CN202870229U - Leakage current detection and protection circuit - Google Patents
Leakage current detection and protection circuit Download PDFInfo
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- CN202870229U CN202870229U CN 201220514335 CN201220514335U CN202870229U CN 202870229 U CN202870229 U CN 202870229U CN 201220514335 CN201220514335 CN 201220514335 CN 201220514335 U CN201220514335 U CN 201220514335U CN 202870229 U CN202870229 U CN 202870229U
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Abstract
The utility model relates to a leakage current detection and protection circuit which comprises a magnetic core, a sensing circuit, a filtering and amplifying circuit, a bias circuit and a detection circuit, wherein the sensing circuit comprises a self-excited oscillation circuit and a sampling circuit, the sensing circuit is connected with the magnetic core, the filtering and amplifying circuit is connected with the sensing circuit, the bias circuit and the sensing circuit are connected with the filtering and amplifying circuit, and the detection circuit is connected with the filtering and amplifying circuit. The leakage current detection and protection circuit can be used to suppress and eliminate leakage currents of different frequencies and different sizes, has a wide working range, is less affected by the environment, is applicable to transformerless photovoltaic systems and is high in sampling precision, stable in performance and lower in cost.
Description
Technical field
The utility model relates to a kind of holding circuit, particularly a kind of leakage current test holding circuit that belongs to the photovoltaic combining inverter technical field.
Background technology
People are increasing to the demand of the energy in recent years, and are also more and more higher to energy-conservation requirement.Sun power has broad application prospects as a kind of regenerative resource of cleaning, and grid-connected photovoltaic system will become a kind of trend.The normal isolated form photovoltaic combining inverter that adopts with power frequency or high-frequency transformer has been guaranteed the electrical isolation between electrical network and the photovoltaic system like this in the photovoltaic parallel in system, thereby improves personnel protection and avoided leakage current between photovoltaic system and the ground.Yet if adopt the power frequency transformation, its volume is large, heavy and expensive; If the employing high-frequency transformer, power conversion circuit will be divided into several grades, so that control complicatedly, reduce simultaneously the efficient of system.In order to overcome the above-mentioned deficiency that the isolation type grid-connected system of transformer is arranged, need the transformerless non-isolation type inverter topology of research.An outstanding advantages of transformerless photovoltaic combining inverter is the efficient that can improve total system.This has very large attractive force for the higher photovoltaic parallel in system of cost of electricity-generating, therefore the miniwatt inverter overwhelming majority adopts the transless topological structure at present, yet in transformerless non-isolation type photovoltaic parallel in system, there is directly electrical connection between electrical network and the photovoltaic array, owing to have stray capacitance between photovoltaic array and the ground, thereby formed the common mode resonance loop that is formed by stray capacitance, filter element and electric network impedance.Thereby the common mode voltage that changes on the stray capacitance then can encourage this resonant tank to produce corresponding common mode leakage current, i.e. leakage current.Because the area of photovoltaic cell is larger, parasitic capacitance value over the ground is issued to 200nF/kpw in rainy day or moist environment, and the common mode current of generation may surpass the scope that allows.Studies show that: in order to suppress leakage current, can consider to improve the topological structure of combining inverter or adopt suitable adjustment strategy.Existing leak current detection device mainly is comprised of three parts such as difference current converter, subsequent process circuit and physical constructions.Wherein, be the difference current converter for detection of the part of leakage current, comprise the magnetic core of a circle or rectangle, be full of the fine copper wire of hundreds of circles on the magnetic core; All current bus bar rows pass in the middle of magnetic core.In the situation that does not have leakage current, pass all current phasors of magnetic core and be zero, so based on Ampère circuital theorem as can be known, do not exist magnetic flux in the magnetic core this moment; If there is leakage current, current phasor and with non-vanishing so, simultaneously, leakage current will cause occurring in the magnetic core variable magnetic flux; Further, this variable magnetic flux will cause occurring in the coil induction electromotive force.Subsequent process circuit is processed and is analyzed the induction electromotive force in the coil,, then cuts off the electricity supply by the Crush trigger structure, with the execute protection function greater than predefined threshold value if analysis result shows current leakage current.Consider that leakage current is usually less, so the higher permalloy of magnetic core employing cost, this is because the relative permeability of permalloy is larger, meeting is convenient to process and analyze so that the induction electromotive force in the coil increases, otherwise, if induction electromotive force is too small, rear extended meeting is difficult to process.
As seen, although existing detection method can detect the leakage current in the certain limit,, owing to need to use the permalloy magnetic material, perhaps adopt the leakage current test module that is specifically designed to photovoltaic industry on the market, thereby increase complexity and the cost of realizing.And, owing to only have alternating current in coil, to produce induction electromotive force, and therefore, the inapplicable and detection DC leakage current of existing detection method.Have, existing detection mode is not used yet and is detected the larger leakage current with upper frequency again, and the larger leakage current that therefore has upper frequency can cause occurring eddy current in the coil, and then causes testing result inaccurate.
Summary of the invention
Technical matters to be solved by this invention is, if provide a kind of Real-Time Monitoring leakage current, the high leakage current of accuracy of detection can fast inverter be cut off a kind of leakage current detection circuit of electrical network when surpassing preset value.
For solving the problems of the technologies described above; the present invention is by the following technical solutions: a kind of leakage current test holding circuit; it is characterized in that comprising magnetic core; sensing circuit; filtering and amplifying circuit; biasing circuit and testing circuit; described sensing circuit comprises the self-oscillation circuit; sample circuit; the magnetic induction density in described self-oscillation electric circuit inspection magnetic field; described sample circuit changes into voltage signal with sensor current signal; described self-oscillation circuit is connected with sample circuit; described filtering and amplifying circuit filtered voltage signal medium-high frequency composition also carry out signal and amplify; described biasing circuit is collected amplifying signal and is carried out absolute value and just get; described testing circuit is processed the data that collect and is judged whether to reach the protection threshold value; described sensing circuit is connected with magnetic core; described filtering is connected with sensing circuit with amplifying circuit; described biasing circuit is connected with amplifying circuit with filtering with sensing circuit, and described testing circuit is connected with amplifying circuit with filtering.
As a kind of improvement, also include L, the N line of grid-connected inverters end, the L of grid-connected inverters end, N line pass from magnetic core.
As a kind of improvement, described magnetic core is circular and adopts Ferrite Material.
As a kind of improvement, described filtering and amplifying circuit are provided with the two-stage low-pass filter.
The utility model can suppress the leakage current of different frequency, different sizes and eliminate, and working range is wide, and is affected by environment less, is applicable to the transless photovoltaic system, and sampling precision is high, stable performance, and can reduce cost.
Description of drawings
Fig. 1 is the structured flowchart of a kind of leakage current test holding circuit of the utility model.
Embodiment
As shown in Figure 1; a kind of embodiment of leakage current test holding circuit; comprise magnetic core 1; sensing circuit 2; filtering and amplifying circuit 3; biasing circuit 4 and testing circuit 5; described sensing circuit 2 comprises the self-oscillation circuit; sample circuit; the magnetic induction density in described self-oscillation electric circuit inspection magnetic field; described sample circuit changes into voltage signal with sensor current signal; described self-oscillation circuit is connected with sample circuit; described filtering and amplifying circuit 3 filtered voltage signal medium-high frequency compositions also carry out signal and amplify; the leakage current composition comprises DC quantity and of ac; wherein the of ac first-harmonic is 50Hz and contains radio-frequency component; therefore adopt butterworth filter to come the high frequency portioning of filtering sensing array output; carrying out simultaneously signal amplifies and to be convenient to testing circuit and to gather described biasing circuit 4 and collect amplifying signals and carry out absolute value and just get; process the data that collect and judge whether to reach the protection threshold value to make things convenient for cpu in the testing circuit 5 to read described testing circuit 5; described sensing circuit 2 is connected with magnetic core; described filtering is connected with sensing circuit 2 with amplifying circuit 3; described biasing circuit is connected with amplifying circuit 3 with filtering with sensing circuit 2, and described testing circuit 5 is connected with amplifying circuit 3 with filtering.After the utility model adopts above structure, comprise following advantage:
1) cross section of magnetic core 1 need not to do very greatly, and the material of making magnetic core is iron material, therefore not only can dwindle the volume of whole leakage current test holding circuit, and reduce use cost;
2) only need a sensing circuit, the leakage current in can detecting from 30mA to the 300mA scope has enlarged the sensing range of leakage current;
3) detect the interior leakage current of very large bandwidth range, from the direct current to the high-frequency ac, that is to say that the described scheme of utility model not only can detect of ac, and can detect DC quantity, and can not produce eddy current, so be not subjected to the impact of leakage current frequency size.
As a kind of improved embodiment, also include L, the N line of grid-connected inverters end, the L of grid-connected inverters end, N line pass from magnetic core 1.
As a kind of improved embodiment, described magnetic core 1 is circular and adopts Ferrite Material.Magnetic core 1 material adopts Ferrite Material, be shaped as circle, with copper cash on magnetic core, magnet ring after winding is fixing to plastic pallet by epoxy resin, to go between tap as the carriage leg, adopt welding manner, carriage is connected magnetic core 1 is used for reinforcement by the magnetic induction density in the caused magnetic field of leakage current of L/N line with wiring board. owing to not only contain DC quantity in the leakage current, and contain the very of ac of high frequency, sensing circuit 2 can directly induce the magnetic induction density in magnetic field, and all has less volume and reliable performance.Theoretical and test shows, generally, be centered around around the L/N line magnetic field very a little less than, especially when leakage current hour, such as being 30mA, magnetic induction density even than also little 0.5 Gauss in magnetic field of the earth, for this reason, in this example, sensing circuit 2 adopts the self-oscillation circuit that magnetic flux is concentrated, and namely magnetic inductor intensity is strengthened.Because the relative permeability of iron about several thousand times, that is to say approximately much larger than the relative permeability of air, adopts iron magnetic core to strengthen preferably magnetic induction density, therefore, use iron can be to satisfy the demands as the making material of magnetic core 1.
As a kind of improved embodiment, described filtering and amplifying circuit 3 are provided with the two-stage low-pass filter, two-stage low-pass filter good wave filtering effect.
Claims (5)
1. leakage current test holding circuit; it is characterized in that comprising magnetic core (1); sensing circuit (2); filtering and amplifying circuit (3); biasing circuit (4) and testing circuit (5); described sensing circuit (2) comprises the self-oscillation circuit; sample circuit; the magnetic induction density in described self-oscillation electric circuit inspection magnetic field; described sample circuit changes into voltage signal with sensor current signal; described self-oscillation circuit is connected with sample circuit; described filtering and amplifying circuit (3) filtered voltage signal medium-high frequency composition also carries out signal and amplifies; described biasing circuit (4) is collected amplifying signal and is carried out absolute value and just get; described testing circuit (5) is processed the data that collect and is judged whether to reach the protection threshold value; described sensing circuit (2) is connected with magnetic core (1); described filtering is connected with sensing circuit (2) with amplifying circuit (3); described biasing circuit is connected with amplifying circuit (3) with filtering with sensing circuit (2), and described testing circuit (5) is connected with amplifying circuit (3) with filtering.
2. a kind of leakage current test holding circuit according to claim 1 is characterized in that also including L, the N line of grid-connected inverters end, and the L of described grid-connected inverters end, N line pass from magnetic core (1).
3. a kind of leakage current test holding circuit according to claim 1 and 2 is characterized in that described magnetic core (1) is circular and employing Ferrite Material.
4. a kind of leakage current test holding circuit according to claim 1 and 2 is characterized in that described filtering and amplifying circuit (3) are provided with the two-stage low-pass filter.
5. a kind of leakage current test holding circuit according to claim 3 is characterized in that filtering and amplifying circuit (3) are provided with the two-stage low-pass filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220514335 CN202870229U (en) | 2012-10-09 | 2012-10-09 | Leakage current detection and protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220514335 CN202870229U (en) | 2012-10-09 | 2012-10-09 | Leakage current detection and protection circuit |
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| CN202870229U true CN202870229U (en) | 2013-04-10 |
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| CN 201220514335 Expired - Fee Related CN202870229U (en) | 2012-10-09 | 2012-10-09 | Leakage current detection and protection circuit |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103543322A (en) * | 2013-10-29 | 2014-01-29 | 清源科技（厦门）股份有限公司 | Leak current detection device for photovoltaic grid-connected inverter |
| CN104155507A (en) * | 2014-08-20 | 2014-11-19 | 上海正泰电源***有限公司 | Leakage current detection circuit and method |
| CN104569703A (en) * | 2013-10-11 | 2015-04-29 | 北京嘉岳同乐极电子有限公司 | Electric leakage detecting and positioning device |
| CN105588970A (en) * | 2015-06-17 | 2016-05-18 | 陈小红 | Fault current detection device |
| CN106291032A (en) * | 2016-08-04 | 2017-01-04 | 中国电子科技集团公司第四十研究所 | A kind of current detecting unit leakage current eliminates circuit and removing method |
| WO2019084878A1 (en) * | 2017-11-02 | 2019-05-09 | 深圳驿普乐氏科技有限公司 | Charging leak current detection circuit |
| CN113759288A (en) * | 2021-11-08 | 2021-12-07 | 深圳市德兰明海科技有限公司 | Leakage current detection circuit and method and leakage current detector |
-
2012
- 2012-10-09 CN CN 201220514335 patent/CN202870229U/en not_active Expired - Fee Related
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104569703A (en) * | 2013-10-11 | 2015-04-29 | 北京嘉岳同乐极电子有限公司 | Electric leakage detecting and positioning device |
| CN104569703B (en) * | 2013-10-11 | 2019-02-15 | 北京嘉岳同乐极电子有限公司 | Detection of electrical leakage positioning device |
| CN103543322A (en) * | 2013-10-29 | 2014-01-29 | 清源科技（厦门）股份有限公司 | Leak current detection device for photovoltaic grid-connected inverter |
| CN103543322B (en) * | 2013-10-29 | 2016-05-04 | 清源科技（厦门）股份有限公司 | A kind of photovoltaic combining inverter leak current detection device |
| CN104155507A (en) * | 2014-08-20 | 2014-11-19 | 上海正泰电源***有限公司 | Leakage current detection circuit and method |
| CN105588970A (en) * | 2015-06-17 | 2016-05-18 | 陈小红 | Fault current detection device |
| CN105588970B (en) * | 2015-06-17 | 2018-06-15 | 陈小红 | Fault current detection device |
| CN106291032A (en) * | 2016-08-04 | 2017-01-04 | 中国电子科技集团公司第四十研究所 | A kind of current detecting unit leakage current eliminates circuit and removing method |
| CN106291032B (en) * | 2016-08-04 | 2019-03-26 | 中国电子科技集团公司第四十一研究所 | A kind of current detecting unit leakage current eliminates circuit and removing method |
| WO2019084878A1 (en) * | 2017-11-02 | 2019-05-09 | 深圳驿普乐氏科技有限公司 | Charging leak current detection circuit |
| CN113759288A (en) * | 2021-11-08 | 2021-12-07 | 深圳市德兰明海科技有限公司 | Leakage current detection circuit and method and leakage current detector |
| CN113759288B (en) * | 2021-11-08 | 2022-03-11 | 深圳市德兰明海科技有限公司 | Leakage current detection circuit and method and leakage current detector |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20130410 Termination date: 20171009 |
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| CF01 | Termination of patent right due to non-payment of annual fee |