CN113285430B - Direct current arc detection method, energy conversion equipment and power generation system - Google Patents
Direct current arc detection method, energy conversion equipment and power generation system Download PDFInfo
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- CN113285430B CN113285430B CN202110631487.3A CN202110631487A CN113285430B CN 113285430 B CN113285430 B CN 113285430B CN 202110631487 A CN202110631487 A CN 202110631487A CN 113285430 B CN113285430 B CN 113285430B
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- 238000001514 detection method Methods 0.000 title claims abstract description 60
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 38
- 238000010248 power generation Methods 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000004146 energy storage Methods 0.000 claims description 46
- 230000002457 bidirectional effect Effects 0.000 claims description 32
- 230000008033 biological extinction Effects 0.000 claims description 32
- 239000003990 capacitor Substances 0.000 claims description 18
- 238000010586 diagram Methods 0.000 description 4
- 238000012423 maintenance Methods 0.000 description 4
- 230000003111 delayed effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- 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
- H02H3/02—Details
- H02H3/06—Details with automatic reconnection
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- 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
- H02H3/08—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 responsive to excess current
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
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- Engineering & Computer Science (AREA)
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Inverter Devices (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The application discloses a direct current arc detection method, energy conversion equipment and a power generation system, which are used for improving the accuracy of direct current arc detection. The method comprises the following steps: when the direct current arc detection circuit judges that a direct current arc is generated on the direct current line, starting arc extinguishing operation; after delaying the preset time, releasing the arc extinguishing operation; and judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free.
Description
Technical Field
The present invention relates to the field of power electronics, and more particularly, to a direct current arc detection method, an energy conversion device, and a power generation system.
Background
In power generation systems (such as photovoltaic power generation systems, photovoltaic hybrid power generation systems and the like), direct-current arc caused by loosening, aging, poor contact and the like of a direct-current wiring terminal is one of key factors affecting the safe operation of the system. The working principle of the direct current arc detection circuit is as follows: the method comprises the steps of sampling alternating current harmonic waves on a direct current line by using a current transformer, obtaining an FFT (Fast Fourier Transform ) value through a series of processes, and if the FFT value exceeds a preset value T1, confirming that the state of the direct current line accords with the characteristics of direct current arc, and directly judging that the direct current arc is generated on the direct current line.
However, other factors in the system (such as ac interference generated at the moment when the load on the ac side of the inverter circuit is switched in/out is coupled to the dc line) may cause ac harmonics to be generated on the dc line, and the FFT value obtained by a series of processing of the ac harmonics exceeds the preset value T1, and the dc arc detection circuit may have misjudgment.
Disclosure of Invention
In view of the above, the present invention provides a direct current arc detection method, an energy conversion device, and a power generation system to improve the accuracy of direct current arc detection.
A method of dc arc detection comprising:
when the direct current arc detection circuit judges that a direct current arc is generated on the direct current line, starting arc extinguishing operation;
After delaying the preset time, releasing the arc extinguishing operation;
And judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free.
Optionally, the judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released includes:
Acquiring a current value on the direct current line, judging whether the current value is lower than a preset current value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released;
or obtaining the power value of the direct current line, judging whether the power value is lower than a preset power value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released;
or acquiring a fast Fourier transform FFT value output by the direct current arc detection circuit, judging whether the FFT value is lower than a preset FFT value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released.
Optionally, the starting the arc extinguishing operation includes: the current value on the direct current line is reduced to the arc extinction threshold value.
Optionally, when the energy conversion device connected to the current line is loaded, the reducing the current value on the current line to the arc extinction threshold includes:
On the premise of coordinating power supply of other lines so as to ensure uninterrupted power supply of the load, the current value of the direct current line is reduced to an arc extinction threshold value.
Optionally, on the direct current line, the energy storage battery is connected to the direct current side of the inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit;
On the premise of coordinating power supply of other lines to ensure uninterrupted power supply of loads, the current value on the direct current line is reduced to an arc extinction threshold value, and the method comprises the following steps: on the premise of coordinating the other types of power supplies and the power grid to supply power so as to ensure uninterrupted power supply of loads, the charge and discharge currents of the energy storage batteries are reduced to arc extinction threshold values by controlling the bidirectional DC/DC converter and/or a battery management system BMS in the energy storage batteries.
Optionally, the controlling the bidirectional DC/DC converter and/or the BMS in the energy storage battery to reduce the charge/discharge current of the energy storage battery to the extinction threshold includes:
and controlling the bidirectional DC/DC converter and/or the BMS in the energy storage battery to cut off the direct current line.
Optionally, the bidirectional DC/DC converter includes: the switching circuit comprises an inductor L, a first switching tube T1, a second switching tube T2, an input capacitor C1 and an output capacitor C2;
The positive electrode of the input capacitor C1 is connected with the electric energy input end of the first switching tube T1 and the electric energy output end of the second switching tube T2 through the inductor L, the electric energy output end of the first switching tube T1 is connected with the negative electrode of the input capacitor C1 and the negative electrode of the output capacitor C2, and the electric energy input end of the second switching tube T2 is connected with the positive electrode of the output capacitor C2;
The method for controlling the bidirectional DC/DC converter to cut off the direct current line comprises the following steps: stopping wave generation to the first switching tube T1 when the energy storage battery is charged; and stopping wave generation to the second switching tube T2 when the energy storage battery discharges.
Optionally, on the direct current line, the energy storage battery is connected to the direct current side of the inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit; the direct current line is also connected in series with a controllable switch;
On the premise of coordinating power supply of other lines to ensure uninterrupted power supply of loads, the current value on the direct current line is reduced to an arc extinction threshold value, and the method comprises the following steps: and on the premise of coordinating the other types of power supplies and the power grid power supply so as to ensure uninterrupted power supply of the load, the controllable switch is controlled to be disconnected.
An energy conversion apparatus, comprising: a control unit and an energy conversion circuit with a DC arc detection circuit;
The control unit is used for starting arc extinguishing operation when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit; after delaying the preset time, releasing the arc extinguishing operation; and judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free.
Optionally, the control unit is specifically configured to implement an arc extinguishing operation by reducing a current value on the current direct-current line to an arc extinguishing threshold value.
Optionally, when the energy conversion device is loaded, the control unit is specifically configured to reduce the current value on the dc line to the arc extinction threshold under the premise of coordinating power supply on other lines to ensure uninterrupted power supply of the load.
Optionally, the energy conversion device comprises a bidirectional DC/DC converter and an inverter circuit; on the direct current line, the energy storage battery is connected to the direct current side of the inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit;
The control unit is specifically used for controlling the BMS circuit and/or the bidirectional DC/DC converter to reduce the charge and discharge current value of the energy storage battery to an arc extinction threshold value on the premise of coordinating other types of power supplies and power grid power supply so as to ensure uninterrupted power supply of the load, thereby completing the step of starting the arc extinction operation.
Optionally, on the direct current line, the energy storage battery is connected to the direct current side of the inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit; the direct current line is also connected in series with a controllable switch;
The control unit is specifically used for switching off the controllable switch on the premise of coordinating the power supply of other types of power sources and the power grid to ensure uninterrupted power supply of the load, so that the step of starting the arc extinguishing operation is completed.
Optionally, the other type of power source is photovoltaic, and correspondingly, the energy conversion device is a light storage inverter.
A power generation system, comprising: any of the energy conversion devices disclosed above, and one or more dc power sources connected to the energy conversion device.
From the above technical solution, it can be seen that the present invention uses the characteristic that the dc arc cannot be re-ignited after being extinguished, when the dc arc detection circuit determines that the dc arc is generated on the dc line, starts the arc extinguishing operation, and releases the arc extinguishing operation after a predetermined time is delayed, if the dc arc does not exist after the arc extinguishing operation is released, it indicates that the dc arc is actually generated before, otherwise, it indicates that the dc arc is misjudged due to the interference, and the dc arc is not actually generated before.
Drawings
In order to more clearly illustrate the embodiments of the invention 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, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for detecting a DC arc according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a hybrid power generation system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a hybrid power system according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing the specific configuration of the bi-directional DC/DC converter and the AC switching circuit in the system of FIG. 2;
Fig. 5 shows a schematic diagram of a specific configuration of the bidirectional DC/DC converter and the ac switching circuit in the system shown in fig. 3.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. 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.
Referring to fig. 1, an embodiment of the invention discloses a direct current arc detection method, which comprises the following steps:
Step S01: when the dc arc detection circuit determines that a dc arc is generated on the dc line, the arc extinguishing operation is started, and the process proceeds to step S02.
Specifically, when a break point occurs on the dc line, if the electric field strength of the break point gap is greater than the breakdown strength of air, the air in the break point gap will break down to generate a group of gas which has extremely high temperature, emits strong light and can be conductive and is approximately cylindrical, which is the dc arc. The current flows through the direct current circuit due to the conductive characteristic of the direct current arc until the direct current arc is extinguished, the air in the gap at the break point is recovered to an insulating state, the current is disconnected, and the direct current arc cannot be re-combusted after being extinguished.
The direct current arc burns, and alternating current harmonic waves are injected into the direct current line, which is one of the characteristics of the direct current arc. When the direct current arc detection circuit detects that alternating current harmonic wave is generated on the direct current line and the FFT value obtained by a series of processing of the alternating current harmonic wave exceeds a preset value T1, the state of the direct current line is confirmed to accord with the direct current arc characteristic, and the direct current arc is directly judged to be generated on the direct current line. After the direct current arc is generated, the arc extinguishing operation needs to be started immediately, so that the direct current arc is extinguished (the arc extinguishing operation can be that the current value on the direct current line is reduced to an arc extinguishing threshold value which is equal to or slightly larger than zero), further expansion of the situation is avoided, an alarm is sent out, and maintenance personnel can timely arrive at the field for maintenance after receiving the alarm. However, some interference factors in the system may make the state of the direct current line conform to the direct current arc characteristic, but in fact, no direct current arc is generated on the direct current line, and at this time, misjudgment occurs in the direct current arc detection circuit, so that maintenance personnel return without work, time of the maintenance personnel is wasted, and normal operation of the system is delayed.
It is necessary to verify the judgment result of the dc arc detection circuit to improve the accuracy of dc arc detection. In the embodiment of the invention, after the direct current arc detection circuit judges that the direct current arc is generated on the direct current line, the arc extinguishing operation is started in time so as to prevent alarming once in case, but the alarm is sent out after the direct current arc detection circuit is verified to judge that the direct current arc detection circuit is correct.
Step S02: after a predetermined delay time, the arc extinguishing operation is released, and the process proceeds to step S03.
Step S03: judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, if not, entering step S04; if yes, go to step S05.
Step S04: and judging that the direct current arc detection circuit has misjudgment, and ending the control of the current wheel.
Step S05: and judging that the direct current arc detection circuit judges that the direct current arc detection circuit is correct until the control of the current round is finished.
Specifically, the embodiment of the invention uses the characteristic that the direct current arc cannot be re-burned after being extinguished to check the judgment result of the direct current arc detection circuit, and if the direct current arc does not exist after the extinction operation is released, the direct current circuit shows an open-circuit fault, which indicates that the direct current arc is actually generated before, and the judgment of the direct current arc detection circuit is correct; conversely, it is indicated that there is a disturbance that leads to a misjudgment that no dc arc has actually been generated previously.
Before the direct current arc is extinguished, the direct current circuit is a passage, and the FFT value output by the direct current arc detection circuit exceeds a preset value T1; after the direct current arc is extinguished, the direct current line shows an open circuit fault, the current and the power on the direct current line are reduced to zero, and the FFT value output by the direct current arc detection circuit is reduced to zero. Based on this, in the step S03, it may be determined whether the current line is in the open state after the arc extinguishing operation is released: and acquiring a current value on the direct current line, judging whether the current value is lower than a preset current value, and if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released. Or may also be: and acquiring the power value of the direct current line, judging whether the power value is lower than a preset power value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released. Or may also be: and acquiring an FFT value output by the direct current arc detection circuit, judging whether the FFT value is lower than a preset FFT value, and if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released.
In theory, the preset current value, the preset power value, and the preset FFT value may be set to zero, but considering the existence of the measurement errors of the current value, the power value, and the FFT value, it is recommended to set the preset current value, the preset power value, and the preset FFT value to a value slightly greater than zero.
The direct current arc detection method can be applied to any power generation system, such as a photovoltaic power generation system, a light-storage hybrid power generation system and the like. However, when the energy conversion equipment in the power generation system is loaded, the continuous power supply of the load needs to be ensured in best effort when the arc extinguishing operation is performed on the direct current line. That is, when the energy conversion device connected to the current line is loaded, the reducing the current value on the current line to the arc extinction threshold specifically includes: on the premise of coordinating power supply of other lines so as to ensure uninterrupted power supply of the load, the current value of the direct current line is reduced to an arc extinction threshold value.
For example, in a power generation system in which an energy storage battery is mixed with other types of power sources, the energy conversion device often hangs a load, and when arc extinguishing operation is performed on a direct current line in which the energy storage battery is located, efforts are made to ensure uninterrupted power supply of the load. Specifically, the energy conversion device comprises a bidirectional DC/DC converter and an inverter circuit; the energy storage battery is connected to the direct current side of the inverter circuit through the bidirectional DC/DC converter, the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected to the power grid and the load through the alternating current switch circuit, for example, as shown in fig. 2. The current transformer in the dc arc detection circuit is denoted by CT in fig. 2. In fig. 2, for the dc line where the energy storage battery is located, the reducing the current value on the dc line to the extinction threshold includes: and on the premise of coordinating the other types of power supplies and the power grid power supply to ensure uninterrupted power supply of a load, the charging and discharging currents of the energy storage Battery are reduced to an arc extinction threshold value by controlling the bidirectional DC/DC converter and/or a BMS (Battery MANAGEMENT SYSTEM) in the energy storage Battery.
Optionally, for the power generation system shown in fig. 2, the charge and discharge current of the energy storage battery is reduced to an arc extinction threshold, and the simplest implementation manner is to cut off the dc line, so that the charge and discharge current of the energy storage battery is reduced to zero, and the implementation manner may be that: controlling the bi-directional DC/DC converter and/or the BMS in the energy storage battery to cut off the direct current circuit; or in the case that a controllable switch K0 is further connected in series to the present dc line, as shown in fig. 3, the controllable switch K0 may be controlled to be turned off so as to cut off the present dc line. Fig. 3 only exemplifies that the controllable switch K0 is connected in series between the energy storage battery and the bidirectional DC/DC converter, but the controllable switch K0 may also be connected in series between the bidirectional DC/DC converter and the inverter circuit, which is not limited.
Alternatively, the bidirectional DC/DC converter in fig. 2 or 3 may employ a circuit topology (see fig. 4 based on fig. 2 or fig. 5 based on fig. 3) including: the switching circuit comprises an inductor L, a first switching tube T1, a second switching tube T2, an input capacitor C1 and an output capacitor C2;
the positive electrode of the input capacitor C1 is connected with the electric energy input end of the first switch tube T1 and the electric energy output end of the second switch tube T2 through the inductor L, the electric energy output end of the first switch tube T1 is connected with the negative electrode of the input capacitor C1 and the negative electrode of the output capacitor C2, and the electric energy input end of the second switch tube T2 is connected with the positive electrode of the output capacitor C2.
At this time, controlling the bidirectional DC/DC converter to cut off the direct current line includes: stopping wave generation to the first switching tube T1 when the energy storage battery is charged; and stopping wave generation to the second switching tube T2 when the energy storage battery discharges.
Alternatively, still referring to fig. 4 or 5, the ac switching circuit includes, for example, a switch K1 and a switch K2, where one end of the switch K1 is connected to the ac side of the inverter circuit, the other end is connected to the load and one end of the switch K2, and the other end of the switch K2 is connected to the power grid.
Taking the other types of power sources as photovoltaic as an example, the photovoltaic power supply priority is higher than the energy storage battery power supply priority, and the energy storage battery power supply priority is higher than the power grid power supply priority. Assuming that the illumination is sufficient at the current moment, the energy storage battery is in a charging state, and K1 is conducted and K2 is disconnected, the scheme for carrying out direct current arc detection on the direct current circuit where the energy storage battery is located can be as follows: stopping generating waves to the first switching tube T1 when the direct current arc detection circuit judges that the direct current arc is generated on the direct current line; after a preset time interval, recovering normal wave generation of the first switching tube T1; after the normal transmission of the first switching tube T1 is restored, if the direct current circuit is in an open circuit state, the direct current arc detection circuit is indicated to judge that the direct current arc detection circuit is correct, the arc extinguishing operation is started at the moment, the alarm is given, otherwise, the interference is determined, and the system continues to normally operate. Or assuming that the current moment is night moment, the energy storage battery is in a discharging working condition, and K1 is conducted and K2 is disconnected, the scheme for carrying out direct current arc detection on the direct current circuit where the energy storage battery is located can be as follows: when the direct current arc detection circuit judges that a direct current arc is generated on the direct current circuit, K2 is closed firstly, and then wave generation to the second switching tube T2 is stopped; after a preset time interval, recovering normal wave generation of the second switching tube T2; after the second switching tube T2 is recovered to normally send out, if the direct current circuit is in an open circuit state, the direct current arc detection circuit is indicated to judge that the direct current arc detection circuit is correct, the arc extinguishing operation is started at the moment, the alarm is given, otherwise, the interference is determined, the system continues to normally operate, and the K2 is disconnected.
Corresponding to the method embodiment, the embodiment of the invention also discloses energy conversion equipment which comprises a control unit and an energy conversion circuit with a direct current arc detection circuit;
The control unit is used for starting arc extinguishing operation when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit; after delaying the preset time, releasing the arc extinguishing operation; and judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free.
Optionally, the control unit is specifically configured to obtain a current value on the current line, determine whether the current value is lower than a preset current value, and if so, determine that the current line is in an open circuit state after the arc extinguishing operation is released. Or the control unit is specifically configured to obtain a power value on the current line, determine whether the power value is lower than a preset power value, and if yes, determine that the current line is in an open circuit state after the arc extinguishing operation is released. Or the control unit is specifically configured to obtain the FFT value output by the dc arc detection circuit, determine whether the FFT value is lower than a preset FFT value, if yes, determine that the dc line is in an open state after the arc extinguishing operation is released.
Optionally, in any embodiment of the disclosure above, the control unit starts an arc extinguishing operation, including: the current value on the direct current line is reduced to the arc extinction threshold value.
Optionally, when the energy conversion device is loaded, the control unit is specifically configured to reduce the current value on the dc line to the arc extinction threshold under the premise of coordinating power supply on other lines to ensure uninterrupted power supply of the load.
Optionally, the energy conversion device comprises a bidirectional DC/DC converter and an inverter circuit; on the direct current line, the energy storage battery is connected to the direct current side of the inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load;
The control unit is specifically used for controlling the BMS circuit and/or the bidirectional DC/DC converter to reduce the charge and discharge current value of the energy storage battery to an arc extinction threshold value on the premise of coordinating other types of power supplies and power grid power supply so as to ensure uninterrupted power supply of the load, thereby completing the step of starting the arc extinction operation.
In addition, when a controllable switch is further connected in series on the DC line (the controllable switch may be connected in series between the energy storage battery and the bidirectional DC/DC converter, or may also be connected in series between the bidirectional DC/DC converter and the inverter circuit), the control unit may also be configured to disconnect the controllable switch on the premise of coordinating the other types of power sources and the power grid to supply power so as to ensure uninterrupted power supply to the load, thereby completing the step of starting the arc extinguishing operation.
In any of the above embodiments, the other type of power source may be photovoltaic or wind energy, and when the other type of power source is photovoltaic, the energy conversion device is a photovoltaic inverter.
In addition, the embodiment of the invention also discloses a power generation system, which comprises: any of the energy conversion devices disclosed above, and one or more dc power sources connected to the energy conversion device. When the direct current side of the energy conversion equipment is connected with the energy storage battery and the photovoltaic at the same time, the power generation system is a light storage hybrid power generation system.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The terms first, second and the like in the description and in the claims and in the above-described figures, are used for distinguishing between similar different objects and not necessarily for describing a particular sequential or chronological order. 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" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. 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 embodiments of the invention. Thus, the present embodiments are 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 (14)
1. A method of detecting a direct current arc, comprising:
when the direct current arc detection circuit judges that a direct current arc is generated on the direct current line, starting arc extinguishing operation;
After delaying the preset time, releasing the arc extinguishing operation;
judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free;
Wherein, judge whether this direct current circuit is the state of breaking circuit after the arc extinguishing operation is released, include:
Acquiring a current value on the direct current line, judging whether the current value is lower than a preset current value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released;
or obtaining the power value of the direct current line, judging whether the power value is lower than a preset power value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released;
or acquiring a fast Fourier transform FFT value output by the direct current arc detection circuit, judging whether the FFT value is lower than a preset FFT value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released.
2. The direct current arc detection method according to claim 1, wherein the starting the arc extinguishing operation includes: the current value on the direct current line is reduced to the arc extinction threshold value.
3. The method according to claim 2, wherein when the energy conversion device connected to the current line is loaded, the step of reducing the current value on the current line to the extinction threshold value includes:
On the premise of coordinating power supply of other lines so as to ensure uninterrupted power supply of the load, the current value of the direct current line is reduced to an arc extinction threshold value.
4. The method for detecting a direct current arc according to claim 3, wherein on the present direct current line, the energy storage battery is connected to the direct current side of the inverter circuit via a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit;
On the premise of coordinating power supply of other lines to ensure uninterrupted power supply of loads, the current value on the direct current line is reduced to an arc extinction threshold value, and the method comprises the following steps: on the premise of coordinating the other types of power supplies and the power grid to supply power so as to ensure uninterrupted power supply of loads, the charge and discharge currents of the energy storage batteries are reduced to arc extinction threshold values by controlling the bidirectional DC/DC converter and/or a battery management system BMS in the energy storage batteries.
5. The direct current arc detection method according to claim 4, wherein the reducing the charge and discharge current of the energy storage battery to the extinction threshold by controlling the bidirectional DC/DC converter and/or the BMS in the energy storage battery comprises:
and controlling the bidirectional DC/DC converter and/or the BMS in the energy storage battery to cut off the direct current line.
6. The direct current arc detection method of claim 5, wherein the bi-directional DC/DC converter comprises: the switching circuit comprises an inductor L, a first switching tube T1, a second switching tube T2, an input capacitor C1 and an output capacitor C2;
The positive electrode of the input capacitor C1 is connected with the electric energy input end of the first switching tube T1 and the electric energy output end of the second switching tube T2 through the inductor L, the electric energy output end of the first switching tube T1 is connected with the negative electrode of the input capacitor C1 and the negative electrode of the output capacitor C2, and the electric energy input end of the second switching tube T2 is connected with the positive electrode of the output capacitor C2;
The method for controlling the bidirectional DC/DC converter to cut off the direct current line comprises the following steps: stopping wave generation to the first switching tube T1 when the energy storage battery is charged; and stopping wave generation to the second switching tube T2 when the energy storage battery discharges.
7. The method for detecting a direct current arc according to claim 3, wherein on the present direct current line, the energy storage battery is connected to the direct current side of the inverter circuit via a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit; the direct current line is also connected in series with a controllable switch;
On the premise of coordinating power supply of other lines to ensure uninterrupted power supply of loads, the current value on the direct current line is reduced to an arc extinction threshold value, and the method comprises the following steps: and on the premise of coordinating the other types of power supplies and the power grid power supply so as to ensure uninterrupted power supply of the load, the controllable switch is controlled to be disconnected.
8. An energy conversion device, comprising: a control unit and an energy conversion circuit with a DC arc detection circuit;
The control unit is used for starting arc extinguishing operation when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit; after delaying the preset time, releasing the arc extinguishing operation; judging whether the direct current circuit is in an open circuit state after the arc extinguishing operation is released, if so, judging that the direct current arc detection circuit judges that the direct current circuit is error-free; wherein, judge whether this direct current circuit is the state of breaking circuit after the arc extinguishing operation is released, include: acquiring a current value on the direct current line, judging whether the current value is lower than a preset current value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released; or obtaining the power value of the direct current line, judging whether the power value is lower than a preset power value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released; or acquiring a fast Fourier transform FFT value output by the direct current arc detection circuit, judging whether the FFT value is lower than a preset FFT value, if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is released.
9. The energy conversion device according to claim 8, wherein the control unit is specifically configured to implement an arc extinction operation by reducing the current value on the present dc line to an arc extinction threshold value.
10. The energy conversion device according to claim 9, wherein the control unit is configured to reduce the current value on the dc link to the extinction threshold value, when the energy conversion device is loaded, in particular, while coordinating power supply on other links to ensure uninterrupted power supply of the load.
11. The energy conversion device of claim 10, wherein the energy conversion device comprises a bi-directional DC/DC converter and an inverter circuit; on the direct current line, an energy storage battery is connected to the direct current side of an inverter circuit through a bidirectional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit;
The control unit is specifically used for controlling the BMS circuit and/or the bidirectional DC/DC converter to reduce the charge and discharge current value of the energy storage battery to an arc extinction threshold value on the premise of coordinating other types of power supplies and power grid power supply so as to ensure uninterrupted power supply of the load, thereby completing the step of starting the arc extinction operation.
12. The energy conversion device according to claim 10, wherein on the present DC line, the energy storage battery is connected to the DC side of the inverter circuit via a bi-directional DC/DC converter; the direct current side of the inverter circuit is also connected with other types of power supplies, and the alternating current side of the inverter circuit is connected with a power grid and a load through an alternating current switch circuit; the direct current line is also connected in series with a controllable switch;
The control unit is specifically used for switching off the controllable switch on the premise of coordinating the power supply of other types of power sources and the power grid to ensure uninterrupted power supply of the load, so that the step of starting the arc extinguishing operation is completed.
13. The energy conversion device according to claim 11 or 12, wherein the other type of power source is photovoltaic and the energy conversion device is a photovoltaic inverter.
14. A power generation system, comprising: the energy conversion device of any one of claims 8-13, and one or more direct current power sources connected to the energy conversion device.
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| CN114755542B (en) * | 2022-04-21 | 2024-02-09 | 阳光电源股份有限公司 | Arc fault detection method, device and equipment |
| CN116068346A (en) * | 2023-02-16 | 2023-05-05 | 固德威技术股份有限公司 | Arc fault confirmation method, device and medium |
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