A bidirectional six-switch buck-boost topology circuit and a control method thereof

Abstract

The application discloses a bidirectional six-switch buck-boost topology circuit and a control method thereof, and belongs to the technical field of power electronics. The scheme additionally increases two switching tubes and an inductor on the basis of a four-switch buck-boost step-up and step-down circuit, separates the input and output negative poles through the additionally increased switching tube and inductor, thereby effectively solving the problem of circulating current formed by the direct connection of the negative bus when different input sources are output in parallel; the loop does not need to judge the input and output voltage relationship, directly adjusts the duty cycle of the power switching tube according to the set voltage, current and energy transmission direction, decides the step-up and step-down state of the topology and realizes the control of the energy transmission direction according to the calculation result of the duty cycle, and determines the conduction and turn-off of the synchronous rectifier tube through the size of the output current. The scheme of the embodiment of the application can solve the circulating current problem caused by the difference of multiple inputs, reduce the control difficulty of the topology and improve the fault tolerance of the control.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a bidirectional six-switch buck-boost topology circuit and a control method thereof. Background Art

[0002] Among the existing buck-boost topologies, the two most common structures are the two-switch buck-boost buck-boost topology and the four-switch buck-boost buck-boost topology. Figure 1 and Figure 2 As shown in Figure 2, the biggest feature of these two topologies is that the negative poles of the input and output are directly connected together, which is a non-isolated topology. Although this design has a simple structure, it has significant problems in multi-channel parallel applications. Figure 3 As shown in the figure, when using a four-switch buck-boost buck-boost topology, if multiple PFC (Power Factor Correction) circuits are connected in parallel as input sources, the negative output terminals of the multiple buck-boost buck-boost circuits are connected, and the negative busbars of the multiple PFC circuits are also directly connected together. If the DC bus output voltages input to the PFC circuits are inconsistent, the potentials at the midpoints of the PFC circuit bridge arms will differ. These potential differences will gradually generate current through the directly connected negative busbars, forming differential-mode currents between the modules. This differential-mode current not only prevents normal parallel operation but can also cause overcurrent output, ultimately damaging components such as switches and fuses.

[0003] Therefore, in order to solve the circulation current problem when multiple buck-boost boost / lower voltage circuits are connected in parallel, it is urgent to propose a new circuit topology and switch tube control strategy to solve these problems and ensure the stability and reliability of the system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the above-mentioned defects of the prior art, a bidirectional six-switch buck-boost topology circuit and a control method thereof are provided.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a bidirectional six-switch buck-boost topology circuit, wherein the topology circuit is connected between a first terminal and a second terminal, and the input and output directions of the first terminal and the second terminal are adjustable. The bidirectional six-switch buck-boost topology circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, and a second inductor;

[0006] The gates of the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube, and the sixth switching tube are all connected to a control system through a driving circuit;

[0007] The drain of the first switching tube is connected to the positive electrode of the first end, the source of the first switching tube is respectively connected to one end of the first inductor and the drain of the second switching tube, the source of the second switching tube is respectively connected to one end of the second inductor and the drain of the third switching tube, the source of the third switching tube is connected to the negative electrode of the first end, the source of the fourth switching tube is connected to the negative electrode of the second end, the drain of the fourth switching tube is respectively connected to the other end of the second inductor and the source of the fifth switching tube, the drain of the fifth switching tube is respectively connected to the other end of the first inductor and the source of the sixth switching tube, and the drain of the sixth switching tube is connected to the positive electrode of the second end.

[0008] Preferably, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are one of MOS tubes, IGBTs, SICMOS, and gallium nitride MOS tubes.

[0009] Preferably, a capacitor is connected in parallel between the drain of the first switching tube and the source of the third switching tube, and a capacitor is connected in parallel between the drain of the sixth switching tube and the source of the fourth switching tube.

[0010] Preferably, the bidirectional six-switch buck-boost topology circuit also includes a common-mode inductor, a first connection end of the common-mode inductor connected to the positive electrode of the first end, a second connection end of the common-mode inductor connected to the drain of the first switch tube, a third connection end of the common-mode inductor connected to the negative electrode of the first end, and a fourth connection end of the common-mode inductor connected to the source of the third switch tube.

[0011] In a second aspect, the present invention further provides a bidirectional six-switch buck-boost topology circuit control method, which is applied to the bidirectional six-switch buck-boost topology circuit described above, comprising:

[0012] Receive control parameters sent from the outside, the control parameters including voltage, current, and energy transfer direction; calculate the duty cycle according to the control parameters and the sampled value of the output end, and control the on and off of each switch tube according to the control parameters and the duty cycle;

[0013] The positive current of the output end and the negative current of the output end in the monitoring loop are monitored. If the difference between the two exceeds a preset threshold, the connection between the negative pole of the input end and the negative pole of the output end is cut off by turning off the switch tube.

[0014] Preferably, calculating the duty cycle according to the control parameter and the sampled value of the output terminal specifically means: calculating the duty cycle according to the difference between the voltage in the control parameter and the sampled value of the voltage at the output terminal.

[0015] Preferably, controlling the on and off of each switch tube according to the control parameter and the duty cycle includes:

[0016] The energy transfer direction is controlled according to the duty cycle, and the on / off of the synchronous rectifier is determined according to the output current.

[0017] Each switching tube cycle includes 3 switching modes;

[0018] When the energy transfer direction indicates that the first end is the input end, the first mode is a boost charging mode, and the first, third, and fifth switching tubes are turned on; the second mode is a boost discharge and buck charging mode, and the first, third, fourth, and sixth switching tubes are turned on; the third mode is a buck discharge mode, and the second, fourth, and sixth switching tubes are turned on;

[0019] When the energy transfer direction indicates that the second end is the input end, the first mode is the boost charging mode, and the second, fourth, and sixth switching tubes are turned on; the second mode is the boost discharge and buck charging mode, and the first, third, fourth, and sixth switching tubes are turned on; the third mode is the buck discharge mode, and the first, third, and fifth switching tubes are turned on.

[0020] Preferably, if the difference between the positive current of the output terminal and the negative current of the output terminal in the monitoring loop exceeds a preset threshold, the specific method of cutting off the connection between the negative electrode of the input terminal and the negative electrode of the output terminal by turning off the switch tube is:

[0021] The currents flowing through the first inductor and the second inductor are monitored simultaneously. When the difference between the currents flowing through the first inductor and the second inductor exceeds a preset threshold, the connection between the negative electrode of the input terminal and the negative electrode of the output terminal is cut off by controlling the on and off of the power tube.

[0022] The present invention has the following beneficial effects: This solution adds two additional switching tubes and an inductor to the four-switch buck-boost boost-boost circuit, and separates the input and output negative poles by the additional switching tubes and inductors, thereby effectively solving the problem of the negative bus being directly connected to form a loop current when different input sources and outputs of the bidirectional buck-boost boost-boost circuit are connected in parallel; using the control method proposed in this solution, the loop does not need to judge the input and output voltage relationship, and automatically adjusts the duty cycle of the power switch tube according to the set voltage, current, and energy transfer direction. The calculation result of the duty cycle is used to determine the buck-boost state of the topology and to achieve control of the energy transfer direction, and the conduction and shutdown of the synchronous rectifier tube is determined by the magnitude of the output current. The solution of the embodiment of the present invention can solve the loop current problem caused by the difference in multiple inputs, effectively reduce circuit loss, improve the efficiency of the topology, reduce the control difficulty of the topology, and improve the fault tolerance of the control. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 The figure is a schematic diagram of a two-switch buck-boost step-up / down voltage topology circuit in the prior art.

[0025] Figure 2 The figure is a schematic diagram of a four-switch buck-boost step-up / down topology circuit in the prior art.

[0026] Figure 3 This is a schematic diagram of the prior art four-switch buck-boost buck-boost topology with multiple PFC input sources in parallel.

[0027] Figure 4 Schematic diagram of a bidirectional six-switch buck-boost topology circuit provided by an embodiment of the present invention.

[0028] Figure 5 This is a flow chart of a bidirectional six-switch buck-boost topology circuit control method provided by an embodiment of the present invention.

[0029] Figure 6 The embodiment of the present invention provides Figure 4 The switching tube control timing diagram of the circuit in the forward output state.

[0030] Figure 7 for Figure 6 Corresponding first modal equivalent circuit diagram.

[0031] Figure 8 for Figure 6 Schematic diagram of the corresponding second modal equivalent circuit.

[0032] Figure 9 for Figure 6 Corresponding third mode equivalent circuit diagram. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] The embodiments of the present invention are described in further detail below in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0035] The bidirectional six-switch buck-boost topology circuit provided in the embodiment of the present invention can be used in scenarios where energy storage batteries are charged under various bus input conditions in new energy fields such as (photovoltaic) storage and charging and (photovoltaic) storage.

[0036] like Figure 4 As shown, an embodiment of the present invention provides a bidirectional six-switch buck-boost topology circuit, which is connected between a first terminal V_energy storage and a second terminal V_BUS. The input and output directions of the first terminal V_energy storage and the second terminal V_BUS can be adjusted. The bidirectional six-switch buck-boost topology circuit includes: a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a first inductor L1, and a second inductor L2.

[0037] The gates of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5, and the sixth switch tube Q6 are all connected to a control system through a drive circuit;

[0038] The drain of the first switching tube Q1 is connected to the first positive electrode V_Storage+, the source of the first switching tube Q1 is respectively connected to one end of the first inductor L1 and the drain of the second switching tube Q2, the source of the second switching tube Q2 is respectively connected to one end of the second inductor L2 and the drain of the third switching tube Q3, the source of the third switching tube Q3 is connected to the first negative electrode V_Storage-, the source of the fourth switching tube Q4 is connected to the second negative electrode V_BUS-, the drain of the fourth switching tube Q4 is respectively connected to the other end of the second inductor L2 and the source of the fifth switching tube Q5, the drain of the fifth switching tube Q5 is respectively connected to the other end of the first inductor L1 and the source of the sixth switching tube Q6, and the drain of the sixth switching tube Q6 is connected to the second positive electrode V_BUS+.

[0039] The bidirectional six-switch buck-boost topology circuit provided in the embodiment of the present invention is an improvement on the traditional four-switch buck-boost topology circuit. Two switching tubes and an inductor are added between the negative electrode of the input end and the negative electrode of the output end. The voltage difference at the negative electrode of the output end between different PFC circuits can be controlled by adjusting the energy transfer of the added switching tubes and inductors to control the current at the negative electrode of the input end, thereby suppressing the negative bus circulating current.

[0040] The first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5, and the sixth switch tube Q6 are MOS tubes, IGBTs, SICMOS, or GaN MOS tubes. Figure 4As shown, in the embodiment of the present invention, the above-mentioned switch tube is an NMOS tube, which can also be replaced by a PMOS tube. Its circuit connection method is slightly different from that of the NMOS tube. Figure 4 In the MOSFET, the diode between the source and drain of each switch tube is the body diode of the MOS tube.

[0041] like Figure 4 As shown, in some embodiments of the present invention, a capacitor is connected in parallel between the drain of the first switch Q1 and the source of the third switch Q3, and a capacitor is connected in parallel between the drain of the sixth switch Q6 and the source of the fourth switch Q4. In practical applications, capacitors can be selected based on the required capacitance value for testing, or additional parallel capacitors can be added.

[0042] like Figure 4 As shown, in some embodiments of the present invention, the bidirectional six-switch buck-boost topology circuit also includes a common-mode inductor L3, a first connection end of the common-mode inductor L3 is connected to the first-end positive electrode V_energy storage+, a second connection end of the common-mode inductor L3 is connected to the drain of the first switch tube Q1, a third connection end of the common-mode inductor L3 is connected to the first-end negative electrode V_energy storage-, and a fourth connection end of the common-mode inductor L3 is connected to the source of the third switch tube Q3.

[0043] An embodiment of the present invention further provides a control method for the bidirectional six-switch buck-boost topology circuit as described above, comprising:

[0044] Receive control parameters sent from the outside, the control parameters including voltage, current, and energy transfer direction; calculate the duty cycle according to the control parameters and the sampled value of the output end, and control the on and off of each switch tube according to the control parameters and the duty cycle;

[0045] The positive current of the output end and the negative current of the output end in the monitoring loop are monitored. If the difference between the two exceeds a preset threshold, the connection between the negative pole of the input end and the negative pole of the output end is cut off by turning off the switch tube.

[0046] Voltage refers to the voltage at the output terminal, and current refers to the current at the output terminal. Current includes both magnitude and direction. The direction of energy transfer determines whether the energy is discharged from the first terminal V_energy storage to the second terminal V_BUS or charged from the second terminal V_BUS to the first terminal V_energy storage.

[0047] The process of the control method provided by the embodiment of the present invention is as follows Figure 5As shown, the difference between the traditional buck-boost control method of the buck-boost circuit mainly lies in two aspects of "duty cycle calculation" and "controlling the power switch tube with the actual calculated duty cycle". The control method provided by the embodiment of the present application is a kind of control method without intermediate state based on the six-switch buck-boost topology circuit. The special part is that the loop does not need to judge the relationship between the input and output voltages, but directly adjusts the duty cycle of the power switch tube according to the set voltage, current and energy transmission direction, and automatically adjusts the BUCK and BOOST modes according to the size of the duty cycle. When the topology is output in the forward direction, the fifth switch tube Q5 is the main switch tube when the voltage needs to be boosted, and the first switch tube Q1 and the third switch tube Q3 are the main switch tubes when the voltage needs to be reduced. The second switch tube Q2, the fourth switch tube Q4 and the sixth switch tube Q6 are synchronous rectifier tubes. When in the critical state, the main switch tube automatically adjusts the duty cycle according to the boost and buck requirements, realizes the seamless connection state of BUCK and BOOST, and adjusts the energy transmission of the parallel energy storage port under different bus voltages by monitoring the circulating current and controlling the state of the switch tube. The principle of the topology output in the reverse direction is the same as that of the forward direction.

[0048] Specifically, the duty cycle is calculated according to the difference between the voltage in the control parameter and the sampling value of the output end. The traditional BUCK, BOOST and BUCK-BOOST three-mode control method needs to judge the input and output voltages, and also needs to do the difference control. The control method of the embodiment of the present application directly calculates the difference between the sampling value and the set value in the loop to calculate the duty cycle. Compared with the traditional BUCK, BOOST and BUCK-BOOST three-mode control method, the scheme of the embodiment does not need to process the intermediate state process, so that the control and calculation are simpler, the control difficulty of the topology is reduced, and the fault tolerance of the control is improved. Compared with the traditional single-mode BUCK-BOOST control, the current flowing through the inductor and the tube can be reduced, the stress of the upper and lower tubes can be reduced, the conduction loss and switching loss of the tube can be reduced, and the efficiency of the topology can be improved. Compared with the traditional two-mode control, the current ripple of the control is smaller.

[0049] Specifically, as shown in the figure, Figure 6-Figure 9 In the embodiment of the present application, the control of the on-off of each switch tube according to the control parameter and the duty cycle includes:

[0050] The control of the energy transmission direction is realized according to the duty cycle, and the conduction and turn-off of the synchronous rectifier tube is determined according to the size of the output current;

[0051] Each switch tube period includes three switch modes;

[0052] When the energy transfer direction indicates that the first end is the input end, the first mode is the boost charging mode, and the first switch tube Q1, the third switch tube Q3, and the fifth switch tube Q5 are turned on; the second mode is the boost discharge and buck charging mode, and the first switch tube Q1, the third switch tube Q3, the fourth switch tube Q4, and the sixth switch tube Q6 are turned on; the third mode is the buck discharge mode, and the second switch tube Q2, the fourth switch tube Q4, and the sixth switch tube Q6 are turned on.

[0053] like Figure 6 As shown, t0-t1 is the boost charging mode, and the circuit equivalent schematic diagram is as follows Figure 7 As shown, at this time, the first switch tube Q1, the third switch tube Q3, and the fifth switch tube Q5 are turned on, and the negative electrode of the input terminal and the negative electrode of the output terminal are disconnected. t1-t2 is both a boost discharge mode and a buck charge mode. The circuit equivalent diagram is shown in FIG. Figure 8 As shown, at this time, the first switch tube Q1, the third switch tube Q3, the fourth switch tube Q4, and the sixth switch tube Q6 are turned on, and the negative electrode of the input end and the negative electrode of the output end are connected together through the third switch tube Q3, the second inductor L2, and the fourth switch tube Q4. t2-t3 is the step-down discharge mode, and the circuit equivalent diagram is shown in FIG. Figure 9 As shown, at this time, the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are turned on, and the negative electrodes of the input and output terminals are disconnected. The first and third modes are the primary operating states, while the second mode is a transitional state. The time proportions of the three modes can be adjusted as needed. Because the inductor current cannot change suddenly, it can still continue to flow after switching from the second mode to the third mode.

[0054] When the energy transfer direction indicates that the second end is the input end, the first mode is the boost charging mode, and the second, fourth, and sixth switching tubes are turned on; the second mode is the boost discharge and buck charging mode, and the first, third, fourth, and sixth switching tubes are turned on; the third mode is the buck discharge mode, and the first, third, and fifth switching tubes are turned on.

[0055] In an embodiment of the present invention, if the difference between the positive current at the output end and the negative current at the output end in the monitoring loop exceeds a preset threshold, the specific method for cutting off the connection between the negative electrode of the input end and the negative electrode of the output end by turning off the switch tube is:

[0056] The current flowing through the first inductor and the second inductor is monitored simultaneously. When the difference between the current flowing through the first inductor and the second inductor exceeds a preset threshold, the connection between the negative electrode of the input terminal and the negative electrode of the output terminal is cut off by controlling the on and off of the power tube. The preset threshold is set according to specific circumstances.

[0057] from Figure 7-Figure 9It can be seen that in the three modes, the first inductor L1 and the second inductor L2 are always interconnected. In some embodiments of the present invention, current is continuously collected from these two inductors. When the currents passing through them are inconsistent, the circulating current can be cut off by disconnecting the third switch tube Q3 or the fourth switch tube Q4. For example, by controlling the on and off of each switch tube, switching from the second mode to the third mode.

[0058] The present invention has the following beneficial effects: This solution adds two additional switching tubes and an inductor to the four-switch buck-boost boost-boost circuit, and separates the input and output negative poles by the additional switching tubes and inductors, thereby effectively solving the problem of the negative bus being directly connected to form a loop current when different input sources and outputs of the bidirectional buck-boost boost-boost circuit are connected in parallel; using the control method proposed in this solution, the loop does not need to judge the input and output voltage relationship, and automatically adjusts the duty cycle of the power switch tube according to the set voltage, current, and energy transfer direction. The calculation result of the duty cycle is used to determine the buck-boost state of the topology and to achieve control of the energy transfer direction, and the conduction and shutdown of the synchronous rectifier tube is determined by the magnitude of the output current. The solution of the embodiment of the present invention can solve the loop current problem caused by the difference in multiple inputs, effectively reduce circuit loss, improve the efficiency of the topology, reduce the control difficulty of the topology, and improve the fault tolerance of the control.

[0059] The above is only a specific embodiment of the present invention and cannot be used to limit the scope of the present invention. Equal changes made by ordinary technicians in this technical field based on this creation, as well as changes well known to technicians in this field, should still fall within the scope of the present invention.

Claims

1. A bidirectional six-switch buck-boost topology circuit, characterized in that: The bidirectional six-switch buck-boost topology circuit is connected between a first terminal and a second terminal, and the input and output directions of the first terminal and the second terminal are adjustable. The bidirectional six-switch buck-boost topology circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, and a second inductor; The gates of the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube, and the sixth switching tube are all connected to a control system through a driving circuit; The drain of the first switching tube is connected to the positive electrode of the first end, the source of the first switching tube is respectively connected to one end of the first inductor and the drain of the second switching tube, the source of the second switching tube is respectively connected to one end of the second inductor and the drain of the third switching tube, the source of the third switching tube is connected to the negative electrode of the first end, the source of the fourth switching tube is connected to the negative electrode of the second end, the drain of the fourth switching tube is respectively connected to the other end of the second inductor and the source of the fifth switching tube, the drain of the fifth switching tube is respectively connected to the other end of the first inductor and the source of the sixth switching tube, and the drain of the sixth switching tube is connected to the positive electrode of the second end.

2. The bidirectional six-switch buck-boost topology circuit according to claim 1, characterized in that: The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are IGBTs, SICMOSs, or gallium nitride MOSs.

3. The bidirectional six-switch buck-boost topology circuit according to claim 2, characterized in that: A capacitor is connected in parallel between the drain of the first switching tube and the source of the third switching tube, and a capacitor is connected in parallel between the drain of the sixth switching tube and the source of the fourth switching tube.

4. The bidirectional six-switch buck-boost topology circuit according to claim 2, characterized in that: The bidirectional six-switch buck-boost topology circuit also includes a common-mode inductor, a first connection end of the common-mode inductor connected to the positive electrode of the first end, a second connection end of the common-mode inductor connected to the drain of the first switch tube, a third connection end of the common-mode inductor connected to the negative electrode of the first end, and a fourth connection end of the common-mode inductor connected to the source of the third switch tube.

5. A control method for a bidirectional six-switch buck-boost topology circuit according to any one of claims 1 to 4, characterized in that: include: Receive control parameters sent from the outside, including voltage, current, and energy transfer direction; Calculating a duty cycle according to the control parameter and the sampled value of the output terminal, and controlling the on and off of each switch tube according to the control parameter and the duty cycle; The positive current of the output end and the negative current of the output end in the monitoring loop are monitored. If the difference between the two exceeds a preset threshold, the connection between the negative pole of the input end and the negative pole of the output end is cut off by turning off the switch tube.

6. The control method of the bidirectional six-switch buck-boost topology circuit according to claim 5, characterized in that: Calculating the duty cycle according to the control parameter and the sampled value of the output terminal specifically refers to calculating the duty cycle according to the difference between the voltage in the control parameter and the sampled value of the output terminal.

7. The control method of the bidirectional six-switch buck-boost topology circuit according to claim 6, characterized in that: The controlling the on and off of each switch tube according to the control parameter and the duty cycle includes: The energy transfer direction is controlled according to the duty cycle, and the on / off of the switch tube is determined according to the output current; Each switching tube cycle includes 3 switching modes; When the energy transfer direction indicates that the first end is the input end, the first mode is a boost charging mode, and the first, third, and fifth switching tubes are turned on; the second mode is a boost discharge and buck charging mode, and the first, third, fourth, and sixth switching tubes are turned on; the third mode is a buck discharge mode, and the second, fourth, and sixth switching tubes are turned on; When the energy transfer direction indicates that the second end is the input end, the first mode is the boost charging mode, and the second, fourth, and sixth switching tubes are turned on; the second mode is the boost discharge and buck charging mode, and the first, third, fourth, and sixth switching tubes are turned on; the third mode is the buck discharge mode, and the first, third, and fifth switching tubes are turned on.

8. The control method of the bidirectional six-switch buck-boost topology circuit according to claim 7, characterized in that: The specific method of cutting off the connection between the negative electrode of the input terminal and the negative electrode of the output terminal by turning off the switch tube is as follows: The currents flowing through the first inductor and the second inductor are monitored simultaneously. When the difference between the currents flowing through the first inductor and the second inductor exceeds a preset threshold, the connection between the negative electrode of the input terminal and the negative electrode of the output terminal is cut off by controlling the switch tube to be turned off.

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