CN202720310U - Novel photovoltaic grid-connected inverter insulation detection circuit - Google Patents

Abstract

The utility model provides a photovoltaic grid-connected inverter insulation detection circuit. The detection circuit comprises a power supply circuit, a partial pressure sampling circuit, a filter circuit, a difference circuit, a summing circuit, a double threshold comparison circuit and a driving output circuit. The insulation detection circuit can carry out real-time voltage sampling and comparison operation so that a detection speed is increased and precision of the insulation detection is increased too.

Description

A kind of novel photovoltaic grid-connected inverter insulation detecting circuit

Technical field：

The utility model belongs to field of photovoltaic power generation, particularly a kind of photovoltaic combining inverter insulation detecting circuit.

Background technology：

Photovoltaic combining inverter and square formation ground insulation impedance detection are with the large-scale application of photovoltaic combining inverter, and the Insulation monitoring problem of photovoltaic arrays receives much concern.In existing insulation detecting circuit, it is low to there is Insulation monitoring precision, the problems such as detection speed is slow.The utility model proposes insulation detecting circuit can carry out real-time voltage sample and comparison operation, improve detection speed, and the precision of Insulation monitoring is improved using the calculation of novelty.

Utility model content：

The technical problem that the utility model is solved is that, in order to improve the precision of Insulation monitoring, the new insulation detecting circuit of proposition kind can carry out real-time voltage sample and comparison operation, improve detection speed.

The technical solution adopted in the utility model is to provide a kind of photovoltaic combining inverter insulation detecting circuit, and the detection circuit includes power-supplying circuit, pressure sampling circuit, filter circuit, difference channel, summing circuit, double threshold comparison circuit and driving output circuit；

Further, in the pressure sampling circuit, the series connection bleeder circuit constituted using precision resistance is carried out partial pressure to photovoltaic arrays DC voltage PV+, PV- and obtains sampled signal；

Further, in the pressure sampling circuit, the voltage follower of also operational amplifier OP413 compositions is used for the input impedance for improving the pressure sampling circuit.

Further, the filter circuit is the second-order low-pass filter circuit built using operational amplifier OP413 and resistance, electric capacity.

Further, the difference channel is made up of operational amplifier OP413 and resistance, electric capacity, and the summing circuit is made up of operational amplifier OP413 and resistance.

Further, the double threshold comparison circuit is made up of operational amplifier OP413 and high-accuracy resistance.

Further, the driving output circuit using resistance, optocoupler and 12V relay groups into.

The beneficial effects of the utility model are that this New insulated detection circuit can carry out real-time voltage sample and comparison operation, improve detection speed, and improve the precision of Insulation monitoring.

Brief description of the drawings：

Fig. 1 is schematic diagram of being sampled when naked is abnormal in the utility model；

Fig. 2 samples schematic diagram when being Abnormal Insulation in the utility model；

Fig. 3 is insulation detecting circuit electrical schematic diagram in the utility model.

Embodiment：

Referring to Fig. 1, positive voltage-to-ground, negative voltage-to-ground to photovoltaic arrays are sampled respectively, obtain sampled voltage VS1 and VS2, when there is no Abnormal Insulation, sampled voltage VS1, VS2 sum is exactly the voltage sample of photovoltaic arrays, almost consistent due to sampling resistor, sampled voltage VS1, VS2 difference are exactly zero, as following formula is represented：

$\mathrm{<figure-callout\; id="1"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}1=\frac{\mathrm{Rs}}{2(R+\mathrm{Rs})}\&times;\mathrm{Upv}$

$\mathrm{<figure-callout\; id="2"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}2=\frac{\mathrm{Rs}}{2(R+\mathrm{Rs})}\&times;\mathrm{Upv}$

$\mathrm{<figure-callout\; id="1"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}1+\mathrm{<figure-callout\; id="2"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}2=\frac{\mathrm{Rs}}{R+\mathrm{Rs}}\&times;\mathrm{Upv}$

VS1-VS2=0

Wherein, Upv is the voltage of photovoltaic arrays, and Rs is sampling resistor, and R is divider resistance.When Abnormal Insulation occurs for photovoltaic arrays, it is assumed that negative resistance to earth is changed into Rx, as shown in Fig. 2 now, voltage sample VS1, VS2 will change, sampled voltage VS1, VS2 sum does not change, and sampled voltage VS1, VS2 difference are changed.

$\mathrm{<figure-callout\; id="1"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}1=\frac{\mathrm{Rs}}{R+\mathrm{Rs}+\mathrm{Rx}}\&times;\mathrm{Upv}$

$\mathrm{<figure-callout\; id="2"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}2=\frac{\mathrm{Rx}}{R+\mathrm{Rs}+\mathrm{Rx}}\&times;\frac{\mathrm{Rs}}{R+\mathrm{Rs}}\&times;\mathrm{Upv}$

$\mathrm{<figure-callout\; id="1"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}1+\mathrm{<figure-callout\; id="2"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}2=\frac{\mathrm{Rs}}{R+\mathrm{Rs}}\&times;\mathrm{Upv}$

$\mathrm{VS}1-\mathrm{<figure-callout\; id="2"\; label="VS"\; filenames="HDA00002001667100021.png"\; state="\{\{state\}\}">VS</figure-callout>}2=\frac{\mathrm{Rs}}{R+\mathrm{Rs}}\&times;\mathrm{Upv}\&times;\frac{R+\mathrm{Rs}-\mathrm{Rx}}{R+\mathrm{Rs}+\mathrm{Rx}}$

Wherein, Upv is the voltage of photovoltaic arrays, and Rs is sampling resistor, and R is divider resistance, and Rx is the negative impedance over the ground of photovoltaic arrays, and 0≤Rx≤R+Rs.When square formation Abnormal Insulation, sampled voltage VS1, VS2 difference drastically become big by 0, therefore can occur abnormal distinguishing rule as insulation using this difference.

The invention is realized by hardware circuit, according to shown in Fig. 3 electrical schematic diagrams, symmetric sampling is carried out to photovoltaic arrays, sampled voltage passes through voltage follower, smooth direct current sampled voltage VS1 is formed by second order filter again, VS2, VS1 and VS2 can obtain sampled voltage VS1 by differential amplifier, VS2 sums Upv and reversely value Upv_negative, VS1 and VS2 is obtained by add circuit again the difference subtract of sampled voltage, fiducial value using Upv and Upv_negative after scaling as double threshold comparator, it is compared with voltage difference subtract with double threshold comparator, the state of output relay is controlled by the output of comparator.When naked is abnormal, the charging of relay line bag, the closing of contact；When Abnormal Insulation, relay line bag power down, contact disjunction.

The circuit is broadly divided into 7 parts：1. pressure sampling circuit, 2. filter circuit, 3. difference channel, 4. summing circuit, 5. double threshold comparison circuit, 6. drive output circuit, 7. power-supplying circuit, in pressure sampling circuit, the series connection bleeder circuit constituted using precision resistance (R3~R40) is carried out partial pressure to photovoltaic arrays DC voltage PV+, PV- and obtains sampled signal VS01, VS02, symmetric mode sampling is carried out to photovoltaic arrays DC voltage, bleeder circuit input impedance is improved by the operational amplifier OP413 voltage followers constituted, its carrying load ability is improved.Filter circuit uses the second-order low-pass filter circuit that operational amplifier OP413 and resistance capacitance are built, and filters high fdrequency component, makes output more smooth, can thus obtain more smooth DC voltage VS1, VS2.Difference channel is made up of operational amplifier OP413 and resistance capacitance, difference channel is also known as subtraction circuit, major function is the difference for calculating VS1 and VS2, because sampling to voltage VS1 be on the occasion of, and VS2 is negative value, so, VS1 and VS2 can be obtained by sampled voltage VS1, VS2 sum Upv and reversely value Upv_negative after difference channel does subtraction.Summing circuit is made up of operational amplifier OP413 and resistance, summing circuit is also known as add circuit, major function is for calculating VS1 and VS2 sums, because sampling to voltage VS1 be on the occasion of, and VS2 is negative value, therefore, VS1 and VS2 can be obtained by sampled voltage VS1, VS2 difference subtract after summing circuit does add operation.Double threshold comparison circuit is made up of operational amplifier OP413 and high-accuracy resistance, Upv and Upv_negative is carried out using high-accuracy resistance in this circuit scaling, signal after will be scaling is as the fiducial value of double threshold comparison circuit, and the output level of sampled voltage VS1, VS2 difference subtract after double threshold comparison circuit is exactly the control signal of relay.Drive output circuit using resistance, optocoupler and 12V relay groups into when comparison circuit is output as high level, optocoupler is turned on, relay line Bao get electricity, the closing of contact, when comparison circuit is output as low level, and optocoupler shut-off, relay line bag power down, contact is separated.

The operation principle of circuit is the charging of relay line bag, the closing of contact when naked is abnormal；When Abnormal Insulation, relay line bag power down, contact is separated.The operational amplifier of high-accuracy resistance and high-gain is employed in whole circuit to ensure the speed of the precision and detection of whole detection circuit.

For the utility model person of an ordinary skill in the technical field, without departing from the concept of the premise utility, some simple deduction or replace can also be made, protection domain of the present utility model should be all considered as belonging to.

Claims (7)

1. a kind of photovoltaic combining inverter insulation detecting circuit, it is characterised in that the detection circuit includes power-supplying circuit, pressure sampling circuit, filter circuit, difference channel, summing circuit, double threshold comparison circuit and driving output circuit.

2. detection circuit according to claim 1, it is characterised in that in the pressure sampling circuit, the series connection bleeder circuit constituted using precision resistance is carried out partial pressure to photovoltaic arrays DC voltage PV+, PV- and obtains sampled signal.

3. the voltage follower of detection circuit according to claim 2, it is characterised in that in the pressure sampling circuit, also operational amplifier OP413 composition is used for the input impedance for improving the pressure sampling circuit.

4. detection circuit according to claim 1, it is characterised in that the filter circuit is the second-order low-pass filter circuit built using operational amplifier OP413 and resistance, electric capacity.

5. detection circuit according to claim 1, it is characterised in that the difference channel is made up of operational amplifier OP413 and resistance, electric capacity, and the summing circuit is made up of operational amplifier OP413 and resistance.

6. detection circuit according to claim 1, it is characterised in that the double threshold comparison circuit is made up of operational amplifier OP413 and high-accuracy resistance.

7. detection circuit according to claim 1, it is characterised in that the driving output circuit using resistance, optocoupler and 12V relay groups into.

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