A method for diagnosing faults of a static converter of a more-electric aircraft

Abstract

The application provides a kind of multi-electric aircraft static converter open circuit fault diagnosis method, belongs to the technical field of fault diagnosis. Specifically includes establishing design adaptive interval sliding mode observer, the mean of observation error is obtained, the fault diagnosis adaptive threshold, fault location threshold, fault location characteristic quantity are defined, fault diagnosis is carried out, and then fault location is carried out.The adaptive interval sliding mode observer designed in the application effectively reduces the chattering at the sliding surface while ensuring the convergence speed;The application uses adaptive threshold to improve the accuracy and robustness of fault diagnosis;The application defines the fault location threshold and fault location characteristic quantity to diagnose the open circuit fault of the static converter through the characteristics of the three-phase output current and the observation value of the adaptive interval sliding mode observer.

Description

Technical Field

[0001] This invention belongs to the field of fault diagnosis technology, and relates to a fault diagnosis method for a multi-electric aircraft static converter, and more particularly to a fault diagnosis method for a multi-electric aircraft static converter based on an adaptive interval sliding mode observer. Background Technology

[0002] In aircraft secondary power systems, static converters convert electrical energy from generators or aviation batteries into alternating current to provide reliable power to onboard electrical equipment, making them an indispensable component of the aviation power system. The safe and stable operation of the aircraft's electrical equipment also depends on the high reliability of the power supply system; a power system failure can result in enormous losses. Static converters have a complex structure with numerous power electronic components, leading to an increased failure rate during operation. Therefore, to ensure the reliability of static converters in actual operation, rapid and accurate diagnosis of switching transistor faults is essential.

[0003] The faults of the switching transistors in a static converter are mainly divided into short-circuit faults and open-circuit faults. The short-circuit fault of the switching transistor is protected by the protection circuit. When a short-circuit fault occurs in the system, the protection circuit quickly disconnects, eventually converting the short-circuit fault of the switching transistor into an open-circuit fault. Since the short-circuit fault is short-lived and will quickly convert into an open-circuit fault, we only consider diagnosing the open-circuit fault of the switching transistor in the static converter.

[0004] Currently, fault diagnosis techniques for static converters can be broadly categorized as follows:

[0005] 1. Signal Feature-Based Methods. These methods primarily analyze the circuit's operating state, sampling the inverter's voltage or current signals and extracting fault features to obtain diagnostic results. Specific related papers include "Open-Circuit Fault Diagnosis and Fault-Tolerant Control for a Grid-Connected NPCInverter" and "A real-time multiple open-circuit fault diagnosis method in voltage-source-inverter fed vector controlled drives." However, these methods suffer from slow diagnostic time and difficulty in resisting interference caused by load changes.

[0006] 2. Circuit Model-Based Methods. These methods primarily obtain estimates of specific voltage or current signals by building a circuit model, and then compare these estimates with measured reference values ​​to detect and locate faults. Specific related papers include "Fast Transistor Open-Circuit Faults Diagnosis in Grid-Tied Three-Phase VSIs Based on Average Bridge Arm Pole-to-Pole Voltages and Error-Adaptive Thresholds" and "Multiple open-circuit faults diagnosis in back-to-back converters of PMSG drives for wind turbine systems." However, these methods suffer from drawbacks such as high requirements for mathematical models and poor robustness.

[0007] 3. Data-driven methods. These methods primarily involve mining large amounts of online and offline data, analyzing and training the data to obtain diagnostic results. Specific related papers include "A data-driven fault diagnosis methodology in Three-Phase inverters for PMSM drive systems" and "Combining a HMM with a genetic algorithm for the fault diagnosis of photovoltaic inverters." However, these methods suffer from high computational complexity, algorithmic complexity, and demanding hardware requirements.

[0008] In summary, existing technologies suffer from problems such as slow diagnostic time, high computational load, complex algorithms, high requirements for mathematical models, and poor robustness. Summary of the Invention

[0009] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for diagnosing open-circuit faults in static converters of multi-electric aircraft based on an adaptive interval sliding mode observer, so as to solve the problems existing in the prior art. Specifically, by establishing an adaptive interval sliding mode observer, an adaptive threshold that varies with the fault size is designed to replace the traditional fixed threshold, thereby achieving the goal of short fault diagnosis time and strong robustness.

[0010] To achieve the above objectives, this invention provides a method for diagnosing open-circuit faults in a multi-electric aircraft static converter based on an adaptive interval sliding mode observer. The static converter topology involved in this method includes a DC power supply, two identical supporting capacitors C1 and C2, a main inverter circuit, and three identical inductors L. j Three identical line resistors r j Three identical load capacitors C j Three identical load resistors R j The supporting capacitors C1 and C2 are connected in series and then in parallel between the DC positive bus Q1 and the DC negative bus Q2 of the DC power supply.

[0011] The main inverter circuit includes four phase bridge arms connected in parallel with the DC power supply, denoted as the k-phase bridge arm, where k represents the phase sequence, k = a, b, c, f; in the four-phase bridge arm, each phase bridge arm consists of two switching transistors V kσ They are connected in series, where σ represents the serial number of the switching transistor, σ = 1, 2; in phase a, phase b, and phase c bridge arms, the switching transistor V... k1 and switching transistor V k2 Series connection, switching transistor V k1 and switching transistor V k2 The contact point is denoted as the output point ψ of the main inverter circuit. j Let j be the phase sequence, j = a, b, c. In phase f of the bridge arm, the switching transistor V... f1 and switching transistor V i2 Series connection, switching transistor V f1 and switching transistor V f2 The contact point is denoted as the midpoint ψ of the main inverter circuit. f ;

[0012] The inductor L j One end is connected to the output point ψ of the main inverter circuit j One end is connected to the line resistor r. j Connected, line resistance r j The other end is connected to the load resistor R j Load capacitor C j Connected in phase, load resistance R j The other end and the load capacitor C j The other end is connected in parallel with the midpoint ψ of the main inverter circuit. f Connected;

[0013] The diagnostic method includes the following steps:

[0014] Step 1, sample the three-phase output phase voltage U af U bf U cf Sample three-phase load voltage V a V b Vc The system equations for the static converter under fault conditions are established, and their expression is as follows:

[0015]

[0016] Where x is the state variable of the static converter, denoted as the first state variable x. Among them, i a i is the output current of phase a of the static converter. b i is the output current of phase b of the static converter. c This refers to the c-phase output current of the static converter. Let f be the derivative of the first state variable x; y is the output of the static converter, denoted as the first output y; a A fault in the static converter switching transistor is denoted as switching transistor fault f. a U is the equivalent input voltage of the static converter; ε is the disturbance of the static converter, denoted as disturbance E. The upper and lower bounds of ε are known, 0 < ε. - <ε<ε + , ε - The ε-lower bound of the perturbation, ε + The upper bound of ε represents the disturbance;

[0017] A is the state coefficient matrix of the first state variable x, denoted as the first state coefficient matrix A. Where r is the line resistance r a The resistance value, L is the inductance value. a The inductance value; B is the coefficient matrix of the equivalent input voltage U of the static converter, denoted as the first equivalent input coefficient matrix B. C is the output coefficient matrix of the first state variable x, denoted as the first output coefficient matrix C. D is the coefficient matrix of the disturbance ε, denoted as the first disturbance coefficient matrix D. F represents a switching transistor fault. a The coefficient matrix is ​​denoted as the first switch failure coefficient matrix F.

[0018] θ is the uncertainty coefficient of the equivalent input voltage U of the static converter, denoted as uncertainty coefficient θ. The upper and lower bounds of θ are known, and θ∈[θ]. - θ + ], θ - This represents the lower bound of the uncertainty coefficient θ. + Let θBU represent the upper bound of the uncertainty coefficient θ, and let θBU satisfy θ - BU<θBU<θ + BU;

[0019] Step 2, construct the adaptive interval sliding mode observer for the static converter, whose expression is:

[0020]

[0021] Here, the estimated value of the first state variable x is denoted as the first estimated value. The first estimate The upper realm, The first estimate The upper realm The derivative, The first estimate The lower bound, The first estimate lower bound The derivative of , E is the first matrix to be designed, g is the first constant to be designed, λ is a positive constant, 0 < λ < 1, α is a positive constant, 0 < α, β is a positive constant, 0 < β < 1, || is the absolute value function, and tanh is the hyperbolic tangent function;

[0022] Step 3, Calculate the first estimate Its expression is:

[0023]

[0024] Where η is a weighting factor, which changes in real time according to the magnitude of the static converter output signal y.

[0025] Step 4, define the observation error e j , Where e a e represents the observation error of the output current of phase A. b e represents the observation error of the output current of phase B. c The observation error is for the output current of phase C;

[0026] Based on the system equations under fault conditions of the static converter and the adaptive interval sliding mode observer of the static converter, the observation error equation is obtained, and its expression is:

[0027]

[0028] in, The observation error e j The derivative;

[0029] Step 5, ignore the static converter switching transistor fault signal f a Solving the observation error equation yields the observation error e. j ;

[0030] Step 6, based on the observation error e j Given an adaptive threshold T for fault diagnosis thj ;

[0031] Step 7, compare the absolute value of the observation error |e j | and fault diagnosis adaptive threshold T thj And the following diagnoses were made:

[0032] If |e j |<T thj If the static converter is found to be operating normally, the fault diagnosis is considered complete.

[0033] If |e j |≥T thj If so, it is determined that the static converter has an open-circuit fault in the switching transistor;

[0034] Step 8, convert the output current i of phase a of the static converter to... a The output current i of phase b of the static converter b and the c-phase output current i of the static converter c Expressed as the j-phase output current i j Define the fault location threshold T for phase j. j T j =1%i jmax i jmax For the j-phase output current i j The maximum value, j = a, b, c;

[0035] Define e j_av The observation error e j The mean, t is a time variable, representing the operating time of the static converter; T represents the period of the three-phase output voltage; and d represents the differential operator.

[0036] Let w be the fault location characteristic of the static converter switching transistor. j Its expression is:

[0037]

[0038] The following conditions should be used to locate switching transistor faults:

[0039] When w a =-1, and w b =1 and w c When = 1, then the switching transistor V a1 An open circuit fault occurred;

[0040] When w a =1, and w b =-1 and w c When = -1, then the switching transistor Va2 An open circuit fault occurred;

[0041] When w a =1, and w b =-1 and w c When = 1, then the switching transistor V b1 An open circuit fault occurred;

[0042] When w a =-1, and w b =1 and w c When = -1, then the switching transistor V b2 An open circuit fault occurred;

[0043] When w a =1, and w b =1 and w c When = -1, then the switching transistor V c1 An open circuit fault occurred;

[0044] When w a =-1, and w b =-1 and w c When = 1, then the switching transistor V c2 An open circuit fault occurred;

[0045] When w a =1, and w b =1 and w c When = 1, then the switching transistor V f1 An open circuit fault occurred;

[0046] When w a =-1, and w b =-1 and w c When = -1, then the switching transistor V f2 An open circuit fault has occurred.

[0047] Preferably, in step 2, the first design constant g and the first design matrix E respectively satisfy the following equations:

[0048]

[0049] A-EC≤-I

[0050] Where I is the identity matrix.

[0051] Preferably, the expression for the equivalent input voltage U of the static converter in step 1 is:

[0052]

[0053] In the formula, Three-phase load voltage The derivative, C is the second derivative of the three-phase load voltage, and C0 is the load capacitance C. j The capacitance value.

[0054] Preferably, the observation error e is obtained by solving the observation error equation in step 5. j The specific process is as follows:

[0055] Ignore static converter switch fault signal f a Solve the observation error equation The observation error e j Simplified as follows:

[0056]

[0057] Where e is the base of the natural logarithm function, e j (0) represents the observation error e j The initial value at time t = 0, ∫ represents a single integral sign, |||| is the norm symbol, and τ represents the time constant.

[0058] Preferably, the fault diagnosis adaptive threshold T in step 6 thj The formula for calculation is:

[0059]

[0060] Compared with the prior art, the beneficial effects of the present invention include:

[0061] 1. Selecting an adaptive threshold for fault diagnosis improves the anti-interference capability, accuracy, and robustness of fault diagnosis;

[0062] 2. The fault diagnosis process does not require additional sensors, reducing the cost of fault diagnosis;

[0063] 3. An adaptive interval sliding mode observer was designed, which not only accelerated the convergence speed of the dynamic process, but also reduced the high-frequency chattering of the steady-state process. Attached Figure Description

[0064] Figure 1 This is a topology diagram of the static converter in an embodiment of the present invention;

[0065] Figure 2 This is a flowchart of the open-circuit fault diagnosis method for the static converter of a multi-electric aircraft according to the present invention;

[0066] Figure 3 In the embodiment of the present invention, the switching transistor V a1 Output current i when an open circuit fault occurs j Observation error e j Fault diagnosis adaptive threshold T thj Simulation waveform diagram;

[0067] Figure 4 In the embodiment of the present invention, the switching transistor V a1 Mean observation error e when an open circuit fault occurs j_av Fault location threshold T j Fault location characteristic quantity w j Simulation waveform diagram;

[0068] Figure 5 In the embodiment of the present invention, the switching transistor V f2 Output current i when an open circuit fault occurs j Observation error e j Fault diagnosis adaptive threshold T thj Simulation waveform diagram;

[0069] Figure 6 In the embodiment of the present invention, the switching transistor V f2 Mean observation error e when an open circuit fault occurs j_av Fault location threshold T j Fault location characteristic quantity w j The simulation waveform diagram. Detailed Implementation

[0070] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0071] Figure 1 This is a topology diagram of the static converter in an embodiment of the present invention. Figure 1 As can be seen, the topology of the static converter involved in the diagnostic method of the present invention includes a DC power supply, two identical supporting capacitors C1 and C2, a main inverter circuit, and three identical inductors L. j Three identical line resistors r j Three identical load capacitors C j Three identical load resistors R j The supporting capacitors C1 and C2 are connected in series and then in parallel between the DC positive bus Q1 and the DC negative bus Q2 of the DC power supply.

[0072] The main inverter circuit includes four phase bridge arms connected in parallel with the DC power supply, denoted as the k-phase bridge arm, where k represents the phase sequence, k = a, b, c, f; in the four-phase bridge arm, each phase bridge arm consists of two switching transistors V kσ They are connected in series, where σ represents the serial number of the switching transistor, σ = 1, 2; in phase a, phase b, and phase c bridge arms, the switching transistor V... k1 and switching transistor V k2 Series connection, switching transistor V k1 and switching transistor V k2 The contact point is denoted as the output point ψ of the main inverter circuit. jLet j be the phase sequence, j = a, b, c. In phase f of the bridge arm, the switching transistor V... f1 and switching transistor V f2 Series connection, switching transistor V f1 and switching transistor V f2 The contact point is denoted as the midpoint ψ of the main inverter circuit. f .

[0073] The inductor L j One end is connected to the output point ψ of the main inverter circuit j One end is connected to the line resistor r. j Connected, line resistance r j The other end is connected to the load resistor R j Load capacitor C j Connected in phase, load resistance R j The other end and the load capacitor C j The other end is connected in parallel with the midpoint ψ of the main inverter circuit. f Connected.

[0074] exist Figure 1 In the diagram, point O is the common node of supporting capacitors C1 and C2. dc This is the DC side voltage, U in this embodiment dc =360V. V a V b V c Let i be the load voltage of phases a, b, and c of the static converter. a i b i c This refers to the output current of phases a, b, and c of the static converter.

[0075] Figure 2 This is a flowchart of the open-circuit fault diagnosis method for multi-electric aircraft static converters according to the present invention. Figure 2 As can be seen, the method for diagnosing open-circuit faults in the static converter of multi-electric aircraft includes the following steps:

[0076] Step 1, sample the three-phase output phase voltage U af U bf U cf Sample three-phase load voltage V a V b V c The system equations for the static converter under fault conditions are established, and their expression is as follows:

[0077]

[0078] Where x is the state variable of the static converter, denoted as the first state variable x. Among them, i ai is the output current of phase a of the static converter. b i is the output current of phase b of the static converter. c This refers to the c-phase output current of the static converter. Let f be the derivative of the first state variable x; y is the output of the static converter, denoted as the first output y; a A fault in the static converter switching transistor is denoted as switching transistor fault f. a U is the equivalent input voltage of the static converter; ε is the disturbance of the static converter, denoted as disturbance ε. The upper and lower bounds of ε are known, 0 < ε. - <ε<ε + , ε - The ε-lower bound of the perturbation, ε + The upper bound of ε represents the disturbance;

[0079] A is the state coefficient matrix of the first state variable x, denoted as the first state coefficient matrix A. Where r is the line resistance r a The resistance value, L is the inductance value. a The inductance value; B is the coefficient matrix of the equivalent input voltage U of the static converter, denoted as the first equivalent input coefficient matrix B. C is the output coefficient matrix of the first state variable x, denoted as the first output coefficient matrix C. D is the coefficient matrix of the disturbance ε, denoted as the first disturbance coefficient matrix D. F represents a switching transistor fault. a The coefficient matrix is ​​denoted as the first switch failure coefficient matrix F.

[0080] θ is the uncertainty coefficient of the equivalent input voltage U of the static converter, denoted as uncertainty coefficient θ. The upper and lower bounds of θ are known, and θ∈[θ]. - θ + ], θ - This represents the lower bound of the uncertainty coefficient θ. + Let θBU represent the upper bound of the uncertainty coefficient θ, and let θBU satisfy θ - BU<θBU<θ + BU.

[0081] In this embodiment, the expression for the equivalent input voltage U of the static converter is:

[0082]

[0083] In the formula, Three-phase load voltage The derivative, C is the second derivative of the three-phase load voltage, and C0 is the load capacitance C. j The capacitance value.

[0084] In this embodiment, r = 0.2Ω, L = 1.5mH, C0 = 50μF, θ = 0.97, θ + =1.1, θ - =0.9,ε=0.02+0.01sin(800πt),ε + =0.03, ε - =0.01.

[0085] Step 2, construct the adaptive interval sliding mode observer for the static converter, whose expression is:

[0086]

[0087] Here, the estimated value of the first state variable x is denoted as the first estimated value. The first estimate The upper realm, The first estimate The upper realm The derivative, The first estimate The lower bound, The first estimate lower bound The derivative of , E is the first matrix to be designed, g is the first constant to be designed, λ is a positive constant, 0 < λ < 1, α is a positive constant, 0 < α, β is a positive constant, 0 < β < 1, || is the absolute value function, and tanh is the hyperbolic tangent function.

[0088] In this embodiment, the first design constant g and the first design matrix E respectively satisfy the following equations:

[0089]

[0090] A-EC≤-I

[0091] Where I is the identity matrix.

[0092] In this embodiment, the first design constant g = 2000, and the specific numbers of the first design matrix E are as follows:

[0093]

[0094] Step 3, Calculate the first estimate Its expression is:

[0095]

[0096] Where η is a weighting factor, which changes in real time according to the magnitude of the static converter output signal y.

[0097]

[0098] Step 4, define the observation error e j , Where e a e represents the observation error of the output current of phase A. b e represents the observation error of the output current of phase B. c The observation error is for the output current of phase C;

[0099] Based on the system equations under fault conditions of the static converter and the adaptive interval sliding mode observer of the static converter, the observation error equation is obtained, and its expression is:

[0100]

[0101] in, The observation error e j The derivative of .

[0102] Step 5, ignore the static converter switching transistor fault signal f a Solving the observation error equation yields the observation error e. j .

[0103] In this embodiment, the fault signal f of the static converter switch is ignored. a Solve the observation error equation The observation error e j Simplified as follows:

[0104]

[0105] Where t is a time variable representing the operating time of the static converter, τ is a time constant, and e is the base of the natural logarithm function. j (0) represents the observation error e j The initial value at time t=0, ∫ represents a single integral sign, and |||| is the norm symbol.

[0106] Step 6, based on the observation error e j Given an adaptive threshold T for fault diagnosis thj .

[0107] In this embodiment, the fault diagnosis adaptive threshold T thj The formula for calculation is:

[0108]

[0109] Step 7, compare the absolute value of the observation error |ej | and fault diagnosis adaptive threshold T thj And the following diagnoses were made:

[0110] If |e j |<T thj If the static converter is found to be operating normally, the fault diagnosis is considered complete.

[0111] If |e j |≥T thj If so, it is determined that the static converter has an open-circuit fault in the switching transistor.

[0112] Step 8, convert the output current i of phase a of the static converter to... a The output current i of phase b of the static converter b and the c-phase output current i of the static converter c Expressed as the j-phase output current i j Define the fault location threshold T for phase j. j T j =1%i jmax i jmax For the j-phase output current i j The maximum value, j = a, b, c;

[0113] Define e j_av The observation error e j The mean, t is a time variable, representing the operating time of the static converter; T represents the period of the three-phase output voltage; and d represents the differential operator.

[0114] Let w be the fault location characteristic of the static converter switching transistor. j Its expression is:

[0115]

[0116] The following conditions should be used to locate switching transistor faults:

[0117] When w a =-1, and w b =1 and w c When = 1, then the switching transistor V a1 An open circuit fault occurred;

[0118] When w a =1, and w b =-1 and w c When V = -1, then the switching transistor V a2 An open circuit fault occurred;

[0119] When w a =1, and w b =-1 and w cWhen = 1, then the switching transistor V b1 An open circuit fault occurred;

[0120] When w a =-1, and w b =1 and w c When = -1, then the switching transistor V b2 An open circuit fault occurred;

[0121] When w a =1, and w b =1 and w c When = -1, then the switching transistor V c1 An open circuit fault occurred;

[0122] When w a =-1, and w b =-1 and w c When = 1, then the switching transistor V c2 An open circuit fault occurred;

[0123] When w a =1, and w b =1 and w c When = 1, then the switching transistor V f1 An open circuit fault occurred;

[0124] When w a =-1, and w b =-1 and w c When = -1, then the switching transistor V f2 An open circuit fault has occurred.

[0125] The invention was verified through simulation.

[0126] Figure 3 The output current i when the switching transistor Va1 experiences an open-circuit fault in this embodiment of the invention. j , Absolute value of observation error |e j | Fault diagnosis adaptive threshold T thj The simulation waveform diagram shows that, after 0.01 seconds, the three-phase output current i... a i b i c Significant changes occurred; at 0.0101 seconds, the absolute value of the observation error for phase a, |e a |Exceeded the adaptive threshold T for fault diagnosis tha The static converter was determined to have experienced an open-circuit fault in its switching transistors; simultaneously, at 0.0105 seconds, the absolute value of the observation error of phase b, |e b |Exceeded the adaptive threshold T for fault diagnosis thb At 0.0101 seconds, the absolute value of the c-phase observation error |e c|Exceeded the adaptive threshold T for fault diagnosis thc .

[0127] Figure 4 In the embodiment of the present invention, the switching transistor V a1 Mean observation error e when an open circuit fault occurs j_av Fault location threshold T j Fault location characteristic quantity w j The simulation waveform is shown in the figure; as can be seen from the figure, at 0.0103 seconds, the mean observation error e a_av Less than the fault location threshold - T a At 0.0108 seconds, the mean observation error is e b_av Greater than the fault location threshold T b At 0.0104 seconds, the mean observation error is e c_av If the fault location threshold Tc is greater than 0.0108 seconds, the fault location feature quantity w... a =-1, w b =1, w c =1, determine the switching transistor V a1 An open circuit fault has occurred.

[0128] Figure 5 The switching transistor V in this embodiment of the invention f2 Output current i when an open circuit fault occurs j , Absolute value of observation error |e j | Fault diagnosis adaptive threshold T thj The simulation waveform diagram shows that, after 0.01 seconds, the three-phase output current i... a i b i c Significant changes occurred; at 0.0101 seconds, the absolute value of the observation error for phase a, |e a |Exceeded the adaptive threshold T for fault diagnosis tha The static converter was determined to have experienced an open-circuit fault in its switching transistors; simultaneously, at 0.0102 seconds, the absolute value of the observation error of phase b, |e b |Exceeded the adaptive threshold T for fault diagnosis thb At 0.0103 seconds, the absolute value of the c-phase observation error |e c |Exceeded the adaptive threshold T for fault diagnosis thc .

[0129] Figure 6 In the embodiment of the present invention, the switching transistor V f2 Mean observation error e when an open circuit fault occurs i_av Fault location threshold T j Fault location characteristic quantity w jThe simulation waveform is shown in the figure; as can be seen from the figure, at 0.0106 seconds, the mean observation error e a_av Less than the fault location threshold - T a Observation error mean e b_av Less than the fault location threshold - T b Observation error mean e c_av Less than the fault location threshold - T c Fault location feature quantity w a =-1, w b =-1, w c =-1, determine the switching transistor V f2 An open circuit fault has occurred.

Claims

1. A method for diagnosing open-circuit faults in a multi-electric aircraft static converter, wherein the static converter topology involved in the method includes a DC power supply, two identical supporting capacitors C1 and C2, a main inverter circuit, and three identical inductors L. j Three identical line resistors r j Three identical load capacitors C j Three identical load resistors R j The supporting capacitors C1 and C2 are connected in series and then in parallel between the DC positive bus Q1 and the DC negative bus Q2 of the DC power supply. The main inverter circuit includes four phase bridge arms connected in parallel with the DC power supply, denoted as the k-phase bridge arm, where k represents the phase sequence, k = a, b, c, f; in the four-phase bridge arm, each phase bridge arm consists of two switching transistors V kσ They are connected in series, where σ represents the serial number of the switching transistor, σ = 1, 2; in phase a, phase b, and phase c bridge arms, the switching transistor V... k1 and switching transistor V k2 Series connection, switching transistor V k1 and switching transistor V k2 The contact point is denoted as the output point ψ of the main inverter circuit. j Let j be the phase sequence, j = a, b, c. In phase f of the bridge arm, the switching transistor V... f1 and switching transistor V f2 Series connection, switching transistor V f1 and switching transistor V f2 The contact point is denoted as the midpoint ψ of the main inverter circuit. f ; The inductor L j One end is connected to the output point ψ of the main inverter circuit j One end is connected to the other end, and the other end is connected to the line resistance r. j Connected, line resistance r j The other end is connected to the load resistor R. j Load capacitor C j Connected in phase, load resistance R j The other end and the load capacitor C j The other end is connected in parallel with the midpoint ψ of the main inverter circuit. f Connected; Its features are, The diagnostic method includes the following steps: Step 1, sample the three-phase output phase voltage U af U bf U cf Sample three-phase load voltage V a V b V c The system equations for the static converter under fault conditions are established, and their expression is as follows: Where x is the state variable of the static converter, denoted as the first state variable x. Among them, i a i is the output current of phase a of the static converter. b i is the output current of phase b of the static converter. c This refers to the c-phase output current of the static converter. Let f be the derivative of the first state variable x; y is the output of the static converter, denoted as the first output y; a A fault in the static converter switching transistor is denoted as switching transistor fault f. a U is the equivalent input voltage of the static converter; ε is the disturbance of the static converter, denoted as disturbance ε. The upper and lower bounds of ε are known, 0 < ε. - <ε<ε + , ε - The ε-lower bound of the perturbation, ε + The upper bound of ε represents the disturbance; A is the state coefficient matrix of the first state variable x, denoted as the first state coefficient matrix A. Where r is the line resistance r a The resistance value, L is the inductance value. a The inductance value; B is the coefficient matrix of the equivalent input voltage U of the static converter, denoted as the first equivalent input coefficient matrix B. C is the output coefficient matrix of the first state variable x, denoted as the first output coefficient matrix C. D is the coefficient matrix of the disturbance ε, denoted as the first disturbance coefficient matrix D. F represents a switching transistor fault. a The coefficient matrix is ​​denoted as the first switch failure coefficient matrix F. θ is the uncertainty coefficient of the equivalent input voltage U of the static converter, denoted as uncertainty coefficient θ. The upper and lower bounds of θ are known, and θ∈[θ]. - θ + ], θ - This represents the lower bound of the uncertainty coefficient θ. + Let θBU represent the upper bound of the uncertainty coefficient θ, and let θBU satisfy θ - BU<θBU<θ + BU; Step 2, construct the adaptive interval sliding mode observer for the static converter, whose expression is: Here, the estimated value of the first state variable x is denoted as the first estimated value. The first estimate The upper realm, The first estimate The upper realm The derivative of The first estimate The lower bound, The first estimate lower bound The derivative of , E is the first matrix to be designed, g is the first constant to be designed, λ is a positive constant, 0 < λ < 1, α is a positive constant, 0 < α, β is a positive constant, 0 < β < 1, || is the absolute value function, and tanh is the hyperbolic tangent function; Step 3, Calculate the first estimate Its expression is: Where η is a weighting factor, which changes in real time according to the magnitude of the static converter output signal y. Step 4, define the observation error e j , Where e a e represents the observation error of the output current of phase A. b e represents the observation error of the output current of phase B. c The observation error is for the output current of phase C; Based on the system equations under fault conditions of the static converter and the adaptive interval sliding mode observer of the static converter, the observation error equation is obtained, and its expression is: in, The observation error e j The derivative; Step 5, ignore the static converter switching transistor fault signal f a Solving the observation error equation yields the observation error e. j ; Step 6, based on the observation error e j Given an adaptive threshold T for fault diagnosis thj ; Step 7, compare the absolute value of the observation error |e j | and fault diagnosis adaptive threshold T thj And the following diagnoses were made: If |e j |<T thj If the static converter is found to be operating normally, the fault diagnosis is considered complete. If |e j |≥T thj If so, it is determined that the static converter has an open-circuit fault in the switching transistor; Step 8, convert the output current i of phase a of the static converter to... a The output current i of phase b of the static converter b and the c-phase output current i of the static converter c Expressed as the j-phase output current i j Define the fault location threshold T for phase j. j T j =1%i jmax i jmax For the j-phase output current i j The maximum value, j = a, b, c; Define e j_av The observation error e j The mean, t is a time variable, representing the operating time of the static converter; T represents the period of the three-phase output voltage; and d represents the differential operator. Let w be the fault location characteristic of the static converter switching transistor. j Its expression is: The following conditions should be used to locate switching transistor faults: When w a =-1, and w b =1 and w c When = 1, then the switching transistor V a1 An open circuit fault occurred; When w a =1, and w b =-1 and w c When = -1, then the switching transistor V a2 An open circuit fault occurred; When w a =1, and w b =-1 and w c When = 1, then the switching transistor V b1 An open circuit fault occurred; When w a =-1, and w b =1 and w c When = -1, then the switching transistor V b2 An open circuit fault occurred; When w a =1, and w b =1 and w c When = -1, then the switching transistor V c1 An open circuit fault occurred; When w a =-1, and w b =-1 and w c When = 1, then the switching transistor V c2 An open circuit fault occurred; When w a =1, and w b =1 and w c When = 1, then the switching transistor V f1 An open circuit fault occurred; When w a =-1, and w b =-1 and w c When = -1, then the switching transistor V f2 An open circuit fault has occurred.

2. The method for diagnosing open-circuit faults in a multi-electric aircraft static converter according to claim 1, characterized in that, Step 2: The first design constant g and the first design matrix E respectively satisfy the following equations: A-EC≤-I Where I is the identity matrix.

3. The method for diagnosing open-circuit faults in a multi-electric aircraft static converter according to claim 1, characterized in that, The expression for the equivalent input voltage U of the static converter mentioned in step 1 is: In the formula, Three-phase load voltage The derivative of C is the second derivative of the three-phase load voltage, and C0 is the load capacitance C. j The capacitance value.

4. The method for diagnosing open-circuit faults in a multi-electric aircraft static converter according to claim 1, characterized in that, Step 5 involves solving the observation error equation to obtain the observation error e. j The specific process is as follows: Ignore static converter switch fault signal f a Solve the observation error equation The observation error e j Simplified as follows: Where e is the base of the natural logarithm function, e j (0) represents the observation error e j The initial value at time t = 0, ∫ represents a single integral sign, |||| is the norm symbol, and τ represents the time constant.

5. The method for diagnosing open-circuit faults in a multi-electric aircraft static converter according to claim 1, characterized in that, Step 6 describes the adaptive threshold T for fault diagnosis. thj The formula for calculation is:

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