Active-disturbance-rejection control method and system for three-level LLC converter

Abstract

The invention provides an active-disturbance-rejection control method and system for a three-level LLC converter, and the method comprises the steps: collecting the voltage of a load end of the three-level LLC converter, and calculating a voltage error and an error change rate through the combination of the voltage of the load end and a reference voltage; fuzzy control is adopted to adjust a fractional order parameter and a differential order of the fractional order linear active disturbance rejection controller; inputting the voltage error and the error change rate into a fractional order linear active disturbance rejection controller, and outputting a given current signal; calculating a current error according to the given current signal and the reference current signal; and inputting the current error to a PI controller to output a PWM signal. The technical problem that ideal control performance is difficult to obtain due to the fact that the output stability, dynamic response and robustness of the converter are easily affected by external interference of the three-level LLC converter and changes of internal parameters of a circuit is solved.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically, to an active disturbance rejection control method and an active disturbance rejection control system for a three-level LLC converter. Background Technology

[0002] Three-level LLC converters, as a type of high-efficiency isolated DC-DC converters, offer advantages such as halved switching voltage stress, high conversion efficiency, soft-switching characteristics, and low electromagnetic interference, making them widely used in new energy power generation, industrial power supplies, data centers, and communication equipment. However, as the core of high-efficiency power conversion, three-level LLC converters face challenges from highly nonlinear systems in practical applications. External interference and changes in internal circuit parameters can easily affect the converter's output stability, dynamic response, and robustness, making it difficult to achieve ideal control performance.

[0003] However, the relevant technologies have at least one of the following problems: as the core of efficient power conversion, the three-level LLC converter faces the challenge of strong nonlinear systems in practical applications. External interference and changes in internal circuit parameters can easily affect the output stability, dynamic response and robustness of the converter, making it difficult to obtain ideal control performance. Summary of the Invention

[0004] This invention addresses the technical problem that external interference and changes in internal circuit parameters of a three-level LLC converter can easily affect the converter's output stability, dynamic response, and robustness, making it difficult to achieve ideal control performance.

[0005] To address the aforementioned problems, this invention provides an active disturbance rejection control method for a three-level LLC converter, comprising: acquiring the load terminal voltage of the three-level LLC converter, and calculating the voltage error and error rate of change by combining the load terminal voltage and a reference voltage; and employing fuzzy control to control the fractional-order parameters of the fractional-order linear active disturbance rejection controller. , and differential order Adjustments are made; the voltage error and the rate of change of error are input to the fractional-order linear active disturbance rejection controller, and a given current signal is output; the current error is calculated based on the given current signal and the reference current signal; the current error is input to the PI controller to output a PWM signal.

[0006] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: The active disturbance rejection control method of this invention is applied to the voltage closed-loop control of a three-level LLC converter; a fractional-order linear state error feedback control law is used to replace the traditional linear state error feedback control law in linear active disturbance rejection, and fuzzy control is used to control the fractional-order parameters. , and differential order Adjustments are made to further improve the dynamic response speed and anti-disturbance capability when facing internal circuit parameters and external interference, thereby achieving synergistic optimization of the anti-disturbance capability and dynamic performance of the three-level LLC converter.

[0007] In one embodiment of the present invention, the fractional-order linear active disturbance rejection controller includes a linear extended state observer and a fractional-order linear state error feedback control law; the expression of the linear extended state observer is: ;in, denoted as the load output voltage, b as the control gain, and u as the control input. This is the load terminal voltage. Differentiate the load voltage. For total disturbance; This is the observed voltage value at the load end. The output voltage differential observation value, This represents the total disturbance observations; , and All are the gains of the linearly extended state observer.

[0008] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: The total system disturbance f includes internal and external disturbances. Internal disturbances can be resonant parameter drift and changes in switching transistor conduction losses; external disturbances can be input voltage fluctuations and load current abrupt changes. The Linear Extended State Observer (LESO) introduces a compensation term into the control quantity by observing the total system disturbance in real time, thereby achieving disturbance feedforward suppression. By combining feedforward compensation and feedback regulation, dual suppression of internal and external disturbances is achieved.

[0009] In one embodiment of the present invention, the expression for the fractional-order linear state error feedback control law is as follows: , ;in, Here, is the control quantity before disturbance compensation; e is the voltage error. , These are the proportional gain coefficient and the differential gain coefficient, respectively, in the fractional-order parameters. For the Laplace operator.

[0010] Compared with existing technologies, the technical effects achieved by adopting this technical solution are as follows: In LESF, a PD controller is used, and a fractional-order linear state error feedback control law is used to replace the PD controller.

[0011] In one embodiment of the present invention, , , ; , ;in, For the bandwidth of the linearly extended state observer, Let be the bandwidth of the fractional-order linear state error feedback control law.

[0012] Compared with existing technologies, the technical effects achieved by this solution are as follows: It can be seen that the parameters of linear active disturbance rejection are only related to the bandwidth of the linearly extended state observer. Bandwidth of fractional-order linear state error feedback control law The two parameters are related, which greatly simplifies the parameter tuning process.

[0013] In one embodiment of the invention, the Laplacian operator is applied using an Oustaloup filter. After discretization, the basic model of the Oustaloup filter is as follows: Where K represents gain; The frequency representing the turning point of the k-th pole. The turning frequency represents the k-th zero point.

[0014] Compared with existing technologies, the technical effects achieved by this solution are as follows: For fractional-order lattice Laplace operators, the Oustaloup method is used. The Laplace operator is approximated using integer-order differential operators. .

[0015] In one embodiment of the present invention, fuzzy control of a fractional-order linear active disturbance rejection controller is achieved using a variable universe fuzzy controller; fuzzy control is employed to control the fractional-order parameters of the fractional-order linear active disturbance rejection controller. , and differential order The adjustment process includes: inputting the voltage error and error rate of change into a variable universe of discourse fuzzy controller; performing fuzzy universe of discourse processing on the voltage error and error rate of change according to fuzzy rules; and outputting a fractional-order increment. , and differential order increment The fractional-order parameter is adjusted by the fractional-order increment, and the differential-order is adjusted by the differential-order increment.

[0016] Compared with existing technologies, the technical effects achieved by this solution are: introducing fuzzy control to realize fractional-order parameters. , and differential order Its adaptive adjustment eliminates the need for manual tuning, achieving an innovative parameter adjustment mechanism.

[0017] In one embodiment of the present invention, the fuzzy rules use seven fuzzy subsets, NB, NM, NS, ZO, PS, PM, and PB, to adjust the fractional order parameter and the differential order.

[0018] Compared with existing technologies, the technical effects achieved by adopting this technical solution are as follows: The fuzzy subsets are set into 7 subsets based on the voltage error e and the error change rate ec, namely NB, NM, NS, ZO, PS, PM, and PB, which correspond to negative large, negative small, zero, positive small, positive medium, and positive large, respectively.

[0019] In one embodiment of the present invention, the variable universe fuzzy controller selects a triangular membership function to describe the fuzzy subset; the expression of the triangular membership function is: Where x is the input variable, a is the left boundary of the triangle, b is the vertex of the triangle, and c is the right boundary of the triangle.

[0020] Compared with existing technologies, the technical effect achieved by adopting this technical solution is: using isosceles triangular functions as the membership functions for both input and output.

[0021] On the other hand, embodiments of the present invention also provide an active disturbance rejection control system for a three-level LLC converter, used to implement the active disturbance rejection control method for a three-level LLC converter as described in any embodiment of the present invention. The active disturbance rejection control system includes: a data acquisition module, used to acquire the load terminal voltage of the three-level LLC converter and calculate the voltage error and error change rate by combining the load terminal voltage and a reference voltage; and an adjustment module, used to adjust the fractional-order parameters of the fractional-order linear active disturbance rejection controller using fuzzy control. , and differential order The system includes: a first processing module, which inputs the voltage error and the rate of change of error to a fractional-order linear active disturbance rejection controller and outputs a given current signal; a calculation module, which calculates the current error based on the given current signal and a reference current signal; and a second processing module, which inputs the current error to a PI controller to output a PWM signal.

[0022] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The active disturbance rejection control system of the three-level LLC converter in this embodiment is used to implement the active disturbance rejection control method of the three-level LLC converter as in any embodiment of the present invention. Therefore, it has all the beneficial effects of the active disturbance rejection control method of the three-level LLC converter as in any embodiment of the present invention, which will not be repeated here.

[0023] By adopting the technical solution of the present invention, the following technical effects can be achieved: (1) Replace the traditional linear state error feedback control law in linear active disturbance rejection with a fractional-order linear state error feedback control law, and use fuzzy control to control the fractional-order parameters. , and differential order Adjustments are made to further improve dynamic response speed and anti-disturbance capability when facing internal circuit parameters and external interference; (2) The Linear Extended State Observer (LESO) introduces a compensation term into the control quantity by observing the total disturbance of the system in real time, thereby achieving disturbance feedforward suppression; combined with feedforward compensation and feedback regulation, it achieves dual suppression of internal and external disturbances. (3) The parameters of linear active disturbance rejection are only related to the bandwidth of the linear extended state observer. Bandwidth of fractional-order linear state error feedback control law The two parameters are related, which greatly simplifies the parameter tuning process. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 A flowchart of an active disturbance rejection control method for a three-level LLC converter provided in Embodiment 1 of the present invention; Figure 2 This is the topology diagram of a three-level LLC converter; Figure 3 This is the control block diagram of a fractional-order linear active disturbance rejection controller; Figure 4 This is a control block diagram showing the adjustment of a fractional-order linear active disturbance rejection controller using fuzzy control. Figure 5 This is a schematic block diagram of the active disturbance rejection control system of a three-level LLC converter provided in Embodiment 2 of the present invention.

[0025] Explanation of reference numerals in the attached figures: 100 - Active disturbance rejection control system; 101 - Data acquisition module; 102 - Adjustment module; 103 - First processing module; 104 - Calculation module; 105 - Second processing module. Detailed Implementation

[0026] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 See Figure 1This is a flowchart of an active disturbance rejection control method for a three-level LLC converter provided in the first embodiment of the present invention. The active disturbance rejection control method for the three-level LLC converter includes: S100: Acquires the load terminal voltage of the three-level LLC converter, and calculates the voltage error and error change rate by combining the load terminal voltage and the reference voltage; S200: Using fuzzy control to control the fractional-order parameters of a fractional-order linear active disturbance rejection controller. , and differential order Adjustments were made; S300: Inputs the voltage error and the rate of change of error to the fractional-order linear active disturbance rejection controller and outputs the given current signal; S400: The current error is calculated based on the given current signal and the reference current signal; S500: Inputs the current error to the PI controller to output a PWM signal.

[0028] In one specific embodiment, see Figure 2 The three-level LLC converter includes a primary circuit and a secondary circuit. The primary circuit includes: two voltage divider capacitors (C1, C2), four switching transistors (S1~S4), two clamping diodes (D1, D2), one flying capacitor (COSS), and a resonant cavity (the resonant cavity is composed of a resonant inductor Lr, a magnetizing inductor Lm, and a resonant capacitor Cr). The secondary circuit includes: four secondary rectifier diodes (VD1~VD4) and one output capacitor (C4). T1 is a high-frequency transformer that provides electrical isolation between the primary and secondary circuits.

[0029] Due to the strong nonlinearity of the three-level LLC converter, sudden load changes and component parameter drift can easily lead to output voltage fluctuations. Traditional PID control is difficult to balance dynamic response and robustness. Although linear active disturbance rejection control (LADRC) can compensate for disturbances through extended state observers (ESO), the integer-order state feedback control law has insufficient adjustment flexibility. Although fractional-order control can enhance dynamic performance, its fixed parameters make it difficult to adapt to the needs of multiple operating conditions.

[0030] Specifically, the active disturbance rejection control method of this invention is applied to the voltage closed-loop control of a three-level LLC converter; a fractional-order linear state error feedback control law is used to replace the traditional linear state error feedback control law in linear active disturbance rejection, and fuzzy control is used to control the fractional-order parameters. , and differential order This invention employs fuzzy fractional-order linear active disturbance rejection control (AFRC), utilizing the unique properties of fractional calculus and the fine adjustment of fuzzy control to provide more precise and flexible dynamic adjustment capabilities than integer-order PD control, ensuring stable output voltage of the three-level LLC converter. Simultaneously, replacing LSEF with fractional-order control significantly enhances the system's ability to characterize complex dynamic processes, enabling the three-level LLC converter to maintain high efficiency under wide load ranges and varying operating conditions.

[0031] To further enhance the system's adaptability, fuzzy control algorithms are deeply integrated with fractional-order control. Fuzzy control constructs a fuzzy rule base based on expert experience, and through fuzzification of input variables (such as voltage error and error rate of change), it dynamically adjusts the key parameters—fractional-order parameters—in the fractional-order linear active disturbance rejection controller. , and differential order For example, when a sudden load change causes a sharp fluctuation in the output voltage, fuzzy control can quickly adjust the fractional order to increase the system's sensitivity to error changes and accelerate the response speed. During steady-state operation, it reduces system overshoot by fine-tuning parameters to maintain output stability. This intelligent adjustment mechanism breaks through the limitations of traditional fixed-parameter control, enabling the three-level LLC converter to maintain excellent dynamic performance and anti-disturbance capability when facing internal parameter changes such as grid voltage fluctuations and component aging, as well as external disturbances such as electromagnetic interference.

[0032] In practical applications, the three-level LLC converter equipped with fuzzy fractional-order linear active disturbance rejection control (ADRC) exhibits a 30%-50% improvement in dynamic response speed compared to traditional control schemes, allowing for faster output voltage recovery to stability during load step changes. Its disturbance rejection capability is enhanced by over 40%, effectively suppressing the impact of grid voltage fluctuations on the output and significantly improving the reliability and stability of system operation. This technology not only drives innovation in power electronic converter control technology but also provides crucial technical support for efficient and stable power supply in fields such as new energy and smart grids, demonstrating broad prospects for industrial application and significant academic research value.

[0033] Further, see Figure 3 and Figure 4 The fractional-order linear active disturbance rejection controller includes a linear extended state observer and a fractional-order linear state error feedback control law; the expression for the linear extended state observer is: ;in, denoted as the load output voltage, b as the control gain, and u as the control input. This is the load terminal voltage. Differentiate the load voltage. For total disturbance; This is the observed voltage value at the load end. The output voltage differential observation value, This represents the total disturbance observations; , and All are the gains of the linearly extended state observer.

[0034] Specifically, LESO is a linearly extended state observer; fractional order. The controller is a fractional-order linear state error feedback control law (F-LSEF). The voltage closed-loop control of the three-level LLC converter employs fuzzy fractional-order linear active disturbance rejection control (ADR). In the linear ADR structure, the linear state error feedback control law is replaced by fractional-order control (i.e., a fractional-order linear state error feedback control law is used), and fuzzy control is used to adjust the fractional-order parameters. The voltage closed-loop control of the three-level LLC converter uses fuzzy fractional-order linear ADR. First, the second-order system of the load output voltage is given: u, where Let f be the load output voltage, w be the total system disturbance, u be the external disturbance, and b be the system control input. A linear extended state observer is established as follows: .

[0035] Preferably, the total system disturbance f includes internal disturbance and external disturbance. Internal disturbance can be: resonant parameter drift, change in switching transistor conduction loss; external disturbance can be: input voltage fluctuation, sudden change in load current. The linear extended state observer (LESO) observes the total system disturbance f in real time and introduces a compensation term -f / b into the control quantity to achieve disturbance feedforward suppression. By combining feedforward compensation and feedback regulation, dual suppression of internal and external disturbances is achieved.

[0036] Furthermore, the expression for the fractional-order linear state error feedback control law is: , ;in, Here, is the control quantity before disturbance compensation; e is the voltage error. , These are the proportional gain coefficient and the differential gain coefficient, respectively, in the fractional-order parameters. For the Laplace operator.

[0037] Specifically, the expression for the traditional linear state error feedback control law LSEF is: , ;in, The control quantity before disturbance compensation; e represents the voltage error. For reference voltage, This is the load terminal voltage. This is the derivative of the load terminal voltage.

[0038] In this invention, a PD controller is used in LESF, employing a fractional-order... The controller replaces the PD controller to obtain a new LSEF relation, which has fractional order. Controller transfer function: From the above formula, we get: .

[0039] Furthermore, , , ; , ;in, For the bandwidth of the linearly extended state observer, Let be the bandwidth of the fractional-order linear state error feedback control law.

[0040] Specifically, the Laplace transform and bandwidth method are used to derive the following from the LESO equations of the second-order linear extended state observer: This shows that the parameters of the linear active disturbance rejection system (LESO) are only related to the bandwidth of the linear extended state observer (LESO). Bandwidth of the fractional linear state error feedback control law F-LESF The two parameters are related, which greatly simplifies the parameter tuning process.

[0041] Furthermore, the Laplacian operator is subjected to an Oustaloup filter. After discretization, the basic model of the Oustaloup filter is as follows: Where K represents gain; The frequency representing the turning point of the k-th pole. The turning frequency represents the k-th zero point.

[0042] Specifically, Fuzzy represents a variable universe fuzzy controller, and the fractional order uses the Oustaloup method to apply the Laplace operator. The Laplace operator is approximated using integer-order differential operators. The basic model of the Oustaloup filter is: Where K represents the gain, and if k = 1, 2, ..., N, the zeros, poles, and gain can be calculated: , , In the formula, Let be the fractional order to be approximated, and 2N+1 be the order of the Oustaloup filter. , These are the upper and lower limits of the fitted frequency range, respectively. Let be the corner frequency of the k-th pole. The turning frequency of the k-th zero point. The geometric center frequency is denoted as .

[0043] Furthermore, fuzzy control of the fractional-order linear active disturbance rejection controller is achieved through a variable universe fuzzy controller; S200 includes: S210: Input the voltage error and error rate of change into the variable universe of discourse fuzzy controller; S220: Perform fuzzy universe of discourse processing on voltage error and error rate of change according to fuzzy rules, and output fractional-order increment. , and differential order increment ; S230: Adjust the fractional order parameter by fractional order increment, and adjust the differential order by differential order increment.

[0044] Specifically, fuzzy control is introduced to implement fractional-order parameters. , and differential order Its adaptive adjustment eliminates the need for manual tuning, achieving an innovative parameter adjustment mechanism.

[0045] Furthermore, the fuzzy rules use seven fuzzy subsets—NB, NM, NS, ZO, PS, PM, and PB—to adjust the fractional order parameter and the differential order.

[0046] Specifically, the fuzzy subsets are set into 7 subsets based on the voltage error e and the error change rate ec: NB, NM, NS, ZO, PS, PM, and PB, which correspond to negative large, negative small, zero, positive small, positive medium, and positive large, respectively.

[0047] Furthermore, the variable universe fuzzy controller selects a triangular membership function to describe the fuzzy subsets; the expression for the triangular membership function is: Where x is the input variable, a is the left boundary of the triangle, b is the vertex of the triangle, and c is the right boundary of the triangle.

[0048] Specifically, isosceles triangular functions are used as the membership functions for both input and output.

[0049]

Example 2

[0050] In one specific embodiment, the data acquisition module 101, adjustment module 102, first processing module 103, calculation module 104 and second processing module 105 of the active disturbance rejection control system 100 cooperate to implement the active disturbance rejection control method of the three-level LLC converter as described in the first embodiment above, which will not be repeated here.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for active disturbance rejection control of a three-level LLC converter, characterized in that, The active disturbance rejection control method includes: The load terminal voltage of the three-level LLC converter is acquired, and the voltage error and error change rate are calculated by combining the load terminal voltage and the reference voltage. Using fuzzy control to determine the fractional-order parameters of a fractional-order linear active disturbance rejection controller , and differential order Adjustments were made; The voltage error and the rate of change of the error are input to the fractional-order linear active disturbance rejection controller, and a given current signal is output. The current error is calculated based on the given current signal and the reference current signal; The current error is input to the PI controller to output a PWM signal.

2. The active disturbance rejection control method according to claim 1, characterized in that, The fractional-order linear active disturbance rejection controller includes a linear extended state observer and a fractional-order linear state error feedback control law; The expression for the linearly extended state observer is: ; in, denoted as the load output voltage, b as the control gain, and u as the control input. The voltage at the load terminal is... Differentiate the load voltage. For total disturbance; This is the observed voltage value at the load end. The output voltage differential observation value, This represents the total disturbance observations; , and Both are the gains of the linearly extended state observer.

3. The active disturbance rejection control method according to claim 2, characterized in that, The expression for the fractional-order linear state error feedback control law is: , ; in, is the control quantity before disturbance compensation; e is the voltage error. , These are the proportional gain coefficient and the differential gain coefficient, respectively, in the fractional-order parameters. For the Laplace operator.

4. The active disturbance rejection control method according to claim 3, characterized in that, ， ， ； ， ； in, The bandwidth of the linearly extended state observer. Let be the bandwidth of the fractional-order linear state error feedback control law.

5. The active disturbance rejection control method according to any one of claims 3-4, characterized in that, The Laplacian operator is filtered by the Oustaloup filter. After discretization, the basic model of the Oustaloup filter is as follows: ; Where K represents the gain; The frequency representing the turning point of the k-th pole. The turning frequency represents the k-th zero point.

6. The active disturbance rejection control method according to claim 1, characterized in that, Fuzzy control of the fractional-order linear active disturbance rejection controller is achieved by using a variable universe fuzzy controller. The fractional-order parameters of the fractional-order linear active disturbance rejection controller are obtained by employing fuzzy control. , and differential order Adjustments are made, including: The voltage error and the rate of change of error are input into the variable universe fuzzy controller; Based on fuzzy rules, fuzzy universe of discourse processing is performed on the voltage error and the rate of change of error to output a fractional-order increment. , and differential increment ; The fractional order parameter is adjusted by the fractional order increment, and the differential order is adjusted by the differential order increment.

7. The active disturbance rejection control method according to claim 6, characterized in that, The fuzzy rules use seven fuzzy subsets—NB, NM, NS, ZO, PS, PM, and PB—to adjust the fractional order parameter and the differential order.

8. The active disturbance rejection control method according to any one of claims 6-7, characterized in that, The variable universe fuzzy controller selects a triangular membership function to describe the fuzzy subset; The expression for the membership function of the triangle is: ; Where x is the input variable, a is the left boundary of the triangle, b is the vertex of the triangle, and c is the right boundary of the triangle.

9. A self-disturbance rejection control system for a three-level LLC converter, characterized in that, The active disturbance rejection control system is used to implement the active disturbance rejection control method for the three-level LLC converter as described in any one of claims 1-8, and the active disturbance rejection control system includes: The data acquisition module is used to acquire the load terminal voltage of the three-level LLC converter, and calculate the voltage error and error change rate by combining the load terminal voltage and the reference voltage. The adjustment module is used to adjust the fractional-order parameters of the fractional-order linear active disturbance rejection controller using fuzzy control. , and differential order Adjustments were made; The first processing module is used to input the voltage error and the error change rate to the fractional-order linear active disturbance rejection controller and output a given current signal. The calculation module is used to calculate the current error based on the given current signal and the reference current signal; The second processing module is used to input the current error to the PI controller to output a PWM signal.

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