A gap-based transformer fault quantitative diagnosis method

Abstract

The application discloses a kind of converter fault quantitative diagnosis methods based on gap degree, comprising the following steps;Step 1: according to KVL and KCL principle obtains nominal system model and fault system model, calculates gap degree value;Step 2: establish converter system current, voltage state two-dimensional mapping space, in the space using gap degree divides fault quantitative index;Realize converter fault relative quantitative size and gap degree mapping relationship;Step 3: two-dimensional space is expanded to three-dimensional space, and the power output capability under converter fault is directly linked with quantitative diagnosis index;Step 4: based on mapping relationship corresponding fault operating point, compared with nominal system expected operating point on control output shaft, obtain control output deviation variable;Step 5: give the fault label containing fault quantitative index and power output capability change.The diagnosis result of the application can reflect the influence of fault on converter power output capability while indicating fault degree label.

Description

Technical Field

[0001] This invention relates to the field of converter fault diagnosis technology, and specifically to a quantitative diagnostic method for converter faults based on gap degree. Background Technology

[0002] Interface converters, as key AC / DC and DC / AC power electronic conversion modules and power control units, are ubiquitous in new power systems dominated by new energy sources. However, interface converters are constantly subjected to high electrical and thermal stresses during operation. The superposition of various disturbances on the DC and AC sides further increases the peak current and voltage, inevitably increasing the failure rate of the converter system.

[0003] Existing signal-based fault diagnosis methods typically rely on one or a few system output states as the basis for fault diagnosis, merely characterizing the state change of the fault. Data-based methods, while able to obtain fault type information through sample training, treat the entire system as a black box, failing to clearly define the degree of deviation between the faulty system and the original system. Model-based methods, although capable of reflecting the internal mechanisms of faults to some extent, only measure current and voltage state deviations using existing Euclidean distance metrics to assess output state changes. For real-world physical systems like converters, external information cannot accurately characterize changes in the converter's actual output capability. If the severity of the fault is not clearly defined, and faults with small deviations but severe consequences are ignored, the fault will inevitably escalate, making it difficult to achieve optimal fault tolerance for the high reliability requirements of power electronic equipment in a rapidly developing power grid. Summary of the Invention

[0004] To overcome the above technical problems, the present invention aims to provide a quantitative fault diagnosis method for converters based on gap degree. The method introduces system output capability mapping into the quantitative fault diagnosis index, so that the diagnosis result can reflect the impact of the fault on the power output capability of the converter while representing the fault degree label.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A quantitative diagnostic method for converter faults based on gapness includes the following steps;

[0007] Step 1: Based on the topology of the target converter to be tested, obtain the nominal system model according to the principles of KVL and KCL. and fault system model And calculate the gap metric between the nominal system and the faulty system of the converter;

[0008] Step 2: Establish a two-dimensional mapping space for the current and voltage states of the converter system, and use gap measurement to classify the quantitative indicators of faults in this space; realize the mapping relationship between the relative quantitative magnitude of converter faults and the gap measurement obtained in Step 1;

[0009] Step 3: Introduce control output to expand the two-dimensional space to a three-dimensional space, and directly link the power output capability under converter fault conditions with quantitative diagnostic indicators;

[0010] Step 4: Based on the mapping relationship between the system current, voltage state and converter control input, the corresponding fault operating point is compared with the nominal system expected operating point on the control output axis to obtain the control output deviation variable;

[0011] Step 5: Design a decision function, select a diagnostic threshold based on the actual operating conditions, determine the quantitative level of the fault based on the relationship between the calculated value of the decision function and the pre-selected threshold, and give a fault label that includes the quantitative indicators of the fault and the change in power output capability.

[0012] In step 2, when dividing the quantitative indicators of faults in two-dimensional space, the concept of equal gap measurement space is established, and the fault severity is defined to be consistent in each equal gap measurement space. The quantitative indicators of faults are given based on the equal gap measurement space preset by the converter.

[0013] The method for calculating the gap in step 1 is as follows:

[0014] Assume the nominal model of the system is represented as The fault model is represented as The directed gap between the nominal system and the faulty system is then... Defined as:

[0015]

[0016] The clearance value between the two systems can then be obtained, defined as follows: and Maximum directed distance between:

[0017] .

[0018] Step 2 specifically involves:

[0019] Simultaneously establish the controlled variable current. ,Voltage The two-dimensional coordinate space represents the distance of the faulty system from the nominal system in the output state, and the quantitative index of the fault is defined using the equal gap space. The maximum value of the distance obtained in step 1 is the calculated gap value between the nominal system (system 1) and the faulty system (system 2). The magnitude of this value represents the degree of change in the correlation between current and voltage between the two systems. The larger the gap value, the greater the difference in the correlation between current and voltage between system 1 and system 2; the smaller the gap value, the smaller the difference in the correlation between current and voltage between system 1 and system 2; when the gap value is 0, it indicates that the correlation between current and voltage between system 1 and system 2 is the same, that is, the obtained fault model is the same as the nominal model, which means that the fault has not occurred.

[0020] Step 3 specifically involves:

[0021] Under normal system conditions, control output Corresponding to a single current With voltage The faulty system also retains this characteristic; under the same fault deviation, and , The relationship between them can be derived from the system fault model. Get, and at the same time , , Using these three factors as independent variables, a three-dimensional spatial movement curve can be plotted, thereby transforming the original... , The gapness in the two-dimensional state variable coordinate system is extended to , , In three-dimensional space.

[0022] In step 3, the three-dimensional space is constructed using three variables: control output, current, and voltage. The clearance in the two-dimensional state variable coordinate system is extended to the three-dimensional space, and the normal operation curve is drawn in combination with the nominal system model. Any point on the line corresponds to a single control output, current, and voltage.

[0023] Step 4 specifically involves:

[0024] In step 3 In the coordinate system, there are two operating curves, namely the nominal system operating curve ( ) and the operating curve of a fault system whose input state changes due to fault tolerance ( When the expected value of the output state is , At that time, assuming for a nominal system, the control input It can be achieved For a faulty system In other words, The relationship between the three factors changes in order to achieve the desired state. , It is necessary to adjust the control output, that is... The deviation of the change corresponding to this operating range It is directly related to the magnitude and type of system failure, that is and The gap value between them is related. The degree of fault deviation can be obtained from the calculated gap value, and the control output deviation is to be determined based on the prior fault signal characteristics and deviation range of the known fault type. The available range is mapped as follows:

[0025]

[0026] in, for Maximum available range upper limit, It is a nonlinear function. To match the gap Related fault prior bias, For normal systems and faulty systems, and These are the control outputs corresponding to the nominal operating point of the system and the control outputs at the expected operating point under fault conditions, respectively.

[0027] Step 5 specifically involves designing a decision function, taking into account gap degree. Control output Current ,Voltage Quantitative fault level classification threshold , in shape The function characterizes the fault decision, where For intermittent decision-making levels, For including current ,Voltage The state vector, Let be the decision function.

[0028] The beneficial effects of this invention are:

[0029] This invention addresses the design of quantitative indicators and their corresponding output capability degradation relationships in the converter fault diagnosis process. Combining the nominal model of the converter under fault-free conditions, a two-dimensional space of output state current and voltage is constructed, and a three-dimensional space of output state current, voltage, and control output is further built upon this. Based on gapness calculation, quantitative fault indicators are defined in the two-dimensional space using internal system deviations rather than output states. In the three-dimensional space, control output is introduced to reflect output capability constraints under converter faults, and the quantitative fault indicators are mapped to the output capability under fault conditions. This method, targeting specific converter faults, achieves quantitative diagnosis while providing output capability constraints under converter fault conditions. This provides a stronger basis for the design of converter fault-tolerant control laws, laying a theoretical foundation for improving the reliability of converter equipment. Attached Figure Description

[0030] Figure 1 This is a circuit topology diagram of an LC filter converter involved in this invention.

[0031] Figure 2 This is a two-dimensional spatial coordinate diagram of current and voltage involved in this invention.

[0032] Figure 3 This is a three-dimensional spatial coordinate diagram of current, voltage, and control output involved in this invention.

[0033] Figure 4 This is a schematic diagram of the control output adjustment range in three-dimensional space involved in this invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the embodiments.

[0035] This invention aims to design a quantitative label for the severity of a converter failure, and to map this quantitative label to the actual change in the converter's power output capability. This allows the quantitative fault level label to translate the degree of output capability degradation under a converter failure. Figure 1 The implementation method of the present invention is described in detail using the voltage source converter system with LC filter shown in the figure. The system is a second-order system and includes two output state variables: inductor current and capacitor voltage.

[0036] The specific testing steps are as follows:

[0037] Step 1: Calculate the backlash value based on the system nominal model and fault model. This calculation method is based on the system transfer function.

[0038] Based on the transfer functions from the system state-space model to the nominal system and the faulty system and The method for calculating the clearance is as follows:

[0039] Directed gap Defined as:

[0040]

[0041] The clearance value between the two systems can then be obtained, defined as follows: and Maximum directed distance between:

[0042]

[0043] Simultaneously establish the controlled variable current. ,Voltage Two-dimensional coordinate space, such as Figure 2 As shown in the figure, the distance of the faulty system from the nominal system in the output state can be characterized, and the quantitative index of the fault is defined using an equal gap space.

[0044] Step 2: Establish the controlled variable current ,Voltage With control output The three-dimensional coordinate space between them.

[0045] Under normal system conditions, the control output Corresponding to a single current With voltage The faulty system also retains this characteristic; under the same fault deviation, and , The relationship between them is known a priori. Based on this, the gapity in the two-dimensional state variable coordinate system can be extended to three-dimensional space. Specifically, as follows... Figure 3 As shown in the figure. The curve in the figure is the nominal system's normal operating curve, and any point on the line corresponds to a single control output. Current With voltage .

[0046] Step 3: Determine the mapping relationship between system backlash and fault severity.

[0047] exist In a coordinate system, there exist operating curves where the input state changes due to fault tolerance, such as... Figure 4 The red arrow indicates the deviation from the specified operating range. This is directly related to the magnitude and type of system faults. Based on the above research, the fault type and magnitude are known; therefore, we intend to determine the control output deviation based on the known prior fault signal characteristics and deviation range of the fault type. The available range is mapped as follows:

[0048]

[0049] in, for Maximum available range upper limit, It is a nonlinear function. To match the gap Related fault prior bias, For normal systems and faulty systems, and These are the control outputs corresponding to the nominal operating point of the system and the control outputs at the expected operating point under fault conditions, respectively.

[0050] Step 4: Design a quantitative fault diagnosis decision function.

[0051] Design a decision function, considering gap degree. Control output Current ,Voltage Quantitative fault level classification threshold , in shape The function characterizes the fault decision, where For intermittent decision-making levels, For including current ,Voltage The state vector, Let be the decision function.

Claims

1. A gap-based transformer fault quantitative diagnosis method, characterized in that, Includes the following steps; Step 1: based on the transformer topology to be detected, according to the principles of KVL and KCL, the nominal system model is obtained and the fault system model , and the gap metric value between the transformer nominal system and the fault system is calculated; Step 2: Establish a two-dimensional mapping space for the current and voltage states of the converter system, and use gap degree to classify quantitative indicators of faults in this space; To establish a mapping relationship between the relative quantitative magnitude of converter faults and the gap metric obtained in step 1; Step 3: Introduce control output to expand the two-dimensional space to a three-dimensional space, and directly link the power output capability under converter fault conditions with quantitative diagnostic indicators; Step 4: Based on the mapping relationship between the system current, voltage state and converter control input, the corresponding fault operating point is compared with the nominal system expected operating point on the control output axis to obtain the control output deviation variable; Step 5: Design a decision function, select a diagnostic threshold based on the actual working conditions, determine the quantitative level of the fault based on the relationship between the calculated value of the decision function and the pre-selected threshold, and give a fault label that includes quantitative fault indicators and changes in power output capability. Step 3 specifically involves: Under normal system conditions, control output Corresponding to a single current With voltage The faulty system also retains this characteristic; under the same fault deviation, and , The relationship between them can be derived from the system fault model. Get, and at the same time , , Using these three factors as independent variables, a three-dimensional spatial movement curve can be plotted, thereby transforming the original... , The gapness in the two-dimensional state variable coordinate system is extended to , , In three-dimensional space.

2. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, In step 2, when dividing the quantitative indicators of faults in two-dimensional space, the concept of equal gap measurement space is established, and the fault severity is defined to be consistent in each equal gap measurement space. The quantitative indicators of faults are given based on the equal gap measurement space preset by the converter.

3. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, The method for calculating the gap in step 1 is as follows: Assume the nominal model of the system is represented as The fault model is represented as The directed gap between the nominal system and the faulty system is then... Defined as: The clearance value between the two systems can then be obtained, defined as follows: and Maximum directed distance between: 。 4. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, Step 2 specifically involves: Simultaneously establish the controlled variable current. ,Voltage The two-dimensional coordinate space represents the distance of the faulty system from the nominal system in the output state. The quantitative index of the fault is defined using the equal gap space. The maximum value of the distance obtained in step 1 is the calculated gap value between the nominal system and the faulty system. The magnitude of this value represents the degree of change in the correlation between current and voltage between the two systems. The larger the gap value, the greater the difference in the correlation between current and voltage between system 1 and system 2. The smaller the gap value, the smaller the difference in the correlation between current and voltage between system 1 and system 2. When the gap value is 0, it indicates that the correlation between current and voltage between system 1 and system 2 is the same, that is, the obtained fault model is the same as the nominal model, which means that the fault has not occurred.

5. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, In step 3, the three-dimensional space is constructed using three variables: control output, current, and voltage. The clearance in the two-dimensional state variable coordinate system is extended to the three-dimensional space, and the normal operation curve is drawn in combination with the nominal system model. Any point on the line corresponds to a single control output, current, and voltage.

6. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, Step 4 specifically involves: In step 3 In the coordinate system, there are two operating curves, namely the nominal system operating curve ( ) and the operating curve of a fault system whose input state changes due to fault tolerance ( When the expected value of the output state is , At that time, assuming for a nominal system, the control input It can be achieved For a faulty system In other words, The relationship between the three factors changes in order to achieve the desired state. , It is necessary to adjust the control output, that is... The deviation of the change corresponding to this operating range It is directly related to the magnitude and type of system failure, that is and The gap value between them is related, and the degree of fault deviation can be obtained through the calculated gap value. The control output deviation is to be determined based on the prior fault signal characteristics and deviation range of the known fault type. The available range is mapped as follows: in, for Maximum available range upper limit, It is a nonlinear function. To match the gap Related fault prior bias, For normal systems and faulty systems, and These are the control outputs corresponding to the nominal operating point of the system and the control outputs at the expected operating point under fault conditions, respectively.

7. The quantitative diagnosis method for converter faults based on gapness according to claim 1, characterized in that, Step 5 specifically involves designing a decision function, taking into account gap degree. Control output Current ,Voltage Quantitative fault level classification threshold , in shape The function characterizes the fault decision, where For intermittent decision-making levels, For including current ,Voltage The state vector, Let be the decision function.

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