltage control to directly limit the transient current of the grid-type converter. However, the switching process is likely to cause oscillation of the power grid, and the limitation of the current reference value in the inner-loop current control is likely to cause the inner-loop current control output to be saturated, causing the outer-loop voltage control to lose its control ability, resulting in the grid-type converter being unable to operate stably. Summary of the Invention

[0006] In order to solve the problem that the grid-type converter in the prior art cannot operate stably, an embodiment of the present disclosure provides a method for suppressing the transient current of the grid-type converter, including: calculating a first virtual impedance based on the actual instantaneous value of the voltage at the grid-connected point; calculating a second virtual impedance based on the maximum amplitude of the actual current at the grid-connected point; and suppressing the transient current of the grid-type converter based on the first virtual impedance and the second virtual impedance.

[0007] In some embodiments, the calculating of the first virtual impedance according to the actual instantaneous voltage value of the grid-connected point includes: obtaining the actual instantaneous voltage value of the grid-connected point; and calculating the first virtual impedance according to the following formula:

[0008] Among them, Z u represents the first virtual impedance, u pccabc Indicates the actual instantaneous value of the voltage at the grid connection point, u vabc_ref Represents the instantaneous value of the first reference voltage of the grid-type converter, I limit Indicates the maximum current amplitude that the grid-type converter can withstand, Z con Indicates the impedance of the grid-type converter.

[0009] In some embodiments, the first virtual impedance satisfies:

[0010] in, Indicates the output voltage amplitude of the grid-type converter under the maximum modulation ratio, U pccmin Indicates the minimum voltage amplitude at the grid connection point in the event of a grid fault.

[0011] In some embodiments, the second virtual impedance is calculated as follows:

[0012] Z i =K i (I max -I limit );

[0013] Among them, Z i Represents the second virtual impedance, K i Represents the proportionality coefficient, I max Indicates the maximum actual current amplitude at the grid connection point.

[0014] Exemplarily, the second virtual impedance satisfies:

[0015] In some embodiments, the above-mentioned suppression of the transient current of the mesh converter based on the first virtual impedance and the second virtual impedance includes: calculating the virtual reactance of the mesh converter and the virtual resistance of the mesh converter based on the first virtual impedance and the second virtual impedance; calculating the virtual impedance voltage compensation value of the mesh converter based on the virtual reactance of the mesh converter and the virtual resistance of the mesh converter; calculating the instantaneous value of the second reference voltage of the mesh converter based on the virtual impedance voltage compensation value of the mesh converter; modulating the instantaneous value of the second reference voltage of the mesh converter to obtain a drive signal, and controlling the mesh converter according to the drive signal.

[0016] In some embodiments, the virtual reactance of the grid-type converter and the virtual resistance of the grid-type converter respectively satisfy:

[0017] X ui =X u +X i ;

[0018] R ui =R u +R i ;

[0019] Among them, X ui represents the virtual reactance of the grid-type converter, R ui Represents the virtual resistance of the grid-type converter, R u Represents the first virtual resistor, X u Represents the first virtual reactance, R i Represents the second virtual resistor, X i represents the second virtual reactance and satisfies

[0020] Exemplarily, the virtual impedance voltage compensation value of the grid-type converter satisfies:

[0021] Where Δu abc_ref Indicates the virtual impedance voltage compensation value of the grid-type converter, i abc It represents the actual current value at the grid connection point, and f represents the frequency of the grid.

[0022] Exemplarily, the instantaneous value of the second reference voltage of the grid-type converter satisfies:

[0023] in, Indicates the instantaneous value of the second reference voltage of the grid-type converter.

[0024] It can be seen that the present invention obtains the instantaneous value of the second reference voltage of the mesh type converter through the virtual impedance voltage compensation value of the mesh type converter. The instantaneous value of the second reference voltage of the mesh type converter can be smaller than the instantaneous value of the first reference voltage of the mesh type converter, which means that the transient current of the mesh type converter is suppressed.

[0025] In another aspect, the present disclosure further provides a device for suppressing transient current of a grid-type converter, comprising:

[0026] The first calculation module is configured to calculate the first virtual impedance according to the actual instantaneous value of the voltage at the grid connection point.

[0027] The second calculation module is configured to calculate the second virtual impedance according to the maximum magnitude of the actual current of the grid connection point.

[0028] A suppression module is configured to suppress the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance.

[0029] On the other hand, an embodiment of the present disclosure further provides a computing device, including: a processor and a memory, wherein the memory stores a computer program that can be run on the processor, and the processor implements the above method when executing the computer program.

[0030] On the other hand, an embodiment of the present disclosure further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the processor implements the above method when executing the computer program.

[0031] On the other hand, an embodiment of the present disclosure further provides a computer program product, including a non-transitory computer-readable storage medium storing a computer program, and the computer program implements the above method when read and executed by a computer.

[0032] Compared with the prior art, the embodiments of the present disclosure have the following beneficial effects:

[0033] In the method for suppressing transient current of a grid-type converter provided in an embodiment of the present disclosure, the actual instantaneous value of the voltage at the grid-connected point and the actual maximum current at the grid-connected point are combined, which can suppress the transient current at the moment when a fault occurs in the grid-type converter, avoid triggering malfunction of the protection device, and ensure that the grid-type converter can resume stable operation after the fault disappears.

[0034] The second virtual impedance of the embodiment of the present disclosure is determined according to the maximum amplitude of the actual current at the grid connection point, and can compensate for the deficiency of the voltage prediction response when the transient current variation is close to being flat but the value is large.

[0035] The embodiments of the present disclosure have a wide range of applications and can be applied to various scenarios including wind power, photovoltaic, energy storage or flexible direct current transmission systems including grid-type converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present disclosure or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0037] FIG1 is a schematic diagram of a grid-connected equivalent circuit of a grid-connected converter according to an embodiment of the present disclosure;

[0038] FIG2 is a flow chart of a method for suppressing transient current of a grid-type converter according to an embodiment of the present disclosure;

[0039] FIG3 is another flow chart of a method for suppressing transient current of a grid-type converter according to an embodiment of the present disclosure;

[0040] FIG4a is a schematic diagram of the actual instantaneous voltage value of the grid connection point without transient current suppression in the case of a single-phase grounding fault in an embodiment of the present disclosure;

[0041] FIG4 b is a schematic diagram of actual current values ​​at the grid connection point without transient current suppression in the case of a single-phase grounding fault according to an embodiment of the present disclosure;

[0042] FIG5a is a schematic diagram of actual instantaneous voltage values ​​at a grid connection point during transient current suppression in the event of a single-phase grounding fault in an embodiment of the present disclosure;

[0043] FIG5 b is a schematic diagram of actual current values ​​at a grid-connected point during transient current suppression in the event of a single-phase grounding fault in an embodiment of the present disclosure;

[0044] FIG5c is a schematic diagram of a virtual impedance for transient current suppression in the case of a single-phase grounding fault in an embodiment of the present disclosure;

[0045] FIG6 is a schematic structural diagram of a device for suppressing transient current of a grid-type converter according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0046] To help those skilled in the art better understand the present disclosure, the following will provide a clear and complete description of the technical solutions in the embodiments of the present disclosure, in conjunction with the accompanying drawings. It is clear that the described embodiments are only a portion of the embodiments of the present disclosure, not all of them. All other embodiments derived by those skilled in the art based on the embodiments of the present disclosure without creative effort are within the scope of protection of the present disclosure.

[0047] The technical solutions in this disclosure will be described below with reference to the accompanying drawings.

[0048] The terms "first," "second," and the like in the description, embodiments, claims, and drawings of the present disclosure are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or order. Furthermore, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions, such as, for example, inclusion of a series of steps or units. A method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0049] It should be understood that in the present disclosure, "at least one (item)" refers to one or more, and "plurality" refers to two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0050] The embodiment of the present disclosure provides a method for suppressing transient current of a grid-type converter, as shown in Figures 2 and 3. The suppression method includes the following steps:

[0051] Step S1: Calculate a first virtual impedance according to the actual instantaneous value of the voltage at the grid connection point.

[0052] Step S2: Calculate the second virtual impedance according to the maximum actual current amplitude of the grid connection point.

[0053] Step S3: suppressing the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance.

[0054] In some embodiments, the calculation of the first virtual impedance according to the actual instantaneous voltage value of the grid connection point in the above step S1 includes: obtaining the actual instantaneous voltage value of the grid connection point. The first virtual impedance is calculated according to the following formula:

[0055] Among them, Z u represents the first virtual impedance, u pccabc Indicates the actual instantaneous value of the voltage at the grid connection point, u vabc_ref Represents the instantaneous value of the first reference voltage of the grid-type converter, I limit Indicates the maximum current amplitude that the grid-type converter can withstand, Zcon Indicates the impedance of the grid-type converter.

[0056] In some embodiments, the first virtual impedance Z u satisfy:

[0057] in, Indicates the output voltage amplitude of the grid-type converter under the maximum modulation ratio, U pccmin Indicates the minimum voltage amplitude at the grid connection point in the event of a grid fault.

[0058] In some other embodiments, the second virtual impedance is calculated as follows:

[0059] Z i =K i (I max -I limit );

[0060] Among them, Z i Represents the second virtual impedance, K i Represents the proportionality coefficient, I max Indicates the maximum actual current amplitude at the grid connection point.

[0061] For example, the second virtual impedance Z i satisfy:

[0062] In some embodiments, the step S3 of suppressing the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance includes:

[0063] Step S301: Calculate the virtual reactance and the virtual resistance of the grid-type converter according to the first virtual impedance and the second virtual impedance.

[0064] Step S302: Calculating a virtual impedance voltage compensation value of the mesh converter according to the virtual reactance and the virtual resistance of the mesh converter.

[0065] Step S303: Calculating a second reference voltage instantaneous value of the grid-type converter according to the virtual impedance voltage compensation value of the grid-type converter.

[0066] Step S304: modulating the instantaneous value of the second reference voltage of the grid-type converter to obtain a driving signal, and controlling the grid-type converter according to the driving signal, that is, controlling the action of the switch tube in the grid-type converter.

[0067] It is understandable that the priority between the first virtual impedance and the second virtual impedance and whether to be put into use at the same time can be adjusted according to demand.

[0068] In some embodiments, the virtual reactance of the meshed converter and the virtual resistance of the meshed converter in step S301 respectively satisfy:

[0069] X ui =X u +X i ;

[0070] R ui =R u +R i ;

[0071] Among them, X ui represents the virtual reactance of the grid-type converter, R ui Represents the virtual resistance of the grid-type converter, R u Represents the first virtual resistor, X u Represents the first virtual reactance, R i Represents the second virtual resistor, X i represents the second virtual reactance and satisfies

[0072] Exemplarily, the virtual impedance voltage compensation value of the grid-type converter in step S302 satisfies:

[0073] Where Δu abc_ref Indicates the virtual impedance voltage compensation value of the grid-type converter, i abc It represents the actual current value at the grid connection point, and f represents the frequency of the grid.

[0074] In some embodiments, the instantaneous value of the second reference voltage of the grid-type converter in step S303 satisfies:

[0075] in, Indicates the instantaneous value of the second reference voltage of the grid-type converter.

[0076] It can be seen that the suppression method provided by the embodiment of the present disclosure obtains the instantaneous value of the second reference voltage of the mesh type converter through the virtual impedance voltage compensation value of the mesh type converter. The instantaneous value of the second reference voltage of the mesh type converter can be smaller than the instantaneous value of the first reference voltage of the mesh type converter, thereby achieving the suppression of the transient current of the mesh type converter.

[0077] As shown in FIG3 , the instantaneous value of the second reference voltage of the mesh-type converter can be modulated by a modulator using pulse width modulation or the like to obtain a driving signal. The driving signal can drive the switch tube in the mesh-type converter 10 to operate, thereby ultimately suppressing the transient current of the mesh-type converter.

[0078] In some embodiments, taking a single-phase grounding fault of 500ms (i.e., the duration of the single-phase grounding fault) occurring at the grid-connected point of a three-phase grid-connected converter as an example, the actual instantaneous voltage value u pccabc In Figures 4a and 5a, the horizontal axis represents time t (in seconds). If the transient current of the grid-connected converter is not suppressed, it can be seen from Figure 4b that the actual current value i abc By adopting the suppression method provided by the embodiment of the present disclosure, that is, inputting virtual impedance (in FIG5c, virtual reactance X ui As shown in Figure 5b, the maximum peak value of the transient current of the grid-type converter is about 1.5pu. During the duration of the single-phase grounding fault, the transient current peak is suppressed to within 1.4pu. After the single-phase grounding fault ends, the virtual impedance is exited and the power grid can resume stable operation.

[0079] Of course, the technical solution provided by the embodiment of the present disclosure can be applied not only to the three-phase coordinate system, but also to the αβ coordinate system or the dq coordinate system, etc., and is not limited by the coordinate system of the meshed controller.

[0080] The following describes the application of the method for suppressing transient current of a grid-type converter provided by an embodiment of the present disclosure in a practical scenario.

[0081] The equivalent circuit of the grid-connected grid-connected converter is shown in Figure 3. The basic principle of achieving transient current suppression is: transient current suppression is achieved through the superposition of voltage prediction and current compensation. pccabc is the measured instantaneous value of the grid connection point voltage, u vabc_ref The valve voltage reference value generated for the grid-type control is used. The voltage prediction link measures and calculates the maximum instantaneous difference between the two when a fault occurs, combined with the maximum transient current limit I allowed by the converter. limit , calculate the virtual impedance modulus Z that should be invested u The current compensation link measures the grid-connected current i abc The maximum current amplitude and I limit The difference is calculated to obtain the virtual impedance modulus Z to be compensated i According to the output of the above two links, the instantaneous reference value of the virtual impedance voltage Δu is generated. abc_ref , and the instantaneous value of the voltage reference u output by the grid control vabc_ref The reference instantaneous value of the converter output voltage that together constitutes the actual output

[0082] The method for suppressing transient current of a grid-type converter provided in an embodiment of the present disclosure includes the following steps:

[0083] Step 1: Measure and calculate the amplitude deviation between the grid connection point voltage and the reference value and select the maximum value.

[0084] Measure the instantaneous value of the system grid connection point voltage u pccabc , minus the instantaneous reference value u of the converter voltage generated by the grid-type control vabc_ref , get the difference of the maximum voltage amplitude of the fundamental frequency ΔU max .

[0085] Step 2: Calculate the virtual impedance Z based on the voltage prediction u .

[0086] According to the ΔU obtained in step 1 max , and the maximum current amplitude that the converter can withstand I limit , predict the required total impedance modulus Use Z u_con Subtract the converter's own impedance Z con (X con Including the converter bridge arm impedance and transformer impedance, etc.), the virtual impedance Z that should be input is obtained u =Z u_con -Z con . Virtual reactance X based on voltage prediction u and virtual resistor R u satisfy It can also be in pure reactance form.

[0087] Step 3: Set the upper and lower limits of the voltage-based predicted virtual impedance.

[0088] Set the virtual impedance value Z based on voltage prediction u The upper limit is U* vmax is the output voltage amplitude when the converter is at maximum modulation, U pccmin The minimum amplitude of the system grid connection point under fault conditions. Set the virtual impedance lower limit modulus to 0, 0≤Z i ≤Z lim_up .

[0089] Step 4: Calculate the virtual impedance Z based on current compensation i .

[0090] Calculate the virtual impedance value Z based on current compensation i =K i (I max -I limit ), where I max To measure the grid-connected current i abc Maximum current amplitude, K i Is the proportional coefficient, used to adjust the compensation degree of this link. The virtual reactance X based on current compensation i and virtual resistor Ri satisfy It can also be in pure reactance form.

[0091] Step 5: Set the upper and lower limits of the current compensation virtual impedance.

[0092] Set the virtual impedance value Z based on current compensation i The upper limit is Z lim_up -Z u , the lower limit is -Z u , -Z u ≤Z i ≤Z lim_up -Z u .

[0093] Step 6: Calculate the virtual impedance based on voltage prediction and current compensation.

[0094] The final virtual reactance X put into the system is calculated ui =X u +X i , virtual resistance R ui =R u +R i .

[0095] Step 7: Generate a virtual impedance compensation voltage reference value and superimpose it with the network control voltage reference value.

[0096] The voltage compensation value is calculated according to step 6 where i abc is the current measurement value. Instantaneous reference value of converter output voltage

[0097] The technical effects achieved by the embodiments of the present disclosure are as follows: taking the case where a single-phase grounding fault occurs at the grid-connected point of a three-phase coordinate system for 500ms as an example, the voltage measurement value u at the grid-connected point is pccabc As shown in Figure 4(a) and Figure 4(b), without the transient current suppression strategy, the virtual impedance has no output value, and the instantaneous value of the grid-connected current i abc As shown in Figures 5(a), 5(b), and 5(c), after implementing the suppression strategy provided by the embodiments of the present disclosure, virtual impedance is instantaneously activated, resulting in an instantaneous overcurrent of approximately 1.5 pu. This overcurrent is suppressed to less than 1.4 pu during the fault, and virtual impedance is removed after the fault ends, allowing the system to resume stable operation.

[0098] Based on the same inventive concept, the embodiment of the present disclosure also provides a device for suppressing transient current of a grid-type converter, as shown in FIG6 . The suppression device 10 may include:

[0099] A first calculation module 1 is configured to calculate a first virtual impedance according to an actual instantaneous voltage value of the grid connection point;

[0100] A second calculation module 2 is configured to calculate a second virtual impedance according to the maximum actual current amplitude of the grid connection point;

[0101] The suppression module 3 is configured to suppress the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance.

[0102] In some embodiments, the first calculation module 1 is further configured to obtain the actual instantaneous voltage value of the grid connection point and calculate the first virtual impedance according to the following formula:

[0103] Among them, Z u represents the first virtual impedance, u pccabc Indicates the actual instantaneous value of the voltage at the grid connection point, u vabc_ref Represents the instantaneous value of the first reference voltage of the grid-type converter, I limit Indicates the maximum current amplitude that the grid-type converter can withstand, Z con Indicates the impedance of the grid-type converter.

[0104] In some embodiments, the first virtual impedance Z u satisfy:

[0105] in, Indicates the output voltage amplitude of the grid-type converter under the maximum modulation ratio, U pccmin Indicates the minimum voltage amplitude at the grid connection point in the event of a grid fault.

[0106] In some other embodiments, the second calculation module 2 calculates the second virtual impedance according to the following formula:

[0107] Z i =K i (I max -I limit );

[0108] Where Z i Represents the second virtual impedance, K i Represents the proportionality coefficient, I max Indicates the maximum actual current amplitude of the grid-connected point. For example, the second virtual impedance Z i satisfy:

[0109] In some embodiments, the suppression module 3 is further configured to: calculate the virtual reactance of the mesh converter and the virtual resistance of the mesh converter based on the first virtual impedance and the second virtual impedance; calculate the virtual impedance voltage compensation value of the mesh converter based on the virtual reactance of the mesh converter and the virtual resistance of the mesh converter; calculate the instantaneous value of the second reference voltage of the mesh converter based on the virtual impedance voltage compensation value of the mesh converter; modulate the instantaneous value of the second reference voltage of the mesh converter to obtain a driving signal, and control the mesh converter according to the driving signal, that is, control the action of the switching tube in the mesh converter.

[0110] In some embodiments, the virtual reactance of the grid-type converter and the virtual resistance of the grid-type converter respectively satisfy:

[0111] X ui =X u +X i ;

[0112] R ui =R u +R i ;

[0113] Among them, X ui represents the virtual reactance of the grid-type converter, R ui Represents the virtual resistance of the grid-type converter, R u Represents the first virtual resistor, X u Represents the first virtual reactance, R i Represents the second virtual resistor, X i represents the second virtual reactance and satisfies

[0114] Exemplarily, the virtual impedance voltage compensation value of the grid-type converter satisfies:

[0115] Where Δu abc_ref Indicates the virtual impedance voltage compensation value of the grid-type converter, i abc It represents the actual current value at the grid connection point, and f represents the frequency of the grid.

[0116] In some embodiments, the instantaneous value of the second reference voltage of the grid-type converter satisfies:

[0117] in, Indicates the instantaneous value of the second reference voltage of the grid-type converter.

[0118] It can be seen that the suppression device 10 provided in the embodiment of the present disclosure obtains the second reference voltage instantaneous value of the mesh type converter through the virtual impedance voltage compensation value of the mesh type converter. The second reference voltage instantaneous value of the mesh type converter can be smaller than the first reference voltage instantaneous value of the mesh type converter, thereby achieving the suppression of the transient current of the mesh type converter.

[0119] Based on the same inventive concept, an embodiment of the present disclosure further provides a computer device, which includes a processor and a memory, the memory being used to store a computer program, the computer program including program instructions, and the processor being used to execute the program instructions stored in a computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a computer storage medium to implement a corresponding method flow or corresponding function, so as to implement the steps of the suppression method provided in the above embodiment.

[0120] Based on the same inventive concept, the embodiment of the present disclosure also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the suppression method provided in the above embodiment.

[0121] Those skilled in the art will appreciate that the embodiments of the present disclosure may be provided as methods, systems, or computer program products. Therefore, the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present disclosure may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0122] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0123] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0124] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0125] The above are merely embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure are included in the scope of the claims of the present disclosure to be approved. Industrial Applicability

[0126] The disclosed embodiments provide a method and apparatus for suppressing transient current in a grid-type converter, wherein the image processing method includes: calculating a first virtual impedance based on the instantaneous value of the actual voltage at the grid connection point; calculating a second virtual impedance based on the maximum amplitude of the actual current at the grid connection point; and suppressing the transient current of the grid-type converter based on the first and second virtual impedances. This approach can suppress transient current at the moment a fault occurs in the grid-type converter, preventing the protection device from malfunctioning, and ensuring that the grid-type converter can resume stable operation after the fault disappears.

Claims

1. A method for suppressing transient current of a grid-type converter, wherein: The inhibition method comprises: Calculating a first virtual impedance according to an actual instantaneous voltage value of the grid connection point; Calculating a second virtual impedance according to the maximum magnitude of the actual current at the grid connection point; The transient current of the grid-type converter is suppressed according to the first virtual impedance and the second virtual impedance.

2. The method according to claim 1, wherein: The calculating the first virtual impedance according to the actual instantaneous voltage value of the grid connection point includes: Obtaining an actual instantaneous voltage value of the grid connection point; The first virtual impedance is calculated as follows: Among them, Z u represents the first virtual impedance, u pccabc Indicates the actual instantaneous voltage value of the grid connection point, u vabc_ref represents the instantaneous value of the first reference voltage of the grid-type converter, I limit Indicates the maximum current amplitude that the grid-type converter can withstand, Z con represents the impedance of the grid-type converter.

3. The method of claim 2, wherein: The first virtual impedance satisfies: in, It represents the output voltage amplitude of the grid-type converter under the maximum modulation ratio, U pccmin Indicates the minimum voltage amplitude of the grid connection point in the event of a grid fault.

4. The method of claim 3, wherein: The second virtual impedance is calculated as follows: i =K i (I max -I limit ); Among them, Z i Represents the second virtual impedance, K i Represents the proportionality coefficient, I max Indicates the maximum actual current amplitude of the grid-connected point.

5. The method of claim 4, wherein: The second virtual impedance satisfies:

6. The method of claim 5, wherein: The suppressing the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance includes: Calculating a virtual reactance of the grid-type converter and a virtual resistance of the grid-type converter according to the first virtual impedance and the second virtual impedance; Calculating a virtual impedance voltage compensation value of the mesh converter according to the virtual reactance of the mesh converter and the virtual resistance of the mesh converter; Calculating a second reference voltage instantaneous value of the meshed converter according to the virtual impedance voltage compensation value of the meshed converter; The instantaneous value of the second reference voltage of the grid-type converter is modulated to obtain a driving signal, and the grid-type converter is controlled according to the driving signal.

7. The method of claim 6, wherein: The virtual reactance of the grid-type converter and the virtual resistance of the grid-type converter respectively satisfy: X ui =X u +X i ; R ui =R u +R i ; Among them, X ui represents the virtual reactance of the grid-type converter, R ui represents the virtual resistance of the grid-type converter, R u Represents the first virtual resistor, X u Represents the first virtual reactance, R i Represents the second virtual resistor, X i represents the second virtual reactance and satisfies 8. The method of claim 7, wherein: The virtual impedance voltage compensation value of the grid-type converter satisfies: Where Δu abc_ref represents the virtual impedance voltage compensation value of the grid-type converter, i abc represents the actual current value of the grid connection point, and f represents the frequency of the grid.

9. The method of claim 8, wherein: The instantaneous value of the second reference voltage of the grid-type converter satisfies: in, Represents the instantaneous value of the second reference voltage of the grid-type converter.

10. A device for suppressing transient current of a grid-type converter, wherein: The suppression device comprises: A first calculation module is configured to calculate a first virtual impedance according to an actual instantaneous voltage value of the grid connection point; A second calculation module is configured to calculate a second virtual impedance according to a maximum magnitude of an actual current at the grid connection point; A suppression module is configured to suppress the transient current of the grid-type converter according to the first virtual impedance and the second virtual impedance.

11. A computing device comprising a processor and a memory, wherein the memory stores a computer program executable on the processor, and the processor implements the method according to any one of claims 1 to 9 when executing the computer program.

12. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method according to any one of claims 1 to 9 is implemented.

13. A computer program product, comprising a non-transitory computer-readable storage medium storing a computer program, wherein the computer program implements the method according to any one of claims 1 to 9 when read and executed by a computer.

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