CN115864481A - Method and device for calculating short-circuit current fed into alternating current power grid by flexible direct current - Google Patents
Method and device for calculating short-circuit current fed into alternating current power grid by flexible direct current Download PDFInfo
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Abstract
The invention discloses a method and a device for calculating short-circuit current fed into an alternating current power grid by flexible direct current, wherein the method comprises the following steps: determining the voltage U of the PCC bus according to a system network diagram generated after the short-circuit fault occurs to the AC power grid PCC (ii) a Comparing the voltage U PCC And a flexible dc converter short latch-up threshold, wherein: when the voltage U is PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the flexible direct current is locked, short-circuit current is not provided for the alternating current power grid, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0; when the voltage U is PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy. The short-circuit current calculation result obtained by the method and the device is closer to the implementation operation value, and the flexible direct current feed-in alternating current is improvedThe accuracy of the short-circuit current calculation result of the power grid fully ensures the stability of the power system.
Description
Technical Field
The present invention relates to the field of high voltage power transmission technology, and more particularly, to a method and apparatus for calculating a short circuit current of a flexible dc feed ac grid, as well as a storage medium and an electronic device.
Background
The influence of flexible direct current on short-circuit current of an alternating current power grid is usually combined with specific flexible direct current engineering in the current planning design and engineering operation, and from the equipment characteristics of a flexible direct current converter, the converter is considered to inject current into the alternating current power grid according to the maximum current capacity of the converter during the alternating current fault period. The common method for calculating the auxiliary effect of the flexible direct current on the short-circuit current of the alternating current power grid is to actively read the maximum value parameter of the injected current of the flexible direct current converter, set a current source at the flexible direct current grid-connected point according to the maximum value of the injected current, and calculate the short-circuit current.
However, if the short-circuit current is calculated according to the above research method, the obtained short-circuit current result is seriously conservative, the port characteristic of the flexible direct current converter is excessively simplified, and the change characteristic of the current injected into the alternating current power grid by the flexible direct current under various fault ride-through strategies is not considered, that is, the active component and the reactive component of the current injected into the alternating current power grid by the flexible direct current are not influenced by the fault ride-through strategies, so that the deviation between the obtained short-circuit current calculation result and the actual operation value is large, and the development of the stability research of the power system is seriously influenced.
Therefore, a technology is needed, which can fully consider the change characteristics of the current of the flexible direct current injected into the alternating current power grid under various fault ride-through strategies, so as to improve the accuracy of calculating the short-circuit current fed into the alternating current power grid by the flexible direct current during the short-circuit fault of the alternating current power grid.
Disclosure of Invention
In order to solve the problems that in the prior art, when an alternating current power grid has a short-circuit fault, a maximum value parameter of an injection current of a flexible direct current converter is actively read, a current source is arranged at a flexible direct current grid-connected point according to the maximum value of the injection current, short-circuit current calculation is carried out, and the obtained short-circuit current result has large deviation with an actual operation value and influences the stability of a power system, the invention provides a method for calculating the short-circuit current fed into the alternating current power grid by flexible direct current, which comprises the following steps:
determining voltage U of PCC bus of flexible direct current grid-connected point according to system network diagram generated after short-circuit fault of alternating current power grid PCC ；
Comparing said voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the voltage U is PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy.
Further, the voltage U of the PCC bus of the flexible direct current grid-connected point is determined according to a system network diagram generated after the short-circuit fault occurs to the alternating current power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating-current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
Further, when the voltage U is applied PCC When the fault current is larger than the short-time blocking threshold value of the flexible direct current converter, reading the fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current comprises the following steps:
when the flexible direct current adopts an active priority fault ride-through strategy, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating current voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value U set in the fault ride-through strategy of the constant AC voltage REF Wherein:
when U is turned PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
When U is formed PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current
Determining a short-circuit current->
Further, when U is turned PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
Wherein a short-circuit current which is fed in the flexible DC voltage supply system is calculated>
The formula of (1) is as follows:
in the formula (I), the compound is shown in the specification,
is the output voltage of the flexible DC converter->
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
Further, when U is in PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current->
Determining a short-circuit current in a flexible DC-fed AC mains->
Wherein the determination of a short-circuit current in a flexible DC feed-in AC mains->
The expression of (a) is:
wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
According to another aspect of the invention, the invention provides a device for calculating a short-circuit current of a flexible direct current fed into an alternating current grid, the device comprising:
a bus voltage unit for determining the voltage U of the PCC bus of the flexible DC grid-connected point according to a system network diagram generated after the short-circuit fault occurs to the AC power grid PCC ；
A short-circuit current unit for comparing the voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the voltage U is higher PCC When the voltage is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating according to the flexible direct current fault ride-through strategyThe short-circuit current fed into the AC power grid is calculated as flexible direct current.
Further, the bus voltage unit determines the voltage U of the PCC bus of the flexible direct current grid-connected point according to a system network diagram generated after the short-circuit fault occurs to the alternating current power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
Further, the short-circuit current unit is at the voltage U PCC When the fault current is larger than the short-time blocking threshold value of the flexible direct current converter, reading the fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current comprises the following steps:
when the flexible direct current adopts an active power-priority fault ride-through strategy, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating current voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value U set in the fault ride-through strategy of the constant AC voltage REF Wherein:
when U is turned PCC Is equal to U REF In the process, the short-circuit current fed into the alternating current power grid by the flexible direct current converter is calculated according to the output voltage of the flexible direct current converter and the reactive power output by the flexible direct current converter
When U is turned PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current
Determining a short-circuit current->
Further, the short-circuit current unit is in U PCC Is equal to U REF In the process, the short-circuit current fed into the alternating current power grid by the flexible direct current converter is calculated according to the output voltage of the flexible direct current converter and the reactive power output by the flexible direct current converter
Wherein a short-circuit current ^ of the flexible direct current fed into the alternating current grid is calculated>
The formula of (1) is:
in the formula (I), the compound is shown in the specification,
is the output voltage of the flexible DC converter->
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
Further, the short-circuit current unit is in U PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And said short-circuit current>
Determining a short-circuit current->
Wherein the determination of the short-circuit current ≥ in a flexible direct-current feed-in alternating-current network>
The expression of (a) is:
wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
According to a further aspect of the invention, a computer-readable storage medium is provided, which stores a computer program for executing any of the methods of calculating a short-circuit current of a flexible direct-current fed ac power grid according to the invention.
According to another aspect of the present invention, the present invention provides an electronic apparatus comprising:
a processor;
a memory for storing the processor-executable instructions;
the processor is used for reading the executable instructions from the memory and executing the executable instructions to realize any one of the methods for calculating the short-circuit current of the flexible direct current fed into the alternating current power grid.
The technical scheme of the invention provides a method and a device for calculating the short-circuit current of a flexible direct-current feed-in alternating-current power grid, a storage medium and electronic equipment, wherein the method for calculating the short-circuit current of the flexible direct-current feed-in alternating-current power grid comprises the following steps: determining voltage U of PCC bus of flexible direct current grid-connected point according to system network diagram generated after short-circuit fault of alternating current power grid PCC (ii) a Comparing said voltage U PCC And a short-time latch-up threshold of the flexible dc converter,wherein: when the voltage U is higher PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the flexible direct current is locked, short-circuit current is not provided for the alternating current power grid, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0; when the voltage U is higher PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy. According to the method and the device, when the short-circuit fault occurs in the alternating current power grid, the short-circuit current fed into the alternating current power grid by the flexible direct current under different fault ride-through strategies is calculated, so that the short-circuit current calculation result is closer to the operation value, the accuracy of the short-circuit current calculation result fed into the alternating current power grid by the flexible direct current is improved, and the stability of a power system is fully ensured.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a flow chart of a method of calculating a short circuit current of a flexible direct current fed into an alternating current grid according to a preferred embodiment of the present invention;
FIG. 2 is a schematic block diagram of a system for calculating the short circuit current of a flexible DC feed AC grid in accordance with a preferred embodiment of the present invention;
fig. 3 is a schematic structural diagram of an electronic device according to a preferred embodiment of the present invention.
Detailed Description
Hereinafter, example embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a subset of embodiments of the invention and not all embodiments of the invention, with the understanding that the invention is not limited to the example embodiments described herein.
It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
It will be understood by those of skill in the art that the terms "first," "second," and the like in the embodiments of the present invention are used merely to distinguish one element, step, device, module, or the like from another element, and do not denote any particular technical or logical order therebetween.
It should also be understood that in embodiments of the present invention, "a plurality" may refer to two or more and "at least one" may refer to one, two or more.
It should also be understood that any reference to any component, data, or structure in an embodiment of the invention may be generally understood as one or more, unless explicitly stated otherwise or indicated otherwise herein.
In addition, the term "and/or" in the present invention is only one kind of association relationship describing the associated object, and means that there may be three kinds of relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In the present invention, the character "/" generally indicates that the preceding and following related objects are in an "or" relationship.
It should also be understood that the description of the embodiments of the present invention emphasizes the differences between the embodiments, and the same or similar parts may be referred to each other, and are not repeated herein for brevity.
Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
Embodiments of the invention are operational with numerous other general purpose or special purpose computing system environments or configurations, and with numerous other electronic devices, such as terminal devices, computer systems, servers, etc. Examples of well known terminal devices, computing systems, environments, and/or configurations that may be suitable for use with electronic devices, such as terminal devices, computer systems, servers, and the like, include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, networked personal computers, minicomputer systems, mainframe computer systems, distributed cloud computing environments that include any of the above, and the like.
Electronic devices such as terminal devices, computer systems, servers, etc. may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, etc. that perform particular tasks or implement particular abstract data types. The computer system/server may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices.
Exemplary method
Fig. 1 is a flow chart of a method of calculating a short circuit current of a flexible direct current fed into an alternating current grid according to a preferred embodiment of the invention. As shown in fig. 1, the method for calculating a short-circuit current of a flexible dc-fed ac power grid according to this embodiment includes the following steps:
Optionally, the voltage U of the PCC bus of the flexible dc grid-connected point is determined according to a system network diagram generated after the short-circuit fault occurs to the ac power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
In an embodiment, the maximum power of the flexible dc converter for flexible dc is 3000MW, the maximum working current of the 3000MW flexible dc converter is 3kA, when the maximum current value of the 3000MW flexible dc converter is calibrated, the set calibration coefficient is 1.2, and the short-time blocking threshold of the flexible dc converter is 0.2p.u. When the fault ride-through strategy controlled by the constant alternating voltage is adopted, the reference value of the alternating voltage is set to be U REF =0.8p.u., after the short-circuit fault of the alternating current power grid occurs, obtaining the voltage U of the PCC bus after the fault by drawing a system network diagram PCC ＝0.7p.u.。
102, comparing the voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is higher PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the flexible direct current is locked, short-circuit current is not provided for the alternating current power grid, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the voltage U is higher PCC And when the fault current is greater than the short-time locking threshold of the flexible direct current converter, reading a fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current.
In one embodiment, when U PCC When the short-time locking threshold value of the flexible direct current converter is smaller than 0.2p.u, the flexible direct current is locked, and short-circuit current is not provided for an alternating current power grid.
Optionally, when the voltage U is PCC When the fault current is larger than the short-time locking threshold of the flexible direct current converter, reading a fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current comprises the following steps:
when the flexible direct current adopts an active power priority fault ride-through strategy, the phase of the short-circuit current fed into the alternating current power grid by the flexible direct current is the same as that of the PCC bus voltage, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value U set in the fault ride-through strategy of the constant AC voltage REF Wherein:
when U is turned PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
When U is turned PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current
Determining a short-circuit current in a flexible DC-fed AC mains->
Alternatively, when U PCC Is equal to U REF In the process, the short-circuit current fed into the alternating current power grid by the flexible direct current converter is calculated according to the output voltage of the flexible direct current converter and the reactive power output by the flexible direct current converter
Wherein a short-circuit current which is fed in the flexible DC voltage supply system is calculated>
The formula of (1) is:
in the formula (I), the compound is shown in the specification,
is the output voltage of the flexible DC converter->
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
Optionally, the current U is PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And said short-circuit current>
Determining a short-circuit current in a flexible DC-fed AC mains->
Wherein the determination of the short-circuit current ≥ in a flexible direct-current feed-in alternating-current network>
The expression of (a) is:
wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
In one embodiment, when U PCC If the value is not less than 0.7p.u., and the value is greater than the short-time blocking voltage threshold value of 0.2p.u., the value adopted by the flexible direct current converter needs to be readAnd (4) fault ride-through strategy. And when the flexible direct current adopts a fault ride-through strategy of constant alternating voltage control, the relation between the alternating voltage reference value and the voltage of the flexible direct current grid-connected point is combined for specific analysis.
AC voltage reference value U set in fault ride-through strategy for constant AC voltage control due to flexible DC REF 0.8p.u. is, therefore, U PCC Is not equal to U REF Then, the maximum current value of the flexible dc converter and the short-circuit current value fed into the ac power grid by the flexible dc converter after the fault ride-through strategy assuming that the flexible dc converter successfully implements the fixed ac voltage control are calculated respectively
Short-circuit current value (or value) fed into an alternating current power grid by flexible direct current when a fault ride-through strategy for determining the constant alternating voltage control of the flexible direct current cannot work>
According to known conditions, in the embodiment, the maximum working current of the 3000MW flexible direct current converter is 3kA, and the maximum current capacity &ofthe 3000MW flexible direct current converter is greater than or equal to>
The calculation formula of (2) is as follows:
and the calculation formula for calculating the short-circuit current fed into the alternating current power grid by the flexible direct current after the fault ride-through strategy of the constant alternating voltage control is successfully implemented can be known as follows:
in the form of output voltage of a flexible DC converter
Reactive power Q output by flexible DC converter Conv =1860MVar, short-circuit current in flexible DC feed AC grid &>
Therefore, when the fault ride-through strategy of adopting constant alternating voltage control according to the flexible direct current is unsuccessful, determining the expression of the short-circuit current fed into the alternating current power grid by the flexible direct current
It can be seen that, at this time, the short-circuit current fed into the ac power grid in a flexible dc manner->
In summary, after the short-circuit fault occurs in the ac power grid, the short-circuit current simulation calculation method in the current planning design is adopted, so that no matter the PCC bus voltage U is PCC If the current is larger than the short-time blocking threshold of the flexible direct current converter, the boosting effect of the flexible direct current on the short-circuit current of the alternating current power grid is that the maximum current capacity of the flexible direct current converter is 3.6kA; by adopting the short-circuit current calculation method provided by the invention, the PCC bus voltage U is obtained after the AC system fails PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the flexible direct current is locked, short-circuit current is not provided for an alternating current power grid, and the short-circuit current boosting effect of the flexible direct current on an alternating current system is 0; PCC bus voltage U after AC system failure PCC And when the fault ride-through strategy is larger than the short-time blocking threshold value of the flexible direct current converter and the read fault ride-through strategy of the flexible direct current is an active-priority fault ride-through strategy, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0 because the phase of the short-circuit current fed into the alternating current power grid by the flexible direct current is the same as that of the PCC bus voltage.
PCC bus voltage U after AC system failure PCC When the fault ride-through strategy is larger than the short-time blocking threshold value of the flexible direct current converter and the read fault ride-through strategy of the flexible direct current is the fault ride-through strategy controlled by the fixed alternating current voltage, the short-circuit current calculation method provided by the invention needs to compare the PCC buses firstlyVoltage U PCC And the AC voltage reference value U set in the fault ride-through strategy of the fixed AC voltage REF Wherein:
when U is turned PCC Is equal to U REF Then, the short-circuit current calculation method provided by the invention is adopted to calculate the short-circuit current fed into the alternating current power grid by the flexible direct current according to the output voltage of the flexible direct current converter and the reactive power output by the flexible direct current converter
The current value is equal to 3.73A, and the short-circuit current simulation calculation method in the current planning design is adopted, so that the auxiliary increase of the short-circuit current of the flexible direct current to the alternating current power grid is 3.6kA of the maximum current capacity of the flexible direct current converter; />
When U is turned PCC Is not equal to U REF In the process, a short-circuit current simulation calculation method in the current planning design is adopted, and the auxiliary increase of the short-circuit current of the flexible direct current to the alternating current power grid is still 3.6kA of the maximum current capacity of the flexible direct current converter; by adopting the short-circuit current calculation method provided by the patent, the maximum through current value of the flexible direct current converter needs to be calculated
And said short-circuit current>
Determining short-circuit current (or voltage) in flexible DC feed-in AC power grid based on smaller value>
Therefore, by adopting the short-circuit current simulation calculation method in the current planning design, the change characteristic of the short-circuit current injected into the alternating current power grid by the flexible direct current under various fault ride-through strategies is not considered, the calculation result of the short-circuit current fed into the alternating current power grid by the flexible direct current is seriously conservative, and the development of the stability research of a power system is not facilitated. By adopting the short-circuit current calculation method provided by the application and considering different fault ride-through strategies of the flexible direct current, more accurate influence of the flexible direct current on the short-circuit current of the alternating current power grid can be obtained.
Exemplary devices
Fig. 2 is a schematic structural diagram of an apparatus for calculating a short-circuit current of a flexible dc feed ac grid according to a preferred embodiment of the present invention. As shown in fig. 2, the apparatus for calculating a short-circuit current of a flexible dc-fed ac power grid according to this embodiment includes:
a bus voltage unit 201, configured to determine a voltage U of the PCC bus in the flexible dc grid-connected point according to a system network diagram generated after a short-circuit fault occurs in the ac power grid PCC ；
A short-circuit current unit 202 for comparing the voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is PCC When the short-time locking threshold value of the flexible direct current converter is not greater than the short-time locking threshold value, the flexible direct current is locked, short-circuit current is not provided for the alternating current power grid, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the voltage U is PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy.
Optionally, the bus voltage unit 201 determines the voltage U of the PCC bus of the flexible dc grid-connected point according to a system network diagram generated after the short-circuit fault occurs in the ac power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating-current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
Optionally, the short-circuit current unit 202 is at said voltage U PCC When the fault voltage is larger than the short-time locking threshold value of the flexible direct current converter, reading the fault ride-through strategy of the flexible direct current, and calculating the short time of feeding the flexible direct current into the alternating current power grid according to the fault ride-through strategy of the flexible direct currentThe path current comprises:
when the flexible direct current adopts an active power priority fault ride-through strategy, the phase of the short-circuit current fed into the alternating current power grid by the flexible direct current is the same as that of the PCC bus voltage, and the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating current voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value U set in the fault ride-through strategy of the constant AC voltage REF Wherein:
when U is turned PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
When U is turned PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current
Determining a short-circuit current->
Optionally, the short circuit current unit 202 is in U PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
Wherein a short-circuit current ^ of the flexible direct current fed into the alternating current grid is calculated>
The formula of (1) is:
in the formula (I), the compound is shown in the specification,
is the output voltage of the flexible DC converter->
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
Optionally, the short circuit current unit 202 is in U PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current->
Determining a short-circuit current->
Wherein the determination of the short-circuit current ≥ in a flexible direct-current feed-in alternating-current network>
The expression of (c) is:
wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
Exemplary electronic device
Fig. 3 is a schematic configuration diagram of an electronic device according to a preferred embodiment of the present invention. The electronic device may be either or both of the first device and the second device, or a stand-alone device separate from them, which stand-alone device may communicate with the first device and the second device to receive the acquired input signals therefrom. Fig. 3 illustrates a block diagram of an electronic device in accordance with an embodiment of the disclosure. As shown in fig. 3, the electronic device includes one or more processors 31 and a memory 32.
The processor 31 may be a Central Processing Unit (CPU) or other form of processing unit having data processing capabilities and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.
The input device 33 may also include, for example, a keyboard, a mouse, and the like.
The output device 34 can output various information to the outside. The output devices 64 may include, for example, a display, speakers, printer, and the like, as well as a communication network and remote output devices connected thereto.
Of course, for simplicity, only some of the components of the electronic device relevant to the present disclosure are shown in fig. 3, omitting components such as buses, input/output interfaces, and the like. In addition, the electronic device may include any other suitable components, depending on the particular application.
Exemplary computer program product and computer-readable storage Medium
In addition to the above-described methods and devices, embodiments of the present disclosure may also be a computer program product comprising computer program instructions which, when executed by a processor, cause the processor to perform the steps in the method of calculating a short-circuit current of a flexible direct current fed alternating current grid according to various embodiments of the present disclosure described in the above-mentioned "exemplary methods" section of this specification.
The computer program product may write program code for carrying out operations for embodiments of the present disclosure in any combination of one or more programming languages, including an object oriented programming language such as Java, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device and partly on a remote computing device, or entirely on the remote computing device or server.
Furthermore, embodiments of the present disclosure may also be a computer readable storage medium having stored thereon computer program instructions which, when executed by a processor, cause the processor to perform the steps in the method of calculating a short-circuit current of a flexible direct current fed ac power grid according to various embodiments of the present disclosure described in the "exemplary methods" section above in this description.
The computer-readable storage medium may take any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may include, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection having one or more wires, a portable disk, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The foregoing describes the general principles of the present disclosure in conjunction with specific embodiments, however, it is noted that the advantages, effects, etc. mentioned in the present disclosure are merely examples and are not limiting, and they should not be considered essential to the various embodiments of the present disclosure. Furthermore, the foregoing disclosure of specific details is for the purpose of illustration and description and is not intended to be limiting, since the disclosure will be described in detail with reference to specific details.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts in the embodiments are referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The block diagrams of devices, apparatuses, systems referred to in this disclosure are only given as illustrative examples and are not intended to require or imply that the connections, arrangements, configurations, etc. must be made in the manner shown in the block diagrams. These devices, apparatuses, devices, systems may be connected, arranged, configured in any manner, as will be appreciated by those skilled in the art. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including, but not limited to," and are used interchangeably therewith. As used herein, the words "or" and "refer to, and are used interchangeably with, the word" and/or, "unless the context clearly dictates otherwise. The word "such as" is used herein to mean, and is used interchangeably with, the phrase "such as but not limited to".
The method and apparatus of the present disclosure may be implemented in a number of ways. For example, the methods and apparatus of the present disclosure may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order for the steps of the method is for illustration only, and the steps of the method of the present disclosure are not limited to the order specifically described above unless specifically stated otherwise. Further, in some embodiments, the present disclosure may also be embodied as programs recorded in a recording medium, the programs including machine-readable instructions for implementing the methods according to the present disclosure. Thus, the present disclosure also covers a recording medium storing a program for executing the method according to the present disclosure.
It is also noted that in the devices, apparatuses, and methods of the present disclosure, each component or step can be decomposed and/or recombined. These decompositions and/or recombinations are to be considered equivalents of the present disclosure. The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit embodiments of the disclosure to the form disclosed herein. While a number of example aspects and embodiments have been discussed above, those of skill in the art will recognize certain variations, modifications, alterations, additions and sub-combinations thereof.
Claims (12)
1. A method of calculating a short circuit current of a flexible dc feed ac grid, the method comprising:
determining voltage U of PCC bus of flexible direct current grid-connected point according to system network diagram generated after short-circuit fault of alternating current power grid PCC ；
Comparing said voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is PCC When the short-time blocking threshold value of the flexible direct current converter is not greater than the short-time blocking threshold value, the short-circuit current fed into the alternating current power grid by the flexible direct current is determined to be 0;
when the voltage U is higher PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy.
2. The method according to claim 1, wherein the voltage U of the PCC bus of the flexible DC grid-connected point is determined according to a system network diagram generated after the short-circuit fault occurs in the AC power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating-current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
3. The method of claim 1, wherein the voltage is U when PCC When the fault current is larger than the short-time blocking threshold value of the flexible direct current converter, reading the fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current comprises the following steps:
when the flexible direct current adopts an active power-priority fault ride-through strategy, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value U set in the fault ride-through strategy of the constant AC voltage REF Wherein:
when U is turned PCC Is equal to U REF According to the output of the flexible DC converterCalculating short-circuit current of flexible direct current fed-in alternating current power grid by voltage and reactive power output by flexible direct current converter
When U is turned PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current->
Determining a short-circuit current in a flexible DC-fed AC mains->
4. The method of claim 3, wherein when U is detected PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
Wherein a short-circuit current which is fed in the flexible DC voltage supply system is calculated>
The formula of (1) is as follows:
in the formula (I), the compound is shown in the specification,
is the output voltage of the flexible DC converter->
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
5. The method of claim 3, wherein the current U is PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And said short-circuit current>
Determining short-circuit current of flexible DC-fed AC grid
Wherein the determination of the short-circuit current ≥ in a flexible direct-current feed-in alternating-current network>
The expression of (a) is: />
Wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
6. An apparatus for calculating a short circuit current for a flexible dc feed ac grid, the apparatus comprising:
a bus voltage unit for generating a system network diagram according to the short-circuit fault of the AC power gridDetermining voltage U of PCC bus of flexible direct current grid-connected point PCC ；
A short-circuit current unit for comparing the voltage U PCC And a flexible dc converter short latch-up threshold, wherein:
when the voltage U is PCC When the short-time blocking threshold value of the flexible direct current converter is not greater than the short-time blocking threshold value, the short-circuit current fed into the alternating current power grid by the flexible direct current is determined to be 0;
when the voltage U is PCC And when the fault current is larger than the short-time locking threshold value of the flexible direct current converter, reading the flexible direct current fault ride-through strategy, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the flexible direct current fault ride-through strategy.
7. The device according to claim 6, wherein the bus voltage unit determines the voltage U of the PCC bus of the flexible DC grid-connected point according to a system network diagram generated after the short-circuit fault occurs to the AC power grid PCC The method comprises the following steps:
generating a system network diagram after the short-circuit fault occurs in the alternating-current power grid, wherein the system network diagram comprises a fault component network diagram and a normal component network diagram;
linearly superposing 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 by adopting a superposition method to obtain a voltage U of the PCC bus PCC 。
8. The apparatus of claim 6, wherein the short circuit current unit is at the voltage U PCC When the fault current is larger than the short-time locking threshold of the flexible direct current converter, reading a fault ride-through strategy of the flexible direct current, and calculating the short-circuit current fed into the alternating current power grid by the flexible direct current according to the fault ride-through strategy of the flexible direct current comprises the following steps:
when the flexible direct current adopts an active priority fault ride-through strategy, the short-circuit current fed into the alternating current power grid by the flexible direct current is 0;
when the flexible direct current adopts a fault ride-through strategy of constant alternating current voltage, comparing the voltage U of the PCC bus PCC And the AC voltage reference value set in the fault ride-through strategy of the fixed AC voltageU REF Wherein:
when U is formed PCC Is equal to U REF In the process, the short-circuit current fed into the alternating current power grid by the flexible direct current converter is calculated according to the output voltage of the flexible direct current converter and the reactive power output by the flexible direct current converter
When U is formed PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And the short-circuit current->
Determining a short-circuit current in a flexible DC-fed AC mains->
9. The apparatus of claim 8, wherein the short circuit current unit is in U PCC Is equal to U REF Calculating the short-circuit current fed into the AC power grid by the flexible DC converter according to the output voltage of the flexible DC converter and the reactive power output by the flexible DC converter
Wherein a short-circuit current ^ of the flexible direct current fed into the alternating current grid is calculated>
The formula of (1) is:
in the formula (I), the compound is shown in the specification,
is the output voltage of a flexible DC converter>
Short-circuit current, Q, for feeding flexible DC into an AC network Conv The reactive power output by the flexible direct current converter.
10. The apparatus of claim 8, wherein the short circuit current unit is in U PCC Is not equal to U REF According to the maximum current value of the flexible DC converter
And said short-circuit current>
Determining a short-circuit current->
Wherein the determination of the short-circuit current ≥ in a flexible direct-current feed-in alternating-current network>
The expression of (c) is:
wherein, the maximum current value of the flexible DC converter
And calibrating according to the maximum working current of the flexible direct current converter.
11. A computer-readable storage medium, characterized in that it stores a computer program for performing the method of any of the preceding claims 1 to 5.
12. An electronic device, characterized in that the electronic device comprises:
a processor;
a memory for storing the processor-executable instructions;
the processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the method described in any one of the above 1 to 5.
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