CN116565816A - Protection method and protection system for arc faults of high-voltage direct-current line - Google Patents
Protection method and protection system for arc faults of high-voltage direct-current line Download PDFInfo
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- CN116565816A CN116565816A CN202310622051.7A CN202310622051A CN116565816A CN 116565816 A CN116565816 A CN 116565816A CN 202310622051 A CN202310622051 A CN 202310622051A CN 116565816 A CN116565816 A CN 116565816A
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000003745 diagnosis Methods 0.000 claims abstract description 33
- 238000006243 chemical reaction Methods 0.000 claims abstract description 31
- 230000009471 action Effects 0.000 claims abstract description 22
- 238000004891 communication Methods 0.000 claims abstract description 16
- 238000001914 filtration Methods 0.000 claims description 12
- 238000001228 spectrum Methods 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 230000000977 initiatory effect Effects 0.000 claims 1
- 238000010891 electric arc Methods 0.000 abstract description 4
- 238000002955 isolation Methods 0.000 abstract description 3
- 230000008569 process Effects 0.000 abstract description 3
- 238000012545 processing Methods 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 description 3
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Classifications
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- 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
- H02H7/268—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 for dc systems
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- 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
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/262—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 involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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- Photovoltaic Devices (AREA)
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Abstract
A protection method and protection system of arc fault of high-voltage direct current line, it is the safe equipment field of photovoltaic power station, pass the current signal of direct current side of the photovoltaic inverter current/voltage signal conversion at first, get the voltage signal, and filter and process, keep the harmonic amplitude higher than the frequency range signal of the set point, compare and judge with the electric arc frequency domain characteristic, get the diagnostic result; according to the diagnosis result, a protection action starting instruction is formulated, and faults are removed; the invention only keeps the frequency with obvious direct current arc characteristics, and the formulated protection action starting instruction is more reliable by combining the time domain characteristics of direct current, thereby avoiding the occurrence of protection misoperation and refusal action; the protection system provided by the invention adopts a string protection scheme, so that the string position of the arc fault can be accurately positioned, and the rapidity and the accuracy of arc fault processing are improved; finally, the communication assembly with the isolation function is adopted in the protection system, so that the interference of the external environment to the protection system is avoided.
Description
Technical Field
The invention relates to the field of photovoltaic power station safety equipment, in particular to a protection method and a protection system for arc faults of a high-voltage direct-current line.
Background
With the continuous development of renewable energy power generation, the installed capacity of photovoltaic power generation is improved year by year, but simultaneously, higher requirements are put on the safety of the photovoltaic power generation. The high-voltage direct current circuit is formed by a plurality of electrical equipment among the photovoltaic modules in a serial connection mode, generally reaches about 1000V, and can reach 1500V at most, even if the system is stopped, the high-voltage direct current circuit still exists about kilovolts in the photovoltaic module matrix, if the conditions of contact drop, device aging, insulation rupture, poor grounding and the like of the electrical equipment occur, electric arcs can be generated, electric fires occur, safety accidents occur, serious losses are caused to the economic level of a power generator, and electric shock risks also exist for operation and maintenance personnel in daily power station operation and maintenance or property maintenance.
Because direct current arc generation is the most common fault phenomenon in a photovoltaic power station and has extremely high hazard, and it is important to prevent electric arcs from occurring in electrical equipment between photovoltaic modules, a reliable and sensitive direct current line protection method for the photovoltaic power station is needed to detect and timely cut off the electric arcs occurring in the photovoltaic power station.
Disclosure of Invention
In order to solve the problems, the invention provides a protection method and a protection system for arc faults of a high-voltage direct-current line.
A method of protecting against arc faults in a high voltage direct current line, the method comprising:
step one: collecting current signals of a direct current side of the photovoltaic inverter in real time, and converting the current signals into voltage signals through current/voltage signal conversion;
step two: filtering the voltage signal, reserving a frequency range signal with harmonic amplitude higher than a set value, and comparing and judging with the arc frequency domain characteristics to obtain a diagnosis result;
step three: formulating a protection action starting instruction according to the diagnosis result, and cutting off faults according to the protection action starting instruction;
preferably, the collecting the current signal of the direct current side of the photovoltaic inverter in real time, converting the current signal through current/voltage signal to obtain a voltage signal, includes:
collecting current signals of the direct current side of the photovoltaic inverter in real time, and reducing the current signals according to a set proportion; performing current/voltage signal conversion on the reduced current signal to obtain a small voltage signal; and amplifying the small voltage signal to a set receiving range to obtain a voltage signal.
Preferably, the filtering the voltage signal, retaining a frequency range signal with a harmonic amplitude higher than a set value, and comparing and judging with the arc frequency domain feature to obtain a diagnosis result, including:
acquiring a frequency spectrum in the voltage signal and filtering to obtain a frequency range signal with a harmonic amplitude higher than a set value, wherein the frequency range signal is an analog quantity signal; performing digital-to-analog conversion on the frequency range signal to obtain a digital quantity signal; and carrying out Fourier transform on the digital quantity signal to obtain a signal frequency domain characteristic, and comparing the signal frequency domain characteristic with an arc frequency domain characteristic to obtain a diagnosis result.
Preferably, the step of formulating a protection action starting instruction according to the diagnosis result further includes:
acquiring a current value of a direct current side of a photovoltaic grid-connected inverter in real time, and acquiring the fluctuation quantity of the current value; judging whether the fluctuation amount is in a set fluctuation range or not to obtain an auxiliary diagnosis result; and based on the diagnosis result and the auxiliary diagnosis result, formulating a protection action starting instruction.
A protection system for a high voltage direct current line arc fault, the protection system comprising: the device comprises a current transformer, a conversion circuit, an amplifying circuit, a band-pass filter circuit, a control processor and a switch circuit;
the current transformer is arranged on the direct current side of the external photovoltaic grid-connected inverter, and the collected current signals are transmitted to the conversion circuit to be subjected to current/voltage signal conversion; the amplifying circuit is connected with the converting circuit and amplifies the signal from the converting circuit to obtain a voltage signal with the signal amplitude within a set receiving range; the amplifying circuit is connected with the band-pass filter circuit, filters the voltage signal, retains a frequency range signal with harmonic amplitude higher than a set value and transmits the frequency range signal to the control processor; the control processor performs analog-to-digital conversion on the frequency range signal, obtains signal frequency domain characteristics through Fourier transformation, compares the signal frequency domain characteristics with arc frequency characteristics to obtain a diagnosis result, formulates a protection action starting instruction, and controls the starting and stopping of the arc breaker through a switch circuit.
Preferably, the band-pass filter circuit is connected in series by using a multi-stage operational amplifier circuit.
Preferably, the protection system further comprises: the first RS485 communication chip; the first RS485 communication chip is arranged between the control processor and the switch circuit and is used for isolating the interference of an external high-voltage environment.
Preferably, the protection system further comprises: the Hall sensor and the second RS485 communication chip; the Hall sensor is used for acquiring a current value of a direct current side of the photovoltaic grid-connected inverter in real time, and transmitting the current value to the control processor through the second RS485 communication chip to formulate an auxiliary diagnosis result.
Preferably, the protection system further comprises: the wireless circuit, the alarm indicator lamp and the alarm sound;
the wireless circuit is used for sending an alarm signal to external terminal equipment; the alarm indicator lamp and the alarm sound are used for giving out alarm indication when arc faults occur.
Compared with the prior art, the invention has the beneficial effects that:
the technical scheme provided by the invention comprises the following steps: collecting current signals of a direct current side of the photovoltaic inverter in real time, and converting the current signals into voltage signals through current/voltage signal conversion; filtering the voltage signal, reserving a frequency range signal with harmonic amplitude higher than a set value, and comparing and judging with the arc frequency domain characteristics to obtain a diagnosis result; formulating a protection action starting instruction according to the diagnosis result, and cutting off faults according to the protection action starting instruction; the invention collects the frequency domain characteristic parameters of the direct current, only retains the frequency with obvious direct current arc characteristics through filtering treatment, has the advantage of high detection efficiency, and combines the time domain characteristics of the direct current to make a protection action starting instruction more reliable, thereby improving the detection accuracy and further avoiding the occurrence of protection misoperation and refusal operation; the protection system provided by the invention adopts a string protection scheme, so that the string position of the arc fault can be accurately positioned, the rapidity and the accuracy of arc fault treatment are improved, and the normal operation of other photovoltaic modules is not influenced; finally, the protection system provided by the invention adopts the communication assembly with the isolation function, so that the interference of the external environment to the protection system is avoided.
Drawings
FIG. 1 is a flow chart of a method for protecting a high voltage DC line from arc faults in the present invention;
fig. 2 is a diagram of the protection system for arc faults of the high voltage direct current line in the present invention.
Detailed Description
For a better understanding of the present invention, reference is made to the following description, drawings and examples.
Embodiment one:
the embodiment provides a protection method for arc faults of a high-voltage direct-current line, and a flow chart of the protection method is shown in fig. 1, and comprises the following steps:
step one: collecting current signals of a direct current side of the photovoltaic inverter in real time, and converting the current signals into voltage signals through current/voltage signal conversion;
step two: filtering the voltage signal to filter useless frequency signals and other interference signals, reserving frequency range signals with harmonic amplitude higher than a set value, and comparing and judging with the electric arc frequency domain characteristics to obtain a diagnosis result; the purpose of the filtering process is to increase the decision to determine whether a dc arc is generated or not and to avoid false alarm events due to environmental factor changes.
Step three: formulating a protection action starting instruction according to the diagnosis result, and cutting off faults according to the protection action starting instruction;
the real-time collection photovoltaic inverter DC side current signal, with current signal through current/voltage signal conversion, obtain voltage signal, include:
collecting current signals of the direct current side of the photovoltaic inverter in real time, and reducing the current signals according to a set proportion;
performing current/voltage signal conversion on the reduced current signal to obtain a small voltage signal;
and amplifying the small voltage signal to a set receiving range to obtain a voltage signal.
The voltage quantity signal is filtered, a frequency range signal with harmonic amplitude higher than a set value is reserved, and the frequency range signal is compared with the arc frequency domain characteristics to obtain a diagnosis result, and the method comprises the following steps:
acquiring a frequency spectrum in the voltage signal and filtering to obtain a frequency range signal with a harmonic amplitude higher than a set value, wherein the frequency range signal is an analog quantity signal;
performing digital-to-analog conversion on the frequency range signal to obtain a digital quantity signal;
and carrying out Fourier transform on the digital quantity signal to obtain a signal frequency domain characteristic, and comparing the signal frequency domain characteristic with an arc frequency domain characteristic to obtain a diagnosis result.
And according to the diagnosis result, formulating a protection action starting instruction, wherein the method further comprises the following steps:
acquiring a current value of a direct current side of a photovoltaic grid-connected inverter in real time, and acquiring the fluctuation quantity of the current value; judging whether the fluctuation amount is in a set fluctuation range or not to obtain an auxiliary diagnosis result;
based on the diagnosis result and the auxiliary diagnosis result, a protection action starting instruction is formulated, and the occurrence condition of the electric arc is judged together by monitoring the fluctuation of the direct current value in real time and combining the fluctuation of the frequency domain, so that the judgment accuracy of the occurrence of the electric arc is improved.
Embodiment two:
the embodiment provides a protection system for arc faults of a high-voltage direct-current line, the constitution diagram of the protection system is shown in fig. 2, the protection system in the invention adopts a string protection scheme, the string position of the arc faults can be accurately positioned, the rapidity and the accuracy of arc fault processing are improved, the work of other normal photovoltaic strings is not influenced, and only the current fault string is processed. The protection system includes: the device comprises a current transformer, a conversion circuit, an amplifying circuit, a band-pass filter circuit, a control processor and a switch circuit; the current transformer is arranged on the direct current side of the external photovoltaic grid-connected inverter, and the collected current signals are transmitted to the conversion circuit to be subjected to current/voltage signal conversion; the amplifying circuit is connected with the converting circuit and amplifies the signal from the converting circuit to obtain a voltage signal with the signal amplitude within a set receiving range; the amplifying circuit is connected with the band-pass filtering circuit, filters the voltage signal, filters useless frequency signals and other interference signals, only keeps the frequency range signals with harmonic amplitude higher than a set value and transmits the frequency range signals to the control processor, so that the judging accuracy of the direct current arc is improved, and false alarm events caused by environmental factor changes are avoided; the purpose of the amplifying circuit is to amplify the small voltage signal to a voltage within a normal receiving range of the control processor; and the control processor performs analog-to-digital conversion on the frequency range signal, obtains a signal frequency domain characteristic through Fourier transformation, compares the signal frequency domain characteristic with an arc frequency characteristic to obtain a diagnosis result, formulates a protection action starting instruction, and controls the starting and stopping of the direct current arc breaker through a switch circuit. Because the control processor processes digital signals, analog-to-digital conversion needs to be performed on the frequency range signals, in this embodiment, an external analog-to-digital conversion circuit may also be used to perform analog-to-digital conversion processing, and the control processor itself has an analog-to-digital conversion function, and selects one of the two analog-to-digital conversion functions, where the chip accuracy and the type of the external analog-to-digital conversion circuit are adaptively selected according to specific settings. In addition, in order to prevent the arc generated in the breaker at the moment of the switching action, the arc breaker has an arc extinguishing function when being designed.
In addition, the protection system provided in this embodiment further includes a voltage level conversion circuit, as shown in R2, R3 and R4 in fig. 2, which is used to convert the 5V voltage signal into a 3.3V voltage signal that can be received by the control processor, specifically, whether the voltage level or the converted voltage value needs to be converted, and according to a specific design, the invention is also applicable to protection in a design scheme that does not need to convert the voltage level or convert the voltage level into other voltage values.
The control processor is also in communication connection with the photovoltaic inverter equipment, and when the control processor is connected, an RS485 communication chip with an isolation function is adopted in order to prevent external equipment from interfering the protection system.
The band-pass filter circuit is connected in series by adopting a multi-stage operational amplifier circuit.
Based on the purpose of preventing interference, the protection system further comprises: the first RS485 communication chip; the first RS485 communication chip is arranged between the control processor and the switch circuit and is used for isolating the interference of an external high-voltage environment.
The protection system further comprises: the Hall sensor and the second RS485 communication chip; the Hall sensor is used for acquiring a current value of a direct current side of the photovoltaic grid-connected inverter in real time, and transmitting the current value to the control processor through the second RS485 communication chip to formulate an auxiliary diagnosis result.
The protection system further includes: the wireless circuit is used as a sending module of the alarm signal and is transmitted to the terminal for display; the alarm indicator lamp and the alarm sound are used as alarm signals when arc faults occur; environmental sensors for detecting external environments, including but not limited to light, temperature, humidity, and the like.
It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (9)
1. A method for protecting an arc fault of a high voltage direct current line, the method comprising:
step one: collecting current signals of a direct current side of the photovoltaic inverter in real time, and converting the current signals into voltage signals through current/voltage signal conversion;
step two: filtering the voltage signal, reserving a frequency range signal with harmonic amplitude higher than a set value, and comparing and judging with the arc frequency domain characteristics to obtain a diagnosis result;
step three: and formulating a protection action starting instruction according to the diagnosis result, and cutting off faults according to the protection action starting instruction.
2. The method for protecting an arc fault of a high voltage direct current line according to claim 1, wherein the collecting the current signal of the direct current side of the photovoltaic inverter in real time, converting the current signal into a voltage signal through current/voltage signal, comprises:
collecting current signals of the direct current side of the photovoltaic inverter in real time, and reducing the current signals according to a set proportion; performing current/voltage signal conversion on the reduced current signal to obtain a small voltage signal; and amplifying the small voltage signal to a set receiving range to obtain a voltage signal.
3. The method for protecting an arc fault of a high voltage direct current line according to claim 1, wherein the filtering the voltage magnitude signal, retaining a frequency range signal with a harmonic amplitude higher than a set value, comparing and judging with an arc frequency domain feature to obtain a diagnosis result, comprises:
acquiring a frequency spectrum in the voltage signal and filtering to obtain a frequency range signal with a harmonic amplitude higher than a set value, wherein the frequency range signal is an analog quantity signal; performing digital-to-analog conversion on the frequency range signal to obtain a digital quantity signal; and carrying out Fourier transform on the digital quantity signal to obtain a signal frequency domain characteristic, and comparing the signal frequency domain characteristic with an arc frequency domain characteristic to obtain a diagnosis result.
4. The method for protecting an arc fault of a high voltage direct current circuit according to claim 3, wherein said formulating a protection action initiation command according to said diagnosis result, further comprises:
acquiring a current value of a direct current side of a photovoltaic grid-connected inverter in real time, and acquiring the fluctuation quantity of the current value; judging whether the fluctuation amount is in a set fluctuation range or not to obtain an auxiliary diagnosis result; and based on the diagnosis result and the auxiliary diagnosis result, formulating a protection action starting instruction.
5. A protection system for a high voltage direct current line arc fault, the protection system comprising: the device comprises a current transformer, a conversion circuit, an amplifying circuit, a band-pass filter circuit, a control processor and a switch circuit;
the current transformer is arranged on the direct current side of the external photovoltaic grid-connected inverter, and the collected current signals are transmitted to the conversion circuit to be subjected to current/voltage signal conversion; the amplifying circuit is connected with the converting circuit and amplifies the signal from the converting circuit to obtain a voltage signal with the signal amplitude within a set receiving range; the amplifying circuit is connected with the band-pass filter circuit, filters the voltage signal, retains a frequency range signal with harmonic amplitude higher than a set value and transmits the frequency range signal to the control processor; the control processor performs analog-to-digital conversion on the frequency range signal, obtains signal frequency domain characteristics through Fourier transformation, compares the signal frequency domain characteristics with arc frequency characteristics to obtain a diagnosis result, formulates a protection action starting instruction, and controls the starting and stopping of the arc breaker through a switch circuit.
6. The system of claim 5, wherein the band-pass filter circuit is a multi-stage operational amplifier circuit in series.
7. The protection system for a hvdc line arc fault in accordance with claim 5, further comprising: the first RS485 communication chip; the first RS485 communication chip is arranged between the control processor and the switch circuit and is used for isolating the interference of an external high-voltage environment.
8. The protection system for a hvdc line arc fault in accordance with claim 5, further comprising: the Hall sensor and the second RS485 communication chip;
the Hall sensor is used for acquiring a current value of a direct current side of the photovoltaic grid-connected inverter in real time, and transmitting the current value to the control processor through the second RS485 communication chip to formulate an auxiliary diagnosis result.
9. The protection system for a hvdc line arc fault in accordance with claim 5, further comprising: the wireless circuit, the alarm indicator lamp and the alarm sound;
the wireless circuit is used for sending an alarm signal to external terminal equipment; the alarm indicator lamp and the alarm sound are used for giving out alarm indication when arc faults occur.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310622051.7A CN116565816A (en) | 2023-05-29 | 2023-05-29 | Protection method and protection system for arc faults of high-voltage direct-current line |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310622051.7A CN116565816A (en) | 2023-05-29 | 2023-05-29 | Protection method and protection system for arc faults of high-voltage direct-current line |
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| CN116565816A true CN116565816A (en) | 2023-08-08 |
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| CN202310622051.7A Pending CN116565816A (en) | 2023-05-29 | 2023-05-29 | Protection method and protection system for arc faults of high-voltage direct-current line |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117148049A (en) * | 2023-10-31 | 2023-12-01 | 锦浪科技股份有限公司 | Direct current arc discharge fault detection system, method and photovoltaic grid-connected system |
-
2023
- 2023-05-29 CN CN202310622051.7A patent/CN116565816A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117148049A (en) * | 2023-10-31 | 2023-12-01 | 锦浪科技股份有限公司 | Direct current arc discharge fault detection system, method and photovoltaic grid-connected system |
| CN117148049B (en) * | 2023-10-31 | 2024-01-26 | 锦浪科技股份有限公司 | Direct current arc discharge fault detection system, method and photovoltaic grid-connected system |
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