Modulation and control method of bridge arm multiplexing type FSBB-CLLLC bidirectional converter

Abstract

The invention provides a modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter, belongs to the technical field of power electronics, and solves the problems that the modulation method of the bridge arm multiplexing type FSBB-CLLLC converter is not clear, the working principle is not clear, and the efficiency is reduced due to the fact that soft switching implementation is complex. The main circuit topology is divided into different bridge arms; different working modes of the converter during forward and reverse operation are researched by combining a bridge arm phase shift angle and a duty ratio; researching and solving the relationship between the inductive current and the phase shift angle of the converter by combining a modulation method and a soft switching condition, and establishing a three-dimensional table; according to different input and output voltage requirements, the duty ratio is determined, the optimal phase shift angle is determined after table look-up, and full-switching tube soft switching of the FSBB-CLLLC converter under voltage stabilization control is achieved.

Description

Technical Field

[0001] The invention relates to a modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter, belonging to the technical field of power electronics. Background Art

[0002] With the rapid development of new energy technologies, electric vehicles, DC microgrids and distributed energy storage systems are gradually becoming the focus of research in the field of new energy technologies. Most of the above-mentioned fields require the realization of bidirectional energy transmission, and the bidirectional transmission of electric energy usually requires the use of bidirectional isolated DC / DC converters (IBDC) to achieve this. However, the above-mentioned technologies all require the use of supercapacitors or battery packs to achieve energy storage, and the current high-voltage battery packs of electric vehicles basically adopt the form of multiple low-voltage lithium batteries in series and parallel. The charging process is divided into pre-charging, constant voltage charging, constant current charging and other stages. The battery voltage will vary over a large range during the whole process. The lower limit of the voltage of a deeply discharged lithium battery is only 0.27 times the nominal voltage, while the voltage can reach 1.13 times the nominal voltage after full charging, and the maximum and minimum voltage ratio is 4.18. Therefore, in order to cover the voltage range of lithium batteries, this requires the bidirectional DC / DC converter to have a wide bidirectional voltage regulation range.

[0003] Among many IBDC converters, the bridge arm multiplexing FSBB-CLLLC converter (Integrated Buck-Boost CLLLC Convertor, IBBCLLLC) cascades the CLLLC converter and the FSBB converter, uses the FSBB converter as the front stage of the CLLLC, broadens the voltage regulation range of the CLLLC converter, and retains the ZVS-ON of the primary side and the ZCS-OFF characteristics of the secondary side of the CLLLC converter, which has good application prospects. Therefore, the present invention studies the modulation method of the bridge arm multiplexing FSBB-CLLLC converter and provides a corresponding control method. Summary of the invention

[0004] The present invention aims to solve the problems of unclear modulation method, unclear working principle and reduced efficiency of bridge arm multiplexing type FSBB-CLLLC converter, and further proposes a modulation and control method of bridge arm multiplexing type FSBB-CLLLC bidirectional converter.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problem is: the steps of the present invention include:

[0006] Step 1: Based on the bridge arm multiplexing type FSBB-CLLLC bidirectional converter, the main circuit topology is divided into different bridge arms;

[0007] Step 2: Obtain different operating modes of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in forward and reverse operation based on the bridge arm phase shift angle α and duty cycle D, where the bridge arm phase shift angle α is the phase angle between the front bridge arm of FSBB and the multiplexing bridge arm, and the duty cycle D is the duty cycle of the upper switch tube S1 in the front bridge arm of FSBB;

[0008] Step 3: Based on the different working modes of the bridge arm multiplexed FSBB-CLLLC bidirectional converter during forward and reverse operation, solve the soft switching conditions of the corresponding working mode;

[0009] Step 4: Solve the different inductor currents i of the bridge arm multiplexing FSBB-CLLLC bidirectional converter based on the modulation method of the bridge arm multiplexing FSBB-CLLLC bidirectional converter and the soft switching conditions L The corresponding phase shift angles are calculated and a three-dimensional table is constructed;

[0010] Step 5: Determine the duty cycle D according to different input and output voltage requirements, input the duty cycle D, input voltage, input current, output current and output voltage into a three-dimensional table, query and obtain the optimal phase shift angle α, and control the bridge arm multiplexing FSBB-CLLLC converter to be in the optimal working mode.

[0011] Preferably, the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in step 1 includes a DC power supply, a load, FSBB front bridge arm switch tubes S1 and S2, multiplexed bridge arm switch tubes S3 and S4, CLLLC primary side switch tubes Q5 and Q6, CLLLC secondary side first bridge arm switch tubes Q7 and Q8, CLLLC secondary side second bridge arm switch tubes Q9 and Q10. 10 , FSBB inductor L, CLLLC primary and secondary resonant inductor L r1 , L r2 , CLLLC original secondary side resonant capacitor C r1 , C r2 , with magnetizing inductance L m Transformer T, input and output filter capacitors C in , C o and bus capacitance C bus , input voltage V in and output voltage V.

[0012] Preferably, the bus capacitor C bus The output port is connected to the FSBB-level and CLLLC-level converters. The reused bridge arm switches S3 and S4 are the rear bridge arm switches of the FSBB-level and the primary inverter bridge arm switches of the CLLLC-level. The primary resonant inductor L r1 With the primary side resonant capacitor C r1 The series resonant frequency is f r , the secondary resonant inductor L of the CLLLC stager2 With the secondary side resonant capacitor C r2 The series resonant frequency is f r , the CLLLC-level converter works at the resonance point, the DC gain is fixed to 1, and the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is calculated based on the duty cycle D;

[0013] The calculation formula of the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is:

[0014]

[0015] Preferably, when the multiplexed FSBB-CLLLC bidirectional converter in step 2 is in forward operation, the input voltage V in After FSBB stage, the voltage is pre-stepped down to V bus , through the CLLLC stage fixed gain output voltage V o , and introduce the phase angle α between the rising edges of the S1 and S3 drive signals, and achieve full switch soft switching by adjusting the phase angle α.

[0016] Preferably, when the multiplexed FSBB-CLLLC bidirectional converter in step 2 is in reverse operation, the input voltage V in Isolate the output to V through CLLLC stage bus , the voltage is adjusted to the required output voltage V by the FSBB stage o , the switch tubes S3~S4 and Q5~Q6 become a rectification network, working in the synchronous rectification mode, and realize soft switching of all switch tubes by adjusting the phase angle α.

[0017] Preferably, the different operating modes of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in forward and reverse operation in step 2 specifically include:

[0018] Step 2.1: Taking the rising edge of the S3 driving signal as the reference, define the phase angle between the rising edge of S3 and the rising edge of S1 as α. When S1 is ahead of S3, α>0, and when S1 lags behind S3, α<0. D is the duty cycle of the FSBB front bridge arm switch tube S1.

[0019] Step 2.2: When the bridge arm multiplexing type FSBB-CLLLC bidirectional converter is in forward operation, when 0<-α<0.5 and 0.5<-α+D<1, S1 is turned on during the conduction period of S3 and is turned off during the conduction period of S4, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modef2; when 0<α<0.5 and 0.5<α+D<1, S1 is turned on during the conduction period of S4 and is turned off during the conduction period of S3, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modef5;

[0020] Step 2.3: When the bridge arm multiplexing type FSBB-CLLLC bidirectional converter operates in reverse, when 0<-α<0.5, 0.5<-α+D<1, S1 is turned on during the conduction period of S3 and is turned off during the conduction period of S4, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modeb2; when 0<α<0.5, 0.5<α+D<1, S1 is turned on during the conduction period of S4 and is turned off during the conduction period of S3, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modeb5.

[0021] Preferably, the step of solving the soft switching condition in step 3 includes:

[0022] Step 3.1: Calculate the FSBB stage inductor current i L Piecewise expressions for all phases in the operating mode cycle;

[0023] Step 3.2: When S1 is turned on and the duty cycle and phase shift angle are confirmed, the input power is transmitted to the inductor L of FSBB, and the input power P is calculated. in Expression of

[0024] Step 3.3: Set the converter's transmission efficiency to η and calculate the inductor current i according to the power conservation law. L The expression of the initial value -I0;

[0025] Step 3.4: Calculate the boundary conditions for the switch tubes S1~S4 and Q5~Q6 to achieve soft switching;

[0026] Step 3.5: Combine the FSBB-level inductor current i L The piecewise expressions for all phases in the operating mode cycle, the inductor current i L The initial value -I0 expression and the switch tubes S1~S4, Q5~Q6 can all realize the boundary conditions of soft switching to calculate the optimal phase shift angle α under the current working mode;

[0027] FSBB level inductor current i L The piecewise expressions for all phases in the working mode cycle are:

[0028]

[0029] In formula (2), -I0 is the inductor current i L The initial values ​​of t1, t2, t3, T s It is the time segment within the working mode cycle;

[0030] Input power P in The expression is:

[0031]

[0032] In formula (3), S a and S b is the inductor current i L The area enclosed by the t-axis;

[0033] Inductor current i L The expression of the initial value -I0 is:

[0034]

[0035] The boundary conditions for the switch tubes S1~S4 and Q5~Q6 to achieve soft switching are as follows:

[0036]

[0037] Preferably, constructing the three-dimensional table in step 3 specifically includes:

[0038] According to the boundary conditions that the switch tubes S1-S4 and Q5-Q6 can realize soft switching, a three-dimensional table of power, duty cycle and phase shift angle α is drawn.

[0039] Preferably, the modulation method of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in step 4 specifically includes:

[0040] The FSBB-level front bridge arm switch tube adopts PWM modulation, the duty cycle of S1 is D, S2 and S1 are complementary, and the CLLLC-level front bridge arm switch tubes Q5 and Q6 and the reused bridge arm switch tubes S3 and S4 form an inverter network with a fixed duty cycle of 50% and a fixed switching frequency f r Alternating conduction.

[0041] Preferably, when controlling the bridge arm multiplexed FSBB-CLLLC converter in step 5, the output voltage is first sampled, and the output voltage is controlled by PI control of the duty cycle D, and then the duty cycle D and the output power are input into a three-dimensional table to query the optimal phase shift angle α to achieve soft switching.

[0042] The beneficial effects of the present invention are:

[0043] 1. The multiplexed converter in the present invention adopts a bridge arm multiplexing structure, which effectively reduces the cost, and the multiplexed bridge arm is more conducive to realizing soft switching, thereby improving efficiency.

[0044] 2. The phase-shift modulation strategy proposed in the present invention is applicable to the forward and reverse operation of the FSBB-CLLLC converter, and can enable the converter to operate in different modes and switch smoothly according to different working conditions.

[0045] 3. The modulation method proposed in the present invention not only broadens the bidirectional gain range of the converter, but also helps to realize soft switching of all switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A circuit topology diagram of the bridge arm multiplexing type FSBB-CLLLC converter provided by the present invention;

[0047] Figure 2 A flow chart of a modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter provided by the present invention;

[0048] Figure 3 A forward phase-shift modulation working mode diagram of the bridge arm multiplexing type FSBB-CLLLC converter provided by the present invention;

[0049] Figure 4 A diagram showing a reverse operation phase-shift modulation working mode of the bridge arm multiplexing type FSBB-CLLLC converter provided by the present invention;

[0050] Figure 5 The waveform diagram of the working mode Modef5 provided by the present invention;

[0051] Figure 6 A schematic diagram of soft switching boundary conditions of the FSBB-CLLLC converter provided by the present invention;

[0052] Figure 7 This is a control block diagram of the bridge arm multiplexing type FSBB-CLLLC converter provided by the present invention. DETAILED DESCRIPTION

[0053] Combination Figure 1-7 To illustrate this embodiment, Figure 2 As shown, the steps of the modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter described in this embodiment include:

[0054] S1: Combined with the bridge arm multiplexing type FSBB-CLLLC bidirectional converter, the main circuit topology is divided into different bridge arms;

[0055] like Figure 1 As shown, the bridge arm multiplexing type FSBB-CLLLC bidirectional converter includes a DC power supply, a load, FSBB front bridge arm switch tubes S1 and S2, multiplexing bridge arm switch tubes S3 and S4, CLLLC primary side switch tubes Q5 and Q6, CLLLC secondary side first bridge arm switch tubes Q7 and Q8, CLLLC secondary side second bridge arm switch tubes Q9 and Q 10 , FSBB inductor L, CLLLC primary and secondary resonant inductor L r1 , L r2 , CLLLC original secondary side resonant capacitor Cr1 , C r2 , with magnetizing inductance L m Transformer T, input and output filter capacitors C in , C o , bus capacitance C bus , where bus capacitance C bus Connecting the FSBB-level and CLLLC-level converters, it can be used as a separate output port. The reused bridge arm switches S3 and S4 not only serve as the rear bridge arm switches of the FSBB-level, but also play the role of the primary inverter bridge arm switches of the CLLLC-level. The primary resonant inductor L r1 With the primary side resonant capacitor C r1 The series resonant frequency is f r , and the series resonant frequency of the secondary resonant inductor and resonant capacitor is also f r .

[0056] For the bridge arm multiplexing type FSBB-CLLLC bidirectional converter, the CLLLC-level converter operates at the resonance point, the DC gain is fixed to 1, and the FSBB-level converter gain depends on the duty cycle D, so the total gain of the FSBB-CLLLC converter is G.

[0057] The calculation formula of the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is:

[0058]

[0059] S2: Combine the bridge arm phase shift angle and duty cycle to study the different working modes of the converter during forward and reverse operation;

[0060] S201: When the FSBB-CLLLC converter is running in the forward direction, the input voltage V in After FSBB stage, the voltage is pre-stepped down to V bus , and then passes through the CLLLC stage to output the voltage V with a fixed gain o At the same time, the phase angle α between the rising edges of the S1 and S3 driving signals is introduced, and the soft switching of the full switch tube is achieved by adjusting the phase angle α.

[0061] S202: When the FSBB-CLLLC converter operates in reverse, the input voltage V in Isolate the output to V through CLLLC stage bus , and then the voltage is adjusted to the required voltage output V by the FSBB stage o , which is different from the forward operation, at this time the switch tubes S3~S4 and Q5~Q6 become a rectification network, and because of the use of a bridge arm multiplexing structure, it needs to work in a synchronous rectification mode.

[0062] S203: Taking the rising edge of the S3 driving signal as the reference, define the phase angle between the rising edge of S3 and the rising edge of S1 as α. When S1 is ahead of S3, α>0; when S1 lags behind S3, α<0. When the FSBB-CLLLC converter is running in the forward direction, considering the duty cycle D and phase angle α of S1, the various working modes corresponding to the phase shift modulation mode of the FSBB-CLLLC stage are as follows: Figure 3 As shown, Figure 3 The driving signals of S1 to S4 in different modes and the current i flowing through the inductor L are given in L。

[0063] S20301: When 0<-α<0.5, S1 is turned on during the conduction period of S3. According to the turn-off time of S1, three working modes of FSBB-CLLLC can be obtained: Modef1-modef3. If -α+D<0.5, S1 is turned on and off during the conduction period of S3, and the mode is defined as Modef1; if 0.5<-α+D<1, S1 is turned off during the conduction period of S4, and the mode is defined as Modef2; if -α+D>1, S1 is turned off during the conduction period of S3 in the next cycle, and the mode is defined as Modef3;

[0064] S20302: When 0<α<0.5, S1 is turned on during the conduction period of S4. According to the off time of S1, three working modes of FSBB-CLLLC can be obtained: Modef4-modef6;

[0065] right Figure 3 Analysis shows that in the four modes of Modef1, Modef3, Modef4 and Modef6, the FSBB stage can only work in boost or buck mode and cannot meet a wider gain range. Therefore, the FSBB-CLLLC converter in this embodiment will not adopt these four working modes.

[0066] When the FSBB-CLLLC converter operates in reverse, the phase shift modulation method of the FSBB-CLLLC stage corresponds to various operating modes such as Figure 4 As shown, similar to the forward operation, the four modes Modeb1, Modeb3, Modeb4 and Modeb6 are not suitable for FSBB level control, while Modeb5 and Modef2 have the same inductor current waveform and belong to the same mode, while Modeb2 and Modef5 have the same inductor current waveform and can also be classified as one mode, which is suitable for FSBB level control.

[0067] S3: Combine the modulation method and soft switching conditions to study and solve the relationship between the inductor current and the phase shift angle of the converter, and establish a three-dimensional table;

[0068] In the FSBB-CLLLC converter, the switches S1 and S4 need to be in floating-point flow to achieve ZVS-ON, and the current waveform of the inductor L is controlled by the duty cycle D and the phase shift angle α, where D is determined by the DC gain of the converter, and adjusting the phase shift angle α can achieve soft switching of the FSBB-level switches. The CLLLC-level converter itself can achieve soft switching of all switches, so the FSBB-CLLLC converter can achieve soft switching of all switches.

[0069] S301: For different DC gain and power conditions, different phase shift angles α are required to achieve soft switching. This implementation takes the Modef5 mode during forward operation as an example. The waveform of the Modef5 mode is as follows: Figure 5 As shown, solving the soft switching conditions includes:

[0070] S30101: Calculation of FSBB-level inductor current i L Piecewise expressions for all phases in the operating mode cycle;

[0071]

[0072] In formula (2), -I0 is the inductor current i L The initial value of

[0073] S30102: When S1 is turned on and the duty cycle and phase shift angle are confirmed, the input power is transmitted to the inductor L of FSBB, and the input power P is calculated. in Expression of

[0074] Input power P in The expression is:

[0075]

[0076] In formula (3), S a and S b is the inductor current i L The area enclosed by the t-axis;

[0077] S30103: Set the converter's transmission efficiency to η and calculate the inductor current i according to the power conservation law. L The expression of the initial value -I0;

[0078] Inductor current i L The expression of the initial value -I0 is:

[0079]

[0080] S30104: Calculate the boundary conditions under which the switch tubes S1~S4 and Q5~Q6 can achieve soft switching;

[0081] The boundary conditions for the switch tubes S1~S4 and Q5~Q6 to achieve soft switching are as follows:

[0082]

[0083] S30105: Figure 6 As shown, the phase shift angle α of the switch can be obtained by combining formulas (2), (4) and (5).

[0084] S302: The modulation method includes: the FSBB-level front bridge arm switch tube adopts PWM modulation, the duty cycle of S1 is D, S2 and S1 are complementary turned on. The CLLLC-level front bridge arm switch tubes Q5 and Q6 and the reused bridge arm switch tubes S3 and S4 form an inverter network with a fixed duty cycle of 50% and a fixed switching frequency f r Alternating conduction.

[0085] S4: Determine the duty cycle according to different input and output voltage requirements, and after looking up the table, determine the optimal phase shift angle for control.

[0086] When controlling the converter, the specific control block diagram is as follows Figure 7 As shown in the figure, when the phase shift modulation is used to control the converter, the duty cycle D determines the gain of the FSBB stage, and the subsequent CLLLC converter has a fixed gain of 1, so the overall gain is determined by D. After sampling the output voltage, the duty cycle D of the converter is controlled by PI control to achieve the control of the output voltage. After determining the duty cycle D, in order to obtain the full switch tube soft switch tube, the duty cycle D and the input and output voltage and current are input into the three-dimensional table to query the optimal phase shift angle so that the converter works in the optimal working mode.

[0087] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A modulation and control method for a bridge arm multiplexing type FSBB-CLLLC bidirectional converter, characterized in that: The modulation and control method of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter comprises the following steps: Step 1: Based on the bridge arm multiplexing type FSBB-CLLLC bidirectional converter, the main circuit topology is divided into different bridge arms; Step 2: Obtain different operating modes of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in forward and reverse operation based on the bridge arm phase shift angle α and duty cycle D, where the bridge arm phase shift angle α is the phase angle between the front bridge arm of FSBB and the multiplexing bridge arm, and the duty cycle D is the duty cycle of the upper switch tube S1 in the front bridge arm of FSBB; Step 3: Based on the different working modes of the bridge arm multiplexed FSBB-CLLLC bidirectional converter during forward and reverse operation, solve the soft switching conditions of the corresponding working mode; Step 4: Solve the different inductor currents i of the bridge arm multiplexing FSBB-CLLLC bidirectional converter based on the modulation method of the bridge arm multiplexing FSBB-CLLLC bidirectional converter and the soft switching conditions L The corresponding phase shift angles are calculated and a three-dimensional table is constructed; Step 5: Determine the duty cycle D according to different input and output voltage requirements, input the duty cycle D, input voltage, input current, output current and output voltage into a three-dimensional table, query and obtain the optimal phase shift angle α, and control the bridge arm multiplexing FSBB-CLLLC converter to be in the optimal working mode.

2. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: In step 1, the bridge arm multiplexing type FSBB-CLLLC bidirectional converter includes a DC power supply, a load, FSBB front bridge arm switch tubes S1 and S2, multiplexing bridge arm switch tubes S3 and S4, CLLLC primary side switch tubes Q5 and Q6, CLLLC secondary side first bridge arm switch tubes Q7 and Q8, CLLLC secondary side second bridge arm switch tubes Q9 and Q 10 , FSBB inductor L, CLLLC primary and secondary resonant inductor L r1 , L r2 , CLLLC original secondary side resonant capacitor C r1 , C r2 , with magnetizing inductance L m Transformer T, input and output filter capacitors C in , C o and bus capacitance C bus , input voltage V in and output voltage V.

3. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 2, characterized in that: Bus capacitance C bus The output port is connected to the FSBB-level and CLLLC-level converters. The reused bridge arm switches S3 and S4 are the rear bridge arm switches of the FSBB-level and the primary inverter bridge arm switches of the CLLLC-level. The primary resonant inductor L r1 With the primary side resonant capacitor C r1 The series resonant frequency is f r , the secondary resonant inductor L of the CLLLC stage r2 With the secondary side resonant capacitor C r2 The series resonant frequency is f r , the CLLLC-level converter works at the resonance point, the DC gain is fixed to 1, and the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is calculated based on the duty cycle D; The calculation formula of the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is:

4. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: When the multiplexed FSBB-CLLLC bidirectional converter in step 2 is running in the forward direction, the input voltage V in After FSBB stage, the voltage is pre-stepped down to V bus , through the CLLLC stage fixed gain output voltage V o , and introduce the phase angle α between the rising edges of the S1 and S3 drive signals, and achieve full switch soft switching by adjusting the phase angle α.

5. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: When the multiplexed FSBB-CLLLC bidirectional converter in step 2 is in reverse operation, the input voltage V in Isolate the output to V through CLLLC stage bus , the voltage is adjusted to the required output voltage V by the FSBB stage o , the switch tubes S3~S4 and Q5~Q6 become a rectification network, working in the synchronous rectification mode, and realize soft switching of all switch tubes by adjusting the phase angle α.

6. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: The different operating modes of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in forward and reverse operation in step 2 specifically include: Step 2.1: Taking the rising edge of the S3 driving signal as the reference, define the phase angle between the rising edge of S3 and the rising edge of S1 as α. When S1 is ahead of S3, α>0, and when S1 lags behind S3, α<0; Step 2.2: When the bridge arm multiplexing type FSBB-CLLLC bidirectional converter is in forward operation, when 0<-α<0.5 and 0.5<-α+D<1, S1 is turned on during the conduction period of S3 and is turned off during the conduction period of S4, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modef2; when 0<α<0.5 and 0.5<α+D<1, S1 is turned on during the conduction period of S4 and is turned off during the conduction period of S3, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modef5; Step 2.3: When the bridge arm multiplexing type FSBB-CLLLC bidirectional converter operates in reverse, when 0<-α<0.5, 0.5<-α+D<1, S1 is turned on during the conduction period of S3 and is turned off during the conduction period of S4, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modeb2; when 0<α<0.5, 0.5<α+D<1, S1 is turned on during the conduction period of S4 and is turned off during the conduction period of S3, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modeb5.

7. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: The steps to solve the soft switching conditions in step 3 include: Step 3.1: Calculate the FSBB stage inductor current i L Piecewise expressions for all phases in the operating mode cycle; Step 3.2: When S1 is turned on and the duty cycle and phase shift angle are confirmed, the input power is transmitted to the inductor L of FSBB, and the input power P is calculated. in Expression of Step 3.3: Set the converter's transmission efficiency to η and calculate the inductor current i according to the power conservation law. L The expression of the initial value -I0; Step 3.4: Calculate the boundary conditions for the switch tubes S1~S4 and Q5~Q6 to achieve soft switching; Step 3.5: Combine the FSBB-level inductor current i L The piecewise expressions for all phases in the operating mode cycle, the inductor current i L The initial value -I0 expression and the switch tubes S1~S4, Q5~Q6 can all realize the boundary conditions of soft switching to calculate the optimal phase shift angle α under the current working mode; FSBB level inductor current i L The piecewise expressions for all phases in the working mode cycle are: In formula (2), -I0 is the inductor current i L The initial values ​​of t1, t2, t3, T s It is the time segment within the working mode cycle; Input power P in The expression is: In formula (3), S a and S b is the inductor current i L The area enclosed by the t-axis; Inductor current i L The expression of the initial value -I0 is: The boundary conditions for the switch tubes S1~S4 and Q5~Q6 to achieve soft switching are as follows:

8. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: Constructing a three-dimensional table in step 3 specifically includes: According to the boundary conditions that the switch tubes S1-S4, Q5-Q6 can all realize soft switching, a three-dimensional table of power, duty cycle and phase shift angle α is drawn.

9. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: The modulation method of the bridge arm multiplexing type FSBB-CLLLC bidirectional converter in step 4 specifically includes: The FSBB-level front bridge arm switch tube adopts PWM modulation, the duty cycle of S1 is D, S2 and S1 are complementary, and the CLLLC-level front bridge arm switch tubes Q5 and Q6 and the reused bridge arm switch tubes S3 and S4 form an inverter network with a fixed duty cycle of 50% and a fixed switching frequency f r Alternating conduction.

10. The modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter according to claim 1, characterized in that: When controlling the bridge arm multiplexing type FSBB-CLLLC converter in step 5, the output voltage is first sampled, and the output voltage is controlled by PI control duty cycle D. Then, the duty cycle D and output power are input into a three-dimensional table to query the optimal phase shift angle α to achieve soft switching.

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