CN116593822A - Method and device for acquiring reference current of grid-connected converter - Google Patents
Method and device for acquiring reference current of grid-connected converter Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
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Abstract
The application discloses a method and a device for acquiring reference current of a grid following type converter suitable for grid fault conditions. The reference current acquisition method of the grid-connected converter comprises the following steps: acquiring voltage drop acting on virtual impedance of the converter after the power grid fault; obtaining a model value of the virtual impedance; acquiring the phase angle of the updated virtual impedance; and obtaining the reference current of the converter according to the voltage drop acting on the virtual impedance after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance. The method for acquiring the reference current of the grid-connected converter can enable the grid-connected converter to have the capability of adaptively processing different types of faults. For example, when a three-phase short circuit fault occurs in the power grid, the converter automatically outputs three-phase symmetrical currents to support the voltages of all phases in an equalizing mode. When the power grid has an asymmetric fault, the fault phase current output by the converter is larger than the non-fault phase, so that a better voltage supporting effect is achieved on the fault phase.
Description
Technical Field
The application relates to the technical field of converter control, in particular to a reference current acquisition method of a grid-connected converter and a reference current acquisition device of the grid-connected converter.
Background
When the voltage drops due to power grid faults, grid-connected specifications generally require a low-voltage ride through function with a grid-connected converter. When the voltage of the grid-connected point is in a given voltage contour line and above, the grid-connected converter can keep continuous operation. Obviously, outputting larger fault current is helpful to improve the voltage of the grid-connected point of the grid-connected converter. However, the current capacity of the grid-connected converter is limited and is usually not more than 2 times the rated current. Therefore, how to design a reasonable follow-up grid type converter fault control strategy and obtain an optimal voltage supporting effect in a safe current range is a problem to be solved. The essence of this problem is how to reasonably distribute the current components (positive-sequence active/reactive, negative-sequence active/reactive) of the converter in a limited space.
In a high-voltage power grid, line impedance is mainly inductance, and grid-connected specifications generally require that reactive current is preferentially output by a grid-connected converter so as to obtain a good voltage supporting effect. In a more general case, the active/reactive current ratio of the output of the converter is equal to the resistance/reactance ratio of the line impedance, so that the theoretically optimal voltage supporting effect can be obtained. The above is the main two kinds of current with net formula converter fault voltage support strategies, mainly has two aspects of problems: 1) Focusing on active/reactive current proportion distribution, and not giving a positive sequence/negative sequence current proportion distribution method; 2) The active/reactive current distribution adopts a fixed proportion, and cannot be adaptively adjusted along with the change of fault scenes.
It is therefore desirable to have a solution that overcomes or at least alleviates at least one of the above-mentioned drawbacks of the prior art.
Disclosure of Invention
It is an object of the present application to provide a method of obtaining a reference current for a grid-connected converter that overcomes or at least alleviates at least one of the above-mentioned drawbacks of the prior art.
In one aspect of the present application, a method for obtaining a reference current of a grid-connected converter is provided, which is used for a grid fault condition, and the method for obtaining the reference current of the grid-connected converter includes:
acquiring voltage drop acting on virtual impedance of the converter after the power grid fault;
obtaining a model value of the virtual impedance;
acquiring the phase angle of the updated virtual impedance;
and obtaining the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
Optionally, the acquiring the voltage drop acting on the virtual impedance of the converter after the grid fault includes:
acquiring three-phase voltage of a grid-connected point of the converter before a power grid fault;
acquiring three-phase voltage of a grid-connected point of the converter after the power grid fails;
and obtaining voltage drops acting on virtual impedance of the converter after the power grid fault according to the three-phase voltage of the grid connection point of the converter before the power grid fault and after the power grid fault.
Optionally, the obtaining the modulus of the virtual impedance includes:
acquiring the largest voltage drop of each phase of the virtual impedance as the largest voltage drop of each phase of the virtual impedance;
obtaining a maximum current allowable value of the converter;
and obtaining the modulus value of the virtual impedance according to the maximum value of the voltage drops of each phase of the virtual impedance and the maximum current allowable value of the converter.
Optionally, the obtaining the phase angle of the updated virtual impedance includes:
acquiring a phase angle of virtual impedance of an initial period;
acquiring a sequence number of a current power frequency period, and acquiring the minimum value of the amplitude values of the three-phase voltages of the grid-connected points of the current transformer in the k-1 power frequency period if the sequence number of the current power frequency period is larger than 3;
obtaining the minimum value in the amplitude values of three-phase voltages of the grid-connected points of the current transformer in the k-2 power frequency period;
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if yes, then
And acquiring the phase angle of the updated virtual impedance by adopting a first method.
Optionally, the obtaining the phase angle of the updated virtual impedance further includes:
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if not, then
And acquiring the phase angle of the updated virtual impedance by adopting a second method.
Optionally, the obtaining the phase angle of the updated virtual impedance further includes:
acquiring the sequence number of the current power frequency period, and if the sequence number of the current power frequency period is equal to 2
The phase angle of the updated virtual impedance is the phase angle + the disturbance step of the virtual impedance of the initial period or the phase angle of the updated virtual impedance is the phase angle-the disturbance step of the virtual impedance of the initial period.
Optionally, the first method is:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle, sgn, of the virtual impedance for k-2 power frequency cycles represents a sign function.
Optionally, the second method is:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle, sgn, of the virtual impedance for k-2 power frequency cycles represents a sign function.
Optionally, the determining whether the minimum value in the amplitude of the three-phase voltage of the grid-connected point of the current transformer in the kth-1 power frequency period and the minimum value in the amplitude of the three-phase voltage of the grid-connected point of the current transformer in the kth-2 power frequency period meet the preset condition includes:
judgment U min [k-1]≥U min [k-2]Whether the preset condition is met or not is judged if yes; wherein,
k is the kth power frequency period, U min [k-1]Is the minimum value, U, in the amplitude of three-phase voltage of the grid-connected point of the converter in the k-1 power frequency period min [k-2]The minimum value of the amplitude values of the three-phase voltages of the grid-connected point of the converter in the k-2 power frequency period is obtained.
Optionally, the reference current of the converter is obtained according to the voltage drop acting on the virtual impedance of the converter after the grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance, and the following formula is adopted:
wherein ,
three-phase reference current representing a current transformer, +.>Is the three-phase voltage of the grid-connected point of the converter before the power grid fault,is the three-phase voltage of the grid-connected point of the converter after the power grid fault.
The application also provides a reference current acquisition device of the grid-connected converter, which comprises:
the voltage drop acquisition module is used for acquiring the voltage drop acting on the virtual impedance of the converter after the power grid fault;
the virtual impedance module is used for acquiring the virtual impedance module;
the updating module is used for acquiring the phase angle of the updated virtual impedance;
the reference current acquisition module is used for acquiring the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
The beneficial effects are that:
the reference current acquisition method of the grid-connected converter has the following advantages:
1. the network-following converter can be provided with the capability of adaptively processing different types of faults. For example, when a three-phase short circuit fault occurs in the power grid, the converter automatically outputs three-phase symmetrical currents to support the voltages of all phases in an equalizing mode. When the power grid has an asymmetric fault, the fault phase current output by the converter is larger than the non-fault phase, so that a better voltage supporting effect is achieved on the fault phase.
2. The application can ensure that the follow-up network type converter is in a safe operation range, and can search and stabilize at the optimal working point of the fault phase voltage support at a higher speed under different fault scenes.
Drawings
Fig. 1 is a flow chart of a reference current obtaining method of a grid-connected converter according to an embodiment of the application.
Fig. 2 is an electronic device for implementing the reference current acquisition method of the heel-net converter shown in fig. 1.
Fig. 3 is a schematic structural diagram of a control system for a heel-net type converter according to an embodiment of the present application.
Fig. 4 is a schematic structural diagram of a grid-connected converter connected to a power grid according to an embodiment of the present application.
Figure 5 is a schematic diagram of the regulation process of the virtual impedance phase angle of the current transformer.
Fig. 6 is a schematic diagram of a virtual impedance mode adjustment process for a current transformer.
Fig. 7 is a schematic diagram of the maximum value of the amplitude of the current of the three phases of the output of the converter.
Figure 8 is a schematic diagram of the minimum value of the three-phase voltage amplitude of the grid-tie point of the current transformer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application become more apparent, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of the application. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
It should be noted that in the description of the present application, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Fig. 1 is a flow chart of a reference current obtaining method of a grid-connected converter according to an embodiment of the application.
The method for regulating and controlling the reference voltage of the networking converter shown in fig. 1 is used for a power grid fault condition, and the method for acquiring the reference current of the following-network converter comprises the following steps:
step 1: acquiring voltage drop acting on virtual impedance of the converter after the power grid fault;
step 2: obtaining a model value of the virtual impedance;
step 3: acquiring the phase angle of the updated virtual impedance;
step 4: and obtaining the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
The reference current acquisition method of the grid-connected converter has the following advantages:
1. the network-following converter can be provided with the capability of adaptively processing different types of faults. For example, when a three-phase short circuit fault occurs in the power grid, the converter automatically outputs three-phase symmetrical currents to support the voltages of all phases in an equalizing mode. When the power grid has an asymmetric fault, the fault phase current output by the converter is larger than the non-fault phase, so that a better voltage supporting effect is achieved on the fault phase.
2. The application can ensure that the follow-up network type converter is in a safe operation range, and can search and stabilize at the optimal working point of the fault phase voltage support at a higher speed under different fault scenes.
In this embodiment, the step of obtaining the voltage drop acting on the virtual impedance of the converter after the grid fault includes:
acquiring three-phase voltage of a grid-connected point of the converter before a power grid fault;
acquiring three-phase voltage of a grid-connected point of the converter after the power grid fails;
and acquiring voltage drop acting on virtual impedance after the grid-connected point fault of the converter according to the three-phase voltage of the grid-connected point of the converter before the grid fault and the three-phase voltage of the grid-connected point of the converter after the grid fault.
For example, the processing steps may be performed,three-phase voltage of grid-connected point of converter before grid fault>And representing the three-phase voltage of the grid connection point of the converter after the grid fault. />Is the voltage drop acting on the virtual impedance.
In this embodiment, obtaining the modulus of the virtual impedance includes:
acquiring the largest voltage drop of each phase of the virtual impedance as the largest voltage drop of each phase of the virtual impedance;
obtaining a maximum current allowable value of the converter;
and obtaining the modulus value of the virtual impedance according to the maximum voltage drop value of each phase of the virtual impedance and the maximum current allowable value of the current transformer.
For example, the magnitude of the voltage drop of each phase of the virtual impedance is calculated first, and the maximum value (maximum value of the voltage drop of each phase of the virtual impedance) is recorded as DeltaU max ；
I lim Represents the maximum current allowed value of the current transformer, which can be obtained by means of the prior art and is not described in detail here.
And obtaining a module value of the virtual impedance according to the maximum voltage drop value of each phase of the virtual impedance and the maximum current allowable value of the converter, and specifically, obtaining the module value by adopting the following formula:
wherein ,|ZS And I is the modulus of the virtual impedance.
In this embodiment, acquiring the phase angle of the updated virtual impedance includes:
acquiring a phase angle of virtual impedance of an initial period;
acquiring a sequence number of a current power frequency period, and acquiring the minimum value of the amplitude values of the three-phase voltages of the grid-connected points of the current transformer in the k-1 power frequency period if the sequence number of the current power frequency period is larger than 3;
obtaining the minimum value in the amplitude values of three-phase voltages of the grid-connected points of the current transformer in the k-2 power frequency period;
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if yes, then
And acquiring the phase angle of the updated virtual impedance by adopting a first method.
In this embodiment, the obtaining the phase angle of the updated virtual impedance further includes:
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if not, then
And acquiring the phase angle of the updated virtual impedance by adopting a second method.
In this embodiment, the first method is:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle, sgn, of the virtual impedance for k-2 power frequency cycles represents a sign function.
In this embodiment, the second method is:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle, sgn, of the virtual impedance for k-2 power frequency cycles represents a sign function.
In this embodiment, the determining whether the minimum value in the amplitude of the three-phase voltage at the grid-connected point of the current transformer in the kth-1 power frequency period and the minimum value in the amplitude of the three-phase voltage at the grid-connected point of the current transformer in the kth-2 power frequency period meet the preset condition includes:
judgment U min [k-1]≥U min [k-2]Whether the preset condition is met or not is judged if yes; wherein,
k is the kth power frequency period, U min [k-1]Is the minimum value, U, in the amplitude of three-phase voltage of the grid-connected point of the converter in the k-1 power frequency period min [k-2]The minimum value of the amplitude values of the three-phase voltages of the grid-connected point of the converter in the k-2 power frequency period is obtained.
In this embodiment, acquiring the phase angle of the updated virtual impedance further includes:
acquiring the sequence number of the current power frequency period, and if the sequence number of the current power frequency period is equal to 2
The phase angle of the updated virtual impedance is the phase angle + the disturbance step of the virtual impedance of the initial period or the phase angle of the updated virtual impedance is the phase angle-the disturbance step of the virtual impedance of the initial period.
In the present embodiment, the phase angle of the virtual impedanceAnd updating once every power frequency period.
The k represents the serial number of the current power frequency period, and when the kth power frequency period starts, the method is characterized in thatIs updated as the value ofWhen the kth power frequency period is finished, comparing the amplitude values of three-phase voltages of grid-connected points of the converter, wherein the minimum value is recorded as U min [k]。
In the present embodiment, the initial value of the phase angle of the virtual impedance of the initial periodSet to 90,
it can be understood that the value can also be selected by itself according to the requirement to obtain the serial number of the current power frequency period, if the serial number of the current power frequency period is equal to 2, namelySet to->Or-> wherein />Is the perturbation step size.
When k is more than or equal to 3, judging U min [k-1]≥U min [k-2]Whether or not it is.
If so, then it is determined by the following formula
If not, then it is determined by the following formula
In this embodiment, the following formula is adopted to obtain the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance:
wherein ,
in the course of this formula (ii) the formula,three-phase reference current for a current transformer> Three-phase voltage of grid-connected point of converter before grid fault> Three-phase voltage of grid-connected point of converter after grid fault>The A B C in the subscript corresponds to the A phase, B phase and C phase in the power system, respectively. Z S| and />The modulus and phase angle of the virtual impedance of the current transformer are represented, respectively.
The application is described in further detail below by way of examples, which should not be construed as limiting the application in any way.
Referring to fig. 3 and 4, the following net type converter control system of the present application is shown in fig. 3. A schematic diagram of the grid access with a grid converter is shown in fig. 4.
The rated voltage of the power grid is 380V, and the system impedance is 0.2+j1.5Ω. The length of each of the line 1 and the line 2 is 1km, and the impedance per unit length is 0.6+j0.16Ω/km. The maximum current allowable value of the current transformer is 60.8A, and the initial value of the virtual impedance phase angle thereof is set to 90 °. Before the power grid fails, the active power output by the converter is 12kW.
At t=0.06 s, an AB biphasic metallic short circuit occurs at the end of line 1. The process of adjusting the virtual impedance phase angle of the current transformer by the method of the application is shown in fig. 5. The virtual impedance modulus adjustment process of the current transformer is shown in fig. 6. The maximum value of the amplitude of the three-phase current outputted by the converter is accurately limited to the vicinity of the maximum allowable current value in the whole fault control process as shown in fig. 7. The minimum value of the three-phase voltage amplitude of the grid-connected point of the converter is shown in fig. 8, is continuously increased from the initial 87V in the fault control process, and is finally stabilized at 118V.
In the present embodiment of the present application, in the present embodiment,
the above formula can also be written in more specific form:
it is known that in the electric networkAfter failure, it is assumed that the A-phase voltage has shifted the most, i.e Middle->If the amplitude of (2) is maximum, the three-phase reference current generated by the converter is +.>In (I)>Is the largest.
In a word, the amplitude of the three-phase current output by the converter is automatically proportional to the reduction (offset) degree of the three-phase voltage of the grid-connected point, so that the three-phase voltage converter can be automatically adapted to different fault types.
In the case of a three-phase short circuit, the degree of deviation of each phase voltage is the same, and therefore, the current output from the current transformer is three-phase symmetrical, and each phase voltage is supported (lifted) to the same degree.
Under the condition of two-phase short circuit, the voltage deviation degree of the fault phase is obviously larger than that of the non-fault phase, so that the output current of the converter in the fault phase is also obviously larger than that of the non-fault phase, and the voltage of the fault phase can be supported more strongly.
The application also provides a reference current acquisition device of the grid-connected converter, which comprises a voltage drop acquisition module, a virtual impedance module value acquisition module, an updating module and a reference current acquisition module,
the voltage drop acquisition module is used for acquiring the voltage drop acting on the virtual impedance of the converter after the power grid fails;
the module for obtaining the module of the virtual impedance is used for obtaining the module of the virtual impedance;
the updating module is used for acquiring the phase angle of the updated virtual impedance;
the reference current acquisition module is used for acquiring the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
It will be appreciated that the description of the method above applies equally to the description of the device.
Fig. 2 is an exemplary structural diagram of an electronic device capable of implementing a method for acquiring a reference current of a grid-connected converter according to an embodiment of the present application.
As shown in fig. 2, the electronic device includes an input device 501, an input interface 502, a central processor 503, a memory 504, an output interface 505, and an output device 506. The input interface 502, the central processing unit 503, the memory 504, and the output interface 505 are connected to each other through a bus 507, and the input device 501 and the output device 506 are connected to the bus 507 through the input interface 502 and the output interface 505, respectively, and further connected to other components of the electronic device. Specifically, the input device 501 receives input information from the outside, and transmits the input information to the central processor 503 through the input interface 502; the central processor 503 processes the input information based on computer executable instructions stored in the memory 504 to generate output information, temporarily or permanently stores the output information in the memory 504, and then transmits the output information to the output device 506 through the output interface 505; the output device 506 outputs the output information to the outside of the electronic device for use by the user.
That is, the electronic device shown in fig. 2 may also be implemented to include: a memory storing computer-executable instructions; and one or more processors that, when executing the computer-executable instructions, implement the method of acquiring reference current for a grid-connected converter described in connection with fig. 1.
In one embodiment, the electronic device shown in FIG. 2 may be implemented to include: a memory 504 configured to store executable program code; the one or more processors 503 are configured to execute the executable program code stored in the memory 504 to perform the method for acquiring the reference current of the grid-connected converter in the above embodiment.
In one typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.
Computer-readable media include both permanent and non-permanent, removable and non-removable media, and the media may be implemented in any method or technology for storage of information. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Furthermore, it is evident that the word "comprising" does not exclude other elements or steps. A plurality of units, modules or means recited in the apparatus claims can also be implemented by means of software or hardware by means of one unit or total means. The terms first, second, etc. are used to identify names, and not any particular order.
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The processor referred to in this embodiment may be a central processing unit (Central Processing Unit, CPU), or other general purpose processor, digital signal processor (Digital Signal Processor, DSP), application specific integrated circuit (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory may be used to store computer programs and/or modules, and the processor may perform various functions of the apparatus/terminal device by executing or executing the computer programs and/or modules stored in the memory, and invoking data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program (such as a sound playing function, an image playing function, etc.) required for at least one function, and the like; the storage data area may store data (such as audio data, phonebook, etc.) created according to the use of the handset, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, memory, plug-in hard disk, smart Media Card (SMC), secure Digital (SD) Card, flash Card (Flash Card), at least one disk storage device, flash memory device, or other volatile solid-state storage device.
In this embodiment, the modules/units of the apparatus/terminal device integration may be stored in a computer readable storage medium if implemented in the form of software functional units and sold or used as a separate product. Based on such understanding, the present application may implement all or part of the flow of the method of the above embodiment, or may be implemented by hardware related to the instructions of a computer program, where the computer program may be stored in a computer readable storage medium, and when executed by a processor, the computer program may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, executable files or in some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), an electrical carrier signal, a telecommunications signal, a software distribution medium, and so forth.
It should be noted that the content of the computer readable medium can be appropriately increased or decreased according to the requirements of the legislation and the practice of the patent in the jurisdiction. While the application has been described in terms of preferred embodiments, it is not intended to limit the application thereto, and any person skilled in the art can make variations and modifications without departing from the spirit and scope of the present application, and therefore the scope of the application is to be determined from the appended claims.
While the application has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the application and are intended to be within the scope of the application as claimed.
Claims (10)
1. The reference current acquisition method of the grid-connected converter is used for power grid fault conditions and is characterized by comprising the following steps of:
acquiring voltage drop acting on virtual impedance of the converter after the power grid fault;
obtaining a model value of the virtual impedance;
acquiring the phase angle of the updated virtual impedance;
and obtaining the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
2. The method for obtaining the reference current of the grid-connected converter according to claim 1, wherein obtaining the voltage drop acting on the virtual impedance of the converter after the grid fault comprises:
acquiring three-phase voltage of a grid-connected point of the converter before a power grid fault;
acquiring three-phase voltage of a grid-connected point of the converter after the power grid fails;
and obtaining voltage drops acting on virtual impedance of the converter after the power grid fault according to the three-phase voltage of the grid connection point of the converter before the power grid fault and after the power grid fault.
3. The method for obtaining the reference current of the grid-connected converter as claimed in claim 2, wherein obtaining the modulus of the virtual impedance comprises:
acquiring the largest voltage drop of each phase of the virtual impedance as the largest voltage drop of each phase of the virtual impedance;
obtaining a maximum current allowable value of the converter;
and obtaining the modulus value of the virtual impedance according to the maximum value of the voltage drops of each phase of the virtual impedance and the maximum current allowable value of the converter.
4. The method for obtaining a reference current of a grid-connected converter as set forth in claim 3, wherein obtaining the phase angle of the updated virtual impedance comprises:
acquiring a phase angle of virtual impedance of an initial period;
acquiring a sequence number of a current power frequency period, and acquiring the minimum value of the amplitude values of the three-phase voltages of the grid-connected points of the current transformer in the k-1 power frequency period if the sequence number of the current power frequency period is larger than 3;
obtaining the minimum value in the amplitude values of three-phase voltages of the grid-connected points of the current transformer in the k-2 power frequency period;
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if yes, then
And acquiring the phase angle of the updated virtual impedance by adopting a first method.
5. The method for obtaining a reference current for a grid-connected converter as set forth in claim 4, wherein said obtaining the phase angle of the updated virtual impedance further comprises:
judging whether the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-1 power frequency period and the minimum value in the amplitude values of the three-phase voltages of the grid-connected point of the current transformer in the k-2 power frequency period meet preset conditions, if not, then
And acquiring the phase angle of the updated virtual impedance by adopting a second method.
6. The method for obtaining a reference current for a grid-connected converter as set forth in claim 4, wherein said obtaining the phase angle of the updated virtual impedance further comprises:
acquiring the sequence number of the current power frequency period, and if the sequence number of the current power frequency period is equal to 2
The phase angle of the updated virtual impedance is the phase angle + the disturbance step of the virtual impedance of the initial period or the phase angle of the updated virtual impedance is the phase angle-the disturbance step of the virtual impedance of the initial period.
7. The method for obtaining the reference current of the grid-connected converter as claimed in claim 4, wherein the first method is as follows:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle of the virtual impedance for k-2 power frequency cycles, sgn, represents a sign function; the second method comprises the following steps:
the phase angle of the updated virtual impedance is obtained by adopting the following formula:
wherein ,
the phase angle k of the virtual impedance after updating is k power frequency period +.>Is the perturbation step size, +.>Phase angle of virtual impedance for k-1 power frequency cycles, +.>The phase angle, sgn, of the virtual impedance for k-2 power frequency cycles represents a sign function.
8. The method for regulating and controlling the reference voltage of the networking type converter according to claim 4, wherein the determining whether the minimum value of the magnitudes of the three-phase voltages of the grid-connected point of the converter in the kth-1 power frequency period and the minimum value of the magnitudes of the three-phase voltages of the grid-connected point of the converter in the kth-2 power frequency period meet the preset condition comprises:
judgment U min [k-1]≥U min [k-2]Whether the preset condition is met or not is judged if yes; wherein,
k is the kth power frequency period, U min [k-1]Is the minimum value, U, in the amplitude of three-phase voltage of the grid-connected point of the converter in the k-1 power frequency period min [k-2]The minimum value of the amplitude values of the three-phase voltages of the grid-connected point of the converter in the k-2 power frequency period is obtained.
9. The method for regulating and controlling the reference voltage of the networking converter according to claim 1, wherein the reference current of the converter obtained according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance is obtained by adopting the following formula:
wherein ,
three-phase reference current representing a current transformer, +.>Is the three-phase voltage of the grid-connected point of the converter before the power grid fault, < +.>Is the three-phase voltage of the grid-connected point of the converter after the power grid fault.
10. The reference current acquisition device of the grid-connected converter is characterized by comprising the following components:
the voltage drop acquisition module is used for acquiring the voltage drop acting on the virtual impedance of the converter after the power grid fault;
the virtual impedance module is used for acquiring the virtual impedance module;
the updating module is used for acquiring the phase angle of the updated virtual impedance;
the reference current acquisition module is used for acquiring the reference current of the converter according to the voltage drop acting on the virtual impedance of the converter after the power grid fault, the modulus value of the virtual impedance and the phase angle of the virtual impedance.
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| CN117895555A (en) * | 2024-03-12 | 2024-04-16 | 南方电网数字电网研究院股份有限公司 | Electric automobile fills electric pile that possesses trouble electric wire netting and supports and emergent power supply function |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117895555A (en) * | 2024-03-12 | 2024-04-16 | 南方电网数字电网研究院股份有限公司 | Electric automobile fills electric pile that possesses trouble electric wire netting and supports and emergent power supply function |
| CN117895555B (en) * | 2024-03-12 | 2024-08-13 | 南方电网数字电网研究院股份有限公司 | Electric automobile fills electric pile that possesses trouble electric wire netting and supports and emergent power supply function |
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