CN112821362A - Multi-path direct-current isolating switch, string type photovoltaic inverter, combiner box, photovoltaic system and control method of photovoltaic system - Google Patents
Multi-path direct-current isolating switch, string type photovoltaic inverter, combiner box, photovoltaic system and control method of photovoltaic system Download PDFInfo
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- 238000010248 power generation Methods 0.000 abstract description 6
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02S40/34—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
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Abstract
The invention provides a multi-path direct-current isolating switch, a string type photovoltaic inverter, a combiner box, a photovoltaic system and a control method thereof, wherein the multi-path direct-current isolating switch is provided with N switch bodies, each switch body is correspondingly connected with a corresponding photovoltaic string, and a control circuit controls each corresponding switch body to be disconnected according to a received control signal so as to realize the control of the disconnection of each corresponding photovoltaic string; that is, if one or more photovoltaic string in the photovoltaic system fails, a few photovoltaic strings containing the failed photovoltaic string can be removed through the multi-path direct-current isolating switch, and the photovoltaic system can be recovered after the failure is removed. Therefore, compared with the technical scheme that the whole photovoltaic inverter can only be turned off if the photovoltaic string fails in the prior art, the multi-path direct-current isolating switch provided by the embodiment of the invention can only eliminate a small number of photovoltaic strings, ensures the reliable turn-off of the failed photovoltaic string, and reduces the loss of the power generation amount of a photovoltaic system.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a multi-path direct-current isolating switch, a string type photovoltaic inverter, a combiner box, a photovoltaic system and a control method thereof.
Background
In the prior art, multiple photovoltaic string strings (shown as PV panel in fig. 1) are generally connected to a string-type photovoltaic inverter, and a boost loop (shown as boost in fig. 1) boosts a dc voltage of the photovoltaic string to a dc voltage required for inverter output control; the Inverter bridge circuit (shown as Inverter in fig. 1) converts the boosted dc voltage into ac voltage with common frequency, and the schematic structural diagram is shown in fig. 1, and according to the grid-connected requirement, the string-type photovoltaic Inverter needs to be provided with a dc switch on its dc line, so as to complete the overhaul and maintenance work of the equipment at a later stage.
As shown in fig. 1, the dc switch of the string inverter is a manual switch, and the switching-off and switching-on of the dc switch need to be controlled by an operating handle; when the group of series inverters runs, if the direct current side of the series inverters breaks down, the inverters are always connected with a fault point because the handles cannot be operated in time, so that the inverters can only be controlled to stop working, and the loss of generated energy is huge.
Disclosure of Invention
In view of this, embodiments of the present invention provide a multi-path dc isolation switch, a string-type photovoltaic inverter, a combiner box, a photovoltaic system, and a control method thereof, which can effectively distinguish and shut down when a photovoltaic string fails, ensure reliable operation of the inverter, and reduce loss of power generation amount.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
the invention provides a multi-path direct current isolating switch in a first aspect, which comprises: at least one control circuit and N switch bodies; n is a positive integer greater than 1; wherein:
the front stage of each switch body is respectively connected with the corresponding photovoltaic group string;
the output end of the control circuit is respectively connected with the control end of each corresponding switch body and used for controlling the disconnection of each corresponding switch body according to the received control signal so as to realize the control of the disconnection of each corresponding photovoltaic group string.
Preferably, the control circuit is further configured to control each corresponding switch body to be closed according to the received control signal, so as to control the access of each corresponding photovoltaic group string.
Preferably, the number of the control circuits is equal to 1, and the output ends of the control circuits are connected with the control ends of the N switch bodies.
Preferably, the switch body includes: the controllable switch is arranged on the positive branch of the corresponding photovoltaic string, and/or the controllable switch is arranged on the negative branch of the corresponding photovoltaic string.
Preferably, the multi-path dc isolating switch further includes: an operating handle; wherein:
the operating handle is used for manually controlling the on-off of the switch body.
Preferably, the multi-path dc isolating switch further includes: and the manual switch is used for realizing control right locking of the switch body.
A second aspect of the present invention provides a string-type photovoltaic inverter, including: the controller, the inverter circuit and at least one multi-path direct current isolating switch as any one of the above parts; wherein:
the multi-path direct-current isolating switches are arranged on the direct-current input side of the string photovoltaic inverter, and the sum of the number of control circuits in all the multi-path direct-current isolating switches is greater than 1;
the controller is used for controlling the working state of the inverter circuit, is in communication connection with each control circuit in the multi-path direct current isolating switch, and sends control signals to each control circuit to respectively control each photovoltaic group string connected with the multi-path direct current isolating switch to be connected into or disconnected from the group string type photovoltaic inverter.
Preferably, at the dc input side of the string-type photovoltaic inverter, there is a corresponding switch body in which the multiple dc isolation switches are disposed in at least one branch.
Preferably, each branch provided with the switch body is respectively connected with at least one photovoltaic string.
Preferably, the string-type photovoltaic inverter further includes: and the current detection circuits are respectively used for detecting the current of each branch circuit on the direct current input side of the string type photovoltaic inverter.
Preferably, the string-type photovoltaic inverter further includes: and the insulation resistance detection circuit is used for detecting the insulation resistance on the direct current side and the insulation resistance on the alternating current side of the inverter circuit.
Preferably, the string-type photovoltaic inverter further includes: a plurality of DC/DC conversion circuits controlled by the controller;
and each DC/DC conversion circuit is respectively arranged between each switch body in the multi-path DC isolating switch and the DC side of the inverter circuit.
Preferably, the string-type photovoltaic inverter further includes: and a plurality of insulation resistance detection circuits provided at the input terminals of the respective DC/DC conversion circuits.
A third aspect of the present invention provides a junction box including: the device comprises a controller, a bus bar and at least one multi-path direct current isolating switch as described in any one of the above items; wherein:
the multi-path direct current isolating switches are arranged at the front stage of the bus bar, and the sum of the number of control circuits in all the multi-path direct current isolating switches is more than 1;
the controller is in communication connection with each control circuit in the multi-path direct current isolating switch and used for sending control signals to each control circuit and respectively controlling each photovoltaic group connected with the multi-path direct current isolating switch to be connected into or disconnected from the combiner box in a serial mode.
Preferably, the junction box further includes: the bus bar pre-stage circuit comprises an insulation resistance detection circuit arranged at a bus bar, or a plurality of insulation resistance detection circuits respectively arranged on each branch of the bus bar pre-stage.
Preferably, the junction box further includes: a plurality of fuses; wherein:
the fuses are respectively arranged at the front stage or the rear stage of each switch body in the multi-path direct current isolating switch.
Preferably, the junction box further includes: and the main switch is arranged at the rear stage of the bus bar.
A fourth aspect of the present invention provides a photovoltaic system comprising: at least one string inverter as described in any one of the preceding claims and a plurality of photovoltaic strings preceding it; or a centralized inverter, at least one combiner box as described in any of the above, and a plurality of photovoltaic string at its front stage.
The fourth aspect of the present invention provides a control method for a photovoltaic system, which is applied to the photovoltaic system described above, and the control method includes:
after the photovoltaic system is controlled to be started and operated, whether a photovoltaic string in the photovoltaic system fails or not is judged;
and if the judgment result is yes, controlling the switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the failed photovoltaic group string in the photovoltaic system to be switched off.
Preferably, after the controlling of the opening of the switch body corresponding to the failed photovoltaic string in the multi-path dc isolation switch in the photovoltaic system, the method further includes:
and after the fault disappears, controlling the switch body to be switched on to enable the corresponding photovoltaic group string to normally operate.
Preferably, the fault includes: arcing, short circuit, leakage current, overcurrent, overvoltage, ground fault, or current reversal.
Preferably, if an insulation resistance detection circuit is disposed in the photovoltaic system, before the controlling of the photovoltaic system to start operation, the method further includes:
judging whether the starting insulation requirement of the photovoltaic system is met or not according to the detected direct current side insulation impedance and alternating current side insulation impedance of the series photovoltaic inverter in the photovoltaic system or the ground insulation impedance of a busbar of a combiner box in the photovoltaic system;
and if so, controlling the photovoltaic system to start and operate.
Preferably, after determining whether the starting insulation requirement of the photovoltaic system is met according to the detected dc side insulation impedance, ac side insulation impedance of the series photovoltaic inverter in the photovoltaic system or the ground insulation impedance of the busbar of the combiner box in the photovoltaic system, the method further includes:
if the starting insulation requirement of the photovoltaic system is judged not to be met according to the detected insulation impedance of the direct current side of the series photovoltaic inverter in the photovoltaic system or the insulation impedance of the ground of a busbar of a combiner box in the photovoltaic system, all switch bodies in a plurality of paths of direct current isolating switches in the photovoltaic system are controlled to be switched off;
sequentially controlling the switch bodies controlled by the control circuits in the multi-path direct current isolating switches to be switched on, and detecting the insulation impedance of the corresponding photovoltaic group strings; and after the switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the photovoltaic group string with low control insulation impedance is switched off and other switch bodies are switched on, if the starting insulation requirement of the photovoltaic system is met, the photovoltaic system is controlled to start and operate.
Based on the multi-path direct current isolating switch provided by the embodiment of the invention, the multi-path direct current isolating switch is provided with N switch bodies, each switch body is correspondingly connected with a corresponding photovoltaic group string, and the control circuit controls each corresponding switch body to be disconnected according to a received control signal so as to realize the control of the disconnection of each corresponding photovoltaic group string; that is, if one or more photovoltaic strings in the photovoltaic system have a fault, in order to avoid the influence on the normal operation of the strings, a few photovoltaic strings containing the faulty photovoltaic strings can be removed through the multi-path direct-current isolating switch, and the operation is recovered after the fault is removed. Therefore, compared with the technical scheme that the whole photovoltaic inverter can only be turned off if the photovoltaic string fails in the prior art, the multi-path direct-current isolating switch provided by the embodiment of the invention can only eliminate a small number of photovoltaic strings, simultaneously ensures the reliable turn-off of the failed photovoltaic string, keeps the other photovoltaic strings in normal operation, and simultaneously reduces the loss of the power generation amount of a photovoltaic system.
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 schematic structural diagram of a string-type photovoltaic inverter provided in the prior art;
fig. 2 is a schematic structural diagram of a multi-path dc isolating switch according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a multi-path dc isolating switch provided with an operating handle according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a string-type photovoltaic inverter according to another embodiment of the present invention;
fig. 5 is a schematic structural diagram of an insulation resistance detection circuit provided in a string-type photovoltaic inverter according to another embodiment of the present invention;
fig. 6 is a schematic structural diagram of a connection between a centralized photovoltaic inverter and a combiner box provided in the prior art;
fig. 7 is a schematic structural view of a junction box provided in the prior art;
fig. 8 is a schematic structural view of a junction box according to another embodiment of the present invention;
fig. 9 is a schematic structural diagram of an insulation resistance detection circuit provided in a bus bar box according to another embodiment of the present invention;
fig. 10 is a schematic structural diagram of a photovoltaic system according to another embodiment of the present invention;
fig. 11 is a flowchart of a control method of a photovoltaic system according to another embodiment of the present invention;
fig. 12 is a flowchart of another control method for a photovoltaic system according to another embodiment of the present invention;
fig. 13 is a flowchart of another control method for a photovoltaic system according to another embodiment of the present invention;
fig. 14 is a schematic structural diagram of a string-type photovoltaic inverter according to another embodiment of the present invention.
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.
In this application, 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.
The embodiment of the invention provides a multi-path direct current isolating switch which can be effectively distinguished and switched off when a photovoltaic string fails, so that the reliable operation of an inverter is ensured, and the loss of generated energy is reduced.
The schematic structural diagram of the multi-path direct current isolating switch is shown in fig. 2, and the multi-path direct current isolating switch comprises: at least one control circuit 110 and N switch bodies 120; n is a positive integer greater than 1; wherein:
fig. 2 shows an example that two switch bodies 120 and one control circuit 110 form a multi-path dc isolation switch, in practical application, two control circuits 110 may respectively control two switch bodies 120, or a plurality of switch bodies 120 are provided, one control circuit 110 controls a plurality of switch bodies 120, and a plurality of control circuits 110 may control a plurality of switch bodies 120, that is, the number of control circuits 110 is greater than or equal to 1, which is within the protection scope of the embodiment of the present invention. Preferably, 1 control circuit 110 controls N switch bodies 120, which further saves cost.
The front stage of each switch body 120 is connected to a corresponding photovoltaic string (as shown in the PV panel in fig. 2); the output end of the control circuit 110 is connected to the control end of each corresponding switch body 120, so as to transmit a corresponding driving signal, and further, the switch bodies 120 connected to the control circuit are controlled to be disconnected according to the control signal received by the input end of the control circuit, so as to control the disconnection of each corresponding photovoltaic string. In addition, the control circuit 110 can also control the switch bodies 120 to be closed according to the received control signal, so as to control the serial access of the corresponding photovoltaic groups.
In practical applications, each switch body 120 may specifically include: and the controllable switch is arranged on the positive branch and/or the controllable switch on the negative branch of each photovoltaic string. Assuming that N is 2, each switch body 120 includes two controllable switches respectively disposed in the positive branch and the negative branch of the photovoltaic string, and the schematic structural diagram thereof is shown in fig. 2, at this time, the on/off of the controllable switches in each switch body 120 is respectively controlled by the control circuit 110, and the schematic structural diagrams of the multi-path dc isolation switch provided with the plurality of switch bodies 120 can be seen in fig. 4-5 and 8-10.
The multi-path direct-current isolating switch provided by the embodiment can be arranged on the direct-current input side of the string-type photovoltaic inverter, or arranged at the front stage of a bus bar of a combiner box; and, each group of string photovoltaic inverter or the header box can be provided with at least one of the multi-path direct current isolating switches, and the number of the multi-path direct current isolating switches inside the group of string photovoltaic inverter or the header box is determined according to the specific application environment, and is within the protection scope of the application.
In the string-type photovoltaic inverter or the combiner box, each switch body 120 in the multi-path direct current isolating switch is correspondingly connected with each photovoltaic string one by one, the control circuit 110 can receive a control signal sent by a controller in the string-type photovoltaic inverter or the photovoltaic combiner box, and control the on/off of each switch body 120 according to the control signal, when the photovoltaic system is started, the corresponding photovoltaic groups are connected in series to the inverter or the combiner box, when a certain photovoltaic string has a fault, such as the photovoltaic string has the problems of arc discharge fault, short circuit, leakage current, overcurrent, overvoltage, ground fault or current reverse fault, the fault photovoltaic string is effectively distinguished, a few photovoltaic strings containing the fault photovoltaic string are removed, at most, N photovoltaic strings are simultaneously removed, the fault photovoltaic string is reliably turned off, and the rest photovoltaic strings keep normal operation; compared with the technical scheme that the whole photovoltaic inverter can only be turned off if the photovoltaic string fails in the prior art, the multi-path direct-current isolating switch provided by the embodiment of the invention can only eliminate a small number of photovoltaic strings, and the loss of the power generation amount of a photovoltaic system is reduced.
It should be noted that the number N of the switch bodies 120 in the multi-path dc isolating switch may be a value greater than or equal to 2 by a skilled person according to a specific application, as long as the front stage of the switch body 120 is a photovoltaic string. The smaller the value of N is, the more fine the fault group string elimination is; the larger the value of N is, the more the number and the overall cost of the control circuit 110 can be saved; therefore, the value thereof depends on the specific application environment, and is within the protection scope of the present application.
It should be noted that, each switch body 120 may be turned on or off by manual control, and at this time, the multi-path dc isolation switch further includes: an operating handle; the structural schematic diagram is shown in fig. 3, and by matching the operating handle with the control circuit 110, each switch body 120 in the multi-path direct current disconnecting switch can realize manual or automatic switching-off and switching-on, so as to ensure reliable switching-on or switching-off of each photovoltaic string.
Since the control signals received by the same control circuit 110 or the same operation handle are the same, the switch bodies 120 controlled by the same control circuit 110 or the same operation handle are operated simultaneously, that is, are opened or closed simultaneously.
Preferably, the multi-way dc isolation switch further comprises: a manual switch for implementing control right locking to the switch body 120; for example, a manually operated button or handle (not shown) is provided for selecting the same one of the control circuit 110 and the operation handle to control the switch body 120, so as to avoid control conflict between the local operation and the remote operation on the same switch body 120, or to achieve function locking.
Another embodiment of the present invention further provides a string-type photovoltaic inverter, a schematic structural diagram of which is shown in fig. 4, the string-type photovoltaic inverter includes: a controller 210, an inverter circuit 220, and at least one multi-way dc isolation switch (1 shown as an example) provided in the above embodiments; wherein:
the multi-path direct-current isolating switch is arranged on the direct-current input side of the group of series photovoltaic inverters; the controller 210 is configured to control a working state of the inverter circuit 220, and is in communication connection with each control circuit 110 in the multi-path dc isolation switch, so as to send a control signal to each control circuit 110, and respectively control each photovoltaic string connected to the multi-path dc isolation switch to be connected to or disconnected from the string-type photovoltaic inverter.
The direct current input side of the group of series photovoltaic inverters is provided with corresponding switch bodies of a plurality of paths of direct current isolating switches in at least one branch, and preferably, each branch is provided with a corresponding switch body; the front stage of each switch body is connected with at least one photovoltaic group string, and the on-off of each switch body is controlled to realize the control of switching in and switching out the group of string type photovoltaic inverters of the photovoltaic group strings connected with the switch body. The sum of the number of the control circuits 110 in all the multiple dc isolators in the set of series-connected pv inverters is greater than 1, for example, a plurality of multiple dc isolators are provided on the dc input side of the set of series-connected pv inverters, and all the switch bodies in each multiple dc isolator are controlled by one control circuit 110 (not shown), or, as shown in fig. 4, only one multiple dc isolator is provided, but a plurality of control circuits 110 are provided inside to control each corresponding switch body.
As shown in fig. 4, the string-type photovoltaic inverter needs to be connected to a plurality of photovoltaic strings, and if there are a corresponding number of switch bodies in the multi-path dc isolation switches arranged on the dc input side of the inverter, only one multi-path dc isolation switch needs to be arranged; when N is 2, the number of the multi-path direct current isolating switches is equal to the number of the photovoltaic string, and when the number of the photovoltaic string is an odd number, the number of the multi-path direct current isolating switches is 0.5 after the number of the photovoltaic string is divided by 2; the scheme of setting a plurality of multi-path direct current isolating switches can be analogized, and is not described in detail.
The controller 210 may be a controller in the string-type photovoltaic inverter, or may be any control chip additionally disposed outside the multi-path dc isolation switch, such as a Microcontroller (MCU), for controlling the operation of the entire string-type photovoltaic inverter.
It should be noted that the output of the string-type pv inverter can be connected to the grid, as shown in fig. 4, or can be connected to a load or connected in parallel or in cascade (not shown) with the ac side of other inverters, as the case may be.
Preferably, the string-type photovoltaic inverter further includes: an insulation resistance detection circuit for detecting the insulation resistance on the dc side and the insulation resistance on the ac side of the inverter circuit 220. When the insulation resistance detection circuit can be disposed on the dc side of the string-type photovoltaic inverter, the schematic structure of the insulation resistance detection circuit is shown in fig. 5, or the inverter circuit 220 itself has an insulation resistance detection circuit (not shown).
It should be noted that, the group of series photovoltaic inverters may only have power conversion of the level of the inverter circuit, and at this time, each switch body in the multi-path dc isolation switch is disposed on the dc side of the inverter circuit; in practical applications, the set of series-connected photovoltaic inverters may further include: a plurality of DC/DC conversion circuits 230 controlled by the controller 210, the structure of which is schematically shown in fig. 14; wherein, each DC/DC conversion circuit 230 is respectively disposed between each switch body 120 and the DC side of the inverter circuit 220 in the multi-path DC isolation switch; that is, a DC/DC conversion circuit 230 is connected to the rear of each switch body 120 in the multi-way DC isolation switch, and the output end of the DC/DC conversion circuit 230 is connected to the DC side of the inverter circuit 220 in parallel. At this time, the insulation resistance detection function of the string-type photovoltaic inverter may be performed by: a plurality of insulation resistance detection circuits (not shown) provided at the input terminals of the DC/DC conversion circuits 230, respectively.
According to the string-type photovoltaic inverter provided by the embodiment of the invention, the multi-path direct-current isolating switch is arranged on the direct-current input side of the string-type photovoltaic inverter, when a fault occurs in a photovoltaic string connected with the string-type photovoltaic inverter, the fault photovoltaic string can be effectively distinguished, a small number of photovoltaic strings controlled by the same control circuit in the multi-path direct-current isolating switch corresponding to the fault photovoltaic string are switched off, other photovoltaic strings still keep normal work, the situation that the whole photovoltaic inverter can only be switched off in the prior art is avoided, and the loss of generated energy is reduced.
In practical applications, the photovoltaic string has many types of faults, for example, faults such as overcurrent, overvoltage, or current reversal, and therefore, the string-type photovoltaic inverter may further include: and the current detection circuits are respectively used for detecting the current of each branch circuit on the direct current input side of the string type photovoltaic inverter, and if each branch circuit is respectively connected with a corresponding photovoltaic string, the output current of each photovoltaic string is detected so as to judge whether the photovoltaic string has the faults or not.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
In the prior art, in order to reduce the connection between the pv strings and the inverters, there is a centralized inverter, a schematic structural diagram of which is shown in fig. 6, a plurality of pv strings are connected in parallel to a combiner box, and after the combiner box is combined, grid connection is realized by the centralized inverter. At this time, a dc main switch is also disposed on the output side of the combiner box, and its structure schematic diagram is shown as the rightmost switch in fig. 7, and the main switch is generally a manual switch and is only a single-input isolating switch. Therefore, if the direct current side of the inverter breaks down, the control main switch is turned off, all the photovoltaic group strings connected into the whole combiner box are disconnected, power cannot be generated, the power generation loss is large, the input end of the combiner box is still connected with the photovoltaic group strings, and the circuit disconnection is not realized.
Accordingly, another embodiment of the present invention also provides a junction box including: the controller, the bus bar and at least one multi-path direct current isolating switch provided by the embodiment; in this embodiment, a multi-way dc isolation switch is provided as an example, and a schematic structural diagram of the multi-way dc isolation switch is shown in fig. 8, where:
the multi-path direct current isolating switch is arranged at the front stage of the bus bar; the controller is in communication connection with the control circuit 110 in the multi-path direct current isolating switch and is used for sending a control signal to the control circuit 110 and respectively controlling each photovoltaic group connected with the multi-path direct current isolating switch to be connected into or cut out of the combiner box in series.
Similarly, the sum of the number of the control circuits 110 in all the multi-path dc isolation switches arranged at the front stage of the bus bar of the bus box is greater than 1, and this embodiment is described by taking a multi-path dc isolation switch provided with a plurality of control circuits 110 as an example, and the structure provided with a plurality of multi-path dc isolation switches can be similar and will not be described again.
The controller in the combiner box is an additionally arranged external control chip, such as an MCU (microprogrammed control Unit) and the like. In fact, the junction box further includes: a plurality of fuses and a master switch; the fuses may be respectively disposed at a front stage (not shown) of each switch body 120 in the multi-path dc isolation switch, or may be respectively disposed at a rear stage (shown in fig. 8) of each switch body 120; the main switch is disposed at the rear stage of the bus bar (as shown in fig. 8).
It is worth to say that, this collection flow box still includes: an insulation resistance detection circuit, which is arranged at the bus bar and has a structure diagram as shown in fig. 9, and is used for detecting the insulation resistance to the ground at the bus bar; alternatively, the junction box further includes: a plurality of insulation resistance detection circuits (not shown) provided in the respective branches of the bus bar preceding stage, respectively, for detecting insulation resistance of the respective photovoltaic string.
According to the junction box provided by the embodiment of the invention, as the junction bus is provided with at least one multi-path direct current isolating switch, and the sum of the number of the control circuits 110 in the junction box is greater than 1, a few photovoltaic string containing fault photovoltaic string can be effectively distinguished and turned off, the loss of generated energy is reduced, and the situation that the output sides of all photovoltaic string connected with the junction box are disconnected and the input end of the photovoltaic string is still connected in the prior art can not occur.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
An embodiment of the present invention further provides a photovoltaic system, including: at least one string inverter and a plurality of photovoltaic strings (such as PV panels shown in fig. 4 or fig. 5) at the front stage thereof provided in the above embodiments, the structural schematic diagram of which is shown in fig. 4 or fig. 5; alternatively, the structure of the centralized inverter, at least one combiner box provided in the above embodiment, and a plurality of photovoltaic strings (such as PV panels shown in fig. 10) at the front stage thereof is schematically shown in fig. 10.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
The embodiment of the present invention further provides a control method for a photovoltaic system, which is applied to the photovoltaic system provided in the above embodiment, and a flowchart thereof is shown in fig. 11, where the control method includes:
and S101, controlling the photovoltaic system to start and operate.
In practical application, the photovoltaic system is started to operate, namely all photovoltaic groups connected to a photovoltaic inverter or a combiner box in the photovoltaic system are switched on in series, and the corresponding inverter operates. After the photovoltaic system is started to operate, step S102 is executed.
S102, judging whether a photovoltaic string in the photovoltaic system fails or not.
Wherein, photovoltaic group cluster breaks down and includes: the photovoltaic group string has the problems of arc discharge fault, short circuit, leakage current, overcurrent, overvoltage, ground fault or current reverse fault and the like. Specifically, whether the corresponding photovoltaic string has the above fault or not may be determined by detecting the output voltage/current of each photovoltaic string, or by other methods, where the method for determining whether the photovoltaic string has the fault is the same as that in the prior art, and details are not repeated.
If yes, step S103 is executed.
S103, controlling the opening of a switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the failed photovoltaic group string in the photovoltaic system.
That is, N photovoltaic string including the faulty string are removed from the photovoltaic system, thereby avoiding affecting the output of the normal photovoltaic string. And after the fault disappears, controlling the switch body to be switched on, and recovering the normal operation of the corresponding photovoltaic string.
Preferably, in order to reduce the determination process, if an insulation resistance detection circuit is provided in the photovoltaic system, before step S101 is executed, the following steps are further included, and a flowchart of the method is shown in fig. 12.
S201, according to detected direct current side insulation impedance and alternating current side insulation impedance of the series photovoltaic inverter in the photovoltaic system or ground insulation impedance of a busbar of a combiner box in the photovoltaic system.
S202, judging whether the starting insulation requirement of the photovoltaic system is met.
According to the insulation impedances detected in step S201, it is determined whether the starting insulation requirement of the photovoltaic system is satisfied, that is, whether the insulation impedance of each photovoltaic string satisfies the grid-connected condition, or whether the insulation impedance of some photovoltaic strings is not significantly lower than that of other photovoltaic strings is determined.
If yes, go to step S101.
If it is determined that the start-up insulation requirement of the photovoltaic system is not satisfied according to the dc side insulation resistance of the string-type photovoltaic inverter or the ground insulation resistance of the busbar of the combiner box detected in step S201, as shown in fig. 13, the following step S301 is executed.
S301, controlling all switch bodies in the multi-path direct current isolating switch in the photovoltaic system to be switched off.
S302, sequentially controlling the switch bodies controlled by the control circuits in the multi-path direct current isolating switches to be switched on, and detecting the insulation impedance of the corresponding photovoltaic group strings.
And after all the photovoltaic string groups are determined to be switched off, sequentially controlling the switch bodies controlled by the control circuits in the single multi-channel direct current isolating switch to be switched on, and detecting the ground insulation impedance of each photovoltaic string group.
And S303, controlling the switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the photovoltaic group string with low insulation impedance to be switched off and other switch bodies to be switched on.
After step S303 is executed, that is, after the output of a few photovoltaic strings including a certain or several photovoltaic strings with lower insulation resistance is turned off, the insulation resistance on the dc side and the insulation resistance on the ac side of the string-type photovoltaic inverter in the photovoltaic system or the insulation resistance on the ground of the busbar of the junction box in the photovoltaic system is detected, and if the insulation requirement on the start of the photovoltaic system is met, step S101 is executed.
According to the control method of the photovoltaic system provided by the embodiment, in the grid-connected operation process of the photovoltaic system, after the faulty photovoltaic string is effectively distinguished, all photovoltaic strings controlled by the same control circuit in the multi-path direct current isolation switch corresponding to the faulty photovoltaic string are only turned off, that is, only a small number of photovoltaic strings are removed, so that the loss of the generated energy is reduced; and before the grid-connected operation of the photovoltaic system, the insulation resistance can be detected, and then a small number of photovoltaic strings containing the photovoltaic strings with lower insulation resistance are cut off.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the 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.
In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the 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.
Claims (23)
1. A multi-way DC isolation switch, comprising: at least one control circuit and N switch bodies; n is a positive integer greater than 1; wherein:
the front stage of each switch body is respectively connected with the corresponding photovoltaic group string;
the output end of the control circuit is respectively connected with the control end of each corresponding switch body and used for controlling each corresponding switch body to be disconnected according to the received control signal so as to control each corresponding photovoltaic group string to be disconnected.
2. The multi-path direct current isolation switch according to claim 1, wherein the control circuit is further configured to control each corresponding switch body to be closed according to the received control signal, so as to control serial access of each corresponding photovoltaic group.
3. The multi-channel DC isolating switch as claimed in claim 1, wherein the number of the control circuits is equal to 1, and the output terminals of the control circuits are connected to the control terminals of the N switch bodies.
4. The multiple direct current isolation switch according to any one of claims 1 to 3, wherein the switch body comprises: the controllable switch is arranged on the positive branch of the corresponding photovoltaic string, and/or the controllable switch is arranged on the negative branch of the corresponding photovoltaic string.
5. The multiple dc disconnect switch of any of claims 1-3, further comprising: an operating handle; wherein:
the operating handle is used for manually controlling the on-off of the switch body.
6. The multiple dc disconnect switch of claim 5, further comprising: and the manual switch is used for realizing control right locking of the switch body.
7. A string photovoltaic inverter, comprising: a controller, an inverter circuit and at least one multi-way DC isolator as claimed in any one of claims 1 to 6; wherein:
the multi-path direct-current isolating switches are arranged on the direct-current input side of the string photovoltaic inverter, and the sum of the number of control circuits in all the multi-path direct-current isolating switches is greater than 1;
the controller is used for controlling the working state of the inverter circuit, is in communication connection with each control circuit in the multi-path direct current isolating switch, and sends control signals to each control circuit to respectively control each photovoltaic group string connected with the multi-path direct current isolating switch to be connected into or disconnected from the group string type photovoltaic inverter.
8. The string pv inverter of claim 7, wherein at the dc input side of the string pv inverter there is a respective switch body in at least one branch in which the multiple dc isolators are disposed.
9. The string-type photovoltaic inverter according to claim 8, wherein each of the branches provided with the switch body is connected to at least one of the photovoltaic strings.
10. The string pv inverter of claim 7, further comprising: and the current detection circuits are respectively used for detecting the current of each branch circuit on the direct current input side of the string type photovoltaic inverter.
11. The string pv inverter of claim 7, further comprising: and the insulation resistance detection circuit is used for detecting the insulation resistance on the direct current side and the insulation resistance on the alternating current side of the inverter circuit.
12. The string pv inverter of claim 7, further comprising: a plurality of DC/DC conversion circuits controlled by the controller;
and each DC/DC conversion circuit is respectively arranged between each switch body in the multi-path DC isolating switch and the DC side of the inverter circuit.
13. The string pv inverter of claim 12, further comprising: and a plurality of insulation resistance detection circuits provided at the input terminals of the respective DC/DC conversion circuits.
14. A combiner box, comprising: a controller, a bus bar, and at least one multi-way dc disconnect switch as recited in any one of claims 1-6; wherein:
the multi-path direct current isolating switches are arranged at the front stage of the bus bar, and the sum of the number of control circuits in all the multi-path direct current isolating switches is more than 1;
the controller is in communication connection with each control circuit in the multi-path direct current isolating switch and used for sending control signals to each control circuit and respectively controlling each photovoltaic group connected with the multi-path direct current isolating switch to be connected into or disconnected from the combiner box in a serial mode.
15. The combiner box of claim 14, further comprising: the bus bar pre-stage circuit comprises an insulation resistance detection circuit arranged at a bus bar, or a plurality of insulation resistance detection circuits respectively arranged on each branch of the bus bar pre-stage.
16. The combiner box of claim 14, further comprising: a plurality of fuses; wherein:
the fuses are respectively arranged at the front stage or the rear stage of each switch body in the multi-path direct current isolating switch.
17. The combiner box of claim 14, further comprising: and the main switch is arranged at the rear stage of the bus bar.
18. A photovoltaic system, comprising: a plurality of photovoltaic strings of at least one string inverter and its preceding stage according to any one of claims 7 to 13; or a concentrated inverter, a plurality of photovoltaic strings of at least one combiner box according to any of claims 14-17 and preceding stages thereof.
19. A control method for a photovoltaic system, which is applied to the photovoltaic system according to claim 18, the control method comprising:
after the photovoltaic system is controlled to be started and operated, whether a photovoltaic string in the photovoltaic system fails or not is judged;
and if the judgment result is yes, controlling the switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the failed photovoltaic group string in the photovoltaic system to be switched off.
20. The method for controlling the photovoltaic system according to claim 19, further comprising, after the controlling of the opening of the switch body corresponding to the failed pv string in the multiple dc isolation switches in the photovoltaic system, the steps of:
and after the fault disappears, controlling the switch body to be switched on to enable the corresponding photovoltaic group string to normally operate.
21. The method of controlling a photovoltaic system according to claim 19 or 20, wherein the fault comprises: arcing, short circuit, leakage current, overcurrent, overvoltage, ground fault, or current reversal.
22. The method according to claim 19 or 20, wherein if an insulation resistance detection circuit is provided in the photovoltaic system, before the controlling the photovoltaic system to start operating, the method further comprises:
judging whether the starting insulation requirement of the photovoltaic system is met or not according to the detected direct current side insulation impedance and alternating current side insulation impedance of the series photovoltaic inverter in the photovoltaic system or the ground insulation impedance of a busbar of a combiner box in the photovoltaic system;
and if so, controlling the photovoltaic system to start and operate.
23. The method for controlling a photovoltaic system according to claim 22, wherein after determining whether the start-up insulation requirement of the photovoltaic system is satisfied according to the detected dc-side insulation impedance, ac-side insulation impedance, or ground insulation impedance of the busbar of the combiner box in the photovoltaic system, the method further comprises:
if the starting insulation requirement of the photovoltaic system is judged not to be met according to the detected insulation impedance of the direct current side of the series photovoltaic inverter in the photovoltaic system or the insulation impedance of the ground of a busbar of a combiner box in the photovoltaic system, all switch bodies in a plurality of paths of direct current isolating switches in the photovoltaic system are controlled to be switched off;
sequentially controlling the switch bodies controlled by the control circuits in the multi-path direct current isolating switches to be switched on, and detecting the insulation impedance of the corresponding photovoltaic group strings; and after the switch body controlled by the same control circuit in the multi-path direct current isolating switch corresponding to the photovoltaic group string with low control insulation impedance is switched off and other switch bodies are switched on, if the starting insulation requirement of the photovoltaic system is met, the photovoltaic system is controlled to start and operate.
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| CN202110037640.XA CN112821362A (en) | 2021-01-12 | 2021-01-12 | Multi-path direct-current isolating switch, string type photovoltaic inverter, combiner box, photovoltaic system and control method of photovoltaic system |
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| CN202110037640.XA CN112821362A (en) | 2021-01-12 | 2021-01-12 | Multi-path direct-current isolating switch, string type photovoltaic inverter, combiner box, photovoltaic system and control method of photovoltaic system |
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