CN111650450B - Identification method based on direct current mutual string identification device - Google Patents
Identification method based on direct current mutual string identification device Download PDFInfo
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- CN111650450B CN111650450B CN202010259732.8A CN202010259732A CN111650450B CN 111650450 B CN111650450 B CN 111650450B CN 202010259732 A CN202010259732 A CN 202010259732A CN 111650450 B CN111650450 B CN 111650450B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The invention discloses an identification method based on a direct current mutual string identification device, wherein a switch K1 and a switch K2 are alternatively closed in a ping-pong mode, and the voltages to the ground of the positive electrode and the negative electrode of 2 sets of direct current power supplies are measured through a voltage sampling module; comparing the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies, switching a load switch if the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies are approximately equal, and judging that the two electrodes are connected in series if the output current of the power supplies does not change obviously when the two power supplies are switched to the two power supplies respectively; if the output current of the power supply changes, the single-pole mutual series is judged; if the voltages of the positive and negative electrodes of the 2 sets of direct current power supplies are not equal to the voltages of the ground, the two sets of direct current power supplies are judged to be connected in series. The invention has the following beneficial effects: the method is simple and reliable, and can accurately identify 4 types of direct-current inter-series positive-positive ring network, negative-negative ring network, positive-positive and negative-negative ring network, and positive-negative ring network.
Description
Technical Field
The invention relates to the technical field of direct current ring networks, in particular to a recognition method based on a direct current cross-string recognition device, which is simple and reliable and can accurately recognize direct current cross-string types.
Background
The phenomenon of electrical connection easily appears in two sets of the same direct current systems, and then can cause the looped network trouble to appear in the system. In the operation process of a direct current system of a transformer substation, the direct current ring network problem is the most common fault in the faults of the direct current system. The two direct current systems have a common negative level and a common positive level, or when the positive and negative poles are connected together at the same time, namely, homopolar looped networks. If the grounding phenomenon occurs on any one of the positive electrode and the negative electrode, the relay protection cannot be started according to normal conditions, and the function of the relay protection device cannot be normally exerted. If the common problems are not solved in time, the common problems bring great harm to the power system. The second type of looped network problem is mainly that the direct current system anode and cathode at two ends are connected with the looped network through coils, resistors and the like, namely the heteropolar looped network, which is another common fault in the transformer substation. The heteropolar ring network and the homopolar ring network can be quickly distinguished through voltage characteristics, but the specific types of the homopolar ring networks cannot be effectively distinguished.
The direct current system looped network fault circuit model analyzes that the direct current system looped network fault is that an effective electric loop exists in2 sections of independent direct current systems; the fault of the direct current system looped network is divided into: positive-positive looped network, negative-negative looped network, positive-positive and negative-negative looped network, positive-negative looped network.
1. Anode looped network
As shown in fig. 1, 2 sets of independent dc power supply positive electrodes are electrically connected, and an effective electrical loop is formed by two sections of the balanced bridge; the anode ring network has the characteristics that: the voltage of the anode of 2 sets of direct current systems is equal to the voltage of the cathode of the 2 sets of direct current systems, and the voltage of the cathode of the 2 sets of direct current systems may be different.
2. Negative ring network
As shown in fig. 2, 2 sets of independent dc power supplies are electrically connected at their cathodes, and form an effective electrical loop through two segments of balanced bridges; (ii) a The anode looped network is characterized in that: the voltage of the cathodes of the 2 sets of direct current systems is equal to the voltage of the grounds, and the voltage of the anodes of the 2 sets of direct current systems may be unequal.
3. Two-pole ring network
As shown in fig. 3, 2 sets of independent dc power supplies are electrically connected in the positive and negative poles, and 2 sets are operated in parallel. FIG. 3 is a graph showing the following relationship; the two-pole ring network has the characteristics that: the voltage of the 2 sets of direct current system buses, the voltage of the anode to ground and the voltage of the cathode to ground are equal.
4. Heteropolar looped network
As shown in fig. 4 and 5, the heteropolar ring network is formed by connecting equipment between the positive and negative poles of two independent power supplies, and a fault loop forms an effective electrical loop through a load, a balance bridge and the ground. The heteropolar looped network has the characteristics that: the bus voltage, the positive voltage to ground and the negative voltage to ground of the 2 sets of direct current systems are different; the positive voltage to ground of one segment is approximately equal to the negative voltage to ground of the other segment; when the resistance difference of the balance bridge is large, the voltage of the ground-to-ground electrode is larger than the voltage of the bus, and the voltage of the other electrode is opposite to the voltage of the ground-to-ground electrode.
Disclosure of Invention
The invention provides a recognition method based on a direct current mutual string recognition device, which is simple and reliable and can accurately recognize direct current mutual string types, in order to overcome the defect that the specific types of homopolar ring networks in the prior art cannot be effectively recognized and distinguished.
In order to achieve the purpose, the invention adopts the following technical scheme:
a recognition method based on a direct current mutual string recognition device is disclosed, wherein the direct current mutual string recognition device comprises 2 direct current power supplies, 2 direct current insulation detection units and a load unit; the direct-current insulation detection unit comprises an MCU, a voltage sampling circuit, a current sampling circuit and a detection bridge circuit; the detection bridge circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch K1 and a switch K2; the resistor R1 is electrically connected with the resistor R2, the switch K1 is electrically connected with the resistor R3 and the switch K2 respectively, the switch K2 is electrically connected with the resistor R4, and the resistor R1, the resistor R2, the resistor R3 and the resistor R4 are all electrically connected with the direct-current power supply and the load unit; the direct current power supply is respectively and electrically connected with the MCU, the voltage sampling circuit, the current sampling circuit and the load unit, the MCU is respectively and electrically connected with the voltage sampling circuit and the current sampling circuit, and the load unit is respectively connected with the voltage sampling circuit and the current sampling circuit; the method comprises the following steps:
(1-1) alternately closing a switch K1 and a switch K2 in a ping-pong manner, and measuring the voltages to the ground of the positive and negative electrodes of 2 sets of direct current power supplies through a voltage sampling module;
(1-2) comparing the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies, and turning to the step (1-3) if the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies are approximately equal; if the voltages of the positive and negative electrodes of the 2 sets of direct current power supplies to the ground are not equal, the two sets of direct current power supplies are judged to be connected in series in different polarities;
(1-3) switching a load switch, and judging that the two power supplies are connected in series with each other in a bipolar manner if the output current of the power supplies is not obviously changed when the load switch is respectively switched to the two power supplies; and if the output current of the power supply changes, determining that the power supply is in single-pole mutual series.
The invention obtains the positive and negative voltage values of 2 direct current systems through a voltage acquisition circuit, determines the mutual series mode of the direct current systems by comparing the mutual relation of the positive and negative voltage values, and determines whether the systems are homopolar mutual series or heteropolar mutual series; if the voltage is detected to be homopolar mutual series and the direct current system voltage is approximately equal, the homopolar mutual series detection is started to obtain a final detection result; the method is simple and reliable, and can accurately identify the type of the direct current cross-serial.
Preferably, the load unit comprises a power load Rp and 4 load switches; the 4 switches are switches Ka +, switches Ka-, switches Kb + and switches Kb-; the power load Rp is electrically connected with each switch, and each switch is electrically connected with the direct-current power supply, the voltage sampling circuit, the current sampling circuit and the detection bridge circuit; the method is characterized in that the steps (1-3) are as follows:
(2-1) turning off all the load switches, and obtaining a current Ia0 on the left side of the load unit and a current Ib0 on the right side of the load unit through the current sampling circuit;
(2-2) closing the switch Ka + and the switch Ka-at the same time, and obtaining a current Ia1 on the left side of the load unit and a current Ib1 on the right side of the load unit through the current sampling circuit;
(2-3) simultaneously closing the switch Kb + and the switch Kb-, and obtaining a current Ia2 on the left side of the load unit and a current Ib2 on the right side of the load unit through the current sampling circuit;
(2-4) comparing the current magnitude twice, if the same power supply current has no change basically, namely Ia1 ≈ Ia2 and Ib1 ≈ Ib2, judging the two-pole mutual string of the power supply, and otherwise judging the single-pole mutual string.
Preferably, the determination process of the unipolar mutual string is as follows:
(3-1) all load switches are disconnected, and the switch Ka + is closed;
(3-2) closing the switch Ka-, and obtaining a current Ia4 on the left side of the load unit and a current Ib4 on the right side of the load unit through the current sampling circuit;
(3-3) opening the switch Ka-, closing the switch Kb-, and obtaining the current Ia5 on the left side of the load unit and the current Ib5 on the right side of the load unit through the current sampling circuit;
(3-4) comparing the current before and after each power supply is switched, and if the current of the same power supply is basically unchanged, namely Ia4 is approximately equal to Ia5, and Ib4 is approximately equal to Ib5, judging that the current single-pole cross-string is a negative pole-negative pole cross-string; otherwise, switching to the step (3-5);
(3-5) comparing current change sizes Ir1 and Ir2 before and after each power supply is switched, wherein Ir1 is Ia4-Ia5, and Ir2 is Ib5-Ib 4; and if the current change size is approximately equal to the load current before and after the negative switch of the same power supply is switched, namely Ir1 is approximately equal to Ir2, the current unipolar mutual string is judged to be a positive-positive stage mutual string.
Preferably, the specific steps of step (1-1) are as follows:
(4-1) opening the switch K1, closing the switch K2, and obtaining the anode-to-ground voltage Va1+ on the left side of the load unit, the cathode-to-ground voltage Va1-, the anode-to-ground voltage Vb1+ on the right side of the load unit and the cathode-to-ground voltage Vb 1-through the voltage acquisition circuit;
(4-2) closing the switch K1, opening the switch K2, and obtaining the anode-to-ground voltage Va2+ on the left side of the load unit, the cathode-to-ground voltage Va2-, the anode-to-ground voltage Vb2+ on the right side of the load unit and the cathode-to-ground voltage Vb 2-through the voltage acquisition circuit;
(4-3) comparing the obtained voltage values, if the anode voltage to ground and the cathode voltage to ground of the 2 direct current power supplies are not equal, namely Va1+ ≠ Va2+, Vb1+ ≠ Vb2+, Va1- ≠ Va2-, Vb1- ≠ Vb2-, judging that the two poles are in different-pole cross-string, and if not, switching to the step (1-3).
Preferably, the voltage sampling circuit comprises a resistance voltage dividing and RC filtering circuit, a voltage following circuit, a first voltage dividing and isolating operational amplifier circuit, a first differential operational amplifier circuit and an RC filtering and TVS tube protection circuit; the resistance voltage division and RC filter circuit, the voltage follower circuit, the first voltage division and isolation operational amplifier circuit, the first difference operational amplifier circuit, the RC filter and the TVS tube protection circuit are sequentially connected in series, the RC filter is electrically connected with the TVS tube protection circuit and the MCU, and the resistance voltage division is electrically connected with the RC filter circuit and the direct-current power supply.
Preferably, the current sampling circuit comprises a common-mode filtering and RC filtering circuit, a reference voltage and instrument operational amplifier circuit, a second voltage division and isolation operational amplifier circuit, a second differential operational amplifier circuit and an RC filtering circuit; the common-mode filtering and RC filter circuit, the reference voltage and instrument operational amplifier circuit, the second voltage division and isolation operational amplifier circuit, the second differential operational amplifier circuit and the RC filter circuit are sequentially connected in series, the common-mode filtering and RC filter circuit is connected with the DC power supply, and the RC filter circuit is respectively and electrically connected with the MCU, the detection bridge circuit and the load unit.
Preferably, the load unit may be a device independently or integrated into the dc insulation detection unit.
Therefore, the invention has the following beneficial effects: the method is simple and reliable, and can accurately identify 4 types of direct-current inter-series positive-positive ring network, negative-negative ring network, positive-positive and negative-negative ring network, and positive-negative ring network.
Drawings
FIG. 1 is a circuit diagram of the anode-cathode loop network of the present invention;
FIG. 2 is a circuit diagram of the negative-negative ring network of the present invention;
FIG. 3 is a circuit diagram of the positive-positive and negative-negative ring networks of the present invention;
FIG. 4 is a first circuit diagram of the anode-cathode loop network of the present invention;
FIG. 5 is a second circuit diagram of the anode-cathode loop network of the present invention;
FIG. 6 is a flow chart of the present invention;
FIG. 7 is a flow chart of the present invention for unipolar cross-string and bipolar cross-string determination;
FIG. 8 is a flow chart of the unipolar cross-string decision of the present invention;
FIG. 9 is a system block diagram of the present invention;
FIG. 10 is a circuit topology of the present invention;
FIG. 11 is a circuit diagram of the voltage acquisition circuit of the present invention;
FIG. 12 is a circuit diagram of the current acquisition module of the present invention;
FIG. 13 is a circuit diagram of the sense bridge circuit of the present invention;
fig. 14 is a circuit diagram of a load unit of the present invention.
In the figure: the circuit comprises a direct-current power supply 1, a direct-current insulation detection unit 2, a load unit 3, a data communication link 4, an MCU21, a voltage sampling circuit 22, a current sampling circuit 23, a detection bridge circuit 24, a resistance voltage division and RC filter circuit 221, a voltage follower circuit 222, a first voltage division and isolation operational amplifier circuit 223, a first differential operational amplifier circuit 224, an RC filter and TVS tube protection circuit 225, a common mode filter and RC filter circuit 231, a reference voltage and instrument operational amplifier circuit 232, a second voltage division and isolation operational amplifier circuit 233, a second differential operational amplifier circuit 234, an RC filter circuit 235, a balance bridge circuit 241 and an unbalanced bridge circuit 242.
Detailed Description
The invention is further described in the following detailed description with reference to the drawings in which:
the embodiment shown in fig. 6 is an identification method based on a dc cross-talk identification device, and as shown in fig. 9 and 10, the dc cross-talk identification device includes 2 dc power supplies 1, 2 dc insulation detection units 2 and a load unit 3; the direct current insulation detection unit comprises an MCU21, a voltage sampling circuit 22, a current sampling circuit 23 and a detection bridge circuit 24; a data communication link 4 is arranged between the direct current insulation detection unit and the load unit; the direct current power supply is respectively and electrically connected with the MCU, the voltage sampling circuit, the current sampling circuit and the load unit, the MCU is respectively and electrically connected with the voltage sampling circuit and the current sampling circuit, and the load unit is respectively connected with the voltage sampling circuit and the current sampling circuit; the data communication link comprises an RS485 communication module, a multimode optical fiber, a single-mode optical fiber and a CAN communication module; the load unit can be independently formed into a device and can also be integrated into the direct current insulation detection unit. As shown in fig. 13, the detection bridge circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch K1, and a switch K2; the resistor R1 is electrically connected with the resistor R2, the switch K1 is electrically connected with the resistor R3 and the switch K2 respectively, the switch K2 is electrically connected with the resistor R4, and the resistor R1, the resistor R2, the resistor R3 and the resistor R4 are all electrically connected with the direct-current power supply and the load unit; ideally, the insulation resistance of positive and negative grounds in a dc system tends to be infinite, and in order to deal with the ground fault of the dc system, two equal-sized balance resistors are usually added between the positive ground and the negative ground of the dc system, which are called as a balance bridge in the dc system. If the direct current system balance bridge is known, the grounding resistance value and the voltage to earth have definite one-to-one correspondence, and the grounding resistance value of the system can be conveniently calculated through the relationship to judge the health state of the system. The resistor R1 and the resistor R2 are balance resistors, and the resistor R3 and the resistor R4 are detection resistor resistors.
Through ping-pong principle division switching K1 and K2, positive and negative voltages to ground can be switched, positive and negative insulation resistance values of a direct current system can be deduced through a formula, and the insulation resistance value can also be calculated through the formula after the system has a two-pole balance insulation fault. And whether the two direct current systems are connected in series or not can be judged according to the voltage change rule.
As shown in fig. 11, the voltage sampling circuit includes a resistor voltage dividing and RC filtering circuit 221, a voltage follower circuit 222, a first voltage dividing and isolating operational amplifier circuit 223, a first differential operational amplifier circuit 224, and an RC filtering and TVS tube protection circuit 225; the resistance voltage division and RC filter circuit, the voltage follower circuit, the first voltage division and isolation operational amplifier circuit, the first difference operational amplifier circuit, the RC filter and the TVS tube protection circuit are sequentially connected in series, the RC filter is electrically connected with the TVS tube protection circuit and the MCU, and the resistance voltage division is electrically connected with the RC filter circuit and the direct-current power supply.
As shown in fig. 11, the resistance voltage dividing circuit is composed of 0.1% high-precision resistors R303, R304, R305, R311, R312 and R3106, and low-temperature drift resistors 25 PPM/deg.c, and is connected to pin 3 of the operational amplifier U300 OP07 through an RC filter circuit composed of a resistor R306 and a capacitor C309, according to the virtual short principle of the operational amplifier, the voltage of pin 2 and pin 3 of the operational amplifier U300 is equal, and pin 6 is connected to pin 2, so that the voltage of pin 6 is equal to the voltage of pin 2, and thus the voltage of pin 6 is equal to the voltage of pin 3, and the output voltage of the operational amplifier U300 is equal to the input voltage, thereby realizing the following function; u302 AMC1200BDWV is isolation operational amplifier, fixed amplification is 8 times, and a voltage division circuit is formed by a resistor R324 and a resistor R325 to limit the voltage between VinP and VinN; because the voltage between the input pins VinP and VinN of the U302 AMC1200BDWV must be less than 250mV, if the voltage exceeds the 250mV, the voltage overflows; the output voltages VoutP and VoutN of the U302 AMC1200BDWV output pin are respectively connected with a pin 3 of a U301 OP07 through a resistor R301 and connected with a pin 2 of a U301 OP07 through a resistor R314 to form a differential amplification circuit together with the resistor R300 and the resistor R313, the output voltage of a pin 6 of the U301 OP07 is sent to the MCU for data processing through an RC filter circuit formed by a resistor R308 and a capacitor C308, and the output voltage is clamped by a diode D300 BAT54S to be between AGND and VDDA; respectively setting the input voltage as Uin1 and the output voltage as Uout1, then
As shown in fig. 12, the current sampling circuit includes a common mode filtering and RC filtering circuit 231, a reference voltage and instrument operational amplifier circuit 232, a second voltage division and isolation operational amplifier circuit 233, a second differential operational amplifier circuit 234 and an RC filtering circuit 235; the common-mode filtering and RC filter circuit, the reference voltage and instrument operational amplifier circuit, the second voltage division and isolation operational amplifier circuit, the second differential operational amplifier circuit and the RC filter circuit are sequentially connected in series, the common-mode filtering and RC filter circuit is connected with the DC power supply, and the RC filter circuit is respectively and electrically connected with the MCU, the detection bridge circuit and the load unit.
As shown in fig. 12, the common mode filter circuit is composed of an L300 common mode filter inductor, and suppresses interference of an external signal to an input signal; the signal passes through L300, then passes through a filter capacitor C321, then forms a voltage signal with a resistor R319 and a resistor R328, passes through an RC filter circuit formed by a resistor R317, a capacitor C319, a resistor R330 and a capacitor C326, and is respectively connected with a pin 2 and a pin 3 of a U306 AD620ARZ-REEL instrument operational amplifier, the amplification factor is determined by connecting a pin 1 and a pin 8 with a resistor R315, and meanwhile, the U307 REF3312AIDBZR outputs a high-precision voltage of 1.25V to a pin 5 of the U306 AD620ARZ-REEL instrument operational amplifier to raise the voltage, so that the negative signal voltage can also pass through the U306 AD620ARZ-REEL instrument operational amplifier; u303 AMC1200BDWV is an isolation operational amplifier, fixed amplification is carried out by 8 times, and a voltage division circuit is formed by a resistor R342 and a resistor R356 to limit the voltage between VinP and VinN; because the voltage between the input pins VinP and VinN of the U303 AMC1200BDWV must be less than 250mV, if the voltage exceeds the 250mV, the voltage overflows; the output voltages VoutP and VoutN of the output pin VoutP and VoutN of the U303 AMC1200BDWV are respectively connected with the pin 3 and the pin 4 of the differential operational amplifier U305 OPA330 through a resistor R318 and a resistor R331, and form a differential amplifying circuit together with the resistor R316 and a resistor R329, the output voltage of the pin 1 of the differential operational amplifier U305 OPA330 is sent to the MCU for data processing through an RC filter circuit formed by a resistor R322 and a capacitor C325, and input signals and output voltages are respectively set as Uin2 and Uout2,
as shown in fig. 14, the load unit includes a power load Rp and 4 load switches; the 4 switches are switches Ka +, switches Ka-, switches Kb + and switches Kb-; the power load Rp is electrically connected with each switch, and each switch is electrically connected with the direct current power supply, the voltage sampling circuit, the current sampling circuit and the detection bridge circuit.
As shown in fig. 6, the identification method based on the dc cross-string identification apparatus includes the following steps:
step 100, alternately closing a switch K1 and a switch K2 in a ping-pong manner, and measuring the voltages to earth of the positive and negative electrodes of 2 sets of direct current power supplies through a voltage sampling module;
101, opening a switch K1, closing a switch K2, and obtaining anode-to-ground voltage Va1+ on the left side of the load unit, a cathode-to-ground voltage Va1-, anode-to-ground voltage Vb1+ and cathode-to-ground voltage Vb 1-on the right side of the load unit through a voltage acquisition circuit;
102, closing a switch K1, opening a switch K2, and obtaining anode-to-ground voltage Va2+ on the left side of the load unit, a cathode-to-ground voltage Va2-, anode-to-ground voltage Vb2+ on the right side of the load unit and cathode-to-ground voltage Vb 2-through a voltage acquisition circuit;
and 103, comparing the obtained voltage values, if the voltage to ground of the anode and the voltage to ground of the cathode of each of the 2 direct current power supplies are not equal, namely Va1+ ≠ Va2+, Vb1+ ≠ Vb2+, Va1- ≠ Va2-, and Vb1- ≠ Vb2-, judging that the two poles are in different-pole cross-string, and otherwise, switching to the step (1-3).
Step 200, comparing the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies, and if the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies are approximately equal, turning to step 300; if the voltages of the positive and negative electrodes of the 2 sets of direct current power supplies to the ground are not equal, the two sets of direct current power supplies are judged to be connected in series;
step 300, switching load switches, and judging that the two power supplies are connected in series with each other in a bipolar manner if the output current of the power supplies does not change obviously when the two power supplies are switched to the two power supplies respectively; if the output current of the power supply changes, the single-pole mutual series is judged;
step 301, turning off all load switches, and obtaining a current Ia0 on the left side of the load unit and a current Ib0 on the right side of the load unit through a current sampling circuit;
step 302, simultaneously closing the switch Ka + and the switch Ka-, and obtaining a current Ia1 on the left side of the load unit and a current Ib1 on the right side of the load unit through the current sampling circuit;
step 303, simultaneously closing the switch Kb + and the switch Kb-, and obtaining a current Ia2 on the left side of the load unit and a current Ib2 on the right side of the load unit through the current sampling circuit;
step 304, comparing the current magnitude of the two times, if the current of the same power supply is basically unchanged, namely Ia1 ≈ Ia2 and Ib1 ≈ Ib2, judging that the two poles of the power supply are mutually connected, otherwise, turning to step 305;
step 305, disconnecting all load switches and closing the switch Ka +;
step 306, closing the switch Ka-, and obtaining the current Ia4 on the left side of the load unit and the current Ib4 on the right side of the load unit through the current sampling circuit;
step 307, opening a switch Ka-, closing a switch Kb-, and obtaining a current Ia5 on the left side of the load unit and a current Ib5 on the right side of the load unit through a current sampling circuit;
step 308, comparing the current before and after each power supply is switched, and if the same power supply current is basically unchanged, namely Ia4 is approximately equal to Ia5, Ib4 is approximately equal to Ib5, judging that the current single-pole mutual string is a negative-negative mutual string; otherwise, the step (3-5) is carried out;
step 309, comparing current change magnitudes Ir1 and Ir2 before and after each power supply is switched, wherein Ir1 is Ia4-Ia5, and Ir2 is Ib5-Ib 4; and if the current change is approximately equal to the load current before and after the negative switch of the same power supply is switched, namely Ir1 is approximately equal to Ir2, and the current single-pole cross string is judged to be a positive-level cross string.
It should be understood that the present embodiment is only for illustrating the present invention and is not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
Claims (6)
1. A recognition method based on a direct current mutual string recognition device is characterized in that the direct current mutual string recognition device comprises 2 direct current power supplies (1), 2 direct current insulation detection units (2) and a load unit (3); the direct-current insulation detection unit comprises an MCU (microprogrammed control unit) (21), a voltage sampling circuit (22), a current sampling circuit (23) and a detection bridge circuit (24); the detection bridge circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch K1 and a switch K2; the resistor R1 is electrically connected with the resistor R2, the switch K1 is electrically connected with the resistor R3 and the switch K2 respectively, the switch K2 is electrically connected with the resistor R4, and the resistor R1, the resistor R2, the resistor R3 and the resistor R4 are all electrically connected with a direct current power supply and a load unit; the direct current power supply is respectively and electrically connected with the MCU, the voltage sampling circuit, the current sampling circuit and the load unit, the MCU is respectively and electrically connected with the voltage sampling circuit and the current sampling circuit, and the load unit is respectively connected with the voltage sampling circuit and the current sampling circuit; the load unit comprises a power load Rp and 4 load switches; the 4 switches are switches Ka +, switches Ka-, switches Kb + and switches Kb-; the power load Rp is electrically connected with each switch, and each switch is electrically connected with the direct-current power supply, the voltage sampling circuit, the current sampling circuit and the detection bridge circuit; the method comprises the following steps:
(1-1) alternately closing a switch K1 and a switch K2 in a ping-pong manner, and measuring the voltages to the ground of the positive and negative electrodes of 2 sets of direct current power supplies through a voltage sampling module;
(1-2) comparing the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies, and turning to the step (1-3) if the voltages to earth of the positive and negative electrodes of the 2 sets of direct current power supplies are approximately equal; if the voltages of the positive and negative electrodes of the 2 sets of direct current power supplies to the ground are not equal, the two sets of direct current power supplies are judged to be connected in series;
(1-3) switching a load switch, and judging that the two power supplies are connected in series with each other in a bipolar manner if the output current of the power supplies is not obviously changed when the load switch is respectively switched to the two power supplies; if the output current of the power supply changes, the single-pole mutual string is judged, and the method specifically comprises the following steps:
(2-1) turning off all the load switches, and obtaining a current Ia0 on the left side of the load unit and a current Ib0 on the right side of the load unit through the current sampling circuit;
(2-2) closing the switch Ka + and the switch Ka-at the same time, and obtaining a current Ia1 on the left side of the load unit and a current Ib1 on the right side of the load unit through the current sampling circuit;
(2-3) simultaneously closing the switch Kb + and the switch Kb-, and obtaining a current Ia2 on the left side of the load unit and a current Ib2 on the right side of the load unit through the current sampling circuit;
(2-4) comparing the current magnitude twice, if the same power supply current has no change basically, namely Ia1 ≈ Ia2 and Ib1 ≈ Ib2, judging the two-pole mutual string of the power supply, and otherwise judging the single-pole mutual string.
2. The identification method based on the direct current mutual string identification device as claimed in claim 1, wherein the judgment process of the single-pole mutual string is as follows:
(3-1) all load switches are disconnected, and the switch Ka + is closed;
(3-2) closing the switch Ka-, and obtaining a current Ia4 on the left side of the load unit and a current Ib4 on the right side of the load unit through the current sampling circuit;
(3-3) opening the switch Ka-, closing the switch Kb-, and obtaining a current Ia5 on the left side of the load unit and a current Ib5 on the right side of the load unit through the current sampling circuit;
(3-4) comparing the current before and after each power supply is switched, and if the current of the same power supply is basically unchanged, namely Ia4 is approximately equal to Ia5, and Ib4 is approximately equal to Ib5, judging that the current single-pole cross-string is a negative pole-negative pole cross-string; otherwise, the step (3-5) is carried out;
(3-5) comparing current change sizes Ir1 and Ir2 before and after each power supply is switched, wherein Ir1= Ia4-Ia5, and Ir2= Ib5-Ib 4; and if the current change is approximately equal to the load current before and after the negative switch of the same power supply is switched, namely Ir1 is approximately equal to Ir2, and the current single-pole cross string is judged to be a positive-level cross string.
3. The identification method based on the direct current mutual string identification device according to claim 1, wherein the specific steps of the step (1-1) are as follows:
(4-1) opening the switch K1, closing the switch K2, and obtaining the anode voltage to ground Va1+ on the left side of the load unit, the cathode voltage to ground Va1-, the anode voltage to ground Vb1+ on the right side of the load unit and the cathode voltage to ground Vb 1-through the voltage acquisition circuit;
(4-2) closing the switch K1, opening the switch K2, and obtaining the anode voltage to ground Va2+ on the left side of the load unit, the cathode voltage to ground Va2-, the anode voltage to ground Vb2+ on the right side of the load unit and the cathode voltage to ground Vb 2-through the voltage acquisition circuit;
(4-3) comparing the obtained voltage values, if the anode voltage to ground and the cathode voltage to ground of the 2 direct current power supplies are not equal, namely Va1+ ≠ Va2+, Vb1+ ≠ Vb2+, Va1- ≠ Va2-, Vb1- ≠ Vb2-, judging that the two poles are in different-pole cross-string, and if not, switching to the step (1-3).
4. The identification method based on the direct current mutual string identification device according to claim 1, wherein the voltage sampling circuit comprises a resistance voltage dividing and RC filtering circuit (221), a voltage following circuit (222), a first voltage dividing and isolating operational amplifier circuit (223), a first differential operational amplifier circuit (224), an RC filtering and TVS pipe protection circuit (225); resistance partial pressure and RC filter circuit, voltage follower circuit, first partial pressure and isolation operational amplifier circuit, first difference operational amplifier circuit, RC filtering and TVS pipe protection circuit establish ties in proper order, and the RC filtering is connected with TVS pipe protection circuit and MCU electricity, and resistance partial pressure is connected with RC filter circuit and DC power supply electricity.
5. The identification method based on the direct current mutual string identification device according to claim 1, wherein the current sampling circuit comprises a common mode filtering and RC filter circuit (231), a reference voltage and instrument operational amplifier circuit (232), a second voltage division and isolation operational amplifier circuit (233), a second differential operational amplifier circuit (234) and an RC filter circuit (235); the common-mode filtering and RC filter circuit, the reference voltage and instrument operational amplifier circuit, the second voltage division and isolation operational amplifier circuit, the second differential operational amplifier circuit and the RC filter circuit are sequentially connected in series, the common-mode filtering and RC filter circuit is connected with the DC power supply, and the RC filter circuit is respectively and electrically connected with the MCU, the detection bridge circuit and the load unit.
6. The identification method based on the direct current mutual string identification device as claimed in claim 1, 2, 4 or 5, wherein the load unit can be independently formed into a device or can be integrated into the direct current insulation detection unit.
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