Three-phase LLC resonant converter parameter design method and system based on time domain model

Abstract

The invention discloses a three-phase LLC resonant converter parameter design method and system based on a time domain model, and belongs to the field of power electronic resonant converter parameter design, and the method comprises the following steps: determining a design demand and working condition distribution; according to the time domain model of the three-phase LLC resonant converter, respectively selecting feasible working modes for different working conditions; according to the selection result of the working modes, the transformation ratio n of the transformer is designed, and the maximum gain Mmax and the minimum gain Mmin are calculated; establishing a relationship between the effective value of the resonance current and the parameters of the resonance converter, and deducing an optimal parameter design constraint condition of the effective value of the resonance current under all working conditions; and solving the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonance current under all working conditions by adopting an optimization method on the premise of meeting all parameter design constraint conditions. The method can optimize the effective value of the full-working-condition resonance current and improve the efficiency of the converter.

Description

Technical Field

[0001] The invention belongs to the field of power electronic resonant converter parameter design, and relates to a three-phase LLC resonant converter parameter design method and system based on a time domain model. Background Art

[0002] In order to cope with climate change and reduce greenhouse gas emissions, electric vehicles have received widespread attention and are developing rapidly. Electric vehicle charging equipment is particularly important for the driving experience. It needs to meet a wide voltage and power output range and have a greater power transmission capacity. As the core part of the charging equipment, the performance of the isolated DC-DC converter determines the performance of the charging equipment. The LLC resonant converter can achieve soft switching within a wide voltage output range, has high efficiency and power density, and is a suitable choice for isolated DC-DC converters. It has been widely used. Compared with the traditional single-phase LLC resonant converter, the three-phase LLC resonant converter has smaller output current ripple and higher efficiency in high-power scenarios. Therefore, when considering high-power charging, the three-phase LLC resonant converter has more advantages.

[0003] Reasonable design is the key to ensure the high performance of three-phase LLC resonant converter. At present, the three-phase LLC resonant converter is basically designed by the fundamental wave analysis method (First Harmonic Approximation, FHA). However, the fundamental wave analysis method adopts approximation in the modeling process, and the accuracy is very poor when the switching frequency deviates from the resonant frequency. Therefore, when the fundamental wave analysis method is used to design wide voltage range application scenarios, the resonant cavity cannot be fully utilized and the efficiency needs to be improved. The time-domain model (Time-Domain Model, TDM) can solve the problem of poor accuracy of the fundamental wave analysis method and help to achieve the parameter optimization design of the resonant converter, but it has not yet been applied to the wide voltage range parameter design of the three-phase LLC resonant converter.

[0004] Therefore, there is currently no design method that can accurately optimize the three-phase LLC resonant converter under a wide voltage range. A design method based on time domain analysis is needed to optimize the converter efficiency through reasonable design based on an accurate description of the converter's characteristics. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a three-phase LLC resonant converter parameter design method and system based on a time domain model, which can meet the application scenarios with a wide voltage and load output range and improve the full-range working efficiency of the converter.

[0006] In order to achieve the above purpose, the present invention adopts the following technical means: In a first aspect, the present invention provides a three-phase LLC resonant converter parameter design method based on a time domain model, comprising: Determine design requirements and operating conditions distribution; Based on the design requirements and operating condition distribution, feasible operating modes are selected for different operating conditions according to the time domain model of the three-phase LLC resonant converter; According to the working mode selection results, the transformer ratio is designed and the maximum gain and minimum gain are calculated; According to the time domain model of the three-phase LLC resonant converter, the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter is established, and the constraint conditions for the design of the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all working conditions are derived based on the maximum gain and minimum gain; Using the optimization method, the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions are solved under the premise of satisfying all parameter design constraints.

[0007] As a further improvement of the present invention, the determining of design requirements and operating condition distribution includes: For the three-phase LLC resonant converter, L r is the resonant inductor, C r is the resonant capacitor, L m is the excitation inductance, n is the transformer ratio, f s is the switching frequency, the resonant frequency f r , inductance ratio k, characteristic impedance Z r as follows:

[0008] Determine the design operating conditions and clarify the voltage gain and load characteristics under different operating conditions.

[0009] As a further improvement of the present invention, based on the design requirements and the operating condition distribution, according to the time domain model of the three-phase LLC resonant converter, feasible operating modes are selected for different operating conditions, specifically including: 21) According to the ZVS conditions of the three-phase LLC resonant converter, all the working modes that can achieve ZVS are determined. The conditions for achieving ZVS are:

[0010] where i * r0 is the normalized resonant current when the inverter switch is turned on, i * r,ZVS is the normalized critical resonant current for achieving ZVS, C oss is the output capacitance of the inverter switch, t d is the dead time; 22) According to the ZCS condition of the three-phase LLC resonant converter, determine all the working modes that can achieve ZCS. The condition for achieving ZCS is that the secondary current of the resonant cavity is discontinuous; 23) Among the working modes that can achieve both ZVS and ZCS, select appropriate working modes for different working conditions.

[0011] As a further improvement of the present invention, the determining of the working mode capable of realizing both ZVS and ZCS at the same time includes: There are four operating modes in the under-resonance region and two operating modes in the over-resonance region; According to the voltage gain and load characteristics of each working condition, the appropriate working mode is selected respectively. The over-resonance region is suitable for low voltage gain and light load conditions, and the under-resonance region is suitable for high voltage gain conditions.

[0012] As a further improvement of the present invention, the criteria for selecting the working mode are: on the one hand, the gain and load output requirements must be met; on the other hand, the maximum output power p * o,max Less than the maximum feasible power p * max To simplify the calculation, we use the ZVS power boundary p * ZVS Instead of the maximum feasible power p * max .

[0013] As a further improvement of the present invention, the transformer ratio is designed according to the working mode selection result, and the maximum gain and the minimum gain are calculated, including: According to the working mode selection results, the transformer ratio n is designed, and the transformer ratio n is calculated according to the boundary working point T1 of the over-resonance region and the under-resonance region as follows:

[0014] The maximum gain and minimum gain are calculated as follows: .

[0015] As a further improvement of the present invention, the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter is established based on the time domain model of the three-phase LLC resonant converter, specifically including: 41a) According to the time domain model of the three-phase LLC resonant converter, the resonant current effective value I is established r,rms Relationship with resonant converter parameters:

[0016] Where M is the voltage gain, I o is the output current, f n= f s / f r To normalize the switching frequency, since the time domain model cannot obtain an analytical solution, h is used to represent the existing functional relationship; 41b) For any given operating point P, the voltage gain M and output current I o is fixed. According to the time domain model, the relationship between the remaining three parameters is:

[0017] 41c) According to 41a) and 41b), for any determined operating point P, the effective value of the resonant current I r,rms,P With k and f n related:

[0018] where h P Represents the effective value of the resonant current at the operating point P and the parameters k and f n Functional relationship of 41d) Plot f n The trend diagram of the resonant current effective value and inductance ratio k at the fixed working point P. According to the trend diagram, k and the ZVS margin (i * r0 / i * r,ZVS ) relationship.

[0019] As a further improvement of the present invention, the constraint conditions for the parameter design of the three-phase LLC resonant converter with the optimal resonant current effective value under all working conditions based on the maximum gain and the minimum gain specifically include: 42a) The optimal condition for the effective value of the resonant current under all operating conditions is that the maximum output power p * o,max Equal to the ZVS power boundary p * ZVS Minimum value of:

[0020] where p * diff is the ZVS power boundary p * ZVS Minimum and maximum output power p * o,max difference; 42b) There are infinite parameters that satisfy the conditions in 42a), and the maximum gain M needs to be selected max The working point Γ is constrained to determine the unique solution:

[0021] where ks and Z rs is the parameter solution, f n,Γ is the switching frequency of the operating point Γ; 42c) Combining 42a) and 42b), when the switching frequency f of the operating point Γ n,Γ When fixed, the optimal parameter solution k for the effective value of the resonant current under all working conditions s and Z rs Can be obtained by n,Γ The effective value of the resonant current under full working condition is determined by the effective value of the resonant current at the working point Γ. r,rms,Γ To measure: .

[0022] As a further improvement of the present invention, the optimization method is used to solve the three-phase LLC resonant converter parameters with the optimal effective value of the resonant current under all working conditions under the premise of satisfying all parameter design constraints, including 51) Determine the minimum gain constraint, the constraint condition is, the maximum switching frequency f s,max The voltage gain at the output current is I o,min When the voltage gain is less than the minimum M min , the corresponding constraint expression is:

[0023] 52) Perform optimal solution, the goal is to solve I r,rms,Γ The minimum value of , constrained by the minimum gain constraint in 51) and the given minimum switching frequency constraint, the solution expression is as follows:

[0024] 53) According to 52), the switching frequency f of the operating point Γ is obtained. n,Γ , parameter k s and Z rs , by a given resonant frequency f r , calculate the resonant inductance L r , resonant capacitor C r and the magnetizing inductance L m : .

[0025] In a second aspect, the present invention provides a three-phase LLC resonant converter parameter design system based on a time domain model, comprising: Determine the unit, which is used to determine the design requirements and operating condition distribution; A selection unit, configured to select feasible working modes for different working conditions based on the design requirements and working condition distribution and according to a time domain model of the three-phase LLC resonant converter; A design unit, used to design a transformer ratio according to a working mode selection result, and calculate a maximum gain and a minimum gain; An establishing unit is used to establish the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter according to the time domain model of the three-phase LLC resonant converter, and derive the constraint conditions of the parameter design of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all working conditions based on the maximum gain and the minimum gain; The optimization unit is used to solve the three-phase LLC resonant converter parameters with the optimal effective value of the resonant current under all working conditions by using an optimization method under the premise of satisfying all parameter design constraints.

[0026] The present invention has the following technical effects: The present invention accurately analyzes the behavior of the converter under different working conditions through a time domain model, and designs parameters accordingly, which can significantly improve the working efficiency of the converter within the full voltage and load output range. This method can cope with application scenarios with wide voltage and load output, meet the performance requirements under different working conditions, and enhance the applicability and flexibility of the converter. By establishing the relationship between the effective value of the resonant current and the parameters, and deriving the constraints of the optimized design, the design process is made more systematic and scientific, and the complexity and uncertainty of the design are reduced. Compared with the traditional frequency domain model, the time domain model is used for analysis, which can more accurately reflect the operating characteristics of the converter, thereby improving the accuracy and reliability of the design. By optimizing the effective value of the resonant current, the loss and heat generation of the converter during operation can be reduced, while reducing electromagnetic interference and improving the stability and reliability of the system. In summary, the parameter design method and system of the three-phase LLC resonant converter based on the time domain model proposed in the present invention have significant advantages in improving the full range of converter working efficiency, adapting to a wide range of applications, optimizing the design process, improving design accuracy and enhancing system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a flow chart of parameter design of a three-phase LLC resonant converter based on a time domain model of the present invention; Figure 2 It is the topological structure diagram of the three-phase LLC resonant converter; Figure 3 It is a schematic diagram of the working condition of the charging scenario; Figure 4It is the working modal distribution diagram of ZVS; Figure 5 It is the power-switching frequency operating modal distribution diagram where power and gain are negatively correlated; Figure 6 It is the power-switching frequency operating modal distribution diagram where power and gain are positively correlated; Figure 7 It is a relationship diagram between the relative position of any working point P in the voltage gain-switching frequency working plane and the inductance ratio; Figure 8 It is the relationship between the effective value of the resonant current and the ZVS margin at any operating point P; Fig. 9 is the relationship between the voltage gain and the resonance parameters at the maximum switching frequency and the minimum output current; Fig.10 This is a comparison chart of the effective values ​​of the resonant current of the three design methods under constant voltage charging and constant power charging conditions; Fig.11 This is a comparison chart of the efficiency of the three design methods under constant voltage charging and constant power charging conditions. DETAILED DESCRIPTION

[0029] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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 are within the scope of the present invention.

[0031] In a first aspect, the present invention provides a three-phase LLC resonant converter parameter design method based on a time domain model, and the design steps are as follows: 1) Determine the design requirements and operating conditions. For a three-phase LLC resonant converter, L r is the resonant inductor, C r is the resonant capacitor, L m is the excitation inductance, n is the transformer ratio, f s is the switching frequency, the resonant frequency f r , inductance ratio k, characteristic impedance Z r as follows:

[0032] 2) According to the time domain model of the three-phase LLC resonant converter, feasible working modes are selected for different working conditions to ensure the realization of zero voltage switching (Zero Voltage Switching, ZVS) of the inverter side switch and zero current switching (Zero Current Switching, ZCS) of the rectifier side diode while meeting the output voltage and power requirements; 3) According to the working mode selection results in step 2), design the transformer ratio n and calculate the maximum gain M max and minimum gain M min ; 4) Establish the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter, and derive the constraint conditions for the design of the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions; 5) Using the optimization method, the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions are solved under the premise of satisfying all parameter design constraints.

[0033] The present invention proposes a three-phase LLC resonant converter parameter design method and system based on a time domain model, aiming to solve the problems of low converter efficiency and complex design under a wide voltage and load output range in the prior art.

[0034] First, the specific application scenarios of the converter are clarified, such as the voltage input range, load variation range, etc. This is the basis of the design. The time domain model of the three-phase LLC resonant converter is used, which can more accurately reflect the operating behavior of the converter under different working conditions. According to the design requirements and working condition distribution, the working mode that is feasible and efficient under different working conditions is selected, which is a key step in optimizing the design.

[0035] Design the transformer ratio to ensure that the voltage conversion requirements can be met under different working conditions. Calculate the maximum gain and minimum gain, which are important references for subsequent parameter design.

[0036] Based on the time domain model, the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter (such as resonant frequency, inductance, capacitance, etc.) is established. By analyzing these relationships, the optimal constraint conditions for the effective value of the resonant current under all working conditions are derived, and these conditions will guide the subsequent parameter optimization.

[0037] Finally, under the premise of satisfying all parameter design constraints, optimization methods (such as genetic algorithm, particle swarm algorithm, etc.) are used to solve the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions.

[0038] The following is a detailed description of each step: The step 2) specifically includes: 21) According to the ZVS conditions of the three-phase LLC resonant converter, all the working modes that can achieve ZVS are determined. The conditions for achieving ZVS are:

[0039] where i * r0 is the normalized resonant current when the inverter switch is turned on, i * r,ZVS is the normalized critical resonant current for achieving ZVS, C oss is the output capacitance of the inverter switch, t d is the dead time; 22) According to the ZCS condition of the three-phase LLC resonant converter, determine all the working modes that can achieve ZCS. The condition for achieving ZCS is that the secondary current of the resonant cavity is discontinuous; 23) In the working mode that can achieve ZVS and ZCS at the same time, the appropriate working mode is selected for different working conditions. The selection criteria must meet the gain and load output requirements on the one hand and the maximum output power p on the other hand. * o,max Less than the maximum feasible power p * max To simplify the calculation, we use the ZVS power boundary p * ZVS Instead of the maximum feasible power p * max .

[0040] The step 4) establishes the relationship between the effective value of the resonant current and the resonant converter parameters, specifically including: 41a) According to the time domain model of the three-phase LLC resonant converter, the resonant current effective value I is established r,rms Relationship with resonant converter parameters:

[0041] Where M is the voltage gain, I o is the output current, f n = f s / f r To normalize the switching frequency, since the time domain model cannot obtain an analytical solution, h is used to represent the existing functional relationship; 41b) For any given operating point P, the voltage gain M and output current I o is fixed, and according to the time domain model, there is a relationship between the remaining three parameters:

[0042] 41c) According to 41a) and 41b), for any determined operating point P, the effective value of the resonant current Ir,rms,P Only with k and f n related:

[0043] where h P Represents the effective value of the resonant current at the operating point P and the parameters k and f n Functional relationship of 41d) Plot f n The trend diagram of the resonant current effective value and inductance ratio k of the working point P when fixed. According to the trend diagram, the smaller k is, the smaller the ZVS margin (i * r0 / i * r,ZVS ) is smaller, the effective value of the resonant current is smaller.

[0044] The constraints for deriving the optimal parameter design of the three-phase LLC resonant converter for the effective value of the resonant current under all operating conditions in step 4) specifically include: 42a) The optimal condition for the effective value of the resonant current under all operating conditions is that the maximum output power p * o,max Equal to the ZVS power boundary p * ZVS Minimum value of:

[0045] where p * diff is the ZVS power boundary p * ZVS Minimum and maximum output power p * o,max difference; 42b) There are infinite parameters that satisfy the conditions in 42a), and the maximum gain M needs to be selected max The working point Γ is constrained to determine the unique solution:

[0046] where k s and Z rs is the parameter solution, f n,Γ is the switching frequency of the operating point Γ; 42c) Combining 42a) and 42b), when the switching frequency f of the operating point Γ n,Γ When fixed, the optimal parameter solution k for the effective value of the resonant current under all working conditions s and Z rs Can be obtained by n,Γ The only way to determine the effective value of the resonant current under full working conditions is to use the effective value of the resonant current at the working point Γ, I r,rms,Γ To measure:

[0047] The step 5) includes 51) Determine the minimum gain constraint, the constraint condition is, the maximum switching frequency f s,max The voltage gain at the output current is I o,min When the voltage gain is less than the minimum M min , the corresponding constraint expression is:

[0048] 52) Perform optimal solution, the goal is to solve I r,rms,Γ The minimum value of , constrained by the minimum gain constraint in 51) and the given minimum switching frequency constraint, the solution expression is as follows:

[0049] 53) According to 52), the switching frequency f of the operating point Γ is obtained. n,Γ , parameter k s and Z rs , by a given resonant frequency f r , the resonant inductance L can be calculated r , resonant capacitor C r and the magnetizing inductance L m :

[0050] The steps of the present invention are described in detail below with reference to the accompanying drawings: Figure 1 The steps of the parameter design method of the three-phase LLC resonant converter based on the time domain model are provided as follows: 1. Determine design requirements and working condition distribution according to Figure 2 , for the three-phase LLC resonant converter, L r is the resonant inductor, C r is the resonant capacitor, L m is the excitation inductance, n is the transformer ratio, f s is the switching frequency, the resonant frequency f r , inductance ratio k, characteristic impedance Z r as follows:

[0051] Determine the design conditions for electric vehicle charging application scenarios. Figure 3A schematic diagram of the working conditions is given, which includes four working conditions: pre-charging, constant current charging (CC), constant power charging (CP) and constant voltage charging (CV). The working points T1, T2 and T3 are the boundary working points between adjacent working conditions. Specific parameters are given, including the rated power P rated , input voltage V in , output voltage V o,min ~ V o,max , resonant frequency f r , switching frequency lower limit f s,min With the upper limit f s,max , and the boundary operating point voltage, as shown in Table 1: Table 1

[0052] Select the primary switch tube as CI60N120SM, the secondary diode as CI40S65D3, and determine the output capacitance C of the primary switch tube. oss is 400pF, and the dead time t is taken into consideration d is 250ns.

[0053] 2. According to the time domain model of the three-phase LLC resonant converter, feasible working modes are selected for different working conditions; 21) Determine all the working modes that can achieve ZVS. The conditions for achieving ZVS are:

[0054] where i * r0 is the normalized resonant current when the switch is turned on, i * r,ZVS is the ZVS critical normalized resonant current, C oss is the output capacitance of the switch, t d is the dead time; Figure 4 Given the working modal distribution diagram of ZVS, it is concluded from observation and analysis that in the sub-resonance region (f s <f r ), the operating modes that can achieve ZVS are: OA1O, SOA1, SA1, SO and OSO modes. In the over-resonance region (f s >f r ), all working modes can achieve ZVS; 22) Determine all the working modes that can achieve ZCS. The condition for achieving ZCS is that the secondary current of the resonant cavity is discontinuous. All working modes with stage O can achieve ZCS. 23) Determine the working modes that can achieve both ZVS and ZCS. In the sub-resonance region, there are OA1O, SOA1, SO, and OSO modes. In the over-resonance region, there are B1OS and OS modes. Select the appropriate working mode for each working condition. For the pre-charging stage, the voltage gain and output current are small, and they are set in the B1OS and OS modes in the over-resonance region; For CC, CP and CV operating conditions, the voltage gain and current are relatively large, and they are set in the sub-resonant region. Figure 5 and Figure 6 The power-switching frequency operating mode distribution diagram including the charging trajectory is given. Figure 5 The output power and voltage gain are negatively correlated. Figure 6 The output power and voltage gain are positively correlated; the maximum output power p * o,max It needs to be less than the maximum feasible power p * max To simplify the calculation, we use the ZVS power boundary p * ZVS Instead of the maximum feasible power limit p * max , combined with the requirements of ZVS and ZCS, the appropriate modes for the three working conditions are Figure 4 SOA1, SO, OSO modes in .

[0055] 3. According to the working mode selection results, the transformer ratio n is designed. Since the pre-charging condition is set in the over-resonance region, and the CC, CP and CV conditions are set in the under-resonance region, the boundary working point T1 is set at the full resonance, and the transformer ratio n can be calculated as follows:

[0056] The maximum gain and minimum gain are calculated as follows:

[0057] 4. Establish the relationship between the effective value of the resonant current and the parameters of the resonant converter, and derive the constraint conditions for the parameter design of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions; 41a) According to the time domain model of the three-phase LLC resonant converter, the resonant current effective value I is established r,rms Relationship with resonant converter parameters:

[0058] Where M is the voltage gain, I o is the output current, f n = f s / f rTo normalize the switching frequency, since the time domain model cannot obtain an analytical solution, h is used to represent the existing functional relationship; 41b) For any given operating point P, the voltage gain M and output current I o is fixed, and according to the time domain model, the remaining three parameters have a relationship:

[0059] 41c) According to 41a) and 41b), for any determined operating point P, the effective value of the resonant current I r,rms,P Only k and f n related:

[0060] where h P Represents the effective value of the resonant current at the operating point P and the parameters k and f n Functional relationship of 41d) Figure 7 Plot f n The relative position of the operating point P in the gain-switching frequency plane and the trend diagram of the inductance ratio k when fixed. According to the trend diagram, the larger the k, the greater the ZVS margin (i * r0 / i * r,ZVS ) is larger, Figure 8 Plot f n The trend diagram of the resonant current effective value and ZVS margin at the fixed working point P, combined with Figure 7 and Figure 8 , the smaller k is, the smaller the ZVS margin of the working point P (i * r0 / i * r,ZVS ) is smaller, the smaller the effective value of the resonant current is.

[0061] 42a) The optimal condition for the effective value of the resonant current under all operating conditions is that the maximum output power p * o,max Equal to the ZVS power boundary p * ZVS Minimum value of:

[0062] where p * diff It is the difference between the minimum value of ZVS power boundary and the maximum output power; 42b) There are infinite parameters that satisfy the conditions in 42a), and the maximum gain M must be combined. max The working point Γ is used to determine the unique solution. The working point T3 is selected as the constraint, and its voltage gain is M max, while the switching frequency is the minimum under all operating conditions:

[0063] where k s and Z rs is the parameter solution, f n,T3 is the switching frequency of working condition T3; 42c) Combining 42a) and 42b), when the switching frequency f of the operating point T3 is n,T3 When fixed, the optimal parameter solutions k and Z for the effective value of the resonant current under all working conditions are r Can be obtained by n,T3 The effective value of the resonant current under all working conditions can be determined by the effective value of the resonant current I at the working point T3. r,rms,T3 To measure:

[0064] 5. Using the optimization method, under the premise of satisfying all parameter design constraints, solve the three-phase LLC resonant converter parameters with the optimal resonant current effective value under all working conditions. 51) Determine the minimum gain constraint, the constraint condition is, the maximum switching frequency f s,max The voltage gain at the output current is I o,min When the voltage gain is less than the minimum M min , Fig. 9 Given the switching frequency f s,max , the output current is I o,min The voltage gain and resonance parameters k and Z r The trend diagram shows that as k decreases and Z r As the voltage gain decreases, the minimum gain constraint is easier to achieve. In order to limit the working area to the B1OS mode as much as possible to achieve ZCS, such as Fig. 9 As shown, the gain of setting the limit value on the B1OS and B1S modal boundaries is exactly M min The corresponding constraint expression is:

[0065] 52) Perform optimal solution, the goal is to solve I r,rms,T3 The minimum value of , constrained by the minimum gain constraint in 51) and the given minimum switching frequency constraint, the solution expression is as follows:

[0066] All three constraints can be expressed as n,T3 Constraints, using the gradient descent method to solve the optimal solution corresponding to f n,T3 , then solve for k s and Z rs , the solution is as follows:

[0067] 53) According to 52), the switching frequency f of the operating point T3 is obtained. s,T3 , parameter k s and Z rs , by a given resonant frequency f r = 50 kHz, the resonant inductance L can be calculated r , resonant capacitor C r and the magnetizing inductance L m :

[0068] Fig.10 and Fig.11 The effective values ​​of resonant current and converter efficiency of the three design methods under CV and CP conditions were compared respectively, where the three methods are: Method 1, the method proposed in the present invention; Method 2, the method proposed in the present invention, but all of them are calculated using the FHA model; Method 3, the traditional FHA-based method. It can be seen that the effective values ​​of resonant current of the method proposed in the present invention are the smallest and the efficiency is the highest under all conditions, which proves the effectiveness of the proposed method.

[0069] In a second aspect, the present invention provides a three-phase LLC resonant converter parameter design system based on a time domain model, comprising: Determine the unit, which is used to determine the design requirements and operating condition distribution; A selection unit, configured to select feasible working modes for different working conditions based on the design requirements and working condition distribution and according to a time domain model of the three-phase LLC resonant converter; A design unit, used to design a transformer ratio according to a working mode selection result, and calculate a maximum gain and a minimum gain; An establishing unit is used to establish the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter according to the time domain model of the three-phase LLC resonant converter, and derive the constraint conditions of the parameter design of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all working conditions based on the maximum gain and the minimum gain; The optimization unit is used to solve the three-phase LLC resonant converter parameters with the optimal effective value of the resonant current under all working conditions by using an optimization method under the premise of satisfying all parameter design constraints.

[0070] The third object of the embodiment of the present invention is to provide an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the three-phase LLC resonant converter parameter design method based on the time domain model, and further comprising a communication interface and a bus.

[0071] A fourth objective of an embodiment of the present invention is to provide a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the three-phase LLC resonant converter parameter design method based on the time domain model is implemented.

[0072] A fifth objective of an embodiment of the present invention is to provide a computer program product, which includes computer instructions and is characterized in that the three-phase LLC resonant converter parameter design method based on the time domain model.

[0073] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0075] The present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, readable storage media, optical storage, etc.) containing computer-usable program codes.

[0076] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0077] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A three-phase LLC resonant converter parameter design method based on a time domain model, characterized in that: include: Determine design requirements and operating conditions distribution; Based on the design requirements and operating condition distribution, feasible operating modes are selected for different operating conditions according to the time domain model of the three-phase LLC resonant converter; According to the working mode selection results, the transformer ratio is designed, and the maximum gain and minimum gain are calculated; According to the time domain model of the three-phase LLC resonant converter, the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter is established, and the constraint conditions for the design of the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all working conditions are derived based on the maximum gain and minimum gain; Using the optimization method, the parameters of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all operating conditions are solved under the premise of satisfying all parameter design constraints.

2. A three-phase LLC resonant converter parameter design method based on a time domain model according to claim 1, characterized in that: The determining of design requirements and operating condition distribution includes: For the three-phase LLC resonant converter, L r is the resonant inductor, C r is the resonant capacitor, L m is the excitation inductance, n is the transformer ratio, f s is the switching frequency, the resonant frequency f r , inductance ratio k, characteristic impedance Z r as follows: Determine the design operating conditions and clarify the voltage gain and load characteristics under different operating conditions.

3. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 1, characterized in that: Based on the design requirements and the operating condition distribution, according to the time domain model of the three-phase LLC resonant converter, feasible operating modes are selected for different operating conditions, specifically including: 21) According to the ZVS conditions of the three-phase LLC resonant converter, all the working modes that can achieve ZVS are determined. The conditions for achieving ZVS are: where i * r0 is the normalized resonant current when the inverter switch is turned on, i * r,ZVS is the normalized critical resonant current for achieving ZVS, C oss is the output capacitance of the inverter switch, t d is the dead time; 22) According to the ZCS condition of the three-phase LLC resonant converter, determine all the working modes that can achieve ZCS. The condition for achieving ZCS is that the secondary current of the resonant cavity is discontinuous. 23) Among the working modes that can achieve both ZVS and ZCS, select appropriate working modes for different working conditions.

4. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 3, characterized in that: The determining of the working mode capable of realizing both ZVS and ZCS at the same time includes: There are four operating modes in the under-resonance region and two operating modes in the over-resonance region; According to the voltage gain and load characteristics of each working condition, the appropriate working mode is selected respectively; the over-resonance region is suitable for low voltage gain and light load conditions, and the under-resonance region is suitable for high voltage gain conditions.

5. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 3, characterized in that: The criteria for selecting the working mode are: on the one hand, the gain and load output requirements must be met; on the other hand, the maximum output power p * o,max Less than the maximum feasible power p * max To simplify the calculation, we use the ZVS power boundary p * ZVS Instead of the maximum feasible power p * max .

6. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 1, characterized in that: The transformer ratio is designed according to the working mode selection result, and the maximum gain and the minimum gain are calculated, including: According to the working mode selection results, the transformer ratio n is designed, and the transformer ratio n is calculated according to the boundary working point T1 of the over-resonance region and the under-resonance region as follows: The maximum gain and minimum gain are calculated as follows: 。 7. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 1, characterized in that: The method of establishing the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter according to the time domain model of the three-phase LLC resonant converter specifically includes: 41a) According to the time domain model of the three-phase LLC resonant converter, the resonant current effective value I is established r,rms Relationship with resonant converter parameters: Where M is the voltage gain, I o is the output current, f n = f s / f r To normalize the switching frequency, since the time domain model cannot obtain an analytical solution, h is used to represent the existing functional relationship; 41b) For any given operating point P, the voltage gain M and output current I o is fixed. According to the time domain model, the relationship between the remaining three parameters is: 41c) According to 41a) and 41b), for any determined operating point P, the effective value of the resonant current I r,rms,P With k and f n related: where h P Represents the effective value of the resonant current at the operating point P and the parameters k and f n Functional relationship of 41d) Plot f n The trend diagram of the resonant current effective value and inductance ratio k at the fixed working point P. According to the trend diagram, k and the ZVS margin (i * r0 / i * r,ZVS ) relationship.

8. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 1, characterized in that: The constraint conditions for the parameter design of the three-phase LLC resonant converter with the optimal resonant current effective value under all working conditions based on the maximum gain and the minimum gain specifically include: 42a) The optimal condition for the effective value of the resonant current under all operating conditions is that the maximum output power p * o,max Equal to the ZVS power boundary p * ZVS Minimum value of: where p * diff is the ZVS power boundary p * ZVS Minimum and maximum output power p * o,max difference; 42b) There are infinite parameters that satisfy the conditions in 42a), and the maximum gain M needs to be selected max The working point Γ is constrained to determine the unique solution: where k s and Z rs is the parameter solution, f n,Γ is the switching frequency of the operating point Γ; 42c) Combining 42a) and 42b), when the switching frequency f of the operating point Γ n,Γ When fixed, the optimal parameter solution k for the effective value of the resonant current under all working conditions s and Z rs Can be obtained by n,Γ The effective value of the resonant current under full working condition is determined by the effective value of the resonant current at the working point Γ. r,rms,Γ To measure: 。 9. The method for designing parameters of a three-phase LLC resonant converter based on a time domain model according to claim 1, characterized in that: The optimization method is used to solve the three-phase LLC resonant converter parameters with the optimal effective value of the resonant current under all working conditions under the premise of satisfying all parameter design constraints, including 51) Determine the minimum gain constraint, the constraint condition is, the maximum switching frequency f s,max The voltage gain at the output current is I o,min When the voltage gain is less than the minimum M min , the corresponding constraint expression is: 52) Perform optimal solution, the goal is to solve I r,rms,Γ The minimum value of , constrained by the minimum gain constraint in 51) and the given minimum switching frequency constraint, the solution expression is as follows: 53) According to 52), the switching frequency f of the operating point Γ is obtained. n,Γ , parameter k s and Z rs , by a given resonant frequency f r , calculate the resonant inductance L r , resonant capacitor C r and the magnetizing inductance L m : 。 10. A three-phase LLC resonant converter parameter design system based on a time domain model, characterized in that: include: Determine the unit, which is used to determine the design requirements and operating condition distribution; A selection unit, configured to select feasible working modes for different working conditions based on the design requirements and working condition distribution and according to a time domain model of the three-phase LLC resonant converter; A design unit, used to design a transformer ratio according to a working mode selection result, and calculate a maximum gain and a minimum gain; An establishing unit is used to establish the relationship between the effective value of the resonant current and the parameters of the three-phase LLC resonant converter according to the time domain model of the three-phase LLC resonant converter, and derive the constraint conditions of the parameter design of the three-phase LLC resonant converter with the optimal effective value of the resonant current under all working conditions based on the maximum gain and the minimum gain; The optimization unit is used to solve the three-phase LLC resonant converter parameters with the optimal effective value of the resonant current under all working conditions by using an optimization method under the premise of satisfying all parameter design constraints.

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