Charging and discharging circuit and uninterruptible power supply

Abstract

The present application relates to the technical field of power electronics, and provides a charging and discharging circuit and an uninterruptible power supply. The uninterruptible power supply comprises a rectifier circuit, an inverter circuit, a charging and discharging circuit, a positive bus, and a negative bus. An input end of the rectifier circuit is configured to be connected to an alternating current power supply, an output end of the rectifier circuit is connected to an input end of the inverter circuit by means of the positive bus and the negative bus, an input end of the charging and discharging circuit is configured to be connected to an energy storage apparatus, and an output end of the charging and discharging circuit is connected to the positive bus and the negative bus. The charging and discharging circuit is configured to charge and discharge the energy storage apparatus. When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to a first threshold, a switching action in the charging and discharging circuit is controlled to adjust the voltage difference between the positive bus and the negative bus to be less than the first threshold so as to achieve voltage balance between the positive bus and the negative bus. In the present application, the charging and discharging circuit is reused to regulate the voltages of the positive and negative buses to achieve voltage balance, thereby simplifying a circuit design and improving the space utilization rate of the uninterruptible power supply.

Description

A charging and discharging circuit and an uninterruptible power supply

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510209655.8, filed on February 24, 2025, entitled “A Charging and Discharging Circuit and an Uninterruptible Power Supply”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of power electronics technology, and in particular to a charging and discharging circuit and an uninterruptible power supply. Background Technology

[0004] An uninterruptible power supply (UPS) is a system that provides uninterrupted power to electronic equipment. A UPS contains an internal energy storage device. When the mains power is normal, the UPS converts the mains voltage to the load's supply voltage and provides it to the load. When the mains power fails, the UPS converts the voltage stored in the energy storage device back into the supply voltage and provides it to the load, thus ensuring reliable power supply.

[0005] A UPS mainly consists of a rectifier circuit, a positive bus, a negative bus, a DC / AC inverter circuit, and a DC / DC charging / discharging circuit. When powered by mains electricity, the rectifier circuit converts the received power and outputs it to the positive and negative buses. When powered by an energy storage device, the DC / DC charging / discharging circuit converts the DC power output from the energy storage device and outputs it to the positive and negative buses. The inverter circuit converts the DC power on the positive and negative buses into AC power and outputs it to the load, thus improving the UPS efficiency. In practice, the positive and negative buses may be unbalanced due to different power demands from the load. A balancing circuit is needed in the UPS to regulate the power between the positive and negative buses. Furthermore, the DC / DC charging / discharging circuit is always operational when powered by the energy storage device. The power of the DC / DC charging / discharging circuit must meet the rated power of the UPS system, resulting in a larger circuit size and disadvantages in terms of cost and space. Summary of the Invention

[0006] This application provides an uninterruptible power supply that reduces circuit size and improves space utilization by combining the DC / DC charging and discharging circuit and the balancing circuit into one.

[0007] In a first aspect, this application provides an uninterruptible power supply (UPS), comprising: a rectifier circuit, an inverter circuit, a charging / discharging circuit, a positive bus, and a negative bus. The input terminal of the rectifier circuit is connected to an AC power source, and the output terminal of the rectifier circuit is connected to the input terminal of the inverter circuit via the positive and negative buses. The input terminal of the charging / discharging circuit is connected to an energy storage device, and the output terminal of the charging / discharging circuit is connected to the positive and negative buses. When the AC power source supplies power to the load, the rectifier circuit receives a first AC current output from the AC power source and converts it into a first DC current for output to the inverter circuit. The inverter circuit converts the first DC current into a second AC current for output to the load. When the energy storage device supplies power to the load, the charging / discharging circuit receives a second DC current output from the energy storage device and converts it into a third DC current for output to the inverter circuit. The inverter circuit converts the third DC current into a third AC current for output to the load. When the absolute value of the voltage difference between the positive and negative buses is greater than or equal to a first threshold, the charging / discharging circuit controls the switching action in the charging / discharging circuit to adjust the voltage difference between the positive and negative buses to be less than the first threshold. When the positive and negative bus voltages are unbalanced, the voltage of the positive and negative bus can be regulated by controlling the switching action in the charging and discharging circuit to achieve voltage balance, which simplifies the circuit design and improves the space utilization of the uninterruptible power supply.

[0008] In one possible implementation, when the energy storage device receives electrical energy from an AC power source, the charging and discharging circuit is used to receive the first DC power output from the rectifier circuit through the positive and negative buses and convert the first DC power into a fourth DC power output to the energy storage device. When the AC power source is normal, the energy storage device can be powered by the AC power source, so that when the AC power source fails, the energy storage device can power the load through the charging and discharging circuit and the inverter circuit.

[0009] In one possible implementation, the charging / discharging circuit includes a positive bus capacitor and a negative bus capacitor, a first inductor, a second inductor, a first diode, a second diode, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, and a third switching transistor. The circuit formed by the series connection of the positive and negative bus capacitors is connected in parallel with the circuit formed by the series connection of the first, second, and third switching transistors. The input terminals of the charging / discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first and second switching transistors through the first switching switch and the first inductor. The negative input terminal is connected to the connection point of the second and third switching transistors through the second switching switch and the second inductor. The first and second diodes are connected in series. The cathode of the first diode is connected to the connection point of the first switching switch and the first inductor, and the anode of the second diode is connected to the connection point of the second switching switch and the second inductor. The balancing circuit reuses the charging / discharging circuit, resulting in a simple circuit structure design. During the charging and discharging process of the energy storage device, the charging / discharging circuit plays a power conversion role. When the positive and negative bus voltages are unbalanced, the charging and discharging circuit can balance the voltage, saving the volume of the uninterruptible power supply and improving space utilization.

[0010] In one possible implementation, when the absolute value of the voltage difference between the positive and negative busbars is greater than or equal to a first threshold, the first and second switching switches are disconnected. At this time, the charging and discharging circuit operates in equilibrium. Further, when the difference between the absolute values ​​of the positive and negative busbar voltages is greater than or equal to a second threshold, the positive busbar voltage is too high. The first and second switching transistors operate synchronously, while the third switching transistor remains inactive. Energy in the positive busbar is released to the second inductor, thereby reducing the voltage difference between the positive and negative busbars. And / or, when the difference between the absolute values ​​of the negative and positive busbar voltages is greater than or equal to a third threshold, the negative busbar voltage is too high. The second and third switching transistors operate synchronously, while the first switching transistor remains inactive. Energy in the negative busbar is released to the first inductor, thereby reducing the voltage difference between the negative and positive busbars.

[0011] In one possible implementation, the charging / discharging circuit includes a first capacitor, a second capacitor, a first inductor, a second inductor, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a fifth switching transistor. The circuit formed by the series connection of the first and second capacitors is connected in parallel with the circuit formed by the series connection of the first, second, and third switching transistors. The input terminals of the charging / discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first and second switching transistors through the first switching switch and the first inductor. The negative input terminal is connected to the connection point of the second and third switching transistors through the second switching switch and the second inductor. The fourth and fifth switching transistors are connected in series between the connection point of the first switching switch and the first inductor and the connection point of the second switching switch and the second inductor. The balancing circuit reuses the charging / discharging circuit, resulting in a simple circuit structure design. During the charging and discharging process of the energy storage device, the charging / discharging circuit plays a power conversion role. When the positive and negative bus voltages are unbalanced, the charging / discharging circuit can balance the voltage, saving the volume of the uninterruptible power supply and improving space utilization.

[0012] In one possible implementation, when the energy storage device receives electrical energy from an AC power source, the first and second switching switches are turned on, the first and third switching transistors operate synchronously, the second switching transistor is deactivated, and the charging / discharging circuit is in a charging state. The energy storage device receives electrical energy from the AC power source through the rectifier circuit and the charging / discharging circuit. And / or, when the energy storage device supplies power to a load, the first and second switching switches are turned on, the second switching transistor operates, the first and third switching transistors are deactivated, the charging / discharging circuit is in a discharging state, and the energy storage device provides electrical energy to the load through the charging / discharging circuit and the inverter circuit.

[0013] In one possible implementation, a third diode is connected in parallel across the two ends of the first switch, with the anode of the third diode connected to the connection point between the first switch and the first inductor. Similarly, a fourth diode is connected in parallel across the two ends of the second switch, with the cathode of the fourth diode connected to the connection point between the second switch and the second inductor. By utilizing the unidirectional conduction property of the diodes, backflow into the bus due to excessive current from the energy storage device during the charging / discharging process can be prevented, thus improving circuit safety.

[0014] In one possible implementation, the first and second switching switches are switching devices that include a body diode, such as a MOSFET or other equivalent switching device. Even if the first and second switching switches do not perform switching actions, the circuit can still be turned on by the internal body diode.

[0015] In one possible implementation, when the energy storage device receives electrical energy from an AC power source, the charging and discharging circuit is in a charging state. The first and second switching switches are open, the first and third switching transistors operate synchronously, and the second switching transistor remains inactive. When the charging and discharging circuit is in a charging state, the first and second switching switches are in a stable open state. The energy storage device can be charged through the third and fourth diodes. Since diodes have unidirectional conduction properties, if a battery failure causes the voltage of the energy storage device to be higher than the bus voltage, the diodes can prevent current backflow into the bus, improving circuit safety. And / or, when the energy storage device supplies power to a load, the charging and discharging circuit is in a discharging state. The first and second switching switches are on, the second switching transistor operates, and the first and third switching transistors remain inactive. The energy storage device provides electrical energy to the load through the charging and discharging circuit and the inverter circuit.

[0016] In one possible implementation, when the absolute value of the voltage difference between the positive and negative busbars is greater than or equal to a first threshold, the first and second switching switches are disconnected, and the charging and discharging circuit operates in a balanced state. When the difference between the absolute values ​​of the voltages of the positive and negative busbars is greater than or equal to a second threshold, the voltage of the positive busbar is too high. The first, second, and fifth switching transistors operate synchronously, while the third and fourth switching transistors remain inactive. Energy in the positive busbar is released to the second inductor, thereby reducing the voltage difference between the positive and negative busbars and balancing the voltages of the positive and negative busbars. When the difference between the absolute values ​​of the voltages of the negative and positive busbars is greater than or equal to a third threshold, the voltage of the negative busbar is too high. The second, third, and fourth switching transistors operate synchronously, while the first and fifth switching transistors remain inactive. Energy in the negative busbar is released to the first inductor, thereby reducing the voltage difference between the positive and negative busbars and balancing the voltages of the positive and negative busbars.

[0017] In one possible implementation, when the absolute value of the voltage difference between the positive and negative busbars is greater than or equal to a first threshold, the first and second switching switches are disconnected, and the charging and discharging circuit operates in a balanced state. When the difference between the absolute values ​​of the voltages of the positive and negative busbars is greater than or equal to a second threshold, the voltage of the positive busbar is too high. The first and second switching transistors operate synchronously, the fifth switching transistor is turned on, and the third and fourth switching transistors are not activated. Energy in the positive busbar is released to the second inductor, reducing the voltage difference between the positive and negative busbars. And / or, when the difference between the absolute values ​​of the voltages of the negative and positive busbars is greater than or equal to a second threshold, the voltage of the negative busbar is too high. The second and third switching transistors operate synchronously, the fourth switching transistor is turned on, and the first and fifth switching transistors are not activated. Energy in the negative busbar is released to the first inductor, thereby reducing the voltage difference between the negative and positive busbars and balancing the voltages of the positive and negative busbars.

[0018] In one possible implementation, when the absolute value of the voltage difference between the positive and negative busbars is greater than or equal to a first threshold, the first and second switching switches are disconnected. When the difference between the absolute values ​​of the voltages on the positive and negative busbars is greater than or equal to a second threshold, the voltage on the positive busbar is too high, and the first and second switching transistors operate synchronously, while the third, fourth, and fifth switching transistors remain inactive. Energy in the positive busbar is released to the second inductor, reducing the voltage difference between the positive and negative busbars. And / or, when the difference between the absolute values ​​of the voltages on the negative and positive busbars is greater than or equal to the second threshold, the voltage on the negative busbar is high, and the second and third switching transistors operate synchronously, while the first, fourth, and fifth switching transistors remain inactive. Energy in the negative busbar is released to the first inductor, thereby reducing the voltage difference between the negative and positive busbars and balancing the voltages on the positive and negative busbars.

[0019] In one possible implementation, when the absolute value of the voltage difference between the positive and negative busbars is greater than or equal to a first threshold, the first and second switching switches are disconnected. When the difference between the absolute values ​​of the voltages on the positive and negative busbars is greater than or equal to a second threshold, the first switch operates, and the second, fourth, and fifth switches are turned on, while the third switch remains inactive. Electrical energy in the positive busbar is released to the first and second inductors, thereby reducing the voltage difference between the positive and negative busbars and balancing the voltages of the positive and negative busbars. And / or, when the difference between the absolute values ​​of the voltages on the negative and positive busbars is greater than or equal to the second threshold, the negative busbar voltage is too high, the third switch operates, and the second, fourth, and fifth switches are turned on, while the first switch remains inactive. Electrical energy in the negative busbar is released to the first and second inductors, thereby reducing the voltage difference between the negative and positive busbars and balancing the voltages of the positive and negative busbars.

[0020] In one possible implementation, a first fuse and a second fuse are connected in series between the first diode and the second diode. When the current in the charging and discharging circuit is too high, the fuse melts due to excessive temperature, thereby cutting off the circuit and stopping the charging and discharging circuit from working, thus improving the safety of the circuit.

[0021] In one possible implementation, a third fuse is provided between the first switch and the positive input terminal, and a fourth fuse is provided between the second switch and the negative input terminal. Alternatively, a third fuse is provided between the first switch and the first inductor, and a fourth fuse is provided between the second switch and the second inductor. When the current in the charging / discharging circuit is too high, the fuses melt due to excessive temperature, thereby cutting off the circuit and stopping the charging / discharging circuit from working, thus improving the safety of the circuit.

[0022] In one possible implementation, a first Hall element is disposed between the first switch and the first inductor, and a second Hall element is disposed between the second switch and the second inductor. The first and second Hall elements can detect current, and when an abnormal current occurs in the circuit (such as excessive current or reverse current), they promptly disconnect the charging and discharging circuit, causing it to stop working and ensuring circuit safety.

[0023] Secondly, this application provides a charging and discharging circuit. The input terminal of the charging and discharging circuit is used to connect to an energy storage device, and the output terminal is used to connect to a positive bus and a negative bus. The charging and discharging circuit includes a positive bus capacitor and a negative bus capacitor, a first inductor, a second inductor, a first diode, a second diode, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, and a third switching transistor. The circuit formed by the series connection of the positive bus capacitor and the negative bus capacitor is connected in parallel with the circuit formed by the series connection of the first switching transistor, the second switching transistor, and the third switching transistor. The input terminal of the charging and discharging circuit includes a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through the first switching switch and the first inductor. The negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through the second switching switch and the second inductor. The first diode and the second diode are connected in series. The negative terminal of the first diode is connected to the connection point of the first switching switch and the first inductor, and the positive terminal of the second diode is connected to the connection point of the second switching switch and the second inductor.

[0024] Thirdly, embodiments of this application provide a charging and discharging circuit. The input terminal of the charging and discharging circuit is used to connect to an energy storage device, and the output terminal is used to connect to a positive bus and a negative bus. The charging and discharging circuit includes a first capacitor, a second capacitor, a first inductor, a second inductor, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a fifth switching transistor. The circuit formed by the series connection of the first capacitor and the second capacitor is connected in parallel with the circuit formed by the series connection of the first switching transistor, the second switching transistor, and the third switching transistor. The input terminal of the charging and discharging circuit includes a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through the first switching switch and the first inductor, and the negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through the second switching switch and the second inductor. The fourth switching transistor and the fifth switching transistor are connected in series between the connection point of the first switching switch and the first inductor and the connection point of the second switching switch and the second inductor. Attached Figure Description

[0025] Figure 1 is a schematic diagram of the structure of an uninterruptible power supply in the prior art;

[0026] Figure 2 is a schematic diagram of the structure of the uninterruptible power supply provided in an embodiment of this application;

[0027] Figure 3 is a schematic diagram of the charging and discharging circuit provided in an embodiment of this application;

[0028] Figures 3a to 3h are schematic diagrams illustrating the working principle of the charging and discharging circuit provided in the embodiments of this application under different conditions;

[0029] Figure 4 is a schematic diagram of the first working state of various switches in the charging and discharging circuit provided in the embodiment of this application;

[0030] Figures 5 to 7 are schematic diagrams of the charging and discharging circuit provided in the embodiments of this application;

[0031] Figures 6a to 6d are schematic diagrams illustrating the working principle of the charging and discharging circuit provided in Figure 6 under different conditions in the embodiments of this application.

[0032] Figures 7a to 7l are schematic diagrams illustrating the working principle of the charging and discharging circuit provided in Figure 7 under different conditions in the embodiments of this application.

[0033] Figure 8 is a schematic diagram of the second working state of various switches in the charging and discharging circuit provided in the embodiment of this application;

[0034] Figure 9 is a schematic diagram of the third working state of various switches in the charging and discharging circuit provided in the embodiment of this application;

[0035] Figure 10 is a schematic diagram of the fourth working state of various switches in the charging and discharging circuit provided in the embodiment of this application;

[0036] Figure 11 is a schematic diagram of the fifth working state of various switches in the charging and discharging circuit provided in the embodiment of this application;

[0037] Figures 12 to 14 are schematic diagrams of three other structures of the charging and discharging circuit provided in the embodiments of this application. Detailed Implementation

[0038] The embodiments of this application are described below with reference to the accompanying drawings.

[0039] Figure 1 shows a schematic diagram of a UPS provided by the prior art. The AC power supply 100 can be mains power. When the mains power is normal, the UPS converts the mains voltage to the supply voltage for the load 400 and provides this supply voltage to the load 400. When the mains power fails, the voltage stored in the energy storage device 300 is converted to the supply voltage and provided to the load 400, thereby ensuring power supply reliability. The UPS mainly includes a rectifier circuit 220, a positive bus Bus+, a negative bus Bus-, a DC / AC inverter circuit 230, and a DC / DC charging / discharging circuit 240. A switching circuit 210 can also be provided between the rectifier circuit 220 and the AC power supply 100, which can control the AC power supply 100 to supply power to the rectifier circuit 220. When the mains power supplies power to the load, the rectifier circuit 220 converts the received mains power into DC power and outputs it to the positive bus Bus+ and the negative bus Bus-. When the mains power fails, the energy storage device 300 supplies power to the load. The DC / DC charging and discharging circuit 240 converts the DC power output from the energy storage device 300 and outputs it to the positive bus Bus+ and the negative bus Bus-. The DC / AC inverter circuit 230 converts the DC power on the positive bus Bus+ and the negative bus Bus- into AC power and outputs it to the load 400, thereby improving the efficiency of the UPS. In practice, the positive and negative buses may be unbalanced due to the different power demands of the load 400. A balancing circuit is required in the UPS to regulate the voltage between the positive bus Bus+ and the negative bus Bus-. Furthermore, the DC / DC charging and discharging circuit 240 is always in operation when the energy storage device 300 is powered. The power of the DC / DC charging and discharging circuit 240 needs to meet the rated power of the UPS system, requiring a larger circuit size, resulting in disadvantages in cost and space.

[0040] In another example, switching circuit 210 can also control energy storage device 300 to supply power to rectifier circuit 220. Switching circuit 210 connects rectifier circuit 220 and energy storage device 300. Rectifier circuit 220 converts the DC power output from energy storage device 300 into AC power and outputs it to inverter circuit 230. Inverter circuit 230 converts the DC power output from rectifier circuit 220 into AC power and outputs it to load 400.

[0041] Figure 2 shows a schematic diagram of a UPS 200 provided in an embodiment of this application. This embodiment combines the charging / discharging circuit 260 and the balancing circuit into one, reducing the design of circuit components and improving circuit utilization. The UPS 200 includes a rectifier circuit 220, an inverter circuit 230, a charging / discharging circuit 260, a positive bus (Bus+), and a negative bus (Bus-). A switching circuit 210 is provided between the rectifier circuit 220 and the AC power supply 100. The A-phase input, B-phase input, and C-phase input terminals of the rectifier circuit 220 are respectively connected to the three-phase output terminals of the AC power supply 100, which can be mains power. The output terminal of the rectifier circuit 220 is connected to the input terminal of the inverter circuit 230 through the positive bus (Bus+) and the negative bus (Bus-). The UPS 200 also includes bus capacitors C1 and C2. The input terminal of the charging / discharging circuit 260 is connected to the energy storage device 300, and the output terminal of the charging / discharging circuit 260 is connected to the positive bus (Bus+) and the negative bus (Bus-). When AC power supply 100 supplies power to load 400, rectifier circuit 220 receives the first AC power output from AC power supply 100 and converts it into first DC power, which is then output to inverter circuit 230. Inverter circuit 230 converts the first DC power into second AC power and outputs it to load 400. When AC power supply 100 fails to supply power to load 400, energy storage device 300 supplies power to load 400. Charging and discharging circuit 260 receives the second DC power output from energy storage device 300 and converts it into third DC power, which is then output to inverter circuit 230. Inverter circuit 230 converts the third DC power into third AC power and outputs it to load 400. During the operation of UPS200, there may be a voltage imbalance between the positive bus Bus+ and the negative bus Bus-. When the absolute value of the voltage difference between the positive bus Bus+ and the negative bus Bus- is greater than or equal to the first threshold, the charging and discharging circuit 260 can adjust the voltage difference between the positive bus Bus+ and the negative bus Bus- to be less than the first threshold by controlling the switching state in the charging and discharging circuit 260, so that the positive and negative bus voltages are balanced.

[0042] For example, AC power supply 100 can also charge energy storage device 300. When energy storage device 300 receives electrical energy from AC power supply 100, rectifier circuit 220 converts the AC power output from AC power supply 100 into first DC power and outputs it to positive bus Bus+ and negative bus Bus-. Charging and discharging circuit 260 receives the first DC power output from rectifier circuit 220 through positive bus Bus+ and negative bus Bus- and converts the first DC power into fourth DC power and outputs it to energy storage device 300 to achieve charging of energy storage device 300.

[0043] Specifically, referring to the circuit topology diagram of the charging / discharging circuit 260 shown in Figure 3, the charging / discharging circuit 260 includes a positive bus capacitor C3 and a negative bus capacitor C4, a first inductor L1, a second inductor L2, a first diode D1, a second diode D2, a first switching switch R1, a second switching switch R2, a first switching transistor Q1, a second switching transistor Q2, and a third switching transistor Q3. The circuit formed by the series connection of the positive bus capacitor C3 and the negative bus capacitor C4 is connected in parallel with the circuit formed by the series connection of the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3. The input terminals of the charging / discharging circuit 260 include a positive input terminal Bat+ and a negative input terminal Bat-. The positive input terminal Bat+ is connected to the connection point of the first switching transistor Q1 and the second switching transistor Q2 through the first switching switch R1 and the first inductor L1. The negative input terminal Bat- is connected to the connection point of the second switching transistor Q2 and the third switching transistor Q3 through the second switching switch R2 and the second inductor L2. The first diode D1 and the second diode D2 are connected in series. The negative terminal of the first diode D1 is connected to the connection point of the first switching switch R1 and the first inductor L1, and the positive terminal of the second diode D2 is connected to the connection point of the second switching switch R2 and the second inductor L2.

[0044] When the charging / discharging circuit 260 is used for charging and discharging the energy storage device 300, that is, when the energy storage device 300 supplies power to the load 400 or when the energy storage device 300 receives AC power 100, the first switching switch R1 and the second switching switch R2 are turned on. During charging, the first switch Q1 and the third switch Q3 operate synchronously, while the second switch Q2 does not operate. During discharging, the first switch Q1 and the third switch Q3 do not operate, while the second switch Q2 operates. In this embodiment, the first switch Q1, the second switch Q2, and the third switch Q3 are examples of switches including body diodes, such as MOSFETs.

[0045] It should be noted that, in the embodiments of this application, "synchronous operation of the switching transistors" refers to "synchronous turn-on or synchronous turn-off of the switching transistors." "No operation of the switching transistors" as used herein refers to "no adjustment of the duty cycle of the switching transistors." The embodiments of this application adjust the operation of the switching transistors by adjusting the duty cycle of the switching transistors [on time / (on time + turn-off time)].

[0046] Specifically, when the mains power is normal, the energy storage device 300 receives electrical energy from the AC power supply 100 through the rectifier circuit 220 and the charging / discharging circuit 260. The charging / discharging circuit 260 operates in a charging state and includes two working stages:

[0047] (1) First stage: The first switch Q1 and the third switch Q3 are turned on synchronously, the second switch Q2 is stably turned off, and the positive and negative buses charge the first inductor L1 and the second inductor L2. The circuit operation state is shown in Figure 3a, where the arrows indicate the direction of current flow.

[0048] (2) Second stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, the body diode in the second switch Q2 is turned on, and the electrical energy stored in the first inductor L1 and the second inductor L2 charges the energy storage device 300. The current direction can be seen in Figure 3b.

[0049] Figure 4 is a schematic diagram showing the operating states of the first switch Q1, the second switch Q2, and the third switch Q3 during the switching process of the charging / discharging circuit 260 shown in Figure 3. The operation of each switch can be controlled by adjusting the duty cycle of each switch. The states of each switch during the charging process can be seen in Figure 4 during the time periods t0 to t1 or t7 to t8, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, and the third switch Q3.

[0050] When the mains power is abnormal, the energy storage device 300 supplies power to the load 400, and the charging / discharging circuit 260 operates in the discharging state. The first switching switch R1 and the second switching switch R2 are stably turned on. The charging / discharging circuit 260 includes two operating stages:

[0051] (1) First stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, and the second switch Q2 is turned on. The circuit operation at this time is shown in Figure 3c, where the arrows indicate the direction of current flow. At this time, the energy storage device 300 stores energy in the first inductor L1 and the second inductor L2.

[0052] (2) Second stage: The first switch Q1 and the third switch Q3 are turned on synchronously, and the second switch Q2 is turned off. At this time, the first inductor L1 and the second inductor L2 discharge to the positive bus Bus+ voltage and the negative bus Bus- voltage. The current direction can be seen in Figure 3d.

[0053] During the discharge process, the status of each switch can be seen in Figure 4 during the time periods t1 to t2 or t9 to t10, specifically the working status of the first switching switch R1, the second switching switch R2, the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3.

[0054] When an imbalance occurs in the voltage of the positive and negative busbars, the charging and discharging circuit 260 operates in a balanced state to balance the voltages of the positive busbar Bus+ and the negative busbar Bus-. At this time, the energy storage device 300 stops charging and discharging, and the first switching switch R1 and the second switching switch R2 are stably disconnected. Since the negative busbar Bus- voltage collected in practice may be negative, this embodiment uses the difference between the absolute values ​​of the positive busbar Bus+ voltage and the negative busbar Bus- voltage as the criterion. The difference between the absolute values ​​of the positive and negative busbar voltages can have the following three cases:

[0055] Case 1: When the absolute value of the voltage on the positive bus Bus+ is greater than or equal to the absolute value of the voltage on the negative bus Bus-, the voltage on the positive bus Bus+ is too high. The charging / discharging circuit 260 operates in equilibrium, with the first switch Q1 and the second switch Q2 operating synchronously, and the third switch Q3 not operating. This includes two operating phases:

[0056] (1) First stage: The first switch Q1 and the second switch Q2 are turned on simultaneously, and the third switch Q3 is turned off. The electrical energy in the positive bus Bus+ is released to the second inductor L2. The circuit operation state at this time is shown in Figure 3e. The arrow in Figure 3e indicates the direction of current.

[0057] (2) Second stage: The first switch Q1 and the second switch Q2 are turned off, the body diode of the third switch Q3 is turned on, and the electrical energy stored in the second inductor L2 is released to the negative bus capacitor C4. The circuit operation at this time is shown in Figure 3f, where the arrows indicate the direction of current.

[0058] After the above two working stages, the electrical energy of the positive bus Bus+ can be released, thereby reducing the voltage difference between the positive bus Bus+ and the negative bus Bus-. The working states of each switch can be seen in Figure 4 during the time period t3 to t4, specifically the working states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, and the third switch Q3.

[0059] Scenario 2: When the absolute value of the voltage on the negative bus Bus- is greater than or equal to the absolute value of the voltage on the positive bus Bus+, the voltage on the negative bus Bus- is too high. In this case, the charging / discharging circuit 260 operates in a balanced state, with the second switch Q2 and the third switch Q3 operating synchronously, while the first switch Q1 remains stationary. This includes two operating phases:

[0060] (1) First stage: The second switch Q2 and the third switch Q3 are turned on simultaneously, and the first switch Q1 is turned off. The electrical energy in the negative bus Bus- is stored in the first inductor L1, thereby reducing the voltage difference between the positive bus Bus+ and the negative bus Bus-. The circuit operation at this time is shown in Figure 3g, where the arrows indicate the current direction.

[0061] (2) Second stage: The body diode of the first switch Q1 is turned on, while the second switch Q2 and the third switch Q3 are turned off. The electrical energy stored in the first inductor L1 is released to the positive bus capacitor C3. The circuit's operating state at this time is shown in Figure 3h, where the arrows indicate the current direction.

[0062] After the above two working stages, the electrical energy of the negative bus Bus- can be released, thereby reducing the voltage difference between the positive bus Bus+ and the negative bus Bus-. The working states of each switch can be seen in Figure 4 during the time period t5 to t6, specifically the working states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, and the third switch Q3.

[0063] Scenario 3: When the absolute value of the voltage on the negative bus Bus- is less than the absolute value of the voltage on the positive bus Bus+, the first switch Q1, the second switch Q2, and the third switch Q3 are all off (open), or the first switch Q1 and the third switch Q3 are both off (open), and the second switch Q2 is on. In this case, the charging / discharging circuit 260 does not operate. The operating states of each switch can be seen in Figure 4 during the time period t4 to t5, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, and the third switch Q3.

[0064] It should be noted that the first threshold, the second threshold, and the third threshold mentioned above can be designed and selected by those skilled in the art according to actual needs.

[0065] It should be understood that the first switching switch R1 and the second switching switch R2 are relays, MOSFETs, IGBTs, or other switching devices including body diodes. MOSFETs can achieve faster switching and avoid the arcing that occurs when relays are switched. See Figures 5 and 6 for details.

[0066] Taking Figure 6 as an example, a third diode D3 is connected in parallel across the two ends of the first switch R1. The positive terminal of the third diode D3 is connected to the connection point between the first switch R1 and the first inductor L1. A fourth diode D4 is connected in parallel across the two ends of the second switch R2. The negative terminal of the fourth diode D4 is connected to the connection point between the second switch R2 and the second inductor L2.

[0067] When the charging and discharging circuit 260 is in the charging state, the first switching switch R1 and the second switching switch R2 are in a stable open state. The energy storage device 300 can be charged through the third diode D3 and the fourth diode D4. Since the diode has the property of unidirectional conduction, if the battery fails and the voltage of the energy storage device 300 is higher than the bus voltage, the diode can prevent the current from flowing back into the bus and improve the safety of the circuit.

[0068] When the mains power is normal, the energy storage device 300 receives electrical energy from the AC power supply 100 through the rectifier circuit 220 and the charging / discharging circuit 260. The charging / discharging circuit 260 operates in a charging state, with the first switch R1 and the second switch R2 open. The first switch Q1 and the third switch Q3 operate synchronously, while the second switch Q2 remains inactive. The charging / discharging circuit 260 includes two operating stages:

[0069] (1) First stage: The first switch Q1 and the third switch Q3 are turned on synchronously, and the second switch Q2 is stably turned off. The positive and negative buses charge the first inductor L1 and the second inductor L2. The circuit operation at this time is shown in Figure 6a, where the arrows indicate the direction of current flow.

[0070] (2) Second stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, and the body diode of the second switch Q2 is turned on. At this time, the electrical energy stored in the first inductor L1 and the second inductor L2 charges the energy storage device 300. The circuit working state and current direction can be seen in Figure 6b.

[0071] When the mains power is abnormal, the energy storage device 300 supplies power to the load 400. The charging and discharging circuit 260 operates in the discharging state, the first switching switch R1 and the second switching switch R2 are stably turned on, the first switch Q1 and the third switch Q3 are not activated, and the second switch Q2 is activated. The charging and discharging circuit 260 includes two operating stages:

[0072] (1) First stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, and the second switch Q2 is turned on. At this time, the energy storage device 300 discharges to the first inductor L1 and the second inductor L2. The circuit operation state at this time is shown in Figure 6c, and the arrows in Figure 6c indicate the direction of current flow.

[0073] (2) Second stage: When the body diodes of the first switch Q1 and the third switch Q3 are turned on and the second switch Q2 is turned off, the first inductor L1 and the second inductor L2 discharge to the positive bus Bus+ voltage and the negative bus Bus- voltage. The current direction can be seen in Figure 6d.

[0074] The first and second diodes in the above embodiments can also be replaced with switching transistors including body diodes, as shown in Figure 7. Figure 7 is another circuit topology provided in an embodiment of this application. The charging and discharging circuit 260 includes a positive bus capacitor C3 and a negative bus capacitor C4, a first inductor L1, a second inductor L2, a first switching switch R1, a second switching switch R2, a first switching transistor Q1, a second switching transistor Q2, a third switching transistor Q3, a fourth switching transistor Q4, and a fifth switching transistor Q5. The circuit formed by the series connection of the positive bus capacitor C3 and the negative bus capacitor C4 is connected in parallel with the circuit formed by the series connection of the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3. The charging / discharging circuit 260 has two input terminals: a positive input terminal Bat+ and a negative input terminal Bat-. The positive input terminal Bat+ is connected to the connection point of the first switch Q1 and the second switch Q2 through the first switch R1 and the first inductor L1. The negative input terminal Bat- is connected to the connection point of the second switch Q2 and the third switch Q3 through the second switch R2 and the second inductor L2. The fourth switch Q4 and the fifth switch Q5 are connected in series between the connection point of the first switch R1 and the first inductor L1 and the connection point of the second switch R2 and the second inductor L2.

[0075] In this embodiment, the first switch Q1, second switch Q2, third switch Q3, fourth switch Q4, and fifth switch Q5 can be switching devices containing body diodes, such as MOSFETs. Even without generating waveforms, the first switch Q1, second switch Q2, third switch Q3, fourth switch Q4, and fifth switch Q5 can automatically achieve unidirectional conduction through their own body diodes. It should be noted that the first switching switch R1 and second switching switch R2 in this embodiment can also be switching devices containing body diodes, or switching devices consisting of a relay and a diode connected in parallel, or their equivalent switching devices.

[0076] When the mains power is normal, the energy storage device 300 receives electrical energy from the AC power supply 100 through the rectifier circuit 220. The charging and discharging circuit 260 operates in the charging state, with the first switch R1 and the second switch R2 turned on. The first switch Q1 and the third switch Q3 operate synchronously, while the second switch Q2 remains off. The charging and discharging circuit 260 includes two operating stages:

[0077] (1) First stage: The first switch Q1 and the third switch Q3 are turned on synchronously, and the second switch Q2 is stably turned off. The positive and negative buses charge the first inductor L1 and the second inductor L2. The circuit operation at this time is shown in Figure 7a, where the arrows indicate the direction of current flow.

[0078] (2) Second stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, and the body diode of the second switch Q2 is turned on. At this time, the electrical energy stored in the first inductor L1 and the second inductor L2 charges the energy storage device 300. The circuit working state and current direction can be seen in Figure 7b.

[0079] The states of each switch can be seen in Figures 8 to 11, during the time periods t0 to t1 or t7 to t8, representing the working states of the first switching switch R1, the second switching switch R2, the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3.

[0080] When the mains power is abnormal, the energy storage device 300 supplies power to the load 400, and the charging / discharging circuit 260 operates in the discharging state. The first switch Q1 and the third switch Q3 are not activated, while the second switch Q2 is activated. The charging / discharging circuit 260 includes two operating stages:

[0081] (1) First stage: The first switch Q1 and the third switch Q3 are simultaneously turned off, and the second switch Q2 is turned on. At this time, the energy storage device 300 discharges to the first inductor L1 and the second inductor L2. The circuit operation state at this time is shown in Figure 7c, and the arrows in Figure 7c indicate the direction of current flow.

[0082] (2) Second stage: When the body diodes of the first switch Q1 and the third switch Q3 are turned on and the second switch Q2 is turned off, the first inductor L1 and the second inductor L2 discharge to the positive bus Bus+ voltage and the negative bus Bus- voltage. The current direction can be seen in Figure 7d.

[0083] The states of each switch can be seen in Figures 8 to 11, during the time periods t1 to t2 and t9 to t10, representing the working states of the first switching switch R1, the second switching switch R2, the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3.

[0084] When an imbalance occurs in the voltage of the positive and negative busbars, the charging and discharging circuit 260 operates in a balanced state to balance the voltages of the positive busbar Bus+ and the negative busbar Bus-. At this time, the energy storage device 300 stops charging and discharging, and the first switching switch R1 and the second switching switch R2 are disconnected. Since the negative busbar Bus- voltage may be negative in practice, this embodiment uses the difference between the absolute values ​​of the positive busbar Bus+ voltage and the negative busbar Bus- voltage as the criterion. The difference between the absolute values ​​of the positive and negative busbar voltages can have the following three cases:

[0085] Scenario 1: When the absolute value of the voltage on the positive bus Bus+ is greater than or equal to the absolute value of the voltage on the negative bus Bus-, the voltage on the positive bus Bus+ is too high, and the charging / discharging circuit 260 operates in equilibrium. In this case, the switching transistor can be controlled in several ways:

[0086] Control mode (1): The first switch Q1, the second switch Q2 and the fifth switch Q5 operate synchronously, while the third switch Q3 and the fourth switch Q4 do not operate.

[0087] Phase 1: Controlling the first switch Q1, the second switch Q2, and the fifth switch Q5 to conduct synchronously, while the third switch Q3 and the fourth switch Q4 are de-energized. The circuit's operating state at this time is shown in Figure 7e. In Figure 7e, the arrows indicate the current direction, and the electrical energy in the positive bus Bus+ is stored in the second inductor L2.

[0088] Second stage: The first switch Q1 and the second switch Q2 are simultaneously turned off, while the body diodes of the third switch Q3 and the fifth switch Q5 are turned on. The electrical energy stored in the second inductor L2 is released to the negative bus capacitor C4. The circuit's operating state at this time is shown in Figure 7f, where the arrows indicate the current direction.

[0089] The two operating phases described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 8 during the time period t3 to t4, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0090] Control mode (2): The first switch Q1 and the second switch Q2 are controlled to operate synchronously, the fifth switch Q5 is turned on, and the third switch Q3 and the fourth switch Q4 are not operated.

[0091] Phase 1: The first switch Q1 and the second switch Q2 are turned on synchronously, the fifth switch Q5 is always on, and the third switch Q3 and the fourth switch Q4 are turned off. The circuit's operating state at this time is shown in Figure 7e. In Figure 7e, the arrows indicate the current direction, and the electrical energy in the positive bus Bus+ is stored in the second inductor L2.

[0092] Second stage: The first switch Q1 and the second switch Q2 are simultaneously turned off, the body diode of the third switch Q3 is turned on, the fifth switch Q5 is normally on, and the fourth switch Q4 is turned off. The electrical energy stored in the second inductor L2 is released to the negative bus capacitor C4. The circuit operation at this time is shown in Figure 7f, where the arrows indicate the current direction.

[0093] The two operating phases described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 9 during the time period t3 to t4, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0094] Control mode (3): The first switch Q1 and the second switch Q2 operate synchronously, while the third switch Q3, the fourth switch Q4 and the fifth switch Q5 do not operate.

[0095] Phase 1: The first switch Q1 and the second switch Q2 are simultaneously turned on, the body diode of the fifth switch Q5 is turned on, and the third switch Q3 and the fourth switch Q4 are turned off. The circuit's operating state at this time is shown in Figure 7e. In Figure 7e, the arrows indicate the current direction, and the electrical energy in the positive bus Bus+ is stored in the second inductor L2.

[0096] Second stage: The body diodes of the third switch Q3 and the fifth switch Q5 are turned on, while the first switch Q1, the second switch Q2, and the fourth switch Q4 are turned off. The electrical energy stored in the second inductor L2 is released to the negative bus capacitor C4. The circuit's operating state at this time is shown in Figure 7f, where the arrows indicate the current direction.

[0097] The two operating phases described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 10 during the time period t3 to t4 for the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0098] Scenario 2: When the absolute value of the voltage on the negative bus Bus- is greater than or equal to the absolute value of the voltage on the positive bus Bus+, the voltage on the negative bus Bus- is too high, and the charging / discharging circuit 260 operates in a balanced state. In this case, the switching transistor has several control methods:

[0099] Control mode (1): The second switch Q2, the third switch Q3 and the fourth switch Q4 are controlled to operate synchronously, while the first switch Q1 and the fifth switch Q5 do not operate.

[0100] Phase 1: The second switch Q2, the third switch Q3, and the fourth switch Q4 are simultaneously turned on, while the first switch Q1 and the fifth switch Q5 are turned off. The circuit's operating state at this time is shown in Figure 7g. The arrows in the figure indicate the direction of current, and the electrical energy in the negative bus Bus- is stored in the first inductor L1.

[0101] Second stage: Control the second switch Q2 and the third switch Q3 to turn off synchronously. At this time, the body diodes of the first switch Q1 and the fourth switch Q4 are turned on. The electrical energy stored in the first inductor L1 is released to the positive bus capacitor C3. The circuit operation at this time is shown in Figure 7h, where the arrows indicate the current direction.

[0102] The two operating stages described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 8 during the time period t5 to t6 for the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0103] Control mode (2): The second switch Q2 and the third switch Q3 are controlled to operate synchronously, the fourth switch Q4 is turned on, and the first switch Q1 and the fifth switch Q5 are not operated.

[0104] Phase 1: The second switch Q2 and the third switch Q3 are simultaneously turned on, the fourth switch Q4 is always on, and the first switch Q1 and the fifth switch Q5 are turned off. The circuit's operating state at this time is shown in Figure 7g. The arrows in the figure indicate the direction of current, and the electrical energy in the negative bus Bus- is stored in the first inductor L1.

[0105] Second stage: The second switch Q2 and the third switch Q3 are simultaneously turned off. At this time, the body diode of the first switch Q1 is turned on, and the fourth switch Q4 is normally turned on. The electrical energy stored in the first inductor L1 is released to the positive bus capacitor C3. The circuit operation at this time is shown in Figure 7h, where the arrows indicate the current direction.

[0106] The two operating stages described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 9 during the time period t5 to t6, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0107] Control method (3): Control the second switch Q2 and the third switch Q3 to operate synchronously, and disconnect the first switch Q1, the fourth switch Q4 and the fifth switch Q5.

[0108] Phase 1: The second switch Q2 and the third switch Q3 are simultaneously turned on, the body diode of the fourth switch Q4 is turned on, and the first switch Q1 and the fifth switch Q5 are turned off. The circuit's operating state at this time is shown in Figure 7g. The arrows in the figure indicate the direction of current, and the electrical energy in the negative bus Bus- is stored in the first inductor L1.

[0109] Second stage: The body diodes of the first switch Q1 and the fourth switch Q4 are turned on, while the second switch Q2, the third switch Q3, and the fifth switch Q5 are turned off. The electrical energy stored in the first inductor L1 is released to the positive bus capacitor C3. The circuit's operating state at this time is shown in Figure 7h, where the arrows indicate the current direction.

[0110] The two operating stages described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. The operating states of each switch can be seen in Figure 10 during the time period t5 to t6 for the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0111] Scenario 3: When the absolute value of the voltage on the negative bus Bus- is less than the absolute value of the voltage on the positive bus Bus+, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5 are all off (disconnected). In this case, the charging / discharging circuit 260 is not operational. The operating states of each switch can be seen in Figures 8-11 during the time interval t3-t4, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, and the third switch Q3. Alternatively, when the absolute value of the voltage on the negative bus Bus- is less than the absolute value of the voltage on the positive bus Bus+, the first switch Q1 and the third switch Q3 are off, while the second switch Q2, the fourth switch Q4, and the fifth switch Q5 can also be normally on. In this case, the charging / discharging circuit 260 is not operational.

[0112] Based on the circuit topology shown in Figure 7, there is another example of controlling the switching transistor to turn on or off when the charging and discharging circuit 260 is in equilibrium.

[0113] Case 1: When the absolute value of the voltage on the positive bus (Bus+) is greater than or equal to the absolute value of the voltage on the negative bus (Bus-), the voltage on the positive bus (Bus+) is too high. The first switch Q1 operates, the second switch Q2, the fourth switch Q4, and the fifth switch Q5 are turned on, and the third switch Q3 does not operate. The charging / discharging circuit 260 operates in equilibrium, including two operating stages:

[0114] (1) First stage: The first switch Q1 is turned on, the second switch Q2, the fourth switch Q4 and the fifth switch Q5 are normally on, and the third switch Q3 is turned off. The circuit operation state at this time is shown in Figure 7i. The arrows in the figure indicate the current direction. The electrical energy in the positive bus Bus+ is stored in the first inductor L1 and the second inductor L2 respectively.

[0115] (2) Second stage: The first switch Q1 is off, the body diode of the third switch Q3 is on, and the second switch Q2, the fourth switch Q4 and the fifth switch Q5 are on. The electrical energy stored in the first inductor L1 and the second inductor L2 is released to the negative bus capacitor C4. The circuit operation state at this time is shown in Figure 7j. The arrow in Figure 7j indicates the direction of current.

[0116] The two operating phases described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. In this case, the operating states of each switch can be seen in Figure 11 during the time period t3 to t4 for the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0117] Case 2: When the absolute value of the voltage on the negative bus Bus- is greater than or equal to the absolute value of the voltage on the positive bus Bus+, the voltage on the negative bus Bus- is too high. The charging / discharging circuit 260 operates in equilibrium. The third switch Q3 is activated, and the second, fourth, and fifth switches Q2, Q4, and Q5 are turned on. The first switch Q1 is not activated. This includes two operating phases:

[0118] (1) First stage: The third switch Q3 is turned on, the second switch Q2, the fourth switch Q4 and the fifth switch Q5 are normally on, and the first switch Q1 is turned off. The circuit working state at this time is shown in Figure 7k. The arrows in the figure indicate the current direction. The electrical energy in the negative bus Bus- is stored in the first inductor L1 and the second inductor L2 respectively.

[0119] (2) Second stage: The second switch Q2, the fourth switch Q4 and the fifth switch Q5 are normally on, the body diode of the first switch Q1 is turned on, the third switch Q3 is turned off, and the electrical energy stored in the first inductor L1 and the second inductor L2 is released to the positive bus capacitor C3. The circuit working state at this time is shown in Figure 7l. The arrow in Figure 7l indicates the current direction.

[0120] The two operating stages described above reduce the voltage difference between the positive bus (Bus+) and the negative bus (Bus-), thus balancing the voltages of the positive and negative buses. In this case, the operating states of each switch can be seen in Figure 11 during the time period t5 to t6 for the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0121] Case 3: When the absolute value of the voltage on the negative bus Bus- is less than the absolute value of the voltage on the positive bus Bus+, all switches Q1, Q2, Q3, Q4, and Q5 are off (disconnected). Alternatively, switches Q2, Q4, and Q5 remain normally on. In this case, the charging / discharging circuit 260 does not operate. The states of each switch can be seen in Figure 11 during the time period t4 to t5, specifically the operating states of the first switching switch R1, the second switching switch R2, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, and the fifth switch Q5.

[0122] Referring again to the schematic diagram of the charging / discharging circuit 260 shown in Figure 14, to further enhance the safety of the charging / discharging circuit 260, fuses 6 and 7 are connected in series between the first diode D1 and the second diode D2. A fuse 3 can be connected in series between the connection point of the first diode D1 and the second diode D2 and the neutral wire. When the current in the charging / discharging circuit 260 is too high, fuses 6 and 7 will melt due to overheating, thereby cutting off the circuit and stopping the charging / discharging circuit 260 from operating, thus improving the circuit's safety.

[0123] Referring to the structural schematic diagram of the charging and discharging circuit 260 shown in FIG13, a fuse 4 is provided between the first switching switch R1 and the positive input terminal Bat+, and a fuse 5 is provided between the second switching switch R2 and the negative input terminal Bat-.

[0124] Referring to the schematic diagram of the charging and discharging circuit 260 shown in Figure 14, a fuse 2 is provided between the first switching switch R1 and the first inductor L1, and a fuse 2 is provided between the second switching switch R2 and the second inductor L2. Fuses 1 and 2 can melt and disconnect the circuit in time when the current is too high, causing the charging and discharging circuit 260 to stop working and ensuring circuit safety.

[0125] It should be noted that the fuses mentioned in this application can be everyday devices such as fuses and circuit breakers.

[0126] Referring to Figures 12-14, a first Hall element CT1 can be installed between the first switching switch R1 and the first inductor L1, and a second Hall element CT2 can be installed between the second switching switch R2 and the second inductor L2. The first Hall element CT1 and the first Hall element CT2 can be ammeters used to detect current. When an abnormal current occurs in the circuit (such as excessive current or reverse current), the charging / discharging circuit 260 is promptly cut off, causing the charging / discharging circuit 260 to stop working and ensuring circuit safety.

[0127] The above-described embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of this application.

Claims

1. An uninterruptible power supply, characterized in that, include: The system includes a rectifier circuit, an inverter circuit, a charging and discharging circuit, a positive bus, and a negative bus. The input terminal of the rectifier circuit is used to connect to an AC power source. The output terminal of the rectifier circuit is connected to the input terminal of the inverter circuit through the positive bus and the negative bus. The input terminal of the charging and discharging circuit is used to connect to an energy storage device. The output terminal of the charging and discharging circuit is connected to the positive bus and the negative bus. When the AC power supply supplies power to the load, the rectifier circuit is used to receive the first AC power output by the AC power supply and convert the first AC power into a first DC power output to the inverter circuit. The inverter circuit is used to convert the first DC power into a second AC power output to the load. When the energy storage device supplies power to the load, the charging and discharging circuit is used to receive the second DC power output by the energy storage device and convert the second DC power into a third DC power output to the inverter circuit. The inverter circuit is used to convert the third DC power into a third AC power output to the load. When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to a first threshold, the charging and discharging circuit is used to control the switching action in the charging and discharging circuit to adjust the voltage difference between the positive bus and the negative bus to be less than the first threshold.

2. The uninterruptible power supply according to claim 1, characterized in that, When the energy storage device receives electrical energy from the AC power source, the charging and discharging circuit is used to receive the first DC power output from the rectifier circuit through the positive bus and the negative bus, and convert the first DC power into a fourth DC power output to the energy storage device.

3. The uninterruptible power supply according to claim 1 or 2, characterized in that, The charging and discharging circuit includes a positive bus capacitor and a negative bus capacitor, a first inductor, a second inductor, a first diode, a second diode, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, and a third switching transistor; The circuit formed by the series connection of the positive bus capacitor and the negative bus capacitor is connected in parallel with the circuit formed by the series connection of the first switch, the second switch and the third switch. The input terminals of the charging and discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through a first switching switch and a first inductor. The negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through a second switching switch and a second inductor. The first diode and the second diode are connected in series. The cathode of the first diode is connected to the connection point of the first switch and the first inductor, and the anode of the second diode is connected to the connection point of the second switch and the second inductor.

4. The uninterruptible power supply according to claim 3, characterized in that, When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to the first threshold, the first switching switch and the second switching switch are disconnected. When the difference between the absolute value of the voltage on the positive bus and the absolute value of the voltage on the negative bus is greater than or equal to a second threshold, the first and second switches operate synchronously, while the third switch does not operate; and / or, When the difference between the absolute value of the voltage of the negative bus and the absolute value of the voltage of the positive bus is greater than or equal to the third threshold, the second switch and the third switch operate synchronously, while the first switch does not operate.

5. The uninterruptible power supply according to claim 1 or 2, characterized in that, The charging and discharging circuit includes a first capacitor, a second capacitor, a first inductor, a second inductor, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a fifth switching transistor; The circuit formed by the series connection of the first capacitor and the second capacitor is connected in parallel with the circuit formed by the series connection of the first switch, the second switch and the third switch. The input terminals of the charging and discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through a first switching switch and a first inductor. The negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through a second switching switch and a second inductor. The fourth and fifth switching transistors are connected in series between the connection point of the first switching switch and the first inductor and the connection point of the second switching switch and the second inductor.

6. The uninterruptible power supply according to any one of claims 1-5, characterized in that, When the energy storage device receives electrical energy from the AC power source, the first and second switching switches are turned on, the first and third switching transistors operate synchronously, and the second switching transistor does not operate; and / or, When the energy storage device supplies power to the load, the first switching switch and the second switching switch are turned on, the first switching transistor and the third switching transistor are not activated, and the second switching transistor is activated.

7. The uninterruptible power supply according to any one of claims 1-5, characterized in that, A third diode is connected in parallel across the two ends of the first switch, and the anode of the third diode is connected to the connection point between the first switch and the first inductor. A fourth diode is connected in parallel across the two ends of the second switch, and the cathode of the fourth diode is connected to the connection point between the second switch and the second inductor.

8. The uninterruptible power supply according to any one of claims 1-5, characterized in that, The first switching switch and the second switching switch are switching devices that include a body diode.

9. The uninterruptible power supply according to claim 7 or 8, characterized in that, When the energy storage device receives electrical energy from the AC power source, the first switching switch and the second switching switch are disconnected, the first switching transistor and the third switching transistor operate synchronously, and the second switching transistor does not operate. And / or, when the energy storage device supplies power to the load, the first switching switch and the second switching switch are turned on, the second switching transistor is activated, and the first switching transistor and the third switching transistor are not activated.

10. The uninterruptible power supply according to claim 5 or 6, characterized in that, When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to the first threshold, the first switching switch and the second switching switch are disconnected. When the difference between the absolute value of the voltage of the positive bus and the absolute value of the voltage of the negative bus is greater than or equal to a second threshold, the first switch, the second switch, and the fifth switch operate synchronously, while the third switch and the fourth switch do not operate; and / or, When the difference between the absolute value of the voltage of the negative bus and the absolute value of the voltage of the positive bus is greater than or equal to the third threshold, the second, third, and fourth switches operate synchronously, while the first and fifth switches do not operate.

11. The uninterruptible power supply according to claim 5 or 6, characterized in that, When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to the first threshold, the first switching switch and the second switching switch are disconnected. When the difference between the absolute value of the voltage of the positive bus and the absolute value of the voltage of the negative bus is greater than or equal to the second threshold, the first and second switches operate synchronously, the fifth switch is turned on, and the third and fourth switches are not operated; and / or, When the difference between the absolute value of the voltage of the negative bus and the absolute value of the voltage of the positive bus is greater than or equal to the second threshold, the second switch and the third switch operate synchronously, the fourth switch is turned on, and the first switch and the fifth switch do not operate.

12. The uninterruptible power supply according to claim 5 or 6, characterized in that, When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to the first threshold, the first switching switch and the second switching switch are disconnected. When the difference between the absolute value of the voltage of the positive bus and the absolute value of the voltage of the negative bus is greater than or equal to a second threshold, the first and second switches operate synchronously, while the third, fourth, and fifth switches do not operate; and / or, When the difference between the absolute value of the voltage of the negative bus and the absolute value of the voltage of the positive bus is greater than or equal to the second threshold, the second switch and the third switch operate synchronously, while the first switch, the fourth switch and the fifth switch do not operate.

13. The uninterruptible power supply according to claim 5 or 6, characterized in that, When the absolute value of the voltage difference between the positive bus and the negative bus is greater than or equal to the first threshold, the first switching switch and the second switching switch are disconnected. When the difference between the absolute value of the voltage on the positive bus and the absolute value of the voltage on the negative bus is greater than or equal to a second threshold, the first switch operates, the second, fourth, and fifth switches are turned on, and the third switch does not operate; and / or When the difference between the absolute value of the voltage of the negative bus and the absolute value of the voltage of the positive bus is greater than or equal to the second threshold, the third switch is activated, the second switch, the fourth switch and the fifth switch are turned on, and the first switch is not activated.

14. The uninterruptible power supply according to any one of claims 1-4, characterized in that, A first fuse and a second fuse are connected in series between the first diode and the second diode.

15. The uninterruptible power supply according to any one of claims 1-14, characterized in that, A third fuse is provided between the first switching switch and the positive input terminal, and a fourth fuse is provided between the second switching switch and the negative input terminal; or, a third fuse is provided between the first switching switch and the first inductor, and a fourth fuse is provided between the second switching switch and the second inductor.

16. A charging and discharging circuit, characterized in that, The input terminal of the charging and discharging circuit is used to connect to the energy storage device, and the output terminal of the charging and discharging circuit is used to connect to the positive bus and the negative bus. The charging and discharging circuit includes a positive bus capacitor and a negative bus capacitor, a first inductor, a second inductor, a first diode, a second diode, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, and a third switching transistor. The circuit formed by the series connection of the positive bus capacitor and the negative bus capacitor is connected in parallel with the circuit formed by the series connection of the first switch, the second switch and the third switch. The input terminals of the charging and discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through a first switching switch and a first inductor. The negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through a second switching switch and a second inductor. The first diode and the second diode are connected in series. The cathode of the first diode is connected to the connection point of the first switch and the first inductor, and the anode of the second diode is connected to the connection point of the second switch and the second inductor.

17. A charging and discharging circuit, characterized in that, The input terminal of the charging and discharging circuit is used to connect to the energy storage device, and the output terminal of the charging and discharging circuit is used to connect to the positive bus and the negative bus. The charging and discharging circuit includes a first capacitor, a second capacitor, a first inductor, a second inductor, a first switching switch, a second switching switch, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a fifth switching transistor. The circuit formed by the series connection of the first capacitor and the second capacitor is connected in parallel with the circuit formed by the series connection of the first switch, the second switch and the third switch. The input terminals of the charging and discharging circuit include a positive input terminal and a negative input terminal. The positive input terminal is connected to the connection point of the first switching transistor and the second switching transistor through a first switching switch and a first inductor. The negative input terminal is connected to the connection point of the second switching transistor and the third switching transistor through a second switching switch and a second inductor. The fourth and fifth switching transistors are connected in series between the connection point of the first switching switch and the first inductor and the connection point of the second switching switch and the second inductor.

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