CN109149918B - LCL filtering grid-connected inverter protection circuit - Google Patents
LCL filtering grid-connected inverter protection circuit Download PDFInfo
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- CN109149918B CN109149918B CN201811096476.4A CN201811096476A CN109149918B CN 109149918 B CN109149918 B CN 109149918B CN 201811096476 A CN201811096476 A CN 201811096476A CN 109149918 B CN109149918 B CN 109149918B
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- 238000001914 filtration Methods 0.000 title claims abstract description 27
- 239000003990 capacitor Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000009545 invasion Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
Classifications
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Emergency Protection Circuit Devices (AREA)
- Inverter Devices (AREA)
- Protection Of Static Devices (AREA)
Abstract
The invention provides an LCL filtering grid-connected inverter protection circuit, which adopts a double overvoltage protection strategy of an electric power electronic switch and an inverter, designs a set of ZnO piezoresistor for each switch to protect, simultaneously takes the whole inverter as a protection object, and connects a set of ZnO piezoresistor in parallel with an input and output end and a filtering capacitor end of the inverter respectively. When the overvoltage is larger than the voltage-sensitive voltage of the ZnO varistor, the ZnO varistor automatically conducts to restrain the overvoltage. The invention can improve the overvoltage resistance and reliability of the LCL filtering grid-connected inverter, effectively limit the overvoltage caused by input overvoltage, output grounding short-circuit fault and the like, effectively inhibit the overcurrent caused by the overvoltage, and not influence the normal operation of a protection circuit, thereby achieving the purpose of overvoltage protection.
Description
Technical Field
The invention relates to the technical field of overvoltage protection, in particular to a LCL filtering grid-connected inverter protection circuit.
Background
In order to reduce output harmonic content, a filtering link is generally added at the output end of the inverter, and as the LCL filtering has better attenuation effect on higher harmonic components of current when the sizes of the inductors are equal, and the total inductance required by the L filtering is larger than that of the LCL type when the filtering effect is the same, the material cost and the weight volume are improved, so that the LCL filtering technology is more and more widely applied. However, when the ground short circuit fault occurs in the LCL filtering grid-connected inverter, there is a more serious overvoltage problem, and the generated overvoltage has serious threat to the safety of the power electronic switching device used in the inverter and the LCL filter itself.
At present, a buffer circuit is generally connected in parallel to a power electronic switching device to limit the overvoltage in the inverter, but when the output of the LCL filtering grid-connected inverter is in short circuit, and the like, and the external overvoltage occurs, the buffer circuit has the problem of insufficient effective limitation of the external overvoltage.
Disclosure of Invention
In order to solve the problem that when the external overvoltage occurs due to the output grounding short circuit fault and the like of the LCL filtering grid-connected inverter in the prior art, the buffer circuit is insufficient to effectively limit the external overvoltage, the invention provides an LCL filtering grid-connected inverter overvoltage protection method, which adopts the following technical scheme:
An LCL filtering grid-connected inverter protection circuit comprises an inverter and a filter,
Wherein the inverter comprises four power electronic switches S1-S4 of the inverter which are electrically connected with each other;
The filter is an LCL filter and comprises an inverter output side inductor L1, a power grid side inductor L2 and a filter capacitor C1, wherein the inverter output side inductor L1 is arranged at the input end of the LCL filter, and the power grid side inductor L2 is arranged at the output end of the LCL filter;
An inverter output side inductance L1 of an input end of the LCL filter is coupled to the inverter, and a grid side inductance L2 of an output end of the LCL filter is coupled to a grid;
The power electronic switch S1 is connected with a resistor Z2 in parallel, the resistor Z3 is connected with the S2 in parallel, the resistor Z4 is connected with the S3 in parallel, the resistor Z5 is connected with the S4 in parallel, the input end of the inverter is connected with the resistor Z1 in parallel, the output end of the inverter is connected with a resistor Z8 in parallel, the output end of the filter is connected with a resistor Z6 in parallel, and the capacitor end of the filter is connected with a resistor Z7 in parallel.
The LCL filtering grid-connected inverter protection circuit provided by the invention adopts a double overvoltage protection strategy of a power electronic switch and an inverter, designs a set of ZnO piezoresistor for each switch to protect, simultaneously takes the whole inverter as a protection object, respectively connects a set of ZnO piezoresistor in parallel with the input and output ends of the inverter, and automatically conducts the ZnO piezoresistor to inhibit overvoltage when overvoltage is larger than the voltage-sensitive voltage of the ZnO piezoresistor.
The inverter is single-phase or three-phase.
The voltage-sensitive voltage of the ZnO varistor refers to the voltage at two ends of the varistor when passing 1mA current.
The input end of the inverter is provided with a set of ZnO piezoresistor which is connected in parallel between the anode and the cathode of the direct current bus, and the ZnO piezoresistor is used for directly restraining the overvoltage of the input end when the overvoltage occurs at the input end.
When an output grounding short circuit fault occurs, because the grounding short circuit current is very large, serious overvoltage can be generated when the power electronic switch is used for switching on and off the large current, and therefore, a set of ZnO piezoresistors are connected in parallel at two ends of each power electronic switch of the inverter to directly protect power electronics. The residual voltage of the piezoresistor can be increased along with the increase of the current flowing through the piezoresistor, when the input overvoltage is overlarge, the residual voltage of the piezoresistor at the input end can be larger than the tolerance voltage of the power electronic switch, once the residual voltage is larger than the voltage-sensitive voltage of the ZnO piezoresistor connected in parallel on the power electronic switch, the ZnO piezoresistor is conducted to inhibit the residual voltage, and at the moment, the ZnO piezoresistor connected in parallel on the switch and the ZnO piezoresistor connected in parallel with the input end of the inverter form double protection of the input overvoltage.
The output end of the filter is connected with a set of ZnO piezoresistor in parallel, and overvoltage protection is directly carried out on the output end of the inverter. The output end of the inverter is connected with a set of ZnO piezoresistor in parallel, and the ZnO piezoresistor connected with the output end of the filter are connected in parallel to protect the grid-connected inverter, so that the damage of overvoltage on the grid-connected side to the inverter caused by short circuit faults, power grid voltage fluctuation, lightning strike invasion and the like is prevented. The ZnO piezoresistor connected in parallel on the switch and the ZnO piezoresistor connected in parallel at the output end form double protection of external overvoltage such as lightning strike invasion.
The two ends of the filter capacitor are connected with a set of ZnO piezoresistor in parallel, so as to protect the filter capacitor and prevent overvoltage at the grid-connected side. Due to the presence of the filter inductance, a rapid change in current when a short circuit fault occurs induces a large overvoltage which may pose a threat to the filter capacitance.
Preferably, the residual voltage of the ZnO varistor connected in parallel with the power electronic switch is matched with the voltage level of the power electronic switch, and the residual voltage is required to be not larger than the voltage level of the power electronic switch.
Preferably, the residual voltage of the ZnO varistor connected in parallel with the filter capacitor is matched with the withstand voltage of the filter capacitor, and the residual voltage is required to be not larger than the withstand voltage level of the filter capacitor.
Preferably, in order to improve the overvoltage protection capability, the limitation of the rated maximum energy and the heat dissipation capability of the existing single ZnO varistor is overcome, and each set of ZnO varistor can be formed by connecting a plurality of ZnO varistors of the same type in parallel so as to improve the current capacity and the rated maximum energy value.
Preferably, the power electronic switch is an IGBT.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
The invention can improve the overvoltage resistance and reliability of the LCL filtering grid-connected inverter, effectively limit the overvoltage caused by input overvoltage, output grounding short-circuit fault and the like, effectively inhibit the overcurrent caused by the overvoltage, and not influence the normal operation of a protection circuit, thereby achieving the purpose of overvoltage protection.
Drawings
FIG. 1 is a circuit diagram of an LCL filtering grid-connected inverter protection circuit provided by the invention;
FIG. 2 is a schematic diagram of an overvoltage waveform of a power electronic switch when an output ground short circuit fault occurs in a single-phase grid-connected inverter;
Fig. 3 is a schematic diagram of overvoltage protection effect of an IGBT single-phase full-bridge LCL filtering grid-connected inverter in embodiment 2 of the present invention;
S1-S4 are power electronic switches, Z1-Z8 are ZnO piezoresistors, L1 is an inversion side filter inductor, L2 is a grid-connected side filter inductor, C1 is a filter capacitor, and f is an output grounding short circuit fault occurrence point.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, which are only for illustration and not to be construed as limitations of the present patent. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Example 1
An LCL filtering grid-connected inverter protection circuit comprises an inverter and a filter,
Wherein the inverter comprises four power electronic switches S1-S4 of the inverter which are electrically connected with each other;
The filter is an LCL filter and comprises an inverter output side inductor L1, a power grid side inductor L2 and a filter capacitor C1, wherein the inverter output side inductor L1 is arranged at the input end of the LCL filter, and the power grid side inductor L2 is arranged at the output end of the LCL filter;
An inverter output side inductance L1 of an input end of the LCL filter is coupled to the inverter, and a grid side inductance L2 of an output end of the LCL filter is coupled to a grid;
The power electronic switch S1 is connected with a resistor Z2 in parallel, the resistor Z3 is connected with the S2 in parallel, the resistor Z4 is connected with the S3 in parallel, the resistor Z5 is connected with the S4 in parallel, the input end of the inverter is connected with the resistor Z1 in parallel, the output end of the inverter is connected with a resistor Z8 in parallel, the output end of the filter is connected with a resistor Z6 in parallel, and the capacitor end of the filter is connected with a resistor Z7 in parallel.
The LCL filtering grid-connected inverter protection circuit provided by the invention adopts a double overvoltage protection strategy of a power electronic switch and an inverter, designs a set of ZnO piezoresistor for each switch to protect, simultaneously takes the whole inverter as a protection object, respectively connects a set of ZnO piezoresistor in parallel with the input and output ends of the inverter, and automatically conducts the ZnO piezoresistor to inhibit overvoltage when overvoltage is larger than the voltage-sensitive voltage of the ZnO piezoresistor.
Example 2
The LCL filtering grid-connected inverter protection circuit provided by the embodiment adopts a single-phase full-bridge inverter bridge, an inverter bridge switch adopts an IGBT (insulated gate bipolar transistor Insulated Gate Bipolar Transistor), and a filter is LCL type filtering.
Fig. 2 is a schematic diagram of an overvoltage waveform of a power electronic switch when an output ground short-circuit fault occurs in the single-phase grid-connected inverter, the output ground short-circuit fault occurs at time a, and overvoltage which is several times or even tens times higher than normal operation voltage occurs in the power electronic switch.
When overvoltage occurs at the input end of the inverter, the ZnO piezoresistor Z1 is firstly conducted to restrain the overvoltage. If the overvoltage auxiliary value is too large, the residual voltage of the ZnO piezoresistor Z1 is larger than the voltage-sensitive voltage of any ZnO piezoresistor Z2-Z5 connected in parallel at the two ends of the IGBT switch, and the corresponding piezoresistor is conducted to inhibit the overvoltage, so that double protection is formed for the IGBT.
When the output grounding short-circuit fault occurs at the f point of the inverter, due to the fact that the grounding short-circuit current is very large, serious overvoltage is generated when the power electronic switch is used for switching on and off the large current, once the voltage at two ends of any one of the ZnO piezoresistors Z2-Z5 is larger than the voltage-sensitive voltage, the corresponding ZnO piezoresistor is immediately conducted to inhibit the overvoltage, and therefore the IGBT is protected from the overvoltage damage caused by the output grounding short-circuit fault. Meanwhile, when the overvoltage of the loop is larger than the voltage-sensitive voltage of the ZnO piezoresistors Z6, Z7 and Z8, the Z6, Z7 and Z8 are automatically conducted to inhibit the overvoltage. Fig. 3 is a schematic diagram of an overvoltage protection effect of the single-phase full-bridge LCL filtering grid-connected inverter according to embodiment 1 IGBT of the present invention.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (3)
1. The LCL filtering grid-connected inverter protection circuit comprises an inverter and a filter, wherein the inverter comprises four power electronic switches S1, a power electronic switch S2, a power electronic switch S3 and a power electronic switch S4 which are electrically connected with each other;
The filter is an LCL filter and comprises an inverter output side inductor L1, a power grid side inductor L2 and a filter capacitor C1, wherein the inverter output side inductor L1 is arranged at the input end of the LCL filter, and the power grid side inductor L2 is arranged at the output end of the LCL filter;
An inverter output side inductance L1 of an input end of the LCL filter is coupled to the inverter, and a grid side inductance L2 of an output end of the LCL filter is coupled to a grid;
The method is characterized in that: the power electronic switch S1 is connected with a resistor Z2 in parallel, the power electronic switch S2 is connected with a resistor Z3 in parallel, the power electronic switch S3 is connected with a resistor Z4 in parallel, the power electronic switch S4 is connected with a resistor Z5 in parallel, the input end of the inverter is connected with a resistor Z1 in parallel, the output end of the inverter is connected with a resistor Z8 in parallel, the output end of the filter is connected with a resistor Z6 in parallel, and the two ends of a filter capacitor C1 of the filter are connected with a resistor Z7 in parallel;
The resistor Z1, the resistor Z2, the resistor Z3, the resistor Z4, the resistor Z5, the resistor Z6, the resistor Z7 and the resistor Z8 respectively comprise a plurality of ZnO piezoresistors of the same type which are connected in parallel;
The voltage-sensitive voltage of the ZnO varistor is the voltage at two ends of the ZnO varistor when passing 1mA current.
2. The LCL filtered grid-tie inverter protection circuit of claim 1, wherein the inverter is a single-phase inverter or a three-phase inverter.
3. The LCL filtering grid-tie inverter protection circuit of claim 1, wherein the power electronic switch S1, the power electronic switch S2, the power electronic switch S3, and the power electronic switch S4 are IGBTs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811096476.4A CN109149918B (en) | 2018-09-19 | 2018-09-19 | LCL filtering grid-connected inverter protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811096476.4A CN109149918B (en) | 2018-09-19 | 2018-09-19 | LCL filtering grid-connected inverter protection circuit |
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| Publication Number | Publication Date |
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| CN109149918A CN109149918A (en) | 2019-01-04 |
| CN109149918B true CN109149918B (en) | 2024-10-01 |
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| CN204333943U (en) * | 2014-12-30 | 2015-05-13 | 广东电网有限责任公司电力调度控制中心 | A multi-objective short-circuit current fault current limiting device |
| CN209267432U (en) * | 2018-09-19 | 2019-08-16 | 广东电网有限责任公司 | A kind of LCL filtering gird-connected inverter protection circuit |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0592696A1 (en) * | 1992-10-08 | 1994-04-20 | Siemens Aktiengesellschaft | Snubber circuit for an inverter branch |
| EP2568587A1 (en) * | 2011-09-06 | 2013-03-13 | Siemens Aktiengesellschaft | Mains filter for a converter and converter with such a mains filter |
| CN203261231U (en) * | 2013-05-27 | 2013-10-30 | 安徽巨日华电新能源有限公司 | Direct-current filter used for photovoltaic inverter |
| CN104518701A (en) * | 2013-09-27 | 2015-04-15 | 天津市信诺创能科技发展有限公司 | Anti-lightning inverter |
| CN207251486U (en) * | 2017-10-11 | 2018-04-17 | 山西聚星辰制动科技有限公司 | A kind of plasma micro-arc oxidation intermediate frequency power supply |
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2018
- 2018-09-19 CN CN201811096476.4A patent/CN109149918B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN204333943U (en) * | 2014-12-30 | 2015-05-13 | 广东电网有限责任公司电力调度控制中心 | A multi-objective short-circuit current fault current limiting device |
| CN209267432U (en) * | 2018-09-19 | 2019-08-16 | 广东电网有限责任公司 | A kind of LCL filtering gird-connected inverter protection circuit |
Non-Patent Citations (1)
| Title |
|---|
| 舰船推进变频器过电压抑制技术研究;阳开生;船电技术;20170430;第37卷(第4期);第38-42页 * |
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