CN110768528B - Control method for smooth switching of working modes of non-reverse Buck-Boost circuit - Google Patents

Abstract

The invention discloses a control method for smooth switching of working modes of a non-inverting Buck-Boost circuit, comprising: determining the working mode currently adopted by the circuit according to an output voltage command value, an input voltage measured value and a control period mode on the circuit ; An automatic voltage regulation module designed according to the mathematical model and mode switching characteristics of the non-inverting Buck-Boost circuit, which can compensate the inductance current command value when the operating mode is switched; According to the mathematical model of the non-inverting Buck-Boost circuit Design an automatic inductor current regulation module. Therefore, the smooth switching of the operating mode of the NIBB circuit can be realized by the control method.

Description

A control for smooth switching of working modes of non-reverse Buck-Boost circuits method

technical field

The invention relates to the technical field of DC-DC converter control, in particular to a mode smooth switching control strategy of a non-inverting Buck-Boost converter.

Background technique

变换器，非反向Buck-Boost变换器的输入输出电压极性相同，从而使得NIBB变换器辅助电源和驱动电路系统较为简单；相比于Zeta变换器、Sepic变换器，NIBB变换器所使用的电感电容等无源元件数量较少，更易于提高功率密度。此外，NIBB变换器两个桥臂的开关管的电压应力分别为输入电压和输出电压，均低于上文所提到的4种变换器。这些特点使得NIBB变换器在开关器件电应力、功率损耗、成本、无源元件体积等方面均具有优势。The non-inverting Buck-Boost converter (NIBB) is a non-isolated DC-DC converter that can realize both step-up and step-down conversion. It has been widely used in recent years. Photovoltaic power generation grid-connected system, electric vehicle charging system, fuel cell grid-connected system, uninterruptible power supply system, low-power power supply, power factor correction converter and other applications. compared to conventional Buck-Boost converters and

The input and output voltages of the non-inverting Buck-Boost converter have the same polarity, which makes the auxiliary power supply and drive circuit system of the NIBB converter simpler; compared with the Zeta converter and the Sepic converter, the NIBB converter uses There are fewer passive components such as inductors and capacitors, making it easier to increase power density. In addition, the voltage stress of the switches of the two bridge arms of the NIBB converter is the input voltage and the output voltage, which are lower than the four converters mentioned above. These characteristics make NIBB converters have advantages in terms of electrical stress of switching devices, power loss, cost, and volume of passive components.

The control object of the present invention is the NIBB converter, and FIG. 1 is a schematic diagram of the NIBB circuit topology. Suppose the switching function of the bridge arm at the input end of the converter (hereinafter referred to as the Buck bridge arm) is S ₁ , and the duty cycle of the switch tube Q ₁ in this bridge arm is d ₁ ; the bridge arm at the output end of the converter (hereinafter referred to as the Boost bridge) The switching function of the bridge arm) is S ₂ , and the duty cycle of the switch tube Q ₃ in this bridge arm is d ₂ . According to theoretical derivation, it can be obtained that under ideal conditions, the NIBB circuit satisfies the differential equation as shown below:

At the same time, the DC operating point of the NIBB circuit can be solved as:

As can be seen from the above formulas, with the different combinations of duty ratios of the Buck bridge arm and the Boost bridge arm, the NIBB circuit has a variety of different operation modes, and the circuit has different characteristics in different operation modes. In practical applications, considering the efficiency problem, when the DC voltage gain of the NIBB circuit is often greater than 1, it works in the mode of d ₂ ≡ 1, which is called Boost mode hereinafter; when the DC voltage gain of the NIBB circuit is less than 1, it works The mode in which d ₁ ≡ 1 is hereinafter referred to as the Buck mode. At the switching point between Boost mode and Buck mode, the duty cycle of each switching device in the NIBB circuit will be very close to 1. Affected by the minimum pulse width problem, the minimum duty cycle of the switching device in the circuit can only reach the minimum duty cycle D _min set according to the characteristics of the switch tube, and the maximum duty cycle can only reach the set value according to the characteristics of the switch tube. The maximum duty cycle is 1-D _min , so when the DC gain of the NIBB circuit is very close to 1, the NIBB circuit will generally work in a quasi-Boost mode or a quasi-Buck mode. In the quasi-Boost mode, the DC gain of the NIBB circuit is greater than 1, d ₂ ≡ 1-D _min ; in the quasi-Buck mode, the DC gain of the NIBB circuit is less than 1, d ₁ ≡ 1-D _min . It can be obtained through theoretical derivation that when the DC voltage gain of the NIBB circuit is the same and the same power supply and load are connected, when the circuit is in Buck mode, the average value of the inductor current of the NIBB circuit is 1-D _min times that in the quasi-Buck mode. ; Similarly, when the circuit is in Boost mode, the average value of the inductor current of the NIBB circuit is 1-D _min times higher than when it is in quasi-Buck mode. Most of the NIBB circuits are accompanied by a duty cycle jump when switching between the above-mentioned operating modes, which often disturbs the output voltage and output current of the system and affects the performance of the circuit.

Compared with the traditional single-mode DC-DC converter, this mode switching problem makes the control strategy of the NIBB circuit more complicated. Therefore, how to achieve smooth switching between different operating modes has become an important issue in the field of NIBB circuit research.

Usually, the control method to solve this problem is to find a variable in Buck mode and Boost mode, and the variable remains continuous when the mode is switched, and then use a unified PI control strategy to control the variable, so that Achieve smooth switching of modes. The disadvantage of this type of method is that the system structure of Buck mode and Boost mode of NIBB circuit is very different. In Boost mode, the NIBB circuit becomes a nonlinear system, and when the load has positive impedance characteristics, the system changes from DC voltage gain to output. The transfer function of the voltage has a right half-plane zero, which makes the closed-loop transfer function of the system as a whole very likely to have a right-half plane pole when the PI control is used in Boost mode, which makes it very difficult to tune the PI parameters, and it is difficult to find a set of general PI The parameters make the control system have good performance in Buck mode and Boost mode.

Aiming at the problems of the prior art that the non-inverting Buck-Boost converter has poor control performance when switching operating modes, and it is difficult to achieve good control performance in a wide range, no effective solution has been proposed yet.

SUMMARY OF THE INVENTION

The purpose of the present invention is to design a control method that can realize smooth switching of working modes of NIBB circuits with better performance. By selecting an appropriate duty cycle combination, different control strategies are designed for different working modes, and the inductance current command value compensation is adopted. In other ways, the smooth switching of the working mode of the NIBB circuit is realized, and the large-scale control performance is good.

The present invention provides a control method for a non-inverting Buck-Boost circuit to solve the problem of poor control performance when switching operating modes caused by the nonlinear characteristics of the NIBB circuit, which is not considered in the prior art. The control method includes the following: steps:

The working mode of the NIBB circuit in the current control cycle is determined by the mode determination module. The input of the mode determination module includes the input voltage _ui of the NIBB circuit and the output voltage command value u _ref of the NIBB circuit; the output of the mode determination module is the working mode of the NIBB circuit. This module collects the input voltage and output voltage command value of the NIBB circuit, and determines the working mode that the NIBB circuit should be in in the current control cycle according to the mode in which the NIBB circuit was in the previous control cycle.

The inductor current command value i _Lref of the NIBB circuit required for the voltage output is automatically adjusted by the automatic voltage regulation module (AVR). The input of the automatic voltage regulation module includes the output voltage u _o of the NIBB circuit and the output voltage command value u _ref of the NIBB circuit; the output of the automatic voltage regulation module is the inductor current command value i _Lref of the NIBB circuit. According to the differential equation satisfied by the NIBB circuit, the control law of AVR in different circuit modes can be designed. According to the above control law, the module can calculate the inductor current command value i _Lref according to the designed control law expression after obtaining the current mode, output voltage u _o and output voltage command value u _ref of the circuit.

The two duty cycles required by the NIBB circuit are output through the automatic current regulation block (ACR). The input quantity of the automatic current adjustment module includes the input voltage u _i of the NIBB circuit, the output voltage command value u _ref of the NIBB circuit, the inductor current command value i _Lref of the NIBB circuit, and the inductor current i _L of the NIBB circuit; the output of the automatic current adjustment module The quantities are the two duty cycles d ₁ and d ₂ of the NIBB circuit. According to the differential equation satisfied by the NIBB circuit, the control law of ACR in different circuit modes can be designed. According to the above control law, the module can obtain the current mode of the circuit, the input voltage _ui , the output voltage command value u _ref , the inductor current command value i _Lref , and the inductor current i _L , and then according to the designed control law expression The two duty cycles d ₁ and d ₂ required by the NIBB circuit are calculated, thereby realizing the control of the NIBB circuit.

The features and advantages of the control method for smooth switching of the working mode of the NIBB circuit proposed by the present invention are:

1. The automatic voltage regulation module and the automatic current regulation module of the control method for the smooth switching of the NIBB circuit operating mode proposed by the present invention have only one adjustable control parameter, and the value of the control parameter has physical meaning and is easier to achieve. Set and adjust the parameters of the control system.

2. The control method for smooth switching of the working mode of the NIBB circuit proposed by the present invention is specially designed based on the mathematical model and circuit parameters of the NIBB circuit, and is a nonlinear control method. Compared with the conventional linear control method based on PI regulator, it has better control performance.

3. The control method for smooth switching of the NIBB circuit operating mode proposed by the present invention performs i _Lref compensation on the inductor current command value in the AVR module according to the circuit operating principle when the NIBB circuit mode is switched. This makes the value of i _Lref also switch when the circuit mode is switched, which can improve the dynamic performance of the control system at the time of mode switching, and reduce the degree of oscillation of the output voltage of the NIBB circuit when the mode is switched.

4. The control method for smooth switching of the working mode of the NIBB circuit proposed by the present invention can also be used as the control method of the NIBB circuit under normal conditions, and also has good performance when the circuit mode does not switch.

Description of drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way, in which:

1 is a schematic diagram of a topology structure of a non-reverse Buck-Boost circuit according to an embodiment of the present invention;

2 is a schematic structural diagram of a control system for a control method for smooth switching of operating modes of an NIBB circuit according to an embodiment of the present invention;

3 is a schematic diagram of an inductor current waveform when the NIBB circuit according to an embodiment of the present invention operates in a Buck mode or a quasi-Buck mode;

4 is a schematic diagram of an inductor current waveform when the NIBB circuit according to an embodiment of the present invention operates in a Buck mode or a quasi-Buck mode;

5 is a flowchart of a mode determination module for a control method for smooth switching of operating modes of an NIBB circuit according to an embodiment of the present invention;

6 is an experimental waveform diagram of a control method for smooth switching of NIBB circuit operating modes according to the present invention;

Fig. 7 is the experimental waveform diagram that adopts the traditional PI control method;

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The topology diagram of the NIBB circuit shown in Figure 1, the circuit topology consists of a group of Buck bridge arms at the input end and a group of Boost bridge arms at the output end connected by an inductor L, and the circuit is connected at the input end and the output end respectively. Has a filter capacitor. FIG. 2 shows the structure diagram of the control system of the control method for smooth switching of the working mode of the NIBB circuit proposed by the present invention. The embodiment of the present invention will be described in detail below by taking FIG. 2 as an example.

1. Analyze the characteristics of NIBB circuit operating mode switching

A schematic diagram of the topology of the NIBB circuit is shown in Figure 1. Generally, in order to reduce circuit loss, a dual-edge modulation strategy is used for PWM generation. In this modulation method, Q ₁ and Q ₃ are always turned on at the same time, which also means that Q ₂ and Q ₄ are always turned off at the same time. In order to facilitate the analysis of this circuit, an average model of the circuit needs to be established. Because the NIBB is a circuit in which power flows in both directions, it actually works in the inductor current continuous mode all the time. Define the switching function of the Buck bridge arm as S ₁ and the switching function of the Boost bridge arm as S ₂ , and the differential equations that can be obtained from the circuit are as follows:

In the control of the NIBB circuit, the circuit has multiple operating modes. The control method divides the NIBB circuit into two types of working modes, each of which has two working modes, 4 working modes in total.

1. Buck mode and quasi-Buck mode

In this mode, the duty cycle _d2 is a constant value. Among them, d ₂ ≡ 1 in Buck mode, and d ₂ ≡ 1-D _min in quasi-Buck mode. In this type of working mode, the inductor current waveform of the NIBB circuit is shown in Figure 3, and the expression of the inductor current waveform can be calculated according to Figure 3:

in

in

It can be calculated according to formula (2), the average inductor current in this type of mode is

If idealized assumptions are made on the output side filter capacitor, it is considered that all harmonic components of the current flowing through Q ₃ are absorbed by the capacitor C _o , and the DC component becomes the output current I _o . The average output current I _o of the NIBB circuit can be calculated as

In the normal Buck mode, d ₂ =1, Q ₃ is fully turned on, and the output current I _o is equal to the average value of the inductor current _IL .

In the quasi-Buck mode, d2=1-D _min , the output current I _o is:

Note that when the circuit is in different modes, even if the output voltage and output current are the same, d ₁ is not the same value. But under the same operating conditions (ie the same load, _ui , u _o ) the average output current I _o of the circuit must be the same. When the converter is not lightly loaded (that is, i _L(t0) is relatively large) and the difference between u _i and u _o is not large (usually when Buck and quasi-Buck have state transitions), the first The value of the binomial value is not very large, and it can be approximated that the following relationship is satisfied at the critical point of mode switching between Buck and quasi-Buck:

Therefore, when the NIBB circuit is at the same operating point, which also means that the circuit has the same average output current I _o , the average inductor current of the circuit in different modes will satisfy the following relationship, that is, the average inductor current in Buck mode is 1-D _min times the average inductor current in quasi-Buck mode.

I _L,buck ≈(1-D _min )I _L,quasi-buck (10)

2. Boost mode and quasi-Boost mode

In this mode, d ₁ is a constant value. Among them, d 1 ≡ 1 in Boost mode, and d ₁ ≡ ₁ -D _min in quasi-Boost mode. In this type of working mode, the inductor current waveform of the NIBB circuit is shown in Figure 4, and the expression of the inductor current waveform can be calculated according to Figure 3:

in

The average inductor current is

The ideal assumption is made on the output side filter capacitor, and it is considered that all harmonic components of the current flowing through Q ₃ are absorbed by the capacitor C _o , and the DC component becomes the output current I _o . Whether it is normal Boost mode or quasi-Boost mode, Q ₃ is in a non-full-time conduction state, so the average output current I _o can be calculated as:

Note that when the circuit is in different modes, even if the output voltage and output current are the same, d ₁ is not the same value. But under the same operating conditions (ie the same load, _ui , u _o ) the average output current I _o of the circuit must be the same. When the converter is not lightly loaded (i.e. i _L(t0) is relatively large) and the difference between u _i and u _o is not large (usually also when the state transition occurs in the Boost mode and the quasi-Boost mode), equations (14) and (15) The value of the second term is not very large, and it can be approximated that the following relationship is satisfied at the critical point where the mode switching between Boost and quasi-Boost occurs

For the same operating conditions, at the critical point of switching between Boost mode and quasi-Boost mode, the following relationship is satisfied between the two duty cycles

d _{2,quasi-boost} ≈(1-D _min )d _2,boost (18)

Therefore, when the NIBB circuit is at the same operating point, which also means that the circuit has the same average output current I _o , the average inductor current of the circuit in different modes will satisfy the following relationship, that is, the average inductor current in Boost mode is 1-D _min times the average inductor current in quasi-Boost mode.

I _L,boost ≈(1-D _min )I _{L,quasi-boost} (19)

2. Design of control system

1. Mode determination module

The input of the mode determination module includes the input voltage _ui of the NIBB circuit and the output voltage command value u _ref of the NIBB circuit; the output of the mode determination module is the working mode mode of the NIBB circuit. The mode determination module will determine according to the process shown in Figure 5.

2. Automatic Voltage Regulation Module (AVR)

The input of the automatic voltage regulation module includes the output voltage u _o of the NIBB circuit and the output voltage command value u _ref of the NIBB circuit; the output of the automatic voltage regulation module is the inductor current command value i _Lref of the NIBB circuit. The variable with serial number n is used to represent the variable in the current control cycle, and the variable with serial number n-1 is used to represent the variable in the previous control cycle. According to the differential equation of the NIBB circuit described by equation (1), the control law of the automatic voltage regulation module can be designed as:

(1) When the current control cycle is the first cycle of system operation, the inductor current command value i _Lref is calculated according to the following expression. Among them, i _o is the output current of the NIBB circuit, and i _Lref-raw is an intermediate variable that does not participate in the input and output and is only used to facilitate the calculation of the control system.

(2) When the current control cycle is not the first cycle of system operation, and the NIBB circuit is in Buck mode or Boost mode, the inductor current command value is calculated according to the following expression. where C _o is the value of the capacitance at the output end of the NIBB circuit, T _c is the control period used by the control method, λ ₁ is the control parameter used in the AVR by the control method, and this parameter can be in the range greater than 0 according to actual needs to adjust the control performance.

(3) When the current control cycle is not the first cycle of system operation, and the NIBB circuit is in a quasi-Buck mode or a quasi-Boost mode, the inductor current command value is calculated according to the following expression. where C _o is the value of the capacitance at the output end of the NIBB circuit, T _c is the control period used by the control method, λ ₁ is the control parameter used in the AVR by the control method, and this parameter can be in the range greater than 0 according to actual needs to adjust the control performance.

3. Automatic current regulation module (ACR)

The input quantity of the automatic current adjustment module includes the input voltage u _i of the NIBB circuit, the output voltage command value u _ref of the NIBB circuit, the inductor current command value i _Lref of the NIBB circuit, and the inductor current i _L of the NIBB circuit; the output of the automatic current adjustment module The quantities are the two duty cycles d ₁ and d ₂ of the NIBB circuit. According to the differential equation of the NIBB circuit described by the formula (1), the control law of the automatic current regulation module can be designed as follows. Among them, λ ₂ is the control parameter used in the ACR by the control method, and the parameter can be adjusted within a range greater than 0 according to actual needs, so as to adjust the control performance.

(1) When the mode determination module determines that the current circuit is in Buck mode, the duty cycle is calculated according to the following expression

(2) When the mode determination module determines that the current circuit is in the quasi-Buck mode, the duty cycle is calculated according to the following expression

(3) When the mode determination module determines that the current circuit is in Boost mode, the duty cycle is calculated according to the following expression

(4) When the mode determination module determines that the current circuit is in the quasi-Boost mode, the duty cycle is calculated according to the following expression

Through the above three modules, the control method for smooth switching of the working mode of the NIBB circuit proposed by the present invention can be realized. FIG. 6 shows the experimental waveforms of applying the method proposed by the present invention to a 10kW, 20kHz two-phase NIBB circuit experimental platform. A scenario is set up in the experiment: keep the input voltage U _i of the NIBB circuit unchanged at 350V, and set the initial output voltage U _o of the NIBB circuit to be 400V. The output voltage U _o is linearly decreased from 400V to 270V within 0.5s, and the output voltage U _o is linearly increased from 270V to 400V within 0.5s. Figure 7 shows the experimental waveforms when the traditional PI control method is used on the same experimental platform.

It can be observed from the experimental results in FIG. 6 that when the working mode of the NIBB circuit is switched, the circuit output voltage oscillation caused by the control method used in the present invention is smaller than that caused by the traditional PI control method, the oscillation time is shorter, and the control Better performance.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope of the appended claims within the limits of the requirements.

Claims (1)

1. A control method for smooth switching of working modes of a non-reverse Buck-Boost circuit is disclosed, wherein the non-reverse Buck-Boost circuitHaving input and output ports, and input DC bus capacitor C_iA switching tube Q directly connected in parallel with the input port₁And a switching tube Q₂Are connected in series to form a Buck bridge arm, the Buck bridge arm and an input direct current bus capacitor C_iParallel output DC bus capacitor C_oA switching tube Q directly connected in parallel with the output port₃And a switching tube Q₄A Boost bridge arm is formed by connecting the output DC bus capacitor C with the Boost bridge arm_oParallel Buck bridge arm middle switch tube Q₁And a switching tube Q₂The connection point of the inductor L and a switching tube Q in a Boost bridge arm₃And a switching tube Q₄Are connected with each other; the control method for the smooth switching of the working modes is characterized by comprising the following steps of:

the method comprises the following steps: outputting a voltage instruction value u according to the current control period through a mode judgment module_refAnd the input voltage u of the non-reverse Buck-Boost circuit acquired in the current control period_iMinimum duty ratio D of non-reverse Buck-Boost circuit_minThe method comprises the following steps that a working mode which is currently adopted by the non-inverting Buck-Boost circuit is judged according to a control cycle mode on the non-inverting Buck-Boost circuit, and specifically comprises the following steps:

(1) if u_ref/u_i<1-2D_minIf so, the Buck mode is adopted in the next control period;

(2) if 1-2D_min≤u_ref/u_i<1-D_minIf the previous control cycle is Buck mode, the next control cycle should adopt Buck mode;

(3) if 1-2D_min≤u_ref/u_i<1-D_minAnd if the previous control cycle is not the Buck mode, the next control cycle should adopt the quasi-Buck mode;

(4) if 1-D_min≤u_ref/u_i<1, adopting a quasi-Buck mode in the next control period;

(5) if u is not more than 1_ref/u_i<1+D_minIf so, the next control period adopts a quasi-Boost mode;

(6) if 1+ D_min≤u_ref/u_i<1+2D_minAnd the last control cycle is notIf the control period is in the Boost mode, the next control period adopts a quasi-Boost mode;

(7) if 1+ D_min≤u_ref/u_i<1+2D_minIf the previous control period is in a Boost mode, the next control period adopts the Boost mode;

(8) if 1+2D_min≤u_ref/u_iIf so, the next control period adopts a Boost mode;

step two: designed according to a mathematical model and mode switching characteristics of a non-reverse Buck-Boost circuit, the inductor current command value i can be subjected to work mode switching_LrefThe automatic voltage regulation module for compensation outputs the required inductive current instruction value i of the non-reverse Buck-Boost circuit_LrefSpecifically, the automatic voltage regulation module is a controller that outputs a voltage command value u based on a current control cycle_refAnd the circuit output voltage u collected in the current control period_oCalculating the inductive current instruction value i by using different calculation methods according to the current working mode of the circuit_LrefThe method specifically comprises the following steps:

(1) if the current control cycle is the first cycle of the control system operation, the inductive current instruction value i_LrefCalculated according to the following expression:

wherein i_o(1) For the output current of the first control cycle of the non-inverting Buck-Boost circuit, i_Lref-rawIs an intermediate variable, i, not involved in input and output, only for facilitating calculations by the control system_Lref-raw(1) Is the value of the first control period of the intermediate variable, i_Lref(1) The calculated value is the first control period of the inductive current instruction value;

(2) if the current control cycle is not the first cycle of the operation of the control system and the current circuit is in a Buck mode or a Boost mode, recording the current cycle as the nth control cycle and the inductive current instruction value i_LrefCalculated according to the following expression:

wherein C is_oThe value of the DC bus capacitance is output for the non-reverse Buck-Boost circuit, T_cControl period, λ, used for the control method₁Control parameter u used in automatic voltage regulation module for the control method_ref(n) is the output voltage instruction value of the non-reverse Buck-Boost circuit in the current control period, u_o(n) is the output voltage of the non-reverse Buck-Boost circuit in the current control period, i_Lref-raw(n-1) is the value of the intermediate variable in the last control period, i_Lref-raw(n) is the value of the intermediate variable in the current control period, i_Lref(n) is a calculated value of the inductive current instruction value in the current control period;

(3) if the current control cycle is not the first cycle of system operation and the current circuit is in a quasi-Buck mode or a quasi-Boost mode, recording the current cycle as the nth control cycle and the inductive current instruction value i_LrefCalculated according to the following expression:

wherein C is_oThe value of the capacitance at the output end of the non-reverse Buck-Boost circuit is T_cControl period adopted for the control method, D_minIs the minimum duty cycle, λ, of the non-inverting Buck-Boost circuit₁Control parameter u used in automatic voltage regulation module for the control method_ref(n) is the output voltage instruction value of the non-reverse Buck-Boost circuit in the current control period, u_o(n) is the output voltage of the non-reverse Buck-Boost circuit in the current control period, i_Lref-raw(n-1) is the value of the intermediate variable in the last control period, i_Lref-raw(n) is the value of the intermediate variable in the current control period, i_Lref(n) is a calculated value of the inductive current instruction value in the current control period;

step three: outputting the duty ratio d required by the non-reverse Buck-Boost circuit through an automatic inductive current regulation module designed according to a mathematical model of the non-reverse Buck-Boost circuit₁And duty cycle d₂The method specifically comprises the following steps: the automatic inductance current regulation module is a nonlinear feedforward controller which outputs a voltage instruction value u based on the current control period_refInductor current command value i_LrefThe circuit input voltage u collected in the current control period_iThe inductive current i collected in the current control period_LAccording to the working mode which is given by the mode judging module in the step one and is currently adopted by the non-reverse Buck-Boost circuit, different calculation methods are used for calculating the duty ratio d of the non-reverse Buck-Boost circuit₁And d₂Wherein the duty ratio d₁Is a switching tube Q₁Duty ratio of (1), switching tube Q₂And a switching tube Q₁Interlock, switch tube Q₂Has a duty ratio of 1-d₁(ii) a Duty ratio d₂Is a switching tube Q₃Duty ratio of (1), switching tube Q₄And a switching tube Q₃Interlock, switch tube Q₄Has a duty ratio of 1-d₂(ii) a Wherein u is_iIs the input voltage u of the non-reverse Buck-Boost circuit in the current control period_refIs the output voltage instruction value i of the non-reverse Buck-Boost circuit in the current control period_LrefThe current is the inductive current instruction value i of the non-reverse Buck-Boost circuit in the current control period_LIs the inductive current, lambda, of the non-reverse Buck-Boost circuit in the current control period₂Control parameter, T, for use in an automatic inductor current regulation module for the control method_cControl period adopted for the control method, D_minThe minimum duty ratio of the non-reverse Buck-Boost circuit is obtained, L is the inductance value of the non-reverse Buck-Boost circuit, and the calculation method is as follows:

(1) if the current circuit is in the Buck mode, the duty ratio is calculated according to the following expression:

(2) if the current circuit is in a quasi-Buck mode, the duty ratio is calculated according to the following expression:

(3) if the current circuit is in a Boost mode, the duty ratio is calculated according to the following expression:

(4) if the current circuit is in a quasi-Boost mode, the duty ratio is calculated according to the following expression:

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