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

Abstract

The application provides a modulation and control method of a bridge-arm multiplexing FSBB-CLLLC bidirectional converter, belongs to the technical field of power electronics, and solves the problems of unclear modulation method, unclear working principle and complex soft switching implementation of the bridge-arm multiplexing FSBB-CLLLC converter, and reduces the efficiency, and comprises the following steps: in combination with the bridge-arm multiplexing FSBB-CLLLC bidirectional converter, the main circuit topology is divided into different bridge arms; in combination with the phase-shifting angle and the duty cycle, different working modes of the converter during forward and reverse operation are researched; in combination with the modulation method and the soft switching condition, the relationship between the inductor current and the phase-shifting angle of the converter is researched, and a three-dimensional table is established; according to different input and output voltage requirements, the duty cycle is determined, the optimal phase-shifting angle is determined after table lookup, and full- switching-tube soft switching of the FSBB-CLLLC converter under the stable voltage control is realized.

Description

TECHNICAL FIELD

[0001] The application relates to a modulation and control method of a bridge-arm-reused FSBB-CLLLC bidirectional converter and belongs to the technical field of power electronics. BACKGROUND

[0002] With the rapid development of new energy technology, electric vehicles, direct current microgrids and distributed energy storage systems are gradually becoming the focus of research in the field of new energy technology. Energy bidirectional transmission is required in most of the above-mentioned fields, and the bidirectional transmission of electric energy usually needs to use a bidirectional isolated DC / DC converter (IBDC) to achieve the bidirectional transmission. However, the above-mentioned technologies need to use super capacitors or battery packs to achieve energy storage, and at present, the high-voltage battery pack of an electric vehicle is basically composed of multiple low-voltage lithium batteries in series and parallel, and during the charging process, the battery voltage will change in a large range, and the process is divided into pre-charging, constant-voltage charging and constant-current charging stages. The lower limit of the voltage of the lithium battery discharged to a deep degree is only 0.27 times the nominal voltage, and the voltage after complete charging can reach 1.13 times the nominal voltage, and the maximum and minimum voltage ratio is 4.18. Therefore, in order to cover the voltage range of the lithium battery, it is required that the bidirectional DC / DC converter has a wide bidirectional voltage regulation range.

[0003] Among the many IBDC converters, the bridge-arm-reused FSBB-CLLLC converter (Integrated Buck-Boost CLLLC Convertor, IBBCLLLC) cascades the CLLLC converter and the FSBB converter together, uses the FSBB converter as the pre-stage of the CLLLC converter, widens the voltage regulation range of the CLLLC converter, and at the same time, retains the original side ZVS-ON and the secondary side ZCS-OFF characteristics of the CLLLC converter, and has good application prospects. Therefore, the modulation mode of the bridge-arm-reused FSBB-CLLLC converter is researched, and the corresponding control method is given. SUMMARY

[0004] The application is to solve the problems that the modulation method of the bridge-arm-reused FSBB-CLLLC converter is not clear, the working principle is not clear and the soft switching is complex, which leads to low efficiency, and further proposes a modulation and control method of a bridge-arm-reused FSBB-CLLLC bidirectional converter.

[0005] The technical scheme adopted by the application to solve the above problems is that the steps of the application include:

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

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

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

[0009] Step 4: Based on the modulation method and soft switching conditions of the bridge-arm multiplexing FSBB-CLLLC bidirectional converter, solve the different inductor currents i of the bridge-arm multiplexing FSBB-CLLLC bidirectional converter. 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. Enter the duty cycle D, input voltage, input current, output current, and output voltage into a three-dimensional table to obtain the optimal phase shift angle α and control the bridge arm multiplexing FSBB-CLLLC converter to be in the optimal operating 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 excitation inductance L m Transformer T, input and output filter capacitors C in 、C o and bus capacitance C bus , input voltage V in and the output voltage V.

[0012] Preferably, the bus capacitor C bus The output port is connected to the FSBB and CLLLC converters. The reused bridge arm switches S3 and S4 are the rear bridge arm switches of the FSBB and the primary inverter bridge arm switches of the CLLLC. 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 and the secondary side resonant capacitor C r2 The series resonant frequency is f r , the CLLLC-level converter operates 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 the FSBB stage, the voltage is pre-stepped down to V bus , fixed gain output voltage V through CLLLC stage o , and introduce the phase angle α between the rising edges of the S1 and S3 drive signals, and achieve soft switching of all switches 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 the 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 rectifier network, working in synchronous rectification mode, and realizing 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 during forward and reverse operation in step 2 specifically include:

[0018] Step 2.1: Taking the rising edge of the S3 drive signal as the reference, define the phase angle between the rising edge of S3 and the rising edge of S1 as α. When S1 leads S3, α>0; when S1 lags S3, α<0. D is the duty cycle of the FSBB front-arm switch 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 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 operating mode Modeb2; 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 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 of the operating mode cycle;

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

[0024] Step 3.3: Set the converter's transfer 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 soft switching of switches S1-S4 and Q5-Q6.

[0026] Step 3.5: Combine the FSBB level inductor current i L The piecewise expressions of all phases in the working mode cycle, the inductor current i L The expression of the initial value -I0 and the boundary conditions of the switches S1~S4, Q5~Q6 can all realize soft switching and 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 Divide the time into segments 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 for the initial value -I0 is:

[0034]

[0035] The boundary conditions for the switches S1 to S4 and Q5 to 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 switches S1-S4 and Q5-Q6 can all achieve 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 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.

[0041] Preferably, 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.

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

[0043] 1. The multiplexed converter of the present invention adopts a bridge arm multiplexing structure, which effectively reduces the cost. The multiplexed bridge arm is more conducive to realizing soft switching and 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 achieve soft switching of all switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The 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 for a bridge arm multiplexing type FSBB-CLLLC bidirectional converter provided by the present invention;

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

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

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

[0051] Figure 6 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] Combine Figure 1-7 This embodiment is described as follows. Figure 2 As shown, the modulation and control method of a bridge arm multiplexing type FSBB-CLLLC bidirectional converter described in this embodiment includes the following steps:

[0054] S1: Combined with the bridge-arm multiplexing 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 switches S1 and S2, multiplexing bridge arm switches S3 and S4, CLLLC primary side switches Q5 and Q6, CLLLC secondary side first bridge arm switches Q7 and Q8, CLLLC secondary side second bridge arm switches Q9 and Q10. 10 , FSBB inductor L, CLLLC primary and secondary resonant inductor L r1 , L r2 , CLLLC original secondary side resonant capacitor Cr1 、C r2 , with excitation inductance L m Transformer T, input and output filter capacitors C in 、C o , busbar capacitance C bus , where busbar 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-side inverter bridge arm switches of the CLLLC-level. The primary-side 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 side resonant inductor and resonant capacitor is also f r .

[0056] For the bridge-arm multiplexing FSBB-CLLLC bidirectional converter, the CLLLC-stage converter operates at the resonant point, with a fixed DC gain of 1, while the FSBB-stage converter gain depends on the duty cycle D. Therefore, 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 the 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 drive signals is introduced, and the soft switching of all switches 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 output voltage 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 the rectification network, and because of the use of the bridge arm multiplexing structure, it needs to work in the 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 of S1 and the phase angle α, the various working modes corresponding to the phase shift modulation method 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 turns on during the conduction period of S3. Based on the off-time of S1, three operating modes of the FSBB-CLLLC can be obtained: Modef1-modef3. If -α + D < 0.5, S1 turns on and off during the conduction period of S3, and this mode is defined as Modef1. If 0.5 < -α + D < 1, S1 turns off during the conduction period of S4, and this mode is defined as Modef2. If -α + D > 1, S1 turns off during the conduction period of S3 in the next cycle, and this 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 operating 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 operate 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 operating 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 in the figure, similar to the forward operation, the four modes Modeb1, Modeb3, Modeb4 and Modeb6 are not suitable for FSBB stage control. However, the inductor current waveforms of Modeb5 and Modef2 are the same and belong to the same mode. The inductor current waveforms of Modeb2 and Modef5 are the same and can also be classified as the same mode, which is suitable for FSBB stage control.

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

[0068] In the FSBB-CLLLC converter, switches S1 and S4 require floating-point current to achieve ZVS-ON. The current waveform of inductor L is controlled by duty cycle D and phase shift angle α, where D is determined by the converter's DC gain. Adjusting phase shift angle α enables soft switching of the FSBB-level switches. Since the CLLLC-level converter itself can achieve soft switching of all switches, the FSBB-CLLLC converter can achieve this.

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

[0070] S30101: Calculate the FSBB-level inductor current i L Segmented expressions for all phases of 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 Expressions 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 for the initial value -I0 is:

[0079]

[0080] S30104: Calculate the boundary conditions for soft switching of switches S1-S4 and Q5-Q6.

[0081] The expression of the boundary condition of the soft switch of the switch tubes S1-S4, Q5-Q6 can be realized as follows:

[0082]

[0083] S30105: as shown in the formula (2), (4) and (5) can be obtained by the phase shift angle alpha. Figure 6

[0084] S302: the modulation method includes that the PWM modulation is used for the front bridge arm switch tube of the FSBB stage, the duty cycle of S1 is D, and S2 and S1 are complementary conduction. The switch tubes Q5 and Q6 of the front bridge arm of the CLLL stage and the multiplex bridge arm switch tubes S3 and S4 form an inverter network, and the fixed duty cycle is 50%, and the fixed switching frequency f r is alternately conducted.

[0085] S4: according to different input and output voltage requirements, the duty cycle is determined, and after the table is searched, the optimal phase shift angle is determined for control.

[0086] When the converter is controlled, the specific control block diagram is shown in Figure 7 When the converter is controlled by the phase shift modulation, the duty cycle D determines the gain of the FSBB stage, and the rear stage CLLL converter is a fixed gain 1, so the overall gain is determined by D. The duty cycle D of the converter is controlled by the PI control after the output voltage is sampled, so as to realize the control of the output voltage. After the duty cycle D is determined, in order to obtain the full switch soft switch tube, the duty cycle D and the input and output voltage and current are input into the three-dimensional table, and the optimal phase shift angle is inquired, so that the converter works in the optimal working mode.

[0087] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the present application, and the equivalent embodiments with equivalent changes are equivalent. However, any simple modification, equivalent replacement and improvement of the above embodiments within the technical solution of the present application, according to the technical essence of the present application, within the spirit and principle of the present application, are still within the protection scope of the present application.​

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 includes the following steps: Step 1: Based on the bridge-arm multiplexing FSBB-CLLLC bidirectional converter, the main circuit topology is divided into different bridge arms; The bridge arm multiplexing type FSBB-CLLLC bidirectional converter in step 1 includes a DC power supply, a load, and a FSBB front bridge arm switch tube. S 1. S 2. Multiplexing bridge arm switch tube S 3. S 4. CLLLC primary side switch tube Q 5. Q 6. CLLLC secondary side first bridge arm switch tube Q 7. Q 8. CLLLC secondary side second bridge arm switch tube Q 9. Q 10 , FSBB inductor L , CLLLC primary and secondary resonant inductors 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 busbar capacitance C bus , input voltage V in and output voltage V o ; Step 2: Phase shift angle based on bridge arm α and duty cycle D Obtain different operating modes of the bridge arm multiplexing FSBB-CLLLC bidirectional converter during forward and reverse operation, where the bridge arm phase shift angle α is the phase angle between the front bridge arm and the multiplexed bridge arm of FSBB, and the duty cycle D It is the upper switch tube in the front bridge arm of FSBB S A duty cycle of 1; The different operating modes of the bridge arm multiplexing FSBB-CLLLC bidirectional converter during forward and reverse operation in step 2 specifically include: Step 2.1: S 3. Based on the rising edge of the driving signal, define S 3's rising edge and S The phase angle between the rising edges is α ,when S 1 ahead of S 3 o'clock, α >0, when S 1 lags behind S 3 o'clock, α <0; Step 2.2: When the bridge arm multiplexing type FSBB-CLLLC bidirectional converter is running in the forward direction, when 0<- α <0.5 and 0.5<- α+D <1 hour, S 1 in S 3 is turned on during conduction. S 4 turns off during the conduction period, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the working mode Modef2; when 0< α <0.5 and 0.5< α+D <1 hour, S 1 in S 4 is turned on during conduction. S 3. A shutdown occurs during the conduction period, 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 is running in reverse, when 0<- α <0.5, 0.5<- α+D <1 hour, S 1 in S 3 is turned on during conduction. S 4 turns off during the conduction period, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the working mode Modeb2; when 0< α <0.5, 0.5< α+D <1 hour, S 1 in S 4 is turned on during conduction. S 3. A shutdown occurs during the conduction period, and the bridge arm multiplexing type FSBB-CLLLC bidirectional converter enters the operating mode Modeb5; Step 3: Based on the different operating modes of the bridge-arm multiplexed FSBB-CLLLC bidirectional converter during forward and reverse operation, solve the soft switching conditions of the corresponding operating modes; Step 4: Solve the different inductor currents of the bridge-arm multiplexing FSBB-CLLLC bidirectional converter based on the modulation method and soft switching conditions of the bridge-arm multiplexing FSBB-CLLLC bidirectional converter i L The corresponding phase shift angle and construct a three-dimensional table; Step 5: Determine the duty cycle based on different input and output voltage requirements D , the duty cycle D , input voltage, input current, output current and output voltage are input into the three-dimensional table to obtain the optimal phase shift angle α , controlling the bridge arm multiplexing type 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: Bus capacitance C bus As the output port, it connects the FSBB level and CLLLC level converter, and reuses the bridge arm switch tube S 3. S 4 is the FSBB level rear bridge arm switch tube and CLLLC level primary side inverter bridge arm switch tube, CLLLC level primary side resonant inductor L r1 With the primary side resonant capacitor C r1 The series resonant frequency is f r , the secondary resonant inductor of the CLLLC level L r2 and secondary side resonant capacitor C r2 The series resonant frequency is f r , the CLLLC converter operates at the resonant point, the DC gain is fixed to 1, based on the duty cycle D The total gain of the bridge arm multiplexing FSBB-CLLLC converter is calculated G ; The calculation formula of the total gain G of the bridge arm multiplexing FSBB-CLLLC converter is: （1）。 3. 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 the FSBB stage, the voltage is pre-reduced to V bus , fixed gain output voltage through CLLLC stage V o , and introduce S 1 and S 3 Phase angle between the rising edges of the driving signal α , by adjusting the phase angle α Realize soft switching of all switch tubes.

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 reverse, the input voltage V in After CLLLC level isolation output to V bus , the voltage is adjusted to the required voltage output through the FSBB stage V o , switch tube S 3~ S 4 and Q 5~ Q 6 becomes a rectifier network, which works in synchronous rectification mode and realizes soft switching of all switches 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: The steps to solve the soft switching conditions in step 3 include: Step 3.1: Calculate the FSBB stage inductor current i L Segmented expressions for all phases of the operating mode cycle; Step 3.2: When S 1 is turned on and the duty cycle and phase shift angle are confirmed, the input power is transferred to the inductor of FSBB L The input power is calculated P in Expressions of Step 3.3: Set the converter's transfer efficiency to η , according to the law of conservation of power, the inductor current is calculated i L Initial value of - I Expression of 0; Step 3.4: Calculate the switch S 1~ S 4. Q 5~ Q 6. Both can realize the boundary conditions of soft switching; Step 3.5: Combine FSBB-level inductor current i L The piecewise expressions of the inductor current at all stages of the operating mode cycle, i L Initial value of - I 0 expression and switch tube S 1~ S 4. Q 5~ Q 6 can achieve the boundary conditions of soft switching and calculate the optimal phase shift angle under the current working mode α ; FSBB level inductor current i L The piecewise expressions for all phases in the working mode cycle are: （2）； In formula (2), - I 0 is the inductor current i L The initial value of Divide the time into segments within the working mode cycle; Input power P in The expression is: （3）； In formula (3), S a and S b is the inductor current i L and t The area enclosed by the coordinate axes; Inductor current i L Initial value of - I The expression for 0 is: （4）； Switching tube S 1~ S 4. Q 5~ Q 6 The boundary conditions for achieving soft switching are as follows: （5）。 6. 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 switch tube S 1~ S 4. Q 5~ Q 6 can realize the boundary conditions of soft switching and draw a three-dimensional table about power, duty cycle and phase shift angle α.

7. 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. S The duty cycle of 1 is D , S 2 and S 1 complementary conduction, CLLLC level front bridge arm switch tube Q 5. Q 6 and multiplexed bridge arm switch tube S 3. S 4 form an inverter network with a fixed duty cycle of 50% and a fixed switching frequency f r Alternating conduction.

8. 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 multiplexed FSBB-CLLLC converter in step 5, first sample the output voltage and control the duty cycle through PI. D To achieve output voltage control, then the duty cycle D And the output power are input into the three-dimensional table to find out the optimal phase shift angle α and realize soft switching.

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