CN113285430A - 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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- CN113285430A CN113285430A CN202110631487.3A CN202110631487A CN113285430A CN 113285430 A CN113285430 A CN 113285430A CN 202110631487 A CN202110631487 A CN 202110631487A CN 113285430 A CN113285430 A CN 113285430A
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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 21
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000004146 energy storage Methods 0.000 claims description 46
- 230000002457 bidirectional effect Effects 0.000 claims description 37
- 239000003990 capacitor Substances 0.000 claims description 18
- 238000007599 discharging Methods 0.000 claims description 10
- 230000008033 biological extinction Effects 0.000 claims description 7
- 230000000977 initiatory effect Effects 0.000 claims 1
- 238000010586 diagram Methods 0.000 description 4
- 238000012423 maintenance Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 3
- 230000032683 aging Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
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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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Abstract
The application discloses a direct current arc detection method, energy conversion equipment and a power generation system, which aim to improve the accuracy of direct current arc detection. The method comprises the following steps: when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit, arc extinguishing operation is started; releasing the arc extinguishing operation after delaying the preset time; and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a direct current arc detection method, energy conversion equipment and a power generation system.
Background
In a power generation system (such as a photovoltaic power generation system, a light storage hybrid power generation system, and the like), a direct current arc caused by loosening, aging, poor contact and the like of a direct current terminal is one of the key factors influencing the safe operation of the system. The working principle of the direct current arc detection circuit is as follows: 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 processing, confirming that the state of the direct current line accords with the direct current arc characteristics if the FFT value exceeds a preset value T1, and directly judging that the direct current arc is generated on the direct current line.
However, other factors in the system (for example, ac interference generated at the moment of switching in/out the load on the ac side of the inverter circuit is coupled to the dc line) may also cause ac harmonics to be generated on the dc line, and an FFT value obtained by performing a series of processing on the ac harmonics exceeds the preset value T1, at which time the dc arc detection circuit makes an erroneous judgment.
Disclosure of Invention
In view of this, the present invention provides a dc arc detection method, an energy conversion device and a power generation system, so as to improve the accuracy of dc arc detection.
A method of dc arc detection comprising:
when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit, arc extinguishing operation is started;
releasing the arc extinguishing operation after delaying the preset time;
and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
Optionally, judge whether this direct current line is the open circuit state after the arc extinguishing operation is relieved, include:
acquiring a current value on the current line, judging whether the current value is lower than a preset current value or not, and if so, judging that the current line is in an open circuit state after arc extinguishing operation is removed;
or acquiring a power value on the current direct current line, judging whether the power value is lower than a preset power value, and if so, judging that the current direct current line is in an open circuit state after arc extinguishing operation is removed;
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, and if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is removed.
Optionally, the starting of the arc extinguishing operation includes: and reducing the current value on the direct current line 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 extinguishing threshold includes:
on the premise of coordinating power supply of power supplies on other lines so as to ensure uninterrupted power supply of a load, the current value on the direct current line is reduced to the arc extinction threshold value.
Optionally, on the direct current 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 with a power grid and a load through an alternating current switch circuit;
thereby coordinating the power supply on other circuits and guaranteeing under the incessant power supply's of load prerequisite, make the current value on this direct current circuit reduce the arc extinguishing threshold value, include: and on the premise of coordinating the power supplies of other types of power supplies and a power grid so as to ensure that the load supplies power uninterruptedly, the charging and discharging current of the energy storage battery is reduced to an arc extinguishing threshold value by controlling the bidirectional DC/DC converter and/or a battery management system BMS in the energy storage battery.
Optionally, the reducing the charging and discharging current of the energy storage battery to the arc extinguishing threshold by controlling the bidirectional DC/DC converter and/or the BMS in the energy storage battery 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 inductor L, the first switch tube T1, the second switch tube T2, the input capacitor C1 and the output capacitor C2;
the positive electrode of the input capacitor C1 is connected with the power input end of the first switch tube T1 and the power output end of the second switch tube T2 through the inductor L, the power 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 power input end of the second switch tube T2 is connected with the positive electrode of the output capacitor C2;
controlling the bidirectional DC/DC converter to cut off the current direct current line comprises the following steps: when the energy storage battery is charged, wave emission to the first switching tube T1 is stopped; when the energy storage battery is discharged, the wave sending to the second switch tube T2 is stopped.
Optionally, on the direct current 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 with a power grid and a load through an alternating current switch circuit; the direct current line is also connected with a controllable switch in series;
thereby coordinating the power supply on other circuits and guaranteeing under the incessant power supply's of load prerequisite, make the current value on this direct current circuit reduce the arc extinguishing threshold value, include: and on the premise of coordinating the power supplies of the other types of power supplies and the power grid so as to ensure that the load supplies power uninterruptedly, the controllable switch is controlled to be switched off.
An energy conversion apparatus, comprising: the control unit and the energy conversion circuit with the direct current arc detection circuit;
the control unit is used for starting arc extinguishing operation when the direct current arc detection circuit judges that direct current arc is generated on a direct current line; releasing the arc extinguishing operation after delaying the preset time; and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
Optionally, the control unit is specifically configured to implement an arc extinguishing operation by reducing a current value on the current line to an arc extinguishing threshold.
Optionally, when the energy conversion device is in a load state, the control unit is specifically configured to reduce the current value on the current line to an arc extinguishing threshold value on the premise of coordinating power supply on other lines to ensure uninterrupted power supply of the load.
Optionally, the energy conversion device includes a bidirectional DC/DC converter and an inverter circuit; on the direct current 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 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 charging and discharging current value of the energy storage battery to an arc extinguishing threshold value on the premise of coordinating power supplies of other types of power supplies and a power grid so as to guarantee uninterrupted power supply of a load, so that the step of starting arc extinguishing operation is completed.
Optionally, on the direct current 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 with a power grid and a load through an alternating current switch circuit; the direct current line is also connected with a controllable switch in series;
and the control unit is specifically used for disconnecting the controllable switch on the premise of coordinating the power supplies of the other types of power supplies and the power grid so as to ensure that the load supplies power uninterruptedly, thereby completing the step of starting arc extinguishing operation.
Optionally, the other type of power source is a photovoltaic, and correspondingly, the energy conversion device is a light storage inverter.
A power generation system, comprising: any one of the energy conversion devices disclosed above, and one or more dc power sources connected to the energy conversion devices.
According to the technical scheme, the characteristic that the direct-current arc cannot be reignited after being extinguished is utilized, when 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, the arc extinguishing operation is released after the preset time is delayed, if the arc extinguishing operation is released, the direct-current line shows an open circuit fault due to the fact that the direct-current arc is not generated, the fact that the direct-current arc is generated actually in the prior art is indicated, and otherwise, the fact that the direct-current arc is generated due to interference is indicated, and the fact that the direct-current arc is not generated in the prior art is actually determined.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a DC arc detection method according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a hybrid power generation system according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another hybrid power generation system disclosed in the embodiment of the present invention;
FIG. 4 is a schematic diagram showing the specific structure of the bidirectional DC/DC converter and AC switch circuit in the system of FIG. 2;
fig. 5 is a schematic diagram showing a specific structure of the bidirectional DC/DC converter and the ac switching circuit in the system shown in fig. 3.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, an embodiment of the present invention discloses a method for detecting a dc arc, including:
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 then the process proceeds to step S02.
Specifically, when a break point occurs on the dc line, if the electric field intensity of the break point gap is greater than the breakdown strength of air, the air in the break point gap is broken down, and a cylindrical gas which has a very high temperature, emits strong light, and can conduct electricity is generated, which is a dc arc. The current on the direct current line still flows due to the conductive characteristic of the direct current arc, until the direct current arc is extinguished, the air in the gap of the break point is restored to the insulation state, the current is disconnected, and the direct current arc cannot be reignited after being extinguished.
When the direct current arc burns, 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 waves are generated on the direct current line and an FFT value obtained by a series of processing of the alternating current harmonic waves exceeds a preset value T1, the direct current arc detection circuit confirms that the state of the direct current line accords with the direct current arc characteristics, and directly judges that direct current arcs are generated on the direct current line. After the direct current arc is generated, arc extinguishing operation needs to be started immediately so as to extinguish the direct current arc (the arc extinguishing operation can be, for example, to reduce the current value on the direct current line to an arc extinguishing threshold value, and the arc extinguishing threshold value is equal to or slightly larger than zero), so that the situation is prevented from being further enlarged, an alarm is sent, and maintenance personnel can timely arrive at the site for maintenance after receiving the alarm. However, some interference factors in the system may also cause the state of the current dc line to conform to the dc arc characteristic, and actually, no dc arc is generated on the current dc line, so that the dc arc detection circuit may make an erroneous judgment, which causes a maintenance staff to return without work, wastes time of the maintenance staff and delays the normal operation of the system.
It is therefore necessary to verify the judgment result of the dc arc detection circuit to improve the accuracy of dc arc detection. According to the embodiment of the invention, after the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit, the arc extinguishing operation is started in time so as to prevent the alarm from happening, but the alarm is not given out temporarily, and the alarm is given out only when the direct current arc detection circuit is checked out to judge that the direct current arc detection circuit is correct.
Step S02: the arc extinguishing operation is released after a delay for a preset time, and then 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 removed, and if not, entering the step S04; if yes, the process proceeds to step S05.
Step S04: and judging that the DC arc detection circuit has misjudgment, and ending the control of the current round.
Step S05: and judging that the direct current arc detection circuit judges no error, and ending the control in the current round.
Specifically, the embodiment of the invention utilizes the characteristic that the direct current arc cannot be reignited after being extinguished to check the judgment result of the direct current arc detection circuit, if the arc extinguishing operation is released, the direct current circuit shows an open circuit fault because the direct current arc does not exist, which indicates that the direct current arc is actually generated before, the direct current arc detection circuit judges that no error exists; otherwise, it indicates that the interference causes misjudgment, and actually, no direct current arc is generated before.
Before the direct current arc is extinguished, a direct current line is a path, 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 also reduced to zero. Based on this, in step S03, it is determined whether the current dc line is in the open circuit state after the arc extinguishing operation is released, and the determination may be: and acquiring a current value on the current line, judging whether the current value is lower than a preset current value, and if so, judging that the current line is in an open circuit state after the arc extinguishing operation is released. Alternatively, it may be: and acquiring a power value on the current direct current line, judging whether the power value is lower than a preset power value, and if so, judging that the current direct current line is in an open circuit state after arc extinguishing operation is removed. Alternatively, it may be: and acquiring the 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 removed.
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 error 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 larger 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 device in the power generation system is loaded, an effort is made to ensure that the load is continuously supplied when the arc extinguishing operation is performed on the direct current line. That is to say, 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 arc extinguishing threshold specifically includes: on the premise of coordinating power supply of power supplies on other lines so as to ensure uninterrupted power supply of a load, the current value on the direct current line is reduced to the 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, a load is often hung on an energy conversion device, and when an arc extinguishing operation is performed on a direct current line in which the energy storage battery is located, an effort is made to ensure that the load supplies power uninterruptedly. Specifically, the energy conversion equipment 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 to other types of power sources, and the alternating current side of the inverter circuit is connected to a power grid and a 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 current line to the arc extinguishing threshold includes: on the premise of coordinating the power supply of the other types of power sources and the power grid so as to ensure that the load supplies power uninterruptedly, the charging and discharging current of the energy storage Battery is reduced to an arc extinguishing threshold value by controlling the bidirectional DC/DC converter and/or a Battery Management System (BMS) in the energy storage Battery.
Optionally, for the power generation system shown in fig. 2, the charging and discharging current of the energy storage battery is reduced to an arc extinguishing threshold, and the simplest implementation manner is to cut off the current line, so that the charging and discharging current of the energy storage battery is reduced to zero, and the implementation manner may be: controlling the bidirectional DC/DC converter and/or a BMS in the energy storage battery to cut off the direct current line; or, in the case that a controllable switch K0 is also connected in series to the current dc line, as shown in fig. 3, the controllable switch K0 may be controlled to be turned off to cut off the current dc line. Fig. 3 only illustrates that the controllable switch K0 is connected in series between the energy storage battery and the bidirectional DC/DC converter, and besides, 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 fig. 3 may employ the following circuit topology (see fig. 4 obtained based on fig. 2, or fig. 5 obtained based on fig. 3), including: the inductor L, the first switch tube T1, the second switch tube T2, the input capacitor C1 and the output capacitor C2;
the positive pole of the input capacitor C1 is connected to the power input end of the first switch tube T1 and the power output end of the second switch tube T2 through the inductor L, the power output end of the first switch tube T1 is connected to the negative pole of the input capacitor C1 and the negative pole of the output capacitor C2, and the power input end of the second switch tube T2 is connected to the positive pole of the output capacitor C2.
In this case, the controlling the bidirectional DC/DC converter to cut off the current DC link includes: when the energy storage battery is charged, wave emission to the first switching tube T1 is stopped; when the energy storage battery is discharged, the wave sending to the second switch tube T2 is stopped.
Optionally, still referring to fig. 4 or 5, the ac switching circuit includes, for example, a switch K1 and a switch K2, the switch K1 is connected to the ac side of the inverter circuit at one end, 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 the photovoltaic, 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 present moment, the energy storage battery is in a charging state, K1 is turned on, and K2 is turned off, the scheme for performing dc arc detection on the dc line where the energy storage battery is located may be: when the direct current arc detection circuit judges that the direct current arc is generated on the direct current line, stopping sending waves to the first switching tube T1; the first switch tube T1 is recovered to generate wave normally after a preset time interval; if the direct current line is in an open circuit state after the first switching tube T1 is recovered to be normally sent, the direct current arc detection circuit judges that the direct current arc detection circuit is correct, at the moment, arc extinguishing operation is started and an alarm is given, otherwise, the system is judged to be in interference, and the system continues to normally operate. Or, if the current time is night time, the energy storage battery is in a discharge working condition, K1 is turned on, and K2 is turned off, then the scheme for performing dc arc detection on the dc line where the energy storage battery is located may be: when the direct current arc detection circuit judges that the direct current arc is generated on the direct current line, K2 is closed firstly, and then wave sending to the second switch tube T2 is stopped; the second switch tube T2 is recovered to generate wave normally after a preset time interval; if the direct current line is in an open circuit state after the second switching tube T2 is recovered to be normally sent, the direct current arc detection circuit judges that the direct current arc detection circuit is correct, at the moment, arc extinguishing operation is started and an alarm is given, otherwise, the system is judged to be in interference, the system continues to normally operate, and the K2 is disconnected.
Corresponding to the embodiment of the method, 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 direct current arc is generated on a direct current line; releasing the arc extinguishing operation after delaying the preset time; and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
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 dc line, determine whether the power value is lower than a preset power value, and if so, determine that the current dc line is in an open circuit state after the arc extinguishing operation is released. Or the control unit is specifically configured to obtain an FFT value output by the dc arc detection circuit, determine whether the FFT value is lower than a preset FFT value, and if so, determine that the current dc line is in an open circuit state after the arc extinguishing operation is released.
Optionally, in any embodiment disclosed above, the control unit initiates an arc extinguishing operation, including: and reducing the current value on the direct current line to the arc extinction threshold value.
Optionally, when the energy conversion device is in a load state, the control unit is specifically configured to reduce the current value on the current line to an arc extinguishing threshold value on the premise of coordinating power supply on other lines to ensure uninterrupted power supply of the load.
Optionally, the energy conversion device includes a bidirectional DC/DC converter and an inverter circuit; on the direct current 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 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 charging and discharging current value of the energy storage battery to an arc extinguishing threshold value on the premise of coordinating power supplies of other types of power supplies and a power grid so as to guarantee uninterrupted power supply of a load, so that the step of starting arc extinguishing operation is completed.
In addition, when a controllable switch (which may be connected in series between the energy storage battery and the bidirectional DC/DC converter or between the bidirectional DC/DC converter and the inverter circuit) is also connected in series on the current DC line, the control unit may also be configured to disconnect the controllable switch on the premise of coordinating the power supplies of the other types of power supplies and the power grid to ensure that the load supplies power uninterruptedly, so as to complete 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 light storage inverter.
In addition, the embodiment of the invention also discloses a power generation system, which comprises: any one of the energy conversion devices disclosed above, and one or more dc power sources connected to the energy conversion devices. 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.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The terms "first," "second," and the like in the description and in the claims, and in the drawings, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. Also, 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, the use of the verb "comprise a" to define an element does not exclude the presence of another, identical element in a process, method, article, or apparatus that comprises the 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. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (15)
1. A method of detecting a dc arc, comprising:
when the direct current arc detection circuit judges that the direct current arc is generated on the direct current circuit, arc extinguishing operation is started;
releasing the arc extinguishing operation after delaying the preset time;
and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
2. The method of claim 1, wherein the determining whether the dc link is in an open circuit state after the arc extinguishing operation is released comprises:
acquiring a current value on the current line, judging whether the current value is lower than a preset current value or not, and if so, judging that the current line is in an open circuit state after arc extinguishing operation is removed;
or acquiring a power value on the current direct current line, judging whether the power value is lower than a preset power value, and if so, judging that the current direct current line is in an open circuit state after arc extinguishing operation is removed;
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, and if so, judging that the direct current line is in an open circuit state after the arc extinguishing operation is removed.
3. The direct current arc detection method of claim 1, wherein the initiating an arc extinguishing operation comprises: and reducing the current value on the direct current line to the arc extinction threshold value.
4. The method according to claim 3, wherein the reducing the current value on the current line to the arc extinguishing threshold when the energy conversion device connected to the current line is loaded comprises:
on the premise of coordinating power supply of power supplies on other lines so as to ensure uninterrupted power supply of a load, the current value on the direct current line is reduced to the arc extinction threshold value.
5. The direct-current arc detection method according to claim 4, wherein on the current direct-current line, an 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;
thereby coordinating the power supply on other circuits and guaranteeing under the incessant power supply's of load prerequisite, make the current value on this direct current circuit reduce the arc extinguishing threshold value, include: and on the premise of coordinating the power supplies of other types of power supplies and a power grid so as to ensure that the load supplies power uninterruptedly, the charging and discharging current of the energy storage battery is reduced to an arc extinguishing threshold value by controlling the bidirectional DC/DC converter and/or a battery management system BMS in the energy storage battery.
6. The method according to claim 5, wherein the step of reducing the charging/discharging current of the energy storage battery to an arc extinguishing 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.
7. The direct current arc detection method of claim 6, wherein the bidirectional DC/DC converter comprises: the inductor L, the first switch tube T1, the second switch tube T2, the input capacitor C1 and the output capacitor C2;
the positive electrode of the input capacitor C1 is connected with the power input end of the first switch tube T1 and the power output end of the second switch tube T2 through the inductor L, the power 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 power input end of the second switch tube T2 is connected with the positive electrode of the output capacitor C2;
controlling the bidirectional DC/DC converter to cut off the current direct current line comprises the following steps: when the energy storage battery is charged, wave emission to the first switching tube T1 is stopped; when the energy storage battery is discharged, the wave sending to the second switch tube T2 is stopped.
8. The direct-current arc detection method according to claim 4, wherein on the current direct-current line, an 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 with a controllable switch in series;
thereby coordinating the power supply on other circuits and guaranteeing under the incessant power supply's of load prerequisite, make the current value on this direct current circuit reduce the arc extinguishing threshold value, include: and on the premise of coordinating the power supplies of the other types of power supplies and the power grid so as to ensure that the load supplies power uninterruptedly, the controllable switch is controlled to be switched off.
9. An energy conversion apparatus, comprising: the control unit and the energy conversion circuit with the direct current arc detection circuit;
the control unit is used for starting arc extinguishing operation when the direct current arc detection circuit judges that direct current arc is generated on a direct current line; releasing the arc extinguishing operation after delaying the preset time; and judging whether the direct current line is in an open circuit state after the arc extinguishing operation is released, and if so, judging that the direct current arc detection circuit judges that no fault exists.
10. The energy conversion device of claim 9, wherein the control unit is configured to perform an arc extinguishing operation by reducing a current value on the current dc line to an arc extinguishing threshold.
11. The energy conversion device according to claim 10, wherein when the energy conversion device is in an on-load state, the control unit is specifically configured to reduce the current value on the current dc line to an arc extinction threshold value on the premise of coordinating power supply on other lines to ensure uninterrupted power supply of the load.
12. The energy conversion apparatus according to claim 11, characterized in that the energy conversion apparatus comprises a bidirectional DC/DC converter and an inverter circuit; on the direct current 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 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 charging and discharging current value of the energy storage battery to an arc extinguishing threshold value on the premise of coordinating power supplies of other types of power supplies and a power grid so as to guarantee uninterrupted power supply of a load, so that the step of starting arc extinguishing operation is completed.
13. The energy conversion device of claim 11, wherein the energy storage battery is connected to the DC side of the inverter circuit via a bidirectional DC/DC converter on the DC line; 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 with a controllable switch in series;
and the control unit is specifically used for disconnecting the controllable switch on the premise of coordinating the power supplies of the other types of power supplies and the power grid so as to ensure that the load supplies power uninterruptedly, thereby completing the step of starting arc extinguishing operation.
14. The energy conversion device according to claim 12 or 13, wherein the other type of power source is a photovoltaic and correspondingly the energy conversion device is a light storage inverter.
15. A power generation system, comprising: the energy conversion device of any of claims 9-14, and one or more direct current power sources coupled to the energy conversion device.
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