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

Control method for smooth switching of working modes of non-reverse Buck-Boost circuit Download PDF

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CN110768528B
CN110768528B CN201911103898.4A CN201911103898A CN110768528B CN 110768528 B CN110768528 B CN 110768528B CN 201911103898 A CN201911103898 A CN 201911103898A CN 110768528 B CN110768528 B CN 110768528B
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翁幸
赵争鸣
陈凯楠
袁立强
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Tsinghua University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters

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Abstract

The invention discloses a control method for smooth switching of a non-reverse Buck-Boost circuit working mode, which comprises the following steps: judging the current working mode of the circuit according to the output voltage instruction value, the input voltage measured value and a previous control period mode of the circuit; the automatic voltage regulating module is designed according to a mathematical model and mode switching characteristics of the non-reverse Buck-Boost circuit and can compensate the inductive current instruction value during the switching of the working mode; and designing an automatic inductive current regulating module according to a mathematical model of the non-reverse Buck-Boost circuit. Therefore, the control method can realize smooth switching of the working mode of the NIBB circuit.

Description

Control method for smooth switching of working modes of non-reverse Buck-Boost circuit
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-reverse Buck-Boost converter.
Background
A non-inverting Buck-Boost converter (NIBB) is a non-isolated DC-DC converter that can implement both Boost conversion and Buck conversion, and is widely used in recent years in applications such as photovoltaic power generation grid-connected systems, electric vehicle charging systems, fuel cell grid-connected systems, uninterruptible power supply systems, low-power supplies, power factor correction converters, and the like. Compared with the conventional Buck-Boost converter and
Figure GDA0002660618200000011
the input and output voltages of the non-reverse Buck-Boost converter have the same polarity, so that an auxiliary power supply and a driving circuit system of the NIBB converter are simpler; compared with a Zeta converter and a Sepic converter, the NIBB converter has the advantages that the number of passive elements such as inductors, capacitors and the like used by the NIBB converter is small, and the power density is easy to improve. In addition, the voltage stress of the switching tubes of the two bridge arms of the NIBB converter is respectively input voltage and output voltage, which are lower than those of the above-mentioned 4 converters. These characteristics make the NIBB converter advantageous in terms of switching device electrical stress, power loss, cost, passive component volume, etc.
The control object of the invention is an NIBB converter, and FIG. 1 is a schematic diagram of an NIBB circuit topology. Let the switching function of the converter input bridge arm (hereinafter referred to as Buck bridge arm) be S1A switch tube Q in the bridge arm1Duty ratio of d1(ii) a The switching function of the converter output end bridge arm (hereinafter referred to as Boost bridge arm) is S2This isSwitch tube Q in bridge arm3Duty ratio of d2. From theoretical derivation, it can be derived that in an ideal state, the NIBB circuit satisfies the differential equation shown below:
Figure GDA0002660618200000012
meanwhile, the direct-current working point of the NIBB circuit can be solved as follows:
Figure GDA0002660618200000021
according to the above formulas, the NIBB circuit has a plurality of different operation modes with different duty ratio combinations of the Buck bridge arm and the Boost bridge arm, and the circuit has different characteristics in different operation modes. In practical application, considering the efficiency problem, when the direct current voltage gain of the NIBB circuit is often made to be larger than 1, the NIBB circuit works at d2The mode of ≡ 1, hereinafter referred to as Boost mode; when the direct-current voltage gain of the NIBB circuit is smaller than 1, the NIBB circuit works at d1The mode of ≡ 1, hereinafter referred to as 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. Under the influence of the problem of minimum pulse width, the duty ratio of the switching device in the circuit can only reach the minimum duty ratio D set according to the characteristics of the switching tube at the minimumminThe maximum duty ratio can only reach the maximum duty ratio 1-D set according to the characteristics of the switch tubeminTherefore, when the dc gain of the NIBB circuit is very close to 1, the NIBB circuit is generally operated 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, d2≡1-Dmin(ii) a In quasi Buck mode, the DC gain of the NIBB circuit is less than 1, d1≡1-Dmin. It can be derived from theory that when the NIBB circuit has the same DC voltage gain and is connected with the same power supply and load, when the circuit is in Buck mode, the average value of the inductive current of the NIBB circuit is 1-D when the circuit is in quasi-Buck modeminDoubling; similarly, when electricity is usedWhen the circuit is in Boost mode, the average value of the inductive current of the NIBB circuit is 1-D when the NIBB circuit is in quasi-Buck modeminAnd (4) doubling. Most of the NIBB circuits are accompanied by duty cycle jump when switching among the above multiple operating modes, which often causes disturbance to the output voltage and output current of the system and affects the performance of the circuits.
This mode switching problem complicates the control strategy of the NIBB circuit more than a conventional single-mode DC-DC converter. Therefore, how to realize smooth switching between different operation modes becomes an important issue in the research field of the NIBB circuit.
The control method for solving the problem is to find a variable which is in the Buck mode and the Boost mode and is still continuous during mode switching, and then control the variable by using a uniform PI control strategy, so as to realize smooth mode switching. The method has the disadvantages that the Buck mode and the Boost mode of the NIBB circuit have great difference, the NIBB circuit becomes a nonlinear system in the Boost mode, and when a load has a positive impedance characteristic, a transfer function from a direct-current voltage gain to an output voltage of the system has a right half plane zero point, so that a closed-loop transfer function of the whole system is very easy to generate a right half plane pole when PI control is adopted in the Boost mode, PI parameters are very difficult to set, and a set of general PI parameters are difficult to find so that the control system has good performance in both the Buck mode and the Boost mode.
Aiming at the problems that the control performance of a non-reverse Buck-Boost converter in the prior art is poor when the working mode is switched and the large-range control performance is difficult to realize, an effective solution is not provided at present.
Disclosure of Invention
The invention aims to design a control method capable of realizing smooth switching of the working modes of an NIBB circuit with better performance, designs different control strategies aiming at different working modes by selecting proper duty ratio combination, adopts modes of inductive current instruction value compensation and the like, realizes smooth switching of the working modes of the NIBB circuit, and realizes good control performance in a large range.
The invention provides a control method for a non-inverting Buck-Boost circuit, which aims to solve the problem of poor control performance during working mode switching caused by the fact that the non-linear characteristic of an NIBB circuit is not considered in the prior art, and comprises the following steps:
and judging the working mode of the NIBB circuit in the current control period through a mode judging module. The input quantity of the mode decision module comprises an input voltage u of the NIBB circuitiOutput voltage command value u of NIBB circuitref(ii) a The output quantity of the mode decision module is the working mode of the NIBB circuit. The module collects the input voltage and the output voltage instruction value of the NIBB circuit, and judges the working mode of the NIBB circuit in the current control period according to the mode of the NIBB circuit in the previous control period.
Inductive current instruction value i of NIBB circuit required for automatically adjusting voltage output through automatic voltage adjusting module (AVR)Lref. The input of the automatic voltage regulation module comprises the output voltage u of the NIBB circuitoOutput voltage command value u of NIBB circuitref(ii) a The output quantity of the automatic voltage regulation module is an inductive current instruction value i of the NIBB circuitLref. According to the differential equation satisfied by the NIBB circuit, the control rule of the AVR under different circuit modes can be designed. The module can obtain the current mode and output voltage u of the circuit according to the control ruleoAnd an output voltage command value urefThen, calculating an inductive current instruction value i according to the designed control rule expressionLref。
The two duty cycles required by the NIBB circuit are output by an automatic current regulation module (ACR). The input quantity of the automatic current regulation module comprises an input voltage u of an NIBB circuitiOutput voltage command value u of NIBB circuitrefInductor current command value i of NIBB circuitLrefAnd the inductive current i of the NIBB circuitL(ii) a Output quantity of automatic current regulation module is two duty ratios d of NIBB circuit1And d2. According to the differential equation satisfied by the NIBB circuit, the ACR can be designed at different voltagesControl law in road mode. The module can obtain the current mode and the input voltage u of the circuit according to the control ruleiAnd an output voltage command value urefInductor current command value iLrefInductor current iLThen, two duty ratios d required by the NIBB circuit are calculated according to the designed control law expression1And d2Thus, the control of the NIBB circuit is realized.
The control method for the smooth switching of the working modes of the NIBB circuit, provided by the invention, has the characteristics and advantages that:
1. the automatic voltage regulating module and the automatic current regulating module of the control method for the smooth switching of the working modes of the NIBB circuit, which are provided by the invention, only have one adjustable control parameter, and the value of the control parameter has physical significance, so that the parameter of a control system is easier to set and adjust.
2. The control method for the smooth switching of the working modes of the NIBB circuit is specially designed based on the mathematical model and the circuit parameters of the NIBB circuit, and is a nonlinear control method. Compared with the conventional linear control method based on the PI regulator, the method has better control performance.
3. The control method for the smooth switching of the working mode of the NIBB circuit, provided by the invention, performs i on an inductive current instruction value in an AVR module according to the circuit operation principle when the mode of the NIBB circuit is switchedLrefAnd (6) compensation. This causes the circuit mode to switch iLrefThe value of the voltage value is also switched, so that the dynamic performance of the control system at the mode switching moment can be improved, and the oscillation degree of the output voltage of the NIBB circuit during the mode switching is reduced.
4. The control method for the smooth switching of the working mode of the NIBB circuit can also be used as the control method of the NIBB circuit under the conventional condition, and has good performance when the circuit mode is not switched.
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The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
FIG. 1 is a schematic diagram of a non-inverting Buck-Boost circuit topology according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a control system of the control method for smooth switching of the operating modes of the NIBB circuit according to the embodiment of the present invention;
FIG. 3 is a schematic diagram of the inductor current waveform when the NIBB circuit of the embodiment of the present invention operates in Buck mode or quasi-Buck mode;
FIG. 4 is a schematic diagram of the inductor current waveform when the NIBB circuit of the embodiment of the present invention operates in Buck mode or quasi-Buck mode;
FIG. 5 is a flow chart of a mode decision module of the control method for smooth switching of the operating mode of the NIBB circuit according to the embodiment of the present invention;
FIG. 6 is an experimental waveform diagram of the control method for smooth switching of the operating modes of the NIBB circuit according to the present invention;
FIG. 7 is a waveform diagram of an experiment using a conventional PI control method;
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the topology structure of the NIBB circuit is formed by connecting a group of Buck bridge arms at the input end and a group of Boost bridge arms at the output end via an inductor L, and the circuit has a filter capacitor at each of the input end and the output end. Fig. 2 shows a control system structure diagram of the control method for smooth switching of the operation mode of the NIBB circuit proposed by the present invention. An embodiment of the present invention will be described in detail below with reference to fig. 2 as an example.
Firstly, analyzing the characteristics of the NIBB circuit during the switching of the working modes
The schematic 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 adopted for PAnd WM generation. In this modulation method, Q1And Q3Always on at the same time, which also means Q2And Q4Always simultaneously off. To facilitate the analysis of this circuit, an average model of the circuit needs to be established. Since the NIBB is a circuit where power flows bidirectionally, it is actually always operating in inductor current continuous mode. Defining the switching function of a Buck bridge arm in a circuit as S1The switching function of the Boost bridge arm is S2The system of differential equations that can be applied to this circuit is as follows:
Figure GDA0002660618200000061
in the control of the NIBB circuit, the circuit has a plurality of operating modes. The control method divides the NIBB circuit into two major working modes, wherein each working mode has two working modes, and the total working modes are 4 working modes.
Buck mode and quasi-Buck mode
In this mode, the duty ratio d2Is a constant value. Wherein Buck mode d2D in [ identical to ] 1, quasi-Buck mode2≡1-Dmin. In such an operating mode, the inductor current waveform of the NIBB circuit is shown in fig. 3, and the expression of the inductor current waveform can be calculated according to fig. 3 as follows:
Figure GDA0002660618200000062
wherein
Figure GDA0002660618200000063
Wherein
Figure GDA0002660618200000064
Can be calculated according to the formula (2), and the average inductive current in the mode is
Figure GDA0002660618200000071
If an idealized assumption is made about the output side filter capacitance, it is assumed that Q flows through3All harmonic components of the current of (2) are passed through a capacitor CoThe DC component becomes the output current Io. The average output current I of the NIBB circuit can be calculatedoIs composed of
Figure GDA0002660618200000072
Normal Buck mode time d2＝1，Q3Full conduction, output current IoEqual to the average value of the inductor current IL。
Figure GDA0002660618200000073
In quasi-Buck mode, D2 is 1-DminOutput current IoComprises the following steps:
Figure GDA0002660618200000074
note that when the circuit is in different modes, d is the same even if the output voltage, output current are the same1Nor are they the same numerical values. But under the same operating conditions (i.e. same load, u)i、uo) Average output current I of circuitoMust be the same. At non-light load of the converter (i.e. i)L(t0)Relatively large) and ui、uoWhen the difference is not large (generally, when the Buck and the quasi-Buck have state transition), the second terms of the equations (7) and (8) are not very large, and it can be considered that the following relationship is satisfied when the Buck and the quasi-Buck have critical points of mode switching:
Figure GDA0002660618200000075
therefore, when the NIBB circuits are at the same operating point, this also means that the circuits have the same average output current IoThe average inductive current of the circuit in different modes satisfies the following relation that the inductive average current in Buck mode is 1-D of the inductive average current in quasi-Buck modeminAnd (4) doubling.
IL,buck≈(1-Dmin)IL,quasi-buck (10)
Boost mode and quasi-Boost mode
In this mode, d1Is a constant value. Wherein d in Boost mode 11, quasi Boost mode d1≡1-Dmin. In such an operating mode, the inductor current waveform of the NIBB circuit is shown in fig. 4, and the expression of the inductor current waveform can be calculated according to fig. 3 as follows:
Figure GDA0002660618200000081
wherein
Figure GDA0002660618200000082
Figure GDA0002660618200000083
Average inductive current of
Figure GDA0002660618200000084
An idealized assumption is made about the output side filter capacitance, which is considered to flow through Q3All harmonic components of the current of (2) are passed through a capacitor CoThe DC component becomes the output current Io. Either in normal Boost mode or quasi-Boost mode, Q3Are all in non-full time conduction state, so that the average can be calculatedOutput current IoComprises the following steps:
Figure GDA0002660618200000085
note that when the circuit is in different modes, d is the same even if the output voltage, output current are the same1Nor are they the same numerical values. But under the same operating conditions (i.e. same load, u)i、uo) Average output current I of circuitoMust be the same. At non-light load of the converter (i.e. i)L(t0)Relatively large) and ui、uoWhen the difference is not large (usually, when the states of the Boost mode and the quasi-Boost mode are switched), the values of the second terms of the equations (14) and (15) are not large, and the following relationship is approximately satisfied at the critical point of mode switching between the Boost mode and the quasi-Boost mode
Figure GDA0002660618200000086
Figure GDA0002660618200000087
For the same working condition, at the critical point of switching between the Boost mode and the quasi-Boost mode, the following relation is satisfied between the two duty ratios
d2,quasi-boost≈(1-Dmin)d2,boost (18)
Therefore, when the NIBB circuits are at the same operating point, this also means that the circuits have the same average output current IoThe average inductor current of the circuit in different modes satisfies the following relational expression that the average inductor current in the Boost mode is 1-D of the average inductor current in the quasi-Boost modeminAnd (4) doubling.
IL,boost≈(1-Dmin)IL,quasi-boost (19)
Second, design of control system
1. Mode decision module
The input quantity of the mode decision module comprises an input voltage u of the NIBB circuitiOutput voltage command value u of NIBB circuitref(ii) a The output quantity of the mode decision module is the operating mode of the NIBB circuit. The mode decision module will make the decision according to the flow shown in fig. 5.
2. Automatic voltage regulation module (AVR)
The input of the automatic voltage regulation module comprises the output voltage u of the NIBB circuitoOutput voltage command value u of NIBB circuitref(ii) a The output quantity of the automatic voltage regulation module is an inductive current instruction value i of the NIBB circuitLref. The variable in the current control cycle is represented by the variable with the serial number n, and the variable in the last control cycle is represented by the variable with the serial number n-1. 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 follows:
(1) when the current control cycle is the first cycle of system operation, the inductive current instruction value iLrefCalculated according to the following expression. Wherein ioIs the output current of the NIBB circuit, iLref-rawIs an intermediate variable that does not participate in input and output, but is used only to facilitate the calculations performed by the control system.
Figure GDA0002660618200000091
(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. Wherein C isoTaking the value of the capacitance at the output of the NIBB circuit, TcControl period, λ, used for the control method1The control parameter used in AVR of the control method can be adjusted within the range of more than 0 according to actual needs, thereby adjusting the control performance.
Figure GDA0002660618200000101
(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 inductive current instruction value is calculated according to the following expression. Wherein C isoTaking the value of the capacitance at the output of the NIBB circuit, TcControl period, λ, used for the control method1The control parameter used in AVR of the control method can be adjusted within the range of more than 0 according to actual needs, thereby adjusting the control performance.
Figure GDA0002660618200000102
3. Automatic current regulation module (ACR)
The input quantity of the automatic current regulation module comprises an input voltage u of an NIBB circuitiOutput voltage command value u of NIBB circuitrefInductor current command value i of NIBB circuitLrefInductor current i of NIBB circuitL(ii) a Output quantity of automatic current regulation module is two duty ratios d of NIBB circuit1And d2. From the differential equation of the NIBB circuit described by equation (1), the control law of the automatic current regulation module can be designed as follows. Wherein λ2The parameters used in the ACR of the control method can be adjusted within the range of more than 0 according to actual needs, so as to adjust the control performance.
(1) When the mode judging module judges that the current circuit is in the Buck mode, the duty ratio is calculated according to the following expression
Figure GDA0002660618200000103
(2) When the mode judging module judges that the current circuit is in the quasi-Buck mode, the duty ratio is calculated according to the following expression
Figure GDA0002660618200000104
(3) When the mode judging module judges that the current circuit is in the Boost mode, the duty ratio is calculated according to the following expression
Figure GDA0002660618200000111
(4) When the mode judging module judges that the current circuit is in the quasi-Boost mode, the duty ratio is calculated according to the following expression
Figure GDA0002660618200000112
The control method for the smooth switching of the working modes of the NIBB circuit can be realized through the three modules. Figure 6 shows the experimental waveforms for the proposed method for a 10kW, 20kHz biphasic NIBB circuit experimental platform. A scenario was set up in the experiment: make input voltage U of NIBB circuitiKeeping 350V unchanged, and setting the initial output voltage U of the NIBB circuitoIs 400V. Make the output voltage U within 0.5soLinearly decreasing from 400V to 270V, and outputting the output voltage U within 0.5soLinearly from 270V to 400V. Fig. 7 shows experimental waveforms when the conventional PI control method is applied to the same set of experimental platforms.
It can be observed from the experimental results of fig. 6 that when the operation mode of the NIBB circuit is switched, the control method used in the present invention causes less circuit output voltage oscillation, shorter oscillation time, and better control performance than the conventional PI control method.
Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

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 CiA 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 CiParallel output DC bus capacitor CoA 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 armoParallel 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 modulerefAnd the input voltage u of the non-reverse Buck-Boost circuit acquired in the current control periodiMinimum duty ratio D of non-reverse Buck-Boost circuitminThe 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 uref/ui<1-2DminIf so, the Buck mode is adopted in the next control period;
(2) if 1-2Dmin≤uref/ui<1-DminIf the previous control cycle is Buck mode, the next control cycle should adopt Buck mode;
(3) if 1-2Dmin≤uref/ui<1-DminAnd if the previous control cycle is not the Buck mode, the next control cycle should adopt the quasi-Buck mode;
(4) if 1-Dmin≤uref/ui<1, adopting a quasi-Buck mode in the next control period;
(5) if u is not more than 1ref/ui<1+DminIf so, the next control period adopts a quasi-Boost mode;
(6) if 1+ Dmin≤uref/ui<1+2DminAnd 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+ Dmin≤uref/ui<1+2DminIf the previous control period is in a Boost mode, the next control period adopts the Boost mode;
(8) if 1+2Dmin≤uref/uiIf 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 switchingLrefThe automatic voltage regulation module for compensation outputs the required inductive current instruction value i of the non-reverse Buck-Boost circuitLrefSpecifically, the automatic voltage regulation module is a controller that outputs a voltage command value u based on a current control cyclerefAnd the circuit output voltage u collected in the current control periodoCalculating the inductive current instruction value i by using different calculation methods according to the current working mode of the circuitLrefThe 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 iLrefCalculated according to the following expression:
Figure FDA0002660618190000021
wherein io(1) For the output current of the first control cycle of the non-inverting Buck-Boost circuit, iLref-rawIs an intermediate variable, i, not involved in input and output, only for facilitating calculations by the control systemLref-raw(1) Is the value of the first control period of the intermediate variable, iLref(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 iLrefCalculated according to the following expression:
Figure FDA0002660618190000022
wherein C isoThe value of the DC bus capacitance is output for the non-reverse Buck-Boost circuit, TcControl period, λ, used for the control method1Control parameter u used in automatic voltage regulation module for the control methodref(n) is the output voltage instruction value of the non-reverse Buck-Boost circuit in the current control period, uo(n) is the output voltage of the non-reverse Buck-Boost circuit in the current control period, iLref-raw(n-1) is the value of the intermediate variable in the last control period, iLref-raw(n) is the value of the intermediate variable in the current control period, iLref(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 iLrefCalculated according to the following expression:
Figure FDA0002660618190000031
wherein C isoThe value of the capacitance at the output end of the non-reverse Buck-Boost circuit is TcControl period adopted for the control method, DminIs the minimum duty cycle, λ, of the non-inverting Buck-Boost circuit1Control parameter u used in automatic voltage regulation module for the control methodref(n) is the output voltage instruction value of the non-reverse Buck-Boost circuit in the current control period, uo(n) is the output voltage of the non-reverse Buck-Boost circuit in the current control period, iLref-raw(n-1) is the value of the intermediate variable in the last control period, iLref-raw(n) is the value of the intermediate variable in the current control period, iLref(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 periodrefInductor current command value iLrefThe circuit input voltage u collected in the current control periodiThe inductive current i collected in the current control periodLAccording 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 isiIs the input voltage u of the non-reverse Buck-Boost circuit in the current control periodrefIs the output voltage instruction value i of the non-reverse Buck-Boost circuit in the current control periodLrefThe current is the inductive current instruction value i of the non-reverse Buck-Boost circuit in the current control periodLIs 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 methodcControl period adopted for the control method, DminThe 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:
Figure FDA0002660618190000041
(2) if the current circuit is in a quasi-Buck mode, the duty ratio is calculated according to the following expression:
Figure FDA0002660618190000042
(3) if the current circuit is in a Boost mode, the duty ratio is calculated according to the following expression:
Figure FDA0002660618190000043
(4) if the current circuit is in a quasi-Boost mode, the duty ratio is calculated according to the following expression:
Figure FDA0002660618190000044
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