CN117434487B - Fault diagnosis method based on current imbalance and duty cycle imbalance - Google Patents
Fault diagnosis method based on current imbalance and duty cycle imbalance Download PDFInfo
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Abstract
The invention belongs to the technical field of power electronics, and particularly discloses a fault diagnosis method based on current imbalance and duty cycle imbalance, which comprises the following steps: s110, collecting current value data of bridge arms according to preset periods, and setting current values of N bridge arms in a circuit collected once every T periods; s120, selecting different fault judging modes according to a preset mode, and selecting a current imbalance judging method and/or a duty ratio imbalance judging method according to the current value in the step S110; s130, setting fault conditions, and setting different fault conditions according to the selected fault judgment mode in the step S120; and S140, performing fault judgment, and performing fault judgment according to different fault conditions set in the step S130 to obtain a specific fault result. The method and the device improve the diagnosis accuracy of faults in aspects of abnormal power supply, sampling faults and the like of the current sensor, prevent serious damage, facilitate timely taking of protective measures and improve the safety of the DC-DC controller system.
Description
Technical Field
The disclosure relates to the technical field of power electronics, in particular to a fault diagnosis method based on current imbalance and duty cycle imbalance.
Background
In a normal state, the current of each bridge arm of the DC-DC controller is equal, so when a certain current sensor of the DC-DC controller fails, a situation that the sampling value of the current sensor deviates from the actual value occurs. In this case, in order to make the target bridge arm current converge to the desired value, the DC-DC controller may adjust the duty cycle of the target bridge arm MOS transistor control signal PWM, thereby causing an increase in risk of bridge arm hardware overcurrent and MOS transistor explosion. Meanwhile, the fault diagnosis of the current sensor of the existing DC-DC controller generally adopts a mode of setting a fault threshold value, and when the acquired current sampling value is higher or lower than a certain threshold value, the fault of the sensor is judged. However, setting the threshold value reduces the utilization of the current sensor range, and limits the operating mode of the DC-DC controller. And the method can not detect the fault of inaccurate current sampling caused by abnormal power supply of the current sensor. Therefore, in such an environment, it is necessary to diagnose the failure of the current sensor quickly and timely, so as to stop the machine in time, avoid the occurrence of more serious problems, and avoid threatening the safety of the DC-DC controller system.
The investigation and publication (public)No.) number: CN103744013B discloses a fault diagnosis method for a fully-controlled bridge circuit, which outputs complementary PWM driving signals to two power switching tubes of any bridge arm of the fully-controlled bridge circuit, and simultaneously turns off the power switching tubes of all the other bridge arms of the fully-controlled bridge circuit; detecting the actual output voltage U of the bridge arm x The current i of the full-control bridge circuit dc The method comprises the steps of carrying out a first treatment on the surface of the Based on the detected actual output voltage U x And current i dc Judging whether the two power switch tubes of the bridge arm have faults or not; and performing fault diagnosis on the power switch tubes of the rest bridge arms of the full-control bridge circuit according to the steps. The fault detection is carried out by adopting different states of voltage and current, the detection content during fault detection is increased, a plurality of unknowns are selected for comparison, the actual accuracy of a diagnosis result cannot be ensured, and the fault detection method is inconvenient to popularize and apply and has limitation in other types of circuits.
Disclosure of Invention
The present disclosure proposes a fault diagnosis method based on current imbalance and duty cycle imbalance to solve the above-mentioned problems.
The present disclosure provides a fault diagnosis method based on current imbalance and duty cycle imbalance, comprising the steps of:
s110, collecting current value data of bridge arms according to periods, setting current values of N bridge arms in a circuit collected once every T periods, setting N current sensors in the T periods to be respectively and correspondingly connected with N bridge arms in a target circuit, collecting current values of inductors arranged on the N bridge arms, recording the current values, and setting a control circuit to collect duty ratios of the N bridge arms;
s120, selecting different fault judging modes according to a preset mode, and selecting a current imbalance judging method and/or a duty ratio imbalance judging method according to the current value and the judging condition in the step S110;
the judging conditions are as follows: when the current value of any bridge arm deviates from the current values of other bridge arms, the current imbalance is judged; when the duty ratio of any bridge arm deviates from the duty ratios of other bridge arms, the duty ratio is determined to be unbalanced;
s130, setting fault conditions, and setting different fault conditions according to the selected fault judgment mode in the step S120; when the current is unbalanced, separating a current maximum value and a current minimum value, calculating an average value of the residual current values, and setting a current unbalanced proportional coefficient and a current unbalanced offset proportional coefficient according to the average value; when the duty ratio is unbalanced, separating a maximum duty ratio value and a minimum duty ratio value, calculating a residual duty ratio average value, and setting a duty ratio unbalanced proportional coefficient and a duty ratio unbalanced offset coefficient according to the average value;
s140, performing fault judgment, comparing the maximum value and the minimum value of the separated current with the unbalanced fault judgment conditions of the current according to the different fault conditions set in the step S130, and comparing the maximum duty cycle and the minimum duty cycle of the separation with the unbalanced fault judgment conditions of the duty cycle to obtain a specific fault result;
and after the fault result is obtained, completing the fault diagnosis, wherein the fault diagnosis is the fault diagnosis in each period.
Preferably, in the step S110, sampling currents of collecting N current sensors are set to i n (n=1, 2, … N); setting the duty ratio of MOS tube PWN control signals of N bridge arms collected by a control circuit as d n (n=1,2,…N)。
Preferably, in the step S130, the sampling current i is measured n (n=1, 2, … N) to be arranged as I n (n=1, 2, … N) and recording the sampling current minimum I 1 Is the current sensor number N Imin And a current maximum I N Is the current sensor number N Imax ；
For the duty cycle d n (n=1, 2, … N) to be arranged as D n (n=1, 2, … N), and recording the minimum duty cycle D 1 The serial number of the current sensor of the bridge arm is N Dmin And a maximum duty cycle D N The serial number of the current sensor of the bridge arm is N Dmax 。
Preferably, in the step 130, one-to-one fault conditions are set according to different judging methods;
setting the calculation current I when the current is unbalanced 2 ~ I N-1 Setting the average value of the current I 2 ~ I N-1 Average value of I Avg According to I Avg The value setting fault diagnosis current imbalance proportionality coefficient includes k IL And k IH The method comprises the steps of carrying out a first treatment on the surface of the According to I Avg The value setting fault diagnosis current unbalance offset coefficient includes b IL And b IH ;
Wherein k is IH Is the current upper bias proportion coefficient, and the value range is k IH >1；k IL Is a current downward bias proportion coefficient, and has a value range of 1>k IL >0；b IH Is the current upward deflection coefficient, and the value range is b IH >0；b IL Is a current declination coefficient, and has a value range of b IL >0。
Preferably, the duty cycle D is calculated from the duty cycle imbalance 2 ~D N-1 Setting the duty ratio D 2 ~D N-1 Average value of D Avg According to D Avg The value setting fault diagnosis duty cycle imbalance proportionality coefficient comprises k DL And k DH And the duty cycle imbalance offset coefficient includes b DL And b DH ；
Wherein k is DH Is the upper deviation proportion coefficient of the duty ratio, and the value range is k DH >1；k DL Is a duty ratio lower deviation proportion coefficient, and has a value range of 1>k DL >0；b DH Is the upper bias coefficient of duty ratio, and the value range is b DH >0；b DL Is a duty cycle downshifting coefficient, and has a value range of b DL >0。
Preferably, in the step S140, the current imbalance fault determination condition is: when meeting I 1 <I Avg ×k IL -b IL Condition, the current sensor N is identified Imin A fault; when meeting I N >I Avg ×k IH +b IH Condition, the current sensor N is identified Imax And (3) failure.
Preferably, in the step S140, the duty ratio imbalance fault determination condition is: when meeting D 1 <D Avg ×k DL -b DL Condition, the current sensor N is identified Dmin A fault; when meeting D N >D Avg ×k DH +b DH Condition, the current sensor N is identified Dmax And (3) failure.
Compared with the prior art, the fault diagnosis method based on current imbalance and duty cycle imbalance has the beneficial effects that: according to the fault diagnosis method based on the current imbalance and the duty ratio imbalance, the current values of all bridge arms are obtained in time, the current values among the bridge arms can be analyzed and judged in time, and the diagnosis accuracy of faults in the aspects of abnormal power supply, sampling faults and the like of the current sensor can be improved; the type and the reason of the fault are timely judged according to the state of the actual bridge arm, and shutdown protection measures can be adopted for the DC-DC controller after the fault is detected, so that the safety of the DC-DC controller system is improved, and the equipment damage rate and the maintenance and repair cost are reduced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description, serve to explain the technical aspects of the disclosure.
FIG. 1 shows a schematic diagram of a configuration of a multi-leg parallel DC-DC controller of the present disclosure;
FIG. 2 illustrates a flow chart of a fault diagnosis method of the present disclosure based on current imbalance and duty cycle imbalance;
FIG. 3 illustrates a fault diagnosis flow chart based on current imbalance and duty cycle imbalance of an embodiment of the present disclosure.
Description of the drawings: 1-DC input voltage; 2-inductance; 3-MOS tube; a 4-DC-DC output voltage; a 5-current sensor; 6-power supply; 7-a driving circuit; 8-control circuitry.
Detailed Description
Various exemplary embodiments, features and aspects of the disclosure will be described in detail below with reference to the drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
The term "and/or" is herein merely an association relationship describing an associated object, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the term "at least one" herein means any one of a plurality or any combination of at least two of a plurality, for example, including at least one of A, B, C, and may mean including any one or more elements selected from the group consisting of A, B and C.
Furthermore, numerous specific details are set forth in the following detailed description in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements, and circuits well known to those skilled in the art have not been described in detail in order not to obscure the present disclosure.
It will be appreciated that the above-mentioned method embodiments of the present disclosure may be combined with each other to form a combined embodiment without departing from the principle logic, and are limited to the description of the present disclosure.
In the normal operation state, the current passing through each bridge arm of the DC-DC controller is equal, so that the normal operation is maintained. However, when a certain current sensor fails, the sampling value of the current sensor deviates from the true value, which affects the subsequent use. However, in the practical application process, the possibility that a plurality of bridge arms of the DC-DC controller simultaneously fail is extremely low. And the current imbalance and duty cycle imbalance are handled differently. Therefore, when a certain bridge arm current of the DC-DC controller at a certain time is significantly deviated from other bridge arm currents, the current is unbalanced. And when the duty ratio of the PWM signal of the MOS tube of one bridge arm of the DC-DC controller at a certain moment is obviously deviated from the duty ratios of other bridge arms, the duty ratio is unbalanced at the moment. Based on the above situation, the present disclosure proposes a fault diagnosis method based on current imbalance and duty cycle imbalance, specifically, as shown in fig. 1,2 and 3, including the following steps: s110, collecting current value data of bridge arms according to periods, and setting current values of N bridge arms in a circuit collected once every T periods; s120, selecting different fault judging modes according to a preset mode, and selecting a current imbalance judging method and/or a duty ratio imbalance judging method according to the current value in the step S110; s130, setting fault conditions, and setting different fault conditions according to the selected fault judgment mode in the step S120; and S140, performing fault judgment, and performing fault judgment according to different fault conditions set in the step S130 to obtain a specific fault result.
Specifically, as shown in fig. 1 and 3, first, a data acquisition operation is performed by using a plurality of current sensors 5 in a period T, that is, current values of the inductors 2 on all bridge arms in the circuit are respectively acquired, and at this time, the DC-DC input voltage 1 and the DC-DC output voltage 4 maintain normal operation of the target circuit. And then carrying out data processing and analysis to obtain the current values of the inductors 2 of all bridge arms, and then starting to process and analyze the current value data, such as: the control circuit 8 is used to perform the current imbalance diagnosis and the duty imbalance diagnosis of the current sensor 5 in the T period, and analyze whether the current value satisfies the current imbalance condition or satisfies the duty imbalance condition. When the current sensor 5 of one bridge arm fails or the power supply 6 is abnormal, the current sampling value deviates from the current values of other bridge arms, and the current is determined to be unbalanced. When the control circuit 8 monitors that the current value of the fault bridge arm deviates from the expected value, the duty ratio of the bridge arm control signal PWM is adjusted, and the on time of the MOS transistor 3 is changed by the driving circuit 7, so that the error between the sampling current and the expected current of the bridge arm is expected to be reduced, the duty ratio of the bridge arm deviates from the duty ratios of other bridge arms, and the bridge arm is determined as unbalanced duty ratio. After the data processing and analysis are carried out, the fault condition setting is started, and when the current value meets the two conditions, the fault condition is set according to the specific condition corresponding to the current value. And when the fault condition is met, fault judgment can be performed, the specific fault position is confirmed, and the fault is conveniently and rapidly judged and timely processed. If the current value data acquired in the period does not meet the conditions, the data acquisition and the new analysis and judgment operation of the next period are performed, the cycle is performed, the fault diagnosis is completed after the fault result is obtained, and the fault diagnosis is the fault diagnosis in each period.
In the embodiment of the present disclosure, as shown in fig. 1 and 2, the circuit is divided into a topology structure part including constituent elements in the target circuit and a control and drive circuit part including a current sensor 5 and a power supply 6, a drive circuit 7 and a control circuit 8 in fig. 1. In topology V in For voltage input, V out For voltage output, the current passing through each component element in the topology structure, that is, the same current will pass through each bridge arm, the current sensor 5 and the control circuit 8 are set to collect the current values and duty ratios of the N bridge arms in the target circuit respectively. And recording the acquired current value and duty cycle. Specifically, the current sensor 5 is used to connect N bridge arms in the target circuit in the T period, collect current values of the inductors 2 set on the N bridge arms, record the current values, and set the sampling current of the N current sensors 5 as i n (n=1, 2, … N). Setting the duty ratio of the control circuit 8 for collecting N bridge arms and the duty ratio of the MOS tube 3PWN control signals of the N bridge arms as d n (n=1,2,…N)。
And then, carrying out subsequent judgment operation on the current value in the T period according to judgment conditions on the current value which is recorded. Judging the current imbalance when the current value of any bridge arm deviates from the current values of other bridge arms; when the current value of any one of the bridge arms deviates from the expected value, it is determined that the duty ratio is unbalanced. Therefore, specific fault conditions can be accurately mastered, and the subsequent rapid obtaining of fault results is facilitated.
In the embodiment of the present disclosure, as shown in fig. 1 and 2, for subsequent setting of fault conditions according to specific fault types, the collected current values and the duty cycles are first sorted. Specifically, for the sampling current i n (n=1, 2, … N) to be arranged as I n (n=1, 2, … N) and recording the sampling current minimum I 1 Is the current sensor number N Imin And a current maximum I N Is the current sensor number N Imax . This is because, during actual operation, the current sensor N Imin And N Imax The sampled current deviates to the greatest extent, which is likely to be faulty. Since the two sensors have a possibility of failure, it is considered that the value having the greatest degree of deviation of the current has a possibility of failure in order to avoid affecting the judgment result. Similarly, the duty cycle values are sorted and sorted in the same way, and the duty cycle d is calculated n (n=1, 2, … N) to be arranged as D n (n=1, 2, … N), and recording the minimum duty cycle D 1 The serial number of the current sensor of the bridge arm is N Dmin And a maximum duty cycle D N The serial number of the current sensor of the bridge arm is N Dmax . Likewise, the current sensor N is identified Dmin And N Dmax The duty cycle of the bridge arm is deviated to the greatest extent, so that the two sensors have the possibility of faults.
In this embodiment, since the current value data has been sorted in the period T to strip out the value that may have a fault, the subsequent confirmation operation is facilitated to be continued. Therefore, the diagnosis accuracy of faults in the aspects of abnormal power supply, sampling faults and the like of the current sensor 5 is improved, and shutdown protection measures are timely taken for the DC-DC controller after the faults are detected, so that the safety of the DC-DC controller system is improved.
After the fault judging mode is selected and accurate and tidied current value data are obtained, the fault judging mode can be selected according toThe corresponding fault condition is further calculated. Specifically, as shown in fig. 1 and 2, since the sampling current minimum value I has been removed from the current value of the current imbalance in the previous step 1 And a sampling current maximum value I N Thus, when performing the current imbalance diagnosis, first, the current I is calculated 2 ~ I N-1 And set the current I 2 ~ I N-1 Average value of I Avg . Next, according to I Avg The value of (2) is set to be k respectively as the unbalanced proportionality coefficient of fault diagnosis current IL And k IH . Wherein k is IH Setting the value range of the current upper bias proportion coefficient as k IH >1；k IL For the current deviation proportion coefficient, the value range is 1>k IL >0；b IH Setting the value range of the current upward deflection coefficient as b IH >0；b IL Setting the value range of the current declination coefficient as b IL >0. The current detected by the current sensor 5 is an inductive current, the MOS tube 3 is switched on and off to generate inductive current pulsation when the inductor is charged and discharged, and the switching time sequence of the MOS tubes 3 of different bridge arms is different, so that the inductive current of different bridge arms has deviation, and the current deviation coefficient b is set IL And current bias coefficient b IH To eliminate the lower and upper limits of the deviation of the different bridge arm currents themselves. With the increase of the control input current, the current pulsation of different bridge arm inductances can be increased, so that the current deviation of different bridge arms can be increased, and the current deviation proportion coefficient k is set IL And current upper bias scaling coefficient k IH To eliminate the lower and upper limits of the control current variation on the bridge arm current deviation.
Likewise, the minimum duty cycle D has been removed when the duty cycle imbalance diagnosis is made 1 And a maximum duty cycle D N Therefore, only the duty ratio D is calculated when the duty ratio imbalance diagnosis is performed 2 ~ D N-1 And set the duty ratio D 2 ~ D N-1 Average value of D Avg According to D Avg The value of the set fault diagnosis duty ratio imbalance proportion coefficient is k DL And k DH And a duty cycle imbalance offset coefficientB is respectively DL And b DH . Wherein k is DH Setting the value range of the duty ratio upper deviation proportion coefficient as k DH >1；k DL Setting the value range of the duty ratio lower deviation proportion coefficient to be 1>k DL >0；b DH Setting the value range of the duty ratio upper bias coefficient as b DH >0；b DL Setting the value range of the duty ratio downshifting coefficient as b DL >0. Since the duty ratio changes with the current, it is also necessary to increase the duty ratio imbalance ratio, duty ratio downshifting ratio k DL And duty cycle upper bias scaling factor k DH And duty cycle downshifting coefficient b DL And duty cycle up-shift coefficient b DH So as to eliminate the deviation of the duty cycle of the controller and avoid fault judgment errors.
In a specific embodiment, the current detected by the current sensor 5 is an inductor current, when the system works, the inductor 2 is periodically charged and discharged along with the on-off of the MOS transistor 3, the charging increases the current of the inductor 2, and the discharging decreases the current of the inductor 2, so that the inductor current itself has periodic pulsation. Taking a BOOST topology controller as an example, the inductance fluctuation can be expressed as:
wherein,v is the fluctuation of inductance current in Is DC-DC input voltage, L is inductance value, d is duty ratio of MOS tube 3, T PWM Is the time period of PWM.
The phase difference is set at the time sequence of the on-off of the plurality of bridge arm MOS tubes 3 of the DC-DC controller, so that N bridge arm inductors can be prevented from simultaneously charging and discharging to increase current pulsation to NBut can lead to the maximum existence of different bridge arm inductance currents at the same time>Thus the current imbalance offset factor setting is required to satisfy b IL ≥/>And b IH ≥/>The current imbalance offset coefficient is set in this embodiment as follows:
wherein I is err The compensation of the current unbalance coefficient is carried out by considering the factors such as the sampling precision of the current sensor, the external interference and the like, I err Is set according to the system characteristics and engineering experience.
The DC-DC controller works in a dynamic regulation process, is influenced by factors such as the switching frequency of the MOS tube 3, a controller algorithm, hardware conditions and the like, the current control precision of a bridge arm of the DC-DC controller is limited, the actual value of the inductor current fluctuates around the expected value of the inductor current, the current fluctuation degree is positively related to the magnitude of the input current, and therefore the unbalanced current proportionality coefficient k is introduced IL And k IH If the current control precision error of the DC-DC controller system is + -e i (0<e i <1) Then the current imbalance scaling factor is:
k IL =1-e i , k IH =1+e i
the DC-DC controller calculates the duty ratio according to the deviation between the expected value and the actual value of the inductance current, and the calculated duty ratio also has a fluctuation range d because the deviation of the inductance current is caused by the fluctuation of the inductance current L ~d H The duty cycle imbalance offset factor is then:
when the charge and discharge of the inductance current do not reach the balance, the larger the duty ratio of the MOS tube 3 is, the input of the MOS tube isThe greater the duty cycle fluctuation degree caused by the current command change, namely the duty cycle fluctuation degree is positively correlated with the average duty cycle, the duty cycle imbalance proportionality coefficient k is introduced DL 、k DH The coefficient value can be obtained by fitting the DC-DC controller under different working conditions according to the fluctuation range of the duty ratio.
When the specific values in the two judging modes respectively meet the conditions, the final fault judgment can be correspondingly carried out, and an accurate judging result is obtained. Namely: when the bridge arm current value of the current unbalance is determined to be 1>k IL >0，k IH >1，b IL >0 and b IH >0, when meeting the condition I 1 <I Avg ×k IL -b IL Condition, identify current sensor N Imin Failure or meet I N >I Avg ×k IH +b IH Condition, identify current sensor N Imax Fault, identifying current sensor N Imax And (3) failure. Therefore, a specific fault position in the state of unbalanced current can be obtained, shutdown protection measures can be timely adopted for the DC-DC controller, and the conditions of equipment damage and the like are avoided. When the bridge arm current with unbalanced duty ratio is determined to be 1>k DL >0，k DH >1，b DL >0 and b DH >When condition 0 is satisfied D 1 <D Avg ×k DL -b DL Condition, identify current sensor N Dmin A fault; or satisfy D N >D Avg ×k DH +b DH Condition, identify current sensor N Dmax And (3) failure.
In this embodiment, since the possibility of simultaneous failure of multiple legs of the DC-DC controller is extremely low, it may be considered an impossible event, and thus, when the current of one leg of the DC-DC controller deviates significantly from the current of the other legs at a certain time, it is considered that the current is unbalanced. When the duty ratio of the PWM signal of the MOS tube 3 of one bridge arm of the DC-DC controller at a certain moment is obviously deviated from the duty ratios of other bridge arms, the unbalanced duty ratio is considered. When at least one of the current imbalance and the duty cycle imbalance occurs, it can be determined that the current sensor 5 is malfunctioning. The judging method of the present disclosure does not reduce the utilization rate of the mileage of the current sensor, and does not limit the working condition of the DC-DC controller. In addition, the method and the device acquire the actual current values of the bridge arms in the period, so that the judging result is more accurate, the machine can be stopped in time, the situation that the DC-DC controller is seriously damaged is avoided, and the safety of the DC-DC controller system is improved.
The foregoing description of the embodiments of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvement of the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (7)
1. A fault diagnosis method based on current imbalance and duty cycle imbalance, comprising the steps of:
s110, collecting current value data of bridge arms according to periods, setting current values of N bridge arms in a circuit collected once every T periods, setting N current sensors in the T periods to be respectively and correspondingly connected with N bridge arms in a target circuit, collecting current values of inductors arranged on the N bridge arms, recording the current values, and setting a control circuit to collect duty ratios of the N bridge arms;
s120, selecting different fault judging modes according to a preset mode, and selecting a current imbalance judging method and/or a duty ratio imbalance judging method according to the current value and the judging condition in the step S110;
the judging conditions are as follows: when the current value of any bridge arm deviates from the current values of other bridge arms, the current imbalance is judged; when the duty ratio of any bridge arm deviates from the duty ratios of other bridge arms, the duty ratio is determined to be unbalanced;
s130, setting fault conditions, and setting different fault conditions according to the selected fault judgment mode in the step S120; when the current is unbalanced, separating a current maximum value and a current minimum value, calculating an average value of the residual current values, and setting a current unbalanced proportional coefficient and a current unbalanced offset proportional coefficient according to the average value; when the duty ratio is unbalanced, separating a maximum duty ratio value and a minimum duty ratio value, calculating a residual duty ratio average value, and setting a duty ratio unbalanced proportional coefficient and a duty ratio unbalanced offset coefficient according to the average value;
s140, performing fault judgment, comparing the maximum value and the minimum value of the separated current with the unbalanced fault judgment conditions of the current according to the different fault conditions set in the step S130, and comparing the maximum duty cycle and the minimum duty cycle of the separation with the unbalanced fault judgment conditions of the duty cycle to obtain a specific fault result;
and after the fault result is obtained, completing the fault diagnosis, wherein the fault diagnosis is the fault diagnosis in each period.
2. The method for diagnosing a fault based on current imbalance and duty cycle imbalance according to claim 1, wherein in said step S110, sampling currents of collecting N of said current sensors are set to i n The method comprises the steps of carrying out a first treatment on the surface of the Setting the duty ratio of MOS tube PWN control signals of N bridge arms collected by a control circuit as d n 。
3. The fault diagnosis method based on current unbalance and duty cycle unbalance according to claim 2, characterized in that in the step S130, the sampling current i is n Ascending order is carried out, and the arrangement is I n And record the minimum value I of the sampling current 1 Is the current sensor number N Imin And a current maximum I N Is the current sensor number N Imax ；
For the duty cycle d n Ascending order is carried out to arrange as D n And record the minimum duty ratio D 1 The serial number of the current sensor of the bridge arm is N Dmin And a maximum duty cycle D N The electric of the bridge armStream sensor number N Dmax 。
4. The fault diagnosis method based on current imbalance and duty cycle imbalance according to claim 3, wherein in the step 130, one-to-one fault conditions are set according to different judging methods;
setting the calculation current I when the current is unbalanced 2 ~ I N-1 Setting the average value of the current I 2 ~ I N-1 Average value of I Avg According to I Avg The value setting fault diagnosis current imbalance proportionality coefficient includes k IL And k IH The method comprises the steps of carrying out a first treatment on the surface of the According to I Avg The value setting fault diagnosis current unbalance offset coefficient includes b IL And b IH ;
Wherein k is IH Is the current upper bias proportion coefficient, and the value range is k IH >1；k IL Is a current downward bias proportion coefficient, and has a value range of 1>k IL >0；b IH Is the current upward deflection coefficient, and the value range is b IH >0；b IL Is a current declination coefficient, and has a value range of b IL >0。
5. The fault diagnosis method based on current imbalance and duty cycle imbalance according to claim 4, wherein duty cycle D is calculated based on duty cycle imbalance condition 2 ~ D N-1 Setting the duty ratio D 2 ~ D N-1 Average value of D Avg According to D Avg The value setting fault diagnosis duty cycle imbalance proportionality coefficient comprises k DL And k DH And the duty cycle imbalance offset coefficient includes b DL And b DH ；
Wherein k is DH Is the upper deviation proportion coefficient of the duty ratio, and the value range is k DH >1；k DL Is a duty ratio lower deviation proportion coefficient, and has a value range of 1>k DL >0；b DH Is the upper bias coefficient of duty ratio, and the value range is b DH >0；b DL Is a duty cycle downshifting coefficient, and has a value range of b DL >0。
6. The method according to claim 5, wherein in step S140, the current imbalance fault determination condition is: when meeting I 1 <I Avg ×k IL -b IL Condition, the current sensor N is identified Imin A fault; when meeting I N >I Avg ×k IH +b IH Condition, the current sensor N is identified Imax And (3) failure.
7. The method according to claim 6, wherein in step S140, the duty cycle imbalance fault determination condition is: when meeting D 1 <D Avg ×k DL -b DL Condition, the current sensor N is identified Dmin A fault; when meeting D N >D Avg ×k DH +b DH Condition, the current sensor N is identified Dmax And (3) failure.
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