Constant value steady-state error convergence control method and device for direct-current buck converter

Abstract

The invention provides a direct current buck converter constant value steady-state error convergence control method and device. The method comprises the following steps: acquiring the input voltage, the output voltage and the inductive current of each stage of direct current buck converter; setting a corresponding output voltage target value, an error coefficient and a convergence factor; calculating an error function of each stage according to a difference value between an output voltage target value and an actual output voltage in combination with an error coefficient; carrying out convergence operation on the error function to enable the error function to converge in finite time; calculating an actual voltage gain according to the result of the convergence operation in combination with the dynamic change of the input voltage and the inductive current; and comparing the actual voltage gain serving as a modulation signal with a carrier wave to generate a pulse width modulation signal, and driving a power switch tube of the direct-current buck converter with the corresponding series. Based on the method, the invention further provides a control device. According to the invention, the change of the output voltage of the DC buck converter in the error convergence approximation process can be dynamically compensated, and a good control effect is realized.

Description

Technical Field

[0001] This invention belongs to the field of DC-DC converter technology, and specifically relates to a method and device for controlling the setpoint steady-state error convergence of a DC-DC buck converter. Background Technology

[0002] Distributed generation systems, built and developed based on renewable energy, have expanded into modern power grids with high penetration rates, delivering high-quality, clean, and efficient power resources to users. Compared with other new energy generation methods, photovoltaic (PV) power generation can directly convert photovoltaic energy into electricity through solar photovoltaic panels in an extremely simple form, without any intermediate links or mechanical movement during the conversion process. Furthermore, modular PV power generation devices can be flexibly assembled and disassembled, making it easier to change the generation capacity as needed. Therefore, PV power generation has a broader application prospect and consumer market. Based on distributed PV power generation, by organically integrating battery banks, PV inverters, local loads, and other devices, a distributed PV DC microgrid system can be formed that can operate both grid-connected and islanded. With the connection of various DC loads, the distributed PV DC microgrid system will contain DC power at different voltage levels. How to efficiently and quickly achieve DC power voltage conversion undoubtedly places new and higher demands on the topology and control strategies of DC converters.

[0003] The voltage gain range of traditional DC-DC converters can be arbitrarily adjusted by the duty cycle. However, in practice, the voltage gain of the converter is often limited by the parasitic parameters in the switching devices and magnetic components. In high-gain applications, if the duty cycle is increased (i.e., the extreme duty cycle) to achieve high-gain output, the current ripple, current stress on the switching devices, and conduction losses in the circuit will continuously increase with the increase of the duty cycle. The reverse recovery problem of the output diode will also become more prominent, and the conversion efficiency of the converter will decrease accordingly. Isolated DC-DC converters can meet the requirements of large-ratio step-up and step-down by properly designing the transformer turns ratio. However, the switching voltage overshoot and electromagnetic interference caused by the leakage inductance of the transformer cannot be ignored. Moreover, the transformer losses, size, and cost also need to be comprehensively considered. Introducing a coupling inductor can improve the voltage gain of the DC-DC converter, but the presence of leakage inductance will generate voltage spikes, resulting in increased voltage stress, reduced efficiency, and severe electromagnetic interference. Using active clamping or passive methods can weaken voltage spikes, but it increases the complexity of the topology.

[0004] Therefore, existing DC-DC converters, especially in cascaded applications requiring high gain and multiple voltage outputs, mostly focus on increasing voltage gain by introducing complex topologies such as transformers and coupled inductors. However, this brings problems such as leakage inductance, voltage spikes, electromagnetic interference, and increased size and cost. At the same time, research on their control strategies is relatively weak, failing to effectively solve the dynamic coupling and independent control problems of each stage of the converter in the cascaded system. This results in slow dynamic response, poor steady-state accuracy, and a lack of modular control schemes. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method and apparatus for setpoint steady-state error convergence control of a DC-DC buck converter. This method can dynamically compensate for changes in the output voltage of the DC-DC buck converter during the error convergence approximation process, achieving excellent control performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for convergent control of steady-state error of a DC-DC buck converter includes the following steps: Obtain the input voltage, inductor current, and output voltage of each stage of the DC-DC buck converter; set the corresponding target value for the output voltage, error coefficient, and convergence factor for each stage of the DC-DC buck converter; Based on the difference between the target output voltage and the actual output voltage, and in conjunction with the error coefficient, the error function for each stage is calculated; the error function is then subjected to a convergence operation based on the convergence factor, so that the error function converges to zero within a finite time. Based on the results of the convergence calculation, and combined with the dynamic changes of the input voltage and inductor current, the actual voltage gain of each stage of the DC-DC buck converter is calculated. The actual voltage gain is used as a modulation signal, compared with the carrier wave to generate a pulse width modulation signal, which is used to drive the power switching transistors of the corresponding stage of the DC-DC buck converter.

[0007] Furthermore, the process of calculating the error function is as follows: Establish the dynamic equations for each stage of the DC-DC buck converter, specifically: ; in, Indicates the first The input voltage of the DC-DC buck converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; The number of stages in a DC-DC buck converter; Based on the aforementioned dynamic equations, the first... The error function of the step-down DC-DC converter is: ; in, Indicates the first Error function of a step-down DC-DC converter; For the first The target output voltage value of the DC-DC buck converter; This represents the error coefficient.

[0008] Furthermore, the convergence operation process is as follows: ; in, Representing the error function Regarding time The derivative; Indicates the first The convergence factor of a step-down DC-DC converter.

[0009] Furthermore, the calculation process for the actual voltage gain simultaneously considers the input voltage, target output voltage, state error, and dynamic changes in inductor current of the converter stage, specifically: ; in, Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Error coefficient of a step-down DC-DC converter; Indicates the first The target output voltage value of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The input voltage of the DC-DC buck converter.

[0010] Furthermore, the process of using the actual voltage gain as a modulation signal, comparing it with the carrier wave to generate a pulse width modulation signal, and using this signal to drive the power switching transistors of the corresponding stage of the DC-DC buck converter includes: The calculated first Actual voltage gain of the DC-DC buck converter As a modulating wave; The modulated wave It is simultaneously input to the comparator with a preset carrier signal for real-time comparison; When the modulated wave When the instantaneous value of the signal is greater than the instantaneous value of the carrier signal, the comparator outputs a high level; otherwise, it outputs a low level, thereby generating a pulse width modulation signal. The pulse width modulation signal is amplified by the driving circuit and then applied to the first... The power switching transistors of the DC-DC buck converter The control terminal is used to control its on and off states.

[0011] The present invention also proposes a controller for implementing the control method, comprising: The signal acquisition module is used to acquire the input voltage, inductor current, and output voltage of the DC-DC buck converter; The storage module is used to store the preset output voltage target value, error coefficient, and convergence approximation factor; The computation and processing module is used to perform error function calculation, convergence calculation, and voltage gain calculation. The pulse width modulation signal generation module is used to generate control signals to drive the power switching transistors based on the calculated voltage gain.

[0012] This invention also proposes a setpoint steady-state error convergence control device for a DC-DC buck converter, comprising: A multi-stage DC-DC buck converter connected end-to-end; and the input terminal of the first-stage DC-DC buck converter is connected to a DC power supply. The number of controllers is equal to the number of DC-DC buck converters, and each controller independently controls each stage of the DC-DC buck converter.

[0013] Furthermore, the DC-DC buck converter is a Buck converter.

[0014] Furthermore, the Buck buck converter includes a power switch, a diode, a filter inductor, and a filter capacitor; The input terminal of the power switch is connected to the positive input terminal of the converter stage. The output terminal of the power switch is connected to the cathode of the diode and one end of the filter inductor. The anode of the diode is connected to the common ground. The other end of the filter inductor serves as the positive output terminal of the converter stage. The filter capacitor is connected between the positive output terminal and the common ground.

[0015] Furthermore, the device is suitable for distributed photovoltaic DC microgrids, used to supply power to DC loads of different voltage levels.

[0016] The effects described in the invention are merely those of the embodiments, and not all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects: This invention proposes a method and apparatus for convergence control of the setpoint steady-state error of a DC-DC buck converter. The method includes the following steps: acquiring the input voltage, inductor current, and output voltage of each stage of the DC-DC buck converter; setting a corresponding target output voltage value, error coefficient, and convergence factor for each stage of the DC-DC buck converter; calculating the error function of each stage based on the difference between the target output voltage value and the actual output voltage, combined with the error coefficient; performing a convergence operation on the error function based on the convergence factor, so that the error function converges to zero within a finite time; calculating the actual voltage gain of each stage of the DC-DC buck converter based on the result of the convergence operation, combined with the dynamic changes of the input voltage and inductor current; using the actual voltage gain as a modulation signal, comparing it with a carrier wave to generate a pulse width modulation signal, which is used to drive the power switches of the corresponding stage of the DC-DC buck converter. Based on this method for convergence control of the setpoint steady-state error of a DC-DC buck converter, an apparatus for convergence control of the setpoint steady-state error of a DC-DC buck converter is also proposed. This invention is applicable to multi-stage DC-DC buck converter topologies, taking into account the input voltage, target output voltage, state error, and inductor current of the DC-DC buck converter in each stage. Therefore, it can dynamically compensate for the changes in output voltage during the error convergence process of the DC-DC buck converter, achieving good control performance.

[0017] This invention avoids the control output of the DC converter under extreme duty cycle conditions. The multi-stage DC buck converter effectively increases the DC voltage buck output range by setting its own output voltage target value. By setting the output voltage target value, the converter can ensure a wide gain voltage output. Attached Figure Description

[0018] Figure 1 This is the approximation curve path of the DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of the present invention; Figure 2 This is a flowchart of a DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of the present invention; Figure 3 The topology of the two-stage cascaded DC-DC buck converter used in the control method proposed in Embodiment 1 of this invention; Figure 4 The controller for the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 5 The controller for the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 6This is a block diagram illustrating the control method for the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention. Figure 7 This is a block diagram illustrating the control method for the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention. Figure 8 The output voltage waveform of the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 9 The output voltage waveform of the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 10 The ripple of the output voltage after the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention has stabilized; Figure 11 The ripple of the output voltage after the second-stage DC-DC buck converter proposed in Embodiment 1 of this invention has stabilized; Figure 12 This is a schematic diagram of the connection of a DC-DC buck converter setpoint steady-state error convergence control device proposed in Embodiment 2 of the present invention; Figure 13 This is a schematic diagram of the connection of the controller proposed in Embodiment 2 of the present invention. Detailed Implementation

[0019] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure of the invention, components and arrangements of specific examples are described below. Furthermore, reference numerals and / or letters may be repeated in different examples. This repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components, processing techniques, and processes are omitted in this invention to avoid unnecessarily limiting the invention.

[0020] Example 1 Embodiment 1 of this invention proposes a method for convergence control of the setpoint steady-state error of a DC-DC buck converter, which is used to solve the technical problems existing in the convergence control of the setpoint steady-state error of DC-DC converters in the prior art.

[0021] The core idea of ​​the fixed-value steady-state error convergence control algorithm of this invention lies in performing fixed-value steady-state control on the output voltage of each stage of the DC-DC buck converter. Specifically, within a finite time range, the steady-state error is dynamically adjusted to ensure that the steady-state error of the DC-DC buck converter output voltage eventually tends to 0. In terms of implementation, the steady-state error of the output voltage of each stage of the DC-DC buck converter is controlled according to... Figure 1 The trajectory shown converges to 0 within a finite time range. Figure 1 middle, The path analysis expression for approximating the curve; To approximate the amplitude of the curve; It is an exponential constant; The convergence approximation factor; For time.

[0022] Figure 2 This is a flowchart of a DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of the present invention; In step S210, the input voltage, inductor current, and output voltage of each stage of the DC-DC buck converter are obtained; and the corresponding target value of output voltage, error coefficient, and convergence factor are set for each stage of the DC-DC buck converter. In step S220, based on the difference between the target output voltage and the actual output voltage, and in conjunction with the error coefficient, the error function of each stage is calculated; the error function is then subjected to a convergence operation based on the convergence factor so that the error function converges to zero within a finite time. The process of calculating the error function is as follows: Establish the dynamic equations for each stage of the DC-DC buck converter, specifically: ; in, Indicates the first The input voltage of the DC-DC buck converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; The number of stages in a DC-DC buck converter; Based on the aforementioned dynamic equations, the first... The error function of the step-down DC-DC converter is: ; in, Indicates the first Error function of a step-down DC-DC converter; For the first The target output voltage value of the DC-DC buck converter; This represents the error coefficient.

[0023] The convergence operation process is as follows: ; in, Representing the error function Regarding time The derivative; Indicates the first The convergence factor of a step-down DC-DC converter.

[0024] In step S230, based on the results of the convergence calculation and combined with the dynamic changes of the input voltage and inductor current, the actual voltage gain of each stage of the DC-DC buck converter is calculated. The calculation process for the actual voltage gain simultaneously considers the input voltage, target output voltage, state error, and dynamic changes in inductor current of the converter stage. Specifically: ; in, Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Error coefficient of a step-down DC-DC converter; Indicates the first The target output voltage value of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The input voltage of the DC-DC buck converter.

[0025] In step S240, the actual voltage gain is used as the modulation signal, compared with the carrier wave to generate a pulse width modulation signal, which is used to drive the power switching transistors of the corresponding stage of the DC-DC buck converter.

[0026] The calculated first Actual voltage gain of the DC-DC buck converter As a modulating wave; The modulated wave It is simultaneously input to the comparator with a preset carrier signal for real-time comparison; When the modulated wave When the instantaneous value of the signal is greater than the instantaneous value of the carrier signal, the comparator outputs a high level; otherwise, it outputs a low level, thereby generating a pulse width modulation signal. The pulse width modulation signal is amplified by the driving circuit and then applied to the first... The power switching transistors of the DC-DC buck converter The control terminal is used to control its on and off states.

[0027] Figure 3 This is a two-stage cascaded DC-DC buck converter topology used in the control method proposed in Embodiment 1 of the present invention. Structurally, it consists of a first-stage DC-DC buck converter and a second-stage DC-DC buck converter; in Figure 3 middle, This is the input voltage for a two-stage cascaded DC-DC buck converter; This is the power switching transistor for the first-stage DC-DC buck converter; The diode is used in the first-stage DC-DC buck converter. This is the filter inductor for the first-stage DC-DC buck converter; This is the filter capacitor for the first-stage DC-DC buck converter; This is the output voltage of the first-stage DC-DC buck converter, and also the input voltage of the second-stage DC-DC buck converter; It serves as the power switch for the second-stage DC-DC buck converter; The diode is used in the second-stage DC-DC buck converter. This is the filter inductor for the second-stage DC-DC buck converter; This is the filter capacitor for the second-stage DC-DC buck converter; The output resistor of a two-stage cascaded DC-DC buck converter; Output voltage of a two-stage cascaded DC-DC buck converter; For the filter inductor of the first-stage DC-DC buck converter The inductor current; : The current flows through the filter inductor of the second-stage DC-DC buck converter The inductor current.

[0028] In this application, a controller is set for each stage of the DC-DC buck converter to achieve separate control of each stage of the DC-DC buck converter. Figure 4 The controller for the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 5 This is the controller for the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention.

[0029] To fully explain Figure 4 The working process of the controller of the first-stage DC-DC buck converter. Figure 6 This is a block diagram illustrating the control method for the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 6 In this context, CN11 is the first set constant in the control algorithm of the first-stage DC-DC buck converter, and its value is the error coefficient. CN12 is the second set constant in the control algorithm of the first-stage DC-DC buck converter, and its value is the target value of the converter's output voltage (which is a fixed value). CN13 is the third set constant in the control algorithm of the first-stage DC-DC buck converter, and its value is the convergence approximation factor. CN14 is the fourth set constant in the control algorithm of the first-stage DC-DC buck converter, and its value is a constant of 1; CN15 is the fifth set constant in the control algorithm of the first-stage DC-DC buck converter, and its value is the inductance of the filter inductor in the converter. CL11 is the input voltage acquired in the control algorithm of the first-stage DC-DC buck converter. CL12 is the filter inductor current collected in the control algorithm of the first-stage DC-DC buck converter. SU11 is the first subtractor in the control algorithm of the first-stage DC-DC buck converter; SU12 is the second subtractor in the control algorithm of the first-stage DC-DC buck converter; SU13 is the third subtractor in the control algorithm of the first-stage DC-DC buck converter; DV11 is the first divider in the control algorithm of the first-stage DC-DC buck converter; DV12 is the second divider in the control algorithm of the first-stage DC-DC buck converter; DV13 is the third divider in the control algorithm of the first-stage DC-DC buck converter; DV14 is the fourth divider in the control algorithm of the first-stage DC-DC buck converter; DR11 is the first differentiator in the control algorithm of the first-stage DC-DC buck converter; DR12 is the first differentiator in the control algorithm of the first-stage DC-DC buck converter. The control algorithm for the first-stage DC-DC buck converter includes the second differentiator; MU11 is the first multiplier; MU12 is the second multiplier; MU13 is the third multiplier; MU14 is the fourth multiplier; MU15 is the fifth multiplier; AD11 is the first adder; CTD1 is the reciprocal; and P1 is the PWM generator. The power switching transistor in the first-stage DC-DC buck converter, i.e. Figure 2 In .

[0030] To fully explain Figure 5 The working process of the controller of the first-stage DC-DC buck converter. Figure 7 This is a block diagram illustrating the control method for the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; CN21 is the first set constant in the control algorithm of the second-stage DC-DC buck converter, and its value is the error coefficient. CN22 is the second set constant in the control algorithm of the second-stage DC-DC buck converter, and its value is the target value of the converter's output voltage (which is a fixed value). CN23 is the third set constant in the control algorithm of the second-stage DC-DC buck converter, and its value is the convergence approximation factor. CN24 is the fourth set constant in the control algorithm of the second-stage DC-DC buck converter, and its value is a constant of 1; CN25 is the fifth set constant in the control algorithm of the second-stage DC-DC buck converter, and its value is the inductance of the filter inductor in the converter. CL21 is the input voltage acquired in the control algorithm of the second-stage DC-DC buck converter, and its value is the output voltage of the first-stage DC-DC buck converter. CL22 is the filter inductor current collected in the control algorithm of the second-stage DC-DC buck converter. SU21 is the first subtractor in the control algorithm of the second-stage DC-DC buck converter; SU22 is the second subtractor in the control algorithm of the second-stage DC-DC buck converter; SU23 is the third subtractor in the control algorithm of the second-stage DC-DC buck converter; DV21 is the first divider in the control algorithm of the second-stage DC-DC buck converter; DV22 is the second divider in the control algorithm of the second-stage DC-DC buck converter; DV23 is the third divider in the control algorithm of the second-stage DC-DC buck converter; DV24 is the fourth divider in the control algorithm of the second-stage DC-DC buck converter; DR21 is the first differentiator in the control algorithm of the second-stage DC-DC buck converter; DR22 is the second-stage DC-DC buck converter... The second differentiator in the control algorithm of the converter; MU21 is the first multiplier in the control algorithm of the second-stage DC-DC buck converter; MU22 is the second multiplier in the control algorithm of the second-stage DC-DC buck converter; MU23 is the third multiplier in the control algorithm of the second-stage DC-DC buck converter; MU24 is the fourth multiplier in the control algorithm of the second-stage DC-DC buck converter; MU25 is the fifth multiplier in the control algorithm of the second-stage DC-DC buck converter; AD21 is the first adder in the control algorithm of the second-stage DC-DC buck converter; CTD2 is the reciprocal in the control algorithm of the second-stage DC-DC buck converter; P2 is the PWM generator in the control algorithm of the second-stage DC-DC buck converter. For the power switching transistors in the second-stage DC-DC buck converter, i.e. Figure 2 In .

[0031] To fully illustrate the implementation process of the DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of the present invention, the present invention uses a two-stage cascaded DC-DC buck converter topology to illustrate the implementation process of the method.

[0032] Establish the dynamic equations for the first-stage DC-DC buck converter and the second-stage DC-DC buck converter respectively: (1) (2) in, This represents the actual voltage gain of the first-stage DC-DC buck converter; This represents the actual voltage gain of the second-stage DC-DC buck converter.

[0033] Simplifying equations (1) and (2), we can obtain the formulas for the output voltage of the first-stage DC-DC buck converter and the output voltage of the second-stage DC-DC buck converter, respectively: (3) (4) Introduce error functions for formulas (3) and (4): (5) in, Indicates the first Error function of a step-down DC-DC converter; For the first The target output voltage value of the DC-DC buck converter; Indicates the error coefficient; For the number of stages in a DC-DC buck converter, =1,2.

[0034] For formula (5) The result is obtained by performing calculations according to formula (6): (6) in, Indicates the first The convergence factor of a step-down DC-DC converter.

[0035] Substituting equation (5) into equation (6), we get: (7) Transforming equation (7), we get: (8) when Substituting equation (3) into equation (8), we get: (9) Simplifying equation (9), we get: (10) Equation (10) is used as the modulation wave for driving the power switch S1 and compared with the carrier wave in the PWM generator: when the modulation wave > the carrier wave, the output of the PWM generator is 1; when the modulation wave < the carrier wave, the output of the PWM generator is 0.

[0036] Similarly, when Substituting equation (4) into equation (8), we get: (11) Simplifying equation (11), we get: (12) Equation (12) is used as the modulation wave for driving the power switch S2 and compared with the carrier wave in the PWM generator: when the modulation wave > the carrier wave, the output of the PWM generator is 1; when the modulation wave < the carrier wave, the output of the PWM generator is 0.

[0037] From the entire derivation process of the voltage gain calculation formula, the voltage gain obtained from equations (10) and (12) is sufficient to ensure that the error functions E1 and E2 of the output voltage of the first-stage and second-stage DC-DC buck converters both meet the requirements of equation (6). Therefore, the error function of the output voltage... and All can be in accordance with Figure 1 The operating trajectory described in the figure ensures that the error of the output voltage of the first and second stage DC buck converters eventually converges to 0 within a finite time range.

[0038] The implementation of this method requires no linearization and no simplification of the system model. Equations (10) and (12) both show that in the process of designing the voltage gain, the control method simultaneously considers the input voltage, output voltage target value, state error, and inductor current of each stage of the DC-DC buck converter, and can dynamically compensate for the change in output voltage of the DC-DC buck converter during the error convergence approximation process.

[0039] To verify the feasibility and effectiveness of the setpoint steady-state error convergence control method for a DC-DC buck converter proposed in Embodiment 1 of this invention, necessary experimental verifications were conducted on the control method in a simulation environment. The relevant parameter settings are as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] and Both are 4.5mH, filter capacitors and The voltage is 4.7μF, and the output resistance R is 10Ω; the convergence factor of the first-stage DC-DC buck converter is... Convergence factor of the second-stage DC-DC buck converter Both are 0.02, with an error coefficient. and All are 0.01. The converter input voltage is 100V, the reference output voltage of the first-stage DC-DC buck converter is 50V, and the reference output voltage of the second-stage DC-DC buck converter is 25V. Figure 8 The output voltage waveform of the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention; Figure 9The output voltage waveform of the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention is shown.

[0040] Filter inductor and The setting of 4.5mH is mainly based on the requirement of current ripple, which controls the inductor current ripple within an acceptable range.

[0041] Filter capacitor and The value is set to 4.7μF mainly based on the requirement of output voltage ripple, which is used to generate a smooth output voltage waveform in the simulation, but not so large as to slow down the dynamic response of the system, so as to clearly demonstrate the speed of the present invention in the dynamic adjustment process.

[0042] Setting the load resistance R to 10Ω effectively demonstrates the performance of the control method under typical load conditions.

[0043] Convergence factor of the first-stage DC-DC buck converter Convergence factor of the second-stage DC-DC buck converter All values ​​are set to 0.02. The convergence factor directly determines the convergence speed of the error function. Setting it to 0.02 means that the error will decay at a relatively gentle exponential rate. This reflects the adjustability of the method, and choosing such a moderate value helps to clearly observe the convergence process in the simulation, avoiding the inability to display dynamic details due to excessively fast convergence, or the impact on the results due to excessively slow convergence.

[0044] Error coefficient and The error coefficient is set to 0.01. Its function is to unify the dimensions of the voltage error or scale its magnitude so that it matches the numerical values ​​of other terms in the method (such as the differential term of inductor current). Setting it to 0.01 can prevent the voltage error term from taking an absolute dominant position in the calculation and ensure that the voltage error and current change rate of the method can work together to achieve stable and smooth control.

[0045] The reference value for the output voltage of the first-stage DC-DC buck converter is set to 50V, and the reference value for the output voltage of the second-stage DC-DC buck converter is set to 25V. This is used to verify the effectiveness of the present invention in wide-range buck and cascaded operation scenarios, and to avoid any stage operating at the extreme duty cycle. This proves the beneficial effect of the present invention in avoiding the extreme duty cycle by setting target values ​​and achieving wide-gain output.

[0046] from Figure 8 and Figure 9As can be seen above, both the first and second stage DC-DC buck converters can achieve rapid convergence of the output voltage to the target value of each stage after a short-time dynamic adjustment control of 8ms, accurately realizing the buck conversion process. During the dynamic adjustment control process, the output voltage waveforms of the first and second stage DC-DC buck converters show no oscillation, maintaining good dynamic response performance.

[0047] Figure 10 The ripple of the output voltage after the first-stage DC-DC buck converter proposed in Embodiment 1 of the present invention has stabilized; Figure 11 This describes the output voltage ripple of the second-stage DC-DC buck converter proposed in Embodiment 1 of the present invention after achieving stable output. Regarding steady-state output, Figure 10 It can be seen that the output voltage range of the first-stage DC-DC buck converter is 47~53V, and the voltage ripple is stably controlled within 3V. Figure 11 It can be seen that due to the influence of the first and second stage filters, the output voltage range of the second stage DC buck converter is 24.8~25.2V, and the voltage ripple is stably controlled within 0.2V, both maintaining good steady-state response performance.

[0048] The steady-state error convergence control method for DC-DC buck converter proposed in Embodiment 1 of this invention is applicable to multi-stage DC-DC buck converter topologies. It takes into account the input voltage, target output voltage, state error, and inductor current of the DC-DC buck converter in each stage. Therefore, it can dynamically compensate for the change in output voltage of the DC-DC buck converter during the error convergence approximation process, and achieve good control effect.

[0049] The DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of this invention avoids the control output of the DC-DC converter under extreme duty cycle conditions. The multi-stage DC-DC buck converter effectively increases the DC voltage buck output range by setting its own output voltage target value. By setting the output voltage target value, the wide gain voltage output of the converter can be guaranteed.

[0050] Example 2 Based on the DC-DC buck converter setpoint steady-state error convergence control method proposed in Embodiment 1 of the present invention, Embodiment 2 of the present invention also proposes a DC-DC buck converter setpoint steady-state error convergence control device, which includes a multi-stage DC-DC buck converter connected end to end; and the input terminal of the first-stage DC-DC buck converter is connected to a DC power supply. The number of controllers is equal to the number of DC-DC buck converters, and each controller independently controls each stage of the DC-DC buck converter.

[0051] Figure 12This is a schematic diagram of the connection of a DC-DC buck converter setpoint steady-state error convergence control device proposed in Embodiment 2 of the present invention; the DC-DC buck converter is a Buck converter, which includes a power switch, a diode, a filter inductor, and a filter capacitor; The input terminal of the power switch is connected to the positive input terminal of the converter stage. The output terminal of the power switch is connected to the cathode of the diode and one end of the filter inductor. The anode of the diode is connected to the common ground. The other end of the filter inductor serves as the positive output terminal of the converter stage. The filter capacitor is connected between the positive output terminal and the common ground.

[0052] The DC-DC buck converter setpoint steady-state error convergence control device proposed in Embodiment 2 of the present invention is suitable for distributed photovoltaic DC microgrids and is used to supply power to DC loads of different voltage levels.

[0053] Figure 13 This is a connection diagram of the controller proposed in Embodiment 2 of the present invention. The controller includes a signal acquisition module for acquiring the input voltage, inductor current and output voltage of the DC-DC buck converter. The storage module is used to store the preset output voltage target value, error coefficient, and convergence approximation factor; The computation and processing module is used to perform error function calculation, convergence calculation, and voltage gain calculation. The pulse width modulation signal generation module is used to generate control signals to drive the power switching transistors based on the calculated voltage gain.

[0054] In the arithmetic processing module, the process of calculating the error function is as follows: The dynamic equations for each stage of the DC-DC buck converter are established, specifically: ; in, Indicates the first The input voltage of the DC-DC buck converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; The number of stages in a DC-DC buck converter; Based on the aforementioned dynamic equations, the first... The error function of the step-down DC-DC converter is: ; in, Indicates the first Error function of a step-down DC-DC converter; For the first The target output voltage value of the DC-DC buck converter; This represents the error coefficient.

[0055] The convergence operation process is as follows: ; in, Representing the error function Regarding time The derivative; Indicates the first The convergence factor of a step-down DC-DC converter.

[0056] Based on the results of the convergence calculation, and combined with the dynamic changes of the input voltage and inductor current, the actual voltage gain of each stage of the DC-DC buck converter is calculated. The calculation process for the actual voltage gain simultaneously considers the input voltage, target output voltage, state error, and dynamic changes in inductor current of the converter stage. Specifically: ; in, Indicates the first The actual voltage gain of the DC-DC buck converter; Indicates the first Error coefficient of a step-down DC-DC converter; Indicates the first The target output voltage value of the DC-DC buck converter; Indicates the first Output voltage of the step-down DC-DC converter; Indicates the first The filter inductance value of the DC-DC buck converter; Indicates the first The time derivative of the filter inductor current of a step-down DC-DC converter; Indicates the first The input voltage of the DC-DC buck converter.

[0057] The execution process of the pulse width modulation signal generation module includes: The calculated first Actual voltage gain of the DC-DC buck converter As a modulating wave; The modulated wave It is simultaneously input to the comparator with a preset carrier signal for real-time comparison; When the modulated wave When the instantaneous value of the signal is greater than the instantaneous value of the carrier signal, the comparator outputs a high level; otherwise, it outputs a low level, thereby generating a pulse width modulation signal. After the pulse width modulation signal is amplified by the driver circuit, it is applied to the first... The power switching transistors of the DC-DC buck converter The control terminal is used to control its on and off states.

[0058] The DC-DC buck converter setpoint steady-state error convergence control device proposed in Embodiment 2 of the present invention is implemented in the form of dedicated hardware (such as ASIC, FPGA) or embedded software. The device has fixed control logic, strong anti-interference ability, and a certain and fast response speed, which is superior to the control method that relies on a general controller.

[0059] The DC-DC buck converter setpoint steady-state error convergence control device proposed in Embodiment 2 of this invention transforms the method concept into a stable and reliable physical entity. Its improved performance, including high precision, fast response, and strong robustness, along with its modular, standardized, and easily integrated engineering advantages, makes it a preferred solution for significantly enhancing the overall performance of DC-DC buck converter systems.

[0060] The description of the relevant parts of the DC-DC buck converter setpoint steady-state error convergence control device provided in Embodiment 2 of this application can be found in the detailed description of the corresponding parts of the DC-DC buck converter setpoint steady-state error convergence control method provided in Embodiment 1 of this application, and will not be repeated here.

[0061] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that the elements inherent in a process, method, article, or apparatus that includes a list of elements are included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Additionally, portions of the technical solutions provided in the embodiments of this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0062] While specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art can make other modifications or variations based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for controlling the convergence of steady-state errors of a DC step-down converter, characterized by, The method comprises the following steps: acquiring input voltage, inductor current and output voltage of each stage of DC step-down converter; setting output voltage target value, error coefficient and convergence factor for each stage of DC step-down converter; calculating error function of each stage according to difference between output voltage target value and actual output voltage, combining error coefficient; performing convergence operation on error function based on convergence factor, so that error function converges to zero in finite time; calculating actual voltage gain of each stage of DC step-down converter according to result of convergence operation, combining dynamic change of input voltage and inductor current; taking actual voltage gain as modulation signal, generating pulse width modulation signal after comparing with carrier, for driving power switch tube of corresponding stage of DC step-down converter.

2. The method of claim 1, wherein, The process of calculating error function is: establishing dynamic equation of each stage of DC step-down converter, specifically: ； wherein, represents the input voltage of the stage DC step-down converter; represents the input voltage of the stage DC step-down converter; represents the filter inductance value of the stage DC step-down converter; represents the derivative of the filter inductance current with respect to time of the stage DC step-down converter; represents the actual voltage gain of the stage DC step-down converter; is the number of stages of the DC step-down converter; Based on the kinetic equation, define the first The error function of the first-stage DC step-down converter is: ； wherein, represents the error function of the first stage DC step-down converter; is the output voltage target value of the first stage DC step-down converter; represents the error coefficient.

3. The method of claim 2, wherein, The process of convergence operation is: ； wherein, denotes the error function derivative with respect to time ; denotes the convergence factor of the nth step-down DC-DC converter.

4. The method of claim 3, wherein, The process of calculating actual voltage gain simultaneously considers input voltage, output voltage target value, state error and dynamic change of inductor current of the stage of converter, specifically: ； wherein, denotes the actual voltage gain of the denotes the error coefficient of the denotes the output voltage target value of the denotes the output voltage of the denotes the filter inductance value of the denotes the derivative of the filter inductance current with respect to time of the denotes the input voltage of the ​​​​​​​ 5. The method of claim 1, wherein, The process of taking actual voltage gain as modulation signal, generating pulse width modulation signal after comparing with carrier, for driving power switch tube of corresponding stage of DC step-down converter, comprises: The calculated actual voltage gain of the first stage dc buck converter as a modulation wave; modulating the wave a preset carrier signal is simultaneously input into a comparator for real-time comparison; When the modulated wave When the instantaneous value of the signal is greater than the instantaneous value of the carrier signal, the comparator outputs a high level; otherwise, it outputs a low level, thereby generating a pulse width modulation signal. The pulse width modulation signal is amplified by a driving circuit and then applied to the control end of the power switch tube of the step-down DC converter to control the on and off of the power switch tube. The pulse width modulation signal is amplified by a driving circuit and then applied to the control end of the power switch tube of the step-down DC converter to control the on and off of the power switch tube. The pulse width modulation signal is amplified by a driving circuit and then applied to the control end of the power switch tube of the step-down DC converter to control the on and off of the power switch tube.

6. A controller for implementing the control method according to any one of claims 1 to 4, characterized in that, comprises: The signal acquisition module is used for acquiring input voltage, inductor current and output voltage of the DC step-down converter. The storage module is used for storing preset output voltage target value, error coefficient and convergence approximation factor. The operation processing module is used for performing error function calculation, convergence operation and voltage gain calculation. The pulse width modulation signal generation module is used for generating control signal for driving power switch tube according to calculated voltage gain.

7. A DC step-down converter fixed value steady state error convergence control device, characterized by, comprises: The first stage of DC step-down converter is connected to the DC power supply. The controller of claim 5, the number of controllers is equal to the number of DC step-down converters, and each controller independently controls each stage of DC step-down converter.

8. The apparatus of claim 7, wherein, The DC step-down converter is a Buck step-down converter.

9. The apparatus of claim 8, wherein, The Buck step-down converter comprises a power switch tube, a diode, a filter inductor and a filter capacitor. The input end of the power switch tube is connected to the input positive terminal of the stage of converter, the output end of the power switch tube is connected to the cathode of the diode and one end of the filter inductor, the anode of the diode is connected to the common ground, the other end of the filter inductor is used as the output positive terminal of the stage of converter, and the filter capacitor is connected between the output positive terminal and the common ground.

10. The apparatus of any one of claims 7 to 9, which is adapted for a distributed photovoltaic DC microgrid and is used for supplying power to DC loads of different voltage levels.

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