Soft switching control method and controller for six-tube Buck-Boost converter

Abstract

The invention discloses a soft switching control method for a six-tube Buck-Boost converter and a controller, and belongs to the field of power electronic conversion and control, the method comprises the following steps: aiming at the six-tube Buck-Boost converter, taking two inductive current periods as a switching period, and carrying out soft switching on the six-tube Buck-Boost converter; 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 six-tube Buck-Boost full-switching device can be realized, the inductive current pulsation is reduced through duty ratio control and phase shift control, 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 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. Therefore, a three-level bridge arm is usually 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 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 converter focuses on model predictive control (MPC) and multi-mode control, both of which are hard-switching control strategies. In order to overcome the problems of high switching loss 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, the soft switching of all switching devices will increase the inductor current pulsation compared to the traditional hard-switching method, resulting in increased conduction losses.

[0004] Therefore, in order to improve the working efficiency and power density of the six-tube Buck-Boost converter, how to achieve soft switching control of the entire device and reduce the inductor current pulsation on this basis is of great research significance. Summary of the invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides a soft switching control method and controller for a six-tube Buck-Boost converter, which aims to reduce switching losses while reducing conduction losses caused by inductor current pulsation, thereby improving the working efficiency and power density of the six-tube Buck-Boost converter.

[0006] To achieve the above object, according to one aspect of the present invention, a 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 A4The 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 and Q A2 At the same time, Q A1 After the first period of conduction, Q A2 After the second period of conduction, it is turned off, starting at the moment Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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, Q A1 , Q A2 The driving signals correspond to the first inductor current cycle Q A2 , Q A1 The driving signal is the same, starting at Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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, according to the input voltage V in , output voltage V out and the output current reference value I out, determine its working condition; SA2, according to the working condition 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 the proportion of each mode in an inductor current cycle; SA3, based on 0.5V in The difference between the voltage of the flying capacitor and the voltage of the flying capacitor is used for PI control. The result of the PI control is limited to obtain the duty cycle compensation value △D, and △D is used to compensate for the proportion of the third mode. SA4, according to the proportion of the first mode, the proportion of the second mode and the proportion of the third mode after compensation, calculate Q A1 The on-duty ratio D A1 and Q A2 The on-duty ratio D A2 , where the first mode refers to V A =V in And V B = 0 mode, the second mode refers to V A =V in And V B =V out The third 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; SA5, calculate D A1 The corresponding first time period, and D A2 The corresponding second time period.

[0008] Furthermore, the SA1 specifically includes: when V in >V out When I out >I out1 The six-tube Buck-Boost converter is in the first operating condition. If I out2 out ≤I out1 In the second working condition, if I out ≤I out2 In the third working condition; when V in ≤V out When I out >I out3 The six-tube Buck-Boost converter is in the fourth operating condition. If I out ≤I out3 In the fifth working condition; I out1 ,I out2 and I out3 They are:

[0009] ​

[0010] Among them, I out1 is the first boundary current, I out2 is the second boundary current, I out3 is the third 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.

[0011] Furthermore, the proportion of the third mode after compensation is:

[0012] D 3_1 =D3+△D

[0013] D A1 and D A2 They are:

[0014] D A1 =D1+D2

[0015] D A2 =D1+D2+D 3_1

[0016] Among them, D 3_1 is the proportion of the third mode after compensation, D3 is the proportion of the third mode before compensation, D2 is the proportion of the second mode, and D1 is the proportion of the first mode.

[0017] Furthermore, the proportion of the third mode after compensation is:

[0018] D 3_1 =D3-△D

[0019] D A1 and D A2 They are:

[0020] D A1 =D1+D2+D 3_1

[0021] D A2 =D1+D2

[0022] Among them, D 3_1 is the proportion of the third mode after compensation, D3 is the proportion of the third mode before compensation, D2 is the proportion of the second mode, and D1 is the proportion of the first mode.

[0023] 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, DB1 and They are:

[0024] D B1 =D2+D 3_1 +D4

[0025]

[0026] Among them, D1 is the proportion of the first mode, D2 is the proportion of the second mode, and D 3_1 is the proportion of the third mode after compensation, and D4 is the proportion of the fourth mode.

[0027] 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.

[0028] According to another aspect of the present invention, a soft switching controller for a six-transistor Buck-Boost converter is provided, which is used to execute the soft switching control method for a six-transistor Buck-Boost converter as described above.

[0029] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0030] (1) A 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, and the conduction loss caused by the inductor current pulsation can be reduced, thereby effectively reducing the conduction loss of the inductor and the switch device, reducing the inductor volume, and improving the power density;

[0031] (2) A specific calculation method for the duty cycle of a driving signal is provided. The input voltage, output voltage and output power reference values ​​are used to determine the working condition of the converter. 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 closed-loop control of the flying capacitor voltage to achieve flying capacitor voltage following. According to the compensated switching duty cycle and phase shift angle of the switching tube, a carrier and a modulation wave are generated to control the on and off of each switching tube, thereby improving the working efficiency of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A topological structure diagram of a six-tube Buck-Boost converter provided in an embodiment of the present invention;

[0033] Figure 2 A control block diagram of a six-tube Buck-Boost converter provided in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the division of different working conditions provided by an embodiment of the present invention;

[0035] Figure 4 A switching timing diagram of an inductor current cycle provided by an embodiment of the present invention;

[0036] Figure 5 A switching timing diagram of a switching cycle provided by an embodiment of the present invention;

[0037] Figure 6 The control method provided by the embodiment of the present invention is in V in >V out Schematic diagram of inductor current change when load size changes;

[0038] Figure 7 The control method provided by the embodiment of the present invention is in V in ≤V out Schematic diagram of inductor current change when load size changes;

[0039] Figure 8 The working waveform under the first working condition when the control method provided by the embodiment of the present invention is adopted;

[0040] Fig. 9 The working waveform under the second working condition when the control method provided by the embodiment of the present invention is adopted;

[0041] Fig.10 The working waveform under the third working condition when the control method provided by the embodiment of the present invention is adopted;

[0042] Fig.11 The working waveform under the fourth working condition when the control method provided by the embodiment of the present invention is adopted;

[0043] Fig.12 The working waveform under the fifth working condition when the control method provided by the embodiment of the present invention is adopted;

[0044] Fig.13 The working waveform when the input voltage changes when the control method provided by the embodiment of the present invention is adopted. 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 accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0047] Embodiment 1

[0048] A soft switching control method for a six-transistor Buck-Boost converter, see Figure 1-Figure 13 , the 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 A3The 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 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 and Q A2 At the same time, Q A1 After the first period of conduction, Q A2 After the second period of conduction, it is turned off, starting at the moment Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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, Q A1 , Q A2 The driving signals correspond to the first inductor current cycle Q A2 , Q A1 The driving signal is the same, starting at Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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 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 5 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, according to the six-tube Buck-Boost converter input voltage V in , output voltage V out and the output current reference value I out , determine the working condition it is in.

[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 >V out When the load size changes, the inductor current is as follows Figure 6 As shown, V in ≤V 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 when V in >V out When A1 With Q A2 The turn-off time is the same. When the load current decreases, it enters the fifth working condition from the fourth working condition. The fifth working condition has Q A3 , Q A4 With Q B2 The switching mode of simultaneous conduction is not present in the fourth condition; when V in ≤V out When the load current decreases, it enters the second working condition from the first working condition. The second working condition has Q A1 With Q A2 One of them has a constant on-duty cycle, and the current at point B is constant at I zvs When the load current is further reduced, it enters the third working condition from the second working condition. The third working condition has Q A3 , Q A4 With Q B2 The switching mode is turned on at the same time, but not in the first and second conditions. The current at point B is constant at I zvs .

[0056] See also Figure 3The working conditions of the six-tube Buck-Boost converter are divided into five types, and the working conditions are judged by the input voltage boundary value and the output current boundary value. The specific judgment method is as follows: in >V out When I out >I out1 The six-tube Buck-Boost converter is in the first operating condition. If I out2 out ≤I out1 In the second working condition, if I out ≤I out2 In the third working condition; when V in ≤V out When I out >I out3 The six-tube Buck-Boost converter is in the fourth operating condition. If I out ≤I out3 In the fifth working state.

[0057] I out1 ,I out2 and I out3 They are:

[0058]

[0059] Among them, I out1 is the first boundary current, I out2 is the second boundary current, I out3 is the third 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 condition 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, and calculate the proportion of each mode in an inductor current cycle.

[0061] Under the first working condition, the proportions of each mode in one inductor current cycle are:

[0062]

[0063] W1=-I zvs 2 L 2 +2I zvs LT s V in (k+1)+2I out LT s V in (k 2 ​+k+1)-T s 2 V in 2 k

[0064] Among them, D1, D2, D3, D4, and D5 are the proportions of the first mode, the second mode, the third mode, the fourth mode, and the fifth mode in one inductor current cycle, respectively, and W1 is the first intermediate parameter.

[0065] The first mode is V A =V in And V B = 0 mode, the second mode refers to V A =V in And V B =V out The third mode refers to V A =0.5V in And V B =V out The fourth mode refers to V A = 0 and V B =V out The fifth mode is V A = 0 and V B = 0 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. The first mode, the second mode, the third mode, the fourth mode, and the fifth mode correspond to Figure 4 T1, T2, T3, T4, and T5.

[0066] Under the second working condition, the proportions of each mode in one inductor current cycle are:

[0067]

[0068] D5=0

[0069] W2=(-4I zvs 2 L 2 (k 2 +k)+LT s V in (I zvs (4k 2 -2)-2I out )-T s 2 V in 2 (k 2 -k)) (1 / 2)

[0070] Under the third working condition, the proportions of each mode in one inductor current cycle are:

[0071]

[0072] W3=(L 2 I zvs 2 +I out LT s V in (-4k 2 +6k-2)) (1 / 2)

[0073] Under the fourth working condition, the proportions of each mode in one inductor current cycle are:

[0074]

[0075]

[0076] D3=0

[0077]

[0078] D5=0

[0079] W4=(I zvs 2 L 2 -2I zvs LT s V in (k+1)-2I out LT s V in (k 2 +k+1)+T s 2 V in 2 k) (1 / 2)

[0080] Under the fifth working condition, the proportions of each mode in one inductor current cycle are:

[0081]

[0082] D3=0

[0083]

[0084] W5=(L 2 I zvs 2 -2I out T s LV in (1-k)) (1 / 2)

[0085] Among them, W2, W3, W4, and W5 are the second intermediate parameter, the third intermediate parameter, the fourth intermediate parameter, and the fifth intermediate parameter respectively.

[0086] Operate SA3, according to 0.5V in The difference between the voltage of the flying capacitor and the duty cycle is controlled by PI. The result of the PI control is limited to obtain a duty cycle compensation value △D, and △D is used to compensate for the proportion of the third mode.

[0087] Operation SA4, calculate Q according to the proportion of the first mode, the proportion of the second mode, and the proportion of the third mode after compensation A1 The on-duty ratio D A1 and Q A2 The on-duty ratio D A2 .

[0088] In one embodiment of the present invention, the proportion of the third mode after compensation is:

[0089] D 3_1 =D3+△D

[0090] D A1 and D A2 They are:

[0091] D A1 =D1+D2

[0092] D A2 =D1+D2+D 3_1

[0093] In this embodiment, Q A4 Hysteresis Q A3 Open.

[0094] In another embodiment of the present invention, the proportion of the third mode after compensation is:

[0095] D 3_1 =D3-△D

[0096] D A1 and D A2 They are:

[0097] D A1 =D1+D2+D 3_1

[0098] D A2 =D1+D2

[0099] In this embodiment, Q A4 Advance Q A3 Open. 3_1is the proportion of the third mode after compensation, D3 is the proportion of the third mode before compensation, D2 is the proportion of the second mode, and D1 is the proportion of the first mode.

[0100] Operation SA5, calculate D A1 The corresponding first time period, and D A2 Specifically, the first time period is equal to D A1 The second time period is equal to D A2 The product of the inductor current period.

[0101] According to an embodiment of the present invention, 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:

[0102] D B1 =D2+D 3_1 +D4

[0103]

[0104] Among them, D1 is the proportion of the first mode, D2 is the proportion of the second mode, and D 3_1 is the proportion of the third mode after compensation, and D4 is the proportion of the fourth mode.

[0105] Preferably, in this embodiment, the control switch tube Q A1 , Q A2 , Q A3 , Q A4 , Q B1 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.

[0106] 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.

[0107] 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, switching frequency is 100kHz, minimum input DC voltage V inmin =500V, maximum input DC voltage V inmax =1500V, 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.

[0108] Under the above parameter settings, the key waveforms of the six-tube Buck-Boost converter in the first, second, third, fourth and fifth working conditions are as follows: Figure 8 , 9 , 10, 11, and 12. Figure 8-Figure 12 It can be seen that the present method can effectively realize zero-voltage turn-on of all switching devices.

[0109] Under the above parameter settings, when the input voltage of the six-tube Buck-Boost converter changes, the inductor current waveform and the flying capacitor voltage waveform are as follows: Fig.13 See Fig.13 It can be seen that this method can effectively achieve capacitor voltage tracking 0.5 times the input voltage. Figure 8-Figure 13 , which verifies the effectiveness of this method.

[0110] The soft switching control method for a six-tube Buck-Boost converter provided by an embodiment of the present invention adopts a switching timing to realize soft switching of all switch devices under a wide input voltage range and load, judges the working condition of the converter according to the output power reference value and input voltage obtained by the output voltage closed loop, calculates the duty cycle of each working mode in the soft switching timing according to the working condition, input voltage and output power, compensates the flying capacitor charging and discharging mode time by closed-loop control of the flying capacitor, calculates the switch tube duty cycle and phase shift angle by using the compensated switching mode time, generates a carrier and a modulation wave, and obtains a driving signal. This method can realize zero voltage switching of the six-tube Buck-Boost full switch device, and at the same time reduces the inductor current pulsation through duty cycle control and phase shift control, thereby improving the working efficiency of the converter.

[0111] Embodiment 2

[0112] A soft switch controller for a six-transistor Buck-Boost converter is used to execute the above-mentioned 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.

[0113] 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 soft switch 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 and Q A2 At the same time, Q A1 After the first period of conduction, Q A2 After the second period of conduction, it is turned off, starting at the moment Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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 ; During the second inductor current cycle of each switching cycle, Q A1 , Q A2 The driving signals correspond to the first inductor current cycle Q A2 , Q A1 The driving signal is the same, starting at Q B1 Shutdown, at Q A3 and Q A4 Before turning on 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 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, based on the input voltage V of the six-tube Buck-Boost converter in , output voltage V out and the output current reference value I out , determine the working condition it is in; SA2, based on the working conditions 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, calculates the proportion of each mode in an inductor current cycle; SA3, based on 0.5V in The difference between the voltage of the flying capacitor and the voltage of the flying capacitor is subjected to PI control. The result of the PI control is limited to obtain a duty cycle compensation value △D, and △D is used to compensate for the proportion of the third mode. SA4, calculate Q according to the proportion of the first mode, the proportion of the second mode and the proportion of the third mode after compensation A1 The on-duty ratio D A1 and Q A2 The on-duty ratio D A2 , where the first mode refers to V A =V in And V B = 0 mode, the second mode refers to V A =V in And V B =V out The third 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; SA5, calculate D A1 The corresponding first time period, and D A2 The corresponding second time period.

3. The soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: The SA1 specifically includes: When V in >V out When I out >I out1 The six-tube Buck-Boost converter is in the first operating condition. If I out2 out ≤I out1 In the second working condition, if I out ≤I out2 In the third working condition;​ When V in ≤V out When I out >I out3 The six-tube Buck-Boost converter is in the fourth operating condition. If I out ≤I out3 In the fifth working condition; I out1 ,I out2 and I out3 They are: Among them, I out1 is the first boundary current, I out2 is the second boundary current, I out3 is the third 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 soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: The proportion of the third mode after compensation is: D 3_1 =D3+△D D A1 and D A2 They are: D A1 =D1+D2 D A2 =D1+D2+D 3_1 Among them, D 3_1 is the proportion of the third mode after compensation, D3 is the proportion of the third mode before compensation, D2 is the proportion of the second mode, and D1 is the proportion of the first mode.

5. The soft switching control method for a six-transistor Buck-Boost converter according to claim 2, characterized in that: The proportion of the third mode after compensation is: D 3_1 =D3-△D D A1 and D A2 They are: D A1 =D1+D2+D 3_1 D A2 =D1+D2 Among them, D 3_1 is the proportion of the third mode after compensation, D3 is the proportion of the third mode before compensation, D2 is the proportion of the second mode, and D1 is the proportion of the first mode.

6. The soft switching control method for a six-transistor Buck-Boost converter according to any one of claims 2 to 5, 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+D 3_1 +D4 Among them, D1 is the proportion of the first mode, D2 is the proportion of the second mode, and D 3_1 is the proportion of the third mode after compensation, and D4 is the proportion of the fourth mode.

7. The 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.

8. A soft switching controller for a six-transistor Buck-Boost converter, characterized in that: Used to execute the soft switching control method for a six-transistor Buck-Boost converter as described in any one of claims 1 to 7.

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