A Fault-Tolerant Control Method for DC Converter

Abstract

The present invention provides a fault-tolerant control method for a DC converter, and relates to the technical field of fault-tolerant control of DC converters. The method comprises the following steps: pre-building a DC converter system, and establishing a corresponding mathematical model according to the switching characteristics of the DC converter system; step 2: designing an adaptive observer to estimate the state of the DC converter system and the voltage source fault; and step 3: designing a state feedback fault-tolerant controller to achieve fault-tolerant control performance. The present invention takes into account that in the case of a voltage source fault and external disturbance in the DC converter, the fault estimation can be performed by designing an adaptive observer, and then the size and shape of the fault can be obtained; and the fault-tolerant control performance is achieved by designing a state feedback fault-tolerant controller, so that in the case of a voltage source fault and external disturbance, the DC converter can still maintain stable and safe operation within the required range. Based on this, the problem that the fault-tolerant control effect cannot be achieved for the DC converter in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of fault-tolerant control of direct current converters, and in particular to a fault-tolerant control method of direct current converters. Background Art

[0002] The DC converter is the core component of the switching power supply, so it is also an important component to maintain the normal operation of power electronic equipment. Once it fails, it will affect the performance of the power electronic equipment, specifically, it will cause the power electronic equipment to fail and then fail to operate normally. However, in actual production, the economic losses caused by the shutdown of power electronic equipment and the maintenance costs required to restore its normal operation are gradually increasing in the proportion of industrial costs, and the economic losses caused by the paralysis of the production system and safety accidents caused by equipment failure are also rising; therefore, the failure of the DC converter may eventually cause a large economic loss and pose a threat to personal safety. Therefore, it is particularly important to perform effective fault diagnosis and fault-tolerant control on the DC converter; among them, fault-tolerant control is the system's tolerance technology for faults, which means that when the system fails, the system can still maintain its own operation in a safe state according to the expected performance indicators or with slightly reduced performance indicators.

[0003] However, in the current DC converter and switching power supply market, although there are some technologies that can perform fault diagnosis, there is still a large gap in fault-tolerant control technology when a fault occurs. For example, the Chinese patent with publication number CN107800291A provides a DC converter based on a fuel cell and a control method thereof, wherein a DC converter fault diagnosis module is provided, through which the DC converter fault diagnosis can be performed; however, the patent can only realize the diagnosis of faults in the DC converter, and cannot achieve the fault-tolerant control effect.

[0004] In summary, the present invention provides a fault-tolerant control method for a DC converter, which can achieve a fault-tolerant control effect for the DC converter, thereby enabling the DC converter to maintain safe operation as required when a fault occurs. Summary of the invention

[0005] The object of the present invention is to provide a fault-tolerant control method for a DC converter, so as to solve the problem mentioned in the above background technology that the DC converter cannot be controlled by the prior art.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A DC converter fault-tolerant control method comprises the following steps:

[0008] Step 1: pre-build a DC converter system, and establish a corresponding mathematical model according to the switching characteristics of the DC converter system;

[0009] Step 2: Design an adaptive observer to estimate the state of the DC converter system and the voltage source fault;

[0010] Step 3: Design a state feedback fault-tolerant controller to achieve fault-tolerant control performance.

[0011] Furthermore, in step 1, the established mathematical model is a switching affine system mathematical model, and the expression of the switching affine system mathematical model is as follows:

[0012] ;

[0013] in, , indicating the state of the DC converter system; , represents the control input; , represents the measurement output; , is the affine term; , represents the voltage source failure of the DC converter (which can also be understood as actuator failure); , represents a disturbance and belongs to , represents the infinite norm; For the switching signal, available subsystems; for example, if is 2, then the coefficient matrix is , , , , , , , denote the system constant matrices with appropriate dimensions respectively.

[0014] Furthermore, in step 2, the expression of the adaptive observer is as follows:

[0015] ;

[0016] in, is the learning rate; is the matrix to be designed; and They are and An estimated value of represents the control gain of the adaptive observer.

[0017] Furthermore, in step 2, the state of the DC converter system and the voltage source fault are estimated by designing an adaptive observer. The state estimation error and fault estimation error of the DC converter system are now defined as: , , and , then the following description of the DC converter system state estimation error and fault estimation error is obtained:

[0018] ;

[0019] in, represents the system state estimation error, represents the fault estimation error.

[0020] Furthermore, in step 3, the expression of the state feedback fault-tolerant controller obtained is as follows:

[0021] ;

[0022] in, is the control input, represents the controller gain matrix to be designed.

[0023] Furthermore, the method further comprises step 4: forming the DC converter system into a closed-loop system, performing gain analysis on the closed-loop system to obtain the conditions for the actual exponential stability of the DC converter system, and obtaining the observer gain matrix and the controller gain matrix.

[0024] Furthermore, steps 1 to 3 are implemented based on a fault-tolerant control system of a DC converter, wherein the fault-tolerant control system of the DC converter includes a model building module and a DC converter test simulation system, wherein the DC converter test simulation system includes an observer submodule and a fault-tolerant control submodule; the model building module is used to build a DC converter system and a mathematical model corresponding to the DC converter system; the observer submodule is used to design an adaptive observer for the DC converter system; and the fault-tolerant control submodule is used to design a state feedback fault-tolerant controller for the DC converter system.

[0025] Furthermore, the DC converter fault-tolerant control system also includes a gain analysis module, which is used to perform gain analysis on the closed-loop system formed by the DC converter system.

[0026] The beneficial effects achieved by the present invention are:

[0027] A fault-tolerant control method for a DC converter is provided. Considering the situation that the DC converter has a voltage source fault and an external disturbance, a fault estimation can be performed by designing an adaptive observer, thereby obtaining the size and shape of the fault; and a fault-tolerant control performance is achieved by designing a state feedback fault-tolerant controller, so that even in the case of a voltage source fault and an external disturbance, the DC converter can still maintain stable and safe operation within the required range. Therefore, compared with the prior art, the present invention can effectively avoid the situation that the power electronic equipment cannot operate normally directly due to the fault of the DC converter, thereby reducing the negative impact of the fault of the DC converter on the entire production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a structural block diagram of a DC converter fault-tolerant control system according to an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of a circuit of a DC converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] To clearly illustrate the solution in the present invention, further description is given below in conjunction with the accompanying drawings:

[0031] Example 1

[0032] This embodiment provides a DC converter fault-tolerant control method, comprising the following steps:

[0033] Step 1: Pre-build a DC converter system and establish a corresponding mathematical model based on the switching characteristics of the DC converter system.

[0034] Specifically:

[0035] According to Kirchhoff's voltage law and current law, the state space model of the DC converter system is established. Due to the affine characteristics of the state space model, and considering the DC converter system with voltage source faults and external disturbances at the same time, the DC converter system with switching characteristics is considered as a state-dependent switching problem, thereby obtaining a switching affine system mathematical model. The expression of the switching affine system mathematical model is as follows:

[0036] ;

[0037] in, , indicating the state of the DC converter system; , represents the control input; , represents the measurement output; , is the affine term; , represents the voltage source failure of the DC converter; , represents a disturbance and belongs to , represents the infinite norm; For the switching signal, Choose from the available subsystems;

[0038] By Kirchhoff's voltage law, Figure 2 The circuit dynamic model shown can be described, the switching signal Choose between the two available subsystems; then the state space model of the circuit is described as a switched affine system with the system state being In this embodiment, K takes a value of 2, for example, Figure 2 There are 2 subsystems shown, the coefficient matrix , , , , , ,

[0039] , denote the system constant matrices with appropriate dimensions, Represents resistance, Represents capacitance, represents the input voltage source, represents inductance, Represents resistance, Represents a diode.

[0040] Assumption 1: First-order derivative of actuator fault and disturbance Satisfy , ,in .

[0041] Assumption 2: For any complex number has a non-negative real part, as in the following expression:

[0042] .

[0043] Assumption 3: .

[0044] in, represents the output matrix, ( )express( )’s rank, is the dimension of the system state, is the dimension of the fault, Any plural number.

[0045] The mathematical model of the switching affine system may have multiple equilibrium points. Assuming that there are no external disturbances, faults, and control inputs, the set of available equilibrium points can be written as the following expression:

[0046] ,

[0047] in, and Respectively and Convex combination of .

[0048] In order to make subsequent research more general, define a variable , the balance point of the DC converter system Translated to the origin, we can get the equivalent system as shown in the following square expression:

[0049] ;

[0050] in, is a new affine term and .

[0051] Step 2: In the presence of voltage source fault and external disturbance, an adaptive observer is designed to estimate the state of the DC converter system and the voltage source fault.

[0052] Specifically:

[0053] The expression of the adaptive observer is as follows:

[0054] ;

[0055] in, is the learning rate; is the matrix to be designed; and They are and An estimated value of represents the control gain of the adaptive observer.

[0056] The state and voltage source fault of the DC converter system are estimated by designing an adaptive observer. The state estimation error and fault estimation error of the DC converter system are defined as: , , and , then the following description of the DC converter system state estimation error and fault estimation error is obtained:

[0057] ;

[0058] in, To represent the system state estimation error, represents the fault estimation error.

[0059] Step 3: In the presence of voltage source faults and external disturbances, a state feedback fault-tolerant controller is designed to achieve fault-tolerant control performance, thereby achieving stable and safe operation of the DC converter system.

[0060] Specifically:

[0061] The expression of the obtained state feedback fault-tolerant controller is as follows:

[0062] ;

[0063] in, is the control input, represents the controller gain matrix to be designed.

[0064] Step 4: Make the DC converter system form a closed-loop system, use the common Lyapunov function to perform gain analysis on the closed-loop system to obtain the actual exponential stability conditions of the DC converter system, and obtain the observer gain matrix and the controller gain matrix.

[0065] Specifically:

[0066] Based on the established mathematical model of the switched affine system and the designed adaptive observer and state feedback fault-tolerant controller, the closed-loop system can be expressed as follows:

[0067]

[0068] in,

[0069] ,

[0070] ;

[0071] Consider a closed-loop system, let with a Related, given and a scalar If there exists a positive definite symmetric matrix ,matrix and scalar , by solving the following linear matrix inequality conditions:

[0072]

[0073] as well as

[0074]

[0075] The matrix is ​​specifically expressed as follows:

[0076]

[0077]

[0078] Obtain the matrix to be determined that satisfies the above linear matrix expression conditions , and scalar ,thus,

[0079] The designed observer gain matrix is ​​obtained by solving the following expression:

[0080] ;

[0081] The designed controller gain matrix By making is the Hurwitz matrix.

[0082] The above control method is implemented based on the fault-tolerant control system of the DC converter. Please refer to Figure 1 , the DC converter fault-tolerant control system specifically includes:

[0083] Model building module: used to build a DC converter system and a mathematical model corresponding to the DC converter system, so that when the DC converter system has a voltage source fault and external disturbance at the same time, the DC converter system with switching characteristics is considered as a type of switching system with state-dependent switching properties.

[0084] DC converter test simulation system: The simulation system includes an observer submodule and a fault-tolerant control submodule; the observer submodule is used to design an adaptive observer for the DC converter system in the presence of voltage source faults and external disturbances, and then estimate the fault; the fault-tolerant control submodule is used to design a state feedback fault-tolerant controller for the DC converter system in the presence of voltage source faults and external disturbances, so as to achieve stable and safe operation of the DC converter system by realizing fault-tolerant control performance.

[0085] Gain analysis module: used to perform gain analysis on the closed-loop system formed by the DC converter system using a common Lyapunov function, so as to obtain the conditions for the actual exponential stability of the DC converter system, and to obtain the observer gain matrix and the controller gain matrix.

[0086] In summary, the DC converter fault-tolerant control method provided in this embodiment has the following advantages:

[0087] (1) Considering the presence of voltage source faults and external disturbances in the DC converter, the fault estimation can be performed by designing an adaptive observer to obtain the size and shape of the fault;

[0088] (2) Fault-tolerant control performance is achieved by designing a state feedback fault-tolerant controller, so that the DC converter can still maintain stable and safe operation within the required range even when subjected to voltage source failure and external disturbances.

[0089] (3) The common Lyapunov function method is used to analyze the stability of the closed-loop system, and the stability conditions of the DC converter system can be obtained.

[0090] It should be noted that the parts not described in detail or expanded in the above scheme are all existing technologies, which do not belong to the improvements made by the present invention on the existing technologies, nor do they belong to the protection scope of the technical scheme of the present invention. Therefore, they will not be described in detail in this article.

[0091] Of course, the above contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the embodiments of the present invention. The present invention is not limited to the above examples, and equal changes and improvements made by ordinary technicians in the technical field within the essential scope of the present invention should all fall within the scope of the patent coverage of the present invention.

Claims

1. A DC converter fault-tolerant control method, characterized in that: The steps include: Step 1: pre-build a DC converter system, and establish a corresponding mathematical model according to the switching characteristics of the DC converter system; Step 2: Design an adaptive observer to estimate the state of the DC converter system and the voltage source fault; Step 3: Design a state feedback fault-tolerant controller to achieve fault-tolerant control performance; In step 1, the established mathematical model is a switching affine system mathematical model, and the expression of the switching affine system mathematical model is as follows: ； in, , indicating the state of the DC converter system; , represents the control input; , represents the measurement output; , is the affine term; , represents the voltage source failure of the DC converter; , represents a disturbance and belongs to , represents the infinite norm; For the switching signal, Choose from the available subsystems; , denote the system constant matrices with appropriate dimensions respectively; In step 2, the expression of the adaptive observer is as follows: ； in, is the learning rate; is the matrix to be designed; and They are and An estimated value of represents the control gain of the adaptive observer.

2. A DC converter fault-tolerant control method according to claim 1, characterized in that: In step 2, the state of the DC converter system and the voltage source fault are estimated by designing an adaptive observer. The state estimation error and fault estimation error of the DC converter system are defined as: , , and , then the following description of the DC converter system state estimation error and fault estimation error is obtained: ； in, represents the system state estimation error, represents the fault estimation error.

3. A DC converter fault-tolerant control method according to claim 2, characterized in that: In step 3, the expression of the state feedback fault-tolerant controller is as follows: ； in, is the control input, represents the controller gain matrix to be designed.

4. A DC converter fault-tolerant control method according to claim 1, characterized in that: The method also includes step 4: forming the DC converter system into a closed-loop system, performing gain analysis on the closed-loop system to obtain the actual exponential stability condition of the DC converter system, and obtaining the observer gain matrix and the controller gain matrix.

5. A DC converter fault-tolerant control method according to claim 1, characterized in that: The steps 1 to 3 are implemented based on a DC converter fault-tolerant control system, wherein the DC converter fault-tolerant control system includes a model building module and a DC converter test simulation system, wherein the DC converter test simulation system includes an observer submodule and a fault-tolerant control submodule; The model building module is used to build a DC converter system and a mathematical model corresponding to the DC converter system; the observer submodule is used to design an adaptive observer for the DC converter system; and the fault-tolerant control submodule is used to design a state feedback fault-tolerant controller for the DC converter system.

6. A DC converter fault-tolerant control method according to claim 5, characterized in that: The DC converter fault-tolerant control system further comprises a gain analysis module, and the gain analysis module is used to perform gain analysis on the closed-loop system formed by the DC converter system.

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