阅读说明：本技术 一种基于Buck电路的滑模控制方法和系统 (Sliding mode control method and system based on Buck circuit ) 是由 李雅静 于 2020-04-02 设计创作，主要内容包括：本发明实施例公开了一种基于Buck电路的滑模控制方法和系统,包括：计算反馈电压值V*和电压偏差值V<Sub>ref</Sub>-V*；建立Buck变换器状态空间方程和电路运行在滑模面上时的状态空间方程；建立滑模面方程和二阶滑模面方程；计算滑模面控制率规则和滑模切换区间。本发明通过在Buck电路中引入滑模控制,并在采样电压中注入电感电流成分,使得滑模面S的计算不再受限于滞后的电容电压,从而使计算的控制变量u能更快地响应负载电流变化,提升Buck电路的反馈调节速度,快速响应信号干扰,增强电路动态性能。(The embodiment of the invention discloses a sliding mode control method and a system based on a Buck circuit, which comprises the following steps: calculating a feedback voltage value V and a voltage deviation value V ref -V; establishing a Buck converter state space equation and a state space equation when a circuit operates on a sliding mode surface; establishing a sliding mode surface equation and a second-order sliding mode surface equation; and calculating a sliding mode surface control rate rule and a sliding mode switching interval. According to the invention, sliding mode control is introduced into the Buck circuit, and an inductive current component is injected into the sampling voltage, so that the calculation of the sliding mode surface S is not limited by lagging capacitance voltage any more, and thus the calculated control variable u can respond to load current change more quickly, the feedback regulation speed of the Buck circuit is increased, signal interference is responded quickly, and the dynamic performance of the circuit is enhanced.)

1. A sliding mode control method based on a Buck circuit is characterized by comprising the following steps:

(1) calculating a feedback voltage value V containing the alternating current information of the inductive current according to the Buck circuit,

V^*＝mi_L+nV_o，

wherein m and n are positive, normal and real numbers i_LFor the current flowing through the inductor, V_oIs the output voltage;

(2) establishing a Buck circuit state space equation according to the feedback voltage value V,

wherein the content of the first and second substances, u ∈ {0,1} is a control variable, the on-off of a switch tube is controlled, and a matrix parameter V is obtained_inFor input voltage, V_oTo output a voltage, V_refIs a reference voltage, V^*Is a feedback voltage value, C is an output capacitor, L is a filter inductor, and R is a load;

(3) establishing a sliding mode surface equation according to a Buck circuit state space equation,

wherein S is a slip form surface;

(4) selecting a second-order sliding mode surface equation according to the sliding mode surface equation,

wherein the sliding mode surface coefficient k is greater than 0;

(5) according to a second-order sliding mode surface equation, a state space equation of the Buck circuit when the Buck circuit operates on the sliding mode surface is defined as follows,

(6) according to a state space equation when the Buck circuit operates on the sliding mode surface, a control rate rule of the sliding mode surface is set as follows,

(7) and (4) calculating a sliding mode switching interval [ l1, l2] and a sliding mode surface coefficient k according to the equations of the steps (2), (5) and (6), and performing optimal sliding mode control on the switch tube according to the sliding mode switching interval [ l1, l2] and the sliding mode surface coefficient k.

2. The sliding-mode control method based on the Buck circuit as claimed in claim 1, wherein the process of calculating the feedback voltage value V containing the alternating current information of the inductor current according to the Buck circuit is as follows:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

3. The sliding mode control method based on the Buck circuit as claimed in claim 1, wherein the Buck circuit characteristics are as follows:

4. the sliding mode control method based on the Buck circuit as claimed in claim 1, wherein the Buck circuit operates on the sliding mode surface under the condition that:

5. the sliding mode control method based on the Buck circuit as claimed in claim 1, wherein the sliding mode switching interval is:

the region between m, n ∈ (0,1), l1 and l2 is the sliding mode switching interval.

6. A sliding mode control system based on a Buck circuit, the system comprising:

a voltage deviation calculation unit for calculating a feedback voltage value V and a voltage deviation value V_ref-V*；

The Buck circuit state space construction unit is used for establishing a Buck converter state space equation and a state space equation when the circuit runs on a sliding mode surface;

the sliding mode surface construction unit is used for establishing a sliding mode surface equation and a second-order sliding mode surface equation;

and the operation unit is used for calculating the sliding mode surface control rate rule and the sliding mode switching interval.

7. The sliding-mode control system based on the Buck circuit as claimed in claim 6, wherein the voltage deviation calculating unit calculates the feedback voltage value V by:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

8. The Buck circuit based sliding mode control system according to claim 6, wherein the system operates on sliding mode surfaces under the conditions:

Technical Field

The invention relates to the technical field of Buck circuits, in particular to a sliding mode control method and system based on a Buck circuit.

Background

With the diversification of electric equipment, more and more equipment, such as artificial smart cards, require a power supply to cope with the situations of large load or sudden change of input voltage. Most of the conventional Buck circuit control uses a pulse width modulation technology, but parameters of the pulse width modulation depend on a system structure, so that when the system is used for dealing with larger signal interference, the system bandwidth has to be reduced, and the dynamic characteristic is poorer.

The voltage conversion circuit is used as a nonlinear system, and a sliding mode control strategy based on a variable structure theory can be adopted. The sliding mode control is a nonlinear control which enables the structure of the system to change constantly, and the sliding mode control performs high-frequency small-amplitude motion, namely sliding mode motion, along a designed track according to a control target. The sliding mode control enables the system to show better robustness when dealing with large signal interference, realizes system convergence stability at a higher speed, and has better dynamic performance and stability.

As shown in fig. 1, the circuit is a Buck circuit block diagram based on a sliding mode control strategy in the prior art, and the circuit mainly collects voltages at two ends of an output capacitor, makes a difference with a reference voltage, and inputs the voltage as a state variable to a sliding mode controller, and the sliding mode controller outputs a control signal u for controlling the switching on and off of a switching tube. The output voltage Vo is the voltage superposition of two ends of the filter capacitor C and the equivalent resistor ESR thereof, and the voltage generated by the capacitor C lags behind the inductance change current.

When Vo is used as a state variable of the sliding mode controller for analysis in a conventional sliding mode control strategy, the calculated control variable lags behind the actual current change, the load current jump cannot be quickly responded, and the adjustment speed of a control system is reduced. According to a conventional sliding mode control strategy, a precise resistor needs to be added into a branch circuit to acquire a current signal, so that the line cost and the layout pressure are increased.

Disclosure of Invention

The embodiment of the invention provides a sliding mode control method and system based on a Buck circuit, wherein an RC loop is connected in series with two ends of a filter inductor to collect an inductive current, and an inductive current component is injected into a sampling voltage, so that the problem that the output voltage of the conventional Buck circuit lags the change of the inductive current is solved, the feedback regulation speed of a control loop is improved, the signal interference is responded quickly, and the dynamic performance of the circuit is enhanced.

The embodiment of the invention discloses the following technical scheme:

the invention provides a sliding mode control method based on a Buck circuit, which comprises the following steps:

(1) calculating a feedback voltage value V containing the alternating current information of the inductive current according to the Buck circuit,

V^*＝mi_L+nV_o，

wherein m and n are positive, normal and real numbers i_LFor the current flowing through the inductor, V_oIs the output voltage;

(2) establishing a Buck circuit state space equation according to the feedback voltage value V,

wherein the content of the first and second substances, u ∈ {0,1} is a control variable, the on-off of a switch tube is controlled, and a matrix parameter V is obtained_inFor input voltage, V_oTo output a voltage, V_refIs reference voltage, V is feedback voltage value, C is output capacitance, L is filter inductance, R is load;

(3) establishing a sliding mode surface equation according to a Buck circuit state space equation,

wherein S is a slip form surface;

(4) selecting a second-order sliding mode surface equation according to the sliding mode surface equation,

wherein the sliding mode surface coefficient k is greater than 0;

(5) according to a second-order sliding mode surface equation, a state space equation of the Buck circuit when the Buck circuit operates on the sliding mode surface is defined as follows,

(6) according to a state space equation when the Buck circuit operates on the sliding mode surface, a control rate rule of the sliding mode surface is set as follows,

(7) and (4) calculating a sliding mode switching interval [ l1, l2] and a sliding mode surface coefficient k according to the equations of the steps (2), (5) and (6), and performing optimal sliding mode control on the switch tube according to the sliding mode switching interval [ l1, l2] and the sliding mode surface coefficient k.

Further, the process of calculating the feedback voltage value V containing the inductor current alternating current information according to the Buck circuit is as follows:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

Further, the Buck circuit characteristics are as follows:

further, the Buck circuit operates on the sliding mode surface under the following conditions:

further, the sliding mode switching interval is as follows:

the region between m, n ∈ (0,1), l1 and l2 is the sliding mode switching interval.

The invention provides a sliding mode control system based on a Buck circuit, which comprises:

a voltage deviation calculation unit for calculating a feedback voltage value V and a voltage deviation value V_ref-V*；

The Buck circuit state space construction unit is used for establishing a Buck converter state space equation and a state space equation when the circuit runs on a sliding mode surface;

the sliding mode surface construction unit is used for establishing a sliding mode surface equation and a second-order sliding mode surface equation;

and the operation unit is used for calculating the sliding mode surface control rate rule and the sliding mode switching interval.

Further, the process of calculating the feedback voltage value V by the voltage deviation calculating unit is as follows:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

Further, the system operates on the sliding surface under the following conditions:

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a block diagram of a Buck circuit based on a sliding mode control strategy in the prior art according to the present invention;

FIG. 2 is a block diagram of a Buck circuit according to the present invention;

FIG. 3 is a schematic diagram of an existing area of a Buck circuit sliding mode according to an embodiment of the invention;

fig. 4 is a schematic structural diagram of a sliding mode control system based on a Buck circuit according to the present invention.

Detailed Description

In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.

As shown in fig. 2, which is a block diagram of the Buck circuit of the present invention, the control target of the Buck circuit is voltage output stabilization.

The method comprises the following steps:

(1) calculating a feedback voltage value V containing the alternating current information of the inductive current according to the Buck circuit,

V^*＝mi_L+nV_o，

wherein m and n are positive, normal and real numbers i_LFor the current flowing through the inductor, V_oIs the output voltage;

(2) establishing a Buck circuit state space equation according to the feedback voltage value V,

wherein the content of the first and second substances, u ∈ {0,1} is a control variable, the on-off of a switch tube is controlled, and a matrix parameter V is obtained_inFor input voltage, V_oTo output a voltage, V_refIs a reference voltage, V^*Is a feedback voltage value, C is an output capacitor, L is a filter inductor, and R is a load;

(3) establishing a sliding mode surface equation according to a Buck circuit state space equation,

wherein S is a slip form surface;

(4) selecting a second-order sliding mode surface equation according to the sliding mode surface equation,

wherein the sliding mode surface coefficient k is greater than 0;

(5) according to a second-order sliding mode surface equation, a state space equation of the Buck circuit when the Buck circuit operates on the sliding mode surface is defined as follows,

(6) according to a state space equation when the Buck circuit operates on the sliding mode surface, a control rate rule of the sliding mode surface is set as follows,

(7) and (4) calculating a sliding mode switching interval [ l1, l2] and a sliding mode surface coefficient k according to the equations of the steps (2), (5) and (6), and performing optimal sliding mode control on the switch tube according to the sliding mode switching interval [ l1, l2] and the sliding mode surface coefficient k.

In the Buck circuit, a resistor R3 and a capacitor C1 form a series branch, the series branch is connected with a filter inductor L in parallel, the series branch is connected between feedback voltage dividing resistors R1 and R2 through R4, and voltage deviation V is achieved_refV is used as an input of the sliding mode controller for controlling the switching tube S1 to be turned on and off.

The process of calculating the feedback voltage value V containing the alternating current information of the inductive current according to the Buck circuit comprises the following steps:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

Because the waveform of the capacitor voltage is the same as that of the inductor current, the voltage at the two ends of the C1 can be collected to represent the inductor current, and the use of a precision resistor in a main loop is avoided. And a current ripple signal is injected into the feedback voltage, so that the phase of the acquired signal is improved, and the phase calculated by the sliding mode surface S is advanced, so that the calculated control variable u can respond to system change more quickly, and the response speed is improved.

The Buck circuit characteristics are as follows:

in the invention, the second-order sliding mode control technology can meet the requirements of quick response and robustness of the system, and the sliding mode surface function is combined by the output voltage deviation and the derivative thereof.

The state space equation when the circuit operates on the sliding mode surface is used for solving a first constant coefficient linear differential equation to obtain:

V_ref-nV_o＝mi_L+x₁(0)e^-kt，

wherein x is₁(0) Is x₁The state value at the time when t is 0.

Due to the fact thatThe DCR is extremely small in milliohm level and is divided by the resistor, so m<<1，mi_LTending to 0. Thus, at k>At 0, output voltageV_oThe reference voltage tends to be obtained in an exponential mode, and the stability of the Buck circuit can be realized through sliding mode control.

For the Buck circuit of the invention, when S is>At 0, output voltage V_oWhen the reference voltage is lower than the reference voltage, the switching tube S1 is turned on, i.e., u is 1; when S is<At 0, output voltage V_oAbove the reference voltage, the switching tube S1 is turned off, i.e., u is equal to 0. Therefore, the sliding mode surface control rate rule is defined as:

to ensure that the trajectory remains on the sliding line, the Buck circuit must comply with the conditions of existence derived from the lyapunov second method, which determine the progressive stability of the system, so that the conditions under which the Buck circuit operates on the sliding surface are:

calculating a sliding mode switching interval as follows through a simultaneous space state equation and a sliding mode surface equation:

wherein m, n ∈ (0,1), straight lines l1, l2 are parallel, and l2 passes through point (V)_ref0), the area between l1 and l2 is the sliding mode switching interval, as shown in fig. 3.

When x₁Tending towards 0 at exponential speed, i.e. line x₁0. Provided that l1, l2 and x₂The axes have an intersection point, i.e. the slope is not infinite, and the system can reach the sliding mode surface S equal to 0. When the slope is infinite, the method can be obtained

Calculate out

In practical application, the sliding mode surface coefficient k enabling the initial arrival point to be in the sliding interval is selected as much as possible.

As shown in fig. 4, which is a schematic structural diagram of a sliding mode control system based on a Buck circuit according to the present invention, the system includes:

a voltage deviation calculation unit for calculating a feedback voltage value V and a voltage deviation value V_ref-V*；

The Buck circuit state space construction unit is used for establishing a Buck converter state space equation and a state space equation when the circuit runs on a sliding mode surface;

the sliding mode surface construction unit is used for establishing a sliding mode surface equation and a second-order sliding mode surface equation;

and the operation unit is used for calculating the sliding mode surface control rate rule and the sliding mode switching interval.

The process of calculating the feedback voltage value V by the voltage deviation calculating unit is as follows:

(1) from the frequency domain analysis, the voltage across the inductor L is calculated as,

u_L＝(sLL+DCR)i_L，

where, s ═ j ω is a complex parameter variable called complex frequency, the inductor L is composed of an ideal inductor LL and an equivalent resistance DCR, and the current flowing through the inductor is i_L；

(2) Calculating the capacitance C₁The voltage across the two terminals is such that,

(3) let the circuit parameterThen the variable u_C1And i_LIn a direct proportion to the total weight of the composition,

u_C1＝DCR*i_L；

(4) calculating C₁The voltage of the alternating current component at both ends is,

(5) calculating the feedback voltage value V of the alternating information of the inductive current,

wherein the content of the first and second substances,m and n are positive, constant real numbers.

The conditions for the system to run on the sliding surface are as follows:

the foregoing is only a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the invention, and such modifications and improvements are also considered to be within the scope of the invention.