Frequency multiplication soft switching control method and controller for six-tube Buck-Boost converter

Abstract

The invention discloses a frequency multiplication soft switching control method and controller for a six-tube Buck-Boost converter, and belongs to the field of power electronic conversion and control, and the method comprises the steps: enabling the switching frequency of a two-level bridge arm in the converter to be twice of the switching frequency of a three-level bridge arm by taking two inductive current periods as a switching period for the six-tube Buck-Boost converter, and enabling the switching frequency of the three-level bridge arm to be twice of the switching frequency of the three-level bridge arm; a switching time sequence for realizing soft switching of a full switching device under a wide input voltage range and a load is designed, and the phase shift angle and the duty ratio of each switch are calculated by taking the pulse minimization of inductive current as a target and taking the soft switching of each switching tube as a constraint. According to the method, zero-voltage switching-on of the full switching device under frequency multiplication of the switching frequency of the six-tube Buck-Boost two-level bridge arm can be realized, and the working efficiency of the converter is improved.

Description

Technical Field

[0001] The present invention belongs to the field of power electronic conversion and control, and more specifically, relates to a frequency doubling soft switch control method and a controller for a six-tube Buck-Boost converter. Background Art

[0002] In common energy storage systems, bidirectional DC / DC converters are key devices for achieving voltage conversion and power transmission. With the increase in the voltage level of energy storage devices, higher pressure-bearing requirements are put forward for the bidirectional DC / DC energy storage side ports. In order to facilitate the selection of switching devices and reduce the switching voltage stress, a three-level bridge arm is used to replace the two-level bridge arm in the traditional four-tube Buck-Boost converter to form a new six-tube Buck-Boost converter. Compared with the midpoint clamped three-level and cascaded three-level structures, the six-tube Buck-Boost converter composed of a flying capacitor three-level has the advantages of common input and output grounding and unrestricted switching timing, which is more suitable for high-voltage and high-power occasions.

[0003] At present, the research on six-tube Buck-Boost converters is still focused on hard-switching control strategies. In order to overcome the problems of high switching losses and low device efficiency caused by the traditional hard-switching control method in high-voltage and high-power working scenarios, zero voltage switching (ZVS) can be used to eliminate the loss when the switch is turned on. Without adding additional auxiliary soft-switching loops, compared with the traditional hard-switching method, the realization of soft switching of all switching devices will increase the pulsation and effective value of the inductor current, resulting in increased conduction losses. Under fixed-frequency control, if the switching frequency in the two-level bridge arm is the same as the switching frequency in the three-level bridge arm, when the input voltage is large and the power is low, a larger proportion of circulating current modes will appear, and the pulsation value and effective value of the inductor current will be large, resulting in larger conduction losses.

[0004] Therefore, in order to improve the working efficiency and power density of the six-tube Buck-Boost converter within the full working range, it is of great research significance to realize soft switching control of the entire device, reduce the proportion of circulating current modes, and reduce the inductor current ripple and effective value under the conditions of large input voltage and low power. Summary of the invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides a frequency doubling soft switching control method and controller for a six-tube Buck-Boost converter, the purpose of which is to achieve soft switching control of the entire device and reduce the proportion of circulating current modes and reduce the pulsation and effective value of the inductor current when the input voltage is large and the power is low.

[0006] To achieve the above object, according to one aspect of the present invention, a frequency doubling soft switching control method for a six-tube Buck-Boost converter is provided, wherein the six-tube Buck-Boost converter comprises a three-level bridge arm, a two-level bridge arm, an inductor and a flying capacitor; the three-level bridge arm comprises a switch tube Q connected in sequence A1 , Q A2 , Q A3 and Q A4 The two-level bridge arm includes switch tubes Q connected in sequence B1 and Q B2 ; One end of the inductor is connected to Q A2 and Q A3 The other end is connected to Q B1 and Q B2 One end of the flying capacitor is connected to Q A1 and Q A2 The other end is connected to Q A3 and Q A4 The method includes: taking two inductor current cycles as one switching cycle, and in each switching cycle, Q A4 and Q A1 Complementary conduction, Q A3 and Q A2 Complementary conduction, Q B2 and Q B1 Complementary conduction; in the first inductor current cycle of each switching cycle, starting at time Q A1 It turns on and turns off after the first period of time, Q A2 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 ; In the second inductor current cycle of each switching cycle, the starting time Q A2 turns on and turns off after the second period of conduction, Q A1 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 Wherein, the first time period and the second time period are obtained by the following method: taking the minimum pulsation of the inductor current as the goal and the soft switching of each switch tube as the constraint, and calculating them.

[0007] Furthermore, the calculation method of the first time period and the second time period specifically includes: SA1, determining the working mode of the six-tube Buck-Boost converter, wherein the working mode includes a discontinuous mode and a continuous mode; SA2, according to the working mode of the six-tube Buck-Boost converter, with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as a constraint, calculating Q A1 The initial on-duty ratio D A1 and Q A2 The initial on-duty ratio D A2 ;SA3, based on 0.5V in The difference between the flying capacitor voltage and the PI control is used. The result of the PI control is limited to obtain the duty cycle compensation value △D, where V in is the input voltage; SA4, using △D to adjust D A1 and D A2 Compensation is performed and Q is obtained accordingly A1 The final on-duty ratio D A1_1 and Q A2 The final on-duty ratio D A2_2 ; SA5, calculate D A1_1 The corresponding first time period, and D A2_2 The corresponding second time period.

[0008] Furthermore, the SA1 specifically includes: if V in >2V out , when I out >I out1 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out1 It is in discontinuous mode; if V in ≤2V out , when I out >I out2 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out2 I out1 and I out2 They are:

[0009]

[0010] Among them, V out is the output voltage, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, Ts is the inductor current period.

[0011] Furthermore, the SA2 specifically includes: according to the working mode of the six-tube Buck-Boost converter, with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as a constraint, calculating the proportion of each mode in an inductor current cycle; A1 and D A2 They are:

[0012] D A1 =D1+D2

[0013] D A2 =D1+D2

[0014] Wherein, D1 is the proportion of the first mode in an inductor current cycle, and D2 is the proportion of the second mode in an inductor current cycle. The first mode refers to V A =0.5V in And V B =0 mode, the second mode refers to V A =0.5V in And V B =V out The mode, V A is the output voltage of the three-level bridge arm, V B is the output voltage of the two-level bridge arm, V out is the output voltage.

[0015] Furthermore, the method further comprises: calculating Q B1 Duty cycle D B1 and conduction phase shift angle φ B1 , according to D B1 and Control Q B1 The on-off, D B1 and They are:

[0016] D B1 =D2+D3

[0017]

[0018] Wherein, D3 is the proportion of the third mode in one inductor current cycle, and the third mode refers to V A = 0 and V B =V out The modality.

[0019] Furthermore, V in >2V out And I out >I out1When D1, D2 and D3 are:

[0020]

[0021] V in >2V out And I out ≤I out1 When D1, D2 and D3 are:

[0022]

[0023] V in ≤2V out And I out >I out2 When D1, D2 and D3 are:

[0024]

[0025] V in ≤2V out And I out ≤I out2 When D1, D2 and D3 are:

[0026]

[0027] Where W = 4I zvs 2 L 2 -LT s V in (16k 2 I out +(8k+4)(I out +I zvs ))+2T s 2 V in 2 k, W are intermediate parameters, D3 is the proportion of the third mode in an inductor current cycle, and the third mode refers to V A = 0 and V B =V out The mode, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, T s is the inductor current period.

[0028] Furthermore, D A1_1 =D A1 +△D,D A2_2 =DA2 -△D.

[0029] Furthermore, the control switch Q A1 , Q A2 , Q A3 , Q A4 , Q B1 and Q B2 During the on-off process, a dead time is set.

[0030] According to another aspect of the present invention, a frequency doubling soft switching controller for a six-transistor Buck-Boost converter is provided, which is used to execute the frequency doubling soft switching control method for a six-transistor Buck-Boost converter as described above.

[0031] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0032] (1) A frequency doubling soft switching control method for a six-tube Buck-Boost converter is provided. For the six-tube Buck-Boost converter, the method takes the realization of zero voltage conduction of each switch tube as a constraint, utilizes the degree of freedom of the duty cycle and phase shift angle of the switch device, optimizes the inductor current pulsation to minimize it, and controls the on and off of each switch tube according to the method. Under the premise of realizing full-range soft switching, the inductor current pulsation can be reduced, the conduction loss of the inductor and the switch device is effectively reduced, the inductor volume is reduced, and the power density is improved;

[0033] (2) A specific calculation method for the duty cycle of a driving signal is provided. The input voltage and output power reference values ​​are used to determine the converter working mode. The input voltage, output power and working area signal are used to calculate the duty cycle and phase shift angle of each switch tube. The switching duty cycle is compensated through the flying capacitor voltage closed-loop control to achieve flying capacitor voltage following. According to the compensated switching tube duty cycle and phase shift angle, a carrier and a modulation wave are generated to control the on and off of each switch tube, thereby improving the working efficiency of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A topological structure diagram of a six-tube Buck-Boost converter provided in an embodiment of the present invention;

[0035] Figure 2 A control block diagram of a six-tube Buck-Boost converter provided in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the division of the continuous mode and the intermittent mode provided in an embodiment of the present invention;

[0037] Figure 4A switching timing diagram of a switching cycle provided by an embodiment of the present invention;

[0038] Figure 5 A switching timing diagram of an inductor current cycle provided by an embodiment of the present invention;

[0039] Figure 6 The control method provided in the embodiment of the present invention is in V in >2V out Schematic diagram of inductor current change when load size changes;

[0040] Figure 7 The control method provided in the embodiment of the present invention is in V in ≤2V out Schematic diagram of inductor current change when load size changes;

[0041] Figure 8 When the control method provided by the embodiment of the present invention is adopted, V in >2V out Working waveform when working in discontinuous mode;

[0042] Fig. 9 When the control method provided by the embodiment of the present invention is adopted, V in >2V out Working waveform when working in continuous mode;

[0043] Fig.10 When the control method provided by the embodiment of the present invention is adopted, V in ≤2V out Working waveform when working in discontinuous mode;

[0044] Fig.11 When the control method provided by the embodiment of the present invention is adopted, V in ≤2V out Working waveform when working in continuous mode. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0047] Embodiment 1

[0048] A frequency-doubling soft-switching control method for a six-transistor Buck-Boost converter, see Figure 1-Figure 11 , the frequency doubling soft switching control method for the six-transistor Buck-Boost converter in this embodiment is described in detail.

[0049] The six-tube Buck-Boost converter includes a three-level bridge arm, a two-level bridge arm, an inductor and a flying capacitor. The three-level bridge arm includes a switch tube Q connected in sequence. A1 , Q A2 , Q A3 and Q A4 The two-level bridge arm includes a switch tube Q connected in sequence B1 and Q B2 One end of the inductor is connected to Q A2 and Q A3 The other end is connected to Q B1 and Q B2 One end of the flying capacitor is connected to Q A1 and Q A2 The other end is connected to Q A3 and Q A4 connection point.

[0050] See also Figure 1 The three-level bridge arm includes the upper bridge arm outer tube Q A1 、Upper bridge arm inner tube Q A2 、Lower bridge arm inner tube Q A3 、Lower bridge arm outer tube Q A4 And the flying capacitor C fly Composition, among which C fly One end and Q A1 Source, Q A2 The drain is connected to the node and the other end is connected to the Q A3 Source, Q A4 The node connected to the drain is connected to the output port Q A2 Source and Q A3 The connection point of the drain. The two-level bridge arm consists of the upper bridge arm switch tube Q B1 With the lower bridge arm switch tube Q B2 The output port is Q B1 With Q B2 The two ends of the inductor L are connected to the output port of the three-level bridge arm and the output port of the two-level bridge arm respectively. o The two ends are connected to the switch tube Q B1 The drain is connected to ground. Figure 2 The control block diagram shown implements this method.

[0051] The frequency doubling soft switching control method for the six-transistor Buck-Boost converter is as follows. Two inductor current cycles are considered as one switching cycle. When operating in steady state, the inductor currents of the two inductor current cycles are exactly the same. In each switching cycle, Q A4 and Q A1 Complementary conduction, Q A3 and Q A2 Complementary conduction, Q B2 and Q B1 Complementary conduction. In the first inductor current cycle of each switching cycle, starting at time Q A1 It turns on and turns off after the first period of time, Q A2 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 , Q B1 The turn-off time lags behind Q A1 Off and ahead of Q A3 In the second inductor current cycle of each switching cycle, starting at time Q A2 turns on and turns off after the second period of conduction, Q A1 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 , Q B1 The turn-off time lags behind Q A2 Off and ahead of Q A4 The first time period and the second time period are obtained by the following method: taking the minimum pulsation of the inductor current as the goal and the soft switching of each switch tube as the constraint, the timing of each switch tube in a switching cycle is as follows: Figure 4 shown.

[0052] Preferably, the calculation method of the first time period and the second time period specifically includes the following operations SA1 to SA5.

[0053] Operation SA1 is performed to determine the working mode of the six-transistor Buck-Boost converter. The working modes include discontinuous mode and continuous mode.

[0054] See also Figure 2 , sample output voltage V out With reference output voltage V out_ref After comparison, the output voltage error value is obtained, which is input into the PI controller PI1, and the power reference value P is output through PI1.ref According to P ref Calculate the output current reference value I out =P ref / V out .

[0055] V in >2V out When the load size changes, the inductor current is as follows Figure 6 As shown, V in ≤2V out When the load size changes, the inductor current is as follows Figure 7 See Figure 6 and Figure 7 , it can be seen that there is Q in the intermittent mode A3 , Q A4 With Q B2 The switching mode of simultaneous conduction does not exist in continuous mode. Figure 3 The specific method for determining the working mode of the six-tube Buck-Boost converter is as follows: If V in >2V out , when I out >I out1 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out1 It is in discontinuous mode; if V in ≤2V out , when I out >I out2 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out2 is in intermittent mode.

[0056] I out1 and I out2 They are:

[0057]

[0058]

[0059] Among them, V out is the output voltage, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, T s is the inductor current period.

[0060] Operate SA2, according to the working mode of the six-tube Buck-Boost converter, with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as the constraint, calculate Q A1 The initial on-duty ratio D A1 and Q A2 The initial on-duty ratio D A2 .

[0061] According to an embodiment of the present invention, operation SA2 specifically includes: according to the working mode of the six-tube Buck-Boost converter, with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as a constraint, calculating the proportion of each mode in an inductor current cycle; D A1 and D A2 They are:

[0062] D A1 =D1+D2

[0063] D A2 =D1+D2

[0064] Among them, D1 is the proportion of the first mode in an inductor current cycle, and D2 is the proportion of the second mode in an inductor current cycle. The first mode refers to V A =0.5V in And V B = 0 mode, the second mode refers to V A =0.5V in And V B =V out The mode, V A is the output voltage of the three-level bridge arm, V B is the output voltage of the two-level bridge arm, V out is the output voltage.

[0065] See also Figure 5 In one inductor current cycle, the converter has the following four modes: V A =0.5V in And V B =0 in the first mode, V A =0.5V in And V B =V out The second mode, V A = 0 and V B =V out The third mode, V A = 0 and V B = 0. The proportion of each mode is calculated as follows.

[0066] V in >2V out And Iout >I out1 When D1, D2, D3 and D4 are:

[0067]

[0068] D4=0

[0069] V in >2V out And I out ≤I out1 When D1, D2, D3 and D4 are:

[0070]

[0071] V in ≤2V out And I out >I out2 When D1, D2, D3 and D4 are:

[0072]

[0073] D4=0

[0074] V in ≤2V out And I out ≤I out2 When D1, D2, D3 and D4 are:

[0075]

[0076] Where W = 4I zvs 2 L 2 -LT s V in (16k 2 I out +(8k+4)(I out +I zvs ))+2T s 2 V in 2 k, W are intermediate parameters, D3 is the proportion of the third mode in an inductor current cycle, and the third mode refers to V A = 0 and V B =V out The mode, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, T sis the inductor current cycle, D3 is the proportion of the third mode in an inductor current cycle, and the third mode refers to V A = 0 and V B =V out mode, and D4 is the proportion of the fourth mode in one inductor current cycle.

[0077] Preferably, the method further comprises: calculating Q B1 Duty cycle D B1 and conduction phase shift angle According to D B1 and Control Q B1 The on-off, D B1 and They are:

[0078] D B1 =D2+D3

[0079]

[0080] Operate SA3, according to 0.5V in The difference between the flying capacitor voltage and the PI control is used. The result of the PI control is limited to obtain the duty cycle compensation value △D, where V in is the input voltage.

[0081] Operate SA4 and use △D to adjust D A1 and D A2 Compensation is performed and Q is obtained accordingly A1 The final on-duty ratio D A1_1 and Q A2 The final on-duty ratio D A2_2 .

[0082] D A1_1 =D A1 +△D

[0083] D A2_2 =D A2 -△D

[0084] Operation SA5, calculate D A1_1 The corresponding first time period, and D A2_2 Specifically, the first time period is equal to D A1_1 The second time period is equal to D A2_2 The product of the inductor current period.

[0085] Preferably, in this embodiment, the control switch tube Q A1 , Q A2 , Q A3 , Q A4 , QB1 and Q B2 In the process of switching on and off, a dead time is set. Specifically, modulation is performed according to the PWM duty ratio and phase shift angle of each switch tube, and a dead time is set to obtain a driving signal of each switch tube.

[0086] Under steady-state conditions, in two adjacent cycles, Q A1 , Q A4 Respectively with Q in the previous inductor current cycle A2 , Q A3 The drive signals are exactly the same; the Q A2 , Q A3 The drive signal is respectively related to the Q A1 , Q A4 The drive signals are exactly the same.

[0087] by Figure 1 , Figure 2 The main parameters in the test example shown are set as follows to verify the effectiveness of this method: Rated capacity P N =6.6kW, the switching frequency of the three-level bridge arm is 100kHz, the switching frequency of the two-level bridge arm is 200kHz, and the minimum DC voltage on the input side is V inmin =500V, maximum input DC voltage V inmax =2000V, output voltage value V out =750V, flying capacitor value C fly =120μF, inductance value L = 75μH, output filter capacitor value C f =80μF, DC input capacitance C in =200μF, output capacitance of the switching device C oss =200pF, zero voltage turn-on current I zvs =2A, dead time t dead =200ns.

[0088] Under the above parameter settings, the six-tube Buck-Boost converter operates at V in >2V out When working in discontinuous mode and continuous mode, the key waveforms are as follows: Figure 8 , Fig. 9 As shown; working at V in ≤2V out When working in discontinuous mode and continuous mode, the key waveforms are as follows: Fig.10 , Fig.11 . See Figure 8-Figure 11It can be seen that this method can effectively realize zero voltage turn-on of all switch devices, which verifies the effectiveness of this method. This method can reduce the conduction loss of the inductor while reducing the switching loss, and improve the working efficiency and power density of the six-tube Buck-Boost converter.

[0089] Embodiment 2

[0090] A frequency doubling soft switch controller for a six-transistor Buck-Boost converter is used to execute the frequency doubling soft switch control method for a six-transistor Buck-Boost converter. The related technical scheme is the same as that of the first embodiment and will not be described in detail here.

[0091] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A frequency doubling soft switching control method for a six-tube Buck-Boost converter, wherein the six-tube Buck-Boost converter comprises a three-level bridge arm, a two-level bridge arm, an inductor and a flying capacitor; the three-level bridge arm comprises a switch tube Q connected in sequence A1 , Q A2 , Q A3 and Q A4 The two-level bridge arm includes switch tubes Q connected in sequence B1 and Q B2 ; One end of the inductor is connected to Q A2 and Q A3 The other end is connected to Q B1 and Q B2 One end of the flying capacitor is connected to Q A1 and Q A2 The other end is connected to Q A3 and Q A4 A connection point; characterized in that Methods include: Two inductor current cycles are considered as one switching cycle. In each switching cycle, Q A4 and Q A1 Complementary conduction, Q A3 and Q A2 Complementary conduction, Q B2 and Q B1 Complementary conduction; In the first inductor current cycle of each switching cycle, the starting time Q A1 It turns on and turns off after the first period of time, Q A2 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 ; In the second inductor current cycle of each switching cycle, starting at time Q A2 turns on and turns off after the second period of conduction, Q A1 Keep off and start time Q B1 Shutdown, at Q A1 Before turning off, Q B1 , in Q A4 The absolute value of the source current is greater than the zero voltage turn-on current, which turns off Q B1 ; The first time period and the second time period are obtained by calculation with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as a constraint.

2. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 1, characterized in that: The calculation method of the first time period and the second time period specifically includes: SA1, determining the working mode of the six-tube Buck-Boost converter, wherein the working mode includes a discontinuous mode and a continuous mode; SA2, according to the working mode of the six-tube Buck-Boost converter, with the goal of minimizing the pulsation of the inductor current and the soft switching of each switch tube as the constraint, calculate Q A1 The initial on-duty ratio D A1 and Q A2 The initial on-duty ratio D A2 ; SA3, based on 0.5V in The difference between the flying capacitor voltage and the PI control is used. The result of the PI control is limited to obtain the duty cycle compensation value △D, where V in is the input voltage; SA4, use △D to calculate D A1 and D A2 Compensation is performed and Q is obtained accordingly A1 The final on-duty ratio D A1_1 and Q A2 The final on-duty ratio D A2_2 ; SA5, calculate D A1_1 The corresponding first time period, and D A2_2 The corresponding second time period.

3. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: The SA1 specifically includes: If V in >2V out , when I out >I out1 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out1 It is in discontinuous mode; if V in ≤2V out , when I out >I out2 When the six-tube Buck-Boost converter is in continuous mode, I out ≤I out2 When in intermittent mode; I out1 and I out2 They are: Among them, V out is the output voltage, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, T s is the inductor current period.

4. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: The SA2 specifically includes: According to the working mode of the six-transistor Buck-Boost converter, the goal is to minimize the pulsation of the inductor current, and the soft switching of each switch tube is constrained to calculate the proportion of each mode in an inductor current cycle; D A1 and D A2 They are: D A1 =D1+D2 D A2 =D1+D2 Wherein, D1 is the proportion of the first mode in an inductor current cycle, and D2 is the proportion of the second mode in an inductor current cycle. The first mode refers to V A =0.5V in And V B =0 mode, the second mode refers to V A =0.5V in And V B =V out The mode, V A is the output voltage of the three-level bridge arm, V B is the output voltage of the two-level bridge arm, V out is the output voltage.

5. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 4, characterized in that: The method also includes: calculating Q B1 Duty cycle D B1 and conduction phase shift angle According to D B1 and Control Q B1 The on-off, D B1 and They are: D B1 =D2+D3 Wherein, D3 is the proportion of the third mode in one inductor current cycle, and the third mode refers to V A = 0 and V B =V out The modality.

6. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 4 or 5, characterized in that: V in >2V out And I out >I out1 When D1, D2 and D3 are: V in >2V out And I out ≤I out1 When D1, D2 and D3 are: V in ≤2V out And I out >I out2 When D1, D2 and D3 are: V in ≤2V out And I out ≤I out2 When D1, D2 and D3 are: Where W = 4I zvs 2 L 2 -LT s V in (16k 2 I out +(8k+4)(I out +I zvs ))+2T s 2 V in 2 k, W are intermediate parameters, D3 is the proportion of the third mode in an inductor current cycle, and the third mode refers to V A = 0 and V B =V out The mode, I out is the output current reference value, I out1 is the first boundary current, I out2 is the second boundary current, k is the ratio of output voltage to input voltage, I ZVS is the zero voltage turn-on current, L is the inductance value, T s is the inductor current period.

7. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: D A1_1 =D A1 +△D,D A2_2 =D A2 -△D。 8. The frequency doubling soft switching control method for a six-transistor Buck-Boost converter according to claim 1, characterized in that: Control switch tube Q A1 , Q A2 , Q A3 , Q A4 , Q B1 and Q B2 During the on-off process, a dead time is set.

9. A frequency doubling soft switch controller for a six-transistor Buck-Boost converter, characterized in that: Used to execute the frequency doubling soft switching control method for a six-tube Buck-Boost converter as described in any one of claims 1-8.

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