A method and apparatus for calculating short circuit current of a flexible HVDC feeding an AC grid

Abstract

The application discloses a method and device for calculating short-circuit current of a flexible DC feeder into an AC power grid, and the method comprises the following steps: determining the voltage U of a PCC bus according to a system network diagram generated after a short-circuit fault of the AC power grid PCC ; comparing the voltage U PCC with a short-time blocking threshold value of a flexible DC converter, wherein: when the voltage U PCC is not greater than the short-time blocking threshold value of the flexible DC converter, the flexible DC is blocked, no short-circuit current is provided for the AC power grid, and the short-circuit current of the flexible DC feeder into the AC power grid is 0; when the voltage U PCC is greater than the short-time blocking threshold value of the flexible DC converter, a flexible DC fault ride-through strategy is read, and the short-circuit current of the flexible DC feeder into the AC power grid is calculated according to the flexible DC fault ride-through strategy. The short-circuit current calculation result obtained by the method and device is closer to the actual operation value, the accuracy of the short-circuit current calculation result of the flexible DC feeder into the AC power grid is improved, and the stability of the power system is fully ensured.

Description

Technical Field

[0001] This invention relates to the field of high-voltage power transmission technology, and more specifically, to a method and apparatus for calculating the short-circuit current of a flexible DC-fed AC power grid, as well as a storage medium and electronic equipment. Background Technology

[0002] The impact of flexible DC transmission on AC grid short-circuit current is typically considered in conjunction with specific flexible DC projects in current planning, design, and operation. Based on the equipment characteristics of the flexible DC converter, it is assumed that during AC faults, the converter injects current into the AC grid according to its maximum current-carrying capacity. Therefore, the common practice for calculating the amplifying effect of flexible DC on AC grid short-circuit current is to actively read the maximum value parameter of the injected current from the flexible DC converter and set a current source at the flexible DC grid connection point according to this maximum injected current to calculate the short-circuit current.

[0003] However, if the short-circuit current is calculated using the above research method, the short-circuit current results are seriously conservative and oversimplify the port characteristics of the flexible DC converter. The changing characteristics of the current injected into the AC grid by the flexible DC converter under various fault ride-through strategies are not considered. That is, it is assumed that the active and reactive components of the current injected into the AC grid by the flexible DC converter are not affected by the fault ride-through strategy. As a result, the short-circuit current calculation results deviate significantly from the actual operating values, which seriously affects the development of power system stability research.

[0004] Therefore, a technology is needed that can fully consider the changing characteristics of the flexible DC-injected AC grid current under various fault ride-through strategies, thereby improving the accuracy of calculating the short-circuit current of the flexible DC-injected AC grid during short-circuit faults in the AC grid. Summary of the Invention

[0005] To address the problem in existing technologies where, during a short-circuit fault in the AC grid, the maximum value of the injected current from the flexible DC converter is actively read, and a current source is set at the flexible DC grid connection point according to this maximum value for short-circuit current calculation, resulting in a large deviation between the calculated short-circuit current and the actual operating value, thus affecting power system stability, this invention provides a method for calculating the short-circuit current fed into the AC grid by a flexible DC converter. The method includes:

[0006] The voltage U of the PCC bus at the flexible DC grid connection point is determined based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC ;

[0007] Compare the voltage U PCC And the short-time blocking threshold of the flexible DC converter, wherein:

[0008] When the voltage U PCCWhen the short-time blocking threshold of the flexible DC converter is not greater than the threshold value, the short-circuit current fed into the AC grid by the flexible DC converter is 0.

[0009] When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is greater than the threshold, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC is calculated based on the flexible DC fault ride-through strategy.

[0010] Furthermore, the voltage U of the PCC bus at the flexible DC grid connection point is determined based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC include:

[0011] After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram.

[0012] The voltage of the PCC bus in the fault component network diagram and the voltage of the PCC bus in the normal component network diagram are linearly superimposed using the superposition method to obtain the voltage U of the PCC bus. PCC .

[0013] Furthermore, when the voltage U PCC When the fault ride-through strategy of the flexible DC converter is greater than the short-term blocking threshold, the fault ride-through current of the flexible DC converter is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the fault ride-through strategy, including:

[0014] When the flexible DC transmission adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC transmission is 0.

[0015] When the flexible DC transmission adopts a constant AC voltage fault ride-through strategy, the voltage U of the PCC bus is compared. PCC The AC voltage reference value U set in the fault ride-through strategy with constant AC voltage REF ,in:

[0016] When U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter.

[0017] When U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid

[0018] Furthermore, when U PCC equal to UREF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. Among them, the short-circuit current of flexible DC feed into AC power grid is calculated. The formula is:

[0019]

[0020] In the formula, The output voltage of the flexible DC converter. Q is the short-circuit current fed into the AC grid by flexible DC. Conv This refers to the reactive power output of the flexible DC converter.

[0021] Furthermore, the statement when U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid Among them, the determination of the short-circuit current of flexible DC feed into AC power grid The expression is:

[0022]

[0023] Among them, the maximum current carrying capacity of the flexible DC converter The calibration is performed based on the maximum operating current of the flexible DC converter.

[0024] According to another aspect of the present invention, an apparatus for calculating the short-circuit current of a flexible DC-fed AC power grid is provided, the apparatus comprising:

[0025] The bus voltage unit is used to determine the voltage U of the PCC bus at the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC ;

[0026] Short-circuit current unit, used to compare the voltage U PCC And the short-time blocking threshold of the flexible DC converter, wherein:

[0027] When the voltage U PCC When the short-time blocking threshold of the flexible DC converter is not greater than the threshold value, the short-circuit current fed into the AC grid by the flexible DC converter is 0.

[0028] When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is greater than the threshold, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC is calculated based on the flexible DC fault ride-through strategy.

[0029] Furthermore, the bus voltage unit determines the voltage U of the PCC bus at the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault in the AC grid. PCC include:

[0030] After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram.

[0031] The voltage of the PCC bus in the fault component network diagram and the voltage of the PCC bus in the normal component network diagram are linearly superimposed using the superposition method to obtain the voltage U of the PCC bus. PCC .

[0032] Furthermore, the short-circuit current unit is located at voltage U. PCC When the fault ride-through strategy of the flexible DC converter is greater than the short-term blocking threshold, the fault ride-through current of the flexible DC converter is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the fault ride-through strategy, including:

[0033] When the flexible DC transmission adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC transmission is 0.

[0034] When the flexible DC transmission adopts a constant AC voltage fault ride-through strategy, the voltage U of the PCC bus is compared. PCC The AC voltage reference value U set in the fault ride-through strategy with constant AC voltage REF ,in:

[0035] When U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter.

[0036] When U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid

[0037] Furthermore, the short-circuit current unit in U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. Among them, the short-circuit current of flexible DC feed into AC power grid is calculated. The formula is:

[0038]

[0039] In the formula, The output voltage of the flexible DC converter. Q is the short-circuit current fed into the AC grid by flexible DC. Conv This refers to the reactive power output of the flexible DC converter.

[0040] Furthermore, the short-circuit current unit in U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid Among them, the determination of the short-circuit current of flexible DC feed into AC power grid The expression is:

[0041]

[0042] Among them, the maximum current carrying capacity of the flexible DC converter The calibration is performed based on the maximum operating current of the flexible DC converter.

[0043] According to another aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program for performing any one of the methods for calculating the short-circuit current of a flexible DC-fed AC grid according to the present invention.

[0044] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising:

[0045] processor;

[0046] Memory used to store the processor's executable instructions;

[0047] The processor is configured to read the executable instructions from the memory and execute the executable instructions to implement any one of the methods for calculating the short-circuit current of a flexible DC-fed AC grid according to the present invention.

[0048] The present invention provides a method and apparatus for calculating the short-circuit current of a flexible DC-DC-integrated AC grid, a storage medium, and an electronic device. The method for calculating the short-circuit current of the flexible DC-DC-integrated AC grid includes: determining the voltage U of the PCC bus at the flexible DC connection point based on a system network diagram generated after a short-circuit fault occurs in the AC grid. PCC Compare the voltage U PCC and the short-time blocking threshold of the flexible DC converter, wherein: when the voltage U PCCWhen the voltage U is not greater than the short-time blocking threshold of the flexible DC converter, the flexible DC converter is blocked, and no short-circuit current is supplied to the AC grid; the short-circuit current fed into the AC grid by the flexible DC converter is 0. PCC When the short-term blocking threshold of the flexible DC converter is exceeded, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC is calculated based on the flexible DC fault ride-through strategy. The method and apparatus calculate the short-circuit current fed into the AC grid by the flexible DC under different fault ride-through strategies when a short-circuit fault occurs in the AC grid. This makes the calculated short-circuit current result closer to the actual operating value, improving the accuracy of the calculated short-circuit current of the flexible DC fed into the AC grid and fully ensuring the stability of the power system. Attached Figure Description

[0049] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0050] Figure 1 A flowchart illustrating a method for calculating the short-circuit current of a flexible DC-fed AC grid according to a preferred embodiment of the present invention;

[0051] Figure 2 A schematic diagram of the structure of a system for calculating the short-circuit current of a flexible DC-fed AC grid according to a preferred embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Detailed Implementation

[0053] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0054] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0055] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0056] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0057] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0058] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0059] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0060] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0061] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0062] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0063] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0064] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0065] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0066] Exemplary methods

[0067] Figure 1 This is a flowchart illustrating a method for calculating the short-circuit current of a flexible DC-fed AC grid according to a preferred embodiment of the present invention. This embodiment can be applied to electronic devices, such as... Figure 1 As shown in the figure, the method for calculating the short-circuit current of a flexible DC-fed AC grid described in this embodiment includes the following steps:

[0068] Step 101: Determine the voltage U of the PCC bus at the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC .

[0069] Optionally, the voltage U of the PCC bus at the flexible DC grid connection point is determined based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC include:

[0070] After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram.

[0071] The voltage of the PCC bus in the fault component network diagram and the voltage of the PCC bus in the normal component network diagram are linearly superimposed using the superposition method to obtain the voltage U of the PCC bus. PCC .

[0072] In one embodiment, the flexible DC-DC converter used in the flexible DC-DC transmission has a maximum power of 3000MW and a maximum operating current of 3kA. When calibrating the maximum current of the 3000MW flexible DC-DC converter, a calibration coefficient of 1.2 is set, and the short-time blocking threshold of the flexible DC-DC converter is 0.2pu. When employing a constant AC voltage control fault ride-through strategy, the AC voltage reference value is set to U. REF =0.8pu, after a short-circuit fault occurs in the AC power grid, the voltage U of the PCC bus after the fault is obtained by drawing the system network diagram. PCC =0.7pu.

[0073] Step 102, compare the voltage U PCC And the short-time blocking threshold of the flexible DC converter, wherein:

[0074] When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is not greater than the threshold value, the flexible DC converter is blocked and no short-circuit current is supplied to the AC grid. The short-circuit current fed into the AC grid by the flexible DC converter is 0.

[0075] When the voltage U PCC When the fault ride-through strategy of the flexible DC converter is greater than the short-term blocking threshold, the fault ride-through strategy of the flexible DC converter is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated according to the fault ride-through strategy.

[0076] In one embodiment, when U PCC When the short-time blocking threshold of the flexible DC converter is less than 0.2 pu, the flexible DC converter will block the short-circuit current and will not supply short-circuit current to the AC grid.

[0077] Optionally, when the voltage U PCC When the fault ride-through strategy of the flexible DC converter is greater than the short-term blocking threshold, the fault ride-through current of the flexible DC converter is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the fault ride-through strategy, including:

[0078] When the flexible DC adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC is in phase with the PCC bus voltage, and the short-circuit current fed into the AC grid by the flexible DC is 0.

[0079] When the flexible DC transmission adopts a constant AC voltage fault ride-through strategy, the voltage U of the PCC bus is compared. PCC The AC voltage reference value U set in the fault ride-through strategy with constant AC voltage REF ,in:

[0080] When U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter.

[0081] When U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid

[0082] Optionally, when U PCC equal to UREF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. Among them, the short-circuit current of flexible DC feed into AC power grid is calculated. The formula is:

[0083]

[0084] In the formula, The output voltage of the flexible DC converter. Q is the short-circuit current fed into the AC grid by flexible DC. Conv This refers to the reactive power output of the flexible DC converter.

[0085] Optionally, the when U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid Among them, the determination of the short-circuit current of flexible DC feed into AC power grid The expression is:

[0086]

[0087] Among them, the maximum current carrying capacity of the flexible DC converter The calibration is performed based on the maximum operating current of the flexible DC converter.

[0088] In one embodiment, when U PCC If the voltage is 0.7 pu, which is greater than the short-time blocking voltage threshold of 0.2 pu, then the fault ride-through strategy adopted by the flexible DC converter needs to be read. When the flexible DC converter adopts a fault ride-through strategy controlled by constant AC voltage, a specific analysis should be conducted based on the relationship between the AC voltage reference value and the voltage at the flexible DC converter grid connection point.

[0089] Due to the AC voltage reference value U set in the fault ride-through strategy of flexible DC constant AC voltage control REF When it is 0.8 pu, therefore, U PCC Not equal to U REF Then it is necessary to calculate the maximum current carrying capacity of the flexible DC converter and the short-circuit current fed into the AC grid by the flexible DC converter after the fault ride-through strategy of constant AC voltage control is successfully implemented. To determine the short-circuit current value of the flexible DC feed into the AC grid when the fault ride-through strategy of the constant AC voltage control of the flexible DC fails to function. Based on the known conditions, in this embodiment, the maximum operating current of the 3000MW flexible DC converter is 3kA. Therefore, the maximum current carrying capacity of the 3000MW flexible DC converter is... The calculation formula is:

[0090]

[0091] According to the calculation formula for the short-circuit current of the flexible DC-to-AC grid after the successful implementation of the fault ride-through strategy controlled by constant AC voltage, we can know that:

[0092]

[0093] In the formula, the output voltage of the flexible DC converter The reactive power Q output by the flexible DC converter Conv =1860MVar, short-circuit current of flexible DC feed into AC power grid

[0094] Therefore, based on the failure of the fault ride-through strategy using constant AC voltage control for flexible DC transmission, the expression for the short-circuit current fed into the AC grid by the flexible DC transmission is determined. It can be seen that at this time, the short-circuit current of the flexible DC feed into the AC grid...

[0095] In summary, when a short-circuit fault occurs in the AC power grid, using the current short-circuit current simulation calculation method in the planning and design, regardless of the PCC bus voltage U... PCC Whether it exceeds the short-time blocking threshold of the flexible DC converter, the boosting effect of flexible DC on the short-circuit current of the AC grid is 3.6kA for the maximum current carrying capacity of the flexible DC converter; while using the short-circuit current calculation method proposed in this invention, when the AC system fault occurs, the PCC bus voltage U PCC When the short-term blocking threshold of the flexible DC converter is not greater than the threshold value, the flexible DC converter is blocked and does not provide short-circuit current to the AC grid. The effect of the flexible DC converter on increasing the short-circuit current of the AC system is zero. When the AC system fault occurs, the PCC bus voltage U PCC When the short-time blocking threshold of the flexible DC converter is greater than that of the flexible DC converter, and the fault ride-through strategy of the flexible DC is the active power priority fault ride-through strategy, the short-circuit current of the flexible DC fed into the AC grid is 0 because the short-circuit current of the flexible DC fed into the AC grid is in phase with the voltage of the PCC bus.

[0096] When the AC system fails, the PCC bus voltage U PCC When the short-circuit current exceeds the short-time blocking threshold of the flexible DC converter, and the fault ride-through strategy of the flexible DC converter is a constant AC voltage controlled fault ride-through strategy, according to the short-circuit current calculation method proposed in this invention, it is necessary to first compare the voltage U of the PCC bus. PCCThe AC voltage reference value U set in the fault ride-through strategy with constant AC voltage REF ,in:

[0097] When U PCC equal to U REF When using the short-circuit current calculation method proposed in this invention, the short-circuit current of the flexible DC-DC converter fed into the AC grid is calculated based on the output voltage and reactive power output of the flexible DC-DC converter. The current is 3.73A, while using the current short-circuit current simulation calculation method in the planning and design, the boost of the short-circuit current of the flexible DC to the AC grid is 3.6kA, which is the maximum current carrying capacity of the flexible DC converter.

[0098] When U PCC Not equal to U REF At that time, using the current short-circuit current simulation calculation method in planning and design, the boost of flexible DC to the AC grid short-circuit current is still 3.6kA, which is the maximum current carrying capacity of the flexible DC converter. However, using the short-circuit current calculation method proposed in this patent, it is necessary to calculate the maximum current carrying capacity of the flexible DC converter. and the short-circuit current The smaller value is used to determine the short-circuit current of the flexible DC feed into the AC grid.

[0099] Therefore, the current short-circuit current simulation calculation method used in planning and design is severely conservative in its calculation results because it does not consider the changing characteristics of the short-circuit current injected into the AC grid under various fault ride-through strategies. This is detrimental to the development of power system stability research. However, by adopting the short-circuit current calculation method proposed in this application, which considers different fault ride-through strategies of flexible DC, a more accurate impact of flexible DC on the short-circuit current of the AC grid can be obtained.

[0100] Exemplary device

[0101] Figure 2 A schematic diagram of the structure of a device for calculating the short-circuit current of a flexible DC-fed AC power grid according to a preferred embodiment of the present invention. Figure 2 As shown, the apparatus for calculating the short-circuit current of a flexible DC-fed AC grid described in this embodiment includes:

[0102] Bus voltage unit 201 is used to determine the voltage U of the PCC bus at the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault occurs in the AC power grid. PCC ;

[0103] Short-circuit current unit 202 is used to compare the voltage U PCC And the short-time blocking threshold of the flexible DC converter, wherein:

[0104] When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is not greater than the threshold value, the flexible DC converter is blocked and no short-circuit current is supplied to the AC grid. The short-circuit current fed into the AC grid by the flexible DC converter is 0.

[0105] When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is greater than the threshold, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC is calculated based on the flexible DC fault ride-through strategy.

[0106] Optionally, the bus voltage unit 201 determines the voltage U of the PCC bus at the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault occurs in the AC power grid. PCC include:

[0107] After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram.

[0108] The voltage of the PCC bus in the fault component network diagram and the voltage of the PCC bus in the normal component network diagram are linearly superimposed using the superposition method to obtain the voltage U of the PCC bus. PCC .

[0109] Optionally, the short-circuit current unit 202 is located at voltage U. PCC When the fault ride-through strategy of the flexible DC converter is greater than the short-term blocking threshold, the fault ride-through current of the flexible DC converter is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the fault ride-through strategy, including:

[0110] When the flexible DC adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC is in phase with the PCC bus voltage, and the short-circuit current fed into the AC grid by the flexible DC is 0.

[0111] When the flexible DC transmission adopts a constant AC voltage fault ride-through strategy, the voltage U of the PCC bus is compared. PCC The AC voltage reference value U set in the fault ride-through strategy with constant AC voltage REF ,in:

[0112] When U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter.

[0113] When U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid

[0114] Optionally, the short-circuit current unit 202 in U PCC equal to U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. Among them, the short-circuit current of flexible DC feed into AC power grid is calculated. The formula is:

[0115]

[0116] In the formula, The output voltage of the flexible DC converter. Q is the short-circuit current fed into the AC grid by flexible DC. Conv This refers to the reactive power output of the flexible DC converter.

[0117] Optionally, the short-circuit current unit 202 in U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter and the short-circuit current Determine the short-circuit current of flexible DC feed into AC power grid Among them, the determination of the short-circuit current of flexible DC feed into AC power grid The expression is:

[0118]

[0119] Among them, the maximum current carrying capacity of the flexible DC converter The calibration is performed based on the maximum operating current of the flexible DC converter.

[0120] Exemplary electronic devices

[0121] Figure 3 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. The electronic device may be any one or both of the first device and the second device, or a standalone device independent of them, which can communicate with the first device and the second device to receive the collected input signals from them. Figure 3 A block diagram of an electronic device according to an embodiment of the present disclosure is illustrated. For example... Figure 3 As shown, the electronic device includes one or more processors 31 and memory 32.

[0122] The processor 31 may be a central processing unit (CPU) or other form of processing unit with data processing and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0123] The memory 32 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 31 may execute the program instructions to implement the methods for information mining of historical change records and / or other desired functions of the software programs of the disclosed embodiments described above. In one example, the electronic device may also include an input device 33 and an output device 34, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0124] In addition, the input device 33 may also include, for example, a keyboard, a mouse, etc.

[0125] The output device 34 can output various information to the outside. The output device 64 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0126] Of course, for the sake of simplicity, Figure 3 Only some of the components of the electronic device relevant to this disclosure are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0127] Exemplary computer program products and computer-readable storage media

[0128] In addition to the methods and apparatus described above, embodiments of this disclosure may also be computer program products comprising computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods for calculating the short-circuit current of a flexible DC-fed AC grid according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0129] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this disclosure. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on a user's computing device, partially on a user's computing device, as a standalone software package, partially on a user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0130] Furthermore, embodiments of this disclosure may also be computer-readable storage media storing computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods for calculating the short-circuit current of a flexible DC-fed AC grid according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0131] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may, for example, include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0132] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0133] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0134] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0135] The methods and apparatus of this disclosure may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of this disclosure are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, this disclosure may also be implemented as a program recorded on a recording medium, the program including machine-readable instructions for implementing the methods according to this disclosure. Thus, this disclosure also covers recording media storing programs for performing the methods according to this disclosure.

[0136] It should also be noted that in the apparatus, devices, and methods of this disclosure, the components or steps are decomposable and / or recombinable. Such decomposition and / or recombination should be considered equivalent to the present disclosure. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0137] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for calculating the short-circuit current of a flexible DC-fed AC power grid, characterized in that, The method includes: The flexible DC grid connection point is determined based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC Bus voltage U PCC ; Compare the voltages U PCC And the short-time blocking threshold of the flexible DC converter, wherein: When the voltage U PCC When the short-circuit current fed into the AC grid by the flexible DC converter is not greater than the short-time blocking threshold of the flexible DC converter, the short-circuit current is determined to be 0. When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is exceeded, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the flexible DC fault ride-through strategy, including: When the flexible DC transmission adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC transmission is 0. When flexible DC transmission adopts a constant AC voltage fault ride-through strategy, comparison PCC Bus voltage U PCC The AC voltage reference value set in the fault ride-through strategy with constant AC voltage U REF ,in: when U PCC equal U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. İ ConvQ Among them, the short-circuit current of flexible DC feed into the AC power grid is calculated. İ ConvQ The formula is: In the formula, The output voltage of the flexible DC converter. İ ConvQ This refers to the short-circuit current fed into the AC power grid by flexible DC transmission. Q Conv The reactive power output of the flexible DC converter; when U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter İ Convmax and the short-circuit current İ ConvQ Determine the short-circuit current of flexible DC feed into AC power grid İ ConvF The determination of the short-circuit current of the flexible DC-to-AC grid is described above. İ ConvF The expression is: İ ConvF = min { İ Convmax ， İ ConvQ} Among them, the maximum current carrying capacity of the flexible DC converter İ Convmax The calibration is performed based on the maximum operating current of the flexible DC converter.

2. The method according to claim 1, characterized in that, The flexible DC grid connection point is determined based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC Bus voltage U PCC include: After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram. The fault component network diagram is composed of components obtained by superposition. PCC The voltage of the bus and the normal component network diagram PCC The voltages of the bus are linearly superimposed to obtain PCC Bus voltage U PCC .

3. A device for calculating the short-circuit current of a flexible DC-fed AC power grid, characterized in that, The device includes: The bus voltage unit is used to determine the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC Bus voltage U PCC ; Short-circuit current unit, used to compare the voltage U PCC And the short-time blocking threshold of the flexible DC converter, wherein: When the voltage U PCC When the short-circuit current fed into the AC grid by the flexible DC converter is not greater than the short-time blocking threshold of the flexible DC converter, the short-circuit current is determined to be 0. When the voltage U PCC When the short-term blocking threshold of the flexible DC converter is exceeded, the flexible DC fault ride-through strategy is read, and the short-circuit current fed into the AC grid by the flexible DC converter is calculated based on the flexible DC fault ride-through strategy, including: When the flexible DC transmission adopts the active power priority fault ride-through strategy, the short-circuit current fed into the AC grid by the flexible DC transmission is 0. When flexible DC transmission adopts a constant AC voltage fault ride-through strategy, comparison PCC Bus voltage U PCC The AC voltage reference value set in the fault ride-through strategy with constant AC voltage U REF ,in: when U PCC equal U REF At that time, the short-circuit current of the flexible DC power supply to the AC grid is calculated based on the output voltage and reactive power of the flexible DC converter. İ ConvQ Among them, the short-circuit current of flexible DC feed into the AC power grid is calculated. İ ConvQ The formula is: In the formula, The output voltage of the flexible DC converter. İ ConvQ This refers to the short-circuit current fed into the AC power grid by flexible DC transmission. Q Conv The reactive power output of the flexible DC converter; when U PCC Not equal to U REF At that time, based on the maximum current carrying capacity of the flexible DC converter İ Convmax and the short-circuit current İ ConvQ Determine the short-circuit current of flexible DC feed into AC power grid İ ConvF Among them, the determination of the short-circuit current of flexible DC feed into AC power grid İ ConvF The expression is: İ ConvF = min { İ Convmax ， İ ConvQ} Among them, the maximum current carrying capacity of the flexible DC converter İ Convmax The calibration is performed based on the maximum operating current of the flexible DC converter.

4. The apparatus according to claim 3, characterized in that, The bus voltage unit determines the flexible DC grid connection point based on the system network diagram generated after a short-circuit fault in the AC power grid. PCC Bus voltage U PCC include: After a short-circuit fault occurs in the AC power grid, a system network diagram is generated, which includes a fault component network diagram and a normal component network diagram. The fault component network diagram is composed of components obtained by superposition. PCC The voltage of the bus and the normal component network diagram PCC The voltages of the bus are linearly superimposed to obtain PCC Bus voltage U PCC .

5. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program for performing the method according to any one of claims 1 to 2.

6. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the method of any one of claims 1 to 2.

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