Bidirectional six-switch buck-boost topology circuit and control method thereof

Abstract

The invention discloses a bidirectional six-switch buck-boost topology circuit and a control method thereof, and belongs to the technical field of power electronics. According to the scheme, two switch tubes and one inductor are additionally arranged on the basis of a four-switch buck-boost circuit, and an input negative electrode and an output negative electrode are separated through the additionally arranged switch tubes and inductor, so that the problem that when different input source outputs are connected in parallel, a negative bus is directly connected to form circulating current is effectively solved; a loop does not need to judge an input and output voltage relation, the duty ratio of a power switch tube is automatically adjusted directly according to the set voltage, current and energy transfer direction, and the boost-buck state of the topology is determined according to the calculation result of the duty ratio, so that the control on the energy transfer direction is realized; the on / off of the synchronous rectifier tube is determined by the magnitude of the output current. By adopting the scheme of the embodiment of the invention, the circulating current problem caused by multi-path input difference can be solved, the topology control difficulty is reduced, and the control error-tolerant rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, 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 1, 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 is simple in structure, it has significant problems in multi-channel parallel applications. Figure 3 As shown in the figure, when a four-switch buck-boost buck-boost topology is used, if multiple PFC (Power Factor Correction) circuits are operated in parallel as input sources, the negative poles of the output terminals of multiple buck-boost buck-boost circuits are connected, and the negative poles of the buses of multiple PFC circuits are also directly connected together. If the DC bus output voltages input to the PFC circuit are inconsistent, the potentials at the midpoints of the bridge arms of the PFC circuits will be different. Through the directly connected negative bus, these potential differences will gradually generate currents, thereby forming differential-mode currents between modules. This differential-mode current will not only prevent normal parallel operation, but may also cause overcurrent output, ultimately leading to damage to components such as switch tubes and fuses.

[0003] Therefore, in order to solve the circulation problem when multiple buck-boost boost and buck-boost 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-mentioned object, 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 end and a second end, and the input and output directions of the first end and the second end can be adjusted, and the bidirectional six-switch buck-boost topology circuit comprises: 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 switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are all connected to a control system through a driving circuit;

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

[0009] Preferably, a capacitor is connected in parallel between the drain of the first switch tube and the source of the third switch tube, and a capacitor is connected in parallel between the drain of the sixth switch tube and the source of the fourth switch 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 is connected to the positive electrode of the first end, a second connection end of the common-mode inductor is connected to the drain of the first switch tube, a third connection end of the common-mode inductor is connected to the negative electrode of the first end, and a fourth connection end of the common-mode inductor is 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 as described above, comprising:

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

[0013] The positive current at the output end and the negative current at the output end in the monitoring loop are monitored. If the difference between the two exceeds a preset threshold, the connection between the negative electrode of the input end and the negative electrode 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 and 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 switch tube, the third switch tube, and the fifth switch tube are turned on; the second mode is a boost discharge and buck charging mode, and the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned on; the third mode is a buck discharge mode, and the second switch tube, the fourth switch tube, and the sixth switch tube 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 switch tube, the fourth switch tube, and the sixth switch tube are turned on; the second mode is the boost discharge and buck charging mode, and the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned on; the third mode is the buck discharge mode, and the first switch tube, the third switch tube, and the fifth switch tube are turned on.

[0020] Preferably, 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 of cutting off the connection between the negative electrode at the input end and the negative electrode at the output end 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 scheme adds two additional switch tubes and an inductor on the basis of the four-switch buck-boost buck-boost circuit, and separates the input and output negative poles by the additional switch tubes and inductors, thereby effectively solving the problem of the negative busbar directly connected to form a circulating current when different input sources and outputs of the bidirectional buck-boost buck-boost circuit are connected in parallel; using the control method proposed in this scheme, the loop does not need to judge the input-output voltage relationship, and automatically adjusts the duty cycle of the power switch tube according to the set voltage, current, and energy transfer direction, and determines the buck-boost state of the topology and realizes the control of the energy transfer direction according to the calculation result of the duty cycle, and determines the conduction and shutdown of the synchronous rectifier tube by the size of the output current. The scheme of the embodiment of the present invention can solve the circulating current problem caused by the difference in multi-channel input, 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 schematic diagram of the prior art two-switch buck-boost boost-down topology circuit is shown in FIG.

[0025] Figure 2 The schematic diagram of the prior art four-switch buck-boost boost-down topology circuit is shown in FIG.

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

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

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

[0029] Figure 6 The embodiment of the present invention provides Figure 4 The switch tube control timing diagram when the circuit in is outputting forward.

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

[0031] Figure 8 for Figure 6 The corresponding second mode equivalent circuit diagram.

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

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the specification. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, and are not used 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 of charging energy storage batteries 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, the topology circuit 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, and 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 the control system through a driving circuit;

[0038] The drain of the first switch tube Q1 is connected to the first positive electrode V_energy storage+, the source of the first switch tube Q1 is respectively connected to one end of the first inductor L1 and the drain of the second switch tube Q2, the source of the second switch tube Q2 is respectively connected to one end of the second inductor L2 and the drain of the third switch tube Q3, the source of the third switch tube Q3 is connected to the first negative electrode V_energy storage-, the source of the fourth switch tube Q4 is connected to the second negative electrode V_BUS-, the drain of the fourth switch tube Q4 is respectively connected to the other end of the second inductor L2 and the source of the fifth switch tube Q5, the drain of the fifth switch tube Q5 is respectively connected to the other end of the first inductor L1 and the source of the sixth switch tube Q6, and the drain of the sixth switch 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 improved on the basis of the traditional four-switch buck-boost 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 of the negative electrode of the output end between different PFC circuits can be controlled by adjusting the energy transfer of the added switching tube and the inductor to control the current of 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 one of MOS tubes, IGBTs, SICMOS, and gallium nitride MOS. Figure 4As shown, in the embodiment of the present invention, the switch tube is an NMOS tube, and can also be replaced by a PMOS tube, and its circuit connection method is slightly different from that of the NMOS tube. Figure 4 In the circuit, 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 tube Q1 and the source of the third switch tube Q3, and a capacitor is connected in parallel between the drain of the sixth switch tube Q6 and the source of the fourth switch tube Q4. In practical applications, capacitors can be selected according to the capacitance required for testing, or 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 positive electrode V_energy storage+ of the first end, 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 negative electrode V_energy storage- of the first end, and a fourth connection end of the common-mode inductor L3 is connected to the source of the third switch tube Q3.

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

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

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

[0046] Voltage refers to the voltage at the output end, and current refers to the current at the output end, which includes magnitude and direction. The energy transfer direction determines whether the energy is discharged from the first end V_energy storage to the second end V_BUS or charged from the second end V_BUS to the first end 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 from the traditional buck-boost boost and buck circuit control method is mainly reflected in the two links 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 invention is a control method without intermediate state based on the six-switch boost and buck topology circuit of the present invention. Its special feature is that 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, and automatically adjusts the BUCK and BOOST modes according to the size of the duty cycle. When the topology is outputting in the forward direction, when boosting is required, the fifth switch tube Q5 is the main switch tube, and when bucking is required, the first switch tube Q1 and the third switch tube Q3 are the main switch tubes, and the second switch tube Q2, the fourth switch tube Q4, and the sixth switch tube Q6 are synchronous rectifier tubes. When in a critical state, the main switch tube automatically adjusts the duty cycle wave according to the boost and buck requirements to achieve a seamless connection state of BUCK and BOOST. At the same time, by monitoring the circulating current and controlling the state of the switch tube, the energy transfer that occurs in parallel when the energy storage port is connected at different bus voltages can be adjusted. The principle of topological reverse output is the same as that of forward output.

[0048] Specifically, 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. The traditional BUCK, BOOST and BUCK-BOOST three-mode control method requires judging the input and output voltages, and also performing hysteresis control, while the control method of the embodiment of the present invention directly loops and calculates the difference between the sampled value and the set value to calculate the duty cycle. Compared with the traditional BUCK, BOOST and BUCK-BOOST three-mode control method, the scheme of this embodiment does not need to process the intermediate state process, making the control and calculation simpler, reducing the control difficulty of the topology, and improving the fault tolerance of the control. Compared with the traditional single-mode BUCK-BOOST control, it can reduce the current flowing through the inductor and the tube, reduce the stress of the upper and lower tubes, and reduce the conduction loss and switching loss of the tube, which can improve the efficiency of the topology. Compared with the traditional two-mode, the controlled current ripple will be smaller.

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

[0050] The energy transfer direction is controlled according to the duty cycle, and the on and off of the synchronous rectifier is determined according to the output current;

[0051] Each switching tube cycle includes 3 switching 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 charging mode. The circuit equivalent schematic diagram is shown in 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 schematic diagram is as follows Fig. 9 As shown, at this time, the second switch tube Q2, the fourth switch tube Q4, and the sixth switch tube Q6 are turned on, and the negative electrode of the input terminal and the negative electrode of the output terminal are disconnected. Among them, the first mode and the third mode are the main working states, and the second mode is a transition state. The time proportion of the three modes can be adjusted as needed, because the current of the inductor cannot change suddenly, and after switching from the second mode to the third mode, it can still continue to flow.

[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 switch tubes are turned on; the second mode is the boost discharge and buck charging mode, and the first, third, fourth and sixth switch tubes are turned on; the third mode is the buck discharge mode, and the first, third and fifth switch tubes are turned on.

[0055] In the embodiment of the present invention, 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:

[0056] The current flowing through the first inductor and the second inductor is monitored at the same time, and when the difference between the two 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 scheme adds two additional switch tubes and an inductor on the basis of the four-switch buck-boost buck-boost circuit, and separates the input and output negative poles by the additional switch tubes and inductors, thereby effectively solving the problem of the negative busbar directly connected to form a circulating current when different input sources and outputs of the bidirectional buck-boost buck-boost circuit are connected in parallel; using the control method proposed in this scheme, the loop does not need to judge the input-output voltage relationship, and automatically adjusts the duty cycle of the power switch tube according to the set voltage, current, and energy transfer direction, and determines the buck-boost state of the topology and realizes the control of the energy transfer direction according to the calculation result of the duty cycle, and determines the conduction and shutdown of the synchronous rectifier tube by the size of the output current. The scheme of the embodiment of the present invention can solve the circulating current problem caused by the difference in multi-channel input, 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 are only specific implementations of the present invention, which cannot be used to limit the scope of the present invention. Equivalent changes made by ordinary technicians in this technical field based on this creation, as well as changes 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 topology circuit is connected between the first end and the second end, the input and output directions of the first end and the second end can be adjusted, and 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 switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are all connected to a control system through a driving circuit; The drain of the first switch tube is connected to the positive electrode of the first end, the source of the first switch tube is respectively connected to one end of the first inductor and the drain of the second switch tube, the source of the second switch tube is respectively connected to one end of the second inductor and the drain of the third switch tube, the source of the third switch tube is connected to the negative electrode of the first end, the source of the fourth switch tube is connected to the negative electrode of the second end, the drain of the fourth switch tube is respectively connected to the other end of the second inductor and the source of the fifth switch tube, the drain of the fifth switch tube is respectively connected to the other end of the first inductor and the source of the sixth switch tube, and the drain of the sixth switch 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 one of MOS tubes, IGBTs, SICMOS, and gallium nitride MOS.

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 switch tube and the source of the third switch tube, and a capacitor is connected in parallel between the drain of the sixth switch tube and the source of the fourth switch 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 is connected to the positive electrode of the first end, a second connection end of the common-mode inductor is connected to the drain of the first switch tube, a third connection end of the common-mode inductor is connected to the negative electrode of the first end, and a fourth connection end of the common-mode inductor is 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: Receiving control parameters sent from outside, wherein the control parameters include voltage, current, and energy transfer direction; Calculating the duty cycle according to the control parameter and the sampling 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 at the output end and the negative current at the output end in the monitoring loop are monitored. If the difference between the two exceeds a preset threshold, the connection between the negative electrode of the input end and the negative electrode 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 means: 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 and off of the synchronous rectifier 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 switch tube, the third switch tube, and the fifth switch tube are turned on; the second mode is a boost discharge and buck charging mode, and the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned on; the third mode is a buck discharge mode, and the second switch tube, the fourth switch tube, and the sixth switch tube 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 switch tube, the fourth switch tube, and the sixth switch tube are turned on; the second mode is the boost discharge and buck charging mode, and the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned on; the third mode is the buck discharge mode, and the first switch tube, the third switch tube, and the fifth switch tube 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 on and off of the power tube.

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