CN115207981B - Low-frequency injection type anti-islanding protection method and system for multi-path photovoltaic access platform area - Google Patents

Low-frequency injection type anti-islanding protection method and system for multi-path photovoltaic access platform area Download PDF

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CN115207981B
CN115207981B CN202211112633.2A CN202211112633A CN115207981B CN 115207981 B CN115207981 B CN 115207981B CN 202211112633 A CN202211112633 A CN 202211112633A CN 115207981 B CN115207981 B CN 115207981B
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frequency
voltage
load
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CN115207981A (en
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刘海涛
邓大上
张波
王岗
费烨
何连杰
周勐
杨红磊
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China Online Shanghai Energy Internet Research Institute Co ltd
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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
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/006—Calibration or setting of parameters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • 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
    • 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
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Abstract

The invention discloses a low-frequency injection type anti-islanding protection method and system for a multi-channel photovoltaic access platform area. Wherein, the method comprises the following steps: injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a power distribution station area, and monitoring a low-frequency voltage and current phase angle difference; determining an impedance angle setting value according to system parameters, determining a load side power factor angle according to load parameters, and confirming that the impedance angle setting value and the load side power factor angle meet a certain proportional relation; and comparing the low-frequency voltage current phase angle difference with the impedance angle setting value, judging that the system is in an island operation state when the impedance angle setting value and the low-frequency voltage current phase angle difference meet a certain proportional relation, and sending a tripping command of the photovoltaic grid-connected circuit breaker to the station area fusion terminal.

Description

Low-frequency injection type anti-islanding protection method and system for multi-path photovoltaic access platform area
Technical Field
The invention relates to the technical field of anti-islanding protection, in particular to a low-frequency injection type anti-islanding protection method and system for a multi-channel photovoltaic access platform area.
Background
Anti-islanding methods can be mainly divided into two main categories: a passive detection method and an active detection method.
The passive method utilizes the change of the voltage, the frequency, the phase or the harmonic wave of the output end of the inverter when the power grid is cut off to carry out the island effect detection. The passive detection method is generally simple to implement, however, when the output power of the grid-connected inverter is basically close to the power of the local grid load, and thus the voltage and frequency of the local grid change very little, the passive detection method fails, and a large non-detection area exists in the method.
The active island detection method is characterized in that output power, frequency or phase of an inverter are disturbed to a certain extent by controlling the inverter. When the grid is working normally, these disturbances are not detected due to the balancing effect of the grid. Once the grid fails, the disturbance of the inverter output will quickly accumulate and go outside the allowable range, thereby triggering the islanding detection circuit. The active detection method has high detection precision, but the control is more complex, and the quality of the output electric energy of the inverter is reduced. Meanwhile, the active injection method mostly adopts harmonic injection, but the harmonic content of the system is relatively high, so that the detection effect is influenced.
In the conventional anti-islanding monitoring method related to the voltage-current phase angle difference, the voltage-current phase angle difference is the voltage-current phase angle difference of the output end of the inverter, and the scheme is based on a fundamental wave 50HZ signal or a harmonic signal. The scheme is only suitable for the condition that only one path of distributed photovoltaic access exists in a transformer area, the load impedance can be reflected only by the voltage-current phase angle difference of the output end of the inverter at the moment, if the system has multi-path distributed photovoltaic access, the method is not established, and the method does not have universal applicability; meanwhile, due to the influence of system harmonic waves, the problem of large errors of the scheme also exists, and the condition of large-scale application is not met.
Disclosure of Invention
According to the invention, the low-frequency injection type anti-islanding protection method and system for the multi-channel photovoltaic access transformer area are provided, so that the problems of poor adaptability, high misjudgment rate, influence on electric energy quality and the like in the conventional anti-islanding protection method are solved.
According to a first aspect of the invention, a low-frequency injection type anti-islanding protection method for a multi-channel photovoltaic access platform area is provided, which comprises the following steps:
injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a power distribution station area, and monitoring the phase angle difference of the low-frequency voltage and current;
determining an impedance angle setting value according to system parameters; determining a load side power factor angle according to the load parameter; confirming that the impedance angle setting value and the load side power factor angle meet a certain proportional relation;
and comparing the low-frequency voltage current phase angle difference with the impedance angle setting value, judging that the system is in an island operation state when the impedance angle setting value and the low-frequency voltage current phase angle difference meet a certain proportional relation, and sending a tripping command of the photovoltaic grid-connected circuit breaker to the station area fusion terminal.
According to a second aspect of the present invention, there is provided a low frequency injection anti-islanding system for a multi-channel photovoltaic access platform, comprising:
the voltage and current phase angle difference monitoring module is used for injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a power distribution station area and monitoring the low-frequency voltage and current phase angle difference through the voltage and current phase angle difference monitoring unit;
the impedance angle setting value and load side power factor angle determining module is used for determining an impedance angle setting value according to system parameters; determining a load side power factor angle according to the load parameter; confirming that the impedance angle setting value and the load side power factor angle meet a certain proportional relation;
and the island operation state judging module is used for comparing the low-frequency voltage current phase angle difference with the impedance angle setting value, judging that the system is in an island operation state when the impedance angle setting value and the low-frequency voltage current phase angle difference meet a certain proportional relation, and sending a tripping command of the photovoltaic grid-connected circuit breaker to the platform area fusion terminal.
According to a third aspect of the present invention, there is provided the storage medium having stored thereon a computer program for executing the method of any one of the above.
According to the invention, a low-frequency small power supply is injected into a low-voltage bus of a distribution substation, the phase angle difference of low-frequency voltage and current is monitored and compared with the impedance angle setting value, and the grid-connected operation or island operation state of the system can be detected. Harmonic interference is eliminated to this scheme, and the rate of accuracy is high, and along with a large amount of access distribution station districts of distributed photovoltaic, this scheme also is applicable to the condition that multichannel distributed photovoltaic inserts. The detection method does not need any complex calculation, and has good sensitivity, selectivity and rapidity.
Drawings
Exemplary embodiments of the invention may be more completely understood in consideration of the following drawings:
fig. 1 is a schematic flow chart of a low-frequency injection type anti-islanding protection method for a multi-channel photovoltaic access platform area according to this embodiment;
fig. 2 is a schematic structural diagram of a low-frequency injection type anti-islanding protection system of a multi-channel photovoltaic access platform area according to this embodiment;
fig. 3 is a schematic view of an application scenario and a system signal transmission flow of a low-frequency injection type anti-islanding protection system of a multi-channel photovoltaic access distribution room according to this embodiment.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
According to a first aspect of the present invention, there is provided a low-frequency injection anti-islanding protection method 100 for a multi-channel photovoltaic-connected platform, and referring to fig. 1, the method 100 includes:
s101, injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a distribution substation, and monitoring the low-frequency power supplyPhase angle difference of voltage and current
Figure 104570DEST_PATH_IMAGE001
；
S102, determining an impedance angle setting value according to system parameters
Figure 765358DEST_PATH_IMAGE002
(ii) a Determining a load side power factor angle according to a load parameter
Figure 845310DEST_PATH_IMAGE003
(ii) a Confirming impedance angle setting value
Figure 933351DEST_PATH_IMAGE004
Angle with load side power factor
Figure 465964DEST_PATH_IMAGE005
A certain proportional relation is satisfied;
s103, comparing the voltage and current phase angle difference
Figure 930443DEST_PATH_IMAGE006
And the impedance angle setting value
Figure 864901DEST_PATH_IMAGE007
Making a comparison and when the impedance angle is set
Figure 123844DEST_PATH_IMAGE007
Phase angle difference with the voltage and current
Figure 878174DEST_PATH_IMAGE008
And when a certain proportional relation is met, judging that the system is in an island operation state, and sending a tripping command of the photovoltaic grid-connected circuit breaker to the station area fusion terminal. Optionally, a low-frequency small power supply and a band-pass filtering unit are injected at a low-voltage bus of the distribution substation area, and the phase angle difference of the low-frequency voltage and the low-frequency current is monitored
Figure 146344DEST_PATH_IMAGE008
The method comprises the following steps:
the low-frequency small power supply is a sine wave with the frequency lower than 50HZ, and can be a voltage source or a current source;
acquiring signals of a low-frequency band through a band-pass filtering unit and shielding signals of other frequency bands;
monitoring the phase angle difference of the low-frequency voltage and the current
Figure 935308DEST_PATH_IMAGE009
。
In this embodiment, a low-frequency 20HZ voltage source and a band-pass filter unit are injected into a low-voltage bus of a distribution substation area, and a voltage-current phase angle difference of 20HZ is monitored
Figure 365153DEST_PATH_IMAGE009
。
Optionally, determining an impedance angle setting based on system parameters
Figure 872357DEST_PATH_IMAGE010
Determining the load-side power factor angle according to the load parameter
Figure 678639DEST_PATH_IMAGE011
Confirming the setting value of the impedance angle
Figure 322110DEST_PATH_IMAGE012
Angle with load side power factor
Figure 922856DEST_PATH_IMAGE013
The proportional relationship of (1) includes:
calculating and determining reactance X1 and resistance R1 values of the medium-voltage system line under low frequency according to the length and model parameters of the medium-voltage line;
calculating and determining a reactance X2 value of the distribution transformer under low frequency according to parameters of the medium-voltage distribution transformer;
according to the reactance X1 and the resistance R1 of the medium-voltage system line and the reactance X2 of the distribution transformer, the impedance angle setting value is calculated and determined
Figure 651778DEST_PATH_IMAGE014
。
Determining a load side power factor angle according to the load parameter, comprising:
calculating and determining reactance X3 and resistance R3 values of the load side line under low frequency according to the length and model parameters of the load line;
according to the load size and the power factor, calculating and determining equivalent reactance X4 and resistance R4 values of the load under low frequency;
calculating the power factor angle of the load side of the transformer area according to X3, R3, X4 and R4
Figure 261750DEST_PATH_IMAGE015
。
Specifically, the low frequency A (A) of the medium voltage system line is calculated and determined according to the length L1 of the medium voltage line, the reactance value x1 per unit length and the resistance value r1 per unit length<50 Reactance at HZ
Figure 759728DEST_PATH_IMAGE016
Resistance of
Figure 796954DEST_PATH_IMAGE017
；
Determining the A (A) of the distribution transformer according to the calculation of the parameters (capacity Se (KVA), high-voltage side voltage Ue (kV) and short-circuit voltage ratio Uk%) of the medium-voltage distribution transformer<50 Reactance at HZ
Figure 13172DEST_PATH_IMAGE018
Ohm;
the impedance angle setting calculation formula is as follows:
Figure 895677DEST_PATH_IMAGE019
；
calculating the load line A (A) based on the load line length L3, the reactance value x3 per unit length, and the resistance value r3 per unit length<50 Reactance at HZ
Figure 513740DEST_PATH_IMAGE020
Ohm; resistance (RC)
Figure 721868DEST_PATH_IMAGE021
Ohm;
according to load apparent power S (VA) and power factor
Figure 428311DEST_PATH_IMAGE022
Calculating to determine the load at A (A)<50 Reactance at HZ
Figure 380087DEST_PATH_IMAGE023
Ohm; resistance (RC)
Figure 852656DEST_PATH_IMAGE024
Ohm;
load side power factor angle
Figure 966106DEST_PATH_IMAGE025
；
Determining the impedance angle setting value
Figure 156916DEST_PATH_IMAGE026
Angle with said load side power factor
Figure 646803DEST_PATH_IMAGE027
Satisfy the requirement of
Figure 239458DEST_PATH_IMAGE028
Wherein
Figure 523809DEST_PATH_IMAGE029
Is the sensitivity factor;
in this embodiment: impedance of medium voltage line: the model of the medium-voltage 10kV line is LG-95, the reactance x1 per kilometer is 0.342 ohm, and the resistance r1 per kilometer is 0.33 ohm; the power supply distance L1 is 10 km.
Figure 936336DEST_PATH_IMAGE030
The resistance of the ohmic resistor is high,
Figure 229914DEST_PATH_IMAGE031
ohm; (line model data from the distribution network project of the national grid company is typicalDesign 10kV overhead line sublist, impedance data from the electrical engineering electrical primary design manual).
Impedance of the distribution transformer: the distribution transformer parameters were: se =400kVA, transformation ratio of 10.5kV/0.4kV, uk% =4, and reactance value reduced to 10kV side is
Figure 677076DEST_PATH_IMAGE032
Ohm.
The impedance angle setting value is as follows:
Figure 397907DEST_PATH_IMAGE033
sensitivity coefficient of
Figure 297730DEST_PATH_IMAGE029
=1.5；
Impedance condition of low-voltage load transmission line: the model of the low-voltage line is jklyj-1/70, the resistance r3 of the low-voltage line is 0.443 ohm/km, the reactance x3 of the low-voltage line is 0.335 ohm/km, and the power supply distance is 100m.
Figure 129420DEST_PATH_IMAGE034
The resistance of the ohmic resistor is high,
Figure 696667DEST_PATH_IMAGE035
ohm;
the loading of the platform area is 150KVA, the power factor angle is 0.85,
Figure 588400DEST_PATH_IMAGE036
ohm;
Figure 975519DEST_PATH_IMAGE037
ohm;
Figure 345320DEST_PATH_IMAGE038
；
Figure 767075DEST_PATH_IMAGE039
Figure 829708DEST_PATH_IMAGE029
the sensitivity requirement is met.
Optionally, the low-frequency voltage current phase angle difference is used
Figure 704124DEST_PATH_IMAGE040
And the impedance angle setting value
Figure 877616DEST_PATH_IMAGE041
Making a comparison and when the impedance angle is set
Figure 888297DEST_PATH_IMAGE041
Phase angle difference with the voltage and current
Figure 121832DEST_PATH_IMAGE042
When a certain proportional relation is satisfied, the judging system is in an island operation state, and a tripping command of the photovoltaic grid-connected circuit breaker is sent to the platform region fusion terminal, and the method comprises the following steps:
when it is satisfied with
Figure 483544DEST_PATH_IMAGE043
And when the system is in an island operation state, the trip command is sent to the transformer area fusion terminal, and all distributed photovoltaic grid-connected circuit breakers of the transformer area are tripped through the fusion terminal.
In this embodiment, when the platform area is operated in a grid-connected mode,
Figure 460727DEST_PATH_IMAGE044
if the anti-islanding protection action condition is not met, the anti-islanding protection does not act; when the transformer area is operated in an island mode, according to the calculation,
Figure 591494DEST_PATH_IMAGE045
Figure 995931DEST_PATH_IMAGE029
and the anti-islanding protection action condition is met, and at the moment, an anti-islanding protection tripping command is givenAnd sending the information to the fusion terminal, and tripping off all distributed photovoltaic grid-connected breakers of the transformer area through the fusion terminal.
According to another aspect of the present invention, there is also provided a low-frequency injection anti-islanding protection system 300 for a multi-photovoltaic-connected platform, referring to fig. 2 and 3, the system 300 includes:
a voltage/current phase angle difference monitoring module 310, configured to inject a low-frequency small power supply and a band-pass filtering unit into a low-voltage bus of a distribution substation, and monitor the low-frequency voltage/current phase angle difference through the voltage/current phase angle difference monitoring unit
Figure 579359DEST_PATH_IMAGE046
；
The impedance angle setting value and load side power factor angle determining module 320 is used for determining an impedance angle setting value according to system parameters; determining a load side power factor angle according to the load parameter; confirming that the impedance angle setting value and the load side power factor angle meet a certain proportional relation;
and the island operation state judging module 330 is configured to compare the voltage-current phase angle difference with the impedance angle setting value, and when the impedance angle setting value and the voltage-current phase angle difference satisfy a certain proportional relationship, judge that the system is in an island operation state, and send a trip command of the photovoltaic grid-connected circuit breaker to the station area convergence terminal.
Optionally, the voltage-current phase angle difference monitoring module includes:
the low-frequency power supply injection unit is used for injecting a low-frequency small power supply with the frequency lower than 50HZ, and the low-frequency small power supply can be a voltage source or a current source;
the band-pass filtering unit is used for acquiring signals of a low-frequency band and shielding signals of other frequency bands;
a voltage and current phase angle difference monitoring unit for monitoring the phase angle difference of low frequency voltage and current
Figure 360233DEST_PATH_IMAGE047
。
Optionally, the impedance angle setting value and load-side power factor angle determining module includes:
the impedance angle setting value calculation unit is used for calculating and determining reactance X1 and resistance R1 values of the medium-voltage system line under low frequency according to the length and model parameters of the medium-voltage line; calculating and determining a reactance X2 value of the distribution transformer under low frequency according to parameters of the medium-voltage distribution transformer; determining an impedance angle setting value according to the reactance X1 and the resistance R1 of the medium-voltage system line and the reactance X2 of the distribution transformer
Figure 345506DEST_PATH_IMAGE048
。
Optionally, the impedance angle setting value and load-side power factor angle determining module includes:
the load side power factor angle calculation unit is used for calculating and determining reactance X3 and resistance R3 values of the load line under low frequency according to the length and the model of the load line; according to the load size and the power factor, calculating and determining equivalent reactance X4 and resistance R4 values of the load under low frequency; calculating the power factor angle of the load side of the transformer area according to X3, R3, X4 and R4
Figure 920844DEST_PATH_IMAGE049
。
Optionally, the impedance angle setting value and load-side power factor angle determining module includes:
a sensitivity verification unit for verifying the impedance angle setting value
Figure 257148DEST_PATH_IMAGE050
Angle with said load side power factor
Figure 576133DEST_PATH_IMAGE051
Satisfy the requirement of
Figure 415914DEST_PATH_IMAGE052
In which
Figure 162153DEST_PATH_IMAGE053
Is the sensitivity factor;
optionally, the islanding operation state determining module includes:
an island operation state discrimination unit for comparing the impedance angle setting value
Figure 985752DEST_PATH_IMAGE054
Phase angle difference with low frequency voltage current
Figure 842850DEST_PATH_IMAGE055
When the relationship of (1) is satisfied
Figure 805645DEST_PATH_IMAGE056
Judging to be in isolated island operation;
optionally, the islanding operation state determining module includes:
and the tripping circuit breaker unit trips all distributed photovoltaic grid-connected circuit breakers of the transformer area through the fusion terminal when the island operation state is judged.
The low-frequency injection type anti-islanding protection system 300 of the multi-channel photovoltaic access platform area in the embodiment of the present invention corresponds to the low-frequency injection type anti-islanding protection method 100 of the multi-channel photovoltaic access platform area in another embodiment of the present invention, and details thereof are not repeated herein.
According to a third aspect of the present invention, there is provided the storage medium storing a computer program for executing the method of any one of the above.
As will be appreciated by one skilled in the art, 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. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims (10)

1. A low-frequency injection type anti-islanding protection method for a multi-channel photovoltaic accessed transformer area is characterized by comprising the following steps:
injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a distribution substation area to monitor the phase angle difference of low-frequency voltage and current
Figure 451890DEST_PATH_IMAGE001
The low-frequency small power supply is a sine wave with the frequency below the standard 50 HZ;
determining an impedance angle setting value according to system parameters
Figure 677072DEST_PATH_IMAGE002
Determining the load-side power factor angle according to the load parameter
Figure 372496DEST_PATH_IMAGE003
The impedance angle setting value
Figure 614121DEST_PATH_IMAGE004
Angle with said load side power factor
Figure 92507DEST_PATH_IMAGE005
Need to satisfy
Figure 1558DEST_PATH_IMAGE006
In which
Figure 539986DEST_PATH_IMAGE007
Is the sensitivity coefficient;
the phase angle difference of the low-frequency voltage and the current
Figure 534487DEST_PATH_IMAGE008
And the impedance angle setting value
Figure 816564DEST_PATH_IMAGE002
Making a comparison when the conditions are satisfied
Figure 580121DEST_PATH_IMAGE009
And when the system is in an island operation state, jumping off all distributed photovoltaic grid-connected circuit breakers of the transformer area through the fusion terminal.
2. Method according to claim 1, characterized in that the low-frequency voltage current phase angle difference is monitored by injecting a low-frequency small power supply and a band-pass filtering unit at the distribution substation low-voltage bus
Figure 351767DEST_PATH_IMAGE001
The method comprises the following steps:
determining a low-frequency small power supply to be a sine wave with a frequency below a standard 50HZ, wherein the low-frequency small power supply can be a voltage source or a current source;
collecting signals of a low-frequency band through a band-pass filtering unit and shielding signals of other frequency bands;
monitoring the phase angle difference of the low-frequency voltage and the current
Figure 505668DEST_PATH_IMAGE001
。
3. The method of claim 1, wherein the impedance angle setting is determined based on system parameters
Figure 653753DEST_PATH_IMAGE002
The method comprises the following steps:
calculating and determining reactance X1 and resistance R1 values of the medium-voltage system line under low frequency according to the length and model parameters of the medium-voltage line;
calculating and determining a reactance X2 value of the distribution transformer under low frequency according to parameters of the medium-voltage distribution transformer;
determining an impedance angle setting value according to the reactance X1 and the resistance R1 of the medium-voltage system line and the reactance X2 of the distribution transformer
Figure 209499DEST_PATH_IMAGE010
。
4. Method according to claim 1, characterized in that the load-side power factor angle is determined from the load parameter
Figure 152047DEST_PATH_IMAGE011
The method comprises the following steps:
calculating and determining reactance X3 and resistance R3 values of a load side line under low frequency according to the length and the model of the load line;
according to the load size and the power factor, calculating and determining equivalent reactance X4 and resistance R4 values of the load under low frequency;
calculating the power factor angle of the load side of the transformer area according to X3, R3, X4 and R4
Figure 855561DEST_PATH_IMAGE003
。
5. The utility model provides a low frequency injection formula anti-island protection system of platform district of multichannel photovoltaic access which characterized in that includes:
the voltage and current phase angle difference monitoring module is used for injecting a low-frequency small power supply and a band-pass filtering unit at a low-voltage bus of a power distribution station area and monitoring the low-frequency voltage and current phase angle difference through the voltage and current phase angle difference monitoring unit
Figure 479440DEST_PATH_IMAGE012
The low-frequency small power supply is a sine wave with the frequency below the standard 50 HZ;
an impedance angle setting value and load side power factor angle determination module for determining the impedance angle setting value according to the system parameters
Figure 217589DEST_PATH_IMAGE013
Determining the load-side power factor angle according to the load parameter
Figure 331039DEST_PATH_IMAGE014
The setting value of the impedance angle
Figure 459532DEST_PATH_IMAGE004
Angle with said load side power factor
Figure 949419DEST_PATH_IMAGE005
Need to satisfy
Figure 718573DEST_PATH_IMAGE006
Wherein
Figure 268503DEST_PATH_IMAGE007
Is the sensitivity factor;
an island operation state discrimination module for discriminating the phase angle difference of the low-frequency voltage and current
Figure 884292DEST_PATH_IMAGE012
And the impedance angle setting value
Figure 912291DEST_PATH_IMAGE015
Making a comparison when the conditions are satisfied
Figure 359453DEST_PATH_IMAGE009
And when the system is in an island operation state, jumping off all distributed photovoltaic grid-connected circuit breakers of the transformer area through the fusion terminal.
6. The system of claim 5, wherein the voltage-current phase angle difference monitoring module comprises:
the low-frequency power supply injection unit is used for injecting a low-frequency small power supply with the frequency lower than 50HZ, and the low-frequency small power supply can be a voltage source or a current source;
the band-pass filtering unit is used for acquiring signals of a low-frequency band and shielding signals of other frequency bands;
a voltage and current phase angle difference monitoring unit for monitoring the phase angle difference of low frequency voltage and current
Figure 752388DEST_PATH_IMAGE016
。
7. The system of claim 5, wherein the impedance angle setting and load-side power factor angle determination module comprises:
the impedance angle setting value calculation unit is used for calculating and determining reactance X1 and resistance R1 values of the medium-voltage system line under low frequency according to the length and model parameters of the medium-voltage line; calculating and determining a reactance X2 value of the distribution transformer under low frequency according to parameters of the medium-voltage distribution transformer; determining an impedance angle setting value according to the reactance X1 and the resistance R1 of the medium-voltage system line and the reactance X2 of the distribution transformer
Figure 917790DEST_PATH_IMAGE017
。
8. The system of claim 5, wherein the impedance angle setting and load-side power factor angle determination module comprises:
the load side power factor angle calculation unit is used for calculating and determining reactance X3 and resistance R3 values of the load line under low frequency according to the length and the model of the load line; according to the load size and the power factor, calculating and determining equivalent reactance X4 and resistance R4 values of the load under low frequency; calculating a power factor angle of a load side of the transformer area according to X3, R3, X4 and R4
Figure 483901DEST_PATH_IMAGE018
。
9. The system of claim 5, wherein the islanding operating state discrimination module comprises:
and the tripping photovoltaic grid-connected circuit breaker unit is used for sending a tripping command of the photovoltaic grid-connected circuit breaker to the platform region fusion terminal when the system is judged to be in an island operation state.
10. A computer-readable storage medium, characterized in that the storage medium stores a computer program for performing the method of any of the preceding claims 1-4.
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