CN111740392A - Fault protection method, intelligent combiner box and photovoltaic inversion system - Google Patents
Fault protection method, intelligent combiner box and photovoltaic inversion system Download PDFInfo
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- CN111740392A CN111740392A CN202010738431.3A CN202010738431A CN111740392A CN 111740392 A CN111740392 A CN 111740392A CN 202010738431 A CN202010738431 A CN 202010738431A CN 111740392 A CN111740392 A CN 111740392A
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- 238000004891 communication Methods 0.000 claims description 17
- 239000003990 capacitor Substances 0.000 claims description 6
- 238000004146 energy storage Methods 0.000 claims description 6
- QVFWZNCVPCJQOP-UHFFFAOYSA-N chloralodol Chemical compound CC(O)(C)CC(C)OC(O)C(Cl)(Cl)Cl QVFWZNCVPCJQOP-UHFFFAOYSA-N 0.000 claims description 4
- 238000003491 array Methods 0.000 claims description 3
- 238000010248 power generation Methods 0.000 abstract description 5
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
- H02S40/32—Electrical components comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
- H02S40/34—Electrical components comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
The application provides a fault protection method, an intelligent combiner box and a photovoltaic inversion system, wherein the fault protection method comprises the steps of firstly collecting branch current and output voltage of the intelligent combiner box through a control unit in the intelligent combiner box, and judging whether arc discharge fault or short circuit fault occurs on the direct current side of the intelligent combiner box according to a collection result; if the direct current side of the intelligent combiner box has arc discharge fault or short circuit fault, the control unit in the intelligent combiner box controls the direct current switch on the output side of the intelligent combiner box to be disconnected and sends fault information to the control unit in the inverter, and the control unit in the inverter controls the inverter to stop and disconnects the direct current switch and the alternating current switch in the inverter according to the fault information; furthermore, when short circuit fault or arc discharge fault occurs, the problem of serious arc discharge and even fire caused by overhigh direct-current voltage of the conventional photovoltaic power generation system can be avoided through the interlocking protection of the intelligent combiner box and the inverter, and the system safety is improved.
Description
Technical Field
The invention relates to the technical field of control, in particular to a fault protection method, an intelligent combiner box and a photovoltaic inverter system.
Background
In the photovoltaic power generation system, after the combiner box detects the input current and the output voltage of the branch circuit, a detection result is transmitted to a system background through a control unit in the combiner box for data display.
However, in the actual operation process, because the output voltage is high, and short circuit and other insulation failure faults occur on the direct current side of the photovoltaic module and the inverter, the direct current side is often severely arcing, and even a fire disaster occurs.
In this regard, how to avoid the above-mentioned security problem is a problem that needs to be solved.
Disclosure of Invention
Therefore, the application provides a fault protection method, an intelligent combiner box and a photovoltaic inverter system so as to improve the safety of the photovoltaic inverter system.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
the application discloses in a first aspect a fault protection method, which is applied to a photovoltaic inverter system, and comprises the following steps:
a control unit in an intelligent combiner box in the photovoltaic inverter system collects branch current and output voltage of the intelligent combiner box and judges whether arc discharge fault or short circuit fault occurs on the direct current side of the intelligent combiner box according to the collection result;
if an arc discharge fault or a short-circuit fault occurs on the direct-current side of the intelligent combiner box, the control unit in the intelligent combiner box controls a direct-current switch on the output side of the intelligent combiner box to be disconnected and sends fault information to a control unit in an inverter in the photovoltaic inversion system;
and the control unit in the inverter controls the inverter to stop according to the fault information and disconnects the direct current switch and the alternating current switch in the inverter.
Optionally, in the above-mentioned fault protection method, the controlling the inverter to stop and disconnect a dc switch and an ac switch in the inverter includes:
firstly, controlling a DCAC conversion circuit in the inverter to shut down;
and respectively controlling the direct current switch and the alternating current switch in the inverter to be switched off.
Optionally, in the fault protection method, determining whether a short-circuit fault occurs on a dc side of the intelligent combiner box according to the acquisition result includes:
respectively judging whether the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time and whether the branch current is increased to a preset range including component short-circuit current within preset time;
and if the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and the branch current is increased to a preset range including component short-circuit current within preset time, judging that the direct-current side of the intelligent combiner box has short-circuit fault.
Optionally, in the fault protection method, determining whether an arc discharge fault occurs on a dc side of the intelligent combiner box according to a collection result includes:
in a preset sampling window period, respectively judging whether the output voltage fluctuates back and forth at least twice in a preset range including open-circuit voltage and a preset range including zero voltage, and whether the branch current fluctuates back and forth at least twice in a preset range including component short-circuit current and a preset range including zero voltage;
and if the output voltage fluctuates back and forth at least twice within a preset range including open-circuit voltage and a preset range including zero voltage, and the branch current fluctuates back and forth at least twice within a preset range including component short-circuit current and a preset range including zero voltage, judging that the arc discharge fault occurs on the direct-current side of the intelligent combiner box.
Optionally, in the fault protection method, the controlling unit in the intelligent combiner box controlling the dc switch on the output side of the intelligent combiner box to be turned off includes:
and the control unit in the intelligent combiner box trips the direct-current switch at the output side of the intelligent combiner box.
The application second aspect discloses an intelligence collection flow box, includes: the device comprises a main circuit, a direct current switch, a branch current sampling device, an output voltage sampling device, a switching power supply and a control unit; wherein:
the branch current sampling equipment is arranged on each branch at the input side of the main circuit, and the output voltage sampling equipment is arranged at the output side of the main circuit;
the direct current switch is arranged on an output side cable of the main circuit;
the switching power supply is used for supplying power to the control unit;
the control unit is used for collecting the branch current and the output voltage of the intelligent combiner box through the branch current sampling equipment and the output voltage sampling equipment and judging whether an arc discharge fault or a short-circuit fault occurs on the direct-current side of the intelligent combiner box according to a collection result; if the direct current side of the intelligent combiner box has arc discharge fault or short circuit fault, the direct current switch on the output side of the intelligent combiner box is controlled to be disconnected, and fault information is sent to a control unit in the inverter, so that the control unit in the inverter controls the inverter to stop and disconnect the direct current switch and the alternating current switch in the inverter.
Optionally, in the above intelligent junction box, the switching power supply further includes: and the energy storage capacitor is connected between the two poles of the output end of the switching power supply.
Optionally, in the above intelligent junction box, the switching power supply takes power from the output side of the main circuit.
Optionally, in the above intelligent combiner box, the condition for determining that a short-circuit fault occurs on the dc side of the intelligent combiner box is as follows: the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and the branch current is increased to a preset range including component short-circuit current within preset time.
Optionally, in the above intelligent combiner box, the condition for determining that an arc discharge fault occurs on the dc side of the intelligent combiner box is as follows: in a preset sampling window period, the output voltage of the combiner box fluctuates back and forth at least twice within a preset range including open-circuit voltage and a preset range including zero voltage, and the branch current fluctuates back and forth at least twice within a preset range including component short-circuit current and a preset range including zero voltage.
Optionally, in the above-mentioned intelligent junction box, the dc switch has a trip coil controlled by the control unit.
The third aspect of the present application discloses a photovoltaic inverter system, including: a photovoltaic array, an inverter, and at least one intelligent combiner box as disclosed in any of the second aspects; wherein:
the photovoltaic arrays output electric energy to the inverters through the corresponding intelligent combiner boxes respectively;
the control units in the intelligent combiner boxes are in communication connection; the control unit in each intelligent combiner box is in communication connection with the control unit in the inverter;
and the control unit in the inverter is used for controlling the inverter to stop according to the fault information sent by the intelligent combiner box and disconnecting the direct current switch and the alternating current switch in the inverter.
Optionally, in the above photovoltaic inverter system, the inverter includes: the DC/AC conversion circuit comprises a direct current switch with a tripping coil, an alternating current switch with a tripping coil and a control unit; in the inverter:
the direct current switch is arranged on the direct current side of the DC/AC conversion circuit;
the alternating current switch is arranged on the alternating current side of the DC/AC conversion circuit;
the control unit controls the DC/AC conversion circuit to operate and controls the direct current switch and/or the alternating current switch to act through corresponding tripping coils.
Optionally, in the above photovoltaic inverter system, the control unit in the inverter is configured to control the inverter to stop according to the fault information sent by the intelligent combiner box, and disconnect the dc switch and the ac switch in the inverter, and specifically is configured to:
a control unit in the inverter firstly controls the DCAC conversion circuit to be shut down;
and the control unit in the inverter respectively controls the direct current switch and the alternating current switch in the inverter to be disconnected.
Optionally, in the photovoltaic inverter system, the control units in the intelligent combiner boxes, and the control units in the intelligent combiner boxes and the control units in the inverter are all communicated in any one of a CAN bus, an RS-485 communication mode, a PLC communication mode, an IO node communication mode, a ZigBee communication mode, and a Lora communication mode.
The fault protection method is applied to a photovoltaic inversion system, firstly, the branch current and the output voltage of an intelligent combiner box in the photovoltaic inversion system are collected through a control unit in the intelligent combiner box, and whether an arc discharge fault or a short-circuit fault occurs on the direct current side of the intelligent combiner box is judged according to the collection result; if the direct current side of the intelligent combiner box has arc discharge fault or short circuit fault, the control unit in the intelligent combiner box controls the direct current switch on the output side of the intelligent combiner box to be disconnected and sends fault information to the control unit in the inverter in the photovoltaic inversion system, and the control unit in the inverter controls the inverter to stop and disconnect the direct current switch and the alternating current switch in the inverter according to the fault information; furthermore, when short circuit fault or arc discharge fault occurs, the problem of serious arc discharge and even fire caused by overhigh direct-current voltage of the conventional photovoltaic power generation system can be avoided through the interlocking protection of the intelligent combiner box and the inverter, and the system safety is improved.
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 embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a flowchart of a fault protection method provided in an embodiment of the present application;
fig. 2 is a flowchart of determining whether a short-circuit fault occurs according to an embodiment of the present disclosure;
fig. 3 is a flowchart for determining whether an arc fault is provided in the embodiment of the present application;
fig. 4 is a schematic structural diagram of an intelligent combiner box according to an embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of a photovoltaic inverter system according to an embodiment of the present application.
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.
The embodiment of the application provides a fault protection method for improving the safety of a photovoltaic inverter system.
Referring to fig. 1, the fault protection method is applied to a photovoltaic inverter system, and mainly includes the following steps:
firstly, a control unit in an intelligent combiner box in a photovoltaic inverter system collects branch current and output voltage of the intelligent combiner box, and judges whether arc discharge fault or short circuit fault occurs on the direct current side of the intelligent combiner box according to a collection result. That is, step S101 shown below is executed first, and then step S102 is executed.
S101, a control unit in the intelligent combiner box collects branch current and output voltage of the intelligent combiner box.
In practical application, the branch current can be collected through corresponding branch current sampling equipment, such as a current sensor; and the output voltage is collected through corresponding output voltage sampling equipment, such as a voltage sensor, so as to obtain a collection result.
Of course, the branch current and the output voltage of the intelligent combiner box can be acquired in other ways in the prior art to obtain an acquisition result. The method for obtaining the acquisition result is not particularly limited, and all of the methods belong to the scope of protection of the present application.
S102, judging whether an arc discharge fault or a short circuit fault occurs on the direct current side of the intelligent combiner box according to the acquisition result.
Regarding the judgment of the short-circuit fault at the direct current side of the intelligent combiner box, see specifically fig. 2, that is, the specific process of judging whether the short-circuit fault occurs at the direct current side of the intelligent combiner box according to the acquisition result may be:
s201, respectively judging whether the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and whether the branch current is increased to a preset range including component short-circuit current within preset time.
The preset range including the zero voltage refers to all voltages in a certain range near the zero voltage, such as 0 to 100V, and the specific value of the preset range including the zero voltage is not limited, and only the condition including the zero voltage needs to be met.
The component short-circuit current is the short-circuit current of the photovoltaic component in the photovoltaic inverter system, which has a connection relation with the intelligent combiner box. The preset range including the component short-circuit current can be all currents in a certain range near the component short-circuit current, the specific value of the preset range including the component short-circuit current is not limited, and the condition including the component short-circuit current is only required to be met.
It should be noted that, the specific value in the preset time is not limited in the present application, but the shorter the value of the preset time is, the more accurate the obtained determination result is.
That is, in practical applications, it can be determined whether a short-circuit fault occurs on the dc side of the intelligent combiner box by determining whether the output voltage in the intelligent combiner box suddenly drops to near zero voltage and whether the branch current suddenly drops to near the component short-circuit voltage.
If the output voltage of the intelligent combiner box is decreased to a preset range including zero voltage within a preset time and the branch current is increased to a preset range including component short-circuit current within a preset time, step S202 is performed.
S202, judging that the direct current side of the intelligent combiner box has a short-circuit fault.
Specifically, in practical application, if it is determined that the output voltage in the intelligent combiner box suddenly drops to near zero voltage and the branch current suddenly drops to near the component short-circuit voltage, it is determined that a short-circuit fault occurs on the dc side of the intelligent combiner box.
Optionally, in practical applications, in addition to the method shown in fig. 2, the method may also be implemented by another method, for example:
and respectively judging whether the branch current and the output voltage meet preset short-circuit fault conditions. And if the branch current and the output voltage both meet the preset short-circuit fault condition, judging that the direct-current side of the intelligent combiner box has a short-circuit fault.
The preset short-circuit fault condition is as follows: the branch current is larger than the maximum current value of the inverter or the maximum current value of the photovoltaic direct current power supply of the controller under the standby condition, and the output voltage is smaller than half of the voltage of the maximum power point of the photovoltaic module under the standard test condition.
Specifically, it is assumed that the MPPT voltage range of the 500KW grade photovoltaic grid-connected inverter used in the photovoltaic inverter system is 460 + 850V, the minimum starting voltage is generally 460V, when the minimum starting voltage is lower than the maximum MPPT voltage, the inverter enters the standby mode, the dc side is switched to the open-circuit state, and the current flowing through the line at this time is zero. If the positive pole and the negative pole of the circuit are directly short-circuited, instantaneous voltages at two ends of the circuit drop to zero when a short-circuit point is switched on, and when a discharge gap occurs, the voltages at two ends of the circuit fluctuate along with the length of the gap, and the value of the voltage is generally maintained at dozens of volts and is far less than the minimum starting voltage of the inverter.
The upper limit of the voltage value for judging the short-circuit state can be set to be half of the voltage Vmp of the maximum power point of the photovoltaic module under the standard test condition, namely the preset short-circuit fault condition met by the output voltage is less than half of the voltage of the maximum power point of the photovoltaic module. For example, a 260Wp polysilicon module is adopted on the dc side, Vmp is 30.77 under a standard test environment, and every 21 photovoltaic modules are connected in series, so that the upper limit voltage value required for judging the short-circuit state is 323V, which avoids the dc side voltage interval value when the inverter normally operates, and can also cope with the voltage variation value under various short-circuit conditions.
And the current value interval corresponding to the branch current in the preset short-circuit fault condition should be not less than the maximum current value of the photovoltaic direct-current power supply when the inverter or the controller connected to the rear end of the photovoltaic direct-current side is in standby.
In practical application, the short-circuit fault of intelligence collection flow box direct current side is judged, can also adopt other modes, all is in the protection scope of this application.
Regarding the judgment of the arc fault of the direct current side of the intelligent combiner box, referring to fig. 3, the specific process of judging whether the arc fault occurs on the direct current side of the intelligent combiner box according to the acquisition result is as follows:
301. and respectively judging whether the output voltage fluctuates back and forth at least twice within a preset range including open-circuit voltage and a preset range including zero voltage and whether the branch current fluctuates back and forth at least twice within a preset range including component short-circuit current and a preset range including zero voltage within a preset sampling window period.
The preset sampling window period is a preset interval for collecting the time occupied by the output voltage and the branch current, and can be half an hour after the header box starts to normally operate, for example; of course, other time intervals are also possible, and the specific occupied time interval of the preset sampling window period is not limited in the present application and all belong to the protection scope of the present application.
The open-circuit voltage is the sum of all branch voltage corresponding to the intelligent combiner box in an output open-circuit state. The preset range including the open-circuit voltage can be all voltages in a certain range near the open-circuit voltage, and specific values of the preset range including the open-circuit voltage are not limited, and only conditions including the open-circuit voltage need to be met.
That is, in practical application, whether the arc discharge fault occurs on the direct current side of the intelligent combiner box can be determined by respectively judging whether the output voltage of the intelligent combiner box fluctuates back and forth at least twice around the open-circuit voltage and the zero voltage and whether the branch current fluctuates back and forth at least twice around the short-circuit current and the zero voltage of the component within a preset sampling window period.
If the output voltage fluctuates back and forth at least twice within the preset range including the open-circuit voltage and the preset range including the zero voltage, and the branch current fluctuates back and forth at least twice within the preset range including the component short-circuit current and the preset range including the zero voltage, step S302 is executed.
S302, judging that an arc discharge fault occurs on the direct current side of the intelligent combiner box.
In practical application, in a preset sampling window period, judging the mode that the output voltage of the intelligent combiner box fluctuates back and forth at least twice near the open-circuit voltage and the zero voltage and the mode that the branch current fluctuates back and forth at least twice near the short-circuit current and the zero voltage of the assembly, and judging that the arc discharge fault occurs on the direct-current side of the intelligent combiner box.
Optionally, in practical applications, in addition to the manner shown in fig. 3, it may also be determined whether an arc discharge fault occurs on the dc side of the intelligent combiner box by other manners, such as:
judging whether the branch current reaches a sudden change threshold value; and if the branch current reaches the mutation threshold value, judging that the arc discharge fault occurs on the direct current side of the intelligent combiner box.
Specifically, when the branch current reaches the abrupt change threshold, it can be said that the current branch current is unstable and the fluctuation range is large, and it can be said that the arc discharge fault occurs on the dc side.
It should be further noted that, the related description of determining whether the branch current reaches the abrupt change threshold may also refer to the prior art, and is not described in detail in this application.
In practical application, the arc fault of drawing of intelligence collection flow box direct current side is judged, can also adopt other modes, all is in the protection scope of this application.
Through the above-described fault determination method, it can be determined whether an arc discharge fault or a short-circuit fault occurs on the dc side of the intelligent combiner box, and if an arc discharge fault or a short-circuit fault occurs on the dc side of the intelligent combiner box, step S103 is executed.
S103, the control unit in the intelligent combiner box controls the direct current switch on the output side of the intelligent combiner box to be disconnected, and sends fault information to the control unit in the inverter in the photovoltaic inversion system.
In practical application, the control unit in the intelligent combiner box can trip the direct current switch on the output side of the intelligent combiner box to disconnect the direct current switch, so that the function of disconnecting the connection between the intelligent combiner box and the direct current bus of the inverter is realized.
And S104, controlling the inverter to stop according to the fault information by a control unit in the inverter, and disconnecting a direct current switch and an alternating current switch in the inverter.
In practical application, the control unit in the inverter can control the DCAC conversion circuit in the inverter to shut down, and then respectively control the direct current switch and the alternating current switch in the inverter to be disconnected, so as to cut off the connection between the two sides of the inverter and the direct current bus and the medium voltage side, thereby protecting the inverter from being influenced.
Based on the principle, when short-circuit fault or arc discharge fault occurs, the intelligent junction box and the inverter can be interlocked for protection, the connection between the direct-current bus and the intelligent junction box is cut off, and the connection between the two sides of the inverter and the direct-current bus and the medium-voltage side is cut off, so that the problem that the existing photovoltaic power generation system is prone to serious arc discharge and even fire when the direct-current voltage is too high is solved, and the safety of the system is improved.
On the basis of the fault protection method shown above, another embodiment of the present application further provides an intelligent combiner box, please refer to fig. 4, which mainly includes: a main circuit (including the respective fuses shown in the figure), a dc switch S1, a branch current sampling device (not shown), an output voltage sampling device (not shown), a switching power supply 102, and a control unit 101. Wherein:
the branch current sampling equipment is arranged on each branch of the input side of the main circuit, and the output voltage sampling equipment is arranged on the output side of the main circuit.
In practical application, the branch current sampling device may be a current sensor, and may also be other existing devices having a current sampling function.
Similarly, the output voltage sampling device may be a voltage sensor, or may be other existing devices with voltage sampling function, and the specific form of the output voltage sampling device is not limited in the present application, and all belong to the protection scope of the present application.
The dc switch S1 is provided on the output side cable of the main circuit.
Specifically, the dc switch S1 has a trip coil controlled by the control unit 101, so that the dc switch S1 can be turned off by controlling the trip coil to trip.
The switching power supply 102 is used to supply power to the control unit 101.
In practical application, the switching power supply 102 can directly take power from the output side of the main circuit, so that external power supply is not needed, and self-power control inside the intelligent combiner box is realized.
The control unit 101 is configured to collect branch currents and output voltages of the intelligent combiner box through a branch current sampling device and an output voltage sampling device, and determine whether an arc discharge fault or a short circuit fault occurs on a dc side of the intelligent combiner box according to a collection result; if an arc discharge fault or a short-circuit fault occurs on the direct current side of the intelligent combiner box, the direct current switch S1 on the output side of the intelligent combiner box is controlled to be switched off, fault information is sent to a control unit in the inverter, and the control unit in the inverter controls the inverter to stop and switches off the direct current switch and the alternating current switch in the inverter.
With reference to the foregoing embodiment and fig. 1, in practical application, the control unit 101 is configured to collect the branch current and the output voltage of the intelligent combiner box through the branch current sampling device and the output voltage sampling device, which is equivalent to executing step S101; and judging whether the arc discharge fault or the short circuit fault occurs on the direct current side of the intelligent combiner box according to the acquisition result, which is equivalent to executing the step S102. If an arc discharge fault or a short-circuit fault occurs on the direct current side of the intelligent combiner box, the direct current switch on the output side of the intelligent combiner box is controlled to be switched off, fault information is sent to a control unit in the inverter, and step S103 is executed equivalently. Further, the step S104 is executed to stop the inverter and turn off the dc switch and the ac switch in the inverter by the control unit in the inverter.
Specifically, in practical application, the conditions for determining the short-circuit fault on the dc side of the combiner box are as follows: the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and the branch current is increased to a preset range including component short-circuit current within preset time.
It should be noted that, for the process of determining whether the short-circuit fault occurs on the dc side of the combiner box, reference may be specifically made to the embodiment corresponding to fig. 2, and details are not described here again.
However, the conditions for determining the arc discharge fault on the dc side of the intelligent combiner box are as follows: in a preset sampling window period, the output voltage of the confluence box fluctuates back and forth at least twice in a preset range including open-circuit voltage and a preset range including zero voltage, and the branch current fluctuates back and forth at least twice in a preset range including component short-circuit current and a preset range including zero voltage.
It should be noted that, for the determination process of whether the arc discharge fault occurs on the dc side of the intelligent combiner box, reference may be specifically made to the embodiment corresponding to fig. 3, and details are not described here again.
Based on the above description, when a short-circuit fault or an arc discharge fault occurs, the connection between the dc bus and the intelligent combiner box can be cut off through the interlocking protection of the intelligent combiner box and the inverter, and the connection between the two sides of the inverter and the dc bus and the medium-voltage side can be cut off, so that the problem that the existing photovoltaic power generation system is easily subjected to serious arc discharge or even fire due to overhigh dc voltage is solved, and the system safety is improved.
Optionally, referring also to fig. 4, in practical applications, the intelligent combiner box further includes: at least one energy storage capacitor C1 connected between the two output terminals of the switching power supply 102.
When the voltage on the input side of the main circuit of the intelligent combiner box is abnormal or short-circuited, so that the switching power supply 102 cannot normally supply power to the control unit 101, the energy storage capacitor C1 can release the electric energy stored by itself to maintain power supply to the control unit 101 within a period of time, and then the control unit 101 can be ensured to complete actions such as fault state detection, tripping of the direct current switch S1 in the combiner box, fault information generation and the like, and the capability of the intelligent combiner box for fault protection is further improved.
The capacitance value of the energy storage capacitor C1 depends on the specific application environment, and the above functions can be realized, all within the protection scope of the present application.
On the basis of the above-mentioned fault protection method and intelligent combiner box, another embodiment of the present application further provides a photovoltaic inverter system, please refer to fig. 5, where the photovoltaic inverter system mainly includes: photovoltaic array 103, inverter 104 and at least one intelligent combiner box 105 as described in any of the above embodiments. Wherein:
the photovoltaic arrays 103 each output electrical energy to the inverter 104 through a respective intelligent combiner box 105.
In practical application, the connection mode of each intelligent combiner box 105 in the photovoltaic inverter system may be cascade connection, or may be parallel connection as shown in fig. 5, and the specific connection mode of each intelligent combiner box 105 is not limited in the present application, and may be determined according to the specific application environment, and both belong to the protection scope of the present application.
Communication connections between the control units 101 in each intelligent combiner box 105; the control unit 101 in each intelligent combiner box 105 is communicatively connected to the control unit 1042 in the inverter 104.
Specifically, the communication between the control units 101 in the intelligent combiner boxes 105, and between the control unit 101 in the intelligent combiner box 105 and the control unit 1042 in the inverter 104 may be performed through any one of a CAN bus (controller area network), RS-485, PLC (Programmable logic controller), IO node, ZigBee (purple peak), and Lora communication modes, so as to ensure real-time interaction of information between the control unit 101 in the intelligent combiner box 105 and the control unit 1042 in the inverter 104, thereby ensuring that the control unit 101 in the intelligent combiner box 105 CAN send fault information to the control unit 1042 in the inverter 104 in time after determining a fault. In practical applications, other communication methods may also be adopted, and are not specifically limited herein.
The control unit 1042 in the inverter 104 is used for controlling the inverter 104 to stop according to the fault information sent by the intelligent combiner box 105, and disconnecting the direct current switch S2 and the alternating current switch S3 in the inverter 104.
Referring also to fig. 5, the inverter 104 includes: a DC/AC conversion circuit 1041, a direct current switch S2 with a trip coil, an alternating current switch S3 with a trip coil, and a control unit 1042; in the inverter 104:
the DC switch S2 is provided on the DC side of the DC/AC conversion circuit 1041.
The AC switch S3 is provided on the AC side of the DC/AC conversion circuit 1041.
The control unit 1042 controls the DC/AC conversion circuit 1041 to operate, and controls the direct current switch S2 and/or the alternating current switch S3 to operate through the corresponding trip coil.
Specifically, if the tripping coil corresponding to the direct current switch S2 is controlled to trip, the direct current switch S2 is turned off; if the tripping coil corresponding to the AC switch S3 is controlled to trip, the AC switch S3 is turned off.
In practical applications, the control unit 1042 in the inverter 104 is configured to control the inverter 104 to stop according to the fault information sent by the intelligent combiner box 105, and disconnect the dc switch S2 and the ac switch S3 in the inverter 104, and specifically configured to:
the control unit 1042 controls the DCAC conversion circuit 1041 to shut down first, and then controls the dc switch S2 and the ac switch S3 to turn off respectively.
It should be noted that, the principle and the related description of the intelligent combiner box 105 can be referred to the embodiment corresponding to fig. 4, and are not described herein again.
Based on the photovoltaic inverter system provided in fig. 5, a specific process of the photovoltaic inverter system to execute the fault protection method is described in detail below with a specific example:
if a short-circuit fault or an arc fault occurs on the input side of the intelligent combiner box 105 or the dc side of the inverter 104, since the energy storage capacitor C1 is disposed between the two poles of the output terminal of the switching power supply 102 in the intelligent combiner box 105, power supply to the control unit 101 in the intelligent combiner box 105 CAN be maintained for a period of time, so that the control unit 101 CAN be ensured to complete fault detection and trip the dc switch S1, and fault information is transmitted to the control unit 1042 in the inverter 104 through any one of the CAN bus, RS-485, PLC, IO node, ZigBee and Lora communication modes.
The control unit 1042 in the inverter 104 controls the DCAC conversion circuit 1041 in the inverter 104 to shut down according to the fault information, and then controls the direct current switch S2 and the alternating current switch S3 to be turned off at the same time, so that the whole photovoltaic inversion system is turned off in sections, the intelligent combiner box 105 and the inverter 105 are protected in a linkage manner, and further extension of the fault is prevented.
Features described in the embodiments in the present specification may be replaced with or combined with each other, and the same and similar portions among the embodiments may be referred to each other, and each embodiment is described with emphasis on differences from other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
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 invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. 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, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (15)
1. A fault protection method is applied to a photovoltaic inverter system and comprises the following steps:
a control unit in an intelligent combiner box in the photovoltaic inverter system collects branch current and output voltage of the intelligent combiner box and judges whether arc discharge fault or short circuit fault occurs on the direct current side of the intelligent combiner box according to the collection result;
if an arc discharge fault or a short-circuit fault occurs on the direct-current side of the intelligent combiner box, the control unit in the intelligent combiner box controls a direct-current switch on the output side of the intelligent combiner box to be disconnected and sends fault information to a control unit in an inverter in the photovoltaic inversion system;
and the control unit in the inverter controls the inverter to stop according to the fault information and disconnects the direct current switch and the alternating current switch in the inverter.
2. The fault protection method of claim 1, wherein the controlling the inverter to shutdown and open dc and ac switches in the inverter comprises:
firstly, controlling a DCAC conversion circuit in the inverter to shut down;
and respectively controlling the direct current switch and the alternating current switch in the inverter to be switched off.
3. The fault protection method according to claim 1 or 2, wherein judging whether a short-circuit fault occurs on the direct current side of the intelligent combiner box according to the acquisition result comprises:
respectively judging whether the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time and whether the branch current is increased to a preset range including component short-circuit current within preset time;
and if the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and the branch current is increased to a preset range including component short-circuit current within preset time, judging that the direct-current side of the intelligent combiner box has short-circuit fault.
4. The fault protection method according to claim 1 or 2, wherein judging whether an arc discharge fault occurs on the direct current side of the intelligent combiner box according to the acquisition result comprises:
in a preset sampling window period, respectively judging whether the output voltage fluctuates back and forth at least twice in a preset range including open-circuit voltage and a preset range including zero voltage, and whether the branch current fluctuates back and forth at least twice in a preset range including component short-circuit current and a preset range including zero voltage;
and if the output voltage fluctuates back and forth at least twice within a preset range including open-circuit voltage and a preset range including zero voltage, and the branch current fluctuates back and forth at least twice within a preset range including component short-circuit current and a preset range including zero voltage, judging that the arc discharge fault occurs on the direct-current side of the intelligent combiner box.
5. The fault protection method according to claim 1 or 2, wherein the controlling unit in the intelligent combiner box controls the direct current switch on the output side of the intelligent combiner box to be turned off, and comprises the following steps:
and the control unit in the intelligent combiner box trips the direct-current switch at the output side of the intelligent combiner box.
6. An intelligence collection flow box, its characterized in that includes: the device comprises a main circuit, a direct current switch, a branch current sampling device, an output voltage sampling device, a switching power supply and a control unit; wherein:
the branch current sampling equipment is arranged on each branch at the input side of the main circuit, and the output voltage sampling equipment is arranged at the output side of the main circuit;
the direct current switch is arranged on an output side cable of the main circuit;
the switching power supply is used for supplying power to the control unit;
the control unit is used for collecting the branch current and the output voltage of the intelligent combiner box through the branch current sampling equipment and the output voltage sampling equipment and judging whether an arc discharge fault or a short-circuit fault occurs on the direct-current side of the intelligent combiner box according to a collection result; if the direct current side of the intelligent combiner box has arc discharge fault or short circuit fault, the direct current switch on the output side of the intelligent combiner box is controlled to be disconnected, and fault information is sent to a control unit in the inverter, so that the control unit in the inverter controls the inverter to stop and disconnect the direct current switch and the alternating current switch in the inverter.
7. The intelligent combiner box of claim 6, wherein the switching power supply further comprises: and the energy storage capacitor is connected between the two poles of the output end of the switching power supply.
8. The intelligent combiner box of claim 6, wherein the switching power supply takes power from an output side of the main circuit.
9. The intelligent combiner box of any of claims 6-8, wherein the conditions for determining short-circuit fault on the dc side of the intelligent combiner box are: the output voltage of the intelligent combiner box is reduced to a preset range including zero voltage within preset time, and the branch current is increased to a preset range including component short-circuit current within preset time.
10. The intelligent combiner box of any one of claims 6-8, wherein the conditions for determining the arc fault on the dc side of the intelligent combiner box are as follows: in a preset sampling window period, the output voltage of the combiner box fluctuates back and forth at least twice within a preset range including open-circuit voltage and a preset range including zero voltage, and the branch current fluctuates back and forth at least twice within a preset range including component short-circuit current and a preset range including zero voltage.
11. The intelligent combiner box of any of claims 6-8, wherein the dc switch has a trip coil controlled by the control unit.
12. A photovoltaic inverter system, comprising: a photovoltaic array, an inverter and at least one intelligent combiner box of any of claims 6-11; wherein:
the photovoltaic arrays output electric energy to the inverters through the corresponding intelligent combiner boxes respectively;
the control units in the intelligent combiner boxes are in communication connection; the control unit in each intelligent combiner box is in communication connection with the control unit in the inverter;
and the control unit in the inverter is used for controlling the inverter to stop according to the fault information sent by the intelligent combiner box and disconnecting the direct current switch and the alternating current switch in the inverter.
13. The pv inversion system of claim 12, wherein the inverter comprises: the DC/AC conversion circuit comprises a direct current switch with a tripping coil, an alternating current switch with a tripping coil and a control unit; in the inverter:
the direct current switch is arranged on the direct current side of the DC/AC conversion circuit;
the alternating current switch is arranged on the alternating current side of the DC/AC conversion circuit;
the control unit controls the DC/AC conversion circuit to operate and controls the direct current switch and/or the alternating current switch to act through corresponding tripping coils.
14. The pv inversion system of claim 13, wherein the control unit in the inverter is configured to control the inverter to stop according to the fault information sent by the intelligent combiner box, and disconnect the dc switch and the ac switch in the inverter, and specifically configured to:
a control unit in the inverter firstly controls the DCAC conversion circuit to be shut down;
and the control unit in the inverter respectively controls the direct current switch and the alternating current switch in the inverter to be disconnected.
15. The photovoltaic inverter system according to any one of claims 12 to 14, wherein the communication between the control units in the intelligent combiner boxes, and the communication between the control units in the intelligent combiner boxes and the control units in the inverters are performed through any one of CAN bus, RS-485, PLC, IO node, ZigBee, and Lora communication.
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