CN112054695B - Isolated DC converter control method, device, equipment and storage medium - Google Patents

Isolated DC converter control method, device, equipment and storage medium Download PDF

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CN112054695B
CN112054695B CN202010974494.9A CN202010974494A CN112054695B CN 112054695 B CN112054695 B CN 112054695B CN 202010974494 A CN202010974494 A CN 202010974494A CN 112054695 B CN112054695 B CN 112054695B
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isolated
converter
phase shift
shift angle
fundamental component
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CN112054695A (en
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金莉
马明
梁晓兵
雷二涛
杜婉琳
王玲
唐挺
徐柏榆
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Electric Power Research Institute of Guangdong Power Grid Co Ltd
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Electric Power Research Institute of Guangdong Power Grid Co Ltd
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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
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33584—Bidirectional converters
    • 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
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The application discloses a control method, a device, equipment and a storage medium of an isolated DC converter, which calculate the transmission power, a first fundamental component and a second fundamental component of the isolated DC converter by utilizing the collected data, obtain a resonant inductance current peak value optimization model by combining a Lagrange multiplier calculation mode, solve the partial derivative of a phase shift angle in the resonant inductance current model by taking the transmission power as a constraint condition, thereby obtaining an optimal inner phase shift angle corresponding to the minimum resonant inductance current peak value so as to carry out drive control on the isolated DC converter according to the optimal inner phase shift angle, keep the current stress of the isolated DC converter to be minimum, reduce the system loss, improve the conversion efficiency, solve the problem that the isolated DC converter has large system loss due to the existing control method, the technical problem of low conversion efficiency.

Description

Isolated DC converter control method, device, equipment and storage medium
Technical Field
The present application relates to the field of power transformation technologies, and in particular, to a method, an apparatus, a device, and a storage medium for controlling an isolated bidirectional dc converter.
Background
With the rapid development of the direct current transmission technology, the direct current distribution network plays an increasingly important role in the fields of urban rail transit systems, ship power distribution systems and the like.
In the current direct current transmission system, an isolation type direct current converter is mostly adopted, namely, the direct current converter formed by adding an isolation transformer between two direct current systems can eliminate energy flow between the direct current systems and a non-fault direct current system, so that fault isolation of the two direct current systems is realized, and the isolation type direct current converter is widely used in the direct current transmission system.
The traditional control method is to give an inner phase shift angle parameter of the isolated DC converter based on the operation requirement, obtain an outer phase shift angle through closed-loop voltage control, and then control based on the obtained phase shift angle parameter to realize the stability of output voltage and power.
Disclosure of Invention
The application provides a control method, a control device, control equipment and a storage medium for an isolated direct current converter, which are used for solving the technical problems of high system loss and low conversion efficiency of the isolated direct current converter caused by the existing control method.
First, a first aspect of the present application provides an isolated dc converter control method, including:
obtaining a first fundamental component based on the transmission power of the isolated DC converter, wherein the first fundamental component is a fundamental component of a per unit value of the transmission power;
obtaining a second fundamental component based on the resonance inductance current and the transformation ratio of the isolated direct current converter, wherein the second fundamental component is a fundamental component of a per unit value of the peak value of the resonance inductance current;
based on the first fundamental wave component and the second fundamental wave component, a Lagrange multiplier calculation mode is combined to construct a resonant inductive current peak value optimization model, the transmission power is used as a constraint condition, partial derivative solving is carried out on a phase shift angle in the resonant inductive current peak value model, and a first internal phase shift angle and a second internal phase shift angle of the isolation type direct current converter are obtained;
and performing drive control on the isolated DC converter according to a first external phase shift angle, the first internal phase shift angle and the second internal phase shift angle, wherein the first external phase shift angle is obtained in a feedback control mode.
Preferably, the formula of the resonant inductor current peak value optimization model is specifically as follows:
L(α,β,φ,λ)＝ILr_max1 *(α,β,φ)-λ[P1 *(α,β,φ)-p0 *]；
wherein L (alpha, beta, phi, lambda) is a Lagrangian function, lambda is a Lagrangian coefficient, and P is a linear function1 *(α, β, φ) is the first fundamental component, ILr_max1 *(α, β, φ) is the second fundamental component, p0 *Is a per unit value of the transmission power.
Preferably, the calculation formula of the first fundamental component is specifically:
Figure BDA0002685296030000021
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, alpha is an inner phase shift angle of a primary side DC power transmission system, beta is an inner phase shift angle of a secondary side DC power transmission system, and phi is an outer phase shift angle of a voltage midpoint.
Preferably, the calculation formula of the second fundamental component is specifically:
Figure BDA0002685296030000022
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated type direct current converter, k is the transformation ratio of the isolated type direct current converter, alpha is the inner phase shift angle of the primary side direct current transmission system, beta is the inner phase shift angle of the secondary side direct current transmission system, and phi is the outer phase shift angle of the voltage midpoint.
Preferably, the configuration process of the first outward phase angle specifically includes:
and optimally adjusting an outward phase angle of the isolated type direct current converter in a PI (proportional integral) control mode based on a voltage difference value between a preset reference voltage and the output voltage of the isolated type direct current converter until the voltage difference value is not greater than a preset voltage difference threshold value, and obtaining a first outward phase angle.
Preferably, the calculation process of the transformation ratio includes:
the method comprises the steps of obtaining input voltage and output voltage of an isolated direct current converter, and calculating the transformation ratio of the isolated direct current converter according to the ratio of the input voltage to the output voltage and the turn ratio of a primary side and a secondary side of a transformer in the isolated direct current converter.
Preferably, the calculation process of the transmission power includes:
calculating to obtain the transmission power of the isolated type direct current converter according to the input voltage of the isolated type direct current converter and system parameters, wherein the system parameters specifically comprise: output current, resonant inductance, switching frequency.
A second aspect of the present application provides an isolated dc converter control apparatus, including:
a first fundamental component obtaining unit, configured to obtain a first fundamental component based on transmission power of the isolated dc converter, where the first fundamental component is a fundamental component of a per unit value of the transmission power;
a second fundamental component obtaining unit, configured to obtain a second fundamental component based on the resonant inductor current and the transformation ratio of the isolated dc converter, where the second fundamental component is a fundamental component of a per unit value of the peak value of the resonant inductor current;
the internal phase shift angle calculation unit is used for constructing a resonant inductive current peak value optimization model based on the first fundamental wave component and the second fundamental wave component and by combining a Lagrange multiplier calculation mode, and performing partial derivative solving on the phase shift angle in the resonant inductive current peak value model by taking the transmission power as a constraint condition to obtain a first internal phase shift angle and a second internal phase shift angle of the isolated DC converter;
and the drive control unit is used for carrying out drive control on the isolated DC converter according to a first outward shift phase angle, the first inward shift phase angle and the second inward shift phase angle, wherein the first outward shift phase angle is obtained in a feedback control mode.
A third aspect of the present application provides an isolated dc converter control apparatus, including: a memory and a processor;
the memory is used for storing program codes corresponding to the control method of the isolated direct current converter mentioned in the first aspect of the application;
the processor is configured to execute the program code.
A fourth aspect of the present application provides a storage medium having stored therein program code corresponding to the isolated dc converter control method of the first aspect of the present application.
According to the technical scheme, the embodiment of the application has the following advantages:
the application provides a control method of an isolated direct current converter, which comprises the following steps: obtaining a first fundamental component based on the transmission power of the isolated DC converter, wherein the first fundamental component is a fundamental component of a per unit value of the transmission power; obtaining a second fundamental component based on the resonance inductance current and the transformation ratio of the isolated direct current converter, wherein the second fundamental component is a fundamental component of a per unit value of the peak value of the resonance inductance current; based on the first fundamental wave component and the second fundamental wave component, a Lagrange multiplier calculation mode is combined to construct a resonant inductive current peak value optimization model, the transmission power is used as a constraint condition, partial derivative solving is carried out on a phase shift angle in the resonant inductive current peak value model, and a first internal phase shift angle and a second internal phase shift angle of the isolation type direct current converter are obtained; and performing drive control on the isolated DC converter according to a first external phase shift angle, the first internal phase shift angle and the second internal phase shift angle, wherein the first external phase shift angle is obtained in a feedback control mode.
According to the method, the first fundamental component and the second fundamental component of the isolated DC converter are calculated by utilizing the collected data, a resonant inductance current peak value optimization model is obtained by combining a Lagrange multiplier calculation mode, the transmission power is used as a constraint condition, and the partial derivative solution is carried out on the phase shift angle in the resonant inductance current peak value model, so that the corresponding optimal inner phase shift angle when the resonant inductance current peak value is minimum is obtained, the isolated DC converter is driven and controlled according to the optimal inner phase shift angle, the current stress of the isolated DC converter is kept minimum, the system loss is reduced, the conversion efficiency is improved, and the technical problems that the isolated DC converter has large system loss and low conversion efficiency due to the existing control method are solved.
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In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flowchart of a first embodiment of a control method for an isolated dc converter according to the present application;
fig. 2 is a schematic structural diagram of a first embodiment of an isolated dc converter control apparatus according to the present application;
FIG. 3 is a circuit schematic of a three-level DAB converter;
fig. 4 is a graph of the equivalent voltage current waveform of the three-level DAB converter as shown in fig. 3.
Detailed Description
The traditional control method is to give an inner phase shift angle parameter of the isolated DC converter based on the operation requirement, obtain an outer phase shift angle through closed-loop voltage control, and then control based on the obtained phase shift angle parameter to realize the stability of output voltage and power.
The embodiment of the application provides a control method, a control device, control equipment and a storage medium for an isolated direct current converter, which are used for solving the technical problems of large system loss and low conversion efficiency of the isolated direct current converter caused by the existing control method.
In order to make the objects, features and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the embodiments described below are only a part of the embodiments of the present application, and not all of the embodiments. 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 application.
Referring to fig. 1, a first embodiment of the present application provides a control method for an isolated dc converter, which is applied to the isolated dc converter, wherein bridge modules at two ends of the isolated dc converter are respectively connected to two dc power transmission systems, and the two bridge modules are connected through a transformer, and the control method includes:
step 101, obtaining a first fundamental component based on the transmission power of the isolated dc converter, where the first fundamental component is a fundamental component of a per unit value of the transmission power.
It should be noted that, according to the transmission power of the isolated dc converter that needs to be controlled, the transmission power is preprocessed to obtain a fundamental component of a per unit value of the transmission power, that is, a first fundamental component.
And 102, obtaining a second fundamental component based on the resonant inductive current and the transformation ratio of the isolated direct current converter, wherein the second fundamental component is a fundamental component corresponding to a per unit value of a peak value of the resonant inductive current.
It should be noted that, the resonant inductor current of the isolated dc converter, which is controlled as needed, is preprocessed according to the resonant inductor current and the transformation ratio, so as to obtain a fundamental component corresponding to a per unit value of the peak value of the resonant inductor current, that is, a second fundamental component.
It should be noted that, step 101 and step 102 in this embodiment may be performed in sequence or in parallel, and the transmission power, the resonant inductor current, and the transformation ratio in step 101 and step 102 in this embodiment may all be obtained by measurement, or calculated according to a corresponding calculation method based on measurable parameters in the isolated dc converter.
103, constructing a resonant inductor current peak value optimization model based on the first fundamental wave component and the second fundamental wave component and by combining a Lagrange multiplier calculation mode, and solving a partial derivative of a phase shift angle in the resonant inductor current peak value model by taking transmission power as a constraint condition to obtain a first internal phase shift angle and a second internal phase shift angle of the isolated DC converter.
It should be noted that, based on the first fundamental wave component and the second fundamental wave component obtained in the above steps 101 and 102, a lagrangian multiplier calculation mode is used, and a lagrangian multiplier calculation formula is used as a basis to construct a resonant inductor current peak optimization model, then a partial derivative solution is performed on a phase shift angle parameter included in the resonant inductor current peak model, and when the resonant inductor current peak reaches the minimum value after the solution, an optimal phase shift angle of the isolated dc converter, that is, a first phase shift angle and a second phase shift angle, is obtained.
And 104, performing drive control on the isolated type direct current converter according to the first externally-shifted phase angle, the first internally-shifted phase angle and the second internally-shifted phase angle, wherein the first externally-shifted phase angle is obtained in a feedback control mode.
And finally, based on the optimal inner phase shift angle obtained in the step 103, combining the outer phase shift angle obtained in a feedback control mode, controlling and outputting a driving signal of a switching device of the isolated direct current converter to be controlled, and finally realizing the optimal control of the isolated direct current converter, so that the aims of keeping the current stress of the isolated direct current converter to be minimum, reducing the system loss and improving the conversion efficiency are fulfilled.
According to the method, a first fundamental component and a second fundamental component of the isolated DC converter are calculated by utilizing data acquired in real time, a Lagrange multiplier calculation mode is combined to obtain a resonant inductance current peak value optimization model, the transmission power is taken as a constraint condition, and the partial derivative solution is carried out on the phase shift angle in the resonant inductance current peak value model, so that the optimal inner phase shift angle corresponding to the minimum resonant inductance current peak value is obtained, the isolated DC converter is driven and controlled according to the optimal inner phase shift angle, the current stress of the isolated DC converter is kept to be minimum, the system loss is reduced, the conversion efficiency is improved, and the technical problems that the isolated DC converter is large in system loss and low in conversion efficiency due to the existing control method are solved.
The above is a detailed description of a first embodiment of a method for controlling an isolated dc converter provided by the present application, and the following is a detailed description of a second embodiment of a method for controlling an isolated dc converter provided by the present application.
Referring to fig. 1, fig. 3 and fig. 4, based on the above first embodiment, a second embodiment of the present application provides a more specific isolated dc converter control method, including:
more specifically, the formula of the resonant inductor current peak optimization model is specifically as follows:
L(α,β,φ,λ)＝ILr_max1 *(α,β,φ)-λ[P1 *(α,β,φ)-p0 *]；
wherein L (alpha, beta, phi, lambda) is a Lagrangian function, lambda is a Lagrangian coefficient, and P is a linear function1 *(α, β, φ) is a first fundamental component, ILr_max1 *(α, β, φ) is the second fundamental component, p0 *Is a per unit value of transmission power.
More specifically, the calculation formula of the first fundamental component is specifically:
Figure BDA0002685296030000071
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, alpha is an inner phase shift angle of a primary side DC power transmission system, beta is an inner phase shift angle of a secondary side DC power transmission system, and phi is an outer phase shift angle of a voltage midpoint.
More specifically, the calculation formula of the second fundamental component is specifically:
Figure BDA0002685296030000072
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, k is the transformation ratio of the isolated DC converter, alpha is the internal phase shift angle of the primary side DC transmission system, beta is the internal phase shift angle of the secondary side DC transmission system, and phi is the external phase shift angle of the voltage midpoint.
More specifically, the configuration process of the first outward phase shift angle specifically includes:
and optimally adjusting the outward phase angle of the isolated type direct current converter in a PI (proportional integral) control mode based on a voltage difference value between a preset reference voltage and the output voltage of the isolated type direct current converter until the voltage difference value is not greater than a preset voltage difference threshold value, and obtaining a first outward phase angle.
It should be noted that the present embodiment is explained by taking a three-level DAB converter (Dual Active Bridge, Dual Active full Bridge dc converter) as a specific example of the isolated dc converter, where the structure of the three-level DAB converter can refer to fig. 3. It is composed of two three-level full-bridge units with clamping diode and flying capacitor via resonant inductor LrDC blocking capacitor Cb1/Cb2And a high-frequency transformer T. Wherein, the switch tube S11-S18Clamping diode Dc1-Dc4Flying capacitor Css1-Css2And a voltage-sharing capacitor C11-C12A three-level full bridge forming the primary side of the transformer; switch tube S21-S28Clamping diode Dc5-Dc8Flying capacitor Css3-Css4And a voltage-sharing capacitor C21-C22Forming a three-level full bridge on the secondary side of the transformer. The turn ratio of the primary side to the secondary side of the high-frequency transformer is N:1, V1And V2Respectively an input voltage and an output voltage. A. B is the midpoint of the primary side bridge arm, C, D is the midpoint of the secondary side bridge arm, O1、O2Is the midpoint of the input and output voltage-dividing capacitors. The following are the reference parameters of each device in fig. 3, as shown in table 1:
TABLE 1 Circuit device parameter table
Figure BDA0002685296030000081
Universal voltage current waveform incorporating a three-level DAB converter, where vABAnd vCDBridge arm voltages, i, of primary and secondary sides of the transformer, respectivelyLrIs the current flowing through the resonant inductor. Let alpha be the internal phase shift angle of primary three-level full bridge, beta be the internal phase shift angle of secondary three-level full bridge, phi' be the phase shift angle between the corresponding switch tubes of primary and secondary, and also define vABAnd vCDThe phase shift angle between the voltage midpoints, i.e., the out-shift angle, is phi.
Firstly, the transformation ratio k of the three-level DAB converter can be calculated according to the input voltage V1, the output voltage V2 sampled in real time and the original secondary side turn ratio N of the transformer as follows:
Figure BDA0002685296030000082
then, the transmission power p of the three-level DAB converter is determined0. Under the steady state working condition, the input voltage V of the converter can be obtained by sampling in real time1An output voltage V2Output current I2In combination with a known system parameter resonant inductance LrSwitching frequency fsThus, the following can be calculated:
Figure BDA0002685296030000083
the transformation ratio k and the transmission power p are calculated according to the steps0Solving the optimal V corresponding to the minimum reflux power of the converter1Side phase shift angle alpha and optimum V2The phase angle β is shifted inward. Controlling three-level DAB in conjunction with the circuit schematic of FIG. 3 and the waveform diagram of FIG. 4The per unit value of the transmission power of the converter is expressed as:
Figure BDA0002685296030000084
where P is the transmission power in one cycle, PbaseIs a preset power reference value, N is the turn ratio of the transformer, alpha is the internal phase shift angle of the primary side three-level full bridge, beta is the internal phase shift angle of the secondary side three-level full bridge, and phi is vABAnd vCDThe phase shift angles between the voltage midpoints, m and n, represent the order of the voltage and current high frequency harmonic expressions, respectively, when solving for power.
From the voltage-current waveform diagram shown in fig. 4, the expression i of the instantaneous value of the current flowing through the resonant inductor can be obtainedLr(t)：
Figure BDA0002685296030000091
Therefore, as can be seen from equation (4), the peak value of the resonant inductor current is expressed as,
Figure BDA0002685296030000092
in the formulas (4) and (5), n is the order of harmonic when the inductor current is superimposed with the harmonic components of each order, ω is the angular frequency, and L isrThe method is a resonance inductor, A and B are intermediate quantities for calculation, and specifically comprises the following steps:
Figure BDA0002685296030000093
wherein, V1Bit input side voltage, V2For the output side voltage, alpha is the internal phase shift angle of the primary side three-level full bridge, beta is the internal phase shift angle of the secondary side three-level full bridge, and phi is vABAnd vCDPhase shift angle between the voltage midpoints.
Performing per unit processing on the peak value of the resonant inductive current to obtain a per unit value of the peak value of the resonant inductive current as shown in the following formula:
Figure BDA0002685296030000094
in the formula ILr_max *Is the per unit value of the peak value of the resonant inductor current, ILr_maxFor resonant inductor current peak, IbaseThe harmonic suppression circuit is a preset current reference value and can be obtained by dividing reference power by reference voltage, N is the order of each harmonic in a harmonic expression of a resonant inductor current, N is the turn ratio of the primary side and the secondary side of the transformer, alpha is the internal phase shift angle of the primary side three-level full bridge, beta is the internal phase shift angle of the secondary side three-level full bridge, and phi is vABAnd vCDAnd the phase shift angle k between the voltage midpoints is the transformation ratio obtained in the step.
By combining the expressions of transmission power and resonant inductor current peak values shown in expressions 3 and 7, the fundamental wave components are their respective main components, and the variation tendency of the fundamental wave components is consistent with that of the total amount. Therefore, the optimization control method of the present embodiment is an optimization method based on the fundamental component. The method comprises the following specific steps:
(1) according to the formula 3 and the formula 7, the fundamental component of the transmission power and the peak per unit value of the resonance inductance current is obtained, specifically:
Figure BDA0002685296030000101
in the formula, P1 *(α, β, φ) is the fundamental component of the per unit value of transmission power, ILr_max1 *(alpha, beta, phi) is the fundamental component of per unit value of the peak value of the resonant inductor current, alpha is the internal phase shift angle of the primary side three-level full bridge, beta is the internal phase shift angle of the secondary side three-level full bridge, and phi is vABAnd vCDAnd (3) the phase shift angle between the voltage midpoints, N is the turns ratio of the transformer, and k is the transformation ratio calculated in the step.
Let a given per unit value of transmission power be p0 *Constructing a relative loop according to the Lagrangian multiplier methodThe lagrangian equation for the power optimization of the stream,
L(α,β,φ,λ)＝ILr_max1 *(α,β,φ)-λ[P1 *(α,β,φ)-p0 *] (9)
wherein L (α, β, φ, λ) is a Lagrangian function and λ is a Lagrangian coefficient.
In order to solve the optimal solution of the reflux power, the partial derivatives are calculated for the three phase shifting angles in the formula 9, and each partial derivative is zero, specifically:
Figure BDA0002685296030000102
in the formula, alpha is the internal phase shift angle of the primary side three-level full bridge, beta is the internal phase shift angle of the secondary side three-level full bridge, and phi is vABAnd vCDPhase shift angle between the voltage midpoints. For the stable operation state of a specific converter, the lagrangian function has the following constraint condition:
Figure BDA0002685296030000103
the constraint conditions specify the magnitude of the transmission power of the converter, i.e. the transmission power obtained by the real-time sampling solution in the above steps. Then, combining the formula (10) and the formula (11), obtaining an optimal phase shift angle corresponding to the minimum effective value of the resonant inductor current, wherein the first phase shift angle and the second phase shift angle are, specifically,
Figure BDA0002685296030000111
through the operation, the optimal inner shift phase angle corresponding to the minimum peak value of the resonant inductor current can be obtained, the isolated DC converter is subjected to drive control according to the first inner shift phase angle, the second inner shift phase angle and the first outer shift phase angle, and finally, the optimal control of the three-level DAB converter is realized.
Wherein the first outwardly shifted phase angle doesThe process can be referred to the following steps: the phase shift angle phi' between the corresponding switch tubes on the primary side and the secondary side is adjusted by a PI controller to output a voltage V2And a command voltage VrefWhen the error value is not zero, the system has a steady-state error, the error is sent to an integral controller, the error is subjected to time integration through an integral link, the longer the error exists, the larger the integral controller action is, and the integral action is increased along with the increase of time. Even if the error is small, the output change of the PI controller is increased along with the increase of time, so that the steady-state error is further reduced until the steady-state error is zero, and finally, the steady-state output voltage has no static error.
According to the technical scheme, the embodiment of the application has the following advantages:
1. according to the resonance inductance current peak value minimum optimization control method based on fundamental wave optimization, the voltage and the current are sampled in real time to calculate the optimal phase shift angle, so that the inductance current is reduced, the system loss is reduced, and the efficiency is improved. Compared with the conventional current stress optimization control algorithm, the method does not need complex modal analysis and inter-partition range judgment, and reduces the calculation amount and the calculation complexity of the control chip.
2. The current stress minimum control method of the bidirectional direct current electric energy converter based on the universal phase shift control, provided by the embodiment, can overcome the defects of large current stress, low efficiency and the like caused by mismatching of input and output voltages during phase shift control of a three-level DAB converter, can effectively reduce the current stress of the converter in a full power range and a full voltage transformation ratio range, and improves the efficiency and performance of the whole converter.
3. The control method for reducing the current stress of the bidirectional direct current electric energy conversion device provided by the embodiment has a more obvious optimization effect under the working condition that the converter is lightly loaded or the voltage is more unmatched. And under some specific working conditions, the control method provided by the embodiment is adopted, so that the reflux power of the system can be reduced while the current stress of the system is reduced, and the double optimization effect is achieved for improving the efficiency of the system.
The above is a detailed description of the second embodiment of the isolated dc converter control method provided in the present application, and the following is a detailed description of the first embodiment of the isolated dc converter control device provided in the present application.
Referring to fig. 2, a third embodiment of the present application provides an isolated dc converter control apparatus, including:
a first fundamental component obtaining unit 201, configured to obtain a first fundamental component based on the transmission power of the isolated dc converter, where the first fundamental component is a fundamental component of a per unit value of the transmission power;
a second fundamental component obtaining unit 202, configured to obtain a second fundamental component based on the resonant inductor current and the transformation ratio of the isolated dc converter, where the second fundamental component is a fundamental component of a per unit value of a peak value of the resonant inductor current;
the inner phase shift angle calculation unit 203 is configured to construct a resonant inductor current peak optimization model based on the first fundamental component and the second fundamental component in combination with a lagrangian multiplier calculation mode, and perform partial derivative solution on a phase shift angle in the resonant inductor current peak optimization model by using transmission power as a constraint condition to obtain a first inner phase shift angle and a second inner phase shift angle of the isolated dc converter;
the driving control unit 204 is configured to perform driving control on the isolated dc converter according to a first externally shifted phase angle, a first internally shifted phase angle, and a second internally shifted phase angle, where the first externally shifted phase angle is obtained through a feedback control manner.
More specifically, the formula of the resonant inductor current peak optimization model is specifically as follows:
L(α,β,φ,λ)＝ILr_max1 *(α,β,φ)-λ[P1 *(α,β,φ)-p0 *]；
wherein L (alpha, beta, phi, lambda) is a Lagrangian function, lambda is a Lagrangian coefficient, and P is a linear function1 *(α, β, φ) isFirst fundamental component, ILr_max1 *(α, β, φ) is the second fundamental component, p0 *Is a per unit value of transmission power.
More specifically, the calculation formula of the first fundamental component is specifically:
Figure BDA0002685296030000121
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, alpha is an inner phase shift angle of a primary side DC power transmission system, beta is an inner phase shift angle of a secondary side DC power transmission system, and phi is an outer phase shift angle of a voltage midpoint.
More specifically, the calculation formula of the second fundamental component is specifically:
Figure BDA0002685296030000122
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, k is the transformation ratio of the isolated DC converter, alpha is the internal phase shift angle of the primary side DC transmission system, beta is the internal phase shift angle of the secondary side DC transmission system, and phi is the external phase shift angle of the voltage midpoint.
More specifically, the configuration process of the first outward phase shift angle specifically includes:
and optimally adjusting the outward phase angle of the isolated type direct current converter in a PI (proportional integral) control mode based on a voltage difference value between a preset reference voltage and the output voltage of the isolated type direct current converter until the voltage difference value is not greater than a preset voltage difference threshold value, and obtaining a first outward phase angle.
More specifically, the calculation process of the transformation ratio includes:
the method comprises the steps of obtaining input voltage and output voltage of an isolated direct current converter, and calculating the transformation ratio of the isolated direct current converter according to the ratio of the input voltage to the output voltage and the turn ratio of the primary side and the secondary side of a transformer in the isolated direct current converter.
More specifically, the calculation process of the transmission power includes:
calculating to obtain the transmission power of the isolated DC converter according to the input voltage of the isolated DC converter and system parameters, wherein the system parameters specifically comprise: output current, resonant inductance, switching frequency.
The above is a detailed description of a first embodiment of an isolated dc converter control apparatus provided in the present application, and the following is a detailed description of an embodiment of an isolated dc converter control apparatus and a corresponding storage medium provided in the present application.
A fourth embodiment of the present application provides an isolated dc converter control apparatus, including: a memory and a processor;
the memory is used for storing program codes corresponding to the control method of the isolated direct current converter mentioned in the first embodiment or the second embodiment of the application;
the processor is used for executing the program codes.
A fifth embodiment of the present application provides a storage medium having stored therein program codes corresponding to the isolated dc converter control method according to the first or second embodiment of the present application.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (10)

1. An isolated DC converter control method, comprising:
obtaining a first fundamental component based on the transmission power of the isolated DC converter, wherein the first fundamental component is a fundamental component of a per unit value of the transmission power;
obtaining a second fundamental component based on the resonance inductance current and the transformation ratio of the isolated direct current converter, wherein the second fundamental component is a fundamental component of a per unit value of the peak value of the resonance inductance current;
based on the first fundamental wave component and the second fundamental wave component, a Lagrange multiplier calculation mode is combined to construct a resonant inductive current peak value optimization model, the transmission power is used as a constraint condition, partial derivative solving is carried out on a phase shift angle in the resonant inductive current peak value model, and a first internal phase shift angle and a second internal phase shift angle of the isolation type direct current converter are obtained;
and performing drive control on the isolated DC converter according to a first external phase shift angle, the first internal phase shift angle and the second internal phase shift angle, wherein the first external phase shift angle is obtained in a closed-loop feedback control mode.
2. The isolated direct-current converter control method according to claim 1, wherein a formula of the resonant inductor current peak value optimization model is specifically as follows:
L(α,β,φ,λ)＝ILr_max1 *(α,β,φ)-λ[P1 *(α,β,φ)-p0 *]；
wherein L (alpha, beta, phi, lambda) is a Lagrangian function, lambda is a Lagrangian coefficient, and P is a linear function1 *(α, β, φ) is the first fundamental component, ILr_max1 *(α, β, φ) is the second fundamental component, p0 *Is a per unit value of the transmission power.
3. The isolated dc converter control method according to claim 1, wherein the calculation formula of the first fundamental component is specifically:
Figure FDA0003227181210000011
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated DC converter, alpha is an inner phase shift angle of a primary side DC power transmission system, beta is an inner phase shift angle of a secondary side DC power transmission system, and phi is an outer phase shift angle of a voltage midpoint.
4. The isolated dc converter control method according to claim 1, wherein the calculation formula of the second fundamental component is specifically:
Figure FDA0003227181210000012
in the formula, N is the turn ratio of the primary side and the secondary side of a transformer in the isolated type direct current converter, k is the transformation ratio of the isolated type direct current converter, alpha is the inner phase shift angle of the primary side direct current transmission system, beta is the inner phase shift angle of the secondary side direct current transmission system, and phi is the outer phase shift angle of the voltage midpoint.
5. The method according to claim 1, wherein the configuration process of the first externally shifted phase angle specifically includes:
and optimally adjusting an outward phase angle of the isolated type direct current converter in a PI (proportional integral) control mode based on a voltage difference value between a preset reference voltage and the output voltage of the isolated type direct current converter until the voltage difference value is not greater than a preset voltage difference threshold value, and obtaining a first outward phase angle.
6. The isolated dc converter control method according to claim 1, wherein the step of calculating the transformation ratio includes:
the method comprises the steps of obtaining input voltage and output voltage of an isolated direct current converter, and calculating the transformation ratio of the isolated direct current converter according to the ratio of the input voltage to the output voltage and the turn ratio of a primary side and a secondary side of a transformer in the isolated direct current converter.
7. The isolated dc converter control method according to claim 1, wherein the calculation of the transmission power includes:
calculating to obtain the transmission power of the isolated type direct current converter according to the input voltage of the isolated type direct current converter and system parameters, wherein the system parameters specifically comprise: output current, resonance inductance, switching frequency and the primary and secondary turns ratio of the transformer.
8. An isolated dc converter control apparatus, comprising:
a first fundamental component obtaining unit, configured to obtain a first fundamental component based on transmission power of the isolated dc converter, where the first fundamental component is a fundamental component of a per unit value of the transmission power;
a second fundamental component obtaining unit, configured to obtain a second fundamental component based on the resonant inductor current and the transformation ratio of the isolated dc converter, where the second fundamental component is a fundamental component of a per unit value of the peak value of the resonant inductor current;
the internal phase shift angle calculation unit is used for constructing a resonant inductive current peak value optimization model based on the first fundamental wave component and the second fundamental wave component and by combining a Lagrange multiplier calculation mode, and performing partial derivative solving on the phase shift angle in the resonant inductive current peak value model by taking the transmission power as a constraint condition to obtain a first internal phase shift angle and a second internal phase shift angle of the isolated DC converter;
and the drive control unit is used for carrying out drive control on the isolated DC converter according to a first outward shift phase angle, the first inward shift phase angle and the second inward shift phase angle, wherein the first outward shift phase angle is obtained in a closed-loop feedback control mode.
9. An isolated dc converter control apparatus, comprising: a memory and a processor;
the memory is used for storing program codes corresponding to the control method of the isolated DC converter of any one of claims 1 to 7;
the processor is configured to execute the program code.
10. A storage medium having stored therein a program code corresponding to the isolated dc converter control method according to any one of claims 1 to 7.
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