Method and device for determining switch open circuit fault of inverter

Abstract

The present invention discloses a method and device for determining an open-circuit switch fault of an inverter, and belongs to the field of fault diagnosis technology. The method comprises: collecting multiple samples of the output voltage within a switching cycle for each H-bridge unit in the CHB inverter, and calculating the output voltage average value of each H-bridge unit according to the collected samples; calculating the output voltage prediction value of each H-bridge unit of the CHB inverter under a fault-free condition according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit; judging whether an open-circuit switch fault occurs in the H-bridge unit according to the ratio of the output voltage average value of each H-bridge unit to the output voltage prediction value. The present invention can diagnose whether an open-circuit switch fault occurs in each H-bridge unit within a switching cycle, which not only reduces the amount of calculation, but also reduces the control deviation caused by complex signal processing, thereby improving the control accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of fault diagnosis, and in particular to a method and device for determining an open-circuit switch fault of an inverter. Background Art

[0002] CHB inverters have become an indispensable component of high-power industrial drives. Since CHB inverters contain a large number of semiconductor switches, the possibility of switch failure is increased. If the open circuit failure of the switch is not discovered during long-term system operation, it will cause secondary failure of the CHB inverter and even cause system shutdown. Therefore, it is necessary to diagnose the open circuit failure of the switch.

[0003] In the related technology, the switch open circuit fault detection methods include fast Fourier transform method, frequency domain analysis method, and fuzzy-based fault classifier method, etc. However, these methods involve complex matrix operations and need to collect multiple fault quantities. Not only does the detection cycle last long, but the control accuracy is also poor due to the large control deviation. Summary of the invention

[0004] The present invention provides a method and device for determining an open circuit fault of a switch of an inverter, which can solve the problems existing in the related art. The technical solution is as follows:

[0005] On the one hand, a method for determining an open-circuit switch fault of an inverter is provided, wherein the CHB inverter comprises a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the method comprises:

[0006] Collecting multiple samples of the output voltage of each H-bridge unit in the CHB inverter within a switching cycle, and calculating the output voltage average value of each H-bridge unit according to the collected samples;

[0007] Calculate the output voltage prediction value of each H-bridge unit of the CHB inverter in the absence of a fault according to the modulation ratio selected by the CHB inverter and the DC voltage input to each H-bridge unit;

[0008] According to the ratio of the output voltage average value of each H-bridge unit to the output voltage prediction value, it is determined whether the H-bridge unit has a switch open circuit fault.

[0009] On the other hand, a switch open circuit fault determination device of an inverter is provided, wherein the CHB inverter comprises a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the device comprises:

[0010] A collection and calculation unit, used for collecting a plurality of samples of the output voltage within a switching cycle for each H-bridge unit in the CHB inverter, and calculating the output voltage average value of each H-bridge unit according to the collected samples;

[0011] A prediction calculation unit, used to calculate the output voltage prediction value of each H-bridge unit of the CHB inverter in a fault-free state according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit;

[0012] The fault determination unit is used to determine whether a switch open circuit fault occurs in each H-bridge unit according to the ratio of the output voltage average value to the output voltage prediction value of each H-bridge unit.

[0013] On the other hand, a computer device is provided, which includes a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to implement the steps of the above-mentioned method for determining an open circuit switch fault of an inverter.

[0014] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored in the storage medium, and when the computer program is executed by a processor, the steps of the method for determining an open circuit switch fault of the inverter are implemented.

[0015] On the other hand, a computer program product is provided, comprising a computer program, wherein when the computer program is executed by a processor, the steps of the method for determining an open circuit switch fault of an inverter are implemented as described above.

[0016] The technical solution provided by the present invention can at least bring the following beneficial effects:

[0017] By calculating the output voltage average value and the output voltage prediction value of each H-bridge unit and comparing and analyzing the two values, it is possible to determine whether a switch open circuit fault occurs in each H-bridge unit. This scheme can diagnose whether a switch open circuit fault occurs in each H-bridge unit within one switching cycle. It not only reduces the amount of calculation, but also reduces the control deviation caused by complex signal processing and improves the control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1is a flow chart of a method for determining an open circuit switch fault of an inverter provided by an embodiment of the present invention;

[0020] Figure 2 is a topological structure diagram of a CHB inverter provided by an embodiment of the present invention;

[0021] Figure 3 is a schematic diagram of an LS-PWM modulation strategy provided by an embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of an LS-PWM modulation strategy provided by an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of the influence of the switch failures in different H-bridges on the proposed judgment index provided by an embodiment of the present invention;

[0024] Figure 6 It is a structural diagram of a switch open circuit fault determination device for an inverter provided by an embodiment of the present invention;

[0025] Figure 7 It is a hardware architecture diagram of a computer device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Please refer to Figure 1 , an embodiment of the present invention provides a method for determining an open-circuit switch fault of an inverter, wherein the CHB inverter comprises a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the method comprises:

[0028] Step 100, collecting multiple samples of the output voltage within a switching cycle for each H-bridge unit in the CHB inverter, and calculating the output voltage average value of each H-bridge unit according to the collected samples;

[0029] Step 102, calculating the output voltage prediction value of each H-bridge unit of the CHB inverter in a fault-free state according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit;

[0030] Step 104 , determining whether a switch open circuit fault occurs in each H-bridge unit according to the ratio of the output voltage average value to the output voltage prediction value of each H-bridge unit.

[0031] In the embodiment of the present invention, by calculating the output voltage average value and the output voltage prediction value of each H-bridge unit and comparing and analyzing the two values, it is possible to determine whether a switch open circuit fault occurs in each H-bridge unit. This solution can diagnose whether a switch open circuit fault occurs in each H-bridge unit within one switching cycle, which not only reduces the amount of calculation, but also reduces the control deviation caused by complex signal processing, thereby improving the control accuracy.

[0032] Please refer to Figure 2 , is a topological structure diagram of a CHB inverter according to an embodiment of the present invention. The CHB inverter is a single-phase cascade H-bridge inverter, which is used to convert an input DC voltage into an AC voltage output. The CHB inverter includes n H-bridge units connected in series, each of which includes two complementary switch pairs. The first complementary switch pair is S x1 / S x3 , the second complementary switch pair is S x2 / S x4 ; x Used to characterize the first x H-bridge units, x is 1, 2, ..., n. Please refer to Figure 3 , which is a schematic diagram of the LS-PWM modulation strategy of the CHB inverter according to an embodiment of the present invention. The modulation strategy can select different carrier combinations to obtain different switching time sequences, and finally eliminate low-order harmonics to obtain a higher output voltage waveform quality.

[0033] Taking n=3 as an example, the DC voltage amplitude of the CHB inverter input is equal, that is, The output AC voltages are V 1. V 2. V 3. The output voltage of CHB inverter is V p , then it satisfies:

[0034]

[0035] The CHB inverter can output 7 levels in total , and at the CHB inverter output level There are redundant synthesis methods. Figure 3The schematic diagram of different output level synthesis methods corresponds to different PWM waveform working modes, and under different PWM waveform working modes, the output voltage waveform of the cascade unit is also different. When the output level synthesis method of the CHB inverter is: (111)-(011)-(001)-(000)-(00-1)-(0-1-1)-(-1-1-1), the LS-PWM modulation strategy principle diagram is as follows: Figure 4 As shown, Figure 4 middle c 1+ and c 1- is the carrier corresponding to the first H-bridge unit, c 2+ and c 2- is the carrier corresponding to the second H-bridge unit, c 3+ and c 3- is the carrier corresponding to the third H-bridge unit, u ref is the reference sinusoidal signal, and its expression is:

[0036]

[0037] in, M is the modulation ratio.

[0038] Under the LS-PWM modulation strategy, when the carrier frequency is much larger than the modulation frequency, the average output voltage (HCMV) of the CHB inverter in the positive half cycle is equal to the instantaneous value of the expected output voltage of the CHB inverter, and the same is true for the negative half cycle.

[0039] When a switch failure occurs, the CHB inverter needs to be diagnosed.

[0040] Described below Figure 1 How the various steps are performed.

[0041] First, with respect to step 100, a plurality of samples of the output voltage within a switching cycle are collected for each H-bridge unit in the CHB inverter, and an average output voltage of each H-bridge unit is calculated based on the collected samples.

[0042] During operation, the CHB inverter can collect the output voltage of each H-bridge unit according to the preset collection interval, thereby obtaining multiple samples within a switching cycle. V ox A switching cycle includes a positive half cycle and a negative half cycle, so the average output voltage of the positive half cycle is M xP and the average output voltage of the negative half cycle MxN It can be calculated by the following formula:

[0043]

[0044]

[0045] in, , 2 m is the total number of samples of the output voltage collected in a switching cycle, and m is the number of samples of the output voltage collected in half a cycle.

[0046] Then, for step 102, according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit, the output voltage prediction value of each H-bridge unit of the CHB inverter in the absence of a fault is calculated.

[0047] When the CHB inverter is fault-free, the output voltage prediction value of each H-bridge unit is related to the modulation ratio M selected by the CHB inverter. When the DC voltage input to each H-bridge unit is equal, the output voltage prediction value of each H-bridge unit can be calculated by the following formula:

[0048]

[0049] in, M x(ref) It is the first in the CHB inverter x The predicted output voltage of each H-bridge unit, x =1, 2, …, n ; A, B, and C are all coefficients, which can be obtained by looking up the table. x The coefficient value is different when the value is different; M is the modulation ratio; the DC source voltage input to each H-bridge unit is equal and is V dc .

[0050] When the number of H-bridge units in the CHB inverter is different, the number of levels that the CHB inverter can output is also different, and the value of the coefficient of each H-bridge unit is also different. Please refer to Table 1 for the values ​​of the coefficients corresponding to the number of H-bridge units being 4, 3, and 2.

[0051] Table 1:

[0052]

[0053] It can be seen that after selecting the corresponding A, B, and C coefficient values, the calculated output voltage prediction values ​​of each H-bridge unit are different.

[0054] Finally, for step 104, it is determined whether a switch open circuit fault occurs in each H-bridge unit according to the ratio of the output voltage average value to the output voltage prediction value of each H-bridge unit.

[0055] In the embodiment of the present invention, whether a switch open circuit fault occurs in the corresponding H-bridge unit can be determined according to the size relationship between the corresponding ratio of each H-bridge unit and the low value threshold.

[0056] Considering that different H-bridge units have different on-times, the longer the on-time is, the more accurate the calculation of the output voltage average value using sampling is. Therefore, it is possible to first determine whether the target H-bridge unit with the largest on-time is faulty, and the determination result is more accurate.

[0057] Specifically, the determination of whether an open switch fault occurs in an H-bridge unit may include: determining a target H-bridge unit having the longest conduction time among a plurality of H-bridge units, and determining whether an open switch fault occurs in the target H-bridge unit; if a fault occurs, further determining a faulty switch in the target H-bridge unit; if no fault occurs, further determining whether other H-bridge units except the target H-bridge unit fail.

[0058] Assuming that the target H-bridge unit is the ath H-bridge unit, the average output voltage of the positive half cycle of the target H-bridge unit is M aP The average output voltage of the negative half cycle M aN are positive and negative respectively, and satisfy M aP =Max{ M xP}and M aN =Min{ M xN}.

[0059] Then, in the embodiment of the present invention, it can be determined whether the target H-bridge unit has a switch open circuit fault by the following method (S11-S12):

[0060] S11: dividing the average output voltage of the positive half cycle of the target H-bridge unit by the predicted output voltage of the positive half cycle to obtain the normalized value of the positive half cycle of the target H-bridge unit; dividing the average output voltage of the negative half cycle of the target H-bridge unit by the predicted output voltage of the negative half cycle to obtain the normalized value of the negative half cycle of the target H-bridge unit;

[0061] The positive half cycle normalized value of the target H-bridge unit can be obtained by the following normalization processing method: M aP % and negative half cycle normalized values M aN %:

[0062]

[0063]

[0064] After the above-mentioned standardized value is obtained, S12 is executed.

[0065] S12: Determine whether the normalized value of the positive half cycle of the target H-bridge unit is less than the low value threshold M th , if so, then S a1 / S a4 The switch pair fails; determining whether the negative half cycle normalized value of the target H-bridge unit is less than the low value threshold M th , if so, then S a2 / S a3 A switch pair has failed.

[0066] In the embodiment of the present invention, when determining whether a switch open circuit fault occurs in a corresponding H-bridge unit according to the size relationship between the corresponding ratio of each H-bridge unit and the low value threshold, only which switch pair is faulty can be determined for the target H-bridge unit, and the fault location of the specific switch cannot be realized, while which switch is faulty for other H-bridge units can be determined. The reasons are as follows:

[0067] Please continue to refer to Figure 4 , Figure 4 This is the LS-PWM modulation strategy schematic diagram corresponding to the inverter including three H-bridge units. The output voltage of each H-bridge unit is as follows: Figure 4 As shown in the lower middle part, the output voltage of the first H-bridge unit is V1, the output voltage of the second H-bridge unit is V2, the output voltage of the third H-bridge unit is V3, and the output voltage of the inverter is Vp. Since V3 has the longest conduction time, the third H-bridge unit is bridge a. When there are three H-bridge units, the inverter can output 7 levels: ±3Vdc, ±2Vdc, ±Vdc, and 0. According to the modulation strategy principle diagram, it can be seen that:

[0068] For positive half cycles:

[0069] If Vp outputs +3Vdc, then V3, V2, and V1 all output Vdc;

[0070] If Vp outputs +2Vdc, then V3 and V2 both output Vdc, and V1 outputs 0; that is:

[0071] If Vp outputs +Vdc, V3 outputs Vdc, and both V2 and V1 output 0;

[0072] If Vp output is 0, then V3, V2, and V1 all output 0;

[0073] The same applies to the negative half cycle.

[0074] It can be understood that the two switches on the left side of each H-bridge are complementary, and the two switches on the right side are complementary. If one switch is turned on, the corresponding complementary switch is turned off. In addition, in practical applications, the switches that need to be turned on when the H-bridge unit outputs 0, Vdc, and -Vdc can use a unique switch situation. For example, when the output is 0, only Sx3 and Sx4 are selected by default when the switches that need to be turned on are Sx3, Sx4 or Sx1, Sx2, and which pair of switches to select is known. Therefore, when the x-th H-bridge outputs Vdc, the switches that need to be turned on by default are: Sx1, Sx4; when the x-th H-bridge outputs 0, the switches that need to be turned on by default are: Sx3, Sx4; when the x-th H-bridge outputs -Vdc, the switches that need to be turned on by default are: Sx2, Sx3.

[0075] In summary:

[0076] When outputting +3Vdc, the switches turned on are: S11, S14; S21, S24; S31, S34;

[0077] When outputting +2Vdc, the switches turned on are: S13, S14; S21, S24; S31, S34;

[0078] When outputting +Vdc, the switches turned on are: S13, S14; S23, S24; S31, S34;

[0079] When the output is 0, the switches that are turned on are: S13, S14; S23, S24; S33, S34.

[0080] That is to say, the impact of the open-circuit faults of switch 1 and switch 4 on the output level in different H-bridges is:

[0081] S11: +3Vdc;

[0082] S14: +3 Vdc, +2 Vdc, +Vdc, 0, - Vdc, -2 Vdc;

[0083] S21: +3 Vdc, +2 Vdc;

[0084] S24: +3 Vdc, +2 Vdc, +Vdc, 0, - Vdc;

[0085] S31: +3 Vdc, +2 Vdc, +Vdc;

[0086] S34: +3 Vdc, +2 Vdc, +Vdc; 0.

[0087] It can be seen that the effect of switches 1 and 4 on the output level in bridge a (bridge H3) differs by only one 0, and the 0 level has no effect on the mean value. Therefore, when comparing the normalized value (mean value) of the positive half cycle with the threshold value to determine the fault of bridge a, it is impossible to determine whether it is a fault of switch 1 or switch 4. For other bridges, such as bridge H1, the effect of switches 1 and 4 on the output level is different. Therefore, when comparing the normalized value (mean value) of the positive half cycle of bridge H1 with the threshold value to determine the fault of bridge H1, it can be determined whether it is a fault of switch 1 or switch 4 based on the comparison result.

[0088] The same applies to the negative half cycle.

[0089] That is to say, the influence of the switch failure in different H-bridges on the proposed judgment index is as follows: Figure 5 That is, for the target H-bridge unit (bridge a), if M aP = 0, then we can only determine S a1 , S a4 Switch pair fault, such as M aN = 0, then we can only determine S a2 , S a3 Switch pair failure. For other H-bridge units, if M xP = 0, then we can determine that S x1 Switch failure, if M xN = 0, then we can determine that S x2 Switch failure, if M xN >0, then we can determine that S x3 Switch failure, such as M xP <0, then we can judge that S x4 Switch failure.

[0090] In addition, if the target H-bridge unit has an open switch fault, it indicates that the output voltage prediction value calculated using the output voltage prediction value of other H-bridge units is inaccurate, which will affect the diagnosis result of the open switch fault of other H-bridge units.

[0091] If the target H-bridge unit does not have a switch open circuit fault, then in the embodiment of the present invention, the following method can be used to determine whether other H-bridge units except the target H-bridge unit have a fault:

[0092] For each H-bridge unit other than the target H-bridge unit, the following steps are performed: dividing the output voltage average value of the positive half-cycle of the H-bridge unit by the output voltage prediction value of the positive half-cycle to obtain the positive half-cycle normalized value of the H-bridge unit; dividing the output voltage average value of the negative half-cycle of the H-bridge unit by the output voltage prediction value of the negative half-cycle to obtain the negative half-cycle normalized value of the H-bridge unit; and determining whether at least one of the normalized value of the positive half-cycle of the H-bridge unit and the normalized value of the negative half-cycle of the H-bridge unit is less than the low value threshold value, and if so, determining that the H-bridge unit is faulty.

[0093] The normalization processing method of the positive half-cycle normalization value and the negative half-cycle normalization value of each H-bridge unit is the same as the normalization processing method of the target H-bridge unit:

[0094]

[0095]

[0096] The above formula can be used to obtain the normalized value of the positive half cycle of each H bridge except the target H bridge. M xP % and negative half cycle normalized values M xN %.

[0097] If exists M xP %< M th , and / or, M xN %< M th , it indicates that the H-bridge unit has an open-circuit switch fault.

[0098] In the embodiment of the present invention, the faulty switch can also be located for the H-bridge unit with the switch open circuit fault. Specifically, the faulty switch can be determined for the H-bridge unit with the switch fault in the following manner:

[0099] If the normalized value of the positive half cycle of the H-bridge unit is less than the lower threshold, M xP %< M th , then determine S x1 A malfunction occurs;

[0100] If the negative half cycle normalized value of the H-bridge unit is less than the lower threshold, M xN %< M th , then determine S x2 A malfunction occurs;

[0101] Calculate the predicted output voltage of the positive half cycle of the H-bridge unit M xP(ref) The predicted output voltage value of the positive half cycle of the target H-bridge unit M aP(ref) The difference M xP,e , the difference M xP,e The average output voltage of the H-bridge unit in the positive half cycle M xP Do the difference and get the error term of the positive half cycle of the H-bridge unit δ MxP ; If the error term of the positive half cycle of the H-bridge unit δ MxP Less than the error threshold δ Mth , then determine S x4 A malfunction occurs;

[0102] Calculate the predicted output voltage of the negative half cycle of the H-bridge unit M xN(ref) The output voltage prediction value of the negative half cycle of the target H-bridge unit M aN(ref) The difference M xN,e , the difference M xN,e The average output voltage of the negative half cycle of the H-bridge unit M xN Do the difference and get the error term of the negative half cycle of the H-bridge unit δ MxN ; If the error term of the negative half cycle of the H-bridge unit δ MxN Less than the error threshold δ Mth , then determine S x3 A failure occurred.

[0103] It should be noted that the error between the predicted and measured output voltage averages is negligible, so the error threshold δ Mth Less than low threshold M th .

[0104] In the embodiment of the present invention, by calculating the output voltage average value and the output voltage prediction value of each H-bridge unit and comparing and analyzing the two values, it is possible to determine whether a switch open circuit fault occurs in each H-bridge unit. This solution can diagnose whether a switch open circuit fault occurs in each H-bridge unit within one switching cycle, which not only reduces the amount of calculation, but also reduces the control deviation caused by complex signal processing, thereby improving the control accuracy.

[0105] Please refer to Figure 6 The embodiment of the present invention provides a switch open circuit fault determination device for an inverter, wherein the CHB inverter comprises a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the device comprises:

[0106] A collection and calculation unit 600 is used to collect multiple samples of the output voltage of each H-bridge unit in the CHB inverter within a switching cycle, and calculate the output voltage average value of each H-bridge unit according to the collected samples;

[0107] A prediction calculation unit 602, configured to calculate a predicted output voltage value of each H-bridge unit of the CHB inverter in a fault-free state according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit;

[0108] The fault determination unit 604 is used to determine whether a switch open circuit fault occurs in each H-bridge unit according to the ratio of the output voltage average value to the output voltage prediction value of each H-bridge unit.

[0109] In one embodiment of the present invention, the output voltage prediction value is calculated by the following formula:

[0110]

[0111] in, M x(ref) It is the first in the CHB inverter x The predicted output voltage of each H-bridge unit, x =1, 2, …, n ; n is the number of H-bridge units; A, B, and C are coefficients, which can be obtained by looking up the table. x The coefficient value is different when the value is different; M is the modulation ratio; the DC source voltage input to each H-bridge unit is equal and is V dc .

[0112] In one embodiment of the present invention, each H-bridge unit in the CHB inverter includes two complementary switch pairs, the first complementary switch pair is S x1 / S x3 , the second complementary switch pair is S x2 / S x4 ; x Used to characterize the first x H-bridge units;

[0113] When the fault determination unit determines whether a switch open circuit fault occurs in the H-bridge unit, the fault determination unit specifically includes:

[0114] A target H-bridge unit with the longest conduction time among multiple H-bridge units is determined, and it is determined whether a switch open circuit fault occurs in the target H-bridge unit; if a fault occurs, the failed switch in the target H-bridge unit is further determined; if no fault occurs, it is further determined whether other H-bridge units except the target H-bridge unit are faulty.

[0115] In one embodiment of the present invention, the output voltage average value includes the output voltage average value of the positive half cycle and the output voltage average value of the negative half cycle;

[0116] When the fault determination unit determines whether a switch open circuit fault occurs in the target H-bridge unit, the fault determination unit specifically includes:

[0117] The output voltage average value of the positive half cycle of the target H-bridge unit is divided by the output voltage prediction value of the positive half cycle to obtain the positive half cycle normalized value of the target H-bridge unit; the output voltage average value of the negative half cycle of the target H-bridge unit is divided by the output voltage prediction value of the negative half cycle to obtain the negative half cycle normalized value of the target H-bridge unit; determine whether the positive half cycle normalized value of the target H-bridge unit is less than the low value threshold value, if so, then S a1 / S a4 The switch pair fails; the target H-bridge unit is the first a H-bridge unit; determine whether the negative half cycle normalized value of the target H-bridge unit is less than the low value threshold, if so, then S a2 / S a3 A switch pair has failed.

[0118] In one embodiment of the present invention, when the fault determination unit determines whether other H-bridge units except the target H-bridge unit have faults, the fault determination unit specifically includes:

[0119] For each H-bridge unit other than the target H-bridge unit, the following steps are performed: dividing the output voltage average value of the positive half-cycle of the H-bridge unit by the output voltage prediction value of the positive half-cycle to obtain the positive half-cycle normalized value of the H-bridge unit; dividing the output voltage average value of the negative half-cycle of the H-bridge unit by the output voltage prediction value of the negative half-cycle to obtain the negative half-cycle normalized value of the H-bridge unit; and determining whether at least one of the normalized value of the positive half-cycle of the H-bridge unit and the normalized value of the negative half-cycle of the H-bridge unit is less than the low value threshold value, and if so, determining that the H-bridge unit is faulty.

[0120] In one embodiment of the present invention, after determining that the H-bridge unit fails, the fault determination unit is further configured to:

[0121] The faulty switch is determined for the H-bridge unit with the switch fault in the following manner: if the normalized value of the positive half cycle of the H-bridge unit is less than the low value threshold, then S x1 Fault occurs; if the negative half cycle normalized value of the H-bridge unit is less than the low value threshold, it is determined S x2 A fault occurs; Calculate the difference between the output voltage prediction value of the positive half cycle of the H-bridge unit and the output voltage prediction value of the positive half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the positive half cycle of the H-bridge unit to obtain the error term of the positive half cycle of the H-bridge unit; If the error term of the positive half cycle of the H-bridge unit is less than the error threshold, determine S x4 A fault occurs; Calculate the difference between the output voltage prediction value of the negative half cycle of the H-bridge unit and the output voltage prediction value of the negative half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the negative half cycle of the H-bridge unit to obtain the error term of the negative half cycle of the H-bridge unit; If the error term of the negative half cycle of the H-bridge unit is less than the error threshold, determine S x3 A failure occurred.

[0122] It should be noted that: the inverter switch open circuit fault determination device provided in the above embodiment is only illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the inverter switch open circuit fault determination device provided in the above embodiment and the inverter switch open circuit fault determination method embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0123] The embodiment of the present application also provides a computer device, please refer to Figure 7The computer device includes a processor and a memory, in which at least one instruction, at least one program, a code set or an instruction set is stored, and the at least one instruction, at least one program, a code set or an instruction set is loaded and executed by the processor to implement the inverter switch open circuit fault determination method provided by the above-mentioned method embodiments.

[0124] An embodiment of the present application also provides a computer-readable storage medium, on which is stored at least one instruction, at least one program, code set or instruction set, and the at least one instruction, at least one program, code set or instruction set is loaded and executed by a processor to implement the method for determining the open circuit switch fault of the inverter provided in the above-mentioned method embodiments.

[0125] An embodiment of the present application also provides a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium, and the processor executes the computer program, so that the computer device executes the method for determining an open circuit switch fault of an inverter described in any of the above embodiments.

[0126] For the convenience of description, the above system or device is described by dividing it into various modules or units according to its functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0127] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present application or certain parts of the embodiments.

[0128] Finally, it should be noted that, in this article, relational terms such as first, second, third and fourth are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0129] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for determining an open circuit fault of a switch of an inverter, characterized in that: The CHB inverter includes a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the method includes: Collecting multiple samples of the output voltage of each H-bridge unit in the CHB inverter within a switching cycle, and calculating the output voltage average value of each H-bridge unit according to the collected samples; Calculate the output voltage prediction value of each H-bridge unit of the CHB inverter in the absence of a fault according to the modulation ratio selected by the CHB inverter and the DC voltage input to each H-bridge unit; According to the ratio of the output voltage average value of each H-bridge unit to the output voltage prediction value, it is determined whether the H-bridge unit has a switch open circuit fault; Each H-bridge unit in the CHB inverter includes two complementary switch pairs. The first complementary switch pair is S x1 / S x3 , the second complementary switch pair is S x2 / S x4 ; x is used to characterize the xth H-bridge unit in the CHB inverter; The determining whether a switch open circuit fault occurs in the H-bridge unit comprises: determining a target H-bridge unit having the longest conduction time among the multiple H-bridge units, and determining whether a switch open circuit fault occurs in the target H-bridge unit; if a fault occurs, further determining a switch in the target H-bridge unit that has a fault; if no fault occurs, further determining whether other H-bridge units except the target H-bridge unit have a fault; The output voltage average value includes the output voltage average value of the positive half cycle and the output voltage average value of the negative half cycle; the determination of whether the target H-bridge unit has a switch open circuit fault includes: dividing the output voltage average value of the positive half cycle of the target H-bridge unit by the output voltage prediction value of the positive half cycle to obtain the positive half cycle normalized value of the target H-bridge unit; dividing the output voltage average value of the negative half cycle of the target H-bridge unit by the output voltage prediction value of the negative half cycle to obtain the negative half cycle normalized value of the target H-bridge unit; judging whether the positive half cycle normalized value of the target H-bridge unit is less than the low value threshold value, if so, S a1 / S a4 The switch pair fails; the target H-bridge unit is the ath H-bridge unit in the CHB inverter; it is determined whether the negative half-cycle normalized value of the target H-bridge unit is less than the low value threshold, if so, S a2 / S a3 The switch pair fails; The determining whether other H-bridge units except the target H-bridge unit fail comprises: For each H-bridge unit other than the target H-bridge unit, the following steps are performed: dividing the average output voltage of the positive half cycle of the H-bridge unit by the predicted output voltage of the positive half cycle to obtain the normalized value of the positive half cycle of the H-bridge unit; dividing the average output voltage of the negative half cycle of the H-bridge unit by the predicted output voltage of the negative half cycle to obtain the normalized value of the negative half cycle of the H-bridge unit; judging whether at least one of the normalized value of the positive half cycle of the H-bridge unit and the normalized value of the negative half cycle of the H-bridge unit is less than the low value threshold value, and if so, determining that the H-bridge unit fails; After determining that the H-bridge unit fails, the method further includes: determining a failed switch for the H-bridge unit where the switch failure occurs in the following manner: If the normalized value of the positive half cycle of the H-bridge unit is less than the lower threshold, then determine S x1 Fault occurs; if the negative half cycle normalized value of the H-bridge unit is less than the low value threshold, then determine S x2 A fault occurs; Calculate the difference between the output voltage prediction value of the positive half cycle of the H-bridge unit and the output voltage prediction value of the positive half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the positive half cycle of the H-bridge unit to obtain the error term of the positive half cycle of the H-bridge unit; If the error term of the positive half cycle of the H-bridge unit is less than the error threshold, determine S x4 A fault occurs; Calculate the difference between the output voltage prediction value of the negative half cycle of the H-bridge unit and the output voltage prediction value of the negative half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the negative half cycle of the H-bridge unit to obtain the error term of the negative half cycle of the H-bridge unit; If the error term of the negative half cycle of the H-bridge unit is less than the error threshold, determine S x3 A failure occurred.

2. The method according to claim 1, characterized in that The output voltage prediction value is calculated by the following formula: M x(ref) =[A(M) 2 +B(M) 2 +C]×V dc Among them, M x(ref) is the output voltage prediction value of the xth H-bridge unit in the CHB inverter, x = 1, 2, ..., n; n is the number of H-bridge units; A, B, C are coefficients, which can be obtained by looking up the table. When x is different, the coefficient value is also different; M is the modulation ratio; the DC source voltage input to each H-bridge unit is equal and is V dc .

3. A device for determining an open circuit fault of a switch of an inverter, characterized in that: The CHB inverter includes a plurality of H-bridge units connected in series, and the CHB inverter is used to convert an input DC voltage into an AC voltage output; the device includes: A collection and calculation unit, used for collecting a plurality of samples of the output voltage within a switching cycle for each H-bridge unit in the CHB inverter, and calculating the output voltage average value of each H-bridge unit according to the collected samples; A prediction calculation unit, used to calculate the output voltage prediction value of each H-bridge unit of the CHB inverter in a fault-free state according to the modulation ratio selected by the CHB inverter and the DC voltage respectively input to each H-bridge unit; A fault determination unit, used to determine whether a switch open circuit fault occurs in each H-bridge unit according to a ratio of an output voltage average value to an output voltage prediction value of each H-bridge unit; Each H-bridge unit in the CHB inverter includes two complementary switch pairs. The first complementary switch pair is S x1 / S x3 , the second complementary switch pair is S x2 / S x4 ; x is used to characterize the xth H-bridge unit in the CHB inverter; When determining whether a switch open circuit fault occurs in an H-bridge unit, the fault determination unit specifically includes: determining a target H-bridge unit with the longest conduction time among a plurality of H-bridge units, and determining whether a switch open circuit fault occurs in the target H-bridge unit; if a fault occurs, further determining a switch in the target H-bridge unit that has a fault; if no fault occurs, further determining whether other H-bridge units except the target H-bridge unit have a fault; The output voltage average value includes the output voltage average value of the positive half cycle and the output voltage average value of the negative half cycle; when the fault judgment unit judges whether the target H-bridge unit has a switch open circuit fault, the fault judgment unit specifically includes: dividing the output voltage average value of the positive half cycle of the target H-bridge unit by the output voltage prediction value of the positive half cycle to obtain the positive half cycle normalized value of the target H-bridge unit; dividing the output voltage average value of the negative half cycle of the target H-bridge unit by the output voltage prediction value of the negative half cycle to obtain the negative half cycle normalized value of the target H-bridge unit; judging whether the positive half cycle normalized value of the target H-bridge unit is less than the low value threshold value, if so, S a1 / S a4 The switch pair fails; the target H-bridge unit is the ath H-bridge unit in the CHB inverter; it is determined whether the negative half-cycle normalized value of the target H-bridge unit is less than the low value threshold, if so, S a2 / S a3 The switch pair fails; When the fault determination unit determines whether other H-bridge units except the target H-bridge unit have faults, the fault determination unit specifically includes: For each H-bridge unit other than the target H-bridge unit, the following steps are performed: dividing the average output voltage of the positive half cycle of the H-bridge unit by the predicted output voltage of the positive half cycle to obtain the normalized value of the positive half cycle of the H-bridge unit; dividing the average output voltage of the negative half cycle of the H-bridge unit by the predicted output voltage of the negative half cycle to obtain the normalized value of the negative half cycle of the H-bridge unit; judging whether at least one of the normalized value of the positive half cycle of the H-bridge unit and the normalized value of the negative half cycle of the H-bridge unit is less than the low value threshold value, and if so, determining that the H-bridge unit fails; After determining that the H-bridge unit has a fault, the fault determination unit is further configured to: determine a faulty switch for the H-bridge unit having a switch fault by: If the normalized value of the positive half cycle of the H-bridge unit is less than the lower threshold, then determine S x1 Fault occurs; if the negative half cycle normalized value of the H-bridge unit is less than the low value threshold, then determine S x2 A fault occurs; Calculate the difference between the output voltage prediction value of the positive half cycle of the H-bridge unit and the output voltage prediction value of the positive half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the positive half cycle of the H-bridge unit to obtain the error term of the positive half cycle of the H-bridge unit; If the error term of the positive half cycle of the H-bridge unit is less than the error threshold, determine S x4 A fault occurs; Calculate the difference between the output voltage prediction value of the negative half cycle of the H-bridge unit and the output voltage prediction value of the negative half cycle of the target H-bridge unit, and subtract the difference from the average output voltage of the negative half cycle of the H-bridge unit to obtain the error term of the negative half cycle of the H-bridge unit; If the error term of the negative half cycle of the H-bridge unit is less than the error threshold, determine S x3 A failure occurred.

4. The device according to claim 3, characterized in that The output voltage prediction value is calculated by the following formula: M x(ref) =[A(M) 2 +B(M) 2 +C]×V dc Among them, M x(ref) is the output voltage prediction value of the xth H-bridge unit in the CHB inverter, x = 1, 2, ..., n; n is the number of H-bridge units; A, B, C are coefficients, which can be obtained by looking up the table. When x is different, the coefficient value is also different; M is the modulation ratio; the DC source voltage input to each H-bridge unit is equal and is V dc .

5. A computer device, characterized in that: The computer device includes a memory and a processor, the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to implement the steps of any of the methods described in claims 1-2 above.

6. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any one of claims 1 to 2 are implemented.

7. A computer program product, characterized in that The method comprises a computer program, which, when executed by a processor, implements the steps of the method according to any one of claims 1 to 2.

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