CN114970368B - Efficiency optimization method and device for double active bridge, electronic equipment and storage medium - Google Patents
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Abstract
The invention discloses an efficiency optimization method and device of a double active bridge, electronic equipment and a storage medium, and belongs to the technical field of power electronics, wherein the method comprises the following steps: establishing a fourier form-based switching function which is a function of the total number of harmonics and the phase shift angle; establishing an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model as objective functions by using a switching function based on a Fourier form; optimizing the objective function to obtain an optimal value of the total number of the harmonic waves and an optimal value of the phase shift angle, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum; the minimum inductor current and the minimum capacitor current are obtained. According to the invention, the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are built by a method based on harmonic modeling, so that the model is easier to solve, the calculated amount is small, and the implementation is easy.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to an efficiency optimization method and device of a double active bridge, electronic equipment and a storage medium.
Background
In order to improve the power efficiency of the double-active bridge type direct current converter, the related technology focuses on researching various power efficiency optimization strategies. Traditional efficiency optimization methods based on power loss models are to achieve optimal efficiency control by building accurate power loss models. However, this optimization method has a problem of complex computation, especially under complex working conditions, such as a face of varying load conditions and voltage conversion ratio conditions, increasing the difficulty of achieving optimal efficiency.
Disclosure of Invention
In view of the above, the embodiments of the present invention provide a method, an apparatus, an electronic device, and a storage medium for optimizing efficiency of a dual active bridge, so as to solve the problems of complex calculation and high implementation difficulty of the existing dual active bridge efficiency optimization method.
According to a first aspect, an embodiment of the present invention provides a method for optimizing efficiency of a dual active bridge, the method including:
establishing a fourier form-based switching function that is a function of the total number of harmonics and the phase shift angle;
establishing an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model as objective functions by using the switching function based on the Fourier form;
optimizing the objective function based on preset constraint conditions to obtain an optimal value of the total number of the harmonic waves and an optimal value of the phase shift angle, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
and acquiring the minimum inductive current and the minimum capacitive current.
Optionally, the constraint includes at least one of: the output power is constant, the calculation time does not exceed the maximum allowable value and the total number of harmonics is an integer.
Optionally, in the case that the constraint condition includes that the output power is constant, the method further includes:
establishing a relation function between a switching state and each output voltage;
and establishing a function of output power in a harmonic form by using the Fourier form-based switching function and the relation function.
Optionally, the creating an inductor current dynamic time domain harmonic model and a capacitor current dynamic time domain harmonic model by using the fourier-form-based switching function includes:
establishing a dynamic time domain expression of the double-active bridge by using the switching function expression based on the Fourier form;
and deducing a time domain expression of the inductor current and a time domain expression of the capacitor current by using the dynamic time domain expression of the double active bridge, wherein the time domain expression of the inductor current is used as the inductor current dynamic time domain harmonic model, and the time domain expression of the capacitor current is used as the capacitor current dynamic time domain harmonic model.
Optionally, the deriving the time domain expression of the inductor current and the time domain expression of the capacitor current by using the dynamic time domain expression of the double active bridge includes:
converting the dynamic time domain expression of the double active bridge into a phase domain expression of the double active bridge;
deriving a phase domain expression of the inductor current based on the phase domain expression of the double active bridge;
converting the phase domain expression of the inductor current into a time domain expression of the inductor current;
deriving a time domain expression of the capacitive current based on the time domain expression of the inductive current.
Optionally, the creating a dynamic time domain expression of the dual active bridge by using the fourier-form-based switching function expression includes:
establishing a relation function between a switching state and each output voltage;
and establishing a dynamic time domain expression of the double-active bridge by using the relation function and the switching function expression based on the Fourier form.
Optionally, the optimizing the objective function based on a preset constraint condition to obtain an optimal value of the total number of harmonics and an optimal value of the phase shift angle includes:
s201: randomly generating an initial population with the scale of N as a parent population;
s202: after non-dominant sorting is carried out on the parent population, a first generation offspring population is obtained through selection, crossing and mutation operations of a genetic algorithm; n is a positive integer;
s203: starting from the second generation, merging the parent population and the offspring population to obtain a sequencing population with the scale of 2N, carrying out rapid non-dominant sequencing, simultaneously carrying out crowding calculation on individuals in each non-dominant layer, and selecting the individuals to form a new parent population according to the non-dominant relationship and the crowding of the individuals;
s204: repeating steps S202 and S203 for the new parent population until the maximum number of iterations is met, stopping calculation, and obtaining the optimal value of the phase shift angle and the total number of harmonics.
According to a second aspect, an embodiment of the present invention provides an efficiency optimization apparatus for a dual active bridge, including:
a switching function establishing module for establishing a fourier form-based switching function, which is a function of the total number of harmonics and the phase shift angle;
the harmonic model building module is used for building an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model by using the switching function based on the Fourier form as an objective function;
the optimization module is used for optimizing the objective function based on preset constraint conditions to obtain an optimal value of the total number of the harmonic waves and an optimal value of the phase shift angle, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
and the acquisition module is used for acquiring the minimum inductive current and the minimum capacitive current.
According to a third aspect, an embodiment of the present invention provides an electronic device, including:
the system comprises a memory and a processor, wherein the memory and the processor are in communication connection, and the memory is used for storing a computer program which is executed by the processor to realize the efficiency optimization method of any double active bridge in the first aspect.
According to a fourth aspect, an embodiment of the present invention provides a computer readable storage medium, where the computer readable storage medium is configured to store a computer program, where the computer program when executed by a processor implements the method for optimizing efficiency of any one of the dual active bridges according to the first aspect.
According to the efficiency optimization method, the device, the electronic equipment and the storage medium of the double-active-bridge, which are provided by the embodiment of the invention, the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are established based on the harmonic modeling method, and the inductance current and the capacitance current are controlled to be minimized through the optimization algorithm, so that the power loss such as the switching tube loss, the transformer loss, the capacitance loss and the like can be reduced, and the efficiency of the double-active-bridge converter is improved. In addition, an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model are built based on a harmonic modeling method, so that the model is easier to solve, and the implementation is easier.
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The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and should not be construed as limiting the invention in any way, in which:
fig. 1 is a schematic flow chart of a method for optimizing efficiency of a dual active bridge according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a dual active bridge model;
FIG. 3 is a schematic diagram of a dual active bridge ideal waveform;
fig. 4 is a schematic structural diagram of an efficiency optimization device for a dual active bridge according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. In the following description of the embodiments, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Referring to fig. 1, an embodiment of the present invention provides a method for optimizing efficiency of a dual active bridge, where the method includes:
s101: establishing a fourier form-based switching function that is a function of the total number of harmonics K and the phase shift angle θ;
s102: establishing an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model as objective functions by using the switching function based on the Fourier form;
s103: optimizing the objective function based on a preset constraint condition to obtain an optimal value of the total number K of the harmonic waves and an optimal value of the phase shift angle theta, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
s104: and acquiring the minimum inductive current and the minimum capacitive current.
In the embodiment of the invention, the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are established based on the harmonic modeling method, and the inductance current and the capacitance current are controlled to be minimized through the optimization algorithm, so that the power loss such as the loss of a switching tube, the loss of a transformer, the loss of a capacitance and the like can be reduced, and the efficiency of the double-active-bridge converter is improved. In addition, an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model are built based on a harmonic modeling method, so that the model is easier to solve, and the implementation is easier.
In some specific embodiments, the creating the inductor current dynamic time domain harmonic model and the capacitor current dynamic time domain harmonic model using the fourier-based switching function includes:
establishing a dynamic time domain expression of the double-active bridge by using the switching function expression based on the Fourier form;
and deducing a time domain expression of the inductor current and a time domain expression of the capacitor current by using the dynamic time domain expression of the double active bridge, wherein the time domain expression of the inductor current is used as the inductor current dynamic time domain harmonic model, and the time domain expression of the capacitor current is used as the capacitor current dynamic time domain harmonic model.
In some optional embodiments, the deriving the time domain representation of the inductor current and the time domain representation of the capacitor current using a dynamic time domain representation of the dual active bridge includes:
converting the dynamic time domain expression of the double active bridge into a phase domain expression of the double active bridge;
deriving a phase domain expression of the inductor current based on the phase domain expression of the double active bridge;
converting the phase domain expression of the inductor current into a time domain expression of the inductor current;
deriving a time domain expression of the capacitive current based on the time domain expression of the inductive current.
The double active bridge model and the ideal waveform are shown in fig. 2 and 3, the double active bridge comprises 8 switching tubes S1-S8, wherein the switching tubes S1-S4 form a full bridge, the switching tubes S5-S8 form another full bridge, and the input voltage of the former full bridge is V in Output voltage is V T1 The input voltage of the other full bridge is V T2 Output voltage is V out The double active bridge model also comprises a transformer between two full bridges, an inductance L, a parasitic resistance R and an output capacitor C which are connected in series with the output end of the previous full bridge, wherein the turns ratio of the transformer is thatn:1. according to Fourier theory, any periodic signal can be represented by an infinite series composed of a sine function and a cosine function, and the function f (x) is assumed to be expandable to a uniformly convergent triangular series over the whole interval, as shown in formula (1), wherein the coefficient a 0 、a k And b k Respectively is
Therefore, the fourier-form-based switching function expression can be deduced as the expression (2), wherein the selection of the total number of harmonics K determines the accuracy of the double-active-bridge time-domain state space model, i.e., determines the accuracy of the inductor current dynamic time-domain harmonic model and the capacitor current dynamic time-domain harmonic model, and when the K value is larger, the fitting degree is higher, but the calculation amount is larger.
Wherein, the liquid crystal display device comprises a liquid crystal display device,
f s is the switching frequency of the switching tubes in the double active bridge.
Firstly, since the state variables in the double active bridge time domain model are driven by the binary value switch function, the dynamic model contains both discrete and continuous time functions, so that the dynamic equation is difficult to resolve. According to the embodiment of the invention, the double-active-bridge time domain state space model is built based on the harmonic modeling method, and then the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are deduced based on the double-active-bridge time domain state space model, so that the model is easier to solve and is easier to realize. In addition, by constructing the harmonic model, the influence of higher harmonics in the switching function on the output of the multilevel converter can be taken into account.
Secondly, in general, the double active bridge dc converter mainly includes 3 power losses, namely, a switching tube loss, a magnetic element loss, and a capacitance loss. The switching tube loss can be divided into switching loss, conduction loss, and gate driving loss. Magnetic element losses are concentrated in transformers and series inductors, including copper losses and iron losses. The conduction loss in the switching tube loss is proportional to the root mean square value of the current flowing in the switching tube in the conduction time, the capacitance loss is proportional to the root mean square value of the capacitance current, so that a double-active-bridge time domain state space model is established based on a harmonic modeling method, the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are deduced based on the double-active-bridge time domain state space model, and the inductance current and the capacitance current are controlled to be minimized through an optimization algorithm, so that the power loss such as the switching tube loss, the transformer loss, the capacitance loss and the like can be reduced, and the efficiency of the double-active-bridge converter is improved.
In some optional embodiments, the creating the dynamic time domain expression of the dual active bridge using the fourier-form-based switching function expression includes:
establishing a relation function between a switching state and each output voltage;
and establishing a dynamic time domain expression of the double-active bridge by using the relation function and the switching function expression based on the Fourier form.
For example, using the fourier-based switching function, the specific process of creating the inductor current dynamic time domain harmonic model and the capacitor current dynamic time domain harmonic model may be:
establishing a relation function between the switching state and each output voltage as shown in formulas (3) and (4):
V T1 (t)＝2V DC [S 1 (t)-S 3 (t)]＝V in [S 1 (t)-S 3 (t)] (3)
V T2 (t)＝2V DC [S 5 (t)-S 7 (t)]＝V out [S 5 (t)-S 7 (t)] (4)
the output voltages corresponding to the switching states of the switches are shown in the following table:
for the double active bridge model shown in fig. 2, assuming no loss, the double active bridge inductance voltage expression is equation (5) and the inductance current expression is equation (6) regardless of the transformer parasitic capacitance:
v L (t)＝v T1 (t)-nv T2 (t) (5)
and (3) establishing a double-active-bridge dynamic time domain expression by using the relation function shown in the formulas (3) and (4) and the Fourier form-based switching function shown in the formula (2), wherein the expression is shown in the formula (7):
wherein R is parasitic resistance of the double active bridge model.
After the double active bridge dynamic time domain expression shown in the formula (7) is converted into a phase domain expression, a phase domain expression of the inductive current can be deduced, and then the phase domain expression of the inductive current is converted into a time domain expression of the inductive current, as shown in the formula (8):
wherein, the liquid crystal display device comprises a liquid crystal display device,
the capacitive current time domain expression can be deduced from the inductive current time domain expression shown in the above formula (8), as shown in the formula (9):
wherein i is out (t) is the output current of the double active bridge model, i Load And (t) is the load current.
In some embodiments, the constraints include at least one of: the output power is constant, the calculation time does not exceed the maximum allowable value and the total number K of harmonics is an integer.
In some specific embodiments, the objective function may be represented by the following formula (10):
wherein P is ref T is a constant value of output power cal To calculate the time, t max To calculate the maximum allowable value of time.
In some specific embodiments, where the constraint includes that the output power is constant, the method further comprises:
establishing a relation function between a switching state and each output voltage;
and establishing a function of output power in a harmonic form by using the Fourier form-based switching function and the relation function.
Referring to fig. 3 and equation (6), at t according to the inductor current 0 To t 1 And t 1 To t 2 The expression of (2) and the expression of average transmission power in one period obtained by integrating the instantaneous transmission power expression of the double active bridge can deduce that the transmission power is in-pi<θ<The expression of pi is shown in formula (11):
from the relation function of the switching states and the respective output voltages shown in the above formulas (3) and (4) and the fourier-form-based switching function shown in the above formula (2), a function of the output power in the harmonic form based on the phase shift angle θ and the total number of harmonics K is obtained as shown in formula 12:
according to the embodiment of the invention, the inductance current and the capacitance current are selected as optimization indexes, an objective function taking the inductance current and the capacitance current as optimization objects is established, the constraint condition is that the output power is constant, the calculation time does not exceed the maximum allowable value, and the total harmonic number K is an integer.
In some specific embodiments, the optimizing the objective function based on a preset constraint condition to obtain the optimal value of the total number K of harmonics and the optimal value of the phase shift angle θ includes:
s201: randomly generating an initial population with the scale of N as a parent population;
s202: after non-dominant sorting is carried out on the parent population, a first generation offspring population is obtained through selection, crossing and mutation operations of a genetic algorithm; n is a positive integer;
s203: starting from the second generation, merging the parent population and the offspring population to obtain a sequencing population with the scale of 2N, carrying out rapid non-dominant sequencing, simultaneously carrying out crowding calculation on individuals in each non-dominant layer, and selecting the individuals to form a new parent population according to the non-dominant relationship and the crowding of the individuals;
s204: repeating steps S202 and S203 for the new parent population until the maximum number of iterations is met, stopping the calculation, and obtaining the optimal value of the phase shift angle theta and the total number of harmonics K.
Wherein, select: the selection operator is applied to the population. The selection operation either directly inherits the optimized individual to the next generation or generates new individuals through pairwise crossover to inherit to the next generation. Crossing: the crossover operator is applied to the population. Variation: the mutation operator is applied to the population. Variation is the variation of gene values at certain loci of individual strings in a population.
Regarding the fast non-dominant ordering, the specific procedure is:
(203-11) calculating a dominance count n for each individual in the pooled population g (i.e. the number of solutions that all dominate the solution g) and the set S of all solutions that are dominated by the solution g g . Specifying that all solutions at the first leading edge have a dominant count of 0, for each solution g whose dominant count is 0, then the set of solutions that are dominant to it S g The dominant count of all solutions in (1) is decremented by 1;
(203-12) after the above steps, if the dominant count of the solutions dominant by the solution g becomes 0, separating the solutions and placing the solutions in the set P, namely, the solutions of the second leading edge surface;
(203-13) repeating the steps (203-11), (203-12) above for solutions in the set P, then all solutions in the third leading edge can be found; and so on until all solutions are placed in their respective fronts.
Among them, regarding dominance: for m objective functions h j (y), j=1, 2 … m, arbitrarily given two decision variables X A ，X B If for any j there is h j (X A )≤h j (X B ) Then call X A Dominating X B Otherwise call X A Not to govern X B 。
In the embodiment of the invention, in order to ensure diversity of population, even if solutions are distributed more uniformly in a target space, the concept of crowding degree is introduced. The calculation process of the crowding degree is as follows:
(203-21) for the first individual, taking one of the individuals l-1 and l+1 closest to it on both sides, taking two points l-1 and l+1 as vertices as rectangles, and the crowding degree being the perimeter of the rectangle. Here, the crowding degree of the individual at the edge is set to ++.
(203-22) calculating the crowdedness of the individuals in each of the fronts, and ordering all the individuals in the same fronts in descending order of crowdedness.
(203-23) after completion of the crowding descending order, selecting individuals from the first front surface until the total number of selected individuals reaches N, and forming a new parent population by the selected N individuals.
The embodiment of the invention adopts NSGA-II algorithm to control the inductance current and capacitance current values of the double-active bridge, searches the optimal control variable for the double-active bridge direct current converter, reduces the power loss of the converter and improves the efficiency characteristic of the converter. The intelligent optimization algorithm has fewer limitations on the optimization problem, only needs the information value of the objective function without other obvious limitations, and can be used for solving the problem of unsatisfied convexity and microposity, solving the problem of no analytical expression and solving the problem of constraint without obvious continuity compared with the traditional optimization algorithm.
In the above embodiment, the objective function is optimized by using NSGA-II (NSGA: non-dominated Sorting Genetic Algorithms, non-dominant inheritance) algorithm, and in other alternative embodiments, other optimization algorithms may be used.
In summary, the embodiment of the invention establishes the double-active-bridge time domain state space model based on the harmonic modeling method, and then obtains the minimum value corresponding to the inductance current and the capacitance current through the intelligent optimization algorithm, thereby reducing the loss of the double-active-bridge converter in energy transmission and realizing the efficiency optimization of the converter.
Accordingly, referring to fig. 4, an embodiment of the present invention provides an efficiency optimization apparatus for a dual active bridge, which includes:
a switching function creation module 401 for creating a fourier form based switching function that is a function of the total number of harmonics and the phase shift angle;
a harmonic model building module 402, configured to build an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model as objective functions by using the fourier-form-based switching function;
an optimizing module 403, configured to optimize the objective function based on a preset constraint condition, so as to obtain an optimal value of the total number of harmonics and an optimal value of the phase shift angle, so that an inductance current of the inductance current dynamic time domain harmonic model is minimum and a capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
an acquisition module 404 is configured to acquire the minimum inductor current and the minimum capacitor current.
In the embodiment of the invention, the inductance current dynamic time domain harmonic model and the capacitance current dynamic time domain harmonic model are established based on the harmonic modeling method, and the inductance current and the capacitance current are controlled to be minimized through the optimization algorithm, so that the power loss such as the loss of a switching tube, the loss of a transformer, the loss of a capacitance and the like can be reduced, and the efficiency of the double-active-bridge converter is improved. In addition, an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model are built based on a harmonic modeling method, so that the model is easier to solve, and the implementation is easier.
In some embodiments, the constraints include at least one of: the output power is constant, the calculation time does not exceed the maximum allowable value and the total number of harmonics is an integer.
In some specific embodiments, where the constraint includes that the output power is constant, the apparatus further comprises:
the relation function building module is used for building a relation function of the switching state and each output voltage;
and the output power function building module is used for building a function of output power in a harmonic form by utilizing the Fourier-form-based switching function and the relation function.
In some specific embodiments, the harmonic model building module 402 includes:
the establishing unit is used for establishing a dynamic time domain expression of the double-active bridge by utilizing the switching function expression based on the Fourier form;
the acquisition unit is used for deducing the time domain expression of the inductive current and the time domain expression of the capacitive current by utilizing the dynamic time domain expression of the double active bridge, wherein the time domain expression of the inductive current is used as the inductive current dynamic time domain harmonic model, and the time domain expression of the capacitive current is used as the capacitive current dynamic time domain harmonic model.
In some specific embodiments, the acquiring unit includes:
a first conversion subunit, configured to convert the dynamic time domain expression of the dual active bridge into a phase domain expression of the dual active bridge;
the first acquisition subunit is used for deriving a phase domain expression of the inductive current based on the phase domain expression of the double active bridge;
a second converting subunit, configured to convert the phase domain expression of the inductor current into a time domain expression of the inductor current;
and the second acquisition subunit is used for deriving the time domain expression of the capacitance current based on the time domain expression of the inductance current.
In some specific embodiments, the establishing unit includes:
the first building subunit is used for building a relation function of the switching state and each output voltage;
and the second establishing subunit is used for establishing a dynamic time domain expression of the double-active bridge by utilizing the relation function and the switching function expression based on the Fourier form.
In some specific embodiments, the optimizing module 403 includes:
a first generation unit for randomly generating an initial population with a scale of N as a parent population;
the second generation unit is used for obtaining a first generation offspring population through selection, crossing and mutation operations of a genetic algorithm after non-dominant sorting of the parent population; n is a positive integer;
the third generation unit is used for merging the parent population and the child population from the second generation to obtain a sequencing population with the scale of 2N, carrying out rapid non-dominant sequencing, simultaneously carrying out crowding degree calculation on individuals in each non-dominant layer, and selecting the individuals to form a new parent population according to the non-dominant relationship and the crowding degree of the individuals;
and the control unit is used for inputting the new parent population into the second generation unit, controlling the second generation unit and the third generation unit to run again until the maximum iteration number is met, stopping calculation, and obtaining the optimal value of the phase shift angle and the total number of harmonic waves.
The embodiment of the present invention is an embodiment of a device based on the same inventive concept as the embodiment of the above method, so specific technical details and corresponding technical effects refer to the embodiment of the above method, and are not described herein again.
The present invention also provides an electronic device, as shown in fig. 5, which may include a processor 51 and a memory 52, where the processor 51 and the memory 52 may be communicatively connected to each other via a bus or other means, and in fig. 5, the connection is exemplified by a bus.
The processor 51 may be a central processing unit (Central Processing Unit, CPU). The processor 51 may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof.
The memory 52 is used as a non-transitory computer readable storage medium, and may be used to store a non-transitory software program, a non-transitory computer executable program, and a module, such as program instructions/modules (e.g., the switching function creation module 401, the harmonic model creation module 402, the optimization module 403, and the acquisition module 404 shown in fig. 4) corresponding to the efficiency optimization method of the dual active bridge in the embodiment of the present invention. The processor 51 executes various functional applications of the processor and data processing by running non-transitory software programs, instructions and modules stored in the memory 52, i.e., implementing the dual active bridge efficiency optimization method in the method embodiments described above.
The one or more modules are stored in the memory 52, which when executed by the processor 51, performs the dual active bridge efficiency optimization method as in the method embodiments described above.
The specific details of the electronic device may be correspondingly understood by referring to the corresponding related descriptions and effects in the above method embodiments, which are not repeated herein.
Correspondingly, the embodiment of the invention also provides a computer readable storage medium, which is used for storing a computer program, when the computer program is executed by a processor, the processes of the above-mentioned dual-active-bridge efficiency optimization method embodiment are realized, and the same technical effects can be achieved, so that repetition is avoided, and the description is omitted here.
Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, as relevant to see a section of the description of method embodiments.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (7)
1. A method for optimizing efficiency of a dual active bridge, the method comprising:
establishing a fourier form-based switching function that is a function of the total number of harmonics and the phase shift angle;
establishing an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model as objective functions by using the switching function based on the Fourier form; the objective function is:
wherein i is L (t) is inductor current, i c (t) is capacitive current, P out (θ, K) is the output power in harmonic form based on the phase shift angle θ and the total number of harmonics K, P ref T is a constant value of output power cal To calculate the time, t max Calculating the maximum allowable value of time;
optimizing the objective function based on preset constraint conditions to obtain an optimal value of the total number of the harmonic waves and an optimal value of the phase shift angle, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
acquiring the minimum inductance current and the minimum capacitance current;
the establishing an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model by using the switching function based on the Fourier form comprises the following steps:
establishing a dynamic time domain expression of the double-active bridge by using the switching function expression based on the Fourier form;
deducing a time domain expression of the inductor current and a time domain expression of the capacitor current by using the dynamic time domain expression of the double active bridge, wherein the time domain expression of the inductor current is used as the inductor current dynamic time domain harmonic model, and the time domain expression of the capacitor current is used as the capacitor current dynamic time domain harmonic model;
the deriving the time domain expression of the inductor current and the time domain expression of the capacitor current by using the dynamic time domain expression of the double active bridge comprises:
converting the dynamic time domain expression of the double active bridge into a phase domain expression of the double active bridge;
deriving a phase domain expression of the inductor current based on the phase domain expression of the double active bridge;
converting the phase domain expression of the inductor current into a time domain expression of the inductor current; the time domain expression of the inductance current is:
wherein V is in For the input voltage of the double active bridge,
r is parasitic electricityResistance, L is inductance, V out For the output voltage of the dual active bridge,
f s is the switching frequency of the switching tubes in the double active bridge;
deriving a time domain expression of the capacitive current based on the time domain expression of the inductive current; the time domain expression of the capacitance current is as follows:
wherein i is out (t) is the output current of the double active bridge model, i Load (t) is the load current, S i (t) is a fourier-based form of the switching function of the switch Si, i=1, 2,3 …;
the creating a dynamic time domain expression of the double active bridge by using the switching function expression based on the Fourier form comprises the following steps:
establishing a relation function between a switching state and each output voltage;
and establishing a dynamic time domain expression of the double-active bridge by using the relation function and the switching function expression based on the Fourier form.
2. The method of claim 1, wherein the constraints include at least one of: the output power is constant, the calculation time does not exceed the maximum allowable value and the total number of harmonics is an integer.
3. The method of claim 2, wherein, in the case where the constraint includes the output power being constant, the method further comprises:
establishing a relation function between a switching state and each output voltage;
and establishing a function of output power in a harmonic form by using the Fourier form-based switching function and the relation function.
4. The method according to claim 1, wherein optimizing the objective function based on a preset constraint condition results in an optimal value of the total number of harmonics and an optimal value of the phase shift angle, comprising:
s201: randomly generating an initial population with the scale of N as a parent population;
s202: after non-dominant sorting is carried out on the parent population, a first generation offspring population is obtained through selection, crossing and mutation operations of a genetic algorithm; n is a positive integer;
s203: starting from the second generation, merging the parent population and the offspring population to obtain a sequencing population with the scale of 2N, carrying out rapid non-dominant sequencing, simultaneously carrying out crowding calculation on individuals in each non-dominant layer, and selecting the individuals to form a new parent population according to the non-dominant relationship and the crowding of the individuals;
s204: repeating steps S202 and S203 for the new parent population until the maximum number of iterations is met, stopping calculation, and obtaining the optimal value of the phase shift angle and the total number of harmonics.
5. An efficiency optimization device for a double active bridge, comprising:
a switching function establishing module for establishing a fourier form-based switching function, which is a function of the total number of harmonics and the phase shift angle;
the harmonic model building module is used for building an inductance current dynamic time domain harmonic model and a capacitance current dynamic time domain harmonic model by using the switching function based on the Fourier form as an objective function; the objective function is:
wherein i is L (t) is inductor current, i c (t) is capacitive current, P out (θ, K) is an input in harmonic form based on the phase shift angle θ and the total number of harmonics KOutput power, P ref T is a constant value of output power cal To calculate the time, t max Calculating the maximum allowable value of time;
the optimization module is used for optimizing the objective function based on preset constraint conditions to obtain an optimal value of the total number of the harmonic waves and an optimal value of the phase shift angle, so that the inductance current of the inductance current dynamic time domain harmonic model is minimum and the capacitance current of the capacitance current dynamic time domain harmonic model is minimum;
the acquisition module is used for acquiring the minimum inductive current and the minimum capacitive current;
the harmonic model building module comprises:
the establishing unit is used for establishing a dynamic time domain expression of the double-active bridge by utilizing the switching function expression based on the Fourier form;
the acquisition unit is used for deducing a time domain expression of the inductive current and a time domain expression of the capacitive current by utilizing the dynamic time domain expression of the double active bridge, wherein the time domain expression of the inductive current is used as the inductive current dynamic time domain harmonic model, and the time domain expression of the capacitive current is used as the capacitive current dynamic time domain harmonic model;
the acquisition unit includes:
a first conversion subunit, configured to convert the dynamic time domain expression of the dual active bridge into a phase domain expression of the dual active bridge;
the first acquisition subunit is used for deriving a phase domain expression of the inductive current based on the phase domain expression of the double active bridge;
a second converting subunit, configured to convert the phase domain expression of the inductor current into a time domain expression of the inductor current; the time domain expression of the inductance current is:
wherein V is in For the input voltage of the double active bridge,
r is parasitic resistance, L is inductance, V out For the output voltage of the dual active bridge,
f s is the switching frequency of the switching tubes in the double active bridge;
a second obtaining subunit, configured to derive a time domain expression of the capacitive current based on the time domain expression of the inductive current; the time domain expression of the capacitance current is as follows:
wherein i is out (t) is the output current of the double active bridge model, i Load (t) is the load current, S i (t) is a fourier-based form of the switching function of the switch Si, i=1, 2,3 …;
the establishing unit includes:
the first building subunit is used for building a relation function of the switching state and each output voltage;
and the second establishing subunit is used for establishing a dynamic time domain expression of the double-active bridge by utilizing the relation function and the switching function expression based on the Fourier form.
6. An electronic device, comprising:
a memory and a processor, the memory and the processor being communicatively connected to each other, the memory being configured to store a computer program which, when executed by the processor, implements the method of optimizing efficiency of a dual active bridge according to any one of claims 1 to 4.
7. A computer readable storage medium for storing a computer program which, when executed by a processor, implements the method of efficiency optimization of a dual active bridge according to any one of claims 1 to 4.
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