Series resonant dual active bridge reflow power optimization control method and system

Abstract

The application discloses a series resonant dual active bridge backflow power optimization control method and system, the method establishes a series resonant dual active bridge theoretical model, and obtains a current expression at a switching time by solving, and further calculates a feasible region of an inner and outer phase shift ratio according to a soft switching condition of the dual active bridge, and obtains a critical curve of the inner and outer phase shift ratio satisfying the soft switching condition through curve fitting; the inner and outer phase shift ratio is selected on the curve and a certain soft switching margin is ensured, so that the current at the switching time is small enough, and then the operation efficiency of the dual active bridge is improved; the application has low real-time calculation amount, and in actual application, only fine adjustment is needed near the theoretical curve, so that the backflow power can be effectively reduced, and the transmission efficiency is improved.

Description

TECHNICAL FIELD

[0001] The application relates to a backflow power optimization control method and system, in particular to a series resonant dual active bridge backflow power optimization control method and system. BACKGROUND

[0002] The dual active bridge (DAB) has the advantages of flexible voltage variation, electrical isolation, bidirectional energy transmission, simple control and the like, and is the most common topology in a direct-current transformer. At present, single phase shift control (SPS) is the most common control method for the DAB topology, but backflow power is inevitably generated in the transmission process. Therefore, some scholars have proposed methods such as extended phase shift (EPS), double phase shift (DPS) and triple phase shift (TPS) to attempt to optimize the backflow power. However, the more the control degrees of freedom are increased, the more complex the calculation and control are. Therefore, at present, only EPS has been well applied.

[0003] The series resonant dual active bridge (SRDAB) adds a resonant link on the basis of the original DAB topology, so that the switching loss is further reduced. However, due to the change in the circuit structure, the existing EPS control method is no longer applicable. Meanwhile, in the prior art, the method for eliminating backflow power by adjusting the pulse width and frequency, using fixed waveform pulse width or fixed waveform frequency modulation at different frequencies has a large amount of calculation and complex control. SUMMARY

[0004] The application aims to provide a series resonant dual active bridge backflow power optimization control method with small real-time calculation amount and simple control, and a second application aims to provide a series resonant dual active bridge backflow power optimization control method with small real-time calculation amount and simple control.

[0005] The series resonant dual active bridge backflow power optimization control method comprises the following steps: obtaining the optimal D1 and D2 values that satisfy the soft switching condition by taking the values of D1 and D2 on the relationship line of the inner phase shift ratio D1 and the outer phase shift ratio D2, and the calculation method of the relationship line of D1 and D2 is as follows:

[0006] The voltage and current equations of the simplified circuit of the series resonant dual active bridge are established.

[0007] The voltage and current equations are established according to three time periods divided by rising edges or falling edges of switch on and off, i.e., (0, t1), (t1, t2) and (t2, t3), and the voltage and current in the three time periods are solved respectively; wherein t1=D1T, t2=(D1+D2)T, t3=T, T is a half switch period; a primary side of the series resonant dual active bridge includes switch tubes S1-S4, a secondary side includes switch tubes Q1-Q4, S4 leads S1 to be turned on for a time of D1T, and S1 leads Q1 to be turned on for a time of D2T;

[0008] D1 and D2 are changed in a feasible region at equal steps, values of i(t1) and i(t2) in the feasible region are solved, a boundary line of i(t1) in the feasible region satisfying a soft switch condition is obtained, i(t2) in the feasible region all satisfies the soft switch condition, and the boundary line is fitted to obtain a relationship line of the D1 and D2.

[0009] Further, the voltage and current equations are established according to three time periods divided by rising edges or falling edges of switch on and off, i.e., (0, t1), (t1, t2) and (t2, t3), and the voltage and current in the three time periods are solved respectively, and the voltage and current in the three time periods are solved respectively.

[0010] The voltage and current equations in the three time periods are as follows:

[0011]

[0012] Further, the voltage and current in the three time periods are as follows:

[0013]

[0014]

[0015] Wherein, expressions of alpha and beta are as follows:

[0016]

[0017] U r1 ~ U r3 , i r1 ~ i r3 respectively represent voltages and currents of capacitors C r in the three time periods, C1-C6 are undetermined coefficients, L r is an inductance value, C r is a capacitance value, d=u1 / u2, R is an equivalent internal resistance, u1 and u2 are direct voltages of the primary side and the secondary side respectively.

[0018] Further, the undetermined coefficients C1-C6 are solved according to periodicity of the voltage and current.

[0019] Further, the relationship line of the D1 and D2 is a straight line.

[0020] Further, the optimal D1 and D2 values satisfying the soft switching condition are obtained by taking D1 and D2 values on the relationship line of the inner shift phase ratio D1 and the outer shift phase ratio D2 and adding a margin.

[0021] Further, the voltage and current equation of the series resonant dual active bridge simplified circuit is:

[0022]

[0023] Under different conduction conditions, u AB and u CD have the following values:

[0024]

[0025]

[0026] The series resonant dual active bridge backflow power optimization control system provided by the application comprises:

[0027] The simplified circuit equation establishing module is used to establish the voltage and current equation of the series resonant dual active bridge simplified circuit.

[0028] The segmented equation establishing module is used to divide the voltage and current equation into three time periods (0, t1), (t1, t2) and (t2, t3) according to the rising edge or falling edge of switch conduction and turn-off, and solve the voltage and current in the three time periods, wherein t1=D1T, t2=(D1+D2)T, t3=T, T is a half switch period; the primary side of the series resonant dual active bridge comprises switch tubes S1-S4, and the secondary side comprises switch tubes Q1-Q4, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T.

[0029] The optimal shift phase ratio solving module is used to change D1 and D2 in the feasible region at equal steps, solve the values of i(t1) and i(t2) in the feasible region, obtain the boundary line of i(t1) in the feasible region satisfying the soft switching condition, i(t2) in the feasible region all satisfy the soft switching condition, fit the boundary line to obtain the relationship line of D1 and D2; and take D1 and D2 values on the relationship line of the inner shift phase ratio D1 and the outer shift phase ratio D2 to obtain the optimal D1 and D2 values satisfying the soft switching condition.

[0030] The electronic device comprises a memory, a processor, and a computer program stored in the memory and capable of running on the processor, and the computer program realizes the series resonance dual active bridge backflow power optimization control method when loaded to the processor.

[0031] The computer readable storage medium stores a computer program, and the computer program realizes the series resonance dual active bridge backflow power optimization control method when executed by the processor.

[0032] Advantages: compared with the prior art, the advantages of the present application are that (1) the backflow power can be effectively reduced, the turn-off loss can be reduced, and the transmission efficiency can be improved; (2) when the backflow power optimization control is actually performed, only fine tuning near the theoretical curve is needed, the calculation amount is small, and the control is simple and convenient. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a series resonance dual active bridge circuit diagram in the embodiment of the present application.

[0034] Figure 2 It is a simplified circuit diagram of the series resonance dual active bridge in the embodiment of the present application.

[0035] Figure 3 It is a modulation pulse and voltage and current waveform diagram of the series resonance dual active bridge in the embodiment of the present application.

[0036] Figure 4 It is a current three-dimensional diagram at t1 in the embodiment of the present application.

[0037] Figure 5 It is a current three-dimensional diagram at t2 in the embodiment of the present application.

[0038] Figure 6 It is a soft switch boundary search flow chart in the embodiment of the present application.

[0039] Figure 7 It is a soft switch boundary fitting curve diagram in the embodiment of the present application. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be further described below with reference to the drawings.

[0041] The series resonance dual active bridge backflow power optimization control method comprises three steps of circuit modeling, equation solving, and linear fitting.

[0042] Step 1, circuit modeling

[0043] The SRDAB topology is as follows Figure 1As shown, the circuit is composed of two full-bridge circuits, an isolation transformer, a series resonant unit, a DC bus, etc., wherein the full-bridge circuit is composed of switch tubes S1-S4, Q1-Q4 and their anti-parallel diodes, and can transform the DC voltage of the primary and secondary sides into a high-frequency square wave. The series resonant unit can be equivalent to an inductor and a capacitor in series. Thus Figure 1 The circuit shown can be simplified as Figure 2 The circuit shown, according to Figure 2 The following equation can be established:

[0044]

[0045] In the formula, L r is the inductance value, C r is the capacitance value, i r is the current in the circuit, U r is the capacitor voltage, U R is the equivalent internal resistance voltage, u AB is the voltage between points A and B of the primary side, and u CD is the voltage between points C and D of the secondary side. Under different conduction conditions, u AB , u CD have the following values:

[0046]

[0047] In the formula, u1 and u2 are the DC voltages of the primary and secondary sides, respectively.

[0048] According to the rising edge or falling edge of the switch conduction and turn-off, the time is divided into several parts, as shown in Figure 3 D1 is defined as the inner phase shift ratio, D2 is defined as the outer phase shift ratio, T is the half switch period, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T. Assuming that S4 is turned on at time 0, then t1=D1T, t2=(D1+D2)T, and t3=T. According to Figure 3 The following equation can be established:

[0049]

[0050] In the formula, d=u1 / u2, and R is the equivalent internal resistance. The voltage and current equations are solved as follows:

[0051]

[0052]

[0053] In the formula, U r1 ~U r3 , i r1 ~i r3 represent the capacitor C rThe voltage and current, C1~C6 are undetermined coefficients. The expressions of α and β are as follows

[0054]

[0055] Step 2, equation solving

[0056] According to the periodicity of the voltage and current:

[0057]

[0058] Thus, the following equation is obtained:

[0059]

[0060] Solving the above equation set, the coefficients C1~C6 are obtained, and C1~C6 are brought back to the current equation to obtain the analytical expression of the SRDAB current.

[0061] Let D1 and D2 change in equal steps in the feasible region, 0≤D1≤1, 0≤D2≤1, 0≤D1+D2≤1, and the values of i(t1) and i(t2) in the feasible region are calculated, as shown in Figure 4 and Figure 5 According to the soft switching condition of the EPS DAB

[0062]

[0063] It can be seen that i(t2) in the feasible region satisfies the full switching condition, and i(t1) in the feasible region exists a boundary line, as shown by the black curve in Figure 4 When D1≤kD2+b, the soft switching condition is satisfied.

[0064] Step 3, linear fitting

[0065] The values of D1 and D2 on the boundary curve are obtained by traversing the feasible region, and two one-dimensional vectors are obtained. The relationship line expression is obtained by linear fitting of the curve with D2 as the x-axis and D1 as the y-axis. Finally, the values of the two are adjusted synchronously in the closed-loop control and a certain margin is added to achieve the purpose of optimal soft switching, and the search process is shown in Figure 6 .

[0066] For the series resonant DAB topology shown in Figure 1 S1~S4, Q1~Q4 are IGBTs of the same type. In this embodiment, the values of the coefficients C1~C6 obtained are-1314.49, -3452.50, -1973.57, -3816.28, -2600.21, and-2428.80.

[0067] Thus, the time-domain expression of the current is:

[0068]

[0069] Because t1=D1T, t2=(D1+D2)T, the current segment function is brought into formula (10) to obtain the relationship line expression of D1D2, that is, D1=1.614D2-0.023, and the fitting curve is as shown in the figure. Figure 7

[0070] The series resonant dual active bridge backflow power optimization control system comprises:

[0071] The simplified circuit equation establishing module is used for establishing the voltage and current equations of the simplified circuit of the series resonant dual active bridge.

[0072] The segment equation establishing module is used for dividing into three time periods according to the rising edges or falling edges of the switch on and off to establish the voltage and current equations, that is, (0, t1), (t1, t2) and (t2, t3), and the voltage and current in the three time periods are solved respectively; wherein t1=D1T, t2=(D1+D2)T, t3=T, T is a half switch period; the original side of the series resonant dual active bridge comprises switch tubes S1-S4, and the secondary side comprises switch tubes Q1-Q4, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T.

[0073] The optimal phase shift ratio solving module is used for changing D1 and D2 in the feasible domain at equal steps, solving the values of i(t1) and i(t2) in the feasible domain, obtaining the boundary line of i(t1) in the feasible domain satisfying the soft switch condition, i(t2) in the feasible domain all satisfying the soft switch condition, and fitting the boundary line to obtain the relationship line of D1 and D2; the values of D1 and D2 are taken on the relationship line of the inner phase shift ratio D1 and the outer phase shift ratio D2, and the optimal D1 and D2 values satisfying the soft switch condition are obtained.

[0074] The electronic device comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, and the computer program realizes the series resonant dual active bridge backflow power optimization control method when being loaded to the processor.

[0075] The computer readable storage medium stores a computer program, and the computer program realizes the series resonant dual active bridge backflow power optimization control method when being executed by the processor.

[0076] The computer readable storage medium can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory or any other medium that can be used to store desired program codes in the form of instructions or data structures and can be accessed by a computer.​

[0077] The processor is configured to execute the computer program stored in the memory to implement the various steps in the methods involved in the above-described embodiments.

Claims

1. A method for series resonant dual active bridge (DAB) reverse power optimization control, characterized in that, D1 and D2 are taken on a relationship line of inner shift phase ratio D1 and outer shift phase ratio D2, and optimal D1 and D2 values satisfying the soft switching condition are obtained; the calculation method of the relationship line of D1 and D2 is as follows: A voltage and current equation of the series resonant dual active bridge simplified circuit is established; The voltage and current equation is established according to three time periods divided by rising edges or falling edges of switch-on and switch-off, i.e., (0, t1), (t1, t2) and (t2, t3), and the voltage and current in the three time periods are solved respectively; wherein t1=D1T, t2=(D1+D2)T, t3=T, and T is a half switch period; the primary side of the series resonant dual active bridge includes switch tubes S1-S4, and the secondary side includes switch tubes Q1-Q4, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T; D1 and D2 are changed in the feasible region at equal steps, the values of i(t1) and i(t2) in the feasible region are solved, a boundary line of i(t1) in the feasible region satisfying the soft switching condition is obtained, i(t2) in the feasible region satisfies the soft switching condition, and the boundary line is fitted to obtain the relationship line of D1 and D2; The voltage and current equation of the series resonant dual active bridge simplified circuit is as follows: where L r is the inductance value, C r is the capacitance value, i r is the current in the circuit, U r is the capacitor voltage, U R is the equivalent internal resistance voltage, under different conduction conditions, u AB and u CD have the following values: Wherein u1 and u2 are direct current voltages of the primary side and the secondary side respectively.

2. The series resonant dual active bridge flyback power optimization control method of claim 1, wherein, The voltage and current equation is established according to three time periods divided by rising edges or falling edges of switch-on and switch-off, i.e., (0, t1), (t1, t2) and (t2, t3), and the voltage and current in the three time periods are solved respectively; wherein t1=D1T, t2=(D1+D2)T, t3=T, and T is a half switch period; the primary side of the series resonant dual active bridge includes switch tubes S1-S4, and the secondary side includes switch tubes Q1-Q4, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T; The voltage and current in the three time periods are as follows: where L r is the inductance value, C r is the capacitance value, U r is the capacitor voltage, d = u1 / u2, R is the equivalent internal resistance, u1 and u2 are the DC voltages of the primary and secondary sides, respectively.

3. The series resonant dual active bridge flyback power optimization control method of claim 2, wherein, Wherein α and β expressions are as follows: The undetermined coefficients C1-C6 are solved according to the periodicity of the voltage and current. U r1 ~U r3 , i r1 ~i r3 represent the voltage and current of the capacitor C r in three time periods respectively, C1~C6 are undetermined coefficients, L r is the inductance value, C r is the capacitance value, d=u1 / u2, R is the equivalent internal resistance, u1 and u2 are the direct current voltages of the primary side and the secondary side respectively.

4. The series resonant dual active bridge flyback power optimization control method of claim 3, wherein, The relationship line of D1 and D2 is a straight line.

5. The series resonant dual active bridge flyback power optimization control method of claim 1, wherein, D1 and D2 are taken on a relationship line of inner shift phase ratio D1 and outer shift phase ratio D2, and optimal D1 and D2 values satisfying the soft switching condition are obtained; the calculation method of the relationship line of D1 and D2 is as follows:

6. The series resonant dual active bridge flyback power optimization control method of claim 1, wherein, It comprises:

7. A series resonant dual active bridge flyback power optimization control system, characterized in that, A simplified circuit equation establishing module is configured to establish a voltage and current equation of a series resonant dual active bridge simplified circuit; A segmented equation establishing module is configured to establish a voltage and current equation according to three time periods divided by rising edges or falling edges of switch-on and switch-off, i.e., (0, t1), (t1, t2) and (t2, t3), and solve the voltage and current in the three time periods respectively; wherein t1=D1T, t2=(D1+D2)T, t3=T, and T is a half switch period; the primary side of the series resonant dual active bridge includes switch tubes S1-S4, and the secondary side includes switch tubes Q1-Q4, the S4 leading S1 conduction time is D1T, and the S1 leading Q1 conduction time is D2T; ​ The optimal phase shift ratio solving module is configured to change D1 and D2 in the feasible region at equal steps, solve the values of i(t1) and i(t2) in the feasible region, obtain a boundary line of i(t1) in the feasible region that satisfies the soft switching condition, i(t2) in the feasible region that satisfies the soft switching condition, and fit the boundary line to obtain the relationship line of D1 and D2; and obtain the optimal D1 and D2 values that satisfy the soft switching condition by taking the values of D1 and D2 on the relationship line of the inner phase shift ratio D1 and the outer phase shift ratio D2. The voltage and current equation of the series resonant dual active bridge simplified circuit is: where L r is the inductance value, C r is the capacitance value, i r is the current in the circuit, U r is the capacitor voltage, U R is the equivalent internal resistance voltage, under different conduction conditions, u AB and u CD have the following values: Wherein, u1 and u2 are the direct current voltages of the primary side and the secondary side respectively.

8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The computer program is loaded into the processor to implement the series resonant dual active bridge return flow power optimization control method according to any one of claims 1-6.

9. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8. The computer program is executed by the processor to implement the series resonant dual active bridge return flow power optimization control method according to any one of claims 1-6.

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