Adaptive second-order sliding mode voltage control method for buck converter

Abstract

The application relates to the technical field of Buck converters, in particular to a Buck converter voltage control method based on adaptive second-order sliding mode, which comprises the following steps: a Buck converter mathematical model is established, a voltage error is taken as a sliding mode variable, and a second-order sliding mode dynamics equation is derived; a sliding mode filter based on a Levant differentiator structure is constructed; an equivalent control corresponding switch average signal is identified online by using the sliding mode filter; a variable gain adaptive law is constructed based on an equivalent control principle, control gain is realized to follow a lumped uncertainty finite time adaptive setting; an adaptive parameter second-order sliding mode controller is designed by combining a power integral backstepping, a PWM driving signal is generated after output limiting, and Buck converter output voltage stabilizing control is completed. The application solves the problems that the existing Buck converter has high power consumption, serious chattering, poor disturbance adaptability and limited energy-saving effect.

Description

Technical Field

[0001] This invention relates to the field of Buck converter technology, and more particularly to an adaptive second-order sliding mode Buck converter voltage control method. Background Technology

[0002] Under the guidance of energy conservation and efficiency improvement policies, the high efficiency and low carbon emissions of power electronic devices have become a rigid requirement for industrial development. Buck step-down converters are widely used in new energy vehicle power supplies, industrial servo power supplies, airborne power supplies and precision chip power supplies. Their control performance directly determines the power conversion loss. Optimizing control strategies and reducing useless power consumption are key to achieving green energy conservation in power supplies. As electrical equipment becomes increasingly high-frequency and integrated, load jumps, input voltage fluctuations, and component temperature drift parameter perturbations have become the norm. The industry has set higher standards for the voltage regulation accuracy, dynamic response and energy-saving level of converters.

[0003] Currently, the mainstream control schemes for Buck converters in engineering are PI control and fixed-parameter second-order sliding mode control. However, all control schemes have inherent defects in energy saving and disturbance rejection performance. Conventional PI controllers have weak robustness, and when faced with parameter drift and load changes, the voltage drop is large and the dynamic recovery is slow. During the regulation phase, power switches frequently and abnormally switch, resulting in a large amount of additional switching losses and low power conversion efficiency, which does not meet the requirements of low-carbon and energy-saving development. Traditional fixed-gain second-order sliding mode controllers must conservatively select excessively large fixed gains to cover unknown disturbances under all operating conditions. Excessive gains will cause serious control chattering, leading to increased heat loss of inductors and capacitors and shortening the service life of power devices. When light load disturbances are small, redundant gains continue to cause energy waste, while under heavy load disturbances, there are problems of insufficient gain and decreased voltage regulation accuracy, making it difficult to balance energy efficiency and control accuracy under all operating conditions. Summary of the Invention

[0004] To address the shortcomings of existing methods, particularly the high power consumption, severe chattering, poor disturbance adaptability, and limited energy-saving effects of Buck converters, this invention replaces traditional low-pass filtering with sliding mode filtering to eliminate parameter selection constraints. It utilizes an adaptive variable gain strategy based on equivalent control design to achieve real-time control gain that follows lumped disturbances, thereby suppressing chattering and reducing ineffective energy consumption at the source. While ensuring system stability for a limited time, this improves the converter's voltage regulation performance and energy utilization efficiency, aligning with the needs of green power supply and low-carbon applications.

[0005] The technical solution adopted in this invention is: an adaptive second-order sliding mode Buck converter voltage control method comprising the following steps: Step 1: Establish a mathematical model of the Buck converter, using voltage error as the sliding mode variable, and derive the second-order sliding mode dynamic equation; Step 2: Construct a sliding model filter based on the Levant differentiator structure, and use the sliding model filter to identify the equivalent control switching average signal online; In a preferred embodiment of the present invention, the formula for the sliding model filter is: (4) Among them, the sign function ; ; Positive design parameters for the filter; This is a constant representing the upper bound of the second derivative of the average switching signal; Output the internal variables of the global error residual; For limited time tracking ; To track .

[0006] As a preferred embodiment of the present invention λ 0 = 1.1, λ 1 = 1.5 λ 2=2, L 1 = 1500.

[0007] Step 3: Construct a variable gain adaptive law based on the equivalent control principle to achieve finite-time adaptive tuning of the control gain following the lumped uncertainty; In a preferred embodiment of the present invention, the formula for the variable gain adaptive law is: (5) in, , These are adaptive coefficients; , A, G They are respectively , The upper bound; k 1, k 2 represents the adaptive gain. k ( t The lower and upper limits of ) ; For selection.

[0008] As a preferred embodiment of the present invention γ =1, K =30, k 1 = 0.6 k 2 = 10 v =0.9.

[0009] Step 4: Combine power-integral backstepping to design an adaptive parameter second-order sliding mode controller, and generate a PWM drive signal after output limiting to complete the output voltage regulation control of the Buck converter. In a preferred embodiment of the present invention, the formula for the adaptive parameter second-order sliding mode controller is: (6) Among them, the sign function , β 1 represents a fixed positive design parameter. β 2 represents the controller gain parameter.

[0010] As a preferred embodiment of the present invention β 1 = 4.

[0011] As a preferred embodiment of the present invention, an adaptive second-order sliding mode Buck converter voltage control system includes: a memory for storing instructions executable by a processor; and a processor for executing the instructions to implement an adaptive second-order sliding mode Buck converter voltage control method.

[0012] As a preferred embodiment of the present invention, a computer-readable medium storing computer program code implements an adaptive second-order sliding mode Buck converter voltage control method when executed by a processor.

[0013] The beneficial effects of this invention are: 1. This invention uses a sliding model filter to replace the traditional low-pass filter, which removes the limitation of the filter constant being constrained by the sampling period during equivalent control identification, resulting in higher accuracy of equivalent disturbance identification.

[0014] 2. The adaptive gain follows the real-time changes of the system's lumped disturbance, without the need to know the upper limit of the disturbance in advance. This avoids the gain overestimation problem of traditional fixed-gain second-order sliding mode, significantly reduces high-frequency jitter in control, reduces switching losses, improves the power utilization of the converter, and meets the requirements of energy-saving control.

[0015] 3. The controller achieves finite-time convergence of the closed-loop system based on power integration, which has a fast convergence speed and strong robustness to load jumps, input voltage fluctuations, and device parameter drift. The steady-state voltage regulation error is small. The adaptive law sets upper and lower limit constraints on the gain to ensure that the adaptive gain is always bounded, avoiding the controller saturation caused by the infinite increase of the gain. It has strong engineering feasibility. Attached Figure Description

[0016] Figure 1 This is a block diagram of the adaptive second-order sliding mode Buck converter voltage control system of the present invention; Figure 2 This is a comparison chart of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the startup phase. Figure 3This is a comparison chart of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the variable load stage (when the load increases). Figure 4 This is a comparison chart of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the variable load stage (when the load decreases). Figure 5 This is a comparison chart of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the transformer stage (when the input voltage increases). Figure 6 This is a comparison chart of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the transformer stage (when the input voltage decreases). Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0018] like Figure 1 As shown, an adaptive second-order sliding mode Buck converter voltage control method includes the following steps: The Buck circuit output voltage control system consists of a DC regulated power supply, a Buck circuit module, a main controller module, a sampling circuit module, and a drive circuit module. The DC regulated power supply is used to provide a stable input voltage; The Buck circuit module achieves step-down conversion through internal resistors, capacitors, inductors, and power switches, and outputs a stable voltage to the load. The main controller module is used to receive feedback signals from the sampling circuit module, execute control algorithms, and output control commands; The sampling circuit module obtains the output voltage of the Buck circuit module through AD sampling and feeds it back to the main controller module to form a closed-loop control. The drive circuit module is used to convert the PWM wave signal into a power switch drive voltage signal to control the power switch's on and off states.

[0019] Based on the above system, the specific implementation of the present invention will be described below through a set of specific parameters of the Buck circuit and experimental results.

[0020] The parameters of the Buck circuit module in the experiment are shown in Table 1.

[0021] Table 1 Buck Circuit Parameters Based on the Buck circuit parameters given in Table 1, the mathematical model of the Buck converter is established using the spatial state averaging method as follows: (1) in, L For inductance, C For capacitors, R For load, i L For inductor current, v o For output voltage, u Control duty cycle input.

[0022] The sliding mode variable is represented as: (2) in, v ref This is the reference voltage.

[0023] The derivative transformation yields the second-order sliding mode dynamics equation, which is expressed as: (3) in, For the system's lumped uncertainty term, t For time, To control the gain term, satisfying , , It is a constant.

[0024] The sliding model filter structure is established as follows: (4) Among them, the sign function , , For the positive design parameters of the filter, The upper bound constant of the second derivative of the average switching signal; filter output Output the internal variables of the global error residual; For limited time tracking (Equivalent average value of switching function) To track .

[0025] The traditional low-pass filter expression proposed in "Adaptive sliding mode control with application to super-twistalgorithm: Equivalent control method, doi:10.1016 / j.automatica.2012.09.008" is as follows: The sliding mode filter expression proposed in "Sliding-mode-based differentiation and filtering, doi:10.1109 / TAC.2018.2797218" is as follows: Compared with traditional low-pass filter design, the sliding mode filter proposed in this invention no longer has the inherent defect of mutual constraint between the filtering time constant and the system sampling period, thus avoiding the parameter constraint problem of linear low-pass filters. Compared with existing sliding mode filter design, it solves the problem of only matching relative degree 1, enabling it to match sliding mode with relative degree 2, and establishes a mapping relationship between the filter mean and the lumped disturbance based on second-order sliding mode dynamics.

[0026] The expression for the variable gain adaptive law is: (5) in, , For adaptive coefficients, , A, G They are respectively , The upper bound; k 1, k 2 represents the adaptive gain. k ( t The lower and upper limits of ) And it approaches 1; The selection function takes the value 1 when x≥0 and the value 0 when x<0; adaptive gain. k ( t Convergence in finite time to This is the lumped disturbance of the system.

[0027] Finally, the adaptive parameter second-order sliding mode controller based on the sliding mode filter is constructed as follows: (6) Among them, the sign function , β 1 represents a fixed positive design parameter. β 2 represents the controller gain parameter, and its value corresponds to... Integrating, we can obtain that the variable gain adaptive law updates in real time, changing with the magnitude of the disturbance.

[0028] The controller proposed in "Second-order sliding-mode controller design and its implementation for buck converters, doi: 10.1109 / TII.2017.2758263." is expressed as follows: Compared with existing fixed-parameter second-order sliding mode controllers, the adaptive parameter controller based on sliding mode filter proposed in this invention adds an adaptive law about the parameters, enabling the control gain to follow the real-time changes of lumped disturbances, thereby improving control efficiency, reducing losses, and avoiding the negative effects of excessive gain.

[0029] Experimental procedure: The parameters used for the sliding mode filter are as follows: λ 0 = 1.1, λ 1 = 1.5 λ 2=2, which satisfies the condition. λ 0, λ 1, λ 2>0, L 1 =1500; The parameters used for the adaptive law are: γ =1, K =30, k 1 = 0.6 k 2 = 10 v =0.9; The parameters used for the adaptive parameter second-order sliding mode controller are: β 1=4; Controller in existing technology α =10, β =4 。

[0030] Finally, closed-loop control is implemented on the Buck circuit. The sampling circuit acquires the output voltage and inductor current, and calculates the sliding mode variable. s The first derivative of the sliding mode variable is used; the acquired switch state signal is input into the sliding mode filter to extract the equivalent average switch signal, and the adaptive law related state variables are calculated by combining the filtered output. k ( t Real-time iterative updates of variable gain β 2( t Finally, the adaptive parameter second-order sliding mode controller on the main control module outputs the control quantity u, which is limited to [0,1] to generate a PWM signal. The MOSFET drive module controls the Buck switch to ensure that the output voltage and inductor current converge to the target steady-state value within a finite time.

[0031] Figure 2This is a comparison diagram of the control effects of the adaptive parameter second-order sliding mode controller and the fixed parameter second-order sliding mode controller during the startup phase of the present invention; Figure 3 and Figure 4 A comparison of the control performance of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the variable load stage; Figure 5 and Figure 6 A comparison of the control effects of an adaptive parameter second-order sliding mode controller and a fixed parameter second-order sliding mode controller during the transformer stage.

[0032] The experimental results show that, overall, the adaptive parameter second-order sliding mode controller has a shorter start-up time, less voltage overshoot and drop during load and voltage transformation stages, and a faster recovery time compared to the fixed parameter sliding mode controller.

[0033] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An adaptive second-order sliding mode voltage control method for a Buck converter, characterized in that, Includes the following steps: Step 1: Establish a mathematical model of the Buck converter, using voltage error as the sliding mode variable, and derive the second-order sliding mode dynamic equation; Step 2: Construct a sliding model filter based on the Levant differentiator structure, and use the sliding model filter to identify the equivalent control switching average signal online; Step 3: Construct a variable gain adaptive law based on the equivalent control principle to achieve finite-time adaptive tuning of the control gain following the lumped uncertainty; Step 4: Combine power-integral backstepping to design an adaptive parameter second-order sliding mode controller, and generate a PWM drive signal after output limiting to complete the output voltage regulation control of the Buck converter.

2. The adaptive second-order sliding mode Buck converter voltage control method according to claim 1, characterized in that, The formula for the sliding model filter is: ； Among them, the sign function ; ; Positive design parameters for the filter; This is a constant representing the upper bound of the second derivative of the average switching signal; Output the internal variables of the global error residual; For limited time tracking ; To track .

3. The adaptive second-order sliding mode Buck converter voltage control method according to claim 1, characterized in that, The formula for the variable gain adaptive law is: ； in, , These are adaptive coefficients; , A, G They are respectively , The upper bound; k 1, k 2 represents the adaptive gain. k ( t The lower and upper limits of ) ; For selection.

4. The adaptive second-order sliding mode Buck converter voltage control method according to claim 1, characterized in that, The formula for an adaptive parameter second-order sliding mode controller is: ； Among them, the sign function , β 1 represents a fixed positive design parameter. β 2 represents the controller gain parameter.

5. The adaptive second-order sliding mode Buck converter voltage control method according to claim 2, characterized in that, λ 0=1.1， λ 1=1.5， λ 2=2， L 1=1500。 6. The adaptive second-order sliding mode Buck converter voltage control method according to claim 3, characterized in that, γ =1， K =30， k 1=0.6， k 2=10， v =0.9。 7. The adaptive second-order sliding mode Buck converter voltage control method according to claim 4, characterized in that, β 1=4。 8. An adaptive second-order sliding mode Buck converter voltage control system, characterized in that, include: Memory is used to store instructions that can be executed by the processor; A processor for executing instructions to implement the adaptive second-order sliding mode Buck converter voltage control method as described in any one of claims 1-7.

9. A computer-readable medium storing computer program code, characterized in that, The computer program code, when executed by a processor, implements the adaptive second-order sliding mode Buck converter voltage control method as described in any one of claims 1-7.

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