Capacitor polarity reverse detection method, device and computer readable medium

Abstract

The present invention provides a capacitor polarity reverse detection method, device and computer readable medium, the capacitor polarity reverse detection method comprises: according to the output voltage of the test power supply and the equivalent impedance of each series branch, determine the voltage threshold and the current threshold; respectively detect the branch voltage at both ends of each series branch; detect the loop current output by the test power supply; if at least one of the at least two series branches has a branch voltage exceeding the voltage threshold, it is determined that there is an electrolytic capacitor with reverse polarity in the at least two series branches; if no branch voltage of any series branch in the at least two series branches exceeds the voltage threshold, and the loop current exceeds the current threshold, it is determined that there is an electrolytic capacitor with reverse polarity in the at least two series branches; if the loop current does not exceed the current threshold, it is determined that there is no electrolytic capacitor with reverse polarity in the at least two series branches. This scheme can accurately detect the electrolytic capacitor with reverse polarity.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering technology, and in particular to a capacitor polarity reverse connection detection method, device and computer-readable medium. Background Art

[0002] Inverters are widely used in the field of motor control. In order to enable the inverter to output stable DC power, electrolytic capacitors are installed on the DC bus side of the inverter. The connection relationship between the electrolytic capacitors and the DC bus of the inverter is as follows: multiple electrolytic capacitors are connected in parallel to form a series branch, and multiple series branches are connected in series to the DC bus of the inverter to form a loop.

[0003] In order to ensure that the inverter can be used normally after leaving the factory, various functions and hardware structures of the inverter need to be tested before leaving the factory. This includes detecting whether there is an electrolytic capacitor with reverse polarity on the DC bus side of the inverter. This is because the 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, it may affect the voltage balance of each series branch, and in severe cases may cause damage to the electrolytic capacitor.

[0004] Currently, when detecting whether the polarity of the electrolytic capacitor on the DC bus side of the inverter is reversed, the voltage of each series branch is detected respectively. When the voltage of a series branch exceeds a set voltage threshold, it is determined that there is an electrolytic capacitor with reverse polarity in the series branch.

[0005] With regard to the current method for detecting reverse polarity of capacitors, when there are no reverse polarity electrolytic capacitors in each series branch connected in series on the DC bus side of the inverter, each series branch has similar voltage division capabilities, and each series branch evenly divides the input voltage applied to the DC bus. When there are reverse polarity electrolytic capacitors in each series branch, each series branch still has similar voltage division capabilities, and each series branch still evenly divides the input voltage applied to the DC bus. That is, when there are reverse polarity electrolytic capacitors in each series branch and when there are no reverse polarity electrolytic capacitors in each series branch, the voltages of each series branch are the same. Therefore, missed connections may occur, resulting in the inability to accurately detect reverse polarity electrolytic capacitors. Summary of the invention

[0006] In view of this, the capacitor polarity reverse connection detection method, device and computer-readable medium provided by the present invention can accurately detect an electrolytic capacitor with reverse polarity connection.

[0007] In a first aspect, an embodiment of the present invention provides a method for detecting reverse polarity of a capacitor, comprising:

[0008] Determine 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, wherein each series branch includes at least two electrolytic capacitors connected in parallel with each other, and at least two of the series branches are connected in series in sequence and connected to two poles of the test power supply;

[0009] Respectively detecting the branch voltages at both ends of each of the series branches;

[0010] Detecting a loop current output by the test power supply;

[0011] Determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold;

[0012] If the branch voltage of at least one of the at least two series branches exceeds the voltage threshold, it is determined that the electrolytic capacitor with reverse polarity exists in the at least two series branches;

[0013] If the branch voltage of any of the at least two series branches does not exceed the voltage threshold, determining whether the loop current exceeds the current threshold;

[0014] If the loop current exceeds the current threshold, determining that there is an electrolytic capacitor with reverse polarity in the at least two series branches;

[0015] If the loop current does not exceed the current threshold, it is determined that the electrolytic capacitor with reverse polarity does not exist in the at least two series branches.

[0016] Optionally,

[0017] The step of determining the voltage threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch includes:

[0018] Calculating the voltage threshold by the following first formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches;

[0019] The first formula includes:

[0020]

[0021] Among them, the V t is used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k 1 Used to characterize the voltage correction factor determined based on the voltage acquisition error.

[0022] Optionally,

[0023] The step of determining the current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch includes:

[0024] 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 the following second formula;

[0025] The second formula includes:

[0026]

[0027] Among them, the I t is used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistor, the balancing resistor is the resistor connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each of the series branches, and k 2 Used to characterize the current correction factor determined based on the current acquisition error.

[0028] Optionally,

[0029] After determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold, the method further includes:

[0030] For each of the series branches, if the branch voltage of the series branch is less than a lower limit of the voltage threshold, it is determined that at least one electrolytic capacitor with reverse polarity exists in the series branch.

[0031] Optionally,

[0032] After determining whether the loop current exceeds the current threshold, the method further includes:

[0033] If the loop current exceeds the current threshold, it is determined that the electrolytic capacitor with reverse polarity exists in each of the series branches.

[0034] Optionally,

[0035] For each of the series branches, the series branch includes at least two electrolytic capacitors and at least one balancing resistor connected in parallel with each other, so that different series branches have the same equivalent impedance.

[0036] In a second aspect, an embodiment of the present invention further provides a capacitor polarity reverse connection detection device, comprising:

[0037] A threshold determination module, used to determine the voltage threshold and the current threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch, wherein each series branch includes at least two electrolytic capacitors connected in parallel with each other, and at least two of the series branches are connected in series in sequence and connected to the two poles of the test power supply;

[0038] A voltage detection module, used to detect the branch voltage at both ends of each of the series branches;

[0039] A current detection module, used to detect the loop current output by the test power supply;

[0040] a voltage comparison module, configured to determine whether the branch voltage of at least one of the at least two series 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;

[0041] a first result output module, configured to determine that there is an electrolytic capacitor with reverse polarity in the at least two series branches when the voltage comparison module determines that the branch voltage of at least one of the at least two series branches exceeds the voltage threshold;

[0042] 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 none of the at least two series branches has a branch voltage exceeding the voltage threshold;

[0043] A second result output module is used to determine that the electrolytic capacitor with reverse polarity exists in the at least two series branches when the current comparison module determines that the loop current exceeds the current threshold, and to determine that the electrolytic capacitor with reverse polarity does not exist in the at least two series branches when the current comparison module determines that the loop current does not exceed the current threshold.

[0044] Optionally,

[0045] The threshold determination module includes: a voltage threshold determination unit;

[0046] The voltage threshold determination unit is used to calculate the voltage threshold by the following first formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches;

[0047] The first formula includes:

[0048]

[0049] Among them, the Vt is used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k 1 Used to characterize the voltage correction factor determined based on the voltage acquisition error.

[0050] Optionally,

[0051] The threshold determination module includes: a current threshold determination unit;

[0052] The current threshold determination unit is used to calculate the current threshold by the following second formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches;

[0053] The second formula includes:

[0054]

[0055] Among them, the I t is used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistor, the balancing resistor is the resistor connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each of the series branches, and k 2 Used to characterize the current correction factor determined based on the current acquisition error.

[0056] Optionally,

[0057] The first result output module is further used to determine that there is at least one electrolytic capacitor with reverse polarity in the series branch when the voltage comparison module determines that the branch voltage of one of the series branches is less than the lower limit of the voltage threshold.

[0058] Optionally,

[0059] The second result output module is further used to determine that the electrolytic capacitor with reverse polarity exists in each of the series branches when the current comparison module determines that the loop current exceeds the current threshold.

[0060] In a third aspect, an embodiment of the present invention further provides another capacitor polarity reverse detection device, comprising: at least one memory and at least one processor;

[0061] The at least one memory is used to store a machine-readable program;

[0062] The at least one processor is used to call the machine-readable program to execute the method provided by the first aspect and any possible implementation manner of the first aspect.

[0063] In a fourth aspect, an embodiment of the present invention further provides a computer-readable medium having computer instructions stored thereon, and when the computer instructions are executed by a processor, the processor executes any one of the capacitor polarity reverse detection methods provided in the first aspect above.

[0064] It can be seen from the above technical scheme that a voltage threshold and a current threshold are set in advance according to the output voltage of the test power supply and the balanced current of each series branch. When there is no reverse polarity electrolytic capacitor in each series branch, the branch voltage of each series branch will not exceed the set voltage threshold, and the loop current flowing through each series branch will not exceed the current threshold. When detecting whether there is a reverse polarity electrolytic capacitor, the branch voltage of each series branch and the loop current output by the test power supply are detected respectively. When there is a branch voltage of at least one series branch exceeding the voltage threshold, it can be determined that there is a reverse polarity electrolytic capacitor in at least one series branch. When the branch voltage of all series branches does not exceed the voltage threshold, it is impossible to determine whether there is a reverse polarity electrolytic capacitor according to the branch voltage, and then judge whether the loop current exceeds the current threshold. If the loop current exceeds the current threshold, it can be determined that there is a reverse polarity electrolytic capacitor in each series branch. If the loop current does not exceed the current threshold, it can be determined that there is no reverse polarity electrolytic capacitor in each series branch. It can be seen from this that by detecting the electrolytic capacitor with reverse polarity based on the branch current of each series branch and the loop current of the loop formed by each series branch, no matter whether there are electrolytic capacitors with reverse polarity in some of the series branches or there are electrolytic capacitors with reverse polarity in all the series branches, it is possible to accurately detect whether there are electrolytic capacitors with reverse polarity, thereby improving the accuracy of detecting the electrolytic capacitors with reverse polarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a flow chart of a capacitor polarity reverse detection method provided by an embodiment of the present invention;

[0066] Figure 2 is a schematic diagram of a capacitor polarity reverse detection system provided by an embodiment of the present invention;

[0067] Figure 3 is a schematic diagram of another capacitor polarity reverse detection system provided by an embodiment of the present invention;

[0068] Figure 4 is a schematic diagram of a capacitor polarity reverse connection detection device provided by an embodiment of the present invention;

[0069] Figure 5 is a schematic diagram of another capacitor polarity reverse connection detection device provided by an embodiment of the present invention;

[0070] Figure 6 is a schematic diagram of another capacitor polarity reverse connection detection device provided by an embodiment of the present invention;

[0071] Figure 7 It is a schematic diagram of another capacitor polarity reverse detection device provided by an embodiment of the present invention.

[0072] List of reference numerals:

[0073] 101: Determine the voltage threshold and current threshold based on the output power of the test power supply and the equivalent impedance of each series branch

[0074] 102: Detect the branch voltage at both ends of each series branch respectively

[0075] 103: Detect the loop current of the test power supply output

[0076] 104: Determine whether there is at least one branch voltage in the series connection that exceeds a voltage threshold.

[0077] 105: Determine whether there are electrolytic capacitors with reverse polarity in each series branch

[0078] 106: Determine whether the loop current exceeds the current threshold

[0079] 107: Make sure there are no reverse polarity electrolytic capacitors in each series branch

[0080] 401: Threshold determination module 402: Voltage detection module 403: Current detection module

[0081] 404: voltage comparison module 405: first result output module 406: current comparison module

[0082] 407: Second result output module 4011: Voltage threshold determination unit 4012: Current threshold determination unit

[0083] 408: Memory 409: Processor E1: Test power supply

[0084] K1: switch C11: electrolytic capacitor C1n: electrolytic capacitor

[0085] C21: electrolytic capacitor C2n: electrolytic capacitor C31: electrolytic capacitor

[0086] C3n: electrolytic capacitor R1: balancing resistor R2: balancing resistor

[0087] R3: Balancing resistor VM1: Voltage detector VM2: Voltage detector

[0088] VM3: Voltage detector AM1: Current detector DETAILED DESCRIPTION

[0089] As mentioned above, a plurality of series branches connected in series are arranged on the DC bus side of the frequency converter, and each series branch includes a plurality of electrolytic capacitors connected in parallel. When determining whether there are electrolytic capacitors with reverse polarity in each series branch by detecting the branch voltage of each series branch, when there are electrolytic capacitors with reverse polarity in each series branch, the voltage division of each series branch is the same as when there are no electrolytic capacitors with reverse polarity in each series branch. Therefore, when there are electrolytic capacitors with reverse polarity in each series branch, correct detection results cannot be obtained according to the branch voltage of each series branch, thereby resulting in the inability to accurately detect the electrolytic capacitors with reverse polarity.

[0090] In an embodiment of the present invention, when detecting whether there are electrolytic capacitors with reverse polarity on the variable frequency bus side, the branch voltage of each series branch is detected respectively and the loop current of each series branch is detected. According to the branch voltage of each series branch, it can be determined whether there are electrolytic capacitors with reverse polarity in some of the series branches. According to the branch voltage and loop current of each series branch, it can be determined whether there are electrolytic capacitors with reverse polarity in all of the series branches. Therefore, whether there are electrolytic capacitors with reverse polarity in some of the series branches or in all of the series branches, it can be accurately determined whether there are electrolytic capacitors with reverse polarity, thereby improving the accuracy of detecting whether there are electrolytic capacitors with reverse polarity.

[0091] The capacitor polarity reverse detection method and device provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0092] like Figure 1 As shown, an embodiment of the present invention provides a method for detecting reverse polarity of a capacitor, which may include the following steps:

[0093] Step 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, wherein each series branch includes at least two electrolytic capacitors connected in parallel with each other, and at least two series branches are sequentially connected in series and connected to two poles of the test power supply;

[0094] Step 102: Detect the branch voltages at both ends of each series branch respectively;

[0095] Step 103: Detect the loop current output by the test power supply;

[0096] Step 104: determine whether the branch voltage of at least one of the series branches exceeds the voltage threshold. If it is Y, execute step 105; if not, execute step 106.

[0097] Step 105: Determine whether there is an electrolytic capacitor with reverse polarity in each series branch, and end the current process;

[0098] Step 106: Determine whether the loop current exceeds the current threshold, if it is Y, execute step 105, if not N, execute step 107;

[0099] Step 107: Determine that there is no electrolytic capacitor with reverse polarity in each series branch.

[0100] In an embodiment of the present invention, a voltage threshold and a current threshold are set in advance according to the output voltage of the test power supply and the balanced current of each series branch. When there is no reverse polarity electrolytic capacitor in each series branch, the branch voltage of each series branch will not exceed the set voltage threshold, and the loop current flowing through each series branch will not exceed the current threshold. When detecting whether there is a reverse polarity electrolytic capacitor, the branch voltage of each series branch and the loop current output by the test power supply are detected respectively. When there is a branch voltage of at least one series branch exceeding the voltage threshold, it can be determined that there is a reverse polarity electrolytic capacitor in at least one series branch. When the branch voltage of all series branches does not exceed the voltage threshold, it is impossible to determine whether there is a reverse polarity electrolytic capacitor according to the branch voltage, and then judge whether the loop current exceeds the current threshold. If the loop current exceeds the current threshold, it can be determined that there is a reverse polarity electrolytic capacitor in each series branch. If the loop current does not exceed the current threshold, it can be determined that there is no reverse polarity electrolytic capacitor in each series branch. It can be seen from this that by detecting the electrolytic capacitor with reverse polarity based on the branch current of each series branch and the loop current of the loop formed by each series branch, no matter whether there are electrolytic capacitors with reverse polarity in some of the series branches or there are electrolytic capacitors with reverse polarity in all the series branches, it is possible to accurately detect whether there are electrolytic capacitors with reverse polarity, thereby improving the accuracy of detecting the electrolytic capacitors with reverse polarity.

[0101] In an embodiment of the present invention, for any series branch, since the reverse leakage current of the electrolytic capacitor is significantly greater than the normal leakage current, when there are one or more electrolytic capacitors with reverse polarity in the series branch, the voltage division of the series branch will be reduced, and the voltage division is the branch voltage of the series branch. Then, whether there is an electrolytic capacitor with reverse polarity in the series branch can be determined based on whether the branch voltage of the series branch is lower than the voltage threshold.

[0102] In an embodiment of the present invention, when there is no reverse polarity electrolytic capacitor in each series branch, each series branch has an approximately equal equivalent resistance, and each series branch has a similar branch voltage division. Because the reverse leakage current of the electrolytic capacitor is significantly greater than the normal leakage current, when there is a reverse polarity electrolytic capacitor in a series branch, the equivalent resistance of the series branch will drop to a lower level, and the number of reverse polarity electrolytic capacitors in the same series branch has a smaller impact on the equivalent resistance of the series branch, so when there is a reverse polarity electrolytic capacitor in each series branch, the equivalent resistance of each series branch is still substantially equal, and each series branch still has a similar branch voltage division. In summary, when there is a reverse polarity electrolytic capacitor in all series branches, it is impossible to detect whether there is a reverse polarity electrolytic capacitor in each series branch according to the branch voltage division of each series branch.

[0103] In an embodiment of the present invention, since the reverse leakage current of the electrolytic capacitor is significantly greater than the normal leakage current, when there is an electrolytic capacitor with reverse polarity in a series branch, the equivalent resistance of the series branch will drop to a lower level. If there are electrolytic capacitors with reverse polarity in all series branches, the equivalent resistance of each series branch will be reduced, and under the premise that the test power supply outputs a constant voltage, the loop current of the loop formed by the test power supply and each series branch will increase, so that when the branch voltage of each series branch does not exceed the voltage threshold and the loop current exceeds the current threshold, it can be determined that each series branch includes an electrolytic capacitor with reverse polarity, that is, it can be determined that there is an electrolytic capacitor with reverse polarity in each series branch.

[0104] Optionally, in Figure 1 On the basis of the capacitor polarity reverse connection detection method shown, when the voltage threshold of the equivalent impedance of each series branch is determined according to the output voltage of the test power supply and the equivalent impedance of each series branch, the voltage threshold can 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 brought into the following first formula, and the voltage threshold is calculated by the following first formula. The first formula includes:

[0105]

[0106] Among them, V t is used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, k 1 Used to characterize the voltage correction factor determined based on the voltage acquisition error.

[0107] In an embodiment of the present invention, since the output voltage of the test power supply remains unchanged, when the branch voltage of some series branches decreases, the branch voltage of other series branches will increase. An interval range is determined as the voltage threshold according to the output voltage of the test power supply and the equivalent resistance of each series branch. When the branch voltage of a series branch is greater than the upper limit of the interval range or less than the decrease of the interval range, it can be determined that there are electrolytic capacitors with reverse polarity in each series branch, which is convenient for detecting the electrolytic capacitors with reverse polarity.

[0108] In an embodiment of the present invention, since voltage detection errors may exist when detecting the branch voltages of each series branch and the output voltage of the test power supply, in order to avoid misjudgment due to voltage detection errors, a voltage threshold with a wider range is obtained by setting a voltage correction coefficient to reduce the probability of erroneous detection results due to voltage detection errors.

[0109] When n is equal to 20, Considering the possible detection error when detecting the output voltage of the test power supply and the possible detection error when detecting the branch voltage of each series branch, the voltage correction coefficient k is used to 1 The voltage threshold V is obtained after correction t ∈(-3%V, 3%V).

[0110] Optionally, in Figure 1 On the basis of the capacitor polarity reverse detection method shown, when determining the current threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch, the current threshold can 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 can be brought into the following second formula, and the current threshold can be calculated by the following second formula. The second formula is:

[0111]

[0112] Among them, I t is used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in a series branch to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each series branch, k 2 Used to characterize the current correction factor determined based on the current acquisition error.

[0113] In an embodiment of the present invention, since the reverse leakage current of the electrolytic capacitor is significantly greater than the normal leakage current, when there is an electrolytic capacitor with reverse polarity in each series branch, the total equivalent impedance of each series branch decreases, and the loop current of the loop formed after each series branch is connected to the test power supply increases. Therefore, the current threshold can be calculated based on the output voltage of the test power supply and the equivalent impedance of each series branch. When it is detected that the loop current is less than the current threshold, it can be determined that there is an electrolytic capacitor with reverse polarity in each series branch.

[0114] In an embodiment of the present invention, since there may be a current detection error when detecting the loop current, in order to avoid the misjudgment of the reverse polarity of the electrolytic capacitor due to the current detection error, a larger current threshold is obtained by setting a voltage correction coefficient to reduce the probability of an erroneous polarity detection result due to the current detection error.

[0115] When n is equal to 20, Considering the possible error when collecting loop current, the current correction factor k is used 2 Correction is made so that the current threshold Wherein, R is used to characterize the equivalent impedance of each series branch, and the equivalent impedance specifically refers to the sum of the equivalent resistances of each series branch.

[0116] Optionally, in Figure 1 On the basis of the capacitor polarity reverse connection detection method shown, if step 104 and step 105 determine that there is an electrolytic capacitor with reverse polarity in each series branch according to the branch voltage of each series branch, then it can be further determined whether there is an electrolytic capacitor with reverse polarity in each series branch according to the branch voltage of each series branch. Specifically, it can be determined whether there is an electrolytic capacitor with reverse polarity in a series branch by the following method:

[0117] For each series branch, if the branch voltage of the series branch is less than the lower limit of the voltage threshold, it is determined that at least one electrolytic capacitor with reverse polarity exists in the series branch.

[0118] In the embodiment of the present invention, since the electrolytic capacitor with reversed polarity will cause the equivalent resistance of the series branch in which it is located to decrease, and the decrease in equivalent resistance will cause the branch voltage of the corresponding series branch to decrease, after determining that there is an electrolytic capacitor with reversed polarity in at least one series branch according to the branch voltages of each series branch, it can be determined whether the branch voltage of each series branch is less than the lower limit of the voltage threshold. If the branch voltage of a series branch is less than the lower limit of the voltage threshold, it can be determined that there is an electrolytic capacitor with reversed polarity in the series branch. Correspondingly, if the branch voltage of a series branch is greater than the upper limit of the voltage threshold, it can be determined that there is no electrolytic capacitor with reversed polarity in the series branch.

[0119] In an embodiment of the present invention, after determining that there are electrolytic capacitors with reverse polarity in some of the series branches, it is possible to determine whether the branch voltage of each series branch is less than the lower limit of the voltage threshold, and then determine the series branches including the electrolytic capacitors with reverse polarity, thereby locating the electrolytic capacitors with reverse polarity, so that users can more conveniently find the electrolytic capacitors with reverse polarity, and then process the electrolytic capacitors with reverse polarity.

[0120] Optionally, in Figure 1 Based on the capacitor polarity reverse detection method shown, if step 106 and step 105 determine that there is an electrolytic capacitor with reverse polarity in each series branch according to the loop current, it can be further determined that there is an electrolytic capacitor with reverse polarity in each series branch.

[0121] In the embodiment of the present invention, since it is first determined whether there are electrolytic capacitors with reverse polarity in each series branch based on the branch voltage of each series branch, after it is impossible to determine whether there are electrolytic capacitors with reverse polarity in each series branch based on the branch voltage of each series branch, it is then determined whether there are electrolytic capacitors with reverse polarity in each series branch based on the loop current. If it is determined that there are electrolytic capacitors with reverse polarity in each series branch based on the loop current, only the situation that there are electrolytic capacitors with reverse polarity in all series branches is included.

[0122] In an embodiment of the present invention, after determining that there are electrolytic capacitors with reverse polarity in each series branch based on the loop current, it can be further determined that there are electrolytic capacitors with reverse polarity in each series branch, thereby realizing polarity positioning of the electrolytic capacitors with reverse polarity in the inverter, and the user can more conveniently find the electrolytic capacitors with reverse polarity and repair the electrolytic capacitors with reverse polarity.

[0123] Optionally, in Figure 1 On the basis of the capacitor polarity reverse connection detection method shown, for each series branch, the series branch includes at least two electrolytic capacitors and at least one balancing resistor connected in parallel. Since there may be performance differences between different electrolytic capacitors, that is, different electrolytic capacitors may have different equivalent resistances, by connecting a balancing resistor in parallel in each series branch, different series branches can have the same equivalent impedance, thereby balancing the voltage division of each series branch, avoiding the situation where the electrolytic capacitors of each series branch are damaged due to unbalanced voltage division, and ensuring the safety of the inverter.

[0124] Optionally, based on the capacitor polarity reverse detection method provided in the above-mentioned embodiments, the number of series branches connected to the DC bus side of the inverter varies according to the voltage of the system in which the inverter is located. For example, in a 400V system, two series branches are generally connected in series, while in a 690V system, three series branches are generally connected in series.

[0125] like Figure 2 In the 400V system shown, electrolytic capacitors C11 to C1n and balancing resistor R1 are connected in parallel to form a first series branch, electrolytic capacitors C21 to C2n and 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 the two poles of the test power supply E1, the voltage detector VM1 is used to detect the branch voltage of the first series branch, the voltage detector VM2 is used to detect the branch voltage of the second series branch, and the current detector AM1 is used to detect the 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. According to the difference in the detected branch voltage and loop current, there are the following four situations:

[0126] A. If the branch voltage detected by the voltage detector VM1 is less than the lower limit of the voltage threshold, and the branch voltage detected by the 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 reverse polarity in the first series branch, and there is no electrolytic capacitor with reverse polarity in the second series branch.

[0127] B. If the branch voltage detected by the voltage detector VM1 is greater than the upper limit of the voltage threshold, and the branch voltage detected by the voltage detector VM2 is less than the lower limit of the voltage threshold, it is determined that there is no electrolytic capacitor with reverse polarity in the first series branch, and there is at least one electrolytic capacitor with reverse polarity in the second series branch.

[0128] C. If the branch voltage detected by the voltage detector VM1 and the branch voltage detected by the voltage detector VM2 do not exceed the voltage threshold, that is, they are both 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, then it is determined that there is at least one electrolytic capacitor with reverse polarity in the first series branch and the second series branch.

[0129] D. If the branch voltage detected by the voltage detector VM1 and the branch voltage detected by the voltage detector VM2 do not exceed the voltage threshold, that is, they are both 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 are no electrolytic capacitors with reverse polarity in the first series branch and the second series branch.

[0130] like Figure 3 In the 690V system shown, electrolytic capacitors C11 to C1n and balancing resistor R1 are connected in parallel to form a first series branch, electrolytic capacitors C21 to C2n and balancing resistor R2 are connected in parallel to form a second series branch, electrolytic capacitors C31 to C3n and 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 the two poles of the test power supply E1, the voltage detector VM1 is used to detect the branch voltage of the first series branch, the voltage detector VM2 is used to detect the branch voltage of the second series branch, the voltage detector VM3 is used to detect the branch voltage of the third series branch, and the current detector AM1 is used to detect the loop current output by the test power supply E1. After closing the switch K1, the branch voltages detected by the voltage detector VM1, the voltage detector VM2 and the voltage detector VM3 are obtained, and the loop current detected by the current detector AM1 is obtained. According to the differences in the detected branch voltages and loop currents, there are the following three situations:

[0131] A. If the branch voltage detected by any one of the voltage detectors VM1, VM2 and 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 there is at least one electrolytic capacitor with reverse polarity in the series branch whose branch voltage is less than the lower limit of the voltage threshold, and there is no electrolytic capacitor with reverse polarity in the series branches whose other two branch voltages are greater than the upper limit of the voltage threshold.

[0132] B. If the branch voltages detected by any two of the voltage detectors VM1, VM2 and VM3 are less than the lower limit of the voltage threshold, and the branch voltage detected by the remaining voltage detector is greater than the upper limit of the voltage threshold, it is determined that there is at least one electrolytic capacitor with reverse polarity in the two series branches whose branch voltages are less than the lower limit of the voltage threshold, and there is no electrolytic capacitor with reverse polarity in the other series branch whose branch voltage is greater than the upper limit of the voltage threshold.

[0133] C. 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 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, then it is determined that there is at least one electrolytic capacitor with reverse polarity in the first series branch, the second series branch and the third series branch.

[0134] 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 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, then it is determined that there are no electrolytic capacitors with reverse polarity in the first series branch, the second series branch and the third series branch.

[0135] It should be noted that when the output voltage of the test power supply is small, the measurement resolution of the branch voltage and loop current will be low, and the branch voltage of each series branch will change slowly, making it impossible to detect the reverse polarity of the electrolytic capacitor. When the output voltage of the test power supply is large, it may cause the inverter under test to malfunction and be damaged. Usually, a test power supply with an output voltage of 200V can be selected for capacitor reverse polarity detection.

[0136] The capacitor polarity reverse connection detection method provided by the above embodiments is verified by a specific example below. The DC bus side of an inverter is connected with three series branches, each of which includes 8 electrolytic capacitors and a balancing resistor connected in parallel, and the equivalent impedance of each series branch is 3.3 kΩ. The polarity reverse connection detection results of the electrolytic capacitors connected to the DC bus side of the inverter are shown in Table 1 below.

[0137] Table 1

[0138]

[0139] In the above Table 1, one series branch reverse connection means that there is an electrolytic capacitor with reverse polarity in one series branch, two series branches reverse connection means that there are electrolytic capacitors with reverse polarity in two series branches, and three series branches reverse connection means that there are electrolytic capacitors with reverse polarity in three series branches. Series branch voltage division deviation = (normal series branch voltage - detected series branch voltage) / normal series branch voltage, wherein the normal series branch voltage is the voltage division of the series branch when there is no reverse connection of the electrolytic capacitor in the corresponding series branch, and the detected series branch voltage is the voltage division of the corresponding series branch detected by the voltage detector.

[0140] like Figure 4 As shown, an embodiment of the present invention provides a capacitor polarity reverse connection detection device, comprising:

[0141] A threshold determination module 401, used 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, wherein each series branch includes at least two electrolytic capacitors connected in parallel with each other, and at least two series branches are sequentially connected in series and connected to two poles of the test power supply;

[0142] A voltage detection module 402, used to detect the branch voltage at both ends of each series branch;

[0143] A current detection module 403, used to detect the loop current output by the test power supply;

[0144] A voltage comparison module 404, configured to determine whether the branch voltage of at least one of the at least two series 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;

[0145] A first result output module 405, configured to determine that there is an electrolytic capacitor with reverse polarity in at least two series branches when the voltage comparison module 404 determines that the branch voltage of at least one series branch in the at least two series branches exceeds the voltage threshold;

[0146] 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 there is no branch voltage of any series branch exceeding the voltage threshold;

[0147] A second result output module 407 is used to determine that there are reverse-polarity electrolytic capacitors in at least two series branches when the current comparison module 406 determines that the loop current exceeds the current threshold, and to determine that there are no reverse-polarity electrolytic capacitors in at least two series branches when the current comparison module 406 determines that the loop current does not exceed the current threshold.

[0148] In an embodiment of the present invention, the voltage detection module 402 can be used to execute step 101 in the above method embodiment, the current detection module 403 can be used to execute step 103 in the above method embodiment, the voltage comparison module 404 can be used to execute step 104 in the above method embodiment, the first result output module 405 can be used to execute step 105 in the above method embodiment, the current comparison module 406 can be used to execute step 106 in the above method embodiment, and the second result output module 407 can be used to execute step 107 in the above method embodiment.

[0149] Optionally, in Figure 4 The capacitor polarity reverse detection device shown is based on Figure 5 As shown, the threshold determination module 401 includes: a voltage threshold determination unit 4011;

[0150] The voltage threshold determination unit 4011 is used to calculate the voltage threshold by the following first formula according to the output voltage of the test power supply and the equivalent impedance of each series branch;

[0151] The first formula includes:

[0152]

[0153] Among them, V t It is used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in a series branch to the balancing resistance, and the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, k 1 Used to characterize the voltage correction factor determined based on the voltage acquisition error.

[0154] Optionally, in Figure 4 The capacitor polarity reverse detection device shown is based on Figure 6 As shown, the threshold determination module 401 includes: a current threshold determination unit 4012;

[0155] The current threshold determination unit 4012 is used to calculate the current threshold by the following second formula according to the output voltage of the test power supply and the equivalent impedance of each series branch;

[0156] The second formula includes:

[0157]

[0158] Among them, I t It is used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in a series branch to the balancing resistance. The balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each series branch, and k 2 Used to characterize the current correction factor determined based on the current acquisition error.

[0159] Optionally, in Figure 4 Based on the capacitor polarity reverse connection detection device shown, the first result output module 405 is further used to determine that there is at least one electrolytic capacitor with reverse polarity in the series branch when the voltage comparison module 404 determines that the branch voltage of a series branch is less than the lower limit of the voltage threshold.

[0160] Optionally, in Figure 4 Based on the capacitor polarity reverse detection device shown, the second result output module 407 is further used to determine that there are reverse polarity electrolytic capacitors in each series branch when the current comparison module 406 determines that the loop current exceeds the current threshold.

[0161] It should be noted that the capacitor polarity reverse detection device provided in the above-mentioned embodiments is based on the same concept as the aforementioned capacitor polarity reverse detection method. The interaction between the modules in the capacitor polarity reverse detection device can be found in the description in the aforementioned capacitor polarity reverse detection method embodiment, which will not be repeated here.

[0162] like Figure 7 As shown, an embodiment of the present invention provides a capacitor polarity reverse detection device, including: at least one memory 408 and at least one processor 409;

[0163] The at least one memory 408 is used to store a machine-readable program;

[0164] The at least one processor 409 is configured to call the machine-readable program to execute the capacitor polarity reverse connection detection method provided in the above embodiments.

[0165] The present invention also provides a computer-readable medium storing instructions for causing a computer to execute the capacitor polarity reversal detection method as described herein. Specifically, a system or device equipped with a storage medium can be provided, on which a software program code for implementing the functions of any of the above embodiments is stored, and a computer (or CPU or MPU) of the system or device reads and executes the program code stored in the storage medium.

[0166] In this case, the program code itself read from the storage medium can realize the function of any one of the above-mentioned embodiments, and thus the program code and the storage medium storing the program code constitute a part of the present invention.

[0167] The storage medium embodiments for providing the program code include a floppy disk, a hard disk, a magneto-optical disk, an optical disk (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), a magnetic tape, a non-volatile memory card, and a ROM. Alternatively, the program code can be downloaded from a server computer by a communication network.

[0168] In addition, it should be clear that the functions of any of the above embodiments can be implemented not only by executing the program code read by the computer, but also by enabling an operating system operating on the computer to complete part or all of the actual operations based on instructions from the program code.

[0169] In addition, it can be understood that the program code read from the storage medium is written to a memory provided in an expansion board inserted into the computer or written to a memory provided in an expansion unit connected to the computer, and then based on the instructions of the program code, a CPU installed on the expansion board or the expansion unit is enabled to perform part or all of the actual operations, thereby realizing the functions of any of the above-mentioned embodiments.

[0170] It should be noted that not all steps and modules in the above-mentioned processes and system structure diagrams are necessary, and some steps or modules can be ignored according to actual needs. The execution order of each step is not fixed and can be adjusted as needed. The system structure described in the above-mentioned embodiments can 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 multiple physical entities, or some components in multiple independent devices may be implemented together.

[0171] In the above embodiments, the hardware unit can be realized by mechanical means or electrical means. For example, a hardware unit can include permanent dedicated circuits or logic (such as special processors, FPGA or ASIC) to complete the corresponding operation. The hardware unit can also include programmable logic or circuits (such as general-purpose processors or other programmable processors), which can be temporarily set by software to complete the corresponding operation. Concrete implementation (mechanical means or dedicated permanent circuits or temporarily set circuits) can be determined based on cost and time considerations.

[0172] The present invention has been shown and described in detail above through the accompanying drawings and preferred embodiments. However, the present invention is not limited to these disclosed embodiments. Based on the above multiple embodiments, those skilled in the art can know that the code review methods in the above different embodiments can be combined to obtain more embodiments of the present invention, and these embodiments are also within the protection scope of the present invention.

Claims

1. A method for detecting reverse polarity of a capacitor, characterized in that: include: Determine 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, wherein each series branch includes at least two electrolytic capacitors connected in parallel with each other, and at least two of the series branches are sequentially connected in series and then connected to two poles of the test power supply (101); Respectively detecting the branch voltages at both ends of each of the series branches (102); 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); If the branch voltage of at least one of the at least two series branches exceeds the voltage threshold, determining that the electrolytic capacitor (105) with reverse polarity exists in the at least two series branches; If the branch voltage of any of the at least two series branches does not exceed the voltage threshold, determining whether the loop current exceeds the current threshold (106); If the loop current exceeds the current threshold, determining that there is an electrolytic capacitor (105) with reverse polarity in the at least two series branches; If the loop current does not exceed the current threshold, it is determined that there is no reverse-polarity electrolytic capacitor (107) in the at least two series branches.

2. The method according to claim 1, characterized in that The step of determining the voltage threshold according to the output voltage of the test power supply and the equivalent impedance of each series branch includes: Calculating the voltage threshold by the following first formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches; The first formula includes: Among them, the V t Used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k1 is used to characterize the voltage correction coefficient determined according to the voltage acquisition error.

3. The method according to claim 1, characterized in that: The step of determining the current threshold value according to the output voltage of the test power supply and the equivalent impedance of each series branch includes: 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 the following second formula; The second formula includes: Among them, the I t Used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in a series branch to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each series branch, and k2 is used to characterize the current correction coefficient determined according to the current acquisition error.

4. The method according to claim 1, characterized in that: After determining whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold, the method further includes: For each of the series branches, if the branch voltage of the series branch is less than a lower limit of the voltage threshold, it is determined that at least one electrolytic capacitor with reverse polarity exists in the series branch.

5. The method according to claim 1, characterized in that After determining whether the loop current exceeds the current threshold, the method further includes: If the loop current exceeds the current threshold, it is determined that the electrolytic capacitor with reverse polarity exists in each of the series branches.

6. The method according to any one of claims 1 to 5, characterized in that: For each of the series branches, the series branch includes at least two 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. A capacitor polarity reverse connection detection device, characterized in that: include: A threshold determination module (401) is used to determine a voltage threshold and a current threshold according to an output voltage of a test power supply and an equivalent impedance of each series branch, wherein each series branch comprises at least two electrolytic capacitors connected in parallel with each other, and at least two of the series branches are sequentially connected in series and connected to two poles of the test power supply; A voltage detection module (402) is used to detect the branch voltage at both ends of each of the series branches respectively; A current detection module (403) for detecting a loop current output by the test power supply; a voltage comparison module (404) configured to determine, based on the voltage threshold determined by the threshold determination module (401) and the branch voltage detected by the voltage detection module (402), whether the branch voltage of at least one of the at least two series branches exceeds the voltage threshold; a first result output module (405) for determining that the electrolytic capacitor with reverse polarity exists in the at least two series branches when the voltage comparison module (404) determines that the branch voltage of at least one of 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 none of the at least two series branches has a branch voltage exceeding the voltage threshold; A second result output module (407) is used to determine that the electrolytic capacitor with reverse polarity exists in the at least two series branches when the current comparison module (406) determines that the loop current exceeds the current threshold, and to determine that the electrolytic capacitor with reverse polarity does not exist 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 device according to claim 7, characterized in that The threshold determination module (401) comprises: a voltage threshold determination unit (4011); The voltage threshold determination unit (4011) is used to calculate the voltage threshold by the following first formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches; The first formula includes: Among them, the V t Used to characterize the voltage threshold, V is used to characterize the output voltage of the test power supply, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in one of the series branches to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, and k1 is used to characterize the voltage correction coefficient determined according to the voltage acquisition error.

9. The device according to claim 7, characterized in that The threshold determination module (401) comprises: a current threshold determination unit (4012); The current threshold determination unit (4012) is used to calculate the current threshold by the following second formula according to the output voltage of the test power supply and the equivalent impedance of each of the series branches; The second formula includes: Among them, the I t Used to characterize the current threshold, n is used to characterize the ratio of the equivalent impedance of each electrolytic capacitor connected in parallel in a series branch to the balancing resistance, the balancing resistance is the resistance connected in parallel with each electrolytic capacitor in the series branch, V is used to characterize the output voltage of the test power supply, R is used to characterize the sum of the equivalent impedances of each series branch, and k2 is used to characterize the current correction coefficient determined according to the current acquisition error.

10. The device according to claim 7, characterized in that The first result output module (405) is further used to determine that there is at least one electrolytic capacitor with reverse polarity in the series branch when the voltage comparison module (404) determines that the branch voltage of one of the series branches is less than the lower limit of the voltage threshold.

11. The device according to claim 7, characterized in that The second result output module (407) is further used to determine that the electrolytic capacitor with reverse polarity exists in each of the series branches when the current comparison module (406) determines that the loop current exceeds the current threshold.

12. A capacitor polarity reverse connection detection device, characterized in that: include: at least one memory (408) and at least one processor (409); The at least one memory (408) is used to store a machine-readable program; The at least one processor (409) is configured to call the machine-readable program to execute the method according to any one of claims 1 to 6.

13. A computer readable medium, characterized in that The computer readable medium stores computer instructions, which, when executed by a processor, cause the processor to perform any one of the methods of claims 1 to 6.

Images