Bidirectional dual-active bridge circuit transformer optimization design method
By removing the resonant inductance in the bidirectional dual active bridge circuit and using the primary side leakage inductance to replace it, and combining the hiking optimization algorithm to design the transformer parameters, the problems of large transformer space and high material costs in the existing technology are solved, and more efficient and economical circuit design.
Patent Information
- Application Number
- CN202411357614.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2025-02-07
AI Technical Summary
In the existing bidirectional dual-active bridge circuit design, there are challenges in the energy efficiency and economics of the transformer, resulting in large space and high material costs.
By removing the resonant inductance in the bidirectional dual-active bridge circuit and using the transformer's primary side leakage inductance instead, the parameter design is used to optimize the transformer's size and performance parameters to reduce component number and energy loss.
While keeping the transformer performance unchanged, material usage and space occupation are reduced, and overall energy efficiency and economy are improved.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of circuit design, and in particular to an optimization design method for a bidirectional dual-active bridge circuit transformer. Background Art
[0002] With the technological innovation and progress in the field of power electronics, the bidirectional dual active bridge (DAB) circuit has been widely adopted in the design and application of power conversion and energy storage systems due to its excellent energy efficiency performance and excellent power density characteristics. In the field of power electronics technology, the bidirectional dual active bridge (DAB) circuit has attracted much attention due to its unique bidirectional power transmission function. This circuit can realize the flow of energy in two directions, that is, the bidirectional conversion and transmission of energy. This feature shows its vital role in application fields such as electric vehicle chargers and renewable energy systems. This bidirectional power flow capability of the DAB circuit provides a technical basis for the flexible management and optimal utilization of energy, thus playing a key role in improving system efficiency and economy.
[0003] The existing DAB circuit design still has some challenges in terms of transformer energy efficiency and economy. As a key component in the DAB circuit, the design and performance of the transformer directly affect the performance and cost of the entire system. The transformer of the traditional DAB circuit will be connected in series with a resonant inductor to form a resonant condition with the capacitor element at a specific frequency to achieve high-efficiency energy conversion and transmission, while reducing the voltage stress of the switching device, reducing electromagnetic interference, improving the dynamic response of the system, and helping to realize soft switching technology, thereby improving the efficiency and stability of the entire power electronic system.
[0004] However, due to the series connection of the resonant inductor, the overall circuit structure occupies a large space, resulting in the overall structure of the transformer becoming larger, and both the magnetic core and the coil require more material costs. Summary of the invention
[0005] The invention proposes a bidirectional dual-active bridge circuit transformer optimization design method to solve the technical problems that the existing bidirectional dual-active bridge circuit occupies a large space and has too high material cost.
[0006] In order to solve the above technical problems, the present invention provides a bidirectional dual active bridge circuit transformer optimization design method, comprising the following steps:
[0007] Step S1: removing the resonant inductor in the bidirectional dual active bridge circuit DAB;
[0008] Step S2: Given transformer parameters, construct an objective function based on transformer power and transformer cost;
[0009] Step S3: Under the condition that the leakage inductance of the primary side of the transformer is equal to the self-inductance of the series inductor, a walking optimization algorithm is used to solve the problem, and the parameters of the bidirectional dual active bridge circuit DAB without resonant inductance are obtained.
[0010] Preferably, in step S2, the objective function F(β) is expressed as:
[0011] F(β)=ω1F w (β)-ω2F p (β);
[0012] β=[n1 n2 ldh L mt V] T ;
[0013] F w (β) = w x (β)+w l (β);
[0014] F P (β) = P(β);
[0015]
[0016] w l (β) = γβ
[0017] γ=[γ1 γ2 0 0 0 0 0];
[0018] In the formula, F w (β) and F P (β) represents the transformer power function and transformer cost function respectively; ω1 and ω2 represent F w (β) and F P (β) is the weight coefficient; β represents the decision vector; n1 and n2 represent the number of turns of the primary and secondary sides of the transformer respectively; l, d and h represent the length, width and height of the transformer respectively; L mt represents the average length of each coil turn; V represents the winding width; w x (β) and w l (β) represents the cost of the transformer core and the cost of the high temperature film wire used in the transformer coil; P(β) represents the power of the transformer; and γ represent weight matrices; γ1 and γ2 represent weight coefficients.
[0019] Preferably, the leakage inductance L of the primary side of the transformer in step S3 is k and the self-inductance L of the series inductor r The expression is:
[0020]
[0021] Where K1 represents constant 3; L mt represents the average length of each coil turn; n1 represents the number of primary turns; V represents the winding width; T ins Indicates the insulation thickness, which is determined by the applied LITZ wire itself; b w Indicates the thickness of all windings;
[0022]
[0023] Where Q is the quality factor; R ac and R L are the resistance converted to the primary side and the load resistance respectively; f r is the resonant frequency, f r =f s1 , f s1 is the switching frequency.
[0024] Preferably, the method of solving the problem using the walking optimization algorithm in step S3 includes:
[0025] Step S31: adding constraints to the decision vector and performing random initialization;
[0026] Step S32: Based on the objective function, the fitness value is calculated to obtain the current best team leader;
[0027] Step S33: randomly generate a terrain inclination angle, and calculate the terrain slope and the traveler's initial speed based on the current best leader and the terrain inclination angle to update the traveler's speed;
[0028] Step S34: Based on the traveler's speed, the traveler's position is updated, and steps S32 to S34 are repeated to iterate to obtain an optimal decision vector, that is, parameters of the bidirectional dual active bridge circuit DAB without a resonant inductor.
[0029] Preferably, the expression for adding constraints in step S31 is:
[0030] minF(β)=ω1F w (β)-ω2F p (β)
[0031]
[0032] l min ≤l≤l max
[0033] d min ≤d≤d max
[0034] h min ≤h≤h max
[0035] L mt min ≤L mt ≤L mt max
[0036] V min ≤V≤V max ;
[0037] In the formula, l min , l max d min d max 、h min 、h max , L mt min , L mt max 、V min 、V max Respectively represent n1, n2, l, d, h, L mt , the upper and lower limits of V.
[0038] Preferably, in step S33, the terrain slope S is calculated i,t The expression is:
[0039] S i,t =tanθ i,t ;
[0040] In the formula, θ i,t Indicates the terrain inclination angle.
[0041] Preferably, in step S33, the traveler's initial speed W is calculated i,t The expression is:
[0042]
[0043] Preferably, the expression for updating the traveler's speed in step S33 is:
[0044] W i,t =W i,t-1 +γ i,t (β best -α i,t β i,t );
[0045] Where W i,t represents the speed of traveler i at the tth iteration; γ i,t is a number uniformly distributed between [0,1]; β best is the best leader position; α i,tis the sweep frequency factor (SF) of hiker i, which is in the interval [1,3]; β i,t represents the position of traveler i at the tth iteration, that is, the decision vector of traveler i at the tth iteration.
[0046] Preferably, the expression for updating the traveler's position in step S34 is:
[0047] β i,t+1 =β i,t +W i,t .
[0048] The beneficial effects of the present invention include at least: based on the existing bidirectional dual-active bridge circuit, the present invention removes the resonant inductor and replaces it with the original transformer primary leakage inductance, thereby reducing the number of components, thereby reducing the complexity and energy loss of the system and improving the overall energy efficiency.
[0049] At the same time, by giving the required transformer parameters, the walking optimization algorithm is used to design the transformer size and performance parameters, so that the resonant inductor is omitted and the complex air gap size determination is omitted, and the optimized transformer primary leakage inductance and the sum of the transformer primary leakage inductance and the series inductance before optimization are kept almost the same, so that less consumables are used and more space is saved without changing the effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] Figure 1 A schematic diagram of a method flow chart of an embodiment of the present invention;
[0051] Figure 2 A schematic diagram of a bidirectional dual active bridge (DAB) integrated transformer topology structure according to an embodiment of the present invention;
[0052] Figure 3 This is a schematic diagram of an integrated transformer design model optimized according to an embodiment of the present invention;
[0053] Figure 4 A schematic diagram of a transformer model before optimization according to an embodiment of the present invention;
[0054] Figure 5 The figure is a schematic diagram of the calculation flow of the walking optimization algorithm according to an embodiment of the present invention. DETAILED DESCRIPTION
[0055] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.
[0056] like Figure 1 As shown, an embodiment of the present invention provides a bidirectional dual active bridge circuit transformer optimization design method, comprising the following steps:
[0057] Step S1: removing the resonant inductor in the bidirectional dual active bridge circuit DAB.
[0058] Specifically, Figure 2 , which is a schematic diagram of the topological structure after removing the resonant inductor in the bidirectional dual active bridge circuit DAB according to an embodiment of the present invention.
[0059] The structure includes: a switch network 100 on the primary side of the transformer, a resonant network 200 and a switch network 300 on the secondary side of the transformer.
[0060] The switch network 100 on the primary side of the transformer includes: a primary side support capacitor (C1), primary side switch tubes (VD1, VD2, VD3, VD4) and corresponding drive signals (S1, S2, S3, S4).
[0061] The resonant network 200 includes resonant capacitors (Cr1, Cr2) and a transformer (T).
[0062] The switch network 300 on the secondary side of the transformer includes: a support capacitor (Cm) during reverse operation, secondary side switch tubes (VD5, VD6, VD7, VD8), and corresponding drive signals (S5, S6, S7, S8).
[0063] In a conventional bidirectional dual active bridge (DAB) circuit, the primary coil of the transformer needs to be connected in series with a resonant series inductor Lr. In an embodiment of the invention, the primary leakage inductor of the transformer is used to replace the resonant inductor.
[0064] Figure 3 It is an integrated transformer optimization design model and a transformer core three-view drawing, and its structure includes: a transformer core 1, a transformer primary coil 2 and a transformer secondary coil 3.
[0065] Transformer core 1: It consists of two separate cores placed opposite each other to ensure the integrity and efficiency of the magnetic circuit. To meet safety regulations, a double layer of thick tape is pasted between the cores to prevent possible insufficient electrical clearance issues.
[0066] In the three-view drawing of the transformer core, the corresponding length, width and height dimensions are: l, d, h.
[0067] Transformer primary coil 2: multi-strand LITZ structure high temperature film-wrapped enameled wire;
[0068] Transformer secondary coil 3: multi-strand LITZ structure high temperature film-wrapped enameled wire.
[0069] Figure 4This is the transformer model before optimization. It can be seen that compared with the optimized model, it obviously requires more cost on the core and the coil, and occupies more space.
[0070] Step S2: Given transformer parameters, construct an objective function based on transformer power and transformer cost.
[0071] Specifically, the number of turns of the primary coil of the transformer n1, the number of turns of the secondary coil of the transformer n2, the length l, width d, height h of a single magnetic core of the transformer, and the average length of each coil turn L mt , winding width V, etc. are taken as optimization parameters, and the optimization problem is established, which together constitute the decision vector β, and finally the optimal energy efficiency and economy of the bidirectional dual active bridge (DAB) circuit transformer is obtained.
[0072] The goal is to improve the energy efficiency and economic optimization of the bidirectional dual active bridge (DAB) circuit transformer, specifically including optimizing the physical structure of the bidirectional dual active bridge (DAB) circuit transformer to achieve the purpose of saving space and cost; optimizing the parameter composition of the bidirectional dual active bridge (DAB) circuit transformer, focusing on the specific number of turns of the primary and secondary coils of the transformer, which is also a determined decision variable. The embodiment of the present invention uses Maxwell magnetic simulation software to establish a new transformer simulation model, and through the windows com interface of Maxwell and python, the automatic simulation analysis of the Maxwell simulation model is realized in python.
[0073] Under given transformer parameters, energy efficiency and economic indicators such as power and cost are obtained through Maxwell simulation. The comprehensive objectives are defined as follows:
[0074] F(β)=ω1F w (β)-ω2F p (β);
[0075] In the formula, F w (β), F P (β) are transformer power function and transformer cost function, ω1 and ω2 are F w (β) and F P (β) is the weight coefficient; β represents the decision vector, and its expression is:
[0076] β=[n1 n2 ldh L mt V] T ;
[0077] F w (β) and F P The expressions of (β) are:
[0078] F w (β) = w x(β)+w l (β);
[0079] F P (β) = P(β);
[0080] Among them, w x (β) and w l (β) respectively represent the cost of the transformer core and the cost of the high-temperature film wire used in the transformer coil; the transformer core cost is mainly determined by the length, width and height of the transformer, while the cost of the high-temperature film wire is mainly determined by the number of turns of the primary and secondary coils of the transformer, so:
[0081]
[0082] w l (β) = γβ
[0083] γ = [γ1γ200000];
[0084] and γ represent weight matrices; γ1 and γ2 represent weight coefficients.
[0085] Step S3: Under the condition that the leakage inductance of the primary side of the transformer is equal to the self-inductance of the series inductor, a walking optimization algorithm is used to solve the problem, and the parameters of the bidirectional dual active bridge circuit DAB without resonant inductance are obtained.
[0086] Since the present invention uses the primary leakage inductance of the transformer to replace the resonant inductance, the design of the transformer needs to meet certain requirements. First, the leakage inductance of the primary side of the transformer is:
[0087]
[0088] Here, K1 represents a constant 3, L mt It represents the average length of each coil turn, in (1 in = 25.4 mm), n1 represents the number of primary turns, V represents the winding width, in, T ins Indicates the insulation thickness, which is determined by the applied LITZ wire itself, b w Indicates the thickness of all windings.
[0089] In this study, L k =L r , L r The expression is:
[0090]
[0091] Among them, L r is the self-inductance of the series inductor; Q is the quality factor, which is usually taken as 95% to ensure a certain ZVS margin; R ac and RL are the resistance converted to the primary side and the load resistance respectively; f r is the resonant frequency. In order to make the LLC converter operate at the optimal efficiency, let f r =f s1 , f s1 is the switching frequency; n1 is the number of turns on the primary side of the transformer.
[0092] In the above formula, P(β) represents the power of the transformer. From the above formula, it can be concluded that the power of the transformer is related to n1, n2, L mt ,V are closely related, so they can be expressed as:
[0093] F p (β) = P (β) = ηβ
[0094] η=[η1 η2 0 0 0 η3 η4];
[0095] Among them, η is the weight matrix, and η1, η2, η3, and η4 are the weight coefficients in the weight matrix respectively.
[0096] Combining the objective function with the decision variables, the energy efficiency and economic optimization problem of the bidirectional dual active bridge (DAB) circuit transformer is obtained:
[0097] minF(β)=ω1F w (β)-ω2F p (β)
[0098]
[0099] l min ≤l≤l max
[0100] d min ≤d≤d max
[0101] h min ≤h≤h max
[0102] L mt min ≤L mt ≤L mt max
[0103] V min ≤V≤V max ;
[0104] In the formula l min , l max d min d max 、h min、h max , L mt min , L mt max 、V min 、V max Respectively represent n1, n2, l, d, h, L mt , the upper and lower limits of V.
[0105] Afterwards, the optimization problem is formulated as a vector with random initialization:
[0106] β=[n1 n2 ldh L mt V] T ;
[0107] That is, β is expressed by the above formula, and the constraint can be described as (β) k,min ≤(β) k ≤(β) k,max , Among them, (β) k represents the kth element in the decision vector, (β) k,max and (β) k,min They represent the upper and lower bounds of the kth element respectively, and |β| represents the dimension of the vector.
[0108] In the embodiment of the present invention, a walking optimization algorithm is used to solve Figure 5 The Hiking Optimization Algorithm, shown in Figure 1, is a metaheuristic algorithm inspired by the experience of hikers trying to reach the top of a mountain, hill, or rock, as the case may be. While hiking, hikers consciously or unconsciously take into account the steepness of the terrain. They avoid very steep terrain and trails in order to maintain their hiking or walking speed. In other words, highly steep terrain and trails slow down the hiker's speed and ultimately extend the duration of the hike. With the knowledge of the geography of the terrain, the hiker can determine or roughly estimate the time required to reach the top of the mountain. This is similar to an agent trying to find the local optimum or the global optimum of an optimization problem.
[0109] Calculate the terrain slope S i,t and the traveler's initial speed W i,t The expression is:
[0110]
[0111] S i,t =tanθ i,t ;
[0112] Among them, W i,t is the speed of hiker i at iteration or time t in km / h, S i,t is the slope of the terrain, where θi,t is the terrain inclination, θ i,t ∈[0,50°], is randomly generated.
[0113] The hiker's current speed:
[0114] W i,t =W i,t-1 +γ i,t (β best -α i,t β i,t );
[0115] Where W i,t represents the speed of traveler i at the tth iteration; γ i,t is a number uniformly distributed between [0,1]; β best is the position of the lead hiker; α i,t is the sweep frequency factor (SF) of hiker i, which is in the interval [1,3]. SF ensures that hikers do not stray too far from the lead hiker, and they can see the direction of the lead hiker and receive the signal from the lead hiker; β i,t represents the position of traveler i at the tth iteration, that is, the decision vector of traveler i at the tth iteration.
[0116] Updated position of hiker i β i.t+1 for:
[0117] β i,t+1 =β i,t +W i,t ;
[0118] After that, the group fitness is updated and the leader is re-evaluated, that is, the obtained β parameter is brought into F(β) to obtain the latest F(β) fitness, that is, the comprehensive objective function. If the iteration requirements are met, the best optimization solution is output, if not, the iteration continues.
[0119] The bidirectional dual active bridge circuit transformer is optimized by adopting the scheme of the embodiment of the present invention, and the air gap of the optimized model is cancelled, which is more suitable for the large-scale optimization in the present invention. The air gap of the model before optimization is kept at 4mm. By using Maxwell simulation, the total inductance value of the leakage inductance of the primary coil plus the series inductance before optimization and the simulation value of the leakage inductance of the primary coil of the transformer after optimization can be obtained, and the results are shown in Table 1.
[0120] Table 1
[0121] Before optimization After optimization Air Gap 4mm 0mm Sensitivity 85.9241uH 85.7835uH
[0122] It can be seen from the table that the embodiment of the present invention omits the series resonant inductance of the transformer in the bidirectional dual active bridge circuit DAB to save space while ensuring the effectiveness of the overall inductance value, that is, the optimized transformer primary leakage inductance and the sum of the transformer primary leakage inductance and the series inductance before optimization are almost the same, and the leakage inductance replaces the overall inductance value.
[0123] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. Only the preferred embodiments of the present invention are expressed. The description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. As long as there is no contradiction in the combination of these technical features, they should be considered as the scope recorded in this specification.
[0124] It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A bidirectional dual active bridge circuit transformer optimization design method, characterized in that: The following steps are involved: Step S1: removing the resonant inductor in the bidirectional dual active bridge circuit DAB; Step S2: Given transformer parameters, construct an objective function based on transformer power and transformer cost; Step S3: Under the condition that the leakage inductance of the primary side of the transformer is equal to the self-inductance of the series inductor, a walking optimization algorithm is used to solve the problem, and the parameters of the bidirectional dual active bridge circuit DAB without resonant inductance are obtained.
2. The bidirectional dual active bridge circuit transformer optimization design method according to claim 1, characterized in that: In step S2, the expression of the objective function F(β) is: F(β)=ω1F w (b)-ω2F p (b); β=[n1 n2 ldh L mt [V] T ; F w (b)=w x (b)+w l (b); F P (β)=P(β); w l (b)=cb γ=[γ1 γ2 0 0 0 0 0]; In the formula, F w (β) and F P (β) represents the transformer power function and transformer cost function respectively; ω1 and ω2 represent F w (β) and F P (β) is the weight coefficient; β represents the decision vector; n1 and n2 represent the number of turns of the primary and secondary sides of the transformer respectively; l, d and h represent the length, width and height of the transformer respectively; L mt represents the average length of each coil turn; V represents the winding width; w x (β) and w l (β) represents the cost of the transformer core and the cost of the high temperature film wire used in the transformer coil; P(β) represents the power of the transformer; and γ represent weight matrices; γ1 and γ2 represent weight coefficients.
3. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 2, characterized in that: The leakage inductance L of the primary side of the transformer in step S3 k and the self-inductance L of the series inductor r The expression is: Where K1 represents constant 3; L mt represents the average length of each coil turn; n1 represents the number of primary turns; V represents the winding width; T ins Indicates the insulation thickness, which is determined by the applied LITZ wire itself; b w Indicates the thickness of all windings; Where Q is the quality factor; R ac and R L are the resistance converted to the primary side and the load resistance respectively; f r is the resonant frequency, f r =f s1 , f s1 is the switching frequency.
4. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 2, characterized in that: The method of solving the problem by using the walking optimization algorithm in step S3 includes: Step S31: adding constraints to the decision vector and performing random initialization; Step S32: Based on the objective function, the fitness value is calculated to obtain the current best team leader; Step S33: randomly generate a terrain inclination angle, and calculate the terrain slope and the traveler's initial speed based on the current best leader and the terrain inclination angle to update the traveler's speed; Step S34: Based on the traveler's speed, the traveler's position is updated, and steps S32 to S34 are repeated to iterate to obtain an optimal decision vector, that is, parameters of the bidirectional dual active bridge circuit DAB without a resonant inductor.
5. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 4, characterized in that: The expression for adding constraints in step S31 is: In the formula, l min , l max d min d max 、h min 、h max , L mt min , L mt max 、V min 、V max Respectively represent n1, n2, l, d, h, L mt , the upper and lower limits of V.
6. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 5, characterized in that: In step S33, the terrain slope S is calculated. i,t The expression is: S i,t =tanθ i,t ; In the formula, θ i,t Indicates the slope angle of the terrain.
7. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 6, characterized in that: In step S33, the traveler's initial speed W is calculated. i,t The expression is:
8. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 7, characterized in that: The expression for updating the traveler's speed in step S33 is: W i,t =W i,t-1 +g i,t (b best -a i,t b i,t ); Where W i,t represents the speed of traveler i at the tth iteration; γ i,t is a number uniformly distributed between [0,1]; β best is the best leader position; α i,t is the sweep frequency factor (SF) of hiker i, which is in the interval [1,3]; β i,t represents the position of traveler i at the tth iteration, that is, the decision vector of traveler i at the tth iteration.
9. The method for optimizing the design of a bidirectional dual active bridge circuit transformer according to claim 8, characterized in that: The expression for updating the traveler's position in step S34 is: β i,t+1 ＝β i,t +W i,t 。