CN102279317B - Online detection method of insulating resistance to ground of photovoltaic grid-connected inverter - Google Patents
Online detection method of insulating resistance to ground of photovoltaic grid-connected inverter Download PDFInfo
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Abstract
The invention relates to the technology of photovoltaic grid-connected inverter, in particular to an online detection method of insulating resistance to ground of a photovoltaic grid-connected inverter. The method comprises the following steps of: by sampling an output voltage VPV of a photovoltaic cell and enabling a switch S1 in a resistance switch circuit to be in opening or closing state, disconnecting or connecting a resistor R5 from or to an upper bridge arm, and then sampling a voltage signal of a dividing voltage output end of a lower bridge arm to obtain a voltage ratio equation of anode to ground of photovoltaic cell and cathode to ground of the photovoltaic cell, thereby online calculating a insulating resistance R+ of anode to ground of the photovoltaic cell and an insulating resistance R- of cathode to ground of the photovoltaic cell in real-time and accurately. The method has simple calculation process and high detecting precision; by adopting the method, the online and real-time detection of anode-to-ground resistance of the photovoltaic cell and the cathode-to-ground resistance of the photovoltaic cell is achieved, the photovoltaic grid-connected inverter is guaranteed to work safely and reliably.
Description
Technical field
The present invention relates to the photovoltaic combining inverter technology, relate in particular to a kind of insulation against ground resistance online test method of photovoltaic combining inverter.
Background technology
In photovoltaic combining inverter, the output voltage of photovoltaic cell is higher, and for example: powerful photovoltaic combining inverter, the output voltage of its photovoltaic cell can be up to more than the 600V.Simultaneously, because the photovoltaic battery panel of photovoltaic cell is open-air the placement, so the weather conditions such as dust, sleet, dense fog all can affect positive pole, the over the ground variation of (following alleged " over the ground " all refers on " for the earth ", i.e. Earth) insulation of negative pole of photovoltaic cell.As a kind of high-pressure system, a quality that key index is exactly the insulation degree of photovoltaic combining inverter safety, whether the state of insulation that the insulation measurement technology can be judged current system is good, and the situation of change of state of insulation.
At present, detect the insulation against ground resistance of photovoltaic combining inverter, usually adopt the detection method based on the bridge balance principle.Please refer to Fig. 1, be the insulation against ground resistance detecting circuit schematic diagram based on the bridge balance principle, the R+ of dotted portion is positive pole (PV+) insulation resistance over the ground of photovoltaic cell among Fig. 1, the R-of dotted portion is negative pole (PV-) insulation resistance over the ground of photovoltaic cell, wherein, between the positive pole and the earth of photovoltaic cell, all be connected to given resistance R between the negative pole of photovoltaic cell and the earth, when by detecting voltage U j and Um, in conjunction with given resistance R, can calculate R+ and R-again.But, when R+ and R-descend on an equal basis, this detection method based on the bridge balance principle, the anodal actual insulation resistance over the ground negative pole reality insulation resistance over the ground big or small and photovoltaic cell that can not accurately detect photovoltaic cell is big or small, namely can not accurately detect the positive pole of photovoltaic cell, the variation of negative pole insulation against ground.
Summary of the invention
The object of the invention is to provide for the deficiencies in the prior art a kind of insulation against ground resistance online test method of photovoltaic combining inverter, it can calculate positive pole insulation resistance and the negative pole insulation resistance over the ground over the ground of the photovoltaic cell of photovoltaic combining inverter online real-time and accurately.
Purpose of the present invention realizes by following technical measures: a kind of insulation against ground resistance online test method of photovoltaic combining inverter, and it may further comprise the steps:
A: the output voltage V of sampling photovoltaic cell
PV
B: make the switch S 1 in the resistance switch circuit be in off-state, resistance R 5 is broken away from from upper brachium pontis, after the processing of voltage signal Vo1 through power frequency codan, filtering circuit, voltage follower circuit and isolating amplifier circuit of the resistance R 3 of lower brachium pontis, the output of R4 dividing potential drop, obtain output signal Vad1, the pass of Vad1 and Vo1 is:
Setting R+ is the positive pole insulation resistance over the ground of photovoltaic cell, and R-is the negative pole insulation resistance over the ground of photovoltaic cell, according to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis of upper brachium pontis, the relation of R4 dividing potential drop, obtains following formula:
C: make the switch S 1 in the resistance switch circuit be in closure state, in the upper bridge arm circuit of resistance R 5 accesses, after the processing of voltage signal Vo2 through power frequency codan, filtering circuit, voltage follower circuit and isolating amplifier circuit of the resistance R 3 of lower brachium pontis, the output of R4 dividing potential drop, obtain output signal Vad2, the pass of Vad2 and Vo2 is:
According to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis of upper brachium pontis, the relation of R4 dividing potential drop, obtain following formula:
D: the positive pole that obtains two groups of photovoltaic cells by step B and C over the ground with the negative pole voltage ratio equation over the ground of photovoltaic cell, wherein unknown parameter is R+ and R-, carries out the resistance value that R+ and R-are tried to achieve in computing, process is derived as follows:
Can get formula (1) substitution formula (2), formula (3) substitution formula (4) respectively:
(5)
Because V
PV, Vad1, Vad2 be the numerical value that obtains of sampling, order
Then can obtain:
Thereby try to achieve the resistance value of R+ and R-;
Wherein, described upper brachium pontis comprises resistance R 1, R2, and an end of resistance R 1 is connected with the positive pole of photovoltaic cell, and the other end of resistance R 1 is connected with an end of resistance R 2, another termination the earth of resistance R 2; Described lower brachium pontis comprises resistance R 3, R4, and a termination the earth of resistance R 3, the other end of resistance R 3 are the dividing potential drop output terminal of lower brachium pontis, and an end of resistance R 4 is connected with the dividing potential drop output terminal of lower brachium pontis, and the other end of resistance R 4 is connected with the negative pole of photovoltaic cell; Described resistance switch circuit comprises resistance R 5, switch S 1, one end of resistance R 5 is connected with the positive pole of photovoltaic cell, the other end of resistance R 5 is connected with the first end of switch S 1, the second termination the earth of switch S 1, and the control end of switch S 1 is the control end of resistance switch circuit;
Described power frequency codan is bypass filter capacitor C1, and the end of bypass filter capacitor C1 is connected with the dividing potential drop output terminal of lower brachium pontis, and the other end of bypass filter capacitor C1 is connected with the negative pole of photovoltaic cell; Described filtering circuit comprises resistance R 6, capacitor C 2, one end of resistance R 6 is connected with the end of bypass filter capacitor C1, the other end of resistance R 6 is connected with an end of the input end of voltage follower circuit, capacitor C 2, and the other end of capacitor C 2 is connected with the negative pole of photovoltaic cell; Described voltage follower circuit is made of operational amplifier U1A, the in-phase input end of operational amplifier U1A is the input end of voltage follower circuit, the inverting input of operational amplifier U1A is connected with the output terminal of operational amplifier U1A, the power supply positive pole of operational amplifier U1A is connected with the power supply of the pwm chip of the accessory power supply module of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U1A is connected with the negative pole of photovoltaic cell;
Described isolating amplifier circuit comprises resistance R 7, R8, R9, R10, capacitor C 3, C4, C5, C6, operational amplifier U1B, operational amplifier U2A, linear optical coupling U3; One end of resistance R 7 is connected with the output terminal of operational amplifier U1A, one end of the other end of resistance R 7 and capacitor C 3, the inverting input of operational amplifier U1B, one end of capacitor C 4,3 pin of linear optical coupling U3 connect, the other end of capacitor C 3, the in-phase input end of operational amplifier U1B, 4 pin of linear optical coupling U3 all are connected with the negative pole of photovoltaic cell, the output terminal of the other end of capacitor C 4 and operational amplifier U1B, one end of resistance R 8 connects, the other end of resistance R 8 is connected with 1 pin of linear light idol U3, the PWM(Pulse Width Modulation of 2 pin of linear optical coupling U3 and the accessory power supply module of photovoltaic combining inverter, pulse-length modulation) power supply of control chip connects, 6 pin of linear optical coupling U3 and the inverting input of operational amplifier U2A, one end of capacitor C 5, one end of resistance R 9 connects, the other end of capacitor C 5, the other end of resistance R 9, one end of resistance R 10 all is connected with the output terminal of operational amplifier U2A, the other end of resistance R 10 is the output terminal of isolating amplifier circuit, one end of capacitor C 6 is connected with the output terminal of isolating amplifier circuit, 5 pin of linear optical coupling U3, the in-phase input end of operational amplifier U2A, the other end of capacitor C 6 all connects simulation ground, the power supply of operational amplifier U2A is anodal to be connected with the power supply+VCCA of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U2A is connected with the power supply-VCCA of photovoltaic combining inverter.
Behind step D, also comprise step e: whether the resistance value of judging R+ and R-satisfies the safety requirement.
After step e, also comprise step F: according to result of determination, carry out next step action of photovoltaic combining inverter, if the resistance value of R+ and R-satisfies the safety requirement, then allow photovoltaic combining inverter startup work, if do not satisfy the safety requirement, then forbid photovoltaic combining inverter startup work, and send alerting signal.
Described steps A is by the output voltage V of microprocessor by PV voltage detecting circuit sampling photovoltaic cell
PVWherein, the first test side of described PV voltage detecting circuit is connected with the positive pole of photovoltaic cell, the second test side of described PV voltage detecting circuit is connected with the negative pole of photovoltaic cell, the 2nd A/D(analog/digital conversion of the output terminal of described PV voltage detecting circuit and described microprocessor) input port is connected.
The one I/O(I/O of the control end of described resistance switch circuit and described microprocessor) port is connected, and described microprocessor is in by the switch S 1 in the control end controlling resistance on-off circuit of resistance switch circuit and disconnects or closure state.
Described microprocessor is the voltage signal by the dividing potential drop output terminal of described power frequency codan, filtering circuit, voltage follower circuit and the lower brachium pontis of isolating amplifier circuit sampling; Wherein, the output terminal of described isolating amplifier circuit is connected with an A/D input port of described microprocessor.
Described microprocessor adopts FIR(that limit for length's shock response is arranged) digital filtering algorithm makes further digital filtering to the A/D sampled signal and processes, this microprocessor is DSP(Digital Signal Processor) microprocessor.
Described microprocessor is provided with the 2nd I/O port, and the 2nd I/O port is connected with warning circuit, and microprocessor sends alerting signal by the 2nd I/O port driver warning circuit.
Described microprocessor is provided with the pwm signal port, the pwm signal port is connected with Boost circuit and the inverter circuit of photovoltaic combining inverter, and described microprocessor is controlled the photovoltaic combining inverter startup work that whether allows by Boost circuit and the inverter circuit of pwm signal port controlling photovoltaic combining inverter.
Beneficial effect of the present invention is: the present invention is by the output voltage V of sampling photovoltaic cell
PVAnd by making the switch S 1 in the resistance switch circuit be in disconnection or closure state, resistance R 5 is broken away from from upper brachium pontis or access in the brachium pontis, then the voltage signal of the dividing potential drop output terminal of brachium pontis under sampling, with the positive pole that obtains two groups of photovoltaic cells over the ground with the negative pole voltage ratio equation over the ground of photovoltaic cell, thereby calculate real-time and accurately online positive pole insulation resistance R+ over the ground and the negative pole insulation resistance R-over the ground of photovoltaic cell of photovoltaic cell.Computation process of the present invention is succinct, accuracy of detection is high, has realized that the online of negative pole insulation against ground resistance of the anodal insulation against ground resistance of photovoltaic cell and photovoltaic cell detects in real time, has guaranteed that photovoltaic combining inverter works safely and reliably.
Description of drawings
Fig. 1 is existing insulation against ground resistance detecting circuit schematic diagram based on the bridge balance principle.
Fig. 2 is the functional-block diagram of the insulation against ground resistance online test method of a kind of photovoltaic combining inverter of the present invention.
Fig. 3 is that the circuit of PV voltage detecting circuit of the insulation against ground resistance online test method of a kind of photovoltaic combining inverter of the present invention is realized schematic diagram.
Fig. 4 is that the circuit of upper brachium pontis, lower brachium pontis, resistance switch circuit, power frequency codan, filtering circuit, voltage follower circuit and isolating amplifier circuit of the insulation against ground resistance online test method of a kind of photovoltaic combining inverter of the present invention is realized schematic diagram.
In Fig. 2, Fig. 3 and Fig. 4, include:
1---upper brachium pontis 2---resistance switch circuit
3---PV voltage detecting circuit 4---warning circuit
The lower brachium pontis of 5---microprocessors 6---
7---power frequency codan 8---filtering circuit
9---voltage follower circuit 10---isolating amplifier circuit
11---Boost circuit and inverter circuit.
Embodiment
The present invention is further illustrated below in conjunction with accompanying drawing.
The insulation against ground resistance online test method of a kind of photovoltaic combining inverter of the present invention, shown in Fig. 2～4, it may further comprise the steps:
A: the output voltage V of sampling photovoltaic cell
PV
B: make the switch S 1 in the resistance switch circuit 2 be in off-state, resistance R 5 is broken away from from upper brachium pontis 1, after the processing of voltage signal Vo1 through power frequency codan 7, filtering circuit 8, voltage follower circuit 9 and isolating amplifier circuit 10 of the resistance R 3 of lower brachium pontis 6, the output of R4 dividing potential drop, obtain output signal Vad1, the pass of Vad1 and Vo1 is:
Setting R+ is the positive pole insulation resistance over the ground of photovoltaic cell, and R-is the negative pole insulation resistance over the ground of photovoltaic cell, according to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis 6 of upper brachium pontis 1, the relation of R4 dividing potential drop, obtains following formula:
C: make the switch S 1 in the resistance switch circuit 2 be in closure state, in upper brachium pontis 1 circuit of resistance R 5 accesses, after the processing of voltage signal Vo2 through power frequency codan 7, filtering circuit 8, voltage follower circuit 9 and isolating amplifier circuit 10 of the resistance R 3 of lower brachium pontis 6, the output of R4 dividing potential drop, obtain output signal Vad2, the pass of Vad2 and Vo2 is:
According to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis 6 of upper brachium pontis 1, the relation of R4 dividing potential drop, obtain following formula:
(4)
D: the positive pole that obtains two groups of photovoltaic cells by step B and C over the ground with the negative pole voltage ratio equation over the ground of photovoltaic cell, wherein unknown parameter is R+ and R-, carry out computing (present embodiment is by microprocessor 5 computings) and try to achieve the resistance value of R+ and R-, process is derived as follows:
Can get formula (1) substitution formula (2), formula (3) substitution formula (4) respectively:
Because V
PV, Vad1, Vad2 be the numerical value that sampling (all sampling input to microprocessor 5) obtains, order
Then can obtain:
Thereby try to achieve the resistance value of R+ and R-;
Wherein, described upper brachium pontis 1 comprises resistance R 1, R2, and an end of resistance R 1 is connected with the positive pole of photovoltaic cell, and the other end of resistance R 1 is connected with an end of resistance R 2, another termination the earth of resistance R 2; Described lower brachium pontis 6 comprises resistance R 3, R4, and a termination the earth of resistance R 3, the other end of resistance R 3 are the dividing potential drop output terminal of lower brachium pontis 6, and an end of resistance R 4 is connected with the dividing potential drop output terminal of lower brachium pontis 6, and the other end of resistance R 4 is connected with the negative pole of photovoltaic cell.Certainly, described upper brachium pontis 1 and lower brachium pontis 6 also can be for alternate manner consist of, for example: be made of a plurality of resistance parallel connections, what be not limited only to that present embodiment selects is made of two resistance series connection.
Wherein, described resistance switch circuit 2 comprises resistance R 5, switch S 1, one end of resistance R 5 is connected with the positive pole of photovoltaic cell, the other end of resistance R 5 is connected with the first end (being the pin one of switch S 1) of switch S 1, the second end of switch S 1 (being the pin two of switch S 1) connects the earth, and the control end of switch S 1 (being the pin 3 of switch S 1) is the control end of resistance switch circuit 2.Switch S 1 is solid-state relay, and in when work, the control end by switch S 1 can gauge tap S1 disconnects or closed, thereby corresponding controlling resistance R5 breaks away from from upper brachium pontis 1 or accesses in the brachium pontis 1.Certainly, described resistance switch circuit 2 also can be for alternate manner consists of, and what be not limited only to that present embodiment selects is made of resistance and switch series connection.
Wherein, described power frequency codan 7 is bypass filter capacitor C1, and the end of bypass filter capacitor C1 is connected with the dividing potential drop output terminal of lower brachium pontis 6, and the other end of bypass filter capacitor C1 is connected with the negative pole of photovoltaic cell; Certainly, described power frequency codan 7 also can be the circuit of other filtering mode, such as: the filtering modes such as LC, CLC are not limited only to the bypass filtering mode that present embodiment is selected.
Wherein, described filtering circuit 8 comprises resistance R 6, capacitor C 2, one end of resistance R 6 is connected with the end of bypass filter capacitor C1, and the other end of resistance R 6 is connected with the input end of voltage follower circuit 9, an end of capacitor C 2, and the other end of capacitor C 2 is connected with the negative pole of photovoltaic cell; Described voltage follower circuit 9 is made of operational amplifier U1A, the in-phase input end of operational amplifier U1A (being the pin 3 of operational amplifier U1A) is the input end of voltage follower circuit 9, the inverting input of operational amplifier U1A (being the pin two of operational amplifier U1A) is connected with the output terminal (being the pin one of operational amplifier U1A) of operational amplifier U1A, the power supply of the power supply of operational amplifier U1A anodal (being the pin 8 of operational amplifier U1A) and the pwm chip of the accessory power supply module of photovoltaic combining inverter (+VCCP) being connected, the power supply negative pole of operational amplifier U1A is connected with the negative pole of photovoltaic cell (being the pin 4 of operational amplifier U1A).
Wherein, described isolating amplifier circuit 10 comprises resistance R 7, R8, R9, R10, capacitor C 3, C4, C5, C6, operational amplifier U1B, operational amplifier U2A, linear optical coupling U3; One end of resistance R 7 (being the input end of isolating amplifier circuit 10) is connected with the output terminal of operational amplifier U1A, one end of the other end of resistance R 7 and capacitor C 3, the inverting input of operational amplifier U1B (being the pin 6 of operational amplifier U1B), one end of capacitor C 4,3 pin of linear optical coupling U3 connect, the other end of capacitor C 3, the in-phase input end of operational amplifier U1B (being the pin 5 of operational amplifier U1B), 4 pin of linear optical coupling U3 all are connected with the negative pole of photovoltaic cell, the output terminal of the other end of capacitor C 4 and operational amplifier U1B (being the pin 7 of operational amplifier U1B), one end of resistance R 8 connects, the other end of resistance R 8 is connected with 1 pin of linear light idol U3,2 pin of linear optical coupling U3 are connected with the power supply of the pwm chip of the accessory power supply module of photovoltaic combining inverter, 6 pin of linear optical coupling U3 and the inverting input of operational amplifier U2A (being the pin two of operational amplifier U2A), one end of capacitor C 5, one end of resistance R 9 connects, the other end of capacitor C 5, the other end of resistance R 9, one end of resistance R 10 all is connected with the output terminal (being the pin one of operational amplifier U2A) of operational amplifier U2A, the other end of resistance R 10 is the output terminal of isolating amplifier circuit 10, one end of capacitor C 6 is connected with the output terminal of isolating amplifier circuit 10,5 pin of linear optical coupling U3, the in-phase input end of operational amplifier U2A (being the pin 3 of operational amplifier U2A), the other end of capacitor C 6 all connects simulation ground (AGND), the power supply of operational amplifier U2A anodal (being the pin 8 of operational amplifier U2A) is connected with the power supply+VCCA of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U2A (being the pin 4 of operational amplifier U2A) is connected with the power supply-VCCA of photovoltaic combining inverter.
Behind step D, also comprise step e: whether the resistance value of judging R+ and R-satisfies the safety requirement.Wherein, insulation against ground safety requirement according to photovoltaic combining inverter, the positive pole of photovoltaic cell insulation resistance and negative pole insulation resistance over the ground over the ground will satisfy standard greater than 1K Ω/V, and therefore, the resistance of R+ and R-will satisfy formula (11) and (12):
After step e, also comprise step F: according to result of determination, carry out next step action of photovoltaic combining inverter, if the resistance value of R+ and R-satisfies the safety requirement, then allow photovoltaic combining inverter startup work, if do not satisfy the safety requirement, then forbid photovoltaic combining inverter startup work, and send alerting signal.
Steps A is to be photovoltaic cell by microprocessor 5 by PV() output voltage V of voltage detecting circuit 3 sampling photovoltaic cells
PVWherein, the first test side of PV voltage detecting circuit 3 is connected with the positive pole of photovoltaic cell, the second test side of PV voltage detecting circuit 3 is connected with the negative pole of photovoltaic cell, and the output terminal of PV voltage detecting circuit 3 is connected with the 2nd A/D input port (A/D_2) of microprocessor 5.PV voltage detecting circuit 3 can adopt differential amplifier circuit, can isolate accurately sampling to the output voltage of photovoltaic cell by differential amplifier circuit.Certainly, described PV voltage detecting circuit 3 also can be the sample circuit of other type, and for example: voltage sensor isolation sample circuit is not limited only to the differential amplifier circuit that present embodiment is selected.
Please refer to Fig. 3, specifically, in the present embodiment, PV voltage detecting circuit 3 comprises resistance R 11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, capacitor C 7, C8, C9, operational amplifier U4A; Resistance R 11, R12, R13, R14, R15, after R16 connects successively, one end is connected with the negative pole of photovoltaic cell, the other end is connected with the inverting input (being the pin two of operational amplifier U4A) of operational amplifier U4A, an end that is resistance R 11 is the second test side of PV voltage detecting circuit 3, the other end of resistance R 11 is connected with an end of resistance R 12, the other end of resistance R 12 is connected with an end of resistance R 13, the other end of resistance R 13 is connected with an end of resistance R 14, the other end of resistance R 14 is connected with an end of resistance R 15, the other end of resistance R 15 is connected with an end of resistance R 16, and the other end of resistance R 16 is connected with the inverting input of operational amplifier U4A; Resistance R 18, R19, R20, R21, R22, after R23 connects successively, one end is connected with the positive pole of photovoltaic cell, the other end is connected with the in-phase input end (being the pin 3 of operational amplifier U4A) of operational amplifier U4A, an end that is resistance R 18 is the first test side of PV voltage detecting circuit 3, the other end of resistance R 18 is connected with an end of resistance R 19, the other end of resistance R 19 is connected with an end of resistance R 20, the other end of resistance R 20 is connected with an end of resistance R 21, the other end of resistance R 21 is connected with an end of resistance R 22, the other end of resistance R 22 is connected with an end of resistance R 23, and the other end of resistance R 23 is connected with the in-phase input end of operational amplifier U4A; After resistance R 17 and capacitor C 7 were in parallel, an end was connected with the inverting input of operational amplifier U4A, and the other end is connected with the output terminal (being the pin one of operational amplifier U4A) of operational amplifier U4A; After resistance R 24 and capacitor C 8 were in parallel, an end was connected with the in-phase input end of operational amplifier U4A, another termination simulation ground (AGND); One end of resistance R 25 is connected with the output terminal of operational amplifier U4A, and the other end of resistance R 25 is the output terminal of PV voltage detecting circuit 3; One end of capacitor C 9 is connected with the output terminal of PV voltage detecting circuit 3, another termination simulation ground of capacitor C 9; The power supply of operational amplifier U4A anodal (being the pin 8 of operational amplifier U4A) is connected with the power supply+VCCA of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U4A (being the pin 4 of operational amplifier U4A) is connected with the power supply-VCCA of photovoltaic combining inverter.Wherein, circuit parameter satisfies following relation:
R11+R12+R13+R14+R15+R16= R18+R19+R20+R21+R22+R23；
R17=R24。
The model of above-mentioned operational amplifier U1A, operational amplifier U1B, operational amplifier U2A, operational amplifier U4A is LM258, and the model of linear optical coupling U3 is HCNR200.Certainly, model and the parameter value of above-mentioned electronic devices and components are only for reference, when the implementation the technical program, can make amendment according to actual environment.
The control end of resistance switch circuit 2 is connected with an I/O port (I/O_1) of microprocessor 5, and microprocessor 5 is in by the switch S 1 in the control end controlling resistance on-off circuit 2 of resistance switch circuit 2 and disconnects or closure state.
Microprocessor 5 is the voltage signals by the dividing potential drop output terminal of described power frequency codan 7, filtering circuit 8, voltage follower circuit 9 and the lower brachium pontis 6 of isolating amplifier circuit 10 samplings; Wherein, the output terminal of isolating amplifier circuit 10 is connected with an A/D input port (A/D_1) of described microprocessor 5.
Microprocessor 5 adopts the FIR digital filtering algorithm, microprocessor 5 is made further digital filtering by the FIR digital filtering algorithm to the A/D sampled signal and is processed, effectively eliminate the electrical network power frequency component to impact of the present invention, and the computation process of FIR digital filtering algorithm is succinct, computational accuracy is high; This microprocessor 5 is the DSP microprocessor, and the DSP microprocessor has the advantages such as powerful data-handling capacity and high travelling speed.
Microprocessor 5 is provided with the 2nd I/O port, and the 2nd I/O port is connected with warning circuit 4, and microprocessor 5 sends alerting signal by the 2nd I/O port driver warning circuit 4.In step F, when the R+ that calculates when microprocessor 5 and the resistance of R-did not satisfy safety and require, then microprocessor 5 can drive warning circuits 4 and send alerting signal, with call user's attention.
Microprocessor 5 is provided with the pwm signal port, the pwm signal port is connected with Boost circuit and the inverter circuit 11 of photovoltaic combining inverter, and microprocessor 5 is controlled the photovoltaic combining inverter startup work that whether allows by Boost circuit and the inverter circuit 11 of pwm signal port controlling photovoltaic combining inverter.In step F, when the R+ that calculates when microprocessor 5 and the resistance of R-satisfied safety and require, then microprocessor 5 allowed Boost circuit and the inverter circuit 11 startup work of photovoltaic combining inverters, namely allows photovoltaic combining inverter startup work; The R+ that calculates when microprocessor 5 and the resistance of R-do not satisfy the safety requirement, and then microprocessor 5 can by Boost circuit and the inverter circuit 11 startup work of pwm signal port blocking photovoltaic combining inverter, namely be forbidden photovoltaic combining inverter startup work.
In sum, computation process of the present invention is succinct, accuracy of detection is high, has realized that the online of negative pole insulation against ground resistance of the anodal insulation against ground resistance of photovoltaic cell and photovoltaic cell detects in real time, has guaranteed that photovoltaic combining inverter works safely and reliably.
Should be noted that at last; above embodiment is only in order to illustrate technical scheme of the present invention; but not limiting the scope of the invention; although with reference to preferred embodiment the present invention has been done to explain; those of ordinary skill in the art is to be understood that; can make amendment or be equal to replacement technical scheme of the present invention, and not break away from essence and the scope of technical solution of the present invention.
Claims (9)
1. the insulation against ground resistance online test method of a photovoltaic combining inverter, it is characterized in that: it may further comprise the steps:
A: the output voltage V of sampling photovoltaic cell
PV
B: make the switch S 1 in the resistance switch circuit be in off-state, resistance R 5 is broken away from from upper brachium pontis, after the processing of voltage signal Vo1 through power frequency codan, filtering circuit, voltage follower circuit and isolating amplifier circuit of the resistance R 3 of lower brachium pontis, the output of R4 dividing potential drop, obtain output signal Vad1, the pass of Vad1 and Vo1 is:
Setting R+ is the positive pole insulation resistance over the ground of photovoltaic cell, and R-is the negative pole insulation resistance over the ground of photovoltaic cell, according to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis of upper brachium pontis, the relation of R4 dividing potential drop, obtains following formula:
C: make the switch S 1 in the resistance switch circuit be in closure state, in the upper bridge arm circuit of resistance R 5 accesses, after the processing of voltage signal Vo2 through power frequency codan, filtering circuit, voltage follower circuit and isolating amplifier circuit of the resistance R 3 of lower brachium pontis, the output of R4 dividing potential drop, obtain output signal Vad2, the pass of Vad2 and Vo2 is:
According to the resistance R 3 of resistance R 1, R2 and the lower brachium pontis of upper brachium pontis, the relation of R4 dividing potential drop, obtain following formula:
D: the positive pole that obtains two groups of photovoltaic cells by step B and C over the ground with the negative pole voltage ratio equation over the ground of photovoltaic cell, wherein unknown parameter is R+ and R-, carries out the resistance value that R+ and R-are tried to achieve in computing, process is derived as follows:
Can get formula (1) substitution formula (2), formula (3) substitution formula (4) respectively:
Because V
PV, Vad1, Vad2 be the numerical value that obtains of sampling, order
Then can obtain:
Thereby try to achieve the resistance value of R+ and R-;
Wherein, described upper brachium pontis comprises resistance R 1, R2, and an end of resistance R 1 is connected with the positive pole of photovoltaic cell, and the other end of resistance R 1 is connected with an end of resistance R 2, another termination the earth of resistance R 2; Described lower brachium pontis comprises resistance R 3, R4, and a termination the earth of resistance R 3, the other end of resistance R 3 are the dividing potential drop output terminal of lower brachium pontis, and an end of resistance R 4 is connected with the dividing potential drop output terminal of lower brachium pontis, and the other end of resistance R 4 is connected with the negative pole of photovoltaic cell; Described resistance switch circuit comprises resistance R 5, switch S 1, one end of resistance R 5 is connected with the positive pole of photovoltaic cell, the other end of resistance R 5 is connected with the first end of switch S 1, the second termination the earth of switch S 1, and the control end of switch S 1 is the control end of resistance switch circuit;
Described power frequency codan is bypass filter capacitor C1, and the end of bypass filter capacitor C1 is connected with the dividing potential drop output terminal of lower brachium pontis, and the other end of bypass filter capacitor C1 is connected with the negative pole of photovoltaic cell; Described filtering circuit comprises resistance R 6, capacitor C 2, one end of resistance R 6 is connected with the end of bypass filter capacitor C1, the other end of resistance R 6 is connected with an end of the input end of voltage follower circuit, capacitor C 2, and the other end of capacitor C 2 is connected with the negative pole of photovoltaic cell; Described voltage follower circuit is made of operational amplifier U1A, the in-phase input end of operational amplifier U1A is the input end of voltage follower circuit, the inverting input of operational amplifier U1A is connected with the output terminal of operational amplifier U1A, the power supply positive pole of operational amplifier U1A is connected with the power supply of the pwm chip of the accessory power supply module of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U1A is connected with the negative pole of photovoltaic cell;
Described isolating amplifier circuit comprises resistance R 7, R8, R9, R10, capacitor C 3, C4, C5, C6, operational amplifier U1B, operational amplifier U2A, linear optical coupling U3; One end of resistance R 7 is connected with the output terminal of operational amplifier U1A, one end of the other end of resistance R 7 and capacitor C 3, the inverting input of operational amplifier U1B, one end of capacitor C 4,3 pin of linear optical coupling U3 connect, the other end of capacitor C 3, the in-phase input end of operational amplifier U1B, 4 pin of linear optical coupling U3 all are connected with the negative pole of photovoltaic cell, the output terminal of the other end of capacitor C 4 and operational amplifier U1B, one end of resistance R 8 connects, the other end of resistance R 8 is connected with 1 pin of linear optical coupling U3,2 pin of linear optical coupling U3 are connected with the power supply of the pwm chip of the accessory power supply module of photovoltaic combining inverter, 6 pin of linear optical coupling U3 and the inverting input of operational amplifier U2A, one end of capacitor C 5, one end of resistance R 9 connects, the other end of capacitor C 5, the other end of resistance R 9, one end of resistance R 10 all is connected with the output terminal of operational amplifier U2A, the other end of resistance R 10 is the output terminal of isolating amplifier circuit, one end of capacitor C 6 is connected with the output terminal of isolating amplifier circuit, 5 pin of linear optical coupling U3, the in-phase input end of operational amplifier U2A, the other end of capacitor C 6 all connects simulation ground, the power supply of operational amplifier U2A is anodal to be connected with the power supply+VCCA of photovoltaic combining inverter, and the power supply negative pole of operational amplifier U2A is connected with the power supply-VCCA of photovoltaic combining inverter.
2. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 1, it is characterized in that: behind step D, also comprise step e: whether the resistance value of judging R+ and R-satisfies the safety requirement.
3. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 2, it is characterized in that: after step e, also comprise step F: according to result of determination, carry out next step action of photovoltaic combining inverter, if the resistance value of R+ and R-satisfies the safety requirement, then allow photovoltaic combining inverter startup work, if do not satisfy the safety requirement, then forbid photovoltaic combining inverter startup work, and send alerting signal.
4. according to claim 1 to the insulation against ground resistance online test method of the described photovoltaic combining inverter of 3 any one, it is characterized in that: described steps A is by the output voltage V of microprocessor by PV voltage detecting circuit sampling photovoltaic cell
PVWherein, the first test side of described PV voltage detecting circuit is connected with the positive pole of photovoltaic cell, the second test side of described PV voltage detecting circuit is connected with the negative pole of photovoltaic cell, and the output terminal of described PV voltage detecting circuit is connected with the 2nd A/D input port of described microprocessor.
5. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 4, it is characterized in that: the control end of described resistance switch circuit is connected with an I/O port of described microprocessor, and described microprocessor is in by the switch S 1 in the control end controlling resistance on-off circuit of resistance switch circuit and disconnects or closure state.
6. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 5 is characterized in that: described microprocessor is the voltage signal by the dividing potential drop output terminal of described power frequency codan, filtering circuit, voltage follower circuit and the lower brachium pontis of isolating amplifier circuit sampling; Wherein, the output terminal of described isolating amplifier circuit is connected with an A/D input port of described microprocessor.
7. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 6, it is characterized in that: described microprocessor adopts the FIR digital filtering algorithm that the A/D sampled signal is made further digital filtering and processes, and this microprocessor is the DSP microprocessor.
8. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 6, it is characterized in that: described microprocessor is provided with the 2nd I/O port, the 2nd I/O port is connected with warning circuit, and microprocessor sends alerting signal by the 2nd I/O port driver warning circuit.
9. the insulation against ground resistance online test method of photovoltaic combining inverter according to claim 6, it is characterized in that: described microprocessor is provided with the pwm signal port, the pwm signal port is connected with Boost circuit and the inverter circuit of photovoltaic combining inverter, and described microprocessor is controlled the photovoltaic combining inverter startup work that whether allows by Boost circuit and the inverter circuit of pwm signal port controlling photovoltaic combining inverter.
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