CN112583266A - Model prediction control method, system, equipment and medium of Buck-Boost converter - Google Patents
Model prediction control method, system, equipment and medium of Buck-Boost converter Download PDFInfo
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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 embodiment of the invention discloses a model prediction control method, a system, equipment and a medium of a Buck-Boost converter. The optimization process of the cost function replaces modulation and mode detection, so that the design is simplified to a great extent and is easy to realize, smooth transition can be realized when the Buck mode and the Boost mode are switched, and quick response can be made to transient changes of lines and loads.
Description
Technical Field
The embodiment of the invention relates to the technical field of power electronic conversion, in particular to a model prediction control method, a system, equipment and a medium for a Buck-Boost converter.
Background
A four-switch Buck-Boost converter, as a non-inverting Buck-Boost converter, has the advantages of a wide operating voltage range, the ability to step up and down the input voltage, and it also allows bi-directional power flow, making such a converter suitable for many applications, such as battery power applications, solar power generation systems, and consumer electronics with universal serial bus power transfer (USB-PD) designs. There are three modes of operation of this type of converter, namely buck mode, boost mode and transitional buck-boost mode (a combination of boost and buck modes). The two switch bridge arms are independently switched and controlled, and equivalently work in a Buck circuit (Buck) mode or a Boost circuit (Boost) mode, so that the converter can realize the functions of voltage reduction or voltage Boost according to the requirements of working conditions.
Many existing controllers for four-switch Buck-Boost converters are implemented by allowing multi-mode operation. However, the system has a problem of mode conversion. In general, neither conventional buck nor boost converters can operate at a voltage ratio of 1:1 at high power conditions using N-FETs due to minimum/maximum limits on duty cycle and non-ideality of parameters present in the power stage. This can lead to an uncontrollable interval, i.e. dead zone, in the system. Undesirable output transients may occur when the circuit passes through a region where the input voltage is very close to the output voltage. The four-switch Buck-Boost converter system also inherits the mode conversion problem with large current and output voltage ripple.
To overcome the mode conversion problem of four-switch Buck-Boost converters, some controllers introduce additional modes of operation, such as a Buck-Boost mode of operation, which is only activated when the circuit passes through the mode conversion operation. These methods, while reducing the dead space, also introduce a number of problems such as inefficiency during Buck-Boost operation and complex control structures that require more design effort.
More importantly, the above-described methods suffer from design complexity and reliance on accurate and fast pattern detection. In such controllers, since Buck and Boost have different transfer functions and different input/output impedance characteristics, designers need to design separate compensation stages for Buck and Boost modes to achieve better loop performance. Another additional requirement is the mode detection design, which is usually done by duty cycle or direct voltage detection. This relies on accurate synchronization time control and may be affected by loop transient performance. Due to the trade-off between noise immunity and transient behavior, it is much more difficult to achieve reliable mode detection with fast response than is desirable.
Disclosure of Invention
Therefore, the embodiment of the invention provides a model predictive control method, a system, equipment and a medium of a Buck-Boost converter, so as to solve the technical problems of complex control structure, low efficiency during Buck-Boost operation, reliable mode detection depending on difficult-to-realize quick response and the like caused by the fact that a control loop and a modulator need to be respectively designed for each working mode in the mode conversion control technology of the traditional four-switch Buck-Boost converter, and truly realize the characteristic of seamless switching.
In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:
according to a first aspect of the embodiments of the present invention, there is provided a model predictive control method of a Buck-Boost converter, the method including: detecting the input voltage V of the Buck-Boost converter in the current control period kin(k) An output voltage Vo(k) And the inductor current IL(k) (ii) a Using a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Respectively predicting the inductive current I of the next control period k +1 through a discrete time prediction modelL(k + 1); utilizing the inductor current I of the next control period k +1 corresponding to each switch state vectorL(k +1) and the maximum allowable inductor current value imaxComparing and updating current limiting weighting factor lambdai_limit(ii) a Using a predetermined reference voltage VrefAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref(ii) a Using the inductor current reference value iL_refThe inductor current I of the next control period k +1L(k +1), updated current limit weighting factor lambdai_limitCalculating and storing a value function value g corresponding to each switch state vector; and selecting and outputting the minimum value function value gminThe switch state of the corresponding switch state vector is taken as the selected switch state SSoptAnd controlling each switch of the Buck-Boost converter in the next control period k + 1.
Further, the Buck-Boost converter includes: first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4The first switch tube S1First end of and the second switch tube S2The first end of the first switch tube S is connected to form a first bridge arm1And the second switch tube S2Respectively connected to the positive and negative poles of a power supply, and a third switching tube S3First end of and the fourth switching tube S4The first ends of the first and second switching tubes S are connected to form a second bridge arm3And the fourth switching tube S4The second end of the second switch tube S is respectively connected to the positive end and the negative end of the load resistor2Second end of and the fourth switching tube S4The second ends of the first and second bridge arms are connected to form a third bridge arm, a fourth bridge arm is formed by the first and second bridge arms in a communication mode, an inductor is arranged on the fourth bridge arm, a power-side single-phase bridge arm point ph1 is formed by the fourth bridge arm and a first connecting point of the first bridge arm, and the first connecting point is located on the first switching tube S1And the second switch tube S2A second connection point of the fourth bridge arm and the second bridge arm forms an output-side single-phase bridge arm point ph2, and the second connection point is located at the third switching tube S3And the fourth switching tube S4And a power supply side capacitor and an output side capacitor are respectively connected in parallel on the power supply side and the output side of the Buck-Boost converter.
Further, the algorithm formula of the discrete time prediction model is as follows:
wherein, TSIs the sampling time, R represents the load resistance of the Buck-Boost converter, RCExpressing the internal resistance of the output side capacitor, L expressing the inductance value of the inductor of the Buck-Boost converter, u1(t) represents the voltage of the single-phase bridge arm point ph1 on the power supply side of the Buck-Boost converter at the time t in the current control period k,
u2(t) represents the voltage of the single-phase bridge arm point ph2 at the output side of the Buck-Boost converter at the time t in the current control cycle k,
dauxwhich represents the prediction coefficients of the video signal,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off denotes that the switch tube is open, on denotes that the switch tube is closed, i belongs to {1,2}, and t belongs to k.
Further, the current limit weighting factor λi_limitThe updating method comprises the following steps: the inductor current I according to the next control period k +1L(k +1) and the maximum allowable inductor current value imaxCurrent limiting weighting factor lambda is updated according to comparison resultsi_limit(ii) a When the inductor current I of the next control period k +1L(k +1) is less than the maximum allowable inductor current value imaxWhile, the current limit weighting factor lambdai_limitUpdating to 0; and when the inductive current IL(k +1) is greater than or equal to the maximum allowable inductor current value imaxWhile, the current limit weighting factor lambdai_limitUpdated to greater than 1000max (| i)L_ref-IL(k+1)|)。
Further, the value function formula for calculating the value function value g is:
g＝|iL_ref-IL(k+1)|+λi_limit。
further, the first switch state vector AS1On/off state of
Second switch state vector AS2On-off state
Third switch state vector AS3On-off state
Fourth switch state vector AS4On-off state
Respectively as follows:
wherein 0 represents that the switch tube is opened, and 1 represents that the switch tube is closed.
Further, the method comprises: sequentially utilizing the first switch state vector AS by cyclic assignment j1The second switch state vector AS2The third switch state vector AS3The fourth switch state vector AS4Predicting the inductor current I of the next control period k +1L(k +1), updating current limiting weighting factor lambdai_limitAnd calculating a value of the cost function g, wherein j sequentially takes 1,2, 3, 4 and 5, and when j takes 5, stopping the circulation process.
According to a second aspect of embodiments of the present invention, there is provided a model predictive control system of a Buck-Boost converter, the system comprising: the detection module is used for detecting the input of the Buck-Boost converter in the current control period kVoltage Vin(k) An output voltage Vo(k) And the inductor current IL(k) (ii) a An inner loop control module for utilizing a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Respectively predicting the inductive current I of the next control period k +1 through a discrete time prediction modelL(k + 1); utilizing the inductor current I of the next control period k +1 corresponding to each switch state vectorL(k +1) and the maximum allowable inductor current value imaxComparing and updating current limiting weighting factor lambdai_limit(ii) a An outer loop control module for utilizing a preset reference voltage VrefAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref(ii) a A cost function calculation module for utilizing the inductor current reference value iL_refThe inductor current I of the next control period k +1L(k +1), updated current limit weighting factor lambdai_limitCalculating and storing a value function value g corresponding to each switch state vector; and a switch state selection and output module for selecting the minimum value function value gminThe switch state of the corresponding switch state vector is taken as the selected switch state SSoptAnd controlling each switch of the Buck-Boost converter in the next control period k + 1.
According to a third aspect of embodiments of the present invention, there is provided a model predictive control apparatus of a Buck-Boost converter, the apparatus including: a processor and a memory; the memory is to store one or more program instructions; the processor is used for executing one or more program instructions to execute any method step in the model predictive control method of the Buck-Boost converter.
According to a fourth aspect of embodiments of the present invention, there is provided a computer storage medium having one or more program instructions embodied therein for performing any one of the method steps of the above method for model predictive control of a Buck-Boost converter.
The embodiment of the invention has the following advantages: the embodiment of the invention does not need to design a control loop and a modulator for each working mode respectively like the traditional technology, but adjusts the control object along the given reference value by optimally selecting the switch state of each control period. The optimization process of the cost function replaces modulation and mode detection, so that the design is simplified to a great extent and is easy to realize, smooth transition can be realized when the Buck mode and the Boost mode are switched, and quick response can be made to transient changes of lines and loads.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
Fig. 1 is a schematic diagram of a logic structure of a model predictive control system of a Buck-Boost converter according to an embodiment of the present invention;
fig. 2 is a circuit diagram of a Buck-Boost converter provided in an embodiment of the present invention;
fig. 3 is a schematic flowchart of a model predictive control method of a Buck-Boost converter according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of a model predictive control method for a Buck-Boost converter according to another embodiment of the present invention;
FIG. 5a is a schematic diagram of the step change of the output voltage of MATLAB/Simulink simulation according to an embodiment of the present invention; FIG. 5b is a schematic diagram of the change of the inductor current under the step change of the output voltage shown in FIG. 5a according to an embodiment of the present invention;
fig. 6a is a schematic diagram of an input voltage step change of MATLAB/Simulink simulation according to an embodiment of the present invention, and fig. 6b and fig. 6c are schematic diagrams of a result of MATLAB/Simulink simulation of an output voltage and an inductor current under the input voltage step change as shown in fig. 6a, respectively, according to an embodiment of the present invention;
fig. 7a and 7b are schematic diagrams of MATLAB/Simulink simulation results of output voltage and load current under load step change according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular system structures, interfaces, techniques, etc. in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
The embodiment of the invention provides a model predictive control system of a Buck-Boost converter aiming at a control strategy of a direct current-direct current converter, so that the four-switch Buck-Boost converter is controlled to be smoothly switched between a Buck mode and a Boost mode.
Referring to fig. 1, a model predictive control system of a Buck-Boost converter provided by an embodiment of the present invention includes: the device comprises a detection module 01, an inner ring control module 02, an outer ring control module 03, a value function calculation module 04 and a switch state selection and output module 05.
In the model predictive control system of the Buck-Boost converter disclosed by the embodiment of the invention, the inner ring control module 02 is a controller for predicting current and is communicated withAnd (4) performing over-model prediction control to quickly adjust the inductive current. The outer loop control module 03 is a voltage loop formed based on a proportional-integral regulator, which utilizes a preset reference voltage VrefCalculating the reference value i of the inductor current required by the inductor by the error between the output voltage of the converter and the output voltage of the converterL_refTo perform inner loop inductor current prediction control.
For the internal prediction loop, the input voltage V of the Buck-Boost converter in the current control period k is detected by using the current sampling period (namely, the current control period k) through the established current prediction model (namely, the discrete time prediction model) of the next sampling period (namely, the next control period)in(k) An output voltage Vo(k) And the inductor current IL(k) To make a current prediction so that the value of the minimum cost function gminThe switch state of the corresponding switch state vector is taken as the selected switch state SSoptEach switch of the Buck-Boost converter is to be controlled at the next sampling instant, i.e. the next control period k +1, for each switch of the Buck-Boost converter.
Referring to fig. 2, the Buck-Boost converter disclosed in the embodiment of the present invention is a four-switch Buck-Boost converter, and specifically includes: first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4A first switch tube S1First end of and a second switch tube S2The first end of the first switch tube S is connected to form a first bridge arm1And a second switch tube S2The second ends of the first and second switching tubes are respectively connected to the positive pole and the negative pole of a power supply, and the third switching tube S3First end and fourth switch tube S4The first ends of the first and second bridge arms are connected to form a second bridge arm, and a third switching tube S3And a fourth switching tube S4Is respectively connected to the positive terminal and the negative terminal of the load resistor, and a second switching tube S2Second end and fourth switch tube S4The second end of the first bridge arm is connected to form a third bridge arm, the first bridge arm is communicated with the second bridge arm to form a fourth bridge arm, an inductor is arranged on the fourth bridge arm, a first connecting point of the fourth bridge arm and the first bridge arm forms a power-side single-phase bridge arm point ph1, and the first connecting point is positioned at a first openingClosing pipe S1And a second switch tube S2A second connection point of the fourth bridge arm and the second bridge arm forms an output-side single-phase bridge arm point ph2, and the second connection point is located at the third switching tube S3And a fourth switching tube S4And a power supply side capacitor and an output side capacitor are respectively connected in parallel on the power supply side and the output side of the Buck-Boost converter.
Corresponding to the model predictive control system of the Buck-Boost converter, the embodiment of the invention also discloses a model predictive control method of the Buck-Boost converter. The model predictive control method of the Buck-Boost converter disclosed in the embodiment of the invention is described in detail below with reference to the above-described model predictive control system of the Buck-Boost converter.
Referring to fig. 3, a method for model predictive control of a Buck-Boost converter provided by an embodiment of the present invention includes: detecting the input voltage V of the Buck-Boost converter in the current control period k through the detection module 01in(k) An output voltage Vo(k) And the inductor current IL(k) (ii) a Utilizing a first switch state vector AS through the inner loop control module 021A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Respectively predicting the inductive current I of the next control period k +1 through a discrete time prediction modelL(k + 1); utilizing the inductor current I of the next control period k +1 corresponding to each switch state vectorL(k +1) and the maximum allowable inductor current value imaxComparing and updating current limiting weighting factor lambdai_limit(ii) a Using a predetermined reference voltage V by the outer loop control module 03refAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref(ii) a By means of a merit function calculation module 04 using the reference value i of the inductor currentL_refThe inductor current I of the next control period k +1L(k +1), updated current limit weighting factor lambdai_limitCalculating and storing a value function value g corresponding to each switch state vector; and selecting and outputting the minimum value function value g through the switch state selection and output module 05minOf corresponding switch state vectorsThe switching state being selected switching state SSoptAnd controlling each switch of the Buck-Boost converter in the next control period k + 1.
Further, the algorithm formula of the discrete time prediction model disclosed in the embodiment of the present invention is as follows:
wherein, TSIs the sampling time, R represents the load resistance of the Buck-Boost converter, RCExpressing the internal resistance of the output side capacitor, L expressing the inductance value of the inductor of the Buck-Boost converter, u1(t) represents the voltage of the single-phase bridge arm point ph1 on the power supply side of the Buck-Boost converter at the time t in the current control period k,
u2(t) represents the voltage of the single-phase bridge arm point ph2 at the output side of the Buck-Boost converter at the time t in the current control cycle k,
dauxwhich represents the prediction coefficients of the video signal,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off denotes that the switch tube is open, on denotes that the switch tube is closed, i belongs to {1,2}, and t belongs to k.
Further, the following describes in detail the establishment of the discrete-time prediction model disclosed in the embodiments of the present invention. Firstly, considering the state when S3 is closed and S4 is open, the inductance current I of the Buck-Boost converterLThe continuous-time model of (t) may be represented by the following equation:
wherein L represents inductance of Buck-Boost converter, RLRepresenting the internal resistance of the inductance, u, of the inductance of the Buck-Boost converter1(t) represents the voltage of the single-phase bridge arm point ph1 on the power supply side of the Buck-Boost converter at the time t in the current control period k,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off indicates that the switch tube is open, on indicates that the switch tube is closed, and t is belonged to k and Vin(t) is the input voltage V of the Buck-Boost converter at the moment t in the current control period koAnd (t) is the output voltage of the Buck-Boost converter at the time t in the current control period k.
In addition, the output end capacitance current I of the four-switch Buck-Boost converter at the time t in the current control period kC(t) output terminal capacitance voltage VC(t) output voltage VoThe relationship of (t) is:
IC(t)RC+VC(t)＝Vo(t) formula (2)
Wherein R isCAnd the internal resistance of the output side capacitor is represented, R represents the load resistance of the Buck-Boost converter, C is the capacitance value of the output end capacitor of the Buck-Boost converter, and t belongs to k.
The capacitance voltage V of the output end of the Buck-Boost converter at the moment t in the current control period k can be obtained by the formulas (2) to (4)C(t) and the inductor current IL(t) is given by:
from the formula (3) and the formula (4), the output voltage V of the Buck-Boost converter at the time t in the current control period k can be obtainedo(t) and the inductor current IL(t) output terminal capacitance voltage VC(t) is given by:
by combining equation (1) and equation (6), it can be derived:
next, considering the state when S3 is open and S4 is closed, there are:
thus, in combination of formulas (7) and (8), it is possible to obtain:
wherein u is2(t) represents the voltage of the single-phase bridge arm point ph2 at the output side of the Buck-Boost converter at the time t in the current control cycle k,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off indicates that the switch tube is open, on indicates that the switch tube is closed, and t ∈ k.
Also, in combination of formulas (5) and (9), it can be found that:
combining formulas (6) and (10), the output voltage V of the Buck-Boost converter at the time t in the current control period ko(t) can be expressed as:
according to the Euler method, the inductive current I of the Buck-Boost converter in the next control period k +1 is deducedL(k +1), output terminal capacitance voltage VCThe discrete prediction model formula of (k +1) is shown in formulas (14) to (15):
wherein, TSIs the sampling time, dauxWhich represents the prediction coefficients of the video signal,
i∈{1,2}，t∈k。
output voltage V of Buck-Boost converter in current control period ko(k) Andoutput terminal capacitance voltage VC(k) Can be expressed as follows:
the algorithm formula of the prediction model of the inductor current (i.e. the discrete time prediction model for predictive control established by the embodiment of the present invention) obtained from the formula (14) and the formula (16) is as follows:
wherein, TSIs the sampling time, R represents the load resistance of the Buck-Boost converter, RCExpressing the internal resistance of the output side capacitor, L expressing the inductance value of the inductor of the Buck-Boost converter, u1(t) represents the voltage of the single-phase bridge arm point ph1 on the power supply side of the Buck-Boost converter in the current control period k,
u2(t) represents the voltage of the single-phase bridge arm point ph2 on the output side of the Buck-Boost converter in the current control period k,
dauxwhich represents the prediction coefficients of the video signal,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off denotes that the switch tube is open, on denotes that the switch tube is closed, i belongs to {1,2}, and t belongs to k.
Further, in the embodiment of the present invention, the value function formula for calculating the value function value g is as follows:
g＝|iL_ref-IL(k+1)|+λi_limit。
referring to fig. 1 and 2, the value function in the embodiment of the present invention includes two terms, the first term is a main term, the given value of the inductor current is tracked through output voltage regulation, and the reference value i of the inductor current is obtainedL_refGiven that the calculation results from the voltage control outer loop, the second term is used for overcurrent limiting, wherein the current limiting weighting factor λi_limitThe update formula of (2) is as follows:
where inf represents an infinite value, imaxRepresenting the maximum allowable inductor current value.
Specifically, in the embodiment of the present invention, the current limit weighting factor λi_limitThe updating method comprises the following steps: inductor current I according to the next control period k +1L(k +1) and the maximum allowable inductor current value imaxCurrent limiting weighting factor lambda is updated according to comparison resultsi_limit(ii) a When the inductor current I of the next control period k +1L(k +1) is less than the maximum allowable inductor current value imaxTime, current limit weighting factor lambdai_limitUpdating to 0; and the inductor current I of the next control period k +1L(k +1) is greater than or equal to the maximum allowable inductor current value imaxTime, current limit weighting factor lambdai_limitUpdated to greater than 1000max (| i)L_ref-IL(k +1) |), it is sufficient to choose a value large enough to be much larger than the maximum value of the first term of the cost function value g.
In the above design, by adding the weighting factor related to the current limit to the cost function, three advantages will be brought: 1) the function of fast and smooth current limiting can be realized without closing a component, but the current can be clamped to prevent the current from rising; 2) allowing overcurrent protection to be implemented in each switching cycle; 3) the robustness of the system is improved by using the predicted current values rather than just the detected currents.
Further, the embodiment of the invention provides model predictive control of a four-switch Buck-Boost converterThe flow chart of the method is shown in fig. 4, using a cyclic assignment j in turn using a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Predicting the inductor current I of the next control period k +1L(k +1), updating current limiting weighting factor lambdai_limitAnd calculating a value of the cost function g, wherein when j sequentially takes 1,2, 3, 4 and 5, and j sequentially takes 1,2, 3 and 4, a first switch state vector AS is correspondingly taken respectively1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Specifically, the input voltage V of the Buck-Boost converter in the current control period k is detected firstlyin(k) An output voltage Vo(k) And the inductor current IL(k) (ii) a Using a predetermined reference voltage VrefAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref. When the circulation flow begins, the variable j is assigned with 1, and after the circulation flow is entered, a first switch state vector AS is selected1Predicting the corresponding inductive current I of the next control period k +1 according to the algorithm formula of the discrete time prediction model corresponding to the corresponding switch stateL(k +1), and then according to the current limit weighting factor lambdai_limitUpdating current limit weighting factor lambda by the updating formulai_limitTo prevent overcurrent; calculating the value of the cost function value g when j is 1 according to the formula, and storing gjAnd selecting a second switch state vector AS by changing the variable j to j +12And repeating the steps according to the corresponding switch states, and repeating the steps in the same way until j equals 4 to predict three switch vectors and obtain the value function values g corresponding to the three switch vectors. When j takes 5, jumping out and stopping the circulation flow, selecting and outputting a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Value of value g obtained correspondingly1～g4Middle minimum value of value gminThe corresponding switch state is taken as the selected switch state SSoptFor said next control period k +1And each switch of the Buck-Boost converter is controlled.
Specifically, a first switching tube S of a four-switch Buck-Boost converter (Buck-Boost converter)1A second switch tube S2A third switch tube S3And a fourth switching tube S4The corresponding switch states are respectively: SS1、SS2、SS3、SS4The four-switch Buck-Boost converter has four available switching vectors which are respectively a first switching state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4. First switch state vector AS1On/off state of
Second switch state vector AS2On-off state
Third switch state vector AS3On-off state
Fourth switch state vector AS4On-off state
Respectively as follows:
wherein 0 represents the switch tube is open, 1 represents the switch tube is closed, SS1 1、SS2 1、SS3 1、SS4 1Respectively, a first switch state vector AS1On/off state of
First switch tube S in1A second switch tube S2A third switch tube S3And a fourth switching tube S4Corresponding switch state, SS1 2、SS2 2、SS3 2、SS4 2Respectively, second switch state vector AS2On/off state of
First switch tube S in1A second switch tube S2A third switch tube S3And a fourth switching tube S4Corresponding switch state, SS1 3、SS2 3、SS3 3、SS4 3Respectively, a first switch state vector AS3On/off state of
First switch tube S in1A second switch tube S2A third switch tube S3And a fourth switching tube S4Corresponding switch state, SS1 4、SS2 4、SS3 4、SS4 4Respectively, second switch state vector AS4On-off state SS of1 2 ～4First switch tube S in1A second switch tube S2A third switch tube S3And a fourth switching tube S4The corresponding switch state.
Corresponding to the above embodiments, the present invention further provides an entropy-based convolutional neural network pooling device, including: a processor and a memory; the memory is to store one or more program instructions; the processor is used for executing one or more program instructions to execute the model predictive control method of the Buck-Boost converter.
In correspondence with the above embodiments, embodiments of the present invention also provide a computer storage medium containing one or more program instructions therein. Wherein one or more program instructions are used to execute a method of model predictive control of a Buck-Boost converter as described above.
In an embodiment of the invention, the processor may be an integrated circuit chip having signal processing capability. The Processor may be a general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete Gate or transistor logic device, discrete hardware component.
The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The processor reads the information in the storage medium and completes the steps of the method in combination with the hardware.
The storage medium may be a memory, for example, which may be volatile memory or nonvolatile memory, or which may include both volatile and nonvolatile memory.
The nonvolatile Memory may be a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), or a flash Memory.
The volatile Memory may be a Random Access Memory (RAM) which serves as an external cache. By way of example and not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), SLDRAM (SLDRAM), and Direct Rambus RAM (DRRAM).
The storage media described in connection with the embodiments of the invention are intended to comprise, without being limited to, these and any other suitable types of memory.
Those skilled in the art will appreciate that the functionality described in the present invention may be implemented in a combination of hardware and software in one or more of the examples described above. When software is applied, the corresponding functionality may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer.
Further, simulation studies were performed on the above-described embodiments presented in the embodiments of the present invention at MATLAB/Simulink, where the inductance and the output side capacitance were 50 μ H and 600 μ F, respectively. Both steady state and dynamic performance of the output voltage regulator were evaluated, including output voltage set-point, input line voltage, and output voltage conditions during dynamic changes in load current, as shown in the results.
Simulation experiment of output voltage given value change under the above working condition, as shown in fig. 5A, the output voltage given value of the above embodiment of the present invention is changed from 12V to 36V, the input voltage is 24V, and the output terminal of the buck-boost converter is connected with a 5A constant current load. As a result, as shown in fig. 5a, when switching between buck and boost modes of operation, the output voltage undergoes a smooth transition without significant output voltage ripple; the result is a rapid transient in inductor current without large inrush values, as shown in fig. 5 b. In addition, no matter the output voltage given value is 12V or 24V, the output voltage can well track the given value in a steady state, the tracking error is less than 1%, the ripple performance is less than 0.1%, and the output capacitance required by design is reduced.
In the above working conditions, as shown in fig. 6a and 6b, the input voltage has a step change from 12V to 36V, the given value of the output voltage is kept at 24V, and the output side of the Buck-Boost converter is still connected with a 5A constant current load. As a result, as shown in fig. 6b and 6c, after the input voltage is changed, the output voltage is returned to 24V through a rapid regulation process, the response speed of the inductor current to the input voltage is fast, and there is no large inrush current. It can be seen that the system first operates in Boost mode and then smoothly transitions to Buck mode after passing through the Buck-Boost state. As a result, the output voltage regulation is good without being affected by input voltage transients or operating mode transitions.
Under the condition of rapid load change, the performance of the four-switch Buck-Boost converter is evaluated by adopting the embodiment provided by the invention. Under the working condition, the given value of the output voltage is 12V, the input voltage is 24V, and the converter works in a Buck mode. The load current changes from 2.5A to 5A at the fastest rate and then back to 2.5A. As a result, the output voltage remains stable and transitions smoothly under load step changes, as shown in fig. 7a and 7 b. Under the condition of load transient, the observed ratios of the overshoot amplitude and the undershoot amplitude of the output voltage to the stable value are within 2 percent. When the load current changes, the inductor current changes rapidly, and no large inrush current occurs.
In summary, the invention has the following advantages: the embodiment provided by the invention can realize smooth transition without an operation dead zone during mode conversion of the four-switch Buck-Boost converter, and realize good voltage regulation performance; the Buck-Boost converter can realize smooth transition between Buck and Boost modes of the four-switch Buck-Boost converter, and has the advantages of high response speed, high tracking precision and no surge current.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made on the basis of the technical solutions of the present invention should be included in the scope of the present invention.
Claims (10)
1. A model predictive control method of a Buck-Boost converter is characterized by comprising the following steps:
detecting the input voltage V of the Buck-Boost converter in the current control period kin(k) An output voltage Vo(k) And the inductor current IL(k)；
Using a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Respectively predicting the inductive current I of the next control period k +1 through a discrete time prediction modelL(k+1)；
Utilizing the inductor current I of the next control period k +1 corresponding to each switch state vectorL(k +1) and the maximum allowable inductor current value imaxComparing and updating current limiting weighting factor lambdai_limit；
Using a predetermined reference voltage VrefAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref；
Using the inductor current reference value iL_refThe inductor current I of the next control period k +1L(k +1), updated current limit weighting factor lambdai_limitCalculating and storing a value function value g corresponding to each switch state vector; and
selecting and outputting the minimum value function value gminThe switch state of the corresponding switch state vector is taken as the selected switch state SSoptAnd controlling each switch of the Buck-Boost converter in the next control period k + 1.
2. The method of claim 1, wherein the Buck-Boost converter comprises: first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4The first switch tube S1First end of and the second switch tube S2The first end of the first switch tube S is connected to form a first bridge arm1And the second switch tube S2Respectively connected to the positive and negative poles of a power supply, and a third switching tube S3First end of and the fourth switching tube S4The first ends of the first and second switching tubes S are connected to form a second bridge arm3And the fourth switching tube S4The second end of the second switch tube S is respectively connected to the positive end and the negative end of the load resistor2Second end of and the fourth switching tube S4The second ends of the first and second bridge arms are connected to form a third bridge arm, a fourth bridge arm is formed by the first and second bridge arms in a communication mode, an inductor is arranged on the fourth bridge arm, a power-side single-phase bridge arm point ph1 is formed by the fourth bridge arm and a first connecting point of the first bridge arm, and the first connecting point is located on the first switching tube S1And the second switch tube S2A second connection point of the fourth bridge arm and the second bridge arm forms an output-side single-phase bridge arm point ph2, and the second connection point is located at the third switching tube S3And the fourth switching tube S4And a power supply side capacitor and an output side capacitor are respectively connected in parallel on the power supply side and the output side of the Buck-Boost converter.
3. The method of claim 2, wherein: the algorithm formula of the discrete time prediction model is as follows:
wherein, TSIs the sampling time, R represents the load resistance of the Buck-Boost converter, RCExpressing the internal resistance of the output side capacitor, L expressing the inductance value of the inductor of the Buck-Boost converter, u1(t) represents the voltage of the single-phase bridge arm point ph1 on the power supply side of the Buck-Boost converter at the time t in the current control period k,
u2(t) represents the voltage of the Buck-Boost converter output side single-phase arm point ph2 at the time t in the current control period k,
dauxwhich represents the prediction coefficients of the video signal,
SS1、SS2、SS3、SS4respectively represent a first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Off denotes that the switch tube is open, on denotes that the switch tube is closed, i belongs to {1,2}, and t belongs to k.
4. Method according to claim 1, characterized in that the current limiting weighting factor λi_limitThe updating method comprises the following steps:
the inductor current I according to the next control period k +1L(k +1) and the maximum allowable inductor current value imaxCurrent limiting weighting factor lambda is updated according to comparison resultsi_limit；
When the inductor current I of the next control period k +1L(k +1) is less than the maximum allowable inductor current value imaxWhen, the current limit weightingFactor lambdai_limitUpdating to 0; and
when the inductor current I of the next control period k +1L(k +1) is greater than or equal to the maximum allowable inductor current value imaxWhile, the current limit weighting factor lambdai_limitUpdated to greater than 1000max (| i)L_ref-IL(k+1)|)。
5. The method of claim 1, wherein the cost function for computing the cost function value g is:
g＝|iL_ref-IL(k+1)|+λi_limit。
6. method according to claim 1, characterized in that said first switch state vector AS1On/off state of
Second switch state vector AS2On-off state
Third switch state vector AS3On-off state
Fourth switch state vector AS4On-off state
Respectively as follows:
wherein 0 represents that the switch tube is opened, and 1 represents that the switch tube is closed.
7. The method according to claim 1, characterized in that it comprises: sequentially utilizing the first switch state vector AS by cyclic assignment j1The second switch state vector AS2The third switch state vector AS3The fourth switch state vector AS4Predicting the inductor current I of the next control period k +1L(k +1), updating current limiting weighting factor lambdai_limitAnd calculating a value of the cost function g, wherein j sequentially takes 1,2, 3, 4 and 5, and when j takes 5, stopping the circulation process.
8. A model predictive control system for a Buck-Boost converter, the system comprising:
the detection module is used for detecting the input voltage V of the Buck-Boost converter in the current control period kin(k) An output voltage Vo(k) And the inductor current IL(k)；
An inner loop control module for utilizing a first switch state vector AS1A second switch state vector AS2Third switch state vector AS3A fourth switch state vector AS4Respectively predicting the inductive current I of the next control period k +1 through a discrete time prediction modelL(k + 1); utilizing the inductor current I of the next control period k +1 corresponding to each switch state vectorL(k +1) and the maximum allowable inductor current value imaxComparing and updating current limiting weighting factor lambdai_limit；
An outer loop control module for utilizing pre-predictionLet reference voltage VrefAnd detecting the obtained output voltage Vo(k) The error between the two values is used to calculate the inductance current reference value iL_ref；
A cost function calculation module for utilizing the inductor current reference value iL_refThe inductor current I of the next control period k +1L(k +1), updated current limit weighting factor lambdai_limitCalculating and storing a value function value g corresponding to each switch state vector; and
a switch state selecting and outputting module for selecting and outputting the minimum value function value gminThe switch state of the corresponding switch state vector is taken as the selected switch state SSoptAnd controlling each switch of the Buck-Boost converter in the next control period k + 1.
9. A model predictive control apparatus of a Buck-Boost converter, the apparatus comprising: a processor and a memory;
the memory is to store one or more program instructions;
the processor, configured to execute one or more program instructions to perform the method of any of claims 1-7.
10. A computer storage medium comprising one or more program instructions for performing the method of any one of claims 1-7.
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