CN112285607B - Single-tube open-circuit fault diagnosis method of open-winding electric drive system based on predictive control - Google Patents

Abstract

The invention discloses a single-tube open-circuit fault diagnosis method of an open-winding electric drive system based on predictive control, which utilizes the characteristic that the switching state of model predictive control is determined and unchanged in each control period to obtain the estimated voltage of each phase according to the predicted switching state; comparing the difference value of the estimated voltage and the actually measured voltage with a given threshold value, and judging possible fault phases and fault switch pairs; in order to eliminate the influence of switching process and measurement noise, the fault phase error voltage is integrated over a certain time length and compared with another threshold value to determine the occurrence of fault; and constructing a diagnosis function according to the relation between the fault phase bridge arm switching signal and the error voltage, and diagnosing the specific switching tube with the open-circuit fault. The method is simple and effective, can realize fault diagnosis in a short time, positions the fault switch tube to a specific fault, is not easily influenced by system operation disturbance in the diagnosis process, and has high reliability.

Description

Single-tube open-circuit fault diagnosis method of open-winding electric drive system based on predictive control

Technical Field

The invention relates to the technical field of single-tube open-circuit fault diagnosis of an open-winding electric drive system, in particular to a single-tube open-circuit fault diagnosis method of the open-winding electric drive system based on predictive control.

Background

The open winding motor is a novel motor, has the advantages of three-phase independent control, high output power, large rotating speed range and the like, and is a research hotspot in the field of electric drive of electric vehicles. The operation reliability of the open-winding electric drive system is directly related to the safety performance of the whole vehicle and the personal safety of personnel, and the power switch device is a weak link which is easy to break down. The research on the corresponding fault diagnosis scheme and the fault-tolerant control strategy of the electric drive system is of great significance.

For power devices of electric drive systems, when a short-circuit fault occurs, a fast fuse is usually used to convert the short-circuit fault into an open-circuit fault, and an open-circuit diagnosis method is used to process the short-circuit fault. In the aspect of open-circuit diagnosis, the current research mostly focuses on the field of conventional inverters, and the research on fault diagnosis of open-winding electric drive systems is rarely reported. Due to the unique symmetry and redundancy of the double-inverter driving topology of the open-winding motor, the characteristics of fault current and voltage generated in a system when some switching tubes are in fault are completely the same, and the traditional diagnosis algorithm can only position a certain pair of failed switches but cannot realize the positioning of specific fault switching tubes. Researchers research a diagnosis algorithm based on a current envelope line and instantaneous frequency, but the accurate positioning of a specific fault switch tube cannot be realized; the method has the advantages that a learner adopts a current detection method to realize accurate diagnosis and positioning of the fault switch tube, but the algorithm is complex, the diagnosis time is long, 0.5-1 fundamental wave period is needed, the influence of load disturbance is easy, and misdiagnosis is easily caused.

Model predictive control is applied to the control field of open-winding electric drive systems by more and more scholars due to the advantages of fast dynamic response, strong robustness, easiness in adding constraints and the like. In addition, the characteristic that the switching state of the model predictive control is determined and unchanged in each control period and the excellent dynamic response capability of the model predictive control can be utilized to realize a fast and reliable open-circuit fault diagnosis algorithm of the switching tube.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art, and provides a single-tube open-circuit fault diagnosis method of an open-winding electric drive system based on predictive control.

In order to achieve the purpose, the technical scheme provided by the invention is as follows: the single-tube open-circuit fault diagnosis method of the open-winding electric drive system based on predictive control comprises a direct-current power supply V_dcThe three-phase 3H bridge inverter (double parallel inverters) and the three-phase stator winding of the open winding motor; the DC power supply V_dcIs connected in parallel with a three-phase 3H bridge inverter; in the three-phase 3H bridge inverter, each phase comprises two bridge arms, each bridge arm comprises two switching tubes with anti-parallel diodes, namely the three-phase 3H bridge inverter has 12 switching tubes, and the switching tubes are respectively marked as S_nijWhere n represents the phase sequence, n ═ a, b, c, i represents the bridge arm serial number of each phase, i ═ 1,2, j represents the switching order of each bridge armThe number j is 1,2, the arms of the three-phase 3H bridge inverter are connected in parallel, the middle points of the A-phase arm are respectively marked as a1 and a2, the middle points of the B-phase arm are respectively marked as B1 and B2, and the middle points of the C-phase arm are respectively marked as C1 and C2; the three-phase stator winding of the open-winding motor is respectively connected with the midpoints of the bridge arms, namely two ends of the A-phase stator winding are respectively connected with the midpoint a1 and the midpoint a2 of the bridge arms, two ends of the B-phase stator winding are respectively connected with the midpoint B1 and the midpoint B2 of the bridge arms, and two ends of the C-phase stator winding are respectively connected with the midpoint C1 and the midpoint C2 of the bridge arms;

the single-tube open-circuit fault diagnosis method of the open-winding electric drive system based on the predictive control comprises the following steps of:

step 1: sampling phase voltages of three-phase stator windings of the open-winding motor in real time;

step 2: the estimated voltage is differed with the actually measured voltage at the corresponding moment to obtain the error voltage epsilon of three phases_a、ε_bAnd ε_cRespectively, with a given threshold h₁And comparing, and preliminarily judging whether the fault occurs, wherein the following two conditions exist:

in the first case, | ε_a|≤h₁，|ε_b|≤h₁And | ε_c|≤h₁Judging that no fault occurs, and returning to the step 1;

in the second case, when one of the following six states occurs, the fault is preliminarily determined, and the fault state variable F is set₁1, preliminarily judging the fault range of the switching tube:

state 1, epsilon_a＞h₁Switching tube S_a11Or S_a22An open circuit fault occurs;

state 2, epsilon_a＜-h₁Switching tube S_a12Or S_a21An open circuit fault occurs;

state 3, epsilon_b＞h₁Switching tube S_b11Or S_b22An open circuit fault occurs;

state 4, epsilon_b＜-h₁Switching tube S_b12Or S_b21Occurrence of open circuit failure

State 5,. epsilon_c＞h₁Switching tube S_c11Or S_c22Occurrence of open circuit failure；

State 6, ε_c＜-h₁Switching tube S_c12Or S_c21An open circuit fault occurs;

and step 3: fault state variable F₁After setting to 1, the respective states in the second case of step 2 are processed accordingly, i.e. the error voltage is integrated over a defined period of time and compared with a given threshold h₂Comparing to further confirm whether the fault occurs; if the fault is judged not to occur, the fault state variable F is set₁ Setting 0, and returning to the step 1; if the fault is judged to have occurred, the fault state variable F is set₂ Setting 1 and executing the step 4;

and 4, step 4: fault state variable F₂After setting 1, determining a faulty switch pair, and still further positioning a specific faulty switch tube; for each state in the step 2, constructing a corresponding diagnosis function J by using the relation between the fault phase bridge arm switch state and the error voltage_kTo locate a specific faulty switching tube, where k represents each state in step 2, and k is 1,2,3,4,5, 6;

and 5: and finishing the fault diagnosis.

In step 2, a threshold h is given₁And setting the voltage to be 50, and obtaining the estimated voltage of each phase from the predicted switching state by utilizing the characteristic that the switching state of the model predictive control is determined and unchanged in each control period.

In step 3, a threshold h is given₂Set to 0.05, the corresponding processing for each state in the second case of step 2 is specifically as follows:

for state 1 or state 2, for |. epsilon_aL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 3 or state 4, for |. epsilon_bL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 5 or state 6, for |. epsilon_cL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing.

In step 4, a diagnostic function is constructed by using the relation between the switching states of the bridge arms of the fault phase and the error voltage, and the switching states of the two bridge arms of each phase are respectively set as s_n1And s_n2Wherein n represents a phase sequence, n is a, b, c, and a switching state of 1 indicates that the upper tube is on and the lower tube is off, and a switching state of 0 indicates that the upper tube is off and the lower tube is on;

the diagnostic function construction for each state in step 2, and the specific diagnostic method is as follows:

for State 1, a diagnostic function is constructed

If J₁If it is less than 0, S is judged_a11A failure; if J₁If it is greater than 0, S is judged_a22A failure;

for State 2, a diagnostic function is constructed

If J₂If it is less than 0, S is judged_a12A failure; if J₂If it is greater than 0, S is judged_a21A failure;

for State 3, a diagnostic function is constructed

If J₃If it is less than 0, S is judged_b11A failure; if J₃If it is greater than 0, S is judged_b22A failure;

for State 4, a diagnostic function is constructed

If J₄If it is less than 0, S is judged_b12A failure; if J₄If it is greater than 0, S is judged_b21A failure;

for State 5, a diagnostic function is constructed

If J₅If it is less than 0, S is judged_c11A failure; if J₅If it is greater than 0, S is judged_c22A failure;

for State 6, a diagnostic function is constructed

If J₆If it is less than 0, S is judged_c12A failure; if J₆If it is greater than 0, S is judged_c21A failure;

wherein, T is the integration duration, which indicates that the integration process continues until the system executes the fault-tolerant operation mode.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the invention directly utilizes the characteristic that the switching state of the model predictive control is determined and unchanged in each control period, namely, the stator phase voltage of the open-winding motor is kept unchanged in one control period and can be predicted in advance, so that the method is simple and effective to realize.

2. The voltage quantity is the state variable which can most directly reflect the fault characteristics of the inverter, the invention directly extracts the voltage information as the basis of fault diagnosis and combines the excellent dynamic response capability of model predictive control, thereby realizing fault diagnosis in a shorter time.

3. When the system operation state is suddenly changed, the current detection diagnosis method has the advantages that the current transient state process is long in duration and irregular in waveform, misdiagnosis is easily caused, the voltage can more directly reflect the fault characteristics of the inverter, and the influence of system operation disturbance is not easily caused, so that the method has high reliability.

4. The invention overcomes the unique symmetry and redundancy of the double-inverter driving topology of the open-winding motor and can position a specific fault switch tube.

Drawings

FIG. 1 is a circuit diagram of an open-winding electric drive system.

FIG. 2 is a flow chart of the method of the present invention.

FIG. 3 shows a switching tube S_a11Or S_a22Error voltage before and after open circuit fault, fault state variable F₁、

And a fault state variable F₂And (4) waveform diagrams.

FIG. 4 shows a switching tube S_a11Diagnostic function J at open-circuit fault occurrence₁Waveform diagram, and diagnosis duration diagram.

FIG. 5 shows a switching tube S_a22Diagnostic function J at open-circuit fault occurrence₁Waveform diagram, and diagnosis duration diagram.

FIG. 6a is a graph of error voltage waveforms before and after a load disturbance occurs when an open-winding electric drive system is operating without a fault.

FIG. 6b is a graph of error voltage waveforms before and after a speed disturbance occurs when the open-winding electric drive system is operating without a fault.

Detailed Description

The present invention will be further described with reference to the following specific examples.

As shown in FIG. 1, the open-winding electric drive system of the present embodiment includes a DC power supply V_dcThe three-phase 3H bridge inverter (double parallel inverters) and the three-phase stator winding of the open winding motor; the DC power supply V_dcIs connected in parallel with a three-phase 3H bridge inverter; in the three-phase 3H bridge inverter, each phase comprises two bridge arms, each bridge arm comprises two switching tubes with anti-parallel diodes, namely the three-phase 3H bridge inverter has 12 switching tubes, and the switching tubes are respectively marked as S_nijThe neutral points of the bridge arms of the three-phase 3H bridge inverter are respectively marked as a1 and a2, the neutral points of the bridge arms of the phase A are respectively marked as B1 and B2, and the neutral points of the bridge arms of the phase C are respectively marked as C1 and C2; the three-phase stator winding of the open-winding motor is respectively connected with the middle points of the bridge arms, namely two ends of the A-phase stator winding are respectively connected with the middle points a1 and a2 of the bridge arms, two ends of the B-phase stator winding are respectively connected with the middle points B1 and B2 of the bridge arms, and two ends of the C-phase stator winding are respectively connected with the middle points C1 and C2 of the bridge arms.

As shown in fig. 2, the single-tube open-circuit fault diagnosis method for an open-winding electric drive system based on predictive control provided by the present embodiment includes the following steps:

step 1: and sampling phase voltages of three-phase stator windings of the open-winding motor in real time.

Step 2: the output switching signal is predicted and controlled by the model to obtain the estimated voltage of each phase, and the estimated voltage is differenced with the actually measured voltage at the corresponding moment to obtain the error voltage epsilon of three phases_a、ε_bAnd ε_cRespectively, with a given threshold h₁For comparison, h₁Is provided withAt 50, there are two cases:

in the first case, | ε_a|≤h₁，|ε_b|≤h₁And | ε_c|≤h₁Judging that no fault occurs, and returning to the step 1;

in the second case, when one of the following six states occurs, the fault is preliminarily determined, and the fault state variable F is set₁1, preliminarily judging the fault range of the switching tube:

state 1, epsilon_a＞h₁Switching tube S_a11Or S_a22An open circuit fault occurs;

state 2, epsilon_a＜-h₁Switching tube S_a12Or S_a21An open circuit fault occurs;

state 3, epsilon_b＞h₁Switching tube S_b11Or S_b22An open circuit fault occurs;

state 4, epsilon_b＜-h₁Switching tube S_b12Or S_b21Occurrence of open circuit failure

State 5,. epsilon_c＞h₁Switching tube S_c11Or S_c22An open circuit fault occurs;

state 6, ε_c＜-h₁Switching tube S_c12Or S_c21An open circuit fault occurs.

And step 3: fault state variable F₁After setting to 1, the respective states in the second case of step 2 are processed accordingly, with a threshold h being specified₂Set to 0.05:

for state 1 or state 2, for |. epsilon_aL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁ Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 3 or state 4, for |. epsilon_bL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁ Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 5 or state 6, for |. epsilon_cL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁ Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing.

And 4, step 4: fault state variable F₂After setting to 1, the faulty switch pair is determined, but the specific faulty switch tube still needs to be further positioned. Constructing a diagnosis function by using the relation between the switching states of the bridge arms of the fault phase and the error voltage, and setting the switching states of the two bridge arms of each phase as s_n1And s_n2Where n represents the phase sequence, n ═ a, b, and c, a switch state of 1 indicates top tube on and bottom tube off, and a switch state of 0 indicates top tube offThe tube is disconnected and connected. For each state in step 2, a corresponding diagnostic function J is constructed_kWherein k represents each state in step 2, k is 1,2,3,4,5, 6; the specific diagnostic function construction and diagnostic method is as follows:

for State 1, a diagnostic function is constructed

If J₁If it is less than 0, S is judged_a11A failure; if J₁If it is greater than 0, S is judged_a22A failure;

for State 2, a diagnostic function is constructed

If J₂If it is less than 0, S is judged_a12A failure; if J₂If it is greater than 0, S is judged_a21A failure;

for State 3, a diagnostic function is constructed

If J₃If it is less than 0, S is judged_b11A failure; if J₃If it is greater than 0, S is judged_b22A failure;

for State 4, a diagnostic function is constructed

If J₄If it is less than 0, S is judged_b12A failure; if J₄If it is greater than 0, S is judged_b21A failure;

for State 5, a diagnostic function is constructed

If J₅If it is less than 0, S is judged_c11A failure; if J₅If it is greater than 0, S is judged_c22A failure;

for State 6, a diagnostic function is constructed

If J₆If it is less than 0, it is judgedS_c12A failure; if J₆If it is greater than 0, S is judged_c21And (4) failure.

Wherein, the integration duration T represents that the integration process continues until the system executes the fault-tolerant operation mode.

And 5: and finishing the fault diagnosis.

This embodiment is a pair of switch tubes S_a11Or S_a22Simulink simulation is carried out under the condition of open-circuit fault, and direct-current voltage V_dc300V, control period T_sWas 100. mu.s. FIG. 3 shows a switching tube S_a11Or S_a22Error voltage before and after open circuit fault, fault state variable F₁、

And a fault state variable F₂Waveform diagram of which the threshold h₁Set to 50, threshold h₂Set to 0.05.

FIG. 4 shows a switching tube S_a11Diagnostic function J at open-circuit fault occurrence₁Waveform diagram and diagnosis duration diagram, FIG. 5 is a switch tube S_a22Diagnostic function J at open-circuit fault occurrence₁Waveform diagram and diagnosis duration diagram, it can be seen that the diagnosis duration of the method of the present invention is 0.26ms, and rapid diagnosis can be realized.

FIG. 6a is a voltage waveform diagram of an error voltage before and after a load disturbance occurs when an open-winding electric drive system operates without a fault, and a rated load torque is suddenly changed from 2 N.m to 4 N.m; FIG. 6b is a voltage waveform diagram of an error voltage before and after a rotational speed disturbance occurs when the open-winding electric drive system operates without a fault, and the rated rotational speed is suddenly changed from 3000r/min to 2000 r/min. As can be seen from the graph, the error voltage is far smaller than the threshold value before and after the disturbance, and the misdiagnosis cannot be caused. Therefore, the diagnosis method is not greatly influenced by system operation disturbance, has good reliability and is worthy of popularization.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that the changes in the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims (3)

1. The single-tube open-circuit fault diagnosis method of the open-winding electric drive system based on predictive control comprises a direct-current power supply V_dcThe three-phase 3H bridge inverter and the three-phase stator winding of the open winding motor; the DC power supply V_dcIs connected in parallel with a three-phase 3H bridge inverter; in the three-phase 3H bridge inverter, each phase comprises two bridge arms, each bridge arm comprises two switching tubes with anti-parallel diodes, namely the three-phase 3H bridge inverter has 12 switching tubes, and the switching tubes are respectively marked as S_nijThe neutral points of the bridge arms of the three-phase 3H bridge inverter are respectively marked as a1 and a2, the neutral points of the bridge arms of the phase A are respectively marked as B1 and B2, and the neutral points of the bridge arms of the phase C are respectively marked as C1 and C2; the three-phase stator winding of the open-winding motor is respectively connected with the midpoints of the bridge arms, namely two ends of the A-phase stator winding are respectively connected with the midpoint a1 and the midpoint a2 of the bridge arms, two ends of the B-phase stator winding are respectively connected with the midpoint B1 and the midpoint B2 of the bridge arms, and two ends of the C-phase stator winding are respectively connected with the midpoint C1 and the midpoint C2 of the bridge arms;

the method for diagnosing the single-tube open-circuit fault of the open-winding electric drive system based on the predictive control is characterized by comprising the following steps of:

step 1: sampling phase voltages of three-phase stator windings of the open-winding motor in real time;

step 2: the estimated voltage is differed with the actually measured voltage at the corresponding moment to obtain the error voltage epsilon of three phases_a、ε_bAnd ε_cRespectively, with a given threshold h₁And comparing, and preliminarily judging whether the fault occurs, wherein the following two conditions exist:

in the first case, | ε_a|≤h₁，|ε_b|≤h₁And | ε_c|≤h₁Judging that no fault occurs, and returning to the step 1;

in the second case, when one of the following six states occurs, the fault is preliminarily determined, and the fault state variable F is set₁1, preliminarily judging the fault range of the switching tube:

state 1, epsilon_a＞h₁Switching tube S_a11Or S_a22An open circuit fault occurs;

state 2, epsilon_a＜-h₁Switching tube S_a12Or S_a21An open circuit fault occurs;

state 3, epsilon_b＞h₁Switching tube S_b11Or S_b22An open circuit fault occurs;

state 4, epsilon_b＜-h₁Switching tube S_b12Or S_b21Occurrence of open circuit failure

State 5,. epsilon_c＞h₁Switching tube S_c11Or S_c22An open circuit fault occurs;

state 6, ε_c＜-h₁Switching tube S_c12Or S_c21An open circuit fault occurs;

and step 3: fault state variable F₁After setting to 1, the respective states in the second case of step 2 are processed accordingly, i.e. the error voltage is integrated over a defined period of time and compared with a given threshold h₂Comparing to further confirm whether the fault occurs; if the fault is judged not to occur, the fault state variable F is set₁Setting 0, and returning to the step 1; if the fault is judged to have occurred, the fault state variable F is set₂Setting 1 and executing the step 4; wherein a threshold value h is given₂Set to 0.05, the corresponding processing for each state in the second case of step 2 is specifically as follows:

for state 1 or state 2, for |. epsilon_aL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold valueh₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 3 or state 4, for |. epsilon_bL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

for state 5 or state 6, for |. epsilon_cL performing integration in time, when the integration time length T reaches 5 control periods, namely 5T_sAnd is and

less than a given threshold h₂If no fault occurs, the fault state variable F is set₁Resetting 0 and returning to the step 1; when the integration time length T does not reach 5T_sWhen the temperature of the water is higher than the set temperature,

has been equal to or greater than a given threshold h₂If the fault is determined to have occurred, the fault state variable F is set₂1, placing;

and 4, step 4: fault state variable F₂After setting 1, determining a faulty switch pair, and still further positioning a specific faulty switch tube; for each state in the step 2, constructing a corresponding diagnosis function J by using the relation between the fault phase bridge arm switch state and the error voltage_kTo locate a specific faulty switching tube, where k represents each state in step 2, and k is 1,2,3,4,5, 6;

and 5: and finishing the fault diagnosis.

2. The open-winding electric drive system single-tube open-circuit fault diagnosis method based on predictive control according to claim 1, characterized in that: in step 2, a threshold h is given₁And setting the voltage to be 50, and obtaining the estimated voltage of each phase from the predicted switching state by utilizing the characteristic that the switching state of the model predictive control is determined and unchanged in each control period.

3. The open-winding electric drive system single-tube open-circuit fault diagnosis method based on predictive control according to claim 1, characterized in that: in step 4, a diagnostic function is constructed by using the relation between the switching states of the bridge arms of the fault phase and the error voltage, and the switching states of the two bridge arms of each phase are respectively set as s_n1And s_n2Wherein n represents a phase sequence, n is a, b, c, and a switching state of 1 indicates that the upper tube is on and the lower tube is off, and a switching state of 0 indicates that the upper tube is off and the lower tube is on;

the diagnostic function construction for each state in step 2, and the specific diagnostic method is as follows:

for State 1, a diagnostic function is constructed

If J₁If it is less than 0, S is judged_a11A failure; if J₁If it is greater than 0, S is judged_a22A failure;

for State 2, a diagnostic function is constructed

If J₂If it is less than 0, S is judged_a12A failure; if J₂If it is greater than 0, S is judged_a21A failure;

for State 3, a diagnostic function is constructed

If J₃If it is less than 0, S is judged_b11A failure; if J₃If it is greater than 0, S is judged_b22A failure;

for State 4, a diagnostic function is constructed

If J₄If it is less than 0, S is judged_b12A failure; if J₄If it is greater than 0, S is judged_b21A failure;

for State 5, a diagnostic function is constructed

If J₅If it is less than 0, S is judged_c11A failure; if J₅If it is greater than 0, S is judged_c22A failure;

for State 6, a diagnostic function is constructed

If J₆If it is less than 0, S is judged_c12A failure; if J₆If it is greater than 0, S is judged_c21A failure;

wherein, T is the integration duration, which indicates that the integration process continues until the system executes the fault-tolerant operation mode.

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