CN103675396A - Leak current detector for photovoltaic inverter - Google Patents
Leak current detector for photovoltaic inverter Download PDFInfo
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Abstract
The invention discloses a leak current detector for a photovoltaic inverter. The leak current detecting method is based on a fluxgate technology. A saturable inductance sensing element is driven by a special circuit to circularly work on a magnetic hysteresis loop, and then the magnetic effect is utilized to detect the leak current. The leak current detector can accurately detect the alternating/direct leak current in the photovoltaic inverter, and is simple and convenient to implement, and low in cost.
Description
Technical field
The present invention relates to photovoltaic DC-to-AC converter field, is a kind of photovoltaic inverter leakage current pick-up unit based on Fluxgate Technique specifically, for needs such as photovoltaic DC-to-AC converters, detects a milliampere occasion for level ac and dc current.Background technology
Without isolated form photovoltaic DC-to-AC converter, when improving the efficiency of whole system, also brought the problem of leakage current.Leakage current can cause electromagnetic interference (EMI), the loss that power network current distortion and system are extra.The negative effect bringing in order to reduce leakage current, will be limited in the leakage current of circuit in safe scope.At VDE0126-1-1, in 2006-02 standard, different leakage current need to disconnect the connection of inverter and electrical network within the corresponding time.
Current, protective device of leakage current is used widely in each different occasions, and existing protective device of leakage current is mainly comprised of three parts such as differential converter, subsequent process circuit and physical constructions.Wherein, for detection of the part of leakage current, comprise the magnetic core of a circle or rectangle, on magnetic core, be wound with the fine copper wire of hundreds of circles, with a metal screen layer, magnetic core and copper cash are covered, to avoid external magnetic field to disturb.All current bus bars pass from magnetic core.In the situation that not there is not leakage current, the vector of passing all electric currents of magnetic core is zero, known based on Ampère circuital theorem so, now in magnetic core, does not have magnetic flux; If there is leakage current, current phasor and by non-vanishing so, meanwhile, leakage current will cause occurring in magnetic core variable magnetic flux; Further, this variable magnetic flux will cause occurring in coil induction electromotive force.Subsequent process circuit is processed and is analyzed the induction electromotive force in coil, if analysis result shows current leakage current, is greater than predefined threshold value, by activating mechanical hook-up, cuts off the electricity supply, to carry out defencive function.This device generally will stay an air gap on toroidal core, is used for filling sensor, such as Hall element of induced field etc.Utilize the variation of Hall plate induced field intensity, export corresponding Hall voltage.This brings certain difficulty to processing magnet ring, and expensive Hall element has increased the cost of protective device of leakage current simultaneously.
Consider that leakage current is conventionally smaller, so magnetic core need to adopt expensive permalloy material to make.This is because the relative permeability of permalloy is larger, can make the induction electromotive force of coil increase, and be convenient to process and analyze, otherwise if induction electromotive force is too small, rear extended meeting is difficult to process.In addition, if the leakage current detecting is larger, magnetic core needs larger cross section so, and to avoid occurring Flux saturation phenomenon, what impact detected normally carries out; If but very large of leakage current so just needs the cross section of magnetic flux very large, correspondingly, will cause the volume of device very large.
Visible, although existing detection mode can detect the leakage current in certain limit,, due to needs, use the materials such as permalloy, and need to increase magnetic core area or be provided for specially detecting the equipment of larger leakage current, therefore, increased the complexity realizing and realized cost.And owing to only having alternating current could produce induction electromotive force in coil, therefore existing detection mode is not suitable for detection DC leakage current.Existing detection mode is not suitable for to detect yet and has the larger leakage current of upper frequency, can cause occurring in coil eddy current, and then cause testing result inaccurate because have the larger leakage current of upper frequency.
Summary of the invention
Fundamental purpose of the present invention is to provide a kind of photovoltaic inverter leakage current pick-up unit.This device can be realized the detection to AC and DC leakage current, has the good linearity, and implements simple and conveniently, and can reduce costs.
For addressing the above problem, following solution is proposed:
A kind of photovoltaic inverter leakage current pick-up unit, by sensing element part, subsequent process circuit part, square fixed support, control panel circuit, connecting interface, photovoltaic DC-to-AC converter output line, formed, wherein: sensing element is wound on and on toroidal core material, is formed telefault and form by fine copper wire, comprises that two windings (2) are the more winding MO1-MO3 (8) of winding MO2-MO4 (7), the number of turn that the number of turn is less; Subsequent process circuit comprises constant-current source circuit (9), square wave excitation circuit (10), filtering biasing circuit (11).
Further: the winding MO2-MO4 (7) that the number of turn is less and constant-current source circuit (9) combination, for inspection module, can normally work; The winding MO1-MO3 (8) that the number of turn is more and square wave excitation circuit (10) combination, for driving satiable inductor periodic duty at magnetic hysteresis loop.
Further, described toroidal core (1) is for strengthening the magnetic induction density in the caused magnetic field of electric current in the leakage current I p of photovoltaic DC-to-AC converter output line (5) and two groups of windings (2), toroidal core is generally by crystallite, amorphous, and the ferromagnetic materials such as permalloy are made.
Further, described filtering biasing circuit (11) is for by MO1 output voltage signal output voltage V m after bias treatment after filtering, thereby determines the size of current leakage current.
Further, near described telefault inductance zero magnetic flux is larger, and when saturated, inductance is less, and inductance is by being saturated to unsaturated sudden change.
Further, described connecting interface is for being connected with auxiliary power circuit with photovoltaic DC-to-AC converter control panel.
Further, described square fixed support is used for fixing telefault and is convenient to and is connected with subsequent conditioning circuit module.
Further, described photovoltaic DC-to-AC converter output line passes from toroidal core.
The present invention is the creepage detection method based on Fluxgate Technique.The ultimate principle that Fluxgate Technique detects be the magnetic field of leakage current generating by a special sensing element senses, and this sensing element is by by a special drives, makes its periodic duty on magnetic hysteresis loop, then utilizes this magnetic effect to detect leakage current.The principle being specifically applied in invention is to utilize a satiable inductor as sensing element, and this satiable inductor is by by a special drives, makes its periodic duty on magnetic hysteresis loop.The magnetic saturation degree of satiable inductor is subject to the joint effect of driving circuit and leakage current.When there is no leakage current, the satiable inductor current waveform under the effect of square wave excitation voltage as shown in Figure 1.When leakage current is non-vanishing, the magnetic field of leakage current generating will affect the current waveform of satiable inductor under the effect of square wave excitation voltage, and current waveform as shown in Figure 2.Above-mentioned current waveform is converted into voltage waveform, process and can obtain equal threshold voltage after filtering, and the size of this magnitude of voltage and leakage current exists linear relationship, thereby can be derived by magnitude of voltage the size of leakage current.
Than existing leakage current test technology, scheme of the present invention has following advantage:
1. the method that the present invention detects leakage current is based on Fluxgate Technique.Adopt Fluxgate Technique, have the following advantages: low imbalance and offset drift, because magnetic core is in whole magnetic hysteresis loop cocycle work; Compare Hall element, its more can be on little electric current embodiment advantage; There is stronger excess current recovery capability; Compare other technology, it has higher sensitivity; Very large dynamic range; High bandwidth; Low Drift Temperature etc.
2. in scheme of the present invention, sensing element only needs a saturable inductance.Near saturable inductance inductance zero magnetic flux is larger, and when saturated, inductance is less, and inductance is by being saturated to unsaturated sudden change.Compare expensive Hall element, this programme has reduced realizes cost.
3. in scheme of the present invention, the convenience of product passed examination while considering the batch production of this device, specialized designs inspection module, i.e. the less winding of the number of turn and the combination of constant-current source circuit.
4. in scheme of the present invention, the sensing element that the making of telefault is compared other is simple.What magnetic core adopted is toroidal core.Concerning manufacturer, toroidal core is most economical, is that in its comparable various magnetic cores, its cost is minimum.The material of magnetic core is generally by crystallite, amorphous, and the ferromagnetic materials such as permalloy are made, so satiable inductor generally all has very high initial permeability and very high saturation induction density.Telefault generally adopts fine copper wire coiling to form, and comprises two windings, and the number of turn of a winding is less, and the number of turn of another winding is more.
5. in scheme of the present invention, can detect other DC/AC leakage current of milliampere level of photovoltaic DC-to-AC converter.Detect the scope of leakage current and can carry out according to actual needs circuit conditioning, such as according to the collection voltage range of A/D mouth, design the proportionate relationship of different leakage current and output voltage, thereby reach different accuracy of detection.Detect the frequency range of leakage current and also can carry out as required circuit conditioning, the main and telefault of frequency range and to pass through the circuit of telefault electric current relevant.The present invention can be applied in photovoltaic inverter leakage current detection, can detect faint DC leakage current, can detect again the ac leakage stream of power frequency and industrial frequency harmonic.
Accompanying drawing explanation
Fig. 1 is the current waveform figure of satiable inductor under the effect of square wave excitation voltage while there is no leakage current;
Fig. 2 is the current waveform figure of satiable inductor under the effect of square wave excitation voltage while having leakage current;
Fig. 3 is photovoltaic inverter leakage current structure of the detecting device schematic diagram of the present invention;
Fig. 4 is photovoltaic inverter leakage current pick-up unit schematic diagram of the present invention;
Fig. 5 is the voltage waveform of telefault pin MO1 while there is no leakage current;
Fig. 6 is the voltage waveform of telefault pin MO1 while having leakage current.
Embodiment
For existing photovoltaic inverter leakage current, detect and exist precision not high, expensive problem, the present invention proposes a kind of photovoltaic inverter leakage current detection scheme based on Fluxgate Technique, utilize saturable telefault, other DC/AC leakage current of milliampere level faint in photovoltaic DC-to-AC converter is induced, and by subsequent process circuit, quantize the size of leakage current, obtain the linear relationship of leakage current and output voltage.Can design as required the funtcional relationship of output voltage and leakage current, thereby obtain different ranges, the photovoltaic leak current detection device of precision and frequency range.
For making technical scheme of the present invention clearer, clear, referring to accompanying drawing examples, scheme shown in the present is described in detail further.Photovoltaic inverter leakage current structure of the detecting device schematic diagram of the present invention as shown in Figure 3.Device comprises toroidal core (1), telefault (2), be used for fixing the square fixed support (3) of telefault, subsequent process circuit plate (4), for circular hole and the interface (6) for being connected with auxiliary electrical source plate with control panel through photovoltaic DC-to-AC converter output line (5).Title from left to right of interface (6) pin and illustrate as shown in table 1.
Table 1 interface 6 pin name and explanation from left to right
The principle of specific implementation can illustrate with reference to Fig. 4, and Fig. 4 is photovoltaic inverter leakage current pick-up unit schematic diagram of the present invention.Schematic diagram comparison system has illustrated the principle of work of detection of electrical leakage module.Telefault has two windings, the winding MO1-MO3 (8) that the winding MO2-MO4 (7) that the number of turn is less and the number of turn are more.Can winding MO2-MO4 (7) and constant current seedbed circuit (9) combination, normally work for inspection module.Concrete embodiment is that the whole leakage current test module assembling is powered on, and by control panel circuit, controlling pin 1 Det_Leakagel is zero setting state, and the Is in Fig. 4 is zero.In the situation that leakage current Ip is zero, the voltage that the voltage Vm of pin 2 Det_Leakage2 that the A/D mouth of control panel circuit detects should provide for biasing circuit.When control panel circuit control pin 1 Det_Leakagel is vacant state, in winding MO2-MO4 (7), will there is a constant electric current I s, it corresponds to the leakage current Ip of certain value.The voltage Vm of pin 2 Det_Leakage2 that the A/D mouth of control panel circuit detects should add by the magnitude of voltage after Butterworth filter for bias voltage.By these two tests, just substantially can determination module whether qualified.Winding MO1-MO3 (8) and square wave excitation circuit (10) combination, for driving satiable inductor periodic duty at magnetic hysteresis loop.The magnetic saturation of the satiable inductor being comprised of winding MO1-MO3 (8) and toroidal core (1) is mainly caused by two parts electric current, a part is the leakage current in photovoltaic DC-to-AC converter output line, another part is by comparator circuit, differential amplifier circuit, push-pull output circuit, the square wave excitation circuit (10) of limiter diode the electric circuit constitute drives the electric current of satiable inductor.When there is no leakage current Ip, the magnetic saturation of satiable inductor is mainly caused by the electric current under the effect of square wave excitation voltage.When satiable inductor passes through less electric current, inductance is very large, and curent change is very little, and the voltage of MO1 increases smaller; When reaching a critical value, inductance is saturated rapidly, and inductance sharply diminishes, and electric current increases rapidly, and the voltage of MO1 also sharply increases thereupon.When the voltage of MO1 is increased to the voltage that obtains through dividing potential drop than MO3 when also large, comparator circuit output changes, and by differential amplifier circuit, recommends output, and limiter diode circuit makes to export square-wave voltage upset, the magnetic saturation of reverse drive satiable inductor.While there is no leakage current Ip, the voltage waveform of MO1 as shown in Figure 5.The voltage of MO1 is by after Butterworth filter, output be the mean value of MO1 voltage, more obtain output voltage V m by biasing circuit.
When having leakage current Ip, the magnetic saturation of satiable inductor is caused jointly by the electric current under leakage current Ip and the effect of square wave excitation voltage.Because leakage current Ip produces a magnetic field in satiable inductor, while only having so magnetic field that electric current under the effect of square wave excitation voltage produces and this magnetic field to cancel out each other, inductance is just very large, and the voltage of MO1 just gently.While having leakage current Ip, the voltage waveform of MO1 as shown in Figure 6.The voltage of MO1 is by after Butterworth filter, output be the mean value of MO1 voltage, more obtain output voltage V m by biasing circuit.There is linear relationship in this voltage Vm and leakage current Ip, thereby can be derived by magnitude of voltage the size of leakage current.
In photovoltaic synchronization inverter system, VDE standard has the different response times to leakage current to the leakage current of different sizes, specifically as shown in table 2.
The response time of table 2 pair mutation current
Design a pick-up unit that can detect this photovoltaic inverter leakage current, need to consider range, precision and the frequency range of detection.Such as the voltage range of A/D acquisition port is 0-3V, the bias voltage of biasing circuit is just designed to 1.5V so, measurement that so just can maximum range.The control of precision is mainly in the setting of the gain parameter of Butterworth filter, and in order to meet the requirement to aftercurrent accuracy of detection, it is 2.865 that Butterworth filter parameter is set to gain, and cutoff frequency is 1.4kHz.
Design philosophy and principle according to above, designed photovoltaic inverter leakage current pick-up unit, and detect test by simulation DC/AC leakage current, and the result of detection is as shown in table 3.In table 3, the leakage current of the positive negative indication different directions of leakage current, when leakage current is 0mA, output voltage is not bias voltage 1.5V, this is that voltage stabilizing chip voltage stabilizing due to side circuit has deviation, but this does not affect the accuracy of detection to leakage current.In practical implementation, the output voltage V m while first detecting leakage current Ip and be zero, and using the voltage now detecting as bias voltage Vb.According to the linear relationship of leakage current and output voltage, can draw
Vm＝0.0019438Ip+Vb
The value that Vb detects according to reality is as the criterion, such as Vb=1.479 in this example.
The output voltage of table 3 leakage current
In a word, adopt technical scheme of the present invention, there is following advantage: the present invention detects the method for leakage current based on Fluxgate Technique.Adopt Fluxgate Technique, have the following advantages: low imbalance and offset drift, because magnetic core is in whole magnetic hysteresis loop cocycle work; Compare Hall element, its more can be on little electric current embodiment advantage; There is stronger excess current recovery capability; Compare other technology, it has higher sensitivity; Very large dynamic range; High bandwidth; Low Drift Temperature etc.
Below the present invention is described in detail; the above is only the present invention's preferred embodiment, when not limiting the scope of the present invention; all any modifications of doing within the spirit and principles in the present invention, be equal to and replace or improve, within all should being included in protection scope of the present invention.
Claims (8)
1. a photovoltaic inverter leakage current pick-up unit, by sensing element part, subsequent process circuit part, square fixed support, control panel circuit, connecting interface, photovoltaic DC-to-AC converter output line, formed, it is characterized in that: sensing element is wound on and on toroidal core material, is formed telefault and form by fine copper wire, comprises that two windings (2) are the more winding MO1-MO3 (8) of winding MO2-MO4 (7), the number of turn that the number of turn is less; Subsequent process circuit comprises constant-current source circuit (9), square wave excitation circuit (10), filtering biasing circuit (11).
2. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: the winding MO2-MO4 (7) that the number of turn is less and constant-current source circuit (9) combination, for inspection module, can normally work; The winding MO1-MO3 (8) that the number of turn is more and square wave excitation circuit (10) combination, for driving satiable inductor periodic duty at magnetic hysteresis loop.
3. photovoltaic inverter leakage current pick-up unit according to claim 1, it is characterized in that: described toroidal core (1) is for strengthening the magnetic induction density in the caused magnetic field of electric current in the leakage current Ip of photovoltaic DC-to-AC converter output line (5) and two groups of windings (2), and toroidal core is generally elected the ferromagnetic material making such as crystallite, amorphous, permalloy as.
4. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: described filtering biasing circuit (11) is for by MO1 output voltage signal output voltage V m after bias treatment after filtering, thereby determines the size of current leakage current.
5. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: near described telefault inductance zero magnetic flux is larger, and when saturated, inductance is less, and inductance is by being saturated to unsaturated sudden change.
6. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: described connecting interface is for being connected with auxiliary power circuit with photovoltaic DC-to-AC converter control panel.
7. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: described square fixed support is used for fixing telefault and is convenient to and is connected with subsequent conditioning circuit module.
8. photovoltaic inverter leakage current pick-up unit according to claim 1, is characterized in that: described photovoltaic DC-to-AC converter output line passes from toroidal core.
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| CN104133099A (en) * | 2014-07-07 | 2014-11-05 | 中国电子科技集团公司第四十一研究所 | Detection device and method for residual current of photovoltaic array |
| CN105223519A (en) * | 2015-09-28 | 2016-01-06 | 广东易事特电源股份有限公司 | Photovoltaic inverter leakage current protection act proving installation |
| CN106018920A (en) * | 2016-05-25 | 2016-10-12 | 河北工业大学 | Single magnetic core complex waveform current sensor |
| CN109752619A (en) * | 2017-11-01 | 2019-05-14 | 晓星电力有限责任公司 | Leak electricity amount detecting device |
| CN110632366A (en) * | 2019-09-29 | 2019-12-31 | 浙江巨磁智能技术有限公司 | Leakage current sensor for low-power three-phase inverter |
| CN110687343A (en) * | 2019-10-22 | 2020-01-14 | 阳光电源股份有限公司 | Leakage current detection method and circuit |
| CN111721983A (en) * | 2020-06-23 | 2020-09-29 | 广东电网有限责任公司 | Current measurement clamp meter |
| CN112345966A (en) * | 2019-08-07 | 2021-02-09 | 青岛鼎信通讯股份有限公司 | Method and device for detecting direct current leakage through residual current transformer |
| WO2021068832A1 (en) * | 2019-10-09 | 2021-04-15 | 青岛鼎信通讯股份有限公司 | Residual current detection method based on magnetic core working state switching |
| 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 |
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| CN104133099A (en) * | 2014-07-07 | 2014-11-05 | 中国电子科技集团公司第四十一研究所 | Detection device and method for residual current of photovoltaic array |
| CN105223519A (en) * | 2015-09-28 | 2016-01-06 | 广东易事特电源股份有限公司 | Photovoltaic inverter leakage current protection act proving installation |
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| CN106018920A (en) * | 2016-05-25 | 2016-10-12 | 河北工业大学 | Single magnetic core complex waveform current sensor |
| CN106018920B (en) * | 2016-05-25 | 2018-09-18 | 河北工业大学 | A kind of single magnetic core complicated wave form current sensor |
| CN109752619A (en) * | 2017-11-01 | 2019-05-14 | 晓星电力有限责任公司 | Leak electricity amount detecting device |
| CN112345966A (en) * | 2019-08-07 | 2021-02-09 | 青岛鼎信通讯股份有限公司 | Method and device for detecting direct current leakage through residual current transformer |
| CN112345966B (en) * | 2019-08-07 | 2023-02-03 | 青岛鼎信通讯股份有限公司 | Method and device for detecting direct current leakage through residual current transformer |
| CN110632366A (en) * | 2019-09-29 | 2019-12-31 | 浙江巨磁智能技术有限公司 | Leakage current sensor for low-power three-phase inverter |
| WO2021068832A1 (en) * | 2019-10-09 | 2021-04-15 | 青岛鼎信通讯股份有限公司 | Residual current detection method based on magnetic core working state switching |
| CN110687343A (en) * | 2019-10-22 | 2020-01-14 | 阳光电源股份有限公司 | Leakage current detection method and circuit |
| CN111721983A (en) * | 2020-06-23 | 2020-09-29 | 广东电网有限责任公司 | Current measurement clamp meter |
| 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 |
| EP4113144A4 (en) * | 2021-11-08 | 2023-10-18 | Shenzhen Poweroak Newener Co., Ltd | Leakage current detection circuit and method, and leakage current detector |
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