DC-dc step-down converter control method based on composite phase-sliding surface

Abstract

This application provides a control method for a DC-DC buck converter based on a composite staged sliding surface, belonging to the field of power electronics technology. This method constructs a nonlinear model of the DC-DC buck converter incorporating constant power load characteristics, performs feedback linearization on the nonlinear model to obtain a linearized error model, determines the tracking error of the output voltage relative to the reference voltage based on the linearized error model, and determines the first and second error regions accordingly. A composite staged sliding surface is then constructed, and a control quantity is determined using a power-law variable gain approach. A pulse width modulation signal is generated based on the control quantity to achieve closed-loop control. The method provided in this application can improve output voltage stability while balancing dynamic response speed and control smoothness.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for a DC-DC buck converter based on a composite phased sliding surface. Background Technology

[0002] With the development of power electronics technology, DC-DC buck converters, as commonly used DC voltage conversion devices, have been widely applied in industrial power supplies, communication equipment, motor drives, new energy power supply, and various electronic systems. DC-DC buck converters are typically used to convert input DC voltage into a target DC voltage that meets load requirements. The stability, regulation accuracy, and operational reliability of their output voltage directly affect the normal operation of downstream loads and the performance of the entire power supply system.

[0003] In related technologies, to achieve stable control of DC-DC buck converters, control methods such as proportional-integral control, dual-loop control, state feedback control, and sliding mode control are commonly used to improve the converter's output regulation capability under different operating conditions. However, in practical applications, the types of loads connected to buck converters are quite complex, and the load characteristics change with the operating state, resulting in strong nonlinear and dynamic characteristics of the system. Especially in some cascaded systems or drive systems, the load may exhibit near-constant power characteristics during certain operating phases, making the converter more sensitive to input and load disturbances. This can easily lead to output voltage fluctuations, slower dynamic recovery processes, or difficulty in balancing response speed and control stability during control, thus affecting the converter's control performance and system operational stability.

[0004] Therefore, in the control of DC-DC buck converters, the complex dynamic characteristics of the load, the insufficient stability of the output voltage, and the difficulty in balancing dynamic response speed and control stability have become urgent problems to be solved. Summary of the Invention

[0005] This application provides a control method for a DC-DC buck converter based on a composite phased sliding surface, which aims to solve the problems in existing DC-DC buck converter control, such as complex load dynamic characteristics, insufficient output voltage stability under changing operating conditions, and difficulty in balancing dynamic response speed and control stability.

[0006] In a first aspect, this application provides a control method for a DC-DC buck converter based on a composite staged sliding surface, the method comprising: Construct a nonlinear model of a DC-DC buck converter that includes constant power load characteristics; The nonlinear model is subjected to feedback linearization to obtain a linearized error model; Based on the linearized error model, the tracking error of the output voltage relative to the reference voltage is determined; Based on the tracking error, a first error region and a second error region are determined; Based on the first error region and the second error region, a composite phased sliding surface is constructed, the composite phased sliding surface including a first sliding surface corresponding to the first error region and a second sliding surface corresponding to the second error region; The control quantity of the DC-DC buck converter is determined based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law. Based on the control quantity, a pulse width modulation signal is generated to control the switching action of the DC-DC buck converter, thereby realizing closed-loop control of the DC-DC buck converter.

[0007] In one possible design, constructing a nonlinear model of the DC-DC buck converter that incorporates constant power load characteristics includes: In continuous conduction mode, the inductor current and output voltage are used as state variables, the duty cycle of the pulse width modulation control signal is used as the control input, and the state equation of the DC-DC buck converter is established by combining the input voltage, resistive load and constant power load. The output function of the DC-DC buck converter is determined based on the deviation between the output voltage and the reference voltage. Based on the state equation and the output function, a nonlinear model of a DC-DC buck converter incorporating constant power load characteristics is constructed.

[0008] In one possible design, the feedback linearization process performed on the nonlinear model to obtain a linearized error model includes: Using the output function as the first coordinate variable and the first derivative of the output function as the second coordinate variable, the coordinate transformation relationship is obtained; Specify new control input variables and establish a mapping relationship between the new control input variables and the control inputs; Based on the coordinate transformation and the mapping relationship, the nonlinear model is converted into a linearized error model.

[0009] In one possible design, determining the tracking error of the output voltage relative to the reference voltage based on the linearized error model includes: Based on the first coordinate variable and the second coordinate variable, a first error variable and a second error variable are determined, wherein the first error variable characterizes the tracking error of the output voltage relative to the reference voltage; The step of determining the first error region and the second error region based on the tracking error includes: Based on the comparison between the absolute value of the first error variable and the preset threshold, the first error region and the second error region are determined.

[0010] In one possible design, constructing a composite phased sliding surface based on the first error region and the second error region includes: A first sliding surface is constructed for the first error region; A second sliding surface is constructed for the second error region; The first sliding surface and the second sliding surface are combined to form the composite phased sliding surface.

[0011] In one possible design, the power-law variable gain approach law includes a first approach term and a second approach term. The first approach term is used to accelerate system convergence under large error conditions, and the second approach term is used to suppress control chattering under small error conditions.

[0012] In one possible design, the power-law variable gain reaching law is expressed as: ; in, This represents the first approaching term. Indicates the second approaching term. This indicates a composite, phased sliding surface. .

[0013] In one possible design, determining the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law variable gain approximation law includes: The first control law is determined based on the first sliding surface and the power-law variable gain approach law; The second control law is determined based on the second sliding surface and the power-law variable gain approach law; Based on the error region to which the tracking error belongs, a target control law is selected from the first control law and the second control law; The target control law is mapped to a duty cycle control variable.

[0014] In one possible design, generating the pulse width modulation signal based on the control quantity includes: The control quantity is compared with the triangular carrier signal to obtain the comparison result; The pulse width modulation signal is generated based on the comparison result.

[0015] Secondly, this application provides a DC-DC buck converter control system based on a composite staged sliding surface, the system comprising: The model building module is used to build a nonlinear model of a DC-DC buck converter that includes constant power load characteristics; The feedback linearization module is used to perform feedback linearization on the nonlinear model to obtain a linearized error model; An error determination module is used to determine the tracking error of the output voltage relative to the reference voltage based on the linearized error model. The region determination module is used to determine a first error region and a second error region based on the tracking error; A sliding surface construction module is used to construct a composite phased sliding surface based on the first error region and the second error region; The control quantity determination module is used to determine the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law. The pulse width modulation signal generation module is used to generate a pulse width modulation signal based on the control quantity to control the switching action of the DC-DC buck converter and realize closed-loop control of the DC-DC buck converter.

[0016] Thirdly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed, implement the method described in the first aspect or various possible designs of the first aspect.

[0017] Fourthly, this application provides a computer program product, which includes computer program code that, when run on a computer, causes the computer to implement the method described in the first aspect or various possible designs of the first aspect.

[0018] This application provides a control method for a DC-DC buck converter based on a composite staged sliding surface. By constructing a nonlinear model of the DC-DC buck converter that includes constant power load characteristics and performing feedback linearization on the nonlinear model, the influence of the negative incremental impedance characteristics of the constant power load and system nonlinearity on the control process can be reduced. Furthermore, by dividing different error regions according to the tracking error and constructing corresponding composite staged sliding surfaces, the DC-DC buck converter can adopt more targeted adjustment methods under different error states. At the same time, by combining the power-law variable gain to determine the control quantity and generating a pulse width modulation signal based on the control quantity to achieve closed-loop control, the dynamic response speed of the output voltage can be improved while the control stability is improved. This effectively solves the problems of complex load dynamic characteristics, insufficient output voltage stability, and difficulty in balancing dynamic response speed and control stability in existing DC-DC buck converter control. Attached Figure Description

[0019] Figure 1 A flowchart illustrating a DC-DC buck converter control method based on a composite staged sliding surface, provided for an embodiment of this application; Figure 2 A schematic diagram of a cascaded DC-DC buck converter system with a constant power load provided in an embodiment of this application; Figure 3 A schematic diagram of a DC-DC buck converter control system with a constant power load provided in an embodiment of this application; Figure 4 A phase plane schematic diagram of a composite phased sliding surface provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0022] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] In this article, the term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists, A and B can exist simultaneously, and B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0024] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0025] In the description of this application, unless otherwise stated, "multiple" and "at least two" mean two or more (including two), and similarly, "multiple groups" and "at least two groups" mean two or more (including two groups).

[0026] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, "connected" or "linked" can refer not only to a physical connection, but also to an electrical connection or a signal connection. For instance, it can be a direct connection, i.e., a physical connection, or an indirect connection through at least one intermediate component, as long as the circuit is connected. It can also refer to the internal connection between two components. A signal connection can refer not only to a signal connection through a circuit, but also to a signal connection through a medium, such as radio waves. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, different technical features in this application can be combined with each other.

[0028] In power electronic systems, cascaded DC-DC converter systems are widely used, especially in coal mine machinery, frequency converter drives, and intrinsically safe power supply scenarios. Power electronic converters typically serve as core power processing units to achieve power conversion and stable power supply. In a cascaded system consisting of a DC-DC power module and a motor drive system, when the motor is in steady-state operation, its speed remains essentially constant, and the load side exhibits constant power load (CPL) characteristics under certain conditions. Because constant power loads have negative incremental impedance characteristics, they reduce system damping, making the system more sensitive to input voltage fluctuations and load disturbances. This can easily lead to increased output voltage fluctuations, or even system oscillation or instability.

[0029] To address the control problem of DC-DC buck converters with constant power loads, various control strategies have been proposed in the existing technology, such as adaptive backstepping control, differential flattening control, and traditional sliding mode control. Among them, adaptive backstepping control is usually highly dependent on the system model and parameters, and its robustness under complex operating conditions still has room for improvement; differential flattening control methods do not adequately consider the comprehensive characteristics of the load in some application scenarios; although traditional sliding mode control has strong disturbance rejection capabilities, it still suffers from significant chattering and dynamic convergence performance that needs further optimization.

[0030] Based on this, this application provides a control method for a DC-DC buck converter based on a composite staged sliding surface. By performing nonlinear modeling on the DC-DC buck converter with constant power load characteristics, and combining feedback linearization, composite staged sliding surface, and power-law variable gain approach, the method improves the output voltage stability, dynamic response performance, and chatter suppression effect of the DC-DC buck converter under constant power load conditions, thereby improving the system's stable operation capability under complex operating conditions.

[0031] Figure 1 This is a flowchart illustrating a control method for a DC-DC buck converter based on a composite staged sliding surface, provided as an embodiment of this application. Figure 1 As shown, the control method provided in this application embodiment specifically includes S101 to S107, and S101 to S107 will be described in detail below.

[0032] S101. Construct a nonlinear model of a DC-DC buck converter that includes constant power load characteristics.

[0033] It should be noted that, since the DC-DC buck converter with constant power load has obvious nonlinear characteristics during operation, and the negative incremental impedance effect of constant power load will affect the system damping and output stability, the DC-DC buck converter is first modeled nonlinearly.

[0034] In practical implementation, the dynamic coupling relationship between the input side, power conversion stage and load side can be described by combining the circuit topology of the DC-DC buck converter, the dynamic characteristics of the energy storage element and the power characteristics of the load side, and a mathematical model that can characterize the dynamic change process of the output voltage can be established.

[0035] Furthermore, parameters for characterizing constant power load characteristics can be introduced into the mathematical model, and an output function related to the output adjustment process can be constructed in conjunction with the output adjustment target, thereby obtaining a nonlinear model of the DC-DC buck converter that includes constant power load characteristics.

[0036] In this embodiment, by constructing the nonlinear model, a foundation can be provided for subsequent feedback linearization processing, tracking error determination, and control law design.

[0037] S102. Perform feedback linearization on the nonlinear model to obtain a linearized error model.

[0038] It should be noted that, since the nonlinear model of the DC-DC buck converter contains nonlinear terms caused by the constant power load characteristics, if the control law is designed directly based on the nonlinear model, it will easily increase the complexity of the controller design and affect the construction of the subsequent error adjustment process. Therefore, the nonlinear model needs to be processed by feedback linearization.

[0039] In practice, a coordinate transformation relationship can be constructed based on the output function corresponding to the nonlinear model, and a new control input variable can be introduced to establish a mapping relationship between the new control input variable and the original control input. On this basis, the nonlinear model is transformed into an equivalent form to weaken the nonlinear coupling effect in the original system and transform it into a model form that is convenient for error analysis and controller design.

[0040] Furthermore, after the feedback linearization process, a linearized error model corresponding to the output adjustment process can be obtained, thereby transforming the original nonlinear system into a model basis suitable for subsequent tracking error determination and composite phased sliding mode control design.

[0041] In this embodiment, by performing feedback linearization on the nonlinear model, the impact of the system's nonlinear characteristics on the control law design can be reduced, thereby improving the pertinence and feasibility of subsequent control method design.

[0042] S103. Based on the linearization error model, determine the tracking error of the output voltage relative to the reference voltage.

[0043] It should be noted that after obtaining the linearized error model, in order to achieve closed-loop regulation of the DC-DC buck converter output process, it is necessary to further determine the deviation relationship between the current output state and the target output state, so as to serve as the basis for subsequent error region division and sliding mode control design.

[0044] In specific implementation, error variables related to the output regulation process can be determined based on the linearized error model, including at least error variables characterizing the deviation of the output voltage from the reference voltage; on this basis, state information related to the output voltage change process can also be combined to form an error descriptor quantity that reflects the dynamic regulation state of the system.

[0045] Furthermore, the tracking error not only reflects the degree to which the current output voltage of the DC-DC buck converter deviates from the target reference voltage, but also provides a basis for subsequent judgment of the error state of the system and selection of the corresponding control strategy.

[0046] In this embodiment, by determining the tracking error of the output voltage relative to the reference voltage, a unified characterization of the system output adjustment target can be achieved, laying the foundation for subsequent error region division and staged sliding mode control.

[0047] S104. Based on the tracking error, determine the first error region and the second error region.

[0048] It should be noted that during the output regulation of a DC-DC buck converter, the control objectives typically differ depending on the system's error state. For example, when the error is large, faster convergence is prioritized; when the error is small, steady-state regulation accuracy and chatter suppression are more important. Therefore, to enable the control strategy to adapt to different error states, the current system operating state needs to be partitioned according to the tracking error.

[0049] In practical implementation, the current system operating state can be divided into a first error region and a second error region based on the magnitude of the error variable corresponding to the tracking error. The first error region characterizes the operating state when the system approaches the target output state, while the second error region characterizes the operating state when the system deviates significantly from the target output state. By setting the first and second error regions, conditions can be provided for using different sliding surfaces and different control focuses under different error states.

[0050] In this embodiment, by dividing the error state into regions, the subsequent control method can be transformed from a unified control method to a phased control method, thereby enhancing the adaptability of the control strategy in the dynamic adjustment process.

[0051] S105. Based on the first error region and the second error region, a composite phased sliding surface is constructed, wherein the composite phased sliding surface includes a first sliding surface corresponding to the first error region and a second sliding surface corresponding to the second error region.

[0052] It should be noted that after determining the first error region and the second error region, in order to enable the controller to have more suitable adjustment characteristics under different error states, it is necessary to design different forms of sliding surfaces for different error regions.

[0053] In specific implementation, a first sliding surface is constructed for the first error region, and a second sliding surface is constructed for the second error region. The first and second sliding surfaces are then combined to form a composite staged sliding surface. Through this composite staged sliding surface, the system can be adjusted along different error convergence trajectories in different error regions.

[0054] The first sliding surface and the second sliding surface correspond to different control focuses, so that the system can take into account control requirements such as fast convergence, stable tracking and chatter suppression under different error states.

[0055] In this embodiment, by constructing the composite phased sliding surface, a sliding constraint basis can be provided for subsequently obtaining the control quantity by combining the power-law variable gain approach.

[0056] S106. Determine the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law.

[0057] It should be noted that after constructing the composite phased sliding surface, it is still necessary to further determine the actual control quantity driving the DC-DC buck converter for output regulation. Since the system corresponds to different sliding surfaces in different error regions, and the approach process also needs to take into account both fast convergence and chattering suppression, it is necessary to combine the aforementioned error regions, sliding surfaces, and power-law variable gain approaching law to jointly obtain the control quantity.

[0058] In practical implementation, a sliding mode surface corresponding to the current tracking error region can be selected, and a corresponding control law can be constructed by combining it with the power-law variable gain approach law, thereby obtaining the control quantity used to adjust the operating state of the DC-DC buck converter. The power-law variable gain approach law can dynamically adjust the approach process according to the current error state of the system, so that the system has a faster approach capability when the error is large and a better smooth adjustment capability when the error is small.

[0059] In this embodiment, by combining the phased sliding surface with the power-law variable gain approach law, the process of obtaining the control quantity can simultaneously take into account dynamic response performance, robustness, and chattering suppression effect.

[0060] S107. Generate a pulse width modulation signal based on the control quantity to control the switching action of the DC-DC buck converter, thereby realizing closed-loop control of the DC-DC buck converter.

[0061] It should be noted that after obtaining the control quantity, it is necessary to apply the control quantity to the actual power conversion process of the DC-DC buck converter in order to achieve drive control of the switching devices.

[0062] In practical implementation, the control quantity is converted into a modulation quantity suitable for pulse width modulation processing, and a corresponding pulse width modulation signal is generated based on the modulation quantity to drive the switching devices of the DC-DC buck converter to perform on and off control. The pulse width modulation signal serves as a bridge between the control quantity and the power switching action, enabling the implementation of the aforementioned model construction, error analysis, and control law design results into actual circuit operation, forming a complete closed-loop control process.

[0063] By changing the on-time and duty cycle of the switching devices, the energy transfer process of the DC-DC buck converter can be adjusted, thereby achieving stable control of the output voltage.

[0064] In this embodiment, by generating a pulse width modulation signal based on the control quantity and controlling the switching action of the DC-DC buck converter, the output voltage can stably track the reference voltage, thereby improving the system's operational stability and dynamic adjustment performance under complex operating conditions.

[0065] This application provides a control method for a DC-DC buck converter based on a composite staged sliding surface. By constructing a nonlinear model of the DC-DC buck converter that includes constant power load characteristics and performing feedback linearization on the nonlinear model, the influence of the negative incremental impedance characteristics of the constant power load and system nonlinearity on the control process can be reduced. Furthermore, by dividing different error regions according to the tracking error and constructing corresponding composite staged sliding surfaces, the DC-DC buck converter can adopt more targeted adjustment methods under different error states. At the same time, by combining the power-law variable gain to determine the control quantity and generating a pulse width modulation signal based on the control quantity to achieve closed-loop control, the dynamic response speed of the output voltage can be improved while the control stability is improved. This effectively solves the problems of complex load dynamic characteristics, insufficient output voltage stability, and difficulty in balancing dynamic response speed and control stability in existing DC-DC buck converter control.

[0066] Figure 2 This is a schematic diagram of a cascaded DC-DC buck converter system with a constant power load, provided as an embodiment of this application. Figure 2 As shown, the DC-DC buck converter involved in this application is a Buck converter, and its input side is connected to the input voltage. The power stage includes a switching device S controlled by a pulse width modulation signal, a freewheeling diode D, an inductor L, and an output capacitor C.

[0067] The output capacitor C is connected in parallel with the load side, which includes a resistive load R and a constant power load CPL. The current flowing through the inductor L is the inductor current. The voltage across the output terminals is the output voltage. The duty cycle of the pulse width modulation control signal is denoted as In this embodiment, the Buck converter operates in continuous conduction mode.

[0068] In one possible embodiment, the method steps shown in S101 can be implemented by S1011 to S1013, which are described in detail below.

[0069] S1011. In continuous conduction mode, the inductor current and output voltage are used as state variables, the duty cycle of the pulse width modulation control signal is used as the control input, and the state equation of the DC-DC buck converter is established by combining the input voltage, resistive load and constant power load.

[0070] exist Figure 2 Based on the circuit structure shown, and according to the circuit relationship between the inductor branch and the output capacitor branch in the Buck converter, the state equation of the DC-DC buck converter can be established as follows: .

[0071] Where P represents the power of the constant power load, Used to characterize the dynamic changes in inductor current. Used to characterize the dynamic changes in output voltage. Used to characterize the nonlinear current component corresponding to a constant power load.

[0072] S1012. Determine the output function of the DC-DC buck converter based on the deviation between the output voltage and the reference voltage.

[0073] In this embodiment, state variables are defined as follows: ,in, Indicating inductor current , Indicates output voltage .

[0074] Furthermore, based on the deviation between the output voltage and the reference voltage, the output function of the DC-DC buck converter is constructed as follows: ,in, For reference voltage, This is the output variable. The output function is used to characterize the deviation of the output voltage relative to the reference voltage.

[0075] S1013. Based on the state equation and the output function, construct a nonlinear model of a DC-DC buck converter that includes constant power load characteristics.

[0076] In this embodiment, based on the state equation and the output function, the DC-DC buck converter can be represented as a standard form of a single-input single-output SISO affine nonlinear system: .

[0077] in, Indicates system dynamic items, ; Indicates the control input gain term. ; This indicates the control input (duty cycle of the pulse width modulation control signal).

[0078] Therefore, the state equation and the output function are uniformly represented as a nonlinear model of a DC-DC buck converter that includes constant power load characteristics.

[0079] In one possible embodiment, the method steps shown in S102 can be implemented by S1021 to S1023, which are described in detail below.

[0080] S1021. Using the output function as the first coordinate variable and the first derivative of the output function as the second coordinate variable, the coordinate transformation relationship is obtained.

[0081] In this embodiment, based on the standard form of the single-input single-output affine nonlinear system obtained in step S1013, the coordinate transformation relationship is defined as follows: .

[0082] in, As the first coordinate variable, For the second coordinate variable, Indicates the output function Along the system vector field The first derivative. Therefore, the first coordinate variable... The second coordinate variable directly represents the deviation of the output voltage from the reference voltage. This represents the dynamic change relationship of the output function. Through the above coordinate transformation, the output adjustment process of the original nonlinear system can be converted into a new coordinate space for representation.

[0083] S1022. Specify new control input variables and establish a mapping relationship between the new control input variables and the control inputs.

[0084] In this embodiment, a new control input variable is specified. and the new control input variable Defined as: .

[0085] in, Indicates the output function Along the system vector field The second derivative, Indicates the output function The first derivative along the input vector field The derivative of .

[0086] Furthermore, new control input variables With the original control input The mapping relationship between them can be represented as: ;in, , .

[0087] Therefore, new control input variables can be established. With the original control input The correspondence between them provides the basis for input transformation in the subsequent conversion of the original nonlinear system into a linear system.

[0088] S1023. Based on the coordinate transformation and the mapping relationship, the nonlinear model is converted into a linearized error model.

[0089] In this embodiment, based on the coordinate transformation relationship and the mapping relationship between the new control input variable and the original control input, the nonlinear model can be converted into the following linear system form: .

[0090] Understandably, after the above transformation, the original nonlinear model of the DC-DC buck converter, which included nonlinear terms for constant power loads, is equivalently converted into a standard linear system form, thus obtaining the linearized error model. This linearized error model retains the output deviation and its dynamic changes, while also facilitating subsequent definition of error variables, error region division, and sliding mode control law design.

[0091] In one possible embodiment, the method steps shown in S103 can be implemented by Sa, which will be described in detail below.

[0092] Sa, based on the first coordinate variable and the second coordinate variable, determine the first error variable and the second error variable.

[0093] The first error variable represents the tracking error of the output voltage relative to the reference voltage.

[0094] In this embodiment, based on the first coordinate variable obtained in S102 Second coordinate variable The error variable is defined as: ;in, As the first error variable, This is the second error variable.

[0095] Due to the first coordinate variable defined in S102 For output function Furthermore, the output function is used to characterize the deviation relationship between the output voltage and the reference voltage; therefore, the first error variable... The second error variable directly characterizes the tracking error of the output voltage relative to the reference voltage. This characterizes the dynamic change process of the first error variable.

[0096] Furthermore, based on the linearized error model obtained in S1023, the state equations corresponding to the first error variable and the second error variable can be obtained as follows: .

[0097] Therefore, the first error variable and the second error variable This constitutes the error state description in the subsequent control process, where, Used to reflect the magnitude of the deviation between the current output voltage and the reference voltage. This is used to reflect the changing trend of the deviation.

[0098] In one possible embodiment, the method steps shown in S104 can be implemented by Sc, which will be described in detail below.

[0099] Sc. Based on the comparison result between the absolute value of the first error variable and the preset threshold, determine the first error region and the second error region.

[0100] In this embodiment, based on the first error variable The absolute value is compared with a preset threshold to divide the current error state of the system into regions.

[0101] The preset threshold is 1.

[0102] Specifically, it can be The corresponding area is defined as the first error area. The corresponding region is defined as the second error region. The first error region corresponds to the small error state, and the second error region corresponds to the large error state.

[0103] Understandably, when When this occurs, it indicates that the output voltage is relatively close to the reference voltage, and the system is in a small error adjustment phase; when When this occurs, it indicates that the output voltage still deviates significantly from the reference voltage, and the system is in a large error adjustment phase.

[0104] Therefore, by adjusting the first error variable By using the absolute value of the threshold to determine the operating state of the DC-DC buck converter, the first error region and the second error region can be divided, thereby providing a regional basis for constructing corresponding sliding surfaces according to different error regions.

[0105] In one possible embodiment, the method steps shown in S105 can be implemented by S1051 to S1053, which are described in detail below.

[0106] S1051. Construct a first sliding surface for the first error region.

[0107] In this embodiment, the first error region corresponds to a small error state, that is, the current system satisfies... .

[0108] For the first error region, a first sliding surface can be constructed using a fast terminal sliding surface to ensure that the system still has high convergence accuracy when approaching the reference output state.

[0109] Specifically, the first sliding surface can be represented as ;in, Indicates the first sliding surface. Indicates the first error variable. Indicates the second error variable. Represents a symbolic function. and These are the parameters of the sliding surface.

[0110] Therefore, within the small error region, by introducing a nonlinear term related to the second error variable, the system can maintain high tracking accuracy when approaching equilibrium and improve error convergence performance.

[0111] S1052. Construct a second sliding surface for the second error region.

[0112] In this embodiment, the second error region corresponds to a large error state, that is, the current system satisfies... .

[0113] For the second error region, a second sliding surface can be constructed to improve the system convergence speed.

[0114] Specifically, the second sliding surface can be represented as ;in, Indicates the second sliding surface. Let be the parameters of the sliding surface, and let the parameters satisfy: >1, 1< <2, >1.

[0115] Therefore, within the large error region, by introducing a nonlinear term related to the first error variable into the second sliding surface, the error recovery capability of the system when it deviates significantly from the target state can be enhanced, thereby improving the overall dynamic convergence speed of the system.

[0116] S1053. The first sliding surface and the second sliding surface are combined to form the composite phased sliding surface.

[0117] In this embodiment, based on the first sliding surface and the second sliding surface Composite phased sliding surfaces can be constructed. .

[0118] Specifically, the composite phased sliding surface can be represented as follows: .

[0119] Therefore, when the system is in the first error region, the first sliding surface is used for control; when the system is in the second error region, the second sliding surface is used for control. By combining the first and second sliding surfaces in different regions, a composite phased sliding surface suitable for different error states can be formed, providing a sliding constraint basis for subsequently obtaining the control quantity by combining the power-law variable gain approach law.

[0120] In one possible embodiment, the power-law variable gain approach law includes a first approach term and a second approach term, wherein the first approach term is used to accelerate system convergence under large error conditions, and the second approach term is used to suppress control chattering under small error conditions.

[0121] In this embodiment, the power-law variable gain approaching law acts on the composite phased sliding surface to adjust the system state's approach to the sliding surface.

[0122] Specifically, the first approach term and the second approach term together constitute the power-law variable gain approach law, wherein the first approach term is used to enhance the system state's approach capability to the sliding mode surface under large error conditions, and the second approach term is used to reduce the high-frequency switching effect in the approach process under small error conditions.

[0123] Furthermore, when the system is in a large error state, the sliding surface deviates significantly from the equilibrium position. In this case, the first approaching term plays a major role in the approaching process to increase the system state's approach speed to the sliding surface, thereby accelerating the overall convergence process. When the system is in a small error state, the system state has gradually approached the sliding surface. In this case, the second approaching term plays a major role in the approaching process to reduce chattering caused by excessive switching during the approaching process and improve the smoothness of the system's adjustment when approaching the equilibrium state.

[0124] Therefore, by simultaneously setting the first and second approach terms in the power-law variable gain approach law, the system can have different approach characteristics under different error states. That is, it can take into account the ability to approach quickly when the error is large and the ability to suppress chattering when the error is small, thus providing a basis for the determination of subsequent control quantities.

[0125] Specifically, the power-law gain convergence law is expressed as: ;in, This represents the first approaching term. Indicates the second approaching term. This indicates a composite, phased sliding surface. .

[0126] In this embodiment, the first approach term Related to the degree of deviation of the sliding surface, when the system is in a large error state, The first approaching term is relatively large and plays a major role in the approaching process, thereby increasing the system state's approximation speed to the sliding surface; the second approaching term... Because the exponent parameter satisfies It can maintain relatively smooth adjustment characteristics when the system approaches the sliding surface, and therefore plays a major role in the small error state to reduce the high-frequency switching effect during the approach process.

[0127] Therefore, by combining the first and second approaching terms to form the power-law variable gain approaching law, the system can have a faster convergence capability when the sliding surface deviation is large and a better chattering suppression capability when the sliding surface deviation is small, thus taking into account both dynamic response performance and control stability.

[0128] In one possible embodiment, the method steps shown in S106 can be implemented by S1061 to S1063, which are described in detail below.

[0129] S1061. Determine the first control law based on the first sliding surface and the power-law variable gain approach law.

[0130] In this embodiment, when the tracking error belongs to the first error region, the first sliding surface is used. The first control law is determined by combining the power-law variable gain approach law.

[0131] Specifically, in the small error region The first control law can be expressed as follows: ;in, This represents the first control law.

[0132] Therefore, within the first error region, the first control law combines the first sliding surface with the power-law variable gain approach law, enabling the system to adjust along the first sliding surface under small error conditions while taking into account the smoothness of the error approximation process.

[0133] S1062. Determine the second control law based on the second sliding surface and the power-law variable gain approach law.

[0134] In this embodiment, when the tracking error belongs to the second error region, the second sliding surface is used. The second control law is determined by combining the power-law variable gain approach law.

[0135] Specifically, in the large error region The second control law can be expressed as follows: ;in, This indicates the second control law.

[0136] Therefore, within the second error region, the second control law, through the second sliding surface and the power-law variable gain approaching law, enables the system to have a stronger error recovery capability when it deviates significantly from the target state, thereby improving the overall convergence speed.

[0137] S1063. Based on the error region to which the tracking error belongs, select the target control law from the first control law and the second control law.

[0138] In this embodiment, based on the error region to which the current tracking error belongs, the first control law... and the second control law Select the target control law.

[0139] Specifically, when the current system satisfies When, select the first control law As the target control law; when the current system satisfies... When, select the second control law. As a target control law.

[0140] Therefore, the controller can switch between different sub-region control laws according to the current error state of the system, so that the controller can adopt a more suitable adjustment mode in small error state and large error state respectively.

[0141] S1064. Map the target control law to a duty cycle control quantity.

[0142] In this embodiment, after selecting the target control law, the target control law is mapped to a duty cycle control quantity.

[0143] Specifically, the output of the composite sliding mode control structure can be expressed as: .

[0144] in, This indicates the duty cycle control value. This represents the duty cycle control quantity corresponding to the first control law. This represents the duty cycle control quantity corresponding to the second control law.

[0145] Therefore, the target control law can be further converted into a duty cycle control quantity suitable for acting on the DC-DC buck converter, thereby providing an input basis for the subsequent generation of pulse width modulation signals based on the duty cycle control quantity.

[0146] In one possible embodiment, the method steps shown in S107 can be implemented by S1071 and S1072, which are described in detail below.

[0147] S1071. Compare the control quantity with the triangular carrier signal to obtain the comparison result.

[0148] In this embodiment, the duty cycle control quantity obtained in S106 is used as the modulation signal input in the pulse width modulation process.

[0149] Specifically, the control quantity can be compared with the triangular carrier signal corresponding to the required switching frequency to determine the on or off state of the power switching device at the current moment.

[0150] Furthermore, when the control quantity is greater than the triangular carrier signal, the comparison result at the corresponding time can be determined as the first result; when the control quantity is less than or equal to the triangular carrier signal, the comparison result at the corresponding time can be determined as the second result. Through the comparison result, the continuously changing control quantity can be converted into a discrete switching criterion suitable for driving switching devices.

[0151] S1072. Generate the pulse width modulation signal based on the comparison result.

[0152] Specifically, when the comparison result is a first result, a high-level signal is output; when the comparison result is a second result, a low-level signal is output, thereby forming a pulse width modulation signal whose pulse width changes with the control quantity.

[0153] Furthermore, the high-level signal is used to control the switching devices in the DC-DC buck converter to turn on, and the low-level signal is used to control the switching devices to turn off. Thus, the first result and the second result correspond to different operating states of the switching devices, thereby enabling the adjustment of the on-time and off-time of the switching devices based on the control quantity, and realizing the control of the energy transfer process of the DC-DC buck converter.

[0154] Figure 3 This is a schematic diagram of a DC-DC buck converter control system with a constant power load, provided as an embodiment of this application. Figure 3 As shown, the control system includes a precise feedback linearization module, an error calculation module, a sliding mode control module, a composite staged sliding mode reaching law module, a coordinate transformation module, a pulse width modulation (PWM) module, and a DC-DC converter. The output voltage of the DC-DC converter... and inductor current The feedback is sent to the precise feedback linearization module, which performs feedback linearization processing on the system and outputs the first coordinate variable. Second coordinate variable Furthermore, based on the first coordinate variable With reference voltage The first error variable was calculated. Based on the second coordinate variable The second error variable was calculated. Subsequently, based on the first error variable... The size is used to partition the system's operating state: when the condition is met At that time, a sliding mode control model corresponding to the small error region and a composite phased sliding mode reaching law are adopted to output the first control law. When satisfied At that time, a sliding mode control model corresponding to the large error region and a composite phased sliding mode reaching law are adopted to output the second control law. The first control law Or the second control law Converted into duty cycle control quantity by coordinate transformation module or The signal is then input to the PWM module to generate the corresponding pulse width modulation signal, which controls the switching action of the DC-DC converter, thereby achieving closed-loop control of the output process of the DC-DC buck converter.

[0155] Figure 4 This is a phase plane schematic diagram of a composite phased sliding surface provided in an embodiment of this application. (See attached diagram.) Figure 4 As shown, the horizontal axis represents the first error variable. The vertical axis represents the second error variable. Wherein, curve S1=0 represents the phase trajectory corresponding to the first sliding surface, and curve S2=0 represents the phase trajectory corresponding to the second sliding surface; the two vertical dashed lines are used to indicate the boundary of the error region. Specifically, in Within the region below the preset threshold, the system uses the first sliding surface S1=0 for control to improve the tracking accuracy and adjustment stability of the system under small error conditions; Within the region where the error is greater than or equal to a preset threshold, the system uses the second sliding surface S2=0 for control to enhance the convergence speed of the system under large error conditions. Thus, by combining the first and second sliding surfaces in different error regions, a composite staged sliding surface can be formed, enabling the system to balance fast convergence performance and steady-state control performance throughout the entire adjustment process.

[0156] This application provides a DC-DC buck converter control system based on a composite phased sliding surface, which includes a model building module, a feedback linearization module, an error determination module, a region determination module, a sliding surface construction module, a control quantity determination module, and a pulse width modulation signal generation module.

[0157] The model building module is used to build a nonlinear model of a DC-DC buck converter that includes constant power load characteristics.

[0158] The feedback linearization module is used to perform feedback linearization processing on the nonlinear model to obtain a linearized error model.

[0159] An error determination module is used to determine the tracking error of the output voltage relative to the reference voltage based on the linearized error model.

[0160] The region determination module is used to determine a first error region and a second error region based on the tracking error.

[0161] The sliding surface construction module is used to construct a composite phased sliding surface based on the first error region and the second error region.

[0162] The control quantity determination module is used to determine the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law.

[0163] The pulse width modulation signal generation module is used to generate a pulse width modulation signal based on the control quantity to control the switching action of the DC-DC buck converter and realize closed-loop control of the DC-DC buck converter.

[0164] It should be noted that the specific process of each module in the control system executing the above method has been described in detail in the above embodiments, and this embodiment does not make specific limitations on it.

[0165] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 5 As shown, the electronic device 500 provided in this embodiment includes a memory 501 and a processor 502.

[0166] The memory 501 can be a separate physical unit, connected to the processor 502 via a bus 503. Alternatively, the memory 501 and processor 502 can be integrated and implemented in hardware. The memory 501 stores program instructions, which the processor 502 calls to execute operations controlled by the system in any of the above method embodiments.

[0167] Optionally, when some or all of the methods in the above embodiments are implemented by software, the electronic device 500 may also include only the processor 502. A memory 501 for storing programs is located outside the electronic device 500, and the processor 502 is connected to the memory via circuits / wires to read and execute the programs stored in the memory. The processor 502 may be a central processing unit (CPU), a network processor (NP), or a combination of a CPU and an NP. The processor 502 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0168] The memory 501 may include volatile memory, such as random-access memory (RAM); the memory may also include non-volatile memory, such as flash memory, hard disk drive (HDD) or solid-state drive (SSD); the memory may also include a combination of the above types of memory.

[0169] For example, this application provides a chip, including: an interface circuit and a logic circuit. The interface circuit is used to receive signals from other chips outside the chip and transmit them to the logic circuit, or to send signals from the logic circuit to other chips outside the chip. The logic circuit is used to perform operations performed by the control system in the above method embodiments.

[0170] For example, this application provides a computer-readable storage medium storing computer program instructions thereon, which are executed by the processor of an electronic device to cause the electronic device to perform the operations performed by the control system in the above method embodiments.

[0171] For example, this application provides a computer program product that, when run on an electronic device, causes the electronic device to perform the operations executed by the control system in the above method embodiments.

[0172] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a DC-DC step-down converter based on a composite fractional sliding surface, characterized in that, The method includes: Construct a nonlinear model of a DC-DC buck converter that includes constant power load characteristics; The nonlinear model is subjected to feedback linearization to obtain a linearized error model; Based on the linearized error model, the tracking error of the output voltage relative to the reference voltage is determined; Based on the tracking error, a first error region and a second error region are determined; Based on the first error region and the second error region, a composite phased sliding surface is constructed, the composite phased sliding surface including a first sliding surface corresponding to the first error region and a second sliding surface corresponding to the second error region; The control quantity of the DC-DC buck converter is determined based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law. Based on the control quantity, a pulse width modulation signal is generated to control the switching action of the DC-DC buck converter, thereby realizing closed-loop control of the DC-DC buck converter.

2. The method according to claim 1, characterized in that, The construction of the nonlinear model of the DC-DC buck converter, which includes constant power load characteristics, includes: In continuous conduction mode, the inductor current and output voltage are used as state variables, the duty cycle of the pulse width modulation control signal is used as the control input, and the state equation of the DC-DC buck converter is established by combining the input voltage, resistive load and constant power load. The output function of the DC-DC buck converter is determined based on the deviation between the output voltage and the reference voltage. Based on the state equation and the output function, a nonlinear model of a DC-DC buck converter incorporating constant power load characteristics is constructed.

3. The method according to claim 2, characterized in that, The step of performing feedback linearization on the nonlinear model to obtain a linearized error model includes: Using the output function as the first coordinate variable and the first derivative of the output function as the second coordinate variable, the coordinate transformation relationship is obtained; Specify new control input variables and establish a mapping relationship between the new control input variables and the control inputs; Based on the coordinate transformation and the mapping relationship, the nonlinear model is converted into a linearized error model.

4. The method according to claim 3, characterized in that, Determining the tracking error of the output voltage relative to the reference voltage based on the linearized error model includes: Based on the first coordinate variable and the second coordinate variable, a first error variable and a second error variable are determined, wherein the first error variable characterizes the tracking error of the output voltage relative to the reference voltage; The step of determining the first error region and the second error region based on the tracking error includes: Based on the comparison between the absolute value of the first error variable and the preset threshold, the first error region and the second error region are determined.

5. The method according to claim 4, characterized in that, The construction of a composite phased sliding surface based on the first error region and the second error region includes: A first sliding surface is constructed for the first error region; A second sliding surface is constructed for the second error region; The first sliding surface and the second sliding surface are combined to form the composite phased sliding surface.

6. The method according to claim 1, characterized in that, The power-law variable gain approach law includes a first approach term and a second approach term. The first approach term is used to accelerate system convergence under large error conditions, and the second approach term is used to suppress control chattering under small error conditions.

7. The method according to claim 6, characterized in that, The power-law variable gain approach law is expressed as follows: ; in, This represents the first approaching term. Indicates the second approaching term. This indicates a composite, phased sliding surface. .

8. The method according to claim 7, characterized in that, The step of determining the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law includes: The first control law is determined based on the first sliding surface and the power-law variable gain approach law; The second control law is determined based on the second sliding surface and the power-law variable gain approach law; Based on the error region to which the tracking error belongs, a target control law is selected from the first control law and the second control law; The target control law is mapped to a duty cycle control variable.

9. The method according to claim 8, characterized in that, The generation of the pulse width modulation signal based on the control quantity includes: The control quantity is compared with the triangular carrier signal to obtain the comparison result; The pulse width modulation signal is generated based on the comparison result.

10. A DC-DC buck converter control system based on a composite staged sliding mode surface, characterized in that, The system includes: The model building module is used to build a nonlinear model of a DC-DC buck converter that includes constant power load characteristics; The feedback linearization module is used to perform feedback linearization processing on the nonlinear model to obtain a linearized error model; An error determination module is used to determine the tracking error of the output voltage relative to the reference voltage based on the linearized error model. The region determination module is used to determine a first error region and a second error region based on the tracking error; A sliding surface construction module is used to construct a composite phased sliding surface based on the first error region and the second error region; The control quantity determination module is used to determine the control quantity of the DC-DC buck converter based on the error region to which the tracking error belongs, the sliding surface corresponding to the error region, and the power-law gain approximation law. The pulse width modulation signal generation module is used to generate a pulse width modulation signal based on the control quantity to control the switching action of the DC-DC buck converter and realize closed-loop control of the DC-DC buck converter.

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