A boost converter control method based on discrete sliding mode constraint attraction law

Abstract

This invention discloses a Boost converter control method based on a discrete sliding mode constraint attraction law, comprising the following steps: 1) establishing a discrete-time mathematical model of the Boost converter control system; 2) constructing a discrete sliding mode constraint attraction law based on a hyperbolic secant function; 3) designing a discrete-time sliding mode controller using the discrete sliding mode constraint attraction law, and using the calculated signal as the control input of the Boost converter. The Boost converter control method based on a discrete sliding mode constraint attraction law provided by this invention has constraint convergence and chatter suppression characteristics, while also improving the dynamic response performance and anti-interference capability of the Boost converter.

Description

Technical Field

[0001] This invention relates to a Boost converter control method based on discrete sliding mode constraint attraction law. This method is applicable to boost DC power supplies and also to DC-DC power supplies in industrial control. Background Technology

[0002] Boost converters, as a core component of switching power supplies, have been widely used in many fields such as industrial control, DC microgrids, computer systems, electric vehicles, and aerospace equipment. In actual operation, due to uncertainties such as sudden changes in external load, input voltage fluctuations, and changes in circuit parameters, traditional control methods often struggle to guarantee the robustness and dynamic response capability of the system in high-performance output voltage regulation.

[0003] Traditional Boost converter voltage control commonly employs linear proportional-integral (PI) control, which is widely used in engineering practice due to its simple structure, ease of implementation, and low dependence on the mathematical model of the controlled object. However, as a linear control strategy, the PI controller struggles to effectively handle complex situations such as time-varying system parameters, external disturbances, and model uncertainties. This can easily lead to problems such as large overshoot, continuous oscillation, or steady-state deviation in the output response, thus limiting its application in applications requiring high precision and high dynamic performance.

[0004] Sliding mode variable structure control, as a nonlinear control method, allows its structure to dynamically switch according to the system state, making it inherently compatible with inherently nonlinear variable structure systems like Boost converters. This method not only boasts fast response speed and strong robustness to parameter perturbations and external disturbances, but also features a relatively simple structure that is easy to implement. Therefore, it has been widely studied and applied in the controller design of Boost converters, resulting in a wealth of theoretical achievements. However, in practical engineering applications, sliding mode control still faces challenges such as chattering suppression and dynamic performance optimization. Furthermore, most existing research on sliding mode control for Boost converters is based on continuous-time system models, while actual digital control systems are inherently discrete-time systems, leading to differences in dynamic characteristics and control performance. Therefore, how to design a discrete sliding mode control strategy suitable for Boost converters and achieve a balance between chattering suppression and dynamic performance requires further in-depth research and improvement. Summary of the Invention

[0005] To overcome the shortcomings of existing control methods, such as limited dynamic response performance and anti-interference capability, and the fact that they are mainly based on continuous-time system model design, this invention provides a Boost converter control method based on discrete sliding mode constraint attraction law. The Boost converter digital control technology using discrete sliding mode constraint attraction law can achieve accurate reference signal tracking, significantly improving the system's dynamic response performance and anti-interference capability.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a Boost converter control method based on discrete sliding mode constraint attraction law, comprising the following steps:

[0007] Step 1: Establish the discrete-time mathematical model of the Boost converter control system

[0008] The discrete-time mathematical model of the Boost converter control system is established as follows:

[0009]

[0010] in, These represent the output voltages of the Boost converter at times k+1, k, and k-1, respectively. This represents the control input signal of the Boost converter at time k. R represents the switching cycle of the power switch, R, L, and C represent the load resistance, inductance, and capacitance of the Boost converter, respectively; and E represents the input voltage signal. The total system interference signal at time k+1;

[0011] Step 2: Construct a discrete sliding mode constraint attraction law based on hyperbolic secant functions.

[0012] Constructing a discrete sliding mode constraint attraction law based on hyperbolic secant functions

[0013]

[0014] in, Let $\frac{ ... Given a reference signal at time k, Let be the actual output voltage signal of the Boost converter at time k; the hyperbolic secant function is: When the tracking error is far from the origin, Approaching 0, that is and The tracking error tends towards 1 to avoid excessive rate of change of the tracking error, which could lead to control saturation, system overshoot, and poor response. When the tracking error approaches the origin, tending towards 1, that is Tend to and The convergence rate parameter of the tracking error approaches zero, reducing system chatter; the convergence rate parameter of the tracking error satisfies... The total system interference signal in equation (2) Calculated using historical data As a compensation quantity, it is embedded into the discrete sliding mode constraint attraction law (2) to achieve the system's anti-interference effect, and

[0015]

[0016] The rate of change of the total interference signal of the system is bounded and satisfies The convergence rate of the tracking error of the discrete sliding mode constraint attraction law (2) satisfies

[0017]

[0018] and

[0019]

[0020] The convergence speed of the tracking error is then limited to Within the range.

[0021] Step 3: Design a discrete-time sliding mode controller using the discrete sliding mode constraint attraction law.

[0022] Substituting equations (2) and (3) into equation (1), we obtain the expression for the discrete-time sliding mode controller of the Boost converter as follows:

[0023]

[0024] in,

[0025]

[0026] Will As the control input signal of the Boost converter, the voltage output signal of the Boost converter can be measured. Follow the reference signal The dynamic characteristics of the tracking error of the Boost converter are characterized by Equation (2).

[0027] Furthermore, to characterize the convergence and steady-state performance of the discrete sliding mode constraint attraction law, this invention provides expressions for two indices: the absolute attraction layer boundary and the steady-state error band boundary. These two indices can be used to guide controller parameter tuning, wherein the absolute attraction layer boundary and the steady-state error band boundary are defined as follows:

[0028] 1) Absolute attraction layer boundary

[0029]

[0030] 2) Steady-state error band boundary

[0031]

[0032] here, For the boundary of the absolute attraction layer, This represents the boundary of the steady-state error band. The expressions for its various indices are as follows:

[0033] 1) Absolute attraction layer boundary Represented as:

[0034]

[0035] In the formula, , It is a positive real number and satisfies

[0036]

[0037] 2) Steady-state error band boundary Represented as:

[0038]

[0039] In the formula, , It is a positive real number and satisfies

[0040]

[0041] in This is the upper bound of the interference compensation error.

[0042] The technical concept of this invention is as follows: a Boost converter control method based on a discrete sliding mode constraint attraction law. This method embeds a hyperbolic secant function into the attraction law to construct a discrete sliding mode constraint attraction law. Based on this discrete sliding mode constraint attraction law, a discrete-time sliding mode controller for the Boost converter is designed to achieve accurate tracking of a given reference signal, thereby improving the dynamic response performance and anti-interference capability of the Boost converter.

[0043] The control effect of this invention is mainly reflected in the following aspects: by adopting a discrete sliding mode constraint attraction law based on hyperbolic secant function, constraint convergence and system chattering are achieved, resulting in better control performance and anti-interference ability of the system. Attached Figure Description

[0044] Figure 1 This is a flowchart of the Boost converter control method.

[0045] Figure 2 This is a schematic diagram of the circuit structure of a Boost converter.

[0046] Figure 3 This is a block diagram of the discrete-time sliding mode controller for a Boost converter.

[0047] Figure 4 This is the startup response diagram of the discrete-time sliding mode controller and PI controller of the Boost converter.

[0048] Figure 5 It refers to the output voltage ripple of the discrete-time sliding mode controller and PI controller of the Boost converter.

[0049] Figure 6 Under conditions of sudden input voltage changes, the output voltage signal is based on a discrete-time sliding mode controller and a PI controller. .

[0050] Figure 7 Under conditions of sudden input voltage changes, the output voltage is determined using a discrete-time sliding mode controller and a PI controller. Fluctuations.

[0051] Figure 8 In the case of tracking changes in target voltage output, the output voltage signal based on a discrete sliding mode controller and a PI controller is used. .

[0052] Figure 9 Under conditions of sudden load changes, the output voltage signal based on a discrete sliding mode controller and a PI controller is used. .

[0053] Figure 10 Under conditions of sudden load changes, the output voltage is based on a discrete sliding mode controller and a PI controller. Fluctuations. Detailed Implementation

[0054] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0055] Reference Figure 1-10 A control method for a Boost converter based on discrete sliding mode constraint attraction law, such as... Figure 1 As shown, it includes the following steps:

[0056] Step (1): Establish the mathematical model of the Boost converter control system

[0057] Figure 2 This is a schematic diagram of the circuit structure of a Boost converter, where DC input voltage; For power switching transistors; A diode; R, L, and C are the load resistor, inductor, and capacitor of the Boost converter, respectively. It is the inductor current; Let be the voltage across the capacitor. According to Kirchhoff's voltage and current laws, the models of the Boost converter control system when the switch is closed and open are as follows:

[0058] a) Switch closed:

[0059]

[0060] b) Switch off:

[0061]

[0062] The average mathematical model is then:

[0063]

[0064] in, The duty cycle is provided as a control signal by a pulse bandwidth modulation signal. From equation (3), the following voltage equation can be obtained:

[0065]

[0066] Using the Euler approximation method, Equation (4) becomes

[0067]

[0068] in, Let be the discrete system output voltage of the Boost converter at times k+1, k, and k-1. This represents the control input signal of the Boost converter at time k. R represents the switching cycle of the power switch, and R, L, and C represent the load resistance, inductance, and capacitance of the Boost converter, respectively. The input voltage signal; This represents discrete error.

[0069] Considering the uncertainties and measurement errors in R, L, and C of the Boost converter system, the second-order input-output system model of the Boost converter becomes...

[0070]

[0071] in, The measurement errors of R, L, C, and E are respectively. The mathematical model of the Boost converter is obtained from equation (6):

[0072]

[0073] in, The total interference signal of the system at time k+1 is expressed as follows:

[0074]

[0075] Step (2): Construct a discrete sliding mode constraint attraction law based on hyperbolic secant function.

[0076] Constructing a discrete sliding mode constraint attraction law based on hyperbolic secant functions

[0077]

[0078] in, Let $\frac{ ... Given a reference signal at time k, Let be the actual output voltage signal of the Boost converter at time k; the hyperbolic secant function is: When the tracking error is far from the origin, Approaching 0, that is and The tracking error tends towards 1 to avoid excessive rate of change of the tracking error, which could lead to control saturation, system overshoot, and poor response. When the tracking error approaches the origin, tending towards 1, that is Tend to and The convergence rate parameter of the tracking error approaches zero, reducing system chatter; the convergence rate parameter of the tracking error satisfies... The total system interference signal in equation (7) Calculated using historical data As a compensation quantity, it is embedded into the discrete sliding mode constraint attraction law (9) to achieve the system's anti-interference effect, and

[0079]

[0080] The rate of change of the total interference signal of the system is bounded and satisfies The convergence rate of the tracking error of the discrete sliding mode constraint attraction law (9) satisfies

[0081]

[0082] and

[0083]

[0084] The convergence speed of the tracking error is then limited to Within the range.

[0085] Step (3): Design a discrete-time sliding mode controller using the discrete sliding mode constraint attraction law.

[0086] Substituting equations (9) and (10) into equation (7), we obtain the expression for the discrete-time sliding mode controller of the Boost converter as follows:

[0087]

[0088] in,

[0089]

[0090] Will As the control input signal of the Boost converter, the voltage output signal of the Boost converter can be measured. Follow the reference signal The dynamic characteristics of the tracking error of the Boost converter are characterized by Equation (9).

[0091] Furthermore, to characterize the convergence and steady-state performance of the discrete sliding mode constraint attraction law, this invention provides expressions for two indices: the absolute attraction layer boundary and the steady-state error band boundary. These two indices can be used to guide controller parameter tuning, wherein the absolute attraction layer boundary and the steady-state error band boundary are defined as follows:

[0092] 1) Absolute attraction layer boundary

[0093]

[0094] 2) Steady-state error band boundary

[0095]

[0096] here, For the boundary of the absolute attraction layer, This represents the boundary of the steady-state error band. The expressions for its various indices are as follows:

[0097] 1) Absolute attraction layer boundary Represented as:

[0098]

[0099] In the formula, , It is a positive real number and satisfies

[0100]

[0101] 2) Steady-state error band boundary Represented as:

[0102]

[0103] In the formula, , It is a positive real number and satisfies

[0104]

[0105] in This is the upper bound of the interference compensation error.

[0106] Furthermore, after designing the discrete-time sliding mode controller for the Boost converter, the controller parameters need to be tuned. Adjustable parameters... The tuning is performed based on two indices characterizing the convergence process of the discrete sliding mode constraint attraction law.

[0107] Example

[0108] The Boost converter uses the switching on and off of transistors to control the magnitude and direction of energy flow, based on high-frequency PWM modulation. To achieve high-precision closed-loop voltage control, the system acquires the output voltage signal in real time. and compare it with the given reference signal By comparing the generated tracking error signal, and based on the circuit parameters of the Boost converter (resistance R, inductance L, capacitance C, input voltage E) and the sampling period T, a system dynamic model in the discrete domain is derived, and the disturbance compensation term is calculated. Combined with preset control parameters, a nonlinear control algorithm is used to calculate the error signal and the disturbance compensation term, thereby correcting the duty cycle of the PWM wave. This control strategy can accurately track the reference voltage, effectively suppress disturbances caused by load changes, input voltage fluctuations, and system nonlinear characteristics, and achieve high-performance, precise control of the Boost converter output voltage.

[0109] The following describes the design process of the discrete-time controller for the Boost converter.

[0110] First, a mathematical model of the Boost converter control system is established. Figure 2 The main control circuit, sampling circuit, and low-pass filter of the Boost converter are used as objects for mechanism modeling, and the switching period of the power switch is... load resistance ,inductance ,capacitance Control cycle Input voltage Given a reference signal The discrete-time PI controller is:

[0111]

[0112] This embodiment will use Matlab Simulink numerical verification to demonstrate the effectiveness and superiority of the discrete-time sliding mode controller design method presented in this invention.

[0113] The block diagram of the discrete-time sliding mode controller of the Boost converter used in the numerical simulation experiment is as follows: Figure 3 As shown, this invention is used to verify the effectiveness and superiority of the discrete-time sliding mode controller design method in the context of startup response, input voltage mutation, tracking target output voltage change, and load mutation.

[0114] (1) Startup response scenario

[0115] Input voltage Keeping constant, the output voltage tracks the target value. Under the action of the discrete-time sliding mode controller (13) designed by the discrete sliding mode constraint attraction law, the controller parameters are selected as follows: Under the action of the discrete PI controller (21), the controller parameters are selected as follows: The experimental results are shown in [the table]. Figure 4 and Figure 5 .from Figure 4 These two output voltage curves provide a direct comparison of the response characteristics of sliding mode control and PI control: sliding mode control exhibits an extremely fast response speed, with the voltage transitioning from the initial 100V to the target value of 200V in a very short time (far less than 0.05s). In contrast, PI control has a relatively slow response, with a longer transition time from 100V to 200V (approximately 0.1s to approach the target). Figure 5 It can be seen that after the sliding mode control reaches steady state, the voltage fluctuates slightly between 199.8 and 200.2 V, with a ripple range of approximately 0.4 V. Similarly, after the PI control reaches steady state, the voltage also fluctuates within the 199.8 to 200.2 V range. Figure 4 and Figure 5 It can be seen that the steady-state ripple amplitude range of the discrete-time sliding mode controller (13) and the discrete-time PI controller (21) proposed in this invention is similar, but the response time of the discrete-time sliding mode controller (13) is significantly shorter than that of the discrete-time PI controller (21).

[0116] (2) Input voltage sudden change situation

[0117] Output voltage The input voltage setpoint remains unchanged, changing at 0.25s. Mutation to Other parameters remain unchanged. Under the action of the discrete-time sliding mode controller (13) designed by the discrete sliding mode constraint attraction law, the controller parameters are selected as follows: Under the action of the discrete PI controller (21), the controller parameters are selected as follows: The experimental results are shown in [the table]. Figure 6 and Figure 7 After a sudden change in input voltage, the sliding mode control output exhibits a brief, small fluctuation (a spike of approximately 1V occurs around 0.25s), then quickly returns to the target voltage of around 200V and stabilizes again. The overall fluctuation is extremely short in duration and small in amplitude, demonstrating a fast disturbance rejection response. In contrast, the PI control output shows a significant overshoot, followed by a slow recovery. The process of restoring to around 200V takes a longer time, with a larger overall fluctuation amplitude and slower recovery speed, indicating weaker disturbance rejection performance. Figure 6 and Figure 7 It can be concluded that, when dealing with input disturbances, the time for the discrete-time sliding mode controller (13) proposed in this invention to complete voltage adjustment is much shorter than that for the discrete-time PI controller (21).

[0118] (3) Tracking the changes in the target output voltage

[0119] Input voltage The output voltage remains constant, tracking the target value at 0.25s. Mutation to Other parameters remain unchanged. Under the action of the discrete-time sliding mode controller (13) designed by the discrete sliding mode constraint attraction law, the controller parameters are selected as follows: Under the action of the discrete PI controller (21), the controller parameters are selected as follows: The experimental results are shown in [the table]. Figure 8 During the output voltage jump from 200V to 220V, sliding mode control tracks the voltage change extremely quickly, responding instantaneously with a response time of approximately 3ms. PI control, on the other hand, has a longer adjustment time and cannot quickly track sudden voltage changes, with a response time of approximately 100ms. Figure 8 It can be seen that the discrete-time sliding mode controller (13) proposed in this invention can achieve a faster response speed than the discrete-time PI controller (21).

[0120] (4) Sudden load changes

[0121] Input voltage Keeping constant, the output voltage tracks the target value. The load resistance changes at 0.25s. Mutation to All other parameters remain unchanged. The input voltage Vin = 100V remains constant, and the output voltage tracks the target value. Under the action of the discrete-time sliding mode controller (13) designed by the discrete sliding mode constraint attraction law, the controller parameters are selected as follows: Under the action of the discrete PI controller (21), the controller parameters are selected as follows: The experimental results are shown in [the table]. Figure 9 and Figure 10 When the load resistance is determined by Mutation to During the process, the output voltage of the sliding mode control showed almost no fluctuation, exhibiting extremely strong resistance to load disturbances and instantly suppressing the effects of sudden load changes. The output voltage of the PI control, however, showed significant transient fluctuations, requiring a period of adjustment to stabilize. Figure 9 It can be seen that the rise time of the sliding mode control output voltage is approximately 2ms and the fall time is approximately 3ms, while the rise time of the PI control output voltage is approximately 40ms and the fall time is approximately 60ms. Figure 9 and 10 It can be seen that the discrete-time sliding mode controller (13) proposed in this invention has a faster load adjustment response speed and better dynamic disturbance rejection performance than the discrete-time PI controller (21).

Claims

1. A control method for a Boost converter based on a discrete sliding mode constraint attraction law, characterized in that, Includes the following steps: Step 1: Establish the discrete-time mathematical model of the Boost converter control system The discrete-time mathematical model of the Boost converter control system is established as follows: in, These represent the output voltages of the Boost converter at times k+1, k, and k-1, respectively. This represents the control input signal of the Boost converter at time k. R represents the switching cycle of the power switch, R, L, and C represent the load resistance, inductance, and capacitance of the Boost converter, respectively; and E represents the input voltage signal. The total interference signal of the system at time k+1; Step 2: Construct a discrete sliding mode constraint attraction law based on hyperbolic secant functions. Constructing a discrete sliding mode constraint attraction law based on hyperbolic secant functions in, Let $\frac{ ... Given a reference signal at time k, Let be the actual output voltage signal of the Boost converter at time k; the hyperbolic secant function is: When the tracking error is far from the origin, Approaching 0, that is and The tracking error tends towards 1 to avoid excessive rate of change of the tracking error, which could lead to control saturation, system overshoot, and poor response. When the tracking error approaches the origin, tending towards 1, that is Tend to and The convergence rate parameter of the tracking error approaches zero, reducing system chatter; the convergence rate parameter of the tracking error satisfies... The total system interference signal in equation (2) Calculated using historical data As a compensation quantity, it is embedded into the discrete sliding mode constraint attraction law (2) to achieve the system's anti-interference effect, and The rate of change of the total interference signal of the system is bounded and satisfies The convergence rate of the tracking error of the discrete sliding mode constraint attraction law (2) satisfies and The convergence speed of the tracking error is then limited to Within the range; Step 3: Design a discrete-time sliding mode controller using the discrete sliding mode constraint attraction law. Substituting equations (2) and (3) into equation (1), we obtain the expression for the discrete-time sliding mode controller of the Boost converter as follows: in, Will As the control input signal of the Boost converter, the voltage output signal of the Boost converter can be measured. Follow the reference signal The dynamic characteristics of the tracking error of the Boost converter are characterized by equation (2).

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