Three-phase inverter cascaded switching tube fault diagnosis method based on two-stage interval sliding mode observer

Abstract

The application discloses a three-phase inverter cascaded switching tube fault diagnosis method based on a two-stage interval sliding mode observer, and belongs to the technical field of three-phase inverter fault diagnosis technology.The method is as follows: a hybrid logic dynamic model is established, and an interval sliding mode observer considering the fault state of a switching tube is designed; a fault phase is judged according to a current residual error; a fault type is preliminarily judged according to the sign of the fault phase current residual error, and fault diagnosis is completed; the two-stage interval sliding mode observer is set to an observation mode corresponding to the fault, so as to match the actual state; and the diagnosis of cascaded faults is repeatedly completed.The application realizes the synchronous diagnosis of complex working conditions in which open-circuit faults and short-circuit faults exist simultaneously by constructing a hybrid logic dynamic model considering the open-circuit and short-circuit fault states of the switching tube and designing a two-stage interval sliding mode observer, and simultaneously has the rapid identification capability of cascaded faults, so that the comprehensive diagnosis, real-time performance, system operation reliability and safety of the three-phase inverter under complex fault scenes are improved.

Description

Technical Field

[0001] This invention relates to a fault diagnosis method for cascaded switching transistors in a three-phase inverter based on a two-stage interval sliding mode observer, belonging to the field of three-phase inverter fault diagnosis technology. Background Technology

[0002] As a core component of power electronic devices, the reliability and safety of three-phase inverters directly affect the stability of the entire power system. During the actual operation of three-phase inverters, switching transistors (such as IGBTs and MOSFETs), as critical power devices, are highly susceptible to failure due to factors such as overcurrent, overvoltage, or aging. Switching transistor failures mainly include two types: open-circuit faults (the transistor cannot conduct normally) and short-circuit faults (the transistor cannot turn off normally).

[0003] Currently, fault diagnosis methods for switching transistors in three-phase inverters have been extensively studied, but existing technical solutions have the following significant drawbacks:

[0004] First, most fault diagnosis methods can only detect and locate single-type switching transistor faults (such as open-circuit faults or short-circuit faults only), and cannot achieve simultaneous diagnosis of complex operating conditions where open-circuit faults and short-circuit faults coexist, thus limiting the comprehensiveness and practicality of fault diagnosis.

[0005] Secondly, in the actual operation of a three-phase inverter, when a switch experiences an open-circuit or short-circuit fault, the voltage spike generated by the fault may break down other switches, triggering subsequent cascaded faults (i.e., secondary or multiple faults induced by the initial fault).

[0006] However, existing fault diagnosis methods are insufficient in their ability to quickly identify and locate such cascading faults, making it difficult to meet the real-time diagnosis requirements of three-phase inverters under complex fault conditions, thus affecting the timeliness and effectiveness of system fault handling.

[0007] Therefore, there is an urgent need to propose a three-phase inverter fault diagnosis method that can simultaneously accommodate mixed diagnosis of open-circuit faults and short-circuit faults of switching transistors and has the ability to quickly identify cascaded faults, so as to improve the operational reliability and safety of three-phase inverters under complex fault scenarios. Summary of the Invention

[0008] To address the problems existing in the background technology, the present invention provides a method for diagnosing faults in cascaded switching transistors of a three-phase inverter based on a two-stage interval sliding mode observer.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for fault diagnosis of cascaded switching transistors in a three-phase inverter based on a two-stage interval sliding mode observer, the method comprising the following steps:

[0010] S1: Establish a hybrid logic dynamic model and design an interval sliding mode observer that considers the fault state of the switching transistor;

[0011] S101: Establish a hybrid logic dynamic model for a three-phase inverter considering both open-circuit and short-circuit faults in the switching transistors.

[0012] (1)

[0013] In formula (1):

[0014] Indicates the three-phase output current;

[0015] Indicates the direction of the three-phase output current;

[0016] ,when hour, ;when hour, ;

[0017] This indicates the resistance value of the load resistor;

[0018] Indicates the value of the filter inductance;

[0019] Indicates the DC bus voltage;

[0020] This indicates the switching signal of the switching transistor. ,when When the signal is on, it indicates that the switching transistor is conducting, meaning a short circuit fault has occurred in the switching transistor; when When this time, it means the switch is turned off, that is, the switch has an open circuit fault;

[0021] Indicates time;

[0022] S102: Based on equation (1), establish the upper and lower bounds of the predicted output of the interval sliding mode observer considering the fault state of the switching transistor:

[0023] (2)

[0024] In formula (2):

[0025] This indicates the upper bound of the predicted output;

[0026] Indicates the lower bound of the predicted output;

[0027] Indicates matrix transpose;

[0028] Indicates the upper bound of the predicted output. The first derivative;

[0029] Indicates the lower bound of the predicted output. The first derivative;

[0030] Represents the system matrix. Represents the identity matrix;

[0031] Represents the control matrix;

[0032] Represents the observation matrix;

[0033] Indicates a directly passed matrix;

[0034] Represents the observer gain matrix;

[0035] Indicates the input of the observer;

[0036] Represents the upper bound of the uncertain parameter;

[0037] Indicates the lower bound of the uncertain parameter;

[0038] Indicates the upper bound of the disturbance;

[0039] Indicates the lower bound of the perturbation;

[0040] Represents a symbolic function;

[0041] Indicates sliding mode gain;

[0042] Represents the observed value;

[0043] S103: Obtain the interval sliding mode observer:

[0044] (3)

[0045] In formula (3):

[0046] This represents the weighting factor.

[0047] S2: Fault phase identification;

[0048] S201: Use an interval sliding mode observer as a preceding observer;

[0049] S202: Set the switch signal input to the front-end observer to the original switch signal to achieve a fault-free state observation mode.

[0050] S203: Set abnormal state diagnostic variables:

[0051] (4)

[0052] In equation (4):

[0053] T c Indicates the period of the fundamental current wave;

[0054] This represents the output residual vector of the interval sliding mode observer;

[0055] This represents the observed value of the phase A current;

[0056] This represents the observed value of the phase B current;

[0057] This represents the observed value of the C-phase current;

[0058] S204: Set the abnormal state detection threshold:

[0059] (5)

[0060] In equation (5):

[0061] This represents a coefficient that considers the robustness of the fault diagnosis algorithm;

[0062] Represents the discretized system matrix;

[0063] This represents the discretized gain matrix;

[0064] This represents the discretized sliding mode gain;

[0065] in: This represents the step size of the discretization. Represents an identity matrix of appropriate dimensions;

[0066] Indicates the current time step;

[0067] S205: When When the time is 0, it indicates that a fault has occurred; otherwise, it indicates that no fault has occurred.

[0068] S206: If a fault occurs, set the fault phase detection variable as follows:

[0069] (6)

[0070] In formula (6):

[0071] This represents the output current residual for each phase. ;

[0072] S207: Fault Phase Detection Variables The phase corresponding to the largest value is the faulty phase.

[0073] S3: Fault isolation;

[0074] S301: Define fault characteristic variables:

[0075] (7)

[0076] In equation (7):

[0077] This represents the current residual corresponding to the fault in the preceding observer;

[0078] like This indicates that there is a probability of an open circuit in the upper pipe or a short circuit in the lower pipe.

[0079] like This indicates a probability of an open circuit in the lower pipe or a short circuit in the upper pipe.

[0080] Two candidate fault types can be obtained;

[0081] S302: Use two interval sliding mode observers as subsequent observers, namely an open-circuit observer and a short-circuit observer;

[0082] S303: In the open-circuit observer, let the switching signal corresponding to the switching transistor that has a probability of open-circuit fault be... This enables open-circuit state observation mode; in the short-circuit observer, the switching signal corresponding to the switching transistor that has a probability of short-circuit fault is set... To achieve short-circuit condition observation mode;

[0083] S304: Calculate the output current residuals of the two subsequent observers and select the corresponding fault residuals for each faulted phase, denoted as the open-circuit observer faulted phase residuals. and the residual of the fault phase of the short-circuit observer ;

[0084] S305: Define residual diagnostic variables:

[0085] (8)

[0086] S306: Setting thresholds for residual diagnostic variables ,like If , it indicates an open circuit fault. ， This indicates a short-circuit fault has occurred, thus completing the differentiation of candidate fault types.

[0087] S4: Set the two-level interval sliding mode observer to the observation mode corresponding to the fault to match the actual state;

[0088] S5: Repeat S2-S4 to complete the diagnosis of cascading faults.

[0089] Compared with the prior art, the beneficial effects of the present invention are:

[0090] This invention constructs a hybrid logic dynamic model that considers both open-circuit and short-circuit fault states of the switching transistors, and designs a two-stage interval sliding mode observer (the front-stage observer is used for fault phase judgment, and the rear-stage observer achieves fault isolation through open-circuit / short-circuit state observation mode). This enables synchronous diagnosis of complex operating conditions where open-circuit and short-circuit faults coexist, and also has the ability to quickly identify cascaded faults. This effectively improves the comprehensiveness, real-time performance, system reliability, and safety of three-phase inverter diagnosis in complex fault scenarios. Attached Figure Description

[0091] Figure 1 This is a flowchart of the present invention;

[0092] Figure 2 This is a schematic diagram of a three-phase inverter.

[0093] Figure 3 This is a diagram of the three-phase current waveforms obtained from the experiment in the embodiment;

[0094] Figure 4 This is a waveform diagram of the fault diagnosis variables obtained from the experiment in the embodiment;

[0095] Figure 5 This is a diagram showing the fault diagnosis results obtained from the experiment in the embodiment. Detailed Implementation

[0096] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0097] A fault diagnosis method for cascaded switches in a three-phase inverter based on a two-stage interval sliding mode observer, the method comprising the following steps:

[0098] S1: Establish a hybrid logic dynamic model and design an interval sliding mode observer that considers the fault state of the switching transistor;

[0099] S101: Based on the operating conditions of the three-phase inverter, establish a hybrid logic dynamic model of the three-phase inverter considering both open-circuit faults and short-circuit faults of the switching transistors:

[0100] (1)

[0101] In formula (1):

[0102] Indicates the three-phase output current;

[0103] Indicates the direction of the three-phase output current;

[0104] ,when hour, ;when hour, ;

[0105] This indicates the resistance value of the load resistor;

[0106] Indicates the value of the filter inductance;

[0107] Indicates the DC bus voltage;

[0108] This indicates the switching signal of the switching transistor. ,when When the signal is on, it indicates that the switching transistor is conducting, meaning a short circuit fault has occurred in the switching transistor; when When this time, it means the switch is turned off, that is, the switch has an open circuit fault;

[0109] Indicates time;

[0110] S102: Based on equation (1), establish the upper and lower bounds of the predicted output of the interval sliding mode observer considering the fault state of the switching transistor:

[0111] (2)

[0112] In formula (2):

[0113] This indicates the upper bound of the predicted output;

[0114] Indicates the lower bound of the predicted output;

[0115] Indicates matrix transpose;

[0116] Indicates the upper bound of the predicted output. The first derivative;

[0117] Indicates the lower bound of the predicted output. The first derivative;

[0118] Represents the system matrix. Represents the identity matrix;

[0119] Represents the control matrix;

[0120] Represents the observation matrix;

[0121] Indicates a directly passed matrix;

[0122] Represents the observer gain matrix;

[0123] Indicates the input of the observer;

[0124] Represents the upper bound of the uncertain parameter;

[0125] Indicates the lower bound of the uncertain parameter;

[0126] Indicates the upper bound of the disturbance;

[0127] Indicates the lower bound of the perturbation;

[0128] Represents a symbolic function;

[0129] Indicates sliding mode gain;

[0130] Represents the observed value;

[0131] S103: Obtain the interval sliding mode observer:

[0132] (3)

[0133] In formula (3):

[0134] This represents the weighting factor.

[0135] S2: Use an interval sliding mode observer as a front-end observer, set it to the fault-free state observation mode, predict the output current under fault-free state, calculate the residual between the predicted output current and the actual output current, and use this to determine the fault phase.

[0136] S201: Use an interval sliding mode observer as a preceding observer;

[0137] S202: Set the switch signal input to the front-end observer to the original switch signal to achieve a fault-free state observation mode.

[0138] S203: Set abnormal state diagnostic variables:

[0139] (4)

[0140] In equation (4):

[0141] T c Indicates the period of the fundamental current wave;

[0142] This represents the output residual vector of the interval sliding mode observer;

[0143] This represents the observed value of the phase A current;

[0144] This represents the observed value of the phase B current;

[0145] This represents the observed value of the C-phase current;

[0146] S204: Set the abnormal state detection threshold:

[0147] (5)

[0148] In equation (5):

[0149] This represents a coefficient that considers the robustness of the fault diagnosis algorithm;

[0150] Represents the discretized system matrix;

[0151] This represents the discretized gain matrix;

[0152] This represents the discretized sliding mode gain;

[0153] in: This represents the step size of the discretization. Represents an identity matrix of appropriate dimensions;

[0154] Indicates the current time step;

[0155] S205: When When the time is 0, it indicates that a fault has occurred; otherwise, it indicates that no fault has occurred.

[0156] S206: If a fault occurs, set the fault phase detection variable as follows:

[0157] (6)

[0158] In formula (6):

[0159] This represents the output current residual for each phase. ;

[0160] S207: Fault Phase Detection Variables The phase corresponding to the largest value is the faulty phase.

[0161] S3: Fault isolation;

[0162] S301: Define fault characteristic variables:

[0163] (7)

[0164] In equation (7):

[0165] This represents the current residual corresponding to the fault in the preceding observer;

[0166] like This indicates that there is a probability of an open circuit in the upper pipe or a short circuit in the lower pipe.

[0167] like This indicates a probability of an open circuit in the lower pipe or a short circuit in the upper pipe.

[0168] Two candidate fault types can be obtained;

[0169] This indicates there is no fault, since a fault has already been detected previously. Theoretically, it shouldn't happen.

[0170] S302: Use two interval sliding mode observers as subsequent observers, namely an open-circuit observer and a short-circuit observer;

[0171] S303: In the open-circuit observer, let the switching signal corresponding to the switching transistor that has a probability of open-circuit fault be... This enables open-circuit state observation mode; in the short-circuit observer, the switching signal corresponding to the switching transistor that has a probability of short-circuit fault is set... To achieve short-circuit condition observation mode;

[0172] S304: Calculate the output current residuals of the two subsequent observers and select the corresponding fault residuals for each faulted phase, denoted as the open-circuit observer faulted phase residuals. and the residual of the fault phase of the short-circuit observer ;

[0173] S305: Define residual diagnostic variables:

[0174] (8)

[0175] S306: Setting thresholds for residual diagnostic variables ,like If , it indicates an open circuit fault. ， This indicates a short-circuit fault has occurred, thus completing the differentiation of candidate fault types.

[0176] S4: Set the two-stage interval sliding mode observer (pre-stage observer and post-stage observer) to the observation mode of the corresponding fault to match the actual state;

[0177] S5: Repeat S2-S4 to complete the diagnosis of cascading faults.

[0178] Example 1:

[0179] The engineering object of this invention is a three-phase inverter. The structure of the three-phase inverter is as follows: Figure 2 As shown, it includes a DC power supply, a main inverter circuit, three inductors with the same inductance value, three resistors with the same resistance value, and a control module.

[0180] The main inverter circuit includes three bridge arms, each containing two power semiconductor switching devices, for a total of six power semiconductor switching devices, denoted as Q1 to Q6.

[0181] The input to the control module is the three-phase current measurement value, and the output is six switching signals, where the control signal of the lower transistor is the non-signal of the control signal of the upper transistor.

[0182] In this embodiment, the DC bus voltage of the three-phase inverter is 20V, and the output current amplitude is set to 3.6A.

[0183] Observer gain matrix in S102 Sliding mode gain .

[0184] S204 .

[0185] Based on the observer's residuals, in S306 It can be set to 10%~20% of the expected peak current output.

[0186] This embodiment was verified through experiments.

[0187] Figure 3 In this embodiment, the three-phase current output by the three-phase inverter is measured by a current sensor. , as well as The waveform shows that an open-circuit fault occurs in Q3 at 0.015s, and a short-circuit fault occurs in Q1 at 0.061s. After an open-circuit fault occurs, the positive half-cycle of the corresponding phase current is missing; after a short-circuit fault occurs, the corresponding phase current shifts in the positive direction.

[0188] Figure 4 The abnormal state diagnostic variables calculated in this embodiment and residual diagnostic variables The waveform shows that after Q3 experiences an open-circuit fault, An increase indicates a fault has occurred, and the faulty phase is identified as phase B. A positive value indicates an open-circuit fault, and the open-circuit fault diagnosis for Q3 is complete. The short-circuit fault diagnosis for Q1 is similar, except that M is a negative value.

[0189] Figure 5 The diagram shows the fault diagnosis results. OC3 represents the fault diagnosis result for Q3 open circuit, and SC1 represents the fault diagnosis result for Q1 short circuit. As can be seen from the diagram, the completion times for the two fault diagnoses are 0.018s and 0.077s, respectively.

[0190] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0191] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for fault diagnosis of cascaded switching transistors in a three-phase inverter based on a two-stage interval sliding mode observer, characterized in that: The method includes the following steps: S1: Establish a hybrid logic dynamic model and design an interval sliding mode observer that considers the fault state of the switching transistor; S1 includes the following steps: S101: Establish a hybrid logic dynamic model for a three-phase inverter considering both open-circuit and short-circuit faults in the switching transistors. (1) In formula (1): Indicates the three-phase output current; Indicates the direction of the three-phase output current; ,when hour, ;when hour, ; This indicates the resistance value of the load resistor; Indicates the value of the filter inductance; Indicates the DC bus voltage; This indicates the switching signal of the switching transistor. ,when When the switch is on, it indicates that the switching transistor is conducting, meaning a short circuit fault has occurred in the switching transistor; when When this occurs, it indicates that the switching transistor is turned off, meaning that the switching transistor has an open circuit fault. Indicates time; S102: Based on equation (1), establish the upper and lower bounds of the predicted output of the interval sliding mode observer considering the fault state of the switching transistor: (2) In formula (2): This indicates the upper bound of the predicted output; Indicates the lower bound of the predicted output; Indicates matrix transpose; Indicates the upper bound of the predicted output. The first derivative; Indicates the lower bound of the predicted output. The first derivative; Represents the system matrix. Represents the identity matrix; Represents the control matrix; Represents the observation matrix; Indicates a directly passed matrix; Represents the observer gain matrix; Indicates the input of the observer; Represents the upper bound of the uncertain parameter; Indicates the lower bound of the uncertain parameter; Indicates the upper bound of the disturbance; Indicates the lower bound of the perturbation; Represents a symbolic function; Indicates sliding mode gain; Represents the observed value; S103: Obtain the interval sliding mode observer: (3) In formula (3): Indicates the weighting factor; S2: Fault phase identification; S3: Fault isolation; S4: Set the two-level interval sliding mode observer to the observation mode corresponding to the fault to match the actual state; S5: Repeat S2-S4 to complete the diagnosis of cascading faults.

2. The method for fault diagnosis of cascaded switching transistors in a three-phase inverter based on a two-stage interval sliding mode observer as described in claim 1, characterized in that: S2 includes the following steps: S201: Use an interval sliding mode observer as a preceding observer; S202: Set the switch signal input to the front-end observer to the original switch signal to achieve a fault-free state observation mode. S203: Set abnormal state diagnostic variables: (4) In equation (4): T c Indicates the period of the fundamental current wave; This represents the output residual vector of the interval sliding mode observer; This represents the observed value of the phase A current; This represents the observed value of the phase B current; This represents the observed value of the C-phase current; S204: Set the abnormal state detection threshold: (5) In equation (5): This represents a coefficient that considers the robustness of the fault diagnosis algorithm; Represents the discretized system matrix; This represents the discretized gain matrix; This represents the discretized sliding mode gain; in: This represents the step size of the discretization. Represents an identity matrix of appropriate dimensions; Indicates the current time step; S205: When When the time is 0, it indicates that a fault has occurred; otherwise, it indicates that no fault has occurred. S206: If a fault occurs, set the fault phase detection variable as follows: (6) In formula (6): This represents the output current residual for each phase. ; S207: Fault Phase Detection Variables The phase corresponding to the largest value is the faulty phase.

3. The method for fault diagnosis of cascaded switching transistors in a three-phase inverter based on a two-stage interval sliding mode observer as described in claim 2, characterized in that: S3 includes the following steps: S301: Define fault characteristic variables: (7) In equation (7): This represents the current residual corresponding to the fault in the preceding observer; like This indicates that there is a probability of an open circuit in the upper pipe or a short circuit in the lower pipe. like This indicates a probability of an open circuit in the lower pipe or a short circuit in the upper pipe. Two candidate fault types can be obtained; S302: Use two interval sliding mode observers as subsequent observers, namely an open-circuit observer and a short-circuit observer; S303: In the open-circuit observer, let the switching signal corresponding to the switching transistor that has a probability of open-circuit fault be... This enables open-circuit state observation mode; in the short-circuit observer, the switching signal corresponding to the switching transistor that has a probability of short-circuit fault is set... To achieve short-circuit condition observation mode; S304: Calculate the output current residuals of the two subsequent observers and select the corresponding fault residuals for each faulted phase, denoted as the open-circuit observer faulted phase residuals. and the residual of the fault phase of the short-circuit observer ; S305: Define residual diagnostic variables: (8) S306: Setting thresholds for residual diagnostic variables ,like If , it indicates an open circuit fault. ， This indicates a short-circuit fault has occurred, thus completing the differentiation of candidate fault types.

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