CN113659533A - Power converter parallel system and energy storage system - Google Patents
Power converter parallel system and energy storage system Download PDFInfo
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- CN113659533A CN113659533A CN202111062891.XA CN202111062891A CN113659533A CN 113659533 A CN113659533 A CN 113659533A CN 202111062891 A CN202111062891 A CN 202111062891A CN 113659533 A CN113659533 A CN 113659533A
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- 238000004146 energy storage Methods 0.000 title claims abstract description 37
- HEZMWWAKWCSUCB-PHDIDXHHSA-N (3R,4R)-3,4-dihydroxycyclohexa-1,5-diene-1-carboxylic acid Chemical compound O[C@@H]1C=CC(C(O)=O)=C[C@H]1O HEZMWWAKWCSUCB-PHDIDXHHSA-N 0.000 claims description 11
- 238000001514 detection method Methods 0.000 claims description 7
- 238000010248 power generation Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 description 8
- 230000002457 bidirectional effect Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 3
- 238000007664 blowing Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—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 for converters; for rectifiers
- H02H7/12—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 for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—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 for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02H7/10—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 for converters; for rectifiers
- H02H7/12—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 for converters; for rectifiers for static converters or rectifiers
- H02H7/122—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 for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
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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
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides an energy storage system and power converter parallel system, which comprises at least two power converters, wherein each power converter at least has a parallel point on a direct current side; moreover, a converter disconnection protection circuit is arranged between the direct current side of each power converter and the corresponding parallel point; the converter disconnection protection circuit comprises a fusing device and an electronic switch which are connected in series; when overcurrent faults of equipment or lines occur on one side of any converter disconnection protection circuit connected with the corresponding power converter, the internal fusing device of the converter disconnection protection circuit is in a disconnection state, and electronic switches in other converter disconnection protection circuits are in a disconnection state; and then each power converter in the power converter parallel system can be disconnected, and the protection of each parallel device is realized. When the power converter parallel system is applied to an energy storage system, the protection of each energy storage converter and a preceding battery system thereof can be realized.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a power converter parallel system and an energy storage system.
Background
In an energy storage system, a plurality of energy storage converters are usually used for realizing power conversion by combining ac and dc, and if any one of the energy storage converters fails, a battery on a dc side may fail, or other energy storage converters connected in parallel fail, so that the system is broken down and a safety accident is caused.
Therefore, in the energy storage system, it is very critical to quickly disconnect a failed energy storage converter or quickly cut off the battery and all the energy storage converters in case of failure, and the prior art cannot realize effective disconnection.
Disclosure of Invention
In view of the above, the present invention provides a parallel power converter system and an energy storage system to achieve effective disconnection between parallel devices in case of a fault.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
a first aspect of the present invention provides a power converter parallel system, comprising: at least two power converters, each of which has a parallel point at least on the dc side; a converter disconnection protection circuit is arranged between the direct current side of each power converter and the corresponding parallel point;
the converter disconnection protection circuit includes: a fuse device and an electronic switch connected in series;
when an equipment or line overcurrent fault occurs on one side of any converter disconnection protection circuit connected with the corresponding power converter, the fusing device in the converter disconnection protection circuit is in a disconnected state, and the electronic switches in the other converter disconnection protection circuits are in a disconnected state.
Optionally, when an equipment or line overcurrent fault occurs on one side of at least one of the converter disconnection protection circuits connected to the corresponding parallel point, the electronic switches in each of the converter disconnection protection circuits are all in a disconnected state.
Optionally, the converter disconnection protection circuit further includes: current detection means for detecting a direct-current side current of the corresponding power converter;
when the direct current side current of the power converter flows to the corresponding parallel point and is greater than a preset value, the electronic switch is in an off state.
Optionally, the electronic switch is: a switch tube with a diode or an anti-parallel diode;
and the body diode and the anti-parallel diode are used for transmitting the electric energy at the corresponding parallel point to the direct current side of the corresponding power converter.
Optionally, the fusing device is a fuse, and the fusing speed of the fusing device is greater than the fusing speed of a fuse in a power supply connected to the corresponding parallel point.
Optionally, one end of the fusing device, which is far away from the electronic switch, is used for connecting one pole of the corresponding parallel point;
and one end of the electronic switch, which is far away from the fusing device, is used for connecting the same pole of the direct current side of the power converter connected with the electronic switch.
Optionally, the converter disconnection protection circuit further includes: a flow continuing device;
when the fusing device and the electronic switch are arranged on the positive pole of the corresponding power converter, the input end of the follow current device is connected with the negative pole of the direct current side of the corresponding power converter, and the output end of the follow current device is connected with the connection point of the fusing device and the electronic switch;
when the fusing device and the electronic switch are arranged on the negative electrode of the corresponding power converter, the input end of the follow current device is connected with the connecting point of the fusing device and the electronic switch, and the output end of the follow current device is connected with the positive electrode of the direct current side of the corresponding power converter.
Optionally, the freewheeling device includes: a diode;
after the fusing device is in the off state, the corresponding current follow current path is as follows: the electronic switch, the DC side of the power converter, and the diode;
after the electronic switch is in an off state, the corresponding current follow current path is as follows: the fusing device, the corresponding parallel point and the diode.
Optionally, the freewheeling device further includes: a current limiting resistor connected in series with the diode.
Optionally, each converter disconnection protection circuit and the corresponding parallel point are further provided with: and the decoupling device is used for realizing the direct current side decoupling of each power converter.
Optionally, the power converter is: a DCDC converter and/or a DCAC converter.
Optionally, the power supply connected to the corresponding parallel point includes: a battery system or a photovoltaic array.
The second aspect of the present invention also provides an energy storage system, including: a battery system and a power converter parallel system as described in any of the preceding paragraphs with respect to the first aspect;
and the parallel connection point of each power converter on the direct current side in the power converter parallel system is connected with the battery system.
Optionally, the power converter is an energy storage converter, and a parallel point of each energy storage converter on the ac side is used for connecting a power grid and/or a load; or,
the power converters are DCDC converters, and the parallel connection point of each DCDC converter on the other side is used for connecting a direct current bus of the new energy power generation system.
The invention provides a power converter parallel system which comprises at least two power converters, wherein each power converter at least has a parallel point on a direct current side; moreover, a converter disconnection protection circuit is arranged between the direct current side of each power converter and the corresponding parallel point; the converter disconnection protection circuit comprises a fusing device and an electronic switch which are connected in series; when overcurrent faults of equipment or lines occur on one side of any converter disconnection protection circuit connected with the corresponding power converter, the internal fusing device of the converter disconnection protection circuit is in a disconnection state, and electronic switches in other converter disconnection protection circuits are in a disconnection state; and then each power converter in the power converter parallel system can be disconnected, and the protection of each parallel device is realized. When the power converter parallel system is applied to an energy storage system, the protection of each energy storage converter and a preceding battery system thereof can be realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the description of the embodiments or the prior art will be briefly introduced 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 parallel power converter system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a converter disconnection protection circuit according to an embodiment of the present invention;
fig. 3 and fig. 4 are schematic diagrams of two current paths of a parallel system of power converters according to an embodiment of the present invention;
fig. 5 and fig. 6 are schematic diagrams of two structures of a converter disconnection protection circuit according to an embodiment of the present invention;
fig. 7a, fig. 7b, fig. 8a and fig. 8b are schematic diagrams of four current paths of a power converter parallel system according to an 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 invention provides a parallel system of power converters to achieve effective disconnection between parallel devices in the event of a fault.
As shown in fig. 1, the power converter parallel system includes at least two power converters, two of which are shown in fig. 1 as an example; each power converter has a parallel point at least on the direct current side, and the other side of each power converter can be independent (as shown in fig. 1) or have another corresponding parallel point; the power converter can be a DCDC converter, a DCAC converter or a series structure of the DCDC converter and the DCAC converter, and the power converter is determined according to the specific application environment and is within the protection scope of the application; fig. 1 shows an example of a DCAC converter, which is suitable for a scenario where energy storage converters in an energy storage system are connected in parallel on multiple dc sides or in parallel between ac and dc. In addition, two sides of each power converter may be directly connected in parallel, or may be connected in parallel through corresponding other devices, for example, the dc side of each power converter may be connected in parallel after the protection circuit 100 and the decoupling device are disconnected by the following converter, and the other side of each power converter may be connected in parallel through a corresponding transformer, depending on the specific application environment, which is within the protection scope of the present application.
Moreover, a converter disconnection protection circuit 100 is respectively arranged between the direct current side of each power converter and the corresponding parallel point of the direct current side; that is, the dc side of each power converter is connected to the parallel point of the dc side by its converter disconnection protection circuit 100; the direct current power supply connected with the parallel point of the direct current side can be a battery system or a photovoltaic array, and the direct current power supply is determined according to the specific application environment and is within the protection range of the application. Specifically, referring to fig. 2, the converter disconnection protection circuit 100 includes: a fuse device 101 and an electronic switch 102 connected in series. Wherein:
when an overcurrent fault occurs in a device or line on one side of any converter disconnection protection circuit 100 connected with a corresponding power converter, for example, when a short-circuit fault or an overcurrent fault occurs in the corresponding power converter, or when a short-circuit fault occurs between the positive pole and the negative pole of any section of line on the direct current side of the corresponding power converter, the fuse device 101 in the converter disconnection protection circuit 100 is in a disconnected state, and the other converter disconnection protection circuits 100 are in a disconnected state by the electronic switches 102 in the converter disconnection protection circuits, so that the function of disconnecting the direct current side of each power converter from the corresponding parallel point is realized.
Taking two DCAC converters respectively connected in parallel at two sides as an example, fig. 3 shows the case when an equipment or line overcurrent fault occurs at the converter side where the first converter opens the protection circuit 100, the dotted line frame indicates the position of the fault, and each dotted line with an arrow indicates the current direction on the corresponding line in this case.
At this time, the dc power supply will disconnect the protection circuit 100 through the converter connected to the dc side of the first DCAC converter, outputting a current to the fault location; the second DCAC converter also outputs a current to the fault location by disconnecting the protection circuit 100 from the converter connected to the second DCAC converter, the parallel point on the dc side, and the other converter disconnecting the protection circuit 100; the current on the converter disconnection protection circuit 100 connected to the direct current side of the first DCAC converter is increased, and when the current exceeds the bearing capacity of the internal fuse device 101, the fuse device 101 fuses, so that the current path of the fault position is cut off, the overcurrent damage of corresponding devices in the first DCAC converter is avoided, and the protection of the first DCAC converter is realized. In addition, at this time, the directions of the direct-current side currents of the two DCAC converters are opposite, and even when the direct-current power supply is a battery system and the battery system is charging, the direct-current side current of the second DCAC converter is larger than the charging current in a normal state, so that the converter connected to the second DCAC converter can be controlled to disconnect the electronic switch 102 in the protection circuit 100, and the connection between the two sides is disconnected, thereby realizing the protection of the second DCAC converter. In addition, the two converters disconnect the protection circuit 100, so that the right side of the parallel point on the direct current side is not connected, and the influence of the short-circuit fault on the direct current power supply is avoided.
As can be seen from the above, the parallel power converter system provided in this embodiment can not only quickly disconnect a failed power converter, but also remove all other power converter pre-stages and dc power supplies to protect each power converter and dc power supply when a device or line fault occurs on the converter side of any converter disconnection protection circuit, such as a power converter failure. When the power converter parallel system is applied to an energy storage system, the battery system and each energy storage converter can be protected.
In addition, when an equipment or line overcurrent fault occurs on one side of at least one converter disconnection protection circuit 100 connected to a corresponding parallel point, for example, a short-circuit fault occurs on the parallel point, or a short-circuit fault occurs on a power supply connected to the parallel point, or a short-circuit fault occurs between a positive electrode and a negative electrode of a line on the power supply side of any converter disconnection protection circuit 100, at this time, the electronic switch 102 in each converter disconnection protection circuit 100 is in a disconnected state.
Still taking two DCAC converters with two sides respectively connected in parallel as an example, fig. 4 shows a situation when a short-circuit fault occurs at a parallel point on the dc sides of the two DCAC converters, a dashed box indicates a position where the short-circuit fault occurs, and each dashed line with an arrow indicates a current direction on a corresponding line in this situation.
At this time, both the DCAC converters output current to the parallel point on the dc side, and if the dc power source connected to the parallel point is a photovoltaic array or the dc power source is a battery system and the battery system is discharging, the direction of the current on the dc side of both the DCAC converters is opposite to the normal state, so that the electronic switches 102 in the protection circuit 100 can be controlled to be turned off to disconnect the connection of both sides of the converter, thereby protecting both the DCAC converters and the dc power source. If the dc power source connected to the parallel point is a battery system and the battery system is charging, although the direction of the dc side currents of the two DCAC converters is the same as the normal condition, because the parallel point has a short-circuit fault, both currents are greater than the currents in the normal condition, so the two converters can be controlled to disconnect the electronic switches 102 in the protection circuit 100 to disconnect the connections of the two sides thereof, thereby implementing corresponding protection.
On the basis of the above embodiment, it should be noted that, in practical applications, the detection of the dc side current of each power converter can be realized by using the original current detection device on the dc side of each power converter, and the detection is matched with the control of each electronic switch 102; however, when each power converter does not originally have a current detection device on the dc side, a current detection device 103 (as shown in fig. 5) may be additionally disposed in the converter disconnection protection circuit 100 to detect the dc side current of the corresponding power converter; and, when the current on the dc side of the corresponding power converter flows to the corresponding parallel point and is greater than the preset value, the corresponding electronic switch 102 is controlled to be in the off state.
For the cases shown in fig. 2 to 4, it can be assumed that a larger value of the dc-side current from right to left is the preset value, and then:
when the direct current power supply is a photovoltaic array, the direct current side current under the normal condition is from left to right; once the detected direct-current side current flows from right to left, that is, an equipment or line overcurrent fault occurs on the power supply side of any converter disconnection protection circuit 100 or the converter sides of other converters except the converter disconnection protection circuit 100, and the current value of the equipment or line overcurrent fault is greater than the preset value, the corresponding electronic switch 102 can be controlled to be switched off.
When the dc power supply is a battery system, the situation during discharging is similar to that of the photovoltaic array, and is not described again.
When the dc power supply is a battery system, and during charging, the current on the dc side under normal conditions also flows from right to left, but is less than or equal to the preset value, and when an overcurrent fault occurs on the power supply side of any converter disconnecting protection circuit 100 or the converter sides of other converters except the converter disconnecting protection circuit 100, the current on the dc side is greater than the preset value, so as to control the corresponding electronic switch 102 to be disconnected.
On the basis of the above embodiment, preferably, as shown in fig. 5, the electronic switch 102 may be: a switching tube T1 with a body diode or an anti-parallel diode, such as a MOS tube; and the body diode or the anti-parallel diode is used for transmitting the electric energy at the corresponding parallel point to the direct current side of the corresponding power converter.
Still taking two DCAC converters respectively connected in parallel at two sides as an example, fig. 7a shows a case when a short-circuit fault occurs in a first DCAC converter, fig. 8a shows a case when a short-circuit fault occurs in a parallel connection point on a direct current side of the two DCAC converters, a position where the short-circuit fault occurs is indicated in a dashed box, and each segment of dashed line with an arrow indicates a current direction on a corresponding line in the case.
If the dc power supply is a photovoltaic array, under normal conditions, each switching tube T1 is in a normally-on state, and the dc power supply outputs electric energy through each switching tube T1 body or each switching tube T1 and its reverse parallel diode, or certainly through each switching tube T1 body. If the direct-current power supply is a battery system, the battery system can always switch the charging and discharging modes, so that each switching tube T1 can be controlled to be in a normally-on state, and the control logic is simple and easy to implement; that is, normally, each switch tube T1 is also in a normally-on state, and the dc power source discharges through the body of each switch tube T1 or each switch tube T1 and its reverse parallel diode, or the dc power source charges through each switch tube T1.
When the short-circuit fault condition shown in fig. 7a occurs, the fuse 101 in the converter disconnection protection circuit 100 connected to the dc side of the first DCAC converter blows, the switching tube T1 in the converter disconnection protection circuit 100 connected to the second DCAC converter switches to the off state, and the body diode or the anti-parallel diode thereof is turned on only in the forward direction and turned off in the reverse direction, so that the disconnection function of the electronic switch 102 can be realized. When the short-circuit fault condition shown in fig. 8a occurs, the switching tubes T1 in the two DCAC converters are both switched to the off state, and the body diodes or the anti-parallel diodes thereof are turned off in the opposite direction, so that the turn-off function of the corresponding electronic switches 102 can be realized.
In this embodiment, the bidirectional conduction function and the overcurrent protection function of the electronic switch 102 are realized through the switching tube T1 and the body diode or the anti-parallel diode thereof, and the electronic switch has a simple structure, low loss and a small volume.
Additionally, the blowing device 101 may be a FUSE, as shown in FIGS. 5-8 b; when the dc power supply also has a FUSE therein, such as a battery system, the fusing speed of the FUSE needs to be faster than the fusing speed of the FUSE in the battery system, so as to ensure that the FUSE can be operated before the FUSE in the battery system is fused, thereby protecting the battery system.
On the basis of the above embodiments, the positions of the fusing device 101 and the electronic switch 102 in the converter disconnection protection circuit 100 can be arbitrarily selected, and can be one at the positive pole, one at the negative pole, or both at the positive pole and the negative pole, and the front and back order is not limited at the same time, and can be determined according to the specific application environment, as long as the above functions can be realized; more preferably, however, both are arranged on the same pole with the fuse 101 near the parallel point and the electronic switch 102 near the power converter; for example, one end of the fusing device 101, which is far away from the electronic switch 102, is used for connecting the positive poles of the corresponding parallel points; and the electronic switch 102 is located at an end away from the fuse 101, and is used for connecting the dc side positive electrode of the power converter connected thereto. That is, as shown in fig. 2 to 5, the corresponding power converter is connected from the positive pole of the parallel point on the dc side, first through the fuse 101, and then through the electronic switch 102.
At this time, referring to fig. 6 (which is illustrated on the basis of fig. 5 as an example), the converter disconnection protection circuit 100 further includes: a freewheel device 104; the input end of the follow current device 104 is connected with the negative pole of the direct current side of the corresponding power converter, and the output end of the follow current device 104 is connected with the connection point of the fusing device 101 and the electronic switch 102.
In practice, the freewheeling device 104 may be a diode, such as D1 shown in fig. 6. The anode of the diode D1 serves as the input of the corresponding freewheel 104, and the cathode of the diode D1 serves as the output of the corresponding freewheel 104.
Still taking two DCAC converters with two sides respectively connected in parallel as an example, for the case of short-circuit fault of the first DCAC converter shown in fig. 7a, when the fuse 101 in the first converter disconnection protection circuit 100 is fused and the electronic switch 102 in the second converter disconnection protection circuit 100 is disconnected, due to the existence of the freewheeling device 104, the current freewheeling path in the first converter disconnection protection circuit 100 is: electronic switch 102, the dc side of the power converter and diode D1, the current freewheel path in the second converter open protection circuit 100 is: the fuse 101, corresponding shunt point and diode D1, the free-wheeling path in the two converter open protection circuit 100 is shown by the dotted line with arrows in fig. 7b, thereby reducing the stress on the switch T1 in the second converter open protection circuit 100.
In the case of a short-circuit fault at the parallel connection point on the dc side of the two DCAC converters shown in fig. 8a, after the two electronic switches 102 are both turned off, the current freewheeling paths in the two converter turn-off protection circuits 100 are both: the fuse device 101, the corresponding parallel connection point and the diode D1, as shown by the dotted line with an arrow in fig. 7b, reduce the stress on the two switching tubes T1.
It should be noted that, because the stray inductance of the external connection of the converter disconnection protection circuit 100 cannot be confirmed, for example, in a system in which the dc sides of a plurality of power converters are connected in parallel, especially in a scenario in which energy storage converters in an energy storage system are connected in parallel in multiple alternating currents and direct currents, the dc side of each power converter is usually provided with a decoupling device (as shown in fig. 6) to achieve decoupling of the dc side; this situation increases the line noise and increases the stress when the switching device (e.g., the electronic switch 102) in the converter open protection circuit 100 is turned off. If the extra absorbing device is added to absorb the energy when the bidirectional switch is turned off, the absorbing device usually needs to be composed of a voltage dependent resistor, a discharge tube and other devices, so that the cost is high and the reliability is low. The converter disconnection protection circuit 100 provided in this embodiment utilizes the freewheeling diode D1 to reduce the stress of the switching transistor T1, thereby achieving low cost and high reliability.
That is, when the converter disconnection protection circuit 100 is applied to a scene in which multiple sets of energy storage converters in an energy storage system are connected in parallel on the direct current side or in parallel on the alternating current side and the direct current side, the energy storage converters can be quickly disconnected when the battery side and the energy storage converters are short-circuited, and the system reliability is improved; moreover, by adding the follow current loop, the turn-off stress of the electronic switch is small, the loss of the electronic switch arranged in a unidirectional mode is small, and the efficiency of the whole machine is improved; in addition, each energy storage converter can be additionally provided with a decoupling device, so that the decoupling of the direct parallel machine is realized.
In practical applications, an end of the fuse device 101 away from the electronic switch 102 may be configured to connect to the negative electrode of the corresponding parallel point, and an end of the electronic switch 102 away from the fuse device 101 may be configured to connect to the negative electrode of the dc side of the power converter connected thereto. At this time, the input end of the freewheeling device 104 is connected to the connection point of the fuse 101 and the electronic switch 102, and the output end of the freewheeling device 104 is connected to the dc side anode of the corresponding power converter.
In addition, a corresponding current limiting resistor can be arranged in the freewheeling device 104 for the diode D1 to protect the diode D1; in the flywheel device 104, a current limiting resistor may be connected in series with the diode D1, and the connection order is not limited.
In addition, for each of the above embodiments, in practical applications, the parallel connection point of each power converter on the dc side may be connected to the photovoltaic array, and in this case, the power converter parallel system is applied to a photovoltaic power generation system, and each power converter may be a unidirectional converter. The parallel connection point of each power converter on the direct current side can also be connected with a battery system, in this case, each power converter needs to be a bidirectional converter, and the fusing speed of the fusing device 101 in the converter disconnection protection circuit 100 is greater than the fusing speed of a fuse in the battery system.
Another embodiment of the present invention further provides an energy storage system, including: a battery system and a power converter parallel system as described in any of the above embodiments; the structure and the operation principle of the parallel system of the power converter can be obtained by referring to the above embodiments, and are not described again.
The parallel connection point of each power converter on the direct current side in the power converter parallel system is connected with the battery system; the other side of each power converter can be respectively connected with corresponding external equipment, and can also be connected with unified external equipment through corresponding parallel points on the other side.
Optionally, the power converter is an energy storage converter, such as a single-stage bidirectional DCAC converter, or a two-stage converter formed by a bidirectional DCDC converter and a bidirectional DCAC converter; the parallel connection point of the energy storage converters on the alternating current side is used for connecting a power grid and/or a load.
Alternatively, the power converter may also be a DCDC converter, and a parallel point of each DCDC converter on the other side is used for connecting a direct current bus of a new energy power generation system, such as a direct current bus of a photovoltaic power generation system or a wind power generation system, and is within the protection scope of the present application.
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 (14)
1. A power converter parallel system, comprising: at least two power converters, each of which has a parallel point at least on the dc side; a converter disconnection protection circuit is arranged between the direct current side of each power converter and the corresponding parallel point;
the converter disconnection protection circuit includes: a fuse device and an electronic switch connected in series;
when an equipment or line overcurrent fault occurs on one side of any converter disconnection protection circuit connected with the corresponding power converter, the fusing device in the converter disconnection protection circuit is in a disconnected state, and the electronic switches in the other converter disconnection protection circuits are in a disconnected state.
2. The power converter parallel system of claim 1, wherein the electronic switch within each of the converter open protection circuits is in an open state when an equipment or line overcurrent fault occurs on the side of at least one of the converter open protection circuits connecting the respective parallel points.
3. The power converter parallel system of claim 1 or 2, wherein the converter disconnect protection circuit further comprises: current detection means for detecting a direct-current side current of the corresponding power converter;
when the direct current side current of the power converter flows to the corresponding parallel point and is greater than a preset value, the electronic switch is in an off state.
4. The power converter parallel system of claim 1 or 2, wherein the electronic switch is: a switch tube with a diode or an anti-parallel diode;
and the body diode and the anti-parallel diode are used for transmitting the electric energy at the corresponding parallel point to the direct current side of the corresponding power converter.
5. The power converter parallel system according to claim 1 or 2, wherein the fusing device is a fuse and has a fusing speed greater than that of a fuse in a power supply connected to the corresponding parallel point.
6. The parallel power converter system according to claim 1 or 2, wherein the fuse device is located at an end away from the electronic switch, and is used for connecting one pole of the corresponding parallel point;
and one end of the electronic switch, which is far away from the fusing device, is used for connecting the same pole of the direct current side of the power converter connected with the electronic switch.
7. The power converter parallel system of claim 1 or 2, wherein the converter disconnect protection circuit further comprises: a flow continuing device;
when the fusing device and the electronic switch are arranged on the positive pole of the corresponding power converter, the input end of the follow current device is connected with the negative pole of the direct current side of the corresponding power converter, and the output end of the follow current device is connected with the connection point of the fusing device and the electronic switch;
when the fusing device and the electronic switch are arranged on the negative electrode of the corresponding power converter, the input end of the follow current device is connected with the connecting point of the fusing device and the electronic switch, and the output end of the follow current device is connected with the positive electrode of the direct current side of the corresponding power converter.
8. The power converter parallel system of claim 7, wherein the freewheeling device comprises: a diode;
after the fusing device is in the off state, the corresponding current follow current path is as follows: the electronic switch, the DC side of the power converter, and the diode;
after the electronic switch is in an off state, the corresponding current follow current path is as follows: the fusing device, the corresponding parallel point and the diode.
9. The parallel power converter system of claim 8, further comprising in the freewheeling device: a current limiting resistor connected in series with the diode.
10. The parallel power converter system of claim 7, wherein each of said converter open protection circuits is further configured to have disposed between it and its corresponding parallel point: and the decoupling device is used for realizing the direct current side decoupling of each power converter.
11. The power converter parallel system according to claim 1 or 2, wherein the power converter is: a DCDC converter and/or a DCAC converter.
12. A power converter parallel system according to claim 1 or 2, wherein the power supply to which the respective parallel points are connected comprises: a battery system or a photovoltaic array.
13. An energy storage system, comprising: a battery system and a power converter parallel system according to any of claims 1-12;
and the parallel connection point of each power converter on the direct current side in the power converter parallel system is connected with the battery system.
14. The energy storage system of claim 13, wherein the power converters are energy storage converters, and a parallel connection point of each energy storage converter on the ac side is used for connecting a grid and/or a load; or,
the power converters are DCDC converters, and the parallel connection point of each DCDC converter on the other side is used for connecting a direct current bus of the new energy power generation system.
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