CN117590125A - Island detection method and device, storage medium and converter system - Google Patents
Island detection method and device, storage medium and converter system 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
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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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
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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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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Abstract
The application provides an island detection method, an island detection device, a storage medium and a converter system. The method comprises the following steps: monitoring whether a first alternating current frequency of the grid-connected converter in a normal operation mode falls into a preset first frequency range or not in real time; if the first alternating current frequency does not fall into the first frequency range, calculating a target active instruction value according to the offset of the first alternating current frequency relative to the rated frequency of the system; the active power instruction value of the grid-formed converter is adjusted from an original value to a target active instruction value; monitoring whether a second alternating current frequency of the grid-formed converter after being adjusted to a target active instruction value falls into a preset second frequency range or not; if the second alternating current frequency is monitored not to fall into the second frequency range, identifying whether the second alternating current frequency within the first preset time period from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range; if yes, determining that island occurs. The method and the device can improve the accuracy of isolated island detection of the grid-structured converter.
Description
Technical Field
The application relates to the technical field of electric power, in particular to an island detection method, an island detection device, a storage medium and a converter system.
Background
The new energy power generation is accelerating the conversion from the auxiliary power supply to the main power supply. The characteristics of double heights (high-proportion new energy and high-proportion power electronic equipment) of the novel power system change the stable form and operation characteristics of the power system, and the problems of reduced short-circuit capacity, reduced inertia, damping loss and the like of the system bring challenges to the safe and stable operation of the power system in the future. With the continuous and deep research of the theory of the networking control technology, the current industry generally considers networking control as a feasible solution for guaranteeing the safe and stable operation of a novel power system.
The grid-structured converter can be operated in a grid-connected mode or an island mode stably without switching a control structure due to the voltage source output characteristic, so that the grid-structured converter is widely applied to a novel power system. However, when an unplanned island occurs, the output voltage and frequency of the grid-connected converter are relatively stable, and the island state cannot be detected by adopting the conventional method.
Disclosure of Invention
The embodiment of the application provides an island detection method, an island detection device, a storage medium and a converter system, which can improve the island detection accuracy of a network-structured converter.
In a first aspect, the present application provides an island detection method, the method including:
monitoring whether a first alternating current frequency of the grid-connected converter in a normal operation mode falls into a preset first frequency range or not in real time; the first frequency range is the normal operation frequency range of the grid-connected converter;
if the first alternating current frequency does not fall into the first frequency range, calculating a target active instruction value according to the offset of the first alternating current frequency relative to the rated frequency of the system;
the active power instruction value of the grid-built converter is adjusted from an original value to the target active instruction value;
monitoring whether a second alternating current frequency of the grid-structured converter after being adjusted to the target active instruction value falls into a preset second frequency range or not; the second frequency range is the island protection critical frequency range;
if the second alternating current frequency is monitored not to fall into the second frequency range, identifying whether the second alternating current frequency which passes through the first preset time length from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range;
if yes, determining that island occurs.
In one embodiment, the identifying whether the second ac frequency does not fall within the second frequency range after the first time of the out-of-limit of the second ac frequency passes within a first preset time period includes:
and identifying whether the second alternating current frequency passing through the first preset time period from the first time of out-of-limit of the second alternating current frequency is larger than the upper limit value of the second frequency range or smaller than the lower limit value of the second frequency range.
In one embodiment, the method further comprises:
and if the second alternating current frequency within the second preset time period from the moment when the grid-built current transformer is adjusted to the target active power instruction value is in the second frequency range, judging that island does not occur, and adjusting the active power instruction value of the grid-built current transformer to the original value.
In one embodiment, the calculating the target active command value according to the offset of the first ac frequency with respect to the system operating frequency includes:
calculating the target active command value based on the following formula:
wherein P is ref For the target active instruction value, m is a preset island detection coefficient, f is a first alternating frequency, f 1 For the nominal frequency of the system, P 0 Is the original value of the active power command value.
In one embodiment, the island detection coefficient has a value range of:
wherein K is p And controlling the ring droop coefficient for the active synchronization of the grid-structured converter.
In one embodiment, the method further comprises:
if the island is judged to occur, reporting the island state.
In one embodiment, the method further comprises:
and if the second alternating current frequency does not fall into the second frequency range and the second alternating current frequency within the first preset time period from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range, judging that other types of disturbance occur.
In a second aspect, the present application provides an islanding detection device, the device comprising:
the first monitoring module is used for monitoring whether the first alternating frequency of the grid-connected converter in the normal operation mode falls into a preset first frequency range or not in real time; the first frequency range is the normal operation frequency range of the grid-connected converter;
the calculation module is used for calculating a target active instruction value according to the offset of the first alternating current frequency relative to the rated frequency of the system when the first alternating current frequency does not fall into the first frequency range;
the command value adjusting module is used for adjusting the active power command value of the grid-structured converter from an original value to the target active command value;
the second monitoring module is used for monitoring whether the second alternating current frequency of the grid-structured converter after being adjusted to the target active instruction value falls into a preset second frequency range or not; the second frequency range is the island protection critical frequency range;
the frequency out-of-limit judging module is used for identifying whether the second alternating current frequency within the first preset duration from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range when the second alternating current frequency is monitored not to fall into the second frequency range;
the island judging module is used for judging that island occurs when the fact that the second alternating current frequency within the first preset duration from the first out-of-limit time of the second alternating current frequency is not in the second frequency range is recognized.
In a third aspect, the present application provides a storage medium having stored therein computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of the islanding detection method as described in any of the preceding claims.
In a fourth aspect, the present application provides a converter system comprising:
the grid-connected converter is used for accessing the power grid system through the switch unit;
the sampling unit is used for collecting the output voltage and the output current of the grid-structured converter;
the frequency detection unit is used for calculating the alternating current frequency of the grid-built converter based on the output voltage and the output current acquired by the sampling unit;
and the control unit is used for acquiring the alternating frequency fed back by the frequency detection unit in real time and executing the steps of the island detection method.
From the above technical solutions, the embodiments of the present application have the following advantages:
according to the island detection method, the island detection device, the storage medium and the converter system, whether the alternating current frequency falls into the first frequency range is monitored when the grid-built converter normally operates, when the first frequency range is monitored, the active power instruction value of the grid-built converter is adjusted according to the offset of the first alternating current frequency relative to the rated frequency of the system, the active power instruction value is adjusted to be a target active power instruction value by an original value, whether the alternating current frequency of the grid-built converter falls into the second frequency range in the current mode is monitored, the first out-of-limit moment is monitored when the second frequency range is not monitored, and whether the alternating current frequency within the first preset duration does not fall into the second frequency range is identified to judge whether island occurs. Island detection of the grid-structured converter can be achieved without injecting disturbance signals, island occurrence judgment is carried out through alternating current frequency within a first preset duration, misjudgment caused by other disturbance is eliminated, and accuracy of non-planned island detection is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive faculty for a person skilled in the art.
Figure 1 is a block diagram of a current transformer system in one embodiment;
FIG. 2 is a flow chart of an island detection method in one embodiment;
FIG. 3 is a block diagram of an island detection device in one embodiment;
FIG. 4 is an internal block diagram of a computer device, in one embodiment.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
In some embodiments, the island detection method provided in the embodiments of the present application is applied to the control unit 140 in the converter system 100 shown in fig. 1. The converter system comprises a grid-formed converter 110, a sampling unit 120, a frequency detection unit 130 and a control unit 140. Wherein, the grid-connected converter 110 is used for accessing the power grid system through the switch unit; the sampling unit 120 is configured to collect an output voltage and an output current of the grid-configured converter 110; the frequency detection unit 130 is configured to calculate an ac frequency of the grid-configured converter 110 based on the output voltage and the output current acquired by the sampling unit 120; and the control unit 140 is configured to acquire the ac frequency fed back by the frequency detection unit 130 in real time, and perform an island detection method. The control unit 140 is further configured to calculate active power and reactive power output by the grid-connected converter 110 according to the output voltage and current signals collected by the sampling unit 120, and generate a pulse trigger signal to control the switching device of the grid-connected converter 110 through power synchronous control and voltage/current inner loop control.
In some embodiments, the control unit 140 includes a power calculation module, an island detection module, a voltage/current inner loop control module, and a power synchronization control module. A power calculation module, configured to calculate active power and reactive power output by the grid-configured converter 110 based on the output voltage and output current collected by the sampling unit 120; the island detection module is used for executing the island detection method; the voltage/current inner loop control module and the power synchronous control are used for cooperating to generate a pulse trigger signal to control the switching device of the grid-connected converter 110.
As shown in fig. 2, an embodiment of the present application provides an island detection method, where the method includes:
step S201 monitors in real time whether the first ac frequency of the grid-connected converter in the normal operation mode falls within a preset first frequency range.
Wherein the first frequency range is the normal operating frequency range of the grid-connected converter, which may be set according to grid standards, e.g. in some embodiments may be [49.8,50.2hz ].
In step S202, if the first ac frequency falls within the first frequency range, it is determined that island does not occur.
At this time, the process returns to step S201, and the monitoring of the first ac frequency is continued.
In step S203, if the first ac frequency does not fall within the first frequency range, a target active command value is calculated according to the offset of the first ac frequency with respect to the nominal frequency of the system.
The rated frequency of the system refers to the rated frequency of the steady-state operation of the power system, such as 50Hz or 60Hz.
When the first ac frequency does not fall into the first frequency range, the first ac frequency may be fluctuation generated in a normal working state, may be offset caused by disturbance, or may be isolated, and even if the isolated island occurs, the offset is smaller, so that the accurate judgment cannot be performed. In this embodiment, the network transformer is controlled according to the target active command value calculated by the offset of the first ac frequency relative to the rated frequency of the system, so as to exacerbate the frequency offset of the network transformer, and then judge the frequency offset.
Step S204, the active power instruction value of the grid-structured converter is adjusted from the original value to the target active instruction value.
The frequency offset of the grid-connected converter can be increased by adjusting the active power command value to the target active command value based on the droop characteristics of the grid-connected converter.
In step S205, it is monitored whether the second ac frequency of the grid-configured converter after being adjusted to the target active command value falls within a preset second frequency range.
The second frequency range is an island protection critical frequency range, and the specific range may be set according to a power grid standard, for example, in some embodiments, the second frequency range may be [49.3,50.5hz ].
In step S206, if it is detected that the second ac frequency does not fall within the second frequency range, it is identified whether the second ac frequency within the first preset time period from the first out-of-limit time of the second ac frequency does not fall within the second frequency range.
The first out-of-limit time refers to a time when the second ac frequency is first identified as not falling into the second frequency range after the active power command value is adjusted to the target active command value. Since normal operation or other types of disturbances may also cause the second ac frequency to be out of limit, it is necessary to monitor the second ac frequency within a first predetermined period of time to accurately determine whether islanding has occurred.
Step S207, if yes, determining that island occurs.
In step S208, if the second ac frequency does not fall within the second frequency range and the second ac frequency within the first preset duration from the first time of out-of-limit of the second ac frequency does not fall within the second frequency range, it is determined that other types of disturbance occur.
If the second alternating current frequency is out of limit and is in oscillation change due to the occurrence of other types of disturbance, the second alternating current frequency which passes through the first preset time from the first out of limit time of the second alternating current frequency does not fall into the second frequency range, namely, the second alternating current frequency falls into the second frequency range partially, and the condition that the second alternating current frequency is out of limit partially is judged to occur. According to the embodiment, the second alternating current frequency in a period of time is observed through setting the time window, judgment is carried out based on the characteristic of the island state and the difference between other types of disturbance, the situation that the other types of disturbance are misjudged as island occurrence is eliminated, and the accuracy is improved. In some embodiments, the first preset time period is 200ms.
Step S209, if the second AC frequency within the second preset time period is within the second frequency range from the moment when the grid-connected converter is adjusted to the target active command value, determining that island does not occur, and adjusting the active power command value of the grid-connected converter to the original value.
Returning to step S201, monitoring of the first ac frequency is continued. After the active power command value of the grid-connected converter is adjusted, the control unit controls the active power command value according to the adjusted active power command value, and the frequency change is changed into continuous change, so that a time window with second preset duration is set to observe the second alternating current frequency, if the active power command value is in a second frequency range, the island is judged not to occur, and erroneous judgment caused by hysteresis of the frequency change is avoided. At this time, the first alternating current frequency is indicated to be out of limit and change under non-island disturbance, so that the active power instruction value can be adjusted to the original value, the normal operation of the grid-structured converter is controlled, and the monitoring is continued.
According to the island detection method, whether the alternating current frequency falls into the first frequency range is monitored when the grid-connected converter normally operates, when the first frequency range is monitored, the active power instruction value of the grid-connected converter is adjusted according to the offset of the first alternating current frequency relative to the rated frequency of the system, the active power instruction value is adjusted to be a target active power instruction value by the original value, whether the alternating current frequency of the grid-connected converter falls into the second frequency range in the current mode is monitored, when the first out-of-limit time is monitored when the second frequency range is not monitored, whether the alternating current frequency within the first preset duration does not fall into the second frequency range is identified, and whether island occurs is judged. Island detection of the grid-connected converter can be realized without injecting disturbance signals, and adverse effects on the system power quality in a grid-connected mode are avoided. And judging the occurrence of the island through the alternating current frequency in the first preset duration, eliminating misjudgment caused by other disturbance, and improving the accuracy of the non-planned island detection. On the other hand, the method only needs to monitor the frequency and regulate and control the active power instruction value, so that the method can be applied to the original control system of the grid-structured converter, is simple to realize and has high adaptability.
In one embodiment, the identifying whether the second ac frequency does not fall within the second frequency range after the first time of the out-of-limit of the second ac frequency passes within the first preset time period includes:
and identifying whether the second alternating current frequency within the first preset time period from the first out-of-limit time of the second alternating current frequency is larger than the upper limit value of the second frequency range or smaller than the lower limit value of the second frequency range.
In this embodiment, based on the frequency variation characteristic of the grid-connected converter in the island state, when the island occurs, the variation of the second ac frequency should be unidirectional out-of-limit, rather than oscillating, and by identifying whether the second ac frequency within the first preset duration from the moment when the second ac frequency first out-of-limit is greater than the upper limit value of the second frequency range, or whether the second ac frequency is less than the lower limit value of the second frequency range, misjudgment caused by other factors is further eliminated, and the accuracy of island detection is improved.
In one embodiment, the calculating the target active command value according to the offset of the first ac frequency relative to the system operating frequency includes:
calculating a target active command value based on:
wherein P is ref For the target active instruction value, m is a preset island detection coefficient, f is a first alternating frequency, f 1 For the nominal frequency of the system, P 0 Is the original value of the active power command value.
In one embodiment, the island detection coefficient has a value range of:
wherein K is p The droop coefficient of the loop is synchronously controlled for the active power of the network-structured converter.
In this embodiment, by limiting the value range of the island detection coefficient, system instability caused by excessive adjustment when the active power command value is adjusted is avoided. The larger the island detection coefficient is within the range, the smaller the island Non-detection zone (NDZ) is, the shorter the detection time is, but the smaller the stability margin of the grid-structured converter is, and the person skilled in the art can select according to actual needs.
In one embodiment, the method further comprises:
if the island is judged to occur, reporting the island state.
In this embodiment, when determining that an island occurs, the control unit reports the island state to the upper control system, and performs island protection in time. If the grid-connected converter cannot timely detect the island state, the grid-connected switch and related equipment may be damaged due to out-of-step switching. In addition, faults can not be cleared in time, and the recovery of the power grid to a normal operation state is affected. Meanwhile, it is considered that an maintainer who is not electrified will be threatened by security. The island detection method provided by the application realizes timely and accurate detection, and can timely report when island occurrence is detected, so that island protection can be timely carried out, the occurrence of the above-mentioned harm is avoided, and the stability and safety of system operation are improved.
It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.
The island detection device provided in the embodiments of the present application is described below, and the island detection device described below and the island detection method described above may be referred to correspondingly.
As shown in fig. 3, an embodiment of the present application provides an island detection device 300, which includes:
the first monitoring module 301 is configured to monitor in real time whether a first ac frequency of the grid-connected converter in a normal operation mode falls within a preset first frequency range; the first frequency range is the normal operation frequency range of the grid-connected converter;
a calculation module 302, configured to calculate a target active command value according to an offset of the first ac frequency relative to a nominal frequency of the system when the first ac frequency does not fall within the first frequency range;
the instruction value adjusting module 303 is configured to adjust an active power instruction value of the grid-configured converter from an original value to the target active instruction value;
the second monitoring module 304 is configured to monitor whether a second ac frequency of the grid-configured converter after being adjusted to the target active command value falls within a preset second frequency range; the second frequency range is the island protection critical frequency range;
the frequency out-of-limit judging module 305 is configured to identify, when it is monitored that the second ac frequency does not fall within the second frequency range, whether the second ac frequency within a first preset duration from a first out-of-limit time of the second ac frequency does not fall within the second frequency range;
and the island determination module 306 is configured to determine that island occurs when it is identified that none of the second ac frequencies within the first preset duration from the first out-of-limit time of the second ac frequency falls within the second frequency range.
In one embodiment, the frequency out-of-limit determination module is configured to perform the steps of:
and identifying whether the second alternating current frequency passing through the first preset time period from the first time of out-of-limit of the second alternating current frequency is larger than the upper limit value of the second frequency range or smaller than the lower limit value of the second frequency range.
In one embodiment, the islanding determination module is further configured to perform the steps of:
and if the second alternating current frequency within the second preset time period from the moment when the grid-built current transformer is adjusted to the target active power instruction value is in the second frequency range, judging that island does not occur, and adjusting the active power instruction value of the grid-built current transformer to the original value.
In one embodiment, the computing module is configured to perform the steps of:
calculating a target active command value based on:
wherein P is ref For the target active instruction value, m is a preset island detection coefficient, f is a first alternating frequency, f 1 For the nominal frequency of the system, P 0 Is the original value of the active power command value.
In one embodiment, the island detection device further comprises:
and the reporting module is used for reporting the island state when the island is judged to occur.
In one embodiment, the islanding determination module is further configured to perform the steps of:
if the second alternating current frequency does not fall into the second frequency range and the second alternating current frequency within the first preset time period from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range, judging that other types of disturbance occur.
The above-mentioned division of the individual modules in the island detection device is only for illustration, and in other embodiments, the island detection device may be divided into different modules as needed to complete all or part of the functions of the island detection device. The individual modules in the island detection device described above may be implemented in whole or in part by software, hardware, or a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
In one embodiment, the present application also provides a storage medium having stored therein computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of the islanding detection method as described in any of the embodiments above.
In an embodiment, the control unit of the converter system has stored therein computer readable instructions, which when executed by the one or more processors, perform the steps of the islanding detection method as described in any of the embodiments above.
In one embodiment, a computer device, which may be a terminal, whose internal structure may be as shown in fig. 4, is provided as a control unit of the converter system. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. The computer program is executed by a processor to implement an islanding detection method. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be keys, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.
Those skilled in the art will appreciate that the structures shown in FIG. 4 are block diagrams only and do not constitute a limitation of the computer device on which the present aspects apply, and that a particular computer device may include more or less components than those shown, or may combine some of the components, or have a different arrangement of components.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in the various embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like. The processors referred to in the embodiments provided herein may be general purpose processors, central processing units, graphics processors, digital signal processors, programmable logic units, quantum computing-based data processing logic units, etc., without being limited thereto.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.
In the present specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and may be combined according to needs, and the same similar parts may be referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An island detection method, the method comprising:
monitoring whether a first alternating current frequency of the grid-connected converter in a normal operation mode falls into a preset first frequency range or not in real time; the first frequency range is the normal operation frequency range of the grid-connected converter;
if the first alternating current frequency does not fall into the first frequency range, calculating a target active instruction value according to the offset of the first alternating current frequency relative to the rated frequency of the system;
the active power instruction value of the grid-built converter is adjusted from an original value to the target active instruction value;
monitoring whether a second alternating current frequency of the grid-structured converter after being adjusted to the target active instruction value falls into a preset second frequency range or not; the second frequency range is the island protection critical frequency range;
if the second alternating current frequency is monitored not to fall into the second frequency range, identifying whether the second alternating current frequency which passes through the first preset time length from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range;
if yes, determining that island occurs.
2. The island detection method according to claim 1, wherein the identifying whether none of the second ac frequencies within a first preset time period from the first out-of-limit time of the second ac frequency falls within the second frequency range comprises:
and identifying whether the second alternating current frequency passing through the first preset time period from the first time of out-of-limit of the second alternating current frequency is larger than the upper limit value of the second frequency range or smaller than the lower limit value of the second frequency range.
3. The island detection method of claim 1, further comprising:
and if the second alternating current frequency within the second preset time period from the moment when the grid-built current transformer is adjusted to the target active power instruction value is in the second frequency range, judging that island does not occur, and adjusting the active power instruction value of the grid-built current transformer to the original value.
4. The island detection method according to claim 1, wherein the calculating a target active command value from an offset of the first alternating current frequency with respect to a system operation frequency includes:
calculating the target active command value based on the following formula:
wherein P is ref For the target active command value, m is a preset island detection systemThe number f is the first alternating frequency, f1 is the rated frequency of the system, and P0 is the original value of the active power instruction value.
5. The island detection method according to claim 4, wherein the island detection coefficient has a value ranging from:
wherein K is p And controlling the ring droop coefficient for the active synchronization of the grid-structured converter.
6. The island detection method of any of claims 1 to 5, wherein the method further comprises:
if the island is judged to occur, reporting the island state.
7. The island detection method of claim 1, further comprising:
and if the second alternating current frequency does not fall into the second frequency range and the second alternating current frequency within the first preset time period from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range, judging that other types of disturbance occur.
8. An islanding detection device, characterized in that the device comprises:
the first monitoring module is used for monitoring whether the first alternating frequency of the grid-connected converter in the normal operation mode falls into a preset first frequency range or not in real time; the first frequency range is the normal operation frequency range of the grid-connected converter;
the calculation module is used for calculating a target active instruction value according to the offset of the first alternating current frequency relative to the rated frequency of the system when the first alternating current frequency does not fall into the first frequency range;
the command value adjusting module is used for adjusting the active power command value of the grid-structured converter from an original value to the target active command value;
the second monitoring module is used for monitoring whether the second alternating current frequency of the grid-structured converter after being adjusted to the target active instruction value falls into a preset second frequency range or not; the second frequency range is the island protection critical frequency range;
the frequency out-of-limit judging module is used for identifying whether the second alternating current frequency within the first preset duration from the first out-of-limit time of the second alternating current frequency does not fall into the second frequency range when the second alternating current frequency is monitored not to fall into the second frequency range;
the island judging module is used for judging that island occurs when the fact that the second alternating current frequency within the first preset duration from the first out-of-limit time of the second alternating current frequency is not in the second frequency range is recognized.
9. A storage medium having stored therein computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of the islanding detection method as claimed in any one of claims 1 to 7.
10. A current transformer system, comprising:
the grid-connected converter is used for accessing the power grid system through the switch unit;
the sampling unit is used for collecting the output voltage and the output current of the grid-structured converter;
the frequency detection unit is used for calculating the alternating current frequency of the grid-built converter based on the output voltage and the output current acquired by the sampling unit;
the control unit is used for acquiring the alternating current frequency fed back by the frequency detection unit in real time and executing the steps of the island detection method according to any one of claims 1 to 7.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117805541A (en) * | 2024-02-29 | 2024-04-02 | 西安千帆翼数字能源技术有限公司 | Island detection method, protection method and related device of energy storage converter |
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| CN117805541A (en) * | 2024-02-29 | 2024-04-02 | 西安千帆翼数字能源技术有限公司 | Island detection method, protection method and related device of energy storage converter |
| CN117805541B (en) * | 2024-02-29 | 2024-05-03 | 西安千帆翼数字能源技术有限公司 | Island detection method, protection method and related device of energy storage converter |
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