CN110988577A - Capacitance polarity reversal detection method, device and computer readable medium - Google Patents

Capacitance polarity reversal detection method, device and computer readable medium Download PDF

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Publication number
CN110988577A
CN110988577A CN201911406864.2A CN201911406864A CN110988577A CN 110988577 A CN110988577 A CN 110988577A CN 201911406864 A CN201911406864 A CN 201911406864A CN 110988577 A CN110988577 A CN 110988577A
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voltage
series
branch
current
threshold
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李江
樊二珂
刘合松
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Siemens Electrical Drives Ltd
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Siemens Electrical Drives Ltd
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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

Abstract

The invention provides a method and a device for detecting reverse connection of capacitance polarity and a computer readable medium, wherein the method for detecting reverse connection of capacitance polarity comprises the following steps: determining a voltage threshold and a current threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch; respectively detecting branch voltage at two ends of each series branch; detecting the loop current output by the test power supply; if the branch voltage of at least one of the at least two series branches exceeds a voltage threshold, determining that electrolytic capacitors with reversed polarities exist in the at least two series branches; if the branch voltage of any one of the at least two series branches does not exceed the voltage threshold and the loop current exceeds the current threshold, determining that electrolytic capacitors with reversed polarities exist in the at least two series branches; if the loop current does not exceed the current threshold, it is determined that no oppositely connected electrolytic capacitors are present in the at least two series branches. The scheme can accurately detect the electrolytic capacitor with reversed polarity.

Description

Capacitance polarity reversal detection method, device and computer readable medium
Technical Field
The invention relates to the technical field of electrical engineering, in particular to a method and a device for detecting polarity reversal of a capacitor and a computer readable medium.
Background
An inverter is widely used in the field of motor control, and an electrolytic capacitor is provided on the dc bus side of the inverter in order to enable the inverter to output a stable dc power. The connection relation between the electrolytic capacitor and the direct current bus of the frequency converter is as follows: the plurality of electrolytic capacitors are connected in parallel to form a series branch, and the plurality of series branches are connected in series to form a loop and connected with a direct current bus of the frequency converter.
In order to ensure that the frequency converter after leaving the factory can be normally used, various functions and hardware structures of the frequency converter need to be detected before leaving the factory, which includes detecting whether an electrolytic capacitor with reversed polarity exists on the direct current bus side of the frequency converter, because the electricity storage capacity of the electrolytic capacitor is related to the direction of current passing through the electrolytic capacitor, if the polarity of the electrolytic capacitor is reversed, the voltage balance of each series branch circuit can be influenced, and the electrolytic capacitor can be damaged in serious cases.
At present, when detecting whether the polarity of an electrolytic capacitor on the direct current bus side of a frequency converter is reversely connected, the voltage of each series branch is detected respectively, and when the voltage of one series branch exceeds a set voltage threshold, it is determined that the electrolytic capacitor with the reverse polarity exists in the series branch.
Aiming at the existing method for detecting the polarity reversal of the capacitor, when the electrolytic capacitors with the polarity reversal do not exist in each series branch mutually connected in series at the direct current bus side of the frequency converter, each series branch has similar voltage division capability, each series branch equally divides the input voltage applied on the direct current bus, and when the electrolytic capacitors with the polarity reversal exist in each series branch, each series branch still has similar voltage division capability, each series branch still equally divides the input voltage applied on the direct current bus, namely when the electrolytic capacitors with the polarity reversal exist in each series branch and when the electrolytic capacitors with the polarity reversal do not exist in each series branch, the voltages of each series branch are the same, so that the condition of leakage connection can occur, and the electrolytic capacitors with the polarity reversal cannot be accurately detected.
Disclosure of Invention
In view of the above, the method, the apparatus and the computer readable medium for detecting polarity reversal of capacitor provided by the present invention can accurately detect the electrolytic capacitor with reversed polarity.
In a first aspect, an embodiment of the present invention provides a method for detecting a reverse polarity connection of a capacitor, including:
determining a voltage threshold and a current threshold according to the output voltage of a test power supply and the equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors which are connected in parallel, and at least two series branches are connected in series in sequence and then are connected with two poles of the test power supply;
respectively detecting branch voltage at two ends of each series branch;
detecting the loop current output by the test power supply;
judging whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold;
determining that the electrolytic capacitor with reversed polarity exists in the at least two series branches if the branch voltage of at least one of the series branches in the at least two series branches exceeds the voltage threshold;
if the branch voltage of any one of the at least two series branches does not exceed the voltage threshold, determining whether the loop current exceeds the current threshold;
determining that the electrolytic capacitors in the at least two series branches are in reverse polarity if the loop current exceeds the current threshold;
determining that the electrolytic capacitors in the at least two series branches are not in reverse polarity if the loop current does not exceed the current threshold.
Alternatively,
the determining the voltage threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch comprises:
calculating the voltage threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch by a first formula;
the first formula includes:
Figure BDA0002348884560000021
wherein, the VtFor characterizing the voltage threshold, theV is used for representing the output voltage of the test power supply, n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, and k is1For characterizing the voltage correction factor determined from the voltage acquisition error.
Alternatively,
the determining the current threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch comprises:
calculating the current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch circuit by using a second formula;
the second formula includes:
Figure BDA0002348884560000031
wherein, the ItThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, the V is used for representing the output voltage of the test power supply, the R is used for representing the sum of the equivalent impedances of each series branch, and the k is used for representing the sum of the equivalent impedances of each series branch2For characterizing the current correction factor determined from the current acquisition error.
Alternatively,
after the determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold, further comprising:
for each of the series branches, if the branch voltage of the series branch is less than the lower limit of the voltage threshold, determining that at least one electrolytic capacitor with reversed polarity exists in the series branch.
Alternatively,
after the determining whether the loop current exceeds the current threshold, further comprising:
and if the loop current exceeds the current threshold, determining that the electrolytic capacitors with reversed polarities exist in each series branch.
Alternatively,
for each of the series branches, the series branch comprises at least two of the electrolytic capacitors and at least one balancing resistor connected in parallel with each other, so that different series branches have the same equivalent impedance.
In a second aspect, an embodiment of the present invention further provides a device for detecting reverse connection of capacitance polarity, including:
the threshold value determining module is used for determining a voltage threshold value and a current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors which are mutually connected in parallel, and at least two series branches are connected with two poles of the test power supply after being sequentially connected in series;
the voltage detection module is used for respectively detecting the branch voltage at two ends of each series branch;
a current detection module for detecting the loop current output by the test power supply;
a voltage comparison module, configured to determine whether the branch voltage of at least one of the at least two serial branches exceeds the voltage threshold according to the voltage threshold determined by the threshold determination module and the branch voltage detected by the voltage detection module;
a first result output module, configured to determine that the electrolytic capacitors with reversed polarity exist in the at least two serial branches when the voltage comparison module determines that the branch voltage of at least one of the at least two serial branches exceeds the voltage threshold;
a current comparison module, configured to determine whether the loop current detected by the current detection module exceeds the current threshold determined by the threshold determination module after the voltage comparison module determines that the branch voltage of any one of the at least two serial branches does not exceed the voltage threshold;
a second result output module, configured to determine that the electrolytic capacitors with reversed polarities exist in the at least two serial branches when the current comparison module determines that the loop current exceeds the current threshold, and determine that the electrolytic capacitors with reversed polarities do not exist in the at least two serial branches when the current comparison module determines that the loop current does not exceed the current threshold.
Alternatively,
the threshold determination module comprises: a voltage threshold determination unit;
the voltage threshold determining unit is configured to calculate the voltage threshold according to the output voltage of the test power supply and the equivalent impedance of each of the series branches by using a first formula as follows;
the first formula includes:
Figure BDA0002348884560000041
wherein, the VtThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k is used for representing the voltage threshold, V is used for representing the output voltage of the test power supply, and n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the1For characterizing the voltage correction factor determined from the voltage acquisition error.
Alternatively,
the threshold determination module comprises: a current threshold determination unit;
the current threshold determining unit is configured to calculate the current threshold according to the output voltage of the test power supply and the equivalent impedance of each of the series branches by using a second formula as follows;
the second formula includes:
Figure BDA0002348884560000042
wherein, the ItThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, the V is used for representing the output voltage of the test power supply, the R is used for representing the sum of the equivalent impedances of each series branch, and the k is used for representing the sum of the equivalent impedances of each series branch2For characterizing the current correction factor determined from the current acquisition error.
Alternatively,
the first result output module is further configured to determine that at least one electrolytic capacitor with reversed polarity exists in the series branch when the voltage comparison module determines that the branch voltage of the series branch is smaller than the lower limit of the voltage threshold.
Alternatively,
the second result output module is further configured to determine that the electrolytic capacitors with reversed polarities exist in each of the series branches when the current comparison module determines that the loop current exceeds the current threshold.
In a third aspect, an embodiment of the present invention further provides another device for detecting reverse connection of capacitance polarity, including: at least one memory and at least one processor;
the at least one memory to store a machine readable program;
the at least one processor is configured to invoke the machine-readable program to perform the method according to the first aspect and any one of the possible implementation manners of the first aspect.
In a fourth aspect, the embodiment of the present invention further provides a computer-readable medium, where the computer-readable medium stores computer instructions, and when the computer instructions are executed by a processor, the processor is caused to execute any one of the capacitance polarity reversal detection methods provided in the first aspect.
According to the technical scheme, the voltage threshold and the current threshold are set according to the output voltage of the test power supply and the balance current of each series branch in advance, when the electrolytic capacitors with reversed polarities do not exist in each series branch, the branch voltage of each series branch does not exceed the set voltage threshold, and the loop current flowing through each series branch does not exceed the current threshold. When detecting whether electrolytic capacitors with reversed polarities exist, branch voltage of each series branch and loop current output by a test power supply are respectively detected, when the branch voltage of at least one series branch exceeds a voltage threshold, electrolytic capacitors with reversed polarities exist in at least one series branch, when the branch voltage of all series branches does not exceed the voltage threshold, whether electrolytic capacitors with reversed polarities exist in all series branches cannot be determined according to the branch voltage, whether the loop current exceeds a current threshold is further judged, if the loop current exceeds the current threshold, the electrolytic capacitors with reversed polarities exist in all series branches can be determined, and if the loop current does not exceed the current threshold, the electrolytic capacitors with reversed polarities do not exist in all series branches can be determined. Therefore, whether the electrolytic capacitors with the reversed polarities exist in part of the series branches or all the series branches can be accurately detected according to the branch currents of all the series branches and the loop current of the loop formed by all the series branches, and the accuracy of detecting the electrolytic capacitors with the reversed polarities can be improved.
Drawings
Fig. 1 is a flowchart of a method for detecting reverse polarity of a capacitor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a system for detecting reverse polarity of a capacitor according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another exemplary system for detecting reverse polarity of a capacitor according to the present invention;
FIG. 4 is a schematic diagram of a device for detecting reverse polarity of a capacitor according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of another apparatus for detecting reverse polarity of capacitance according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of another apparatus for detecting reverse polarity of capacitance according to an embodiment of the present invention;
fig. 7 is a schematic diagram of another capacitor polarity reversal detection apparatus according to an embodiment of the present invention.
List of reference numerals:
101: determining a voltage threshold and a current threshold according to the output power of the test power supply and the equivalent impedance of each series branch
102: respectively detecting the branch voltage at both ends of each series branch
103: detecting loop current of test power supply output
104: determining whether a branch voltage of at least one of the series branches exceeds a voltage threshold
105: electrolytic capacitor for determining polarity reversal in each series branch
106: judging whether the loop current exceeds the current threshold
107: electrolytic capacitor for determining absence of polarity reversal in each series branch
401: threshold determination module 402: the voltage detection module 403: current detection module
404: voltage comparison module 405: the first result output module 406: current comparison module
407: the second result output module 4011: voltage threshold determination unit 4012: current threshold determination unit
408: the memory 409 is: processor E1: test power supply
K1: switch C11: electrolytic capacitor C1 n: electrolytic capacitor
C21: electrolytic capacitor C2 n: electrolytic capacitor C31: electrolytic capacitor
C3 n: electrolytic capacitor R1: balance resistance R2: balance resistance
R3: balance resistance VM 1: voltage detector VM 2: voltage detector
VM 3: voltage detector AM 1: current detector
Detailed Description
As described above, the dc bus side of the frequency converter is provided with a plurality of series branches connected in series, each series branch includes a plurality of electrolytic capacitors connected in parallel, when it is determined whether there is an electrolytic capacitor with a reversed polarity in each series branch by detecting the branch voltage of each series branch, when there is an electrolytic capacitor with a reversed polarity in each series branch, the divided voltage of each series branch is the same as that of each series branch when there is no electrolytic capacitor with a reversed polarity, and therefore, a correct detection result cannot be obtained when there is an electrolytic capacitor with a reversed polarity in each series branch according to the branch voltage of each series branch, and thus, an electrolytic capacitor with a reversed polarity cannot be accurately detected.
In the embodiment of the invention, when detecting whether the electrolytic capacitors with the reversed polarities exist on the side of the variable frequency bus, the branch voltage of each series branch is detected respectively, the loop current of each series branch is detected, the condition that the electrolytic capacitors with the reversed polarities exist in part of the series branches can be determined according to the branch voltage of each series branch, and the condition that the electrolytic capacitors with the reversed polarities exist in all the series branches can be determined according to the branch voltage and the loop current of each series branch, so that whether the electrolytic capacitors with the reversed polarities exist in part of the series branches or the electrolytic capacitors with the reversed polarities exist in all the series branches can be accurately determined, and the accuracy of detecting whether the electrolytic capacitors with the reversed polarities exist can be improved.
The following describes in detail a method and an apparatus for detecting reverse connection of capacitance polarity according to an embodiment of the present invention with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present invention provides a method for detecting reverse polarity of a capacitor, where the method may include the following steps:
step 101: determining a voltage threshold and a current threshold according to the output power of a test power supply and the equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors connected in parallel, and the at least two series branches are connected in series in sequence and then connected with two poles of the test power supply;
step 102: respectively detecting branch voltage at two ends of each series branch;
step 103: detecting the loop current output by the test power supply;
step 104: judging whether the branch voltage of at least one series branch in each series branch exceeds a voltage threshold, if so, executing a step 105, and if not, executing a step 106;
step 105: determining that electrolytic capacitors with reversed polarities exist in each series branch and finishing the current process;
step 106: judging whether the loop current exceeds a current threshold, if so, executing step 105, and if not, executing step 107;
step 107: and determining that no electrolytic capacitor with reversed polarity exists in each series branch.
In the embodiment of the invention, a voltage threshold and a current threshold are preset according to the output voltage of the test power supply and the balance current of each series branch, and when no electrolytic capacitor with reversed polarity exists in each series branch, the branch voltage of each series branch cannot exceed the set voltage threshold, and the loop current flowing through each series branch cannot exceed the current threshold. When detecting whether electrolytic capacitors with reversed polarities exist, branch voltage of each series branch and loop current output by a test power supply are respectively detected, when the branch voltage of at least one series branch exceeds a voltage threshold, electrolytic capacitors with reversed polarities exist in at least one series branch, when the branch voltage of all series branches does not exceed the voltage threshold, whether electrolytic capacitors with reversed polarities exist in all series branches cannot be determined according to the branch voltage, whether the loop current exceeds a current threshold is further judged, if the loop current exceeds the current threshold, the electrolytic capacitors with reversed polarities exist in all series branches can be determined, and if the loop current does not exceed the current threshold, the electrolytic capacitors with reversed polarities do not exist in all series branches can be determined. Therefore, whether the electrolytic capacitors with the reversed polarities exist in part of the series branches or all the series branches can be accurately detected according to the branch currents of all the series branches and the loop current of the loop formed by all the series branches, and the accuracy of detecting the electrolytic capacitors with the reversed polarities can be improved.
In the embodiment of the invention, for any one series branch, because the reverse leakage current of the electrolytic capacitor is obviously greater than the normal leakage current, when one or more electrolytic capacitors with reversed polarities exist in the series branch, the divided voltage of the series branch is reduced, and the divided voltage is the branch voltage of the series branch, so that whether the electrolytic capacitor with the reversed polarity exists in the series branch can be determined according to whether the branch voltage of the series branch is lower than the voltage threshold.
In the embodiment of the invention, when the electrolytic capacitors with the opposite polarities do not exist in each series branch, each series branch has approximately equal equivalent resistance, and each series branch has approximately similar branch voltage division. Because the reverse leakage current of the electrolytic capacitor is obviously larger than the normal leakage current, when an electrolytic capacitor with reversed polarity exists in one series branch, the equivalent resistance of the series branch can be reduced to a lower level, and the influence of the number of the electrolytic capacitors with reversed polarity in the same series branch on the equivalent resistance of the series branch is smaller, so that when the electrolytic capacitors with reversed polarity exist in each series branch, the equivalent resistance of each series branch is still basically equal, and each series branch still has similar branch voltage division. In summary, when the electrolytic capacitors with reversed polarities exist in all the serial branches, it is impossible to detect whether the electrolytic capacitors with reversed polarities exist in each serial branch according to the branch voltage of each serial branch.
In the embodiment of the invention, since the reverse leakage current of the electrolytic capacitor is significantly larger than the normal leakage current, when an electrolytic capacitor with reversed polarity exists in a series branch, the equivalent resistance of the series branch is reduced to a lower level. If electrolytic capacitors with reversed polarities exist in all the series branches, the equivalent resistance of each series branch is reduced, and on the premise that the test power supply outputs constant voltage, the loop current of a loop formed by the test power supply and each series branch is increased, so that when the branch voltage of each series branch does not exceed the voltage threshold and the loop current exceeds the current threshold, each series branch can be determined to include the electrolytic capacitors with reversed polarities, and the electrolytic capacitors with reversed polarities exist in each series branch can be determined.
Optionally, on the basis of the method for detecting reverse polarity connection of a capacitor shown in fig. 1, when the voltage threshold is determined according to the output voltage of the test power supply and the equivalent impedance voltage threshold of each series branch, the voltage threshold may be determined according to the output voltage of the test power supply and the equivalent impedance of each series branch, specifically, the output voltage of the test power supply and the equivalent impedance of each series branch are substituted into the following first formula, and the voltage threshold is calculated by the following first formula. The first formula includes:
Figure BDA0002348884560000081
wherein, VtThe voltage threshold value is used for representing a voltage threshold value, V is used for representing the output voltage of a test power supply, n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, k1For characterizing the voltage correction factor determined from the voltage acquisition error.
In the embodiment of the invention, because the output voltage of the test power supply is kept unchanged, when the branch voltage of part of the series branches is reduced, the branch voltage of other parts of the series branches is increased, an interval range is determined as a voltage threshold according to the output voltage of the test power supply and the equivalent resistance of each series branch, and when the branch voltage of one series branch is larger than the upper limit of the interval range or smaller than the reduction of the interval range, the electrolytic capacitors with reversed polarities exist in each series branch, so that the electrolytic capacitors with reversed polarities can be detected conveniently.
In the embodiment of the invention, because voltage detection errors can exist when the branch voltage of each series branch and the output voltage of the test power supply are detected, in order to avoid misjudgment caused by the voltage detection errors, a voltage threshold with a larger range is obtained by setting a voltage correction coefficient, so that the probability of error occurrence of a detection result caused by the voltage detection errors is reduced.
When n is equal to 20, the number of bits in the bit line is,
Figure BDA0002348884560000091
considering the detection error possibly occurring when the output voltage of the test power supply is detected and the detection error possibly occurring when the branch voltage of each series branch is detected, the voltage correction coefficient k is used1Correcting the finally obtained voltage threshold Vt∈(-3％V，3％V)。
Optionally, on the basis of the method for detecting reverse polarity connection of a capacitor shown in fig. 1, when the current threshold is determined according to the output voltage of the test power supply and the equivalent impedance of each series branch, the current threshold may be determined according to the output voltage of the test power supply and the equivalent impedance of each series branch, and specifically, the output voltage of the test power supply and the equivalent impedance of each series branch may be substituted into the following second formula, and the current threshold may be calculated by the following second formula. The second formula is:
Figure BDA0002348884560000092
wherein, ItThe voltage detection circuit is used for representing a current threshold value, n is used for representing the ratio of equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, V is used for representing the output voltage of a test power supply, R is used for representing the sum of the equivalent impedance of each series branch, and k is2For characterizing the current correction factor determined from the current acquisition error.
In the embodiment of the invention, because the reverse leakage current of the electrolytic capacitor is obviously greater than the normal leakage current, when the electrolytic capacitors with reversed polarities exist in each series branch, the total equivalent impedance of each series branch is reduced, and the loop current of the loop formed by each series branch connected with the test power supply is increased, so that the current threshold value can be calculated according to the output voltage of the test power supply and the equivalent impedance of each series branch, and when the loop current is detected to be less than the current threshold value, the electrolytic capacitors with reversed polarities exist in each series branch can be determined.
In the embodiment of the invention, because a current detection error may exist when the loop current is detected, in order to avoid the misjudgment of polarity reversal of the electrolytic capacitor caused by the current detection error, a voltage correction coefficient is set for correction to obtain a larger current threshold value, so that the probability of error occurrence of the polarity reversal detection result caused by the current detection error is reduced.
When n is equal to 20, the number of bits in the bit line is,
Figure BDA0002348884560000101
the error possibly existing when the loop current is collected is considered, and the coefficient k is corrected through the current2Making a correction to make the current threshold value
Figure BDA0002348884560000102
Wherein, R is used for representing the equivalent impedance of each series branch, and the equivalent impedance specifically refers to the sum of the equivalent resistances of each series branch.
Alternatively, on the basis of the method for detecting polarity reversal of capacitance shown in fig. 1, if step 104 and step 105 determine that there is an electrolytic capacitor with polarity reversal in each series branch according to the branch voltage of each series branch, it may be further determined whether there is an electrolytic capacitor with polarity reversal in each series branch according to the branch voltage of each series branch. Specifically, whether the electrolysis electricity with reversed polarity exists in one series branch can be determined by the following method:
for each series branch, determining that at least one electrolytic capacitor with reversed polarity exists in the series branch if the branch voltage of the series branch is smaller than the lower limit of the voltage threshold.
In the embodiment of the present invention, since the electrolytic capacitor with the reversed polarity may cause the equivalent resistance of the serial branch where the electrolytic capacitor is located to decrease, and the equivalent resistance may cause the branch voltage of the corresponding serial branch to decrease, after determining that the electrolytic capacitor with the reversed polarity exists in at least one serial branch according to the branch voltage of each serial branch, it may be respectively determined whether the branch voltage of each serial branch is smaller than the lower limit of the voltage threshold, and if the branch voltage of one serial branch is smaller than the lower limit of the voltage threshold, it may be determined that the electrolytic capacitor with the reversed polarity exists in the serial branch. Accordingly, if the branch voltage of one series branch is greater than the upper limit of the voltage threshold, it may be determined that there is no electrolytic capacitor with reversed polarity in the series branch.
In the embodiment of the invention, after determining that the electrolytic capacitors with the reversed polarities exist in part of the series branches, whether the branch voltage of each series branch is smaller than the lower limit of the voltage threshold value can be respectively determined, and then the series branches including the electrolytic capacitors with the reversed polarities are determined, so that the positioning of the electrolytic capacitors with the reversed polarities is realized, a user can more conveniently find the electrolytic capacitors with the reversed polarities, and the electrolytic capacitors with the reversed polarities are further processed.
Alternatively, on the basis of the method for detecting polarity reversal of capacitance shown in fig. 1, if steps 106 and 105 determine that there is an electrolytic capacitance with polarity reversal in each series branch according to the loop current, it may be further determined that there is an electrolytic capacitance with polarity reversal in each series branch.
In the embodiment of the invention, whether the electrolytic capacitors with the reversed polarities exist in each series branch is determined according to the branch voltage of each series branch, after whether the electrolytic capacitors with the reversed polarities exist in each series branch cannot be determined according to the branch voltage of each series branch, whether the electrolytic capacitors with the reversed polarities exist in each series branch is determined according to the loop current, and if the electrolytic capacitors with the reversed polarities exist in each series branch is determined according to the loop current, only the situation that the electrolytic capacitors with the reversed polarities exist in all series branches is included.
In the embodiment of the invention, after the electrolytic capacitors with the reversed polarities exist in each series branch are determined according to the loop current, the electrolytic capacitors with the reversed polarities exist in each series branch can be further determined, the polarity of the electrolytic capacitors with the reversed polarities is positioned in the frequency converter, and then a user can more conveniently find the electrolytic capacitors with the reversed polarities and carry out repair treatment on the electrolytic capacitors with the reversed polarities.
Optionally, on the basis of the method for detecting reverse polarity connection of capacitors shown in fig. 1, for each series branch, the series branch includes at least two electrolytic capacitors and at least one balance resistor connected in parallel with each other. Because different electrolytic capacitors may have performance difference, namely different electrolytic capacitors may have different equivalent resistances, different series branches can have the same equivalent impedance by connecting the balance resistors in parallel in each series branch, so that the partial pressure of each series branch is balanced, the condition that each series branch causes electrolytic capacitor damage due to unbalanced partial pressure is avoided, and the safety of the frequency converter is ensured.
Optionally, on the basis of the method for detecting polarity reversal of capacitors provided in the foregoing embodiments, the number of series branches connected to the dc bus side of the frequency converter is different according to the voltage of the system in which the frequency converter is located, for example, two series branches are generally connected in series in a 400V system, and three series branches are generally connected in series in a 690V system.
In the 400V system shown in fig. 2, electrolytic capacitors C11 to C1n and a balancing resistor R1 are connected in parallel to form a first series branch, electrolytic capacitors C21 to C2n and a balancing resistor R2 are connected in parallel to form a second series branch, the first series branch and the second series branch are connected in series to be connected to two poles of a test power supply E1, a voltage detector VM1 is configured to detect a branch voltage of the first series branch, a voltage detector VM2 is configured to detect a branch voltage of the second series branch, and a current detector AM1 is configured to detect a loop current output by the test power supply E1. After closing the switch K1, the branch voltage detected by the voltage detector VM1 and the voltage detector VM2 is obtained, and the loop current detected by the current detector AM1 is obtained, and according to the difference between the detected branch voltage and loop current, there are four cases as follows:
A. if the branch voltage detected by voltage detector VM1 is less than the lower limit of the voltage threshold and the branch voltage detected by voltage detector VM2 is greater than the upper limit of the voltage threshold, it is determined that there is at least one electrolytic capacitor with reversed polarity in the first series branch and no electrolytic capacitor with reversed polarity in the second series branch.
B. If the branch voltage detected by voltage detector VM1 is greater than the upper limit of the voltage threshold and the branch voltage detected by voltage detector VM2 is less than the lower limit of the voltage threshold, it is determined that there is no electrolytic capacitor with reversed polarity in the first series branch and at least one electrolytic capacitor with reversed polarity in the second series branch.
C. If neither the branch voltage detected by the voltage detector VM1 nor the branch voltage detected by the voltage detector VM2 exceeds the voltage threshold, i.e., both are greater than or equal to the lower limit of the voltage threshold and less than or equal to the upper limit of the voltage threshold, and the loop current detected by the current detector AM1 is greater than the current threshold, it is determined that at least one electrolytic capacitor with reversed polarity is present in each of the first and second series branches.
D. If neither the branch voltage detected by the voltage detector VM1 nor the branch voltage detected by the voltage detector VM2 exceeds the voltage threshold, i.e., both are greater than or equal to the lower limit of the voltage threshold and less than or equal to the upper limit of the voltage threshold, and the return current detected by the current detector AM1 is less than or equal to the current threshold, it is determined that there is no electrolytic capacitor with reverse polarity in both the first and second series branches.
In the 690V system shown in fig. 3, electrolytic capacitors C11 to C1n and a balancing resistor R1 are connected in parallel to form a first series branch, electrolytic capacitors C21 to C2n and a balancing resistor R2 are connected in parallel to form a second series branch, electrolytic capacitors C31 to C3n and a balancing resistor R3 are connected in parallel to form a third series branch, the first series branch, the second series branch and the third series branch are connected in series to be connected to two poles of a test power supply E1, a voltage detector VM1 is used for detecting a branch voltage of the first series branch, a voltage detector VM2 is used for detecting a branch voltage of the second series branch, a voltage detector VM3 is used for detecting a branch voltage of the third series branch, and a current detector AM1 is used for detecting a loop current output by the test power supply E1. After the switch K1 is closed, the branch voltage detected by the voltage detector VM1, the voltage detector VM2 and the voltage detector VM3 is obtained, and the loop current detected by the current detector AM1 is obtained, and according to the difference between the detected branch voltage and the detected loop current, there are the following three cases:
A. if the branch voltage detected by any one of the voltage detector VM1, the voltage detector VM2 and the voltage detector VM3 is less than the lower limit of the voltage threshold, and the branch voltages detected by the other two voltage detectors are greater than the upper limit of the voltage threshold, it is determined that at least one electrolytic capacitor with reversed polarity exists in the series branch whose branch voltage is less than the lower limit of the voltage threshold, and no electrolytic capacitor with reversed polarity exists in the series branch whose branch voltage is greater than the upper limit of the voltage threshold.
B. If any two of the voltage detectors VM1, VM2, and VM3 detect a branch voltage smaller than the lower limit of the voltage threshold and the remaining one detects a branch voltage larger than the upper limit of the voltage threshold, it is determined that at least one electrolytic capacitor with reversed polarity exists in each of the two series branches whose branch voltages are smaller than the lower limit of the voltage threshold, and that no electrolytic capacitor with reversed polarity exists in the other series branch whose branch voltage is larger than the upper limit of the voltage threshold.
C. If none of the branch voltages detected by the voltage detector VM1, the voltage detector VM2, and the voltage detector VM3 exceeds the voltage threshold, that is, the branch voltages detected by the three voltage detectors are all greater than or equal to the lower limit of the voltage threshold and less than or equal to the upper limit of the voltage threshold, and the loop current detected by the current detector AM1 is greater than the current threshold, it is determined that at least one electrolytic capacitor with reverse polarity exists in each of the first series branch, the second series branch, and the third series branch.
D. If the branch voltages detected by the voltage detector VM1, the voltage detector VM2 and the voltage detector VM3 do not exceed the voltage threshold, that is, the branch voltages detected by the three voltage detectors are all greater than or equal to the lower limit of the voltage threshold and less than or equal to the upper limit of the voltage threshold, and the backflow current detected by the current detector AM1 is less than or equal to the current threshold, it is determined that no electrolytic capacitor with reverse polarity exists in the first series branch, the second series branch and the third series branch.
It should be noted that when the output voltage of the test power supply is small, the measurement resolution of the branch voltage and the loop current is low, and the branch voltage of each series branch changes slowly, so that the situation of polarity reversal of the electrolytic capacitor cannot be detected, and when the output voltage of the test power supply is large, the frequency converter to be tested may malfunction and be damaged. The test power supply with 200V output voltage can be selected to perform the detection of the reverse polarity of the capacitor.
The capacitance polarity reversal detection method provided by the above embodiments is verified by using specific examples. The direct current bus side of one frequency converter is connected with three series branches, each series branch comprises 8 electrolytic capacitors and a balance resistor which are mutually connected in parallel, the equivalent impedance of each series branch is 3.3k omega, and the polarity reversal detection result of the electrolytic capacitors connected to the direct current bus side of the frequency converter is shown in the following table 1.
TABLE 1
Figure BDA0002348884560000131
In table 1, the reverse connection of a series branch means that there are electrolytic capacitors with reverse polarity in one series branch, the reverse connection of two series branches means that there are electrolytic capacitors with reverse polarity in two series branches, and the reverse connection of three series branches means that there are electrolytic capacitors with reverse polarity in three series branches. The voltage difference of the series branch is (normal series branch voltage-detected series branch voltage)/normal series branch voltage, wherein the normal series branch voltage is the voltage difference of the series branch when the corresponding series branch is reversely connected without the electrolytic capacitor, and the detected series branch voltage is the voltage difference of the corresponding series branch detected by the voltage detector.
As shown in fig. 4, an embodiment of the present invention provides a device for detecting reverse polarity of a capacitor, including:
a threshold determining module 401, configured to determine a voltage threshold and a current threshold according to an output voltage of the test power supply and an equivalent impedance of each series branch, where each series branch includes at least two electrolytic capacitors connected in parallel, and the at least two series branches are connected in series in sequence and then connected to two poles of the test power supply;
a voltage detection module 402, configured to detect a branch voltage at each end of each series branch;
a current detection module 403, configured to detect a loop current output by the test power supply;
a voltage comparison module 404, configured to determine whether a branch voltage of at least one of the at least two serial branches exceeds a voltage threshold according to the voltage threshold determined by the threshold determination module 401 and the branch voltage detected by the voltage detection module 402;
a first result output module 405, configured to determine that electrolytic capacitors with reversed polarities exist in the at least two serial branches when the voltage comparison module 404 determines that the branch voltage of at least one of the at least two serial branches exceeds the voltage threshold;
a current comparison module 406, configured to determine whether the loop current detected by the current detection module 403 exceeds the current threshold determined by the threshold determination module 401 after the voltage comparison module 404 determines that the branch voltage of any serial branch does not exceed the voltage threshold;
a second result output module 407, configured to determine that there is an electrolytic capacitor with reversed polarity in at least two serial branches when the current comparison module 406 determines that the loop current exceeds the current threshold, and determine that there is no electrolytic capacitor with reversed polarity in at least two serial branches when the current comparison module 406 determines that the loop current does not exceed the current threshold.
In an embodiment of the present invention, the voltage detection module 402 may be configured to perform step 101 in the above-mentioned method embodiment, the current detection module 403 may be configured to perform step 103 in the above-mentioned method embodiment, the voltage comparison module 404 may be configured to perform step 104 in the above-mentioned method embodiment, the first result output module 405 may be configured to perform step 105 in the above-mentioned method embodiment, the current comparison module 406 may be configured to perform step 106 in the above-mentioned method embodiment, and the second result output module 407 may be configured to perform step 107 in the above-mentioned method embodiment.
Alternatively, on the basis of the capacitance polarity reversal detection apparatus shown in fig. 4, as shown in fig. 5, the threshold determination module 401 includes: a voltage threshold determination unit 4011;
the voltage threshold determination unit 4011 is configured to calculate a voltage threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch by using the following first formula;
the first formula includes:
Figure BDA0002348884560000141
wherein, VtThe voltage threshold value is represented, V is used for representing the output voltage of the test power supply, n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistor, the balance resistor is the resistor connected in parallel with each electrolytic capacitor in the series branch, k1For characterizing the voltage correction factor determined from the voltage acquisition error.
Alternatively, on the basis of the capacitance polarity reversal detection apparatus shown in fig. 4, as shown in fig. 6, the threshold determination module 401 includes: a current threshold determination unit 4012;
the current threshold determining unit 4012 is configured to calculate a current threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch by using a second formula as follows;
the second formula includes:
Figure BDA0002348884560000142
wherein, ItThe method is used for representing a current threshold value, n is used for representing the ratio of equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, V is used for representing the output voltage of a test power supply, R is used for representing the sum of the equivalent impedance of each series branch, and k is used for representing the sum of the equivalent impedance of each series branch2For characterizing the current correction factor determined from the current acquisition error.
Optionally, on the basis of the apparatus for detecting polarity reversal of capacitance shown in fig. 4, the first result output module 405 is further configured to determine that at least one electrolytic capacitor with polarity reversal exists in a series branch when the voltage comparison module 404 determines that a branch voltage of the series branch is smaller than a lower limit of the voltage threshold.
Optionally, on the basis of the detection apparatus for detecting polarity reversal of a capacitor shown in fig. 4, the second result output module 407 is further configured to determine that an electrolytic capacitor with polarity reversal exists in each series branch when the current comparison module 406 determines that the loop current exceeds the current threshold.
It should be noted that the capacitance polarity reversal detection device provided in each of the above embodiments and the capacitance polarity reversal detection method are based on the same concept, and the interaction between the modules in the capacitance polarity reversal detection device can be referred to the description in the foregoing capacitance polarity reversal detection method embodiment, and is not described herein again.
As shown in fig. 7, an embodiment of the present invention provides a device for detecting reverse polarity of a capacitor, including: at least one memory 408 and at least one processor 409;
the at least one memory 408 for storing a machine-readable program;
the at least one processor 409 is configured to invoke the machine readable program to execute the method for detecting reverse polarity of capacitance provided in the above embodiments.
The present invention also provides a computer readable medium storing instructions for causing a computer to perform a method of capacitance polarity reversal detection as described herein. Specifically, a system or an apparatus equipped with a storage medium on which software program codes that realize the functions of any of the above-described embodiments are stored may be provided, and a computer (or a CPU or MPU) of the system or the apparatus is caused to read out and execute the program codes stored in the storage medium.
In this case, the program code itself read from the storage medium can realize the functions of any of the above-described embodiments, and thus the program code and the storage medium storing the program code constitute a part of the present invention.
Examples of the storage medium for supplying the program code include a floppy disk, a hard disk, a magneto-optical disk, an optical disk (e.g., CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW), a magnetic tape, a nonvolatile memory card, and a ROM. Alternatively, the program code may be downloaded from a server computer via a communications network.
Further, it should be clear that the functions of any one of the above-described embodiments may be implemented not only by executing the program code read out by the computer, but also by causing an operating system or the like operating on the computer to perform a part or all of the actual operations based on instructions of the program code.
Further, it is to be understood that the program code read out from the storage medium is written to a memory provided in an expansion board inserted into the computer or to a memory provided in an expansion unit connected to the computer, and then causes a CPU or the like mounted on the expansion board or the expansion unit to perform part or all of the actual operations based on instructions of the program code, thereby realizing the functions of any of the above-described embodiments.
It should be noted that not all steps and modules in the above flows and system structure diagrams are necessary, and some steps or modules may be omitted according to actual needs. The execution order of the steps is not fixed and can be adjusted as required. The system structure described in the above embodiments may be a physical structure or a logical structure, that is, some modules may be implemented by the same physical entity, or some modules may be implemented by a plurality of physical entities, or some components in a plurality of independent devices may be implemented together.
In the above embodiments, the hardware unit may be implemented mechanically or electrically. For example, a hardware element may comprise permanently dedicated circuitry or logic (such as a dedicated processor, FPGA or ASIC) to perform the corresponding operations. The hardware elements may also comprise programmable logic or circuitry, such as a general purpose processor or other programmable processor, that may be temporarily configured by software to perform the corresponding operations. The specific implementation (mechanical, or dedicated permanent, or temporarily set) may be determined based on cost and time considerations.
While the invention has been shown and described in detail in the drawings and in the preferred embodiments, it is not intended to limit the invention to the embodiments disclosed, and it will be apparent to those skilled in the art that various combinations of the code auditing means in the various embodiments described above may be used to obtain further embodiments of the invention, which are also within the scope of the invention.

Claims (13)

1. The method for detecting the polarity reversal of the capacitor is characterized by comprising the following steps:
determining a voltage threshold and a current threshold according to the output voltage of a test power supply and the equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors connected in parallel, and at least two series branches are connected in series in sequence and then connected with two poles of the test power supply (101);
respectively detecting branch voltage (102) at two ends of each series branch;
detecting a loop current (103) output by the test power supply;
determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold (104);
determining that there is the electrolytic capacitor (105) in the at least two series branches with reversed polarity if the branch voltage of at least one of the series branches in the at least two series branches exceeds the voltage threshold;
determining whether the loop current exceeds the current threshold if the branch voltage of none of the at least two series branches exceeds the voltage threshold (106);
determining that there is the electrolytic capacitor (105) in the at least two series branches with reversed polarity if the loop current exceeds the current threshold;
determining that the electrolytic capacitors (107) of reversed polarity are not present in the at least two series branches if the loop current does not exceed the current threshold.
2. The method of claim 1, wherein determining the voltage threshold based on the output voltage of the test power supply and the equivalent impedance of each series branch comprises:
calculating the voltage threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch by a first formula;
the first formula includes:
Figure FDA0002348884550000011
wherein, the VtThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k is used for representing the voltage threshold, V is used for representing the output voltage of the test power supply, and n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the1For characterizing the voltage correction factor determined from the voltage acquisition error.
3. The method of claim 1, wherein determining the current threshold based on the output voltage of the test power supply and the equivalent impedance of each series branch comprises:
calculating the current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch circuit by using a second formula;
the second formula includes:
Figure FDA0002348884550000021
wherein, the ItThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, the V is used for representing the output voltage of the test power supply, the R is used for representing the sum of the equivalent impedances of each series branch, and the k is used for representing the sum of the equivalent impedances of each series branch2For characterizing the current correction factor determined from the current acquisition error.
4. The method of claim 1, further comprising, after said determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold:
for each of the series branches, if the branch voltage of the series branch is less than the lower limit of the voltage threshold, determining that at least one electrolytic capacitor with reversed polarity exists in the series branch.
5. The method of claim 1, after said determining whether the loop current exceeds the current threshold, further comprising:
and if the loop current exceeds the current threshold, determining that the electrolytic capacitors with reversed polarities exist in each series branch.
6. The method according to any one of claims 1 to 5,
for each of the series branches, the series branch comprises at least two of the electrolytic capacitors and at least one balancing resistor connected in parallel with each other, so that different series branches have the same equivalent impedance.
7. Capacitance polarity reversal detection device, its characterized in that includes:
the threshold value determining module (401) is used for determining a voltage threshold value and a current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors which are mutually connected in parallel, and at least two series branches are connected in series in sequence and then are connected with two poles of the test power supply;
a voltage detection module (402) for detecting a branch voltage across each of said series branches, respectively;
a current sensing module (403) for sensing a loop current output by said test power supply;
a voltage comparison module (404) for determining whether the branch voltage of at least one of the at least two serial branches exceeds the voltage threshold according to the voltage threshold determined by the threshold determination module (401) and the branch voltage detected by the voltage detection module (402);
a first result output module (405) for determining that the electrolytic capacitors with reversed polarity exist in the at least two series branches when the voltage comparison module (404) determines that the branch voltage of at least one of the series branches in the at least two series branches exceeds the voltage threshold;
a current comparison module (406) for determining whether the loop current detected by the current detection module (403) exceeds the current threshold determined by the threshold determination module (401) after the voltage comparison module (404) determines that the branch voltage of none of the at least two series branches exceeds the voltage threshold;
a second result output module (407) for determining that there is the electrolytic capacitor with reversed polarity in the at least two series branches when the current comparison module (406) determines that the loop current exceeds the current threshold, and determining that there is no electrolytic capacitor with reversed polarity in the at least two series branches when the current comparison module (406) determines that the loop current does not exceed the current threshold.
8. The apparatus of claim 7, wherein the threshold determination module (401) comprises: a voltage threshold determination unit (4011);
the voltage threshold determining unit (4011) is configured to calculate the voltage threshold according to an output voltage of the test power supply and an equivalent impedance of each of the series branches by a first formula;
the first formula includes:
Figure FDA0002348884550000031
wherein, the VtThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k is used for representing the voltage threshold, V is used for representing the output voltage of the test power supply, and n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to the balance resistance, the balance resistance is the resistance connected in parallel with each electrolytic capacitor in the1For characterizing the voltage correction factor determined from the voltage acquisition error.
9. The apparatus of claim 7, wherein the threshold determination module (401) comprises: a current threshold determination unit (4012);
the current threshold value determining unit (4012) is configured to calculate the current threshold value according to the output voltage of the test power supply and the equivalent impedance of each of the series branches by using a second formula as follows;
the second formula includes:
Figure FDA0002348884550000032
wherein, the ItThe n is used for representing the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one series branch to a balance resistor, the balance resistor is a resistor connected in parallel with each electrolytic capacitor in the series branch, the V is used for representing the output voltage of the test power supply, the R is used for representing the sum of the equivalent impedances of each series branch, and the k is used for representing the sum of the equivalent impedances of each series branch2For characterizing the current correction factor determined from the current acquisition error.
10. The apparatus of claim 7,
the first result output module (405) is further configured to determine that at least one electrolytic capacitor with reversed polarity exists in one of the series branches when the voltage comparison module (404) determines that the branch voltage of the one series branch is smaller than the lower limit of the voltage threshold.
11. The apparatus of claim 7,
the second result output module (407) is further configured to determine that the electrolytic capacitors with reversed polarities exist in each of the series branches when the current comparison module (406) determines that the loop current exceeds the current threshold.
12. Capacitance polarity reversal detection device, its characterized in that includes: at least one memory (408) and at least one processor (409);
the at least one memory (408) for storing a machine readable program;
the at least one processor (409) configured to invoke the machine readable program to perform the method of any of claims 1 to 6.
13. Computer readable medium, characterized in that it has stored thereon computer instructions which, when executed by a processor, cause the processor to carry out the method of any one of claims 1 to 6.
CN201911406864.2A 2019-12-31 2019-12-31 Capacitance polarity reversal detection method, device and computer readable medium Pending CN110988577A (en)

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