Three-leg topology apparatus, control method, and uninterruptible power supply system

Abstract

The application provides a three-bridge-arm topological device, a control method and an uninterruptible power supply system. The three-bridge-arm topological device reuses a voltage conversion circuit, so that the battery pack can be charged without adding an additional charger. In addition, in the mains power supply mode or the battery power supply mode, the voltage conversion circuit and the three-bridge-arm conversion circuit work, that is, all devices of the three-bridge-arm topological device work. When the three-bridge-arm topological device is applied to a battery low-voltage large-current uninterruptible power supply system, the device reuse rate of the system can be improved, the device design redundancy can be avoided, and the cost of the battery low-voltage large-current uninterruptible power supply system is reduced.

Description

Technical Field

[0001] This invention relates to uninterruptible power supply (UPS) technology, and more particularly to a three-arm topology device, control method, and UPS system. Background Technology

[0002] An online uninterruptible power supply (UPS) system is a type of UPS system where the AC voltage supplied to the load always passes through an inverter circuit, regardless of whether the mains voltage is normal or not. Based on power rating, online UPS systems are divided into online low-to-medium power UPS systems and online high-power UPS systems. Online low-to-medium power UPS systems typically refer to those with a power rating between 1 kW and 3 kW.

[0003] Battery-powered low-voltage high-current UPS systems are a type of online small-to-medium power UPS system. These systems use a small number of battery cells in their battery packs, allowing them to output low-voltage, high-current power when supplying power to a load. Due to the limited number of battery cells, battery-powered low-voltage high-current UPS systems are widely used in the online small-to-medium power UPS market. However, existing battery-powered low-voltage high-current UPS systems have low component reuse rates, resulting in higher costs. Summary of the Invention

[0004] This invention provides a three-bridge-arm topology device, a control method, and an uninterruptible power supply system to solve the technical problem of low device reuse rate in existing low-voltage, high-current battery UPS systems.

[0005] In a first aspect, the present invention provides a three-arm topology device, the three-arm topology device comprising: a battery pack, a voltage conversion circuit, a switching switch, and a three-arm conversion circuit;

[0006] The three-arm converter circuit includes: a first arm, a second arm, a third arm, a first inductor, a second inductor, a DC bus capacitor, and a first capacitor; the first arm includes a first switch and a second switch connected in series; the second arm includes a third switch and a fourth switch connected in series; the third arm includes a fifth switch and a sixth switch connected in series; the first arm, the second arm, the third arm, and the DC bus capacitor are connected in parallel between the positive output terminal and the negative output terminal of the bus; the midpoint of the first arm is connected to the first end of the first inductor, and the second end of the first inductor is connected as the positive voltage input terminal of the three-arm topology; the midpoint of the second arm is connected as the negative voltage input terminal of the three-arm topology; the midpoint of the third arm is connected to the first end of the second inductor, and the second end of the second inductor is the output terminal of the three-arm topology, connected to the load and the first end of the first capacitor respectively, and the second end of the first capacitor is connected to the negative voltage input terminal;

[0007] The battery pack is connected to the first terminal of the voltage conversion circuit. The positive terminal of the second terminal of the voltage conversion circuit is connected to the positive output terminal of the bus and the positive voltage input terminal via the switching switch. The negative terminal of the second terminal of the voltage conversion circuit is connected to the negative output terminal of the bus. The live wire of the AC power supply is connected to the positive voltage input terminal via the switching switch, and the neutral wire of the AC power supply is connected to the negative voltage input terminal. The switching switch is used to control the voltage conversion circuit to charge the battery pack in AC power supply mode and to control the voltage conversion circuit to discharge the battery pack in battery power supply mode.

[0008] In a first possible implementation, the switching switch includes: a first switch, a second switch, and a balancing component; the positive terminal of the second end of the voltage conversion circuit is connected to the fixed terminal of the first switch, the first selector terminal of the first switch is connected to the first terminal of the balancing component, the second terminal of the balancing component is connected to the positive output terminal of the bus, the second selector terminal of the first switch is connected to the positive voltage input terminal, the first terminal of the second switch is connected to the live wire of the AC power supply, the second terminal of the second switch is connected to the positive voltage input terminal, and the negative terminal of the second end of the voltage conversion circuit is connected to the negative output terminal of the bus; the balancing component is used to balance the voltage between the bus and the voltage conversion circuit; in the AC power supply mode, the fixed terminal of the first switch is connected to the first selector terminal of the first switch, and the second switch is closed; in the battery power supply mode, the fixed terminal of the first switch is connected to the second selector terminal of the first switch, and the second switch is open.

[0009] Optionally, the first switch is any one of the following: a double-throw relay, a bidirectional electronic switch, or a thyristor. Optionally, the second switch is any one of the following: a single-throw relay, a unidirectional electronic switch, or a thyristor. Optionally, the balancing component is any one of the following: a varistor, a negative temperature coefficient thermistor, or a third inductor.

[0010] Optionally, the balancing component is a resistor, and the switching switch further includes: a third switch; the positive terminal of the second end of the voltage conversion circuit is connected to the first end of the third switch, and the second end of the third switch is connected to the positive output terminal of the bus; or, the third switch is connected in parallel with the resistor; in the AC power supply mode, and when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the third switch is closed; in the battery power supply mode, the third switch is open. Optionally, the third switch is any of the following: a single-throw relay, a one-way electronic switch, or a thyristor.

[0011] In a second possible implementation, the switching switch includes a first switch, a second switch, and a balancing component. The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the first switch and the first selection terminal of the second switch. The second end of the first switch is connected to the first end of the balancing component. The second end of the balancing component is connected to the positive output terminal of the bus. The second selection terminal of the second switch is connected to the live wire of the AC power supply. The fixed end of the second switch is connected to the positive voltage input terminal. The negative terminal of the second end of the voltage conversion circuit is connected to the negative output terminal of the bus. The balancing component is used to balance the voltage between the bus and the voltage conversion circuit. In the AC power supply mode, the first switch is closed, and the fixed end of the second switch is connected to the second selection terminal of the second switch. In the battery power supply mode, the first switch is open, and the fixed end of the second switch is connected to the first selection terminal of the second switch.

[0012] Optionally, the first switch is any one of the following: a single-throw relay, a unidirectional electronic switch, or a thyristor. Optionally, the second switch is any one of the following: a double-throw relay, a bidirectional electronic switch, or a thyristor. Optionally, the balancing component is any one of the following: a varistor, a negative temperature coefficient thermistor, or a third inductor.

[0013] Optionally, the balancing component is a resistor, and the switching switch further includes: a third switch; the positive terminal of the second end of the voltage conversion circuit is connected to the first end of the third switch, and the second end of the third switch is connected to the positive output terminal of the bus; or, the third switch is connected in parallel with the resistor; in the AC power supply mode, and when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the third switch is closed; in the battery power supply mode, the third switch is open. Optionally, the third switch is any of the following: a single-throw relay, a one-way electronic switch, or a thyristor.

[0014] In a third possible implementation, the switching switch includes a first switch, a second switch, a third switch, and a balancing component. The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the first switch and the first end of the third switch, respectively. The second end of the first switch is connected to the positive voltage input terminal. The first end of the second switch is connected to the live wire of the AC power supply. The second end of the second switch is connected to the positive voltage input terminal. The second end of the third switch is connected to the first end of the balancing component. The second end of the balancing component is connected to the positive output terminal of the bus. The negative terminal of the second end of the voltage conversion circuit is connected to the negative output terminal of the bus. The balancing component is used to balance the voltage between the bus and the voltage conversion circuit. In the AC power supply mode, the first switch is open, and the second and third switches are closed. In the battery power supply mode, the first switch is closed, and the second and third switches are open.

[0015] Optionally, the first switch is any one of the following: a single-throw relay, a one-way electronic switch, or a thyristor. Optionally, the second switch is any one of the following: a single-throw relay, a one-way electronic switch, or a thyristor. Optionally, the third switch is any one of the following: a single-throw relay, a one-way electronic switch, or a thyristor. Optionally, the balancing component is any one of the following: a varistor, a negative temperature coefficient thermistor, or a third inductor.

[0016] Optionally, the balancing component is a resistor, and the switching switch further includes: a fourth switch; the positive terminal of the second end of the voltage conversion circuit is connected to the first end of the fourth switch, and the second end of the fourth switch is connected to the positive output terminal of the bus; or, the fourth switch is connected in parallel with the resistor; in the AC power supply mode, and when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the fourth switch is closed; in the battery power supply mode, the fourth switch is open. Optionally, the fourth switch is any of the following: a single-throw relay, a one-way electronic switch, or a thyristor.

[0017] The fourth possible implementation is that the voltage conversion circuit includes: a fourth bridge arm, a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, a transformer, a third inductor, a second capacitor, and a third capacitor;

[0018] The fourth bridge arm includes a seventh switch and an eighth switch, with the first end of the seventh switch connected to the first end of the eighth switch.

[0019] The fifth bridge arm includes a ninth switch and a tenth switch, with the first end of the ninth switch connected to the first end of the tenth switch.

[0020] The sixth bridge arm includes an eleventh switch and a twelfth switch, with the first end of the eleventh switch connected to the first end of the twelfth switch.

[0021] The seventh bridge arm includes a thirteenth switch and a fourteenth switch, with the first end of the thirteenth switch connected to the first end of the fourteenth switch;

[0022] The fourth bridge arm is connected in parallel with the fifth bridge arm, the sixth bridge arm and the seventh bridge arm are connected in parallel with the third capacitor, the first terminal of the transformer is connected to the midpoint of the fourth bridge arm, the second terminal of the transformer is connected to the midpoint of the fifth bridge arm, the third terminal of the transformer is connected to the midpoint of the fifth bridge arm through the third inductor and the second capacitor, and the fourth terminal of the transformer is connected to the midpoint of the sixth bridge arm.

[0023] The second terminal of the seventh switch is the positive terminal of the first terminal of the voltage conversion circuit, the second terminal of the eighth switch is the negative terminal of the first terminal of the voltage conversion circuit, the second terminal of the thirteenth switch is the positive terminal of the second terminal of the voltage conversion circuit, and the second terminal of the fourteenth switch is the negative terminal of the second terminal of the voltage conversion circuit.

[0024] Secondly, the present invention also provides an uninterruptible power supply system, the system comprising: an AC power supply, a load, and a three-arm topology device as described in any of the first aspects; wherein the live wire of the AC power supply is connected to the positive voltage input terminal of the three-arm topology device, the neutral wire of the AC power supply is connected to the negative voltage input terminal of the three-arm topology device, and the output terminal of the three-arm topology device is connected to the load.

[0025] Thirdly, the present invention also provides a control method for a three-arm topology device, the method being used to control the three-arm topology device provided in the first possible implementation of the first aspect, the method comprising: in a mains power supply mode, controlling the fixed end of a first switch to connect with the first selector end of the first switch, and closing a second switch; in a battery power supply mode, controlling the fixed end of the first switch to connect with the second selector end of the first switch, and opening the second switch.

[0026] Optionally, the method further includes: in mains power supply mode, when the voltage difference between the bus and the voltage conversion circuit of the three-arm topology device is less than or equal to a preset threshold, controlling the third switch to close; in battery power supply mode, controlling the third switch to open.

[0027] Fourthly, the present invention also provides a control method for a three-arm topology device, the method being used to control the three-arm topology device provided in the second possible implementation of the first aspect, the method comprising: in a mains power supply mode, controlling a first switch to close, and the fixed end of a second switch being connected to a second selector end of the second switch; in a battery power supply mode, controlling the first switch to open, and the fixed end of the second switch being connected to a first selector end of the second switch.

[0028] Optionally, the method further includes: in mains power supply mode, when the voltage difference between the bus and the voltage conversion circuit of the three-arm topology device is less than or equal to a preset threshold, controlling the third switch to close; in battery power supply mode, controlling the third switch to open.

[0029] Fifthly, the present invention also provides a control method for a three-arm topology device, the method being used to control the three-arm topology device provided in the third possible implementation of the first aspect, the method comprising: in a mains power supply mode, controlling a first switch to be open and a second switch and a third switch to be closed; and in a battery power supply mode, controlling the first switch to be closed and the second switch and the third switch to be open.

[0030] Optionally, the method further includes: in mains power supply mode, controlling the fourth switch to close when the voltage difference between the bus and the voltage conversion circuit of the three-arm topology device is less than or equal to a preset threshold; and in battery power supply mode, controlling the fourth switch to open.

[0031] The three-arm topology device, control method, and uninterruptible power supply system provided by this invention achieve battery charging or discharging through a multiplexed voltage conversion circuit, eliminating the need for an additional charger. Furthermore, both the voltage conversion circuit and the three-arm switching circuit operate in both mains power and battery power modes, meaning all components of the three-arm topology device are involved. When this three-arm topology device is applied to a low-voltage, high-current battery UPS system, it improves the component reuse rate, avoids component design redundancy, and thus reduces the cost of the low-voltage, high-current battery UPS system. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of a battery-powered low-voltage, high-current UPS system provided for the present technology;

[0034] Figure 2 Schematic diagram of the first three-arm topology device provided by the present invention Figure 1 ;

[0035] Figure 3 Schematic diagram of the first three-arm topology device provided by the present invention Figure 2 ;

[0036] Figure 4 This is a schematic diagram of the second three-arm topology device provided by the present invention;

[0037] Figure 5 This is a schematic diagram of the third three-arm topology device provided by the present invention;

[0038] Figure 6 This is a schematic diagram of the fourth three-arm topology device provided by the present invention;

[0039] Figure 7 This is a schematic diagram of the fifth three-arm topology device provided by the present invention;

[0040] Figure 8 A schematic diagram of the current in the mains power supply mode for the fourth three-arm bridge topology device provided by the present invention;

[0041] Figure 9 A schematic diagram of the current in the mains power supply mode for the fourth three-arm bridge topology device provided by the present invention;

[0042] Figure 10 A schematic diagram of the current in the mains power supply mode for the fourth three-arm bridge topology device provided by the present invention;

[0043] Figure 11 A schematic diagram of the current in the mains power supply mode for the fourth three-arm bridge topology device provided by the present invention;

[0044] Figure 12 A schematic diagram of the current in battery-powered mode for the fourth three-arm bridge topology device provided by the present invention;

[0045] Figure 13 A schematic diagram of the current in battery-powered mode for the fourth three-arm bridge topology device provided by the present invention;

[0046] Figure 14 A schematic diagram of the sixth three-arm topology device provided by the present invention;

[0047] Figure 15 A schematic diagram of the seventh three-arm topology device provided by the present invention;

[0048] Figure 16 A schematic diagram of the eighth three-arm topology device provided by the present invention;

[0049] Figure 17 A schematic diagram of the ninth type of three-arm topology device provided by the present invention;

[0050] Figure 18 A schematic diagram of the tenth three-arm topology device provided by the present invention;

[0051] Figure 19 A schematic diagram of the eleventh three-arm topology device provided by the present invention;

[0052] Figure 20 A schematic diagram of the twelfth three-arm topology device provided by the present invention;

[0053] Figure 21 A schematic diagram of the thirteenth three-arm topology device provided by the present invention;

[0054] Figure 22 A schematic diagram of the fourteenth three-arm topology device provided by the present invention;

[0055] Figure 23 This is a schematic diagram of the fifteenth three-arm topology device provided by the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Figure 1 This is a schematic diagram of a low-voltage, high-current battery-powered UPS system provided by existing technology. Figure 1 As shown, common low-voltage, high-current battery UPS systems currently include: charger, battery pack, unidirectional DC-DC converter, AC power supply, Vienna rectifier converter, and half-bridge inverter.

[0058] In AC power supply mode, the Vienna rectifier converter converts AC power to DC power, the half-bridge inverter converts the DC power back to AC power to supply the load, and the charger charges the battery pack. In AC power supply mode, the Vienna rectifier converter, half-bridge inverter, and charger are all active; in this mode, the DC-DC converter is idle.

[0059] In battery-powered mode (i.e., when powered by a battery pack), the DC-DC converter boosts the DC output from the battery pack, and the half-bridge inverter converts the DC back to AC to supply the load. In other words, both the DC-DC converter and the half-bridge inverter are operational. In battery-powered mode, the Vienna rectifier and charger are idle.

[0060] In other words, some components of existing low-voltage, high-current battery UPS systems are idle during operation, resulting in a low component reuse rate and thus a higher cost.

[0061] In view of the above problems, this application provides a three-arm topology device. When the device is applied to a low-voltage, high-current UPS system, all the components of the device participate in the operation, whether in mains power supply mode or battery power supply mode, which improves the component reuse rate of the low-voltage, high-current UPS system and thus reduces the cost of the low-voltage, high-current UPS system.

[0062] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0063] Figure 2 Schematic diagram of the first three-arm topology device provided by the present invention Figure 1 .like Figure 2 As shown, the three-arm topology device may include: a battery pack, a voltage conversion circuit, a switching switch, and a three-arm conversion circuit.

[0064] The three-arm converter circuit may include: a first arm, a second arm, a third arm, a first inductor L1, a second inductor L2, a DC bus capacitor E1, and a first capacitor Co.

[0065] The first bridge arm includes a first switch Q1 and a second switch Q2, which are connected in series between BUS+ and BUS-, where BUS+ is the positive output terminal of the bus and BUS- is the negative output terminal of the bus. For example, the first end of the first switch Q1 is connected to BUS+, the second end of the first switch Q1 is connected to the first end of the second switch Q2, and the second end of the second switch Q2 is connected to BUS-. The common terminal of the first switch Q1 and the second switch Q2 is called the midpoint of the first bridge arm. In some embodiments, this first bridge arm can also be called the high-frequency bridge arm on the power factor correction (PFC) side.

[0066] The second bridge arm includes a third switch Q3 and a fourth switch Q4, which are connected in series between BUS+ and BUS-. For example, the first end of the third switch Q3 is connected to BUS+, the second end of the third switch Q3 is connected to the first end of the fourth switch Q4, and the second end of the fourth switch Q4 is connected to BUS-. The common end of the third switch Q3 and the fourth switch Q4 is called the midpoint of the second bridge arm. In some embodiments, this second bridge arm can also be referred to as the bridge arm shared by the PFC and the inverter (INV).

[0067] The third bridge arm includes a fifth switch Q5 and a sixth switch Q6, which are connected in series between BUS+ and BUS-. For example, the first end of the fifth switch Q5 is connected to BUS+, the second end of the fifth switch Q5 is connected to the first end of the sixth switch Q6, and the second end of the sixth switch Q6 is connected to BUS-. The common end of the fifth switch Q5 and the sixth switch Q6 is called the midpoint of the third bridge arm. In some embodiments, this third bridge arm can also be called the INV-side high-frequency bridge arm.

[0068] The DC bus capacitor E1 is connected between BUS+ and BUS-. That is, the first bridge arm, the second bridge arm, the third bridge arm, and the DC bus capacitor E1 are connected in parallel between BUS+ and BUS-.

[0069] The first inductor L1 is a high-frequency inductor on the PFC side, and the second inductor L2 is a high-frequency inductor on the INV side. The midpoint of the first bridge arm is connected to the first terminal of the first inductor L1, and the second terminal of the first inductor L1 serves as the positive voltage input terminal AC_L of the three-bridge-arm topology. The midpoint of the second bridge arm serves as the negative voltage input terminal AC_N of the three-bridge-arm topology. The midpoint of the third bridge arm is connected to the first terminal of the second inductor L2, and the second terminal of the second inductor L2 serves as the output terminal of the three-bridge-arm topology, connected to both the load and the first terminal of the first capacitor Co. The second terminal of the first capacitor Co is connected to the negative voltage input terminal AC_N.

[0070] The positive terminal of the battery pack is connected to the positive terminal of the first end of the voltage conversion circuit, and the negative terminal of the battery pack is connected to the negative terminal of the first end of the voltage conversion circuit. The positive terminal of the second end of the voltage conversion circuit is connected to BUS+ and the positive voltage input terminal AC_L via a switch, and the negative terminal of the second end of the voltage conversion circuit is connected to BUS-. The live wire of the AC mains power supply is connected to the positive voltage input terminal AC_L via a switch, and the neutral wire of the AC mains power supply is connected to the negative voltage input terminal AC_N.

[0071] The aforementioned battery pack may include at least one battery, which can be determined based on the power of the UPS system to which the three-arm topology device is applied. For example, the UPS system may be an online UPS system with a power between 1 kW and 3 kW, or the UPS may be a battery low-voltage high-current UPS system.

[0072] In this embodiment, the three-arm topology has two power supply modes: AC power supply mode and battery power supply mode. AC power supply mode refers to a mode where a stable AC power supply is provided; battery power supply mode refers to a mode where the AC power input is low voltage, or there is no AC power input. The three-arm topology can switch between these two modes using a switch.

[0073] In AC power mode, the switch controls the AC power supply to power the three-bridge converter circuit. At this time, the three-bridge converter circuit operates in AC-AC mode. For example, the PFC in the three-bridge converter circuit converts the AC input AC power into DC power (i.e., rectifies the AC input AC power). The DC bus capacitor E1 filters (or regulates) the DC power obtained by the PFC, resulting in stable DC power. The INV of the three-bridge converter circuit then converts the stable DC power back into AC power and outputs it to the load to power it.

[0074] It should be noted that although the PFC converts AC to DC, this DC still contains a certain amount of pulsating AC component, known as ripple voltage. Therefore, in mains power supply mode, the DC bus capacitor E1 can filter (or regulate) the DC obtained from the PFC to remove the ripple voltage and obtain a smooth and stable DC voltage. Simultaneously, the DC bus capacitor E1 can store energy.

[0075] In AC power mode, the switch can control the voltage conversion circuit to charge the battery pack. For example, the switch can control the voltage conversion circuit to charge the battery pack when AC power is on and the battery pack voltage is low. This means that charging the battery pack is achieved by reusing the voltage conversion circuit, eliminating the need for an additional charger. In this AC power mode, both the voltage conversion circuit and the three-arm switching circuit are active, meaning all components of the three-arm topology are involved.

[0076] For example, the switch can control the voltage conversion circuit to be connected between BUS+ and BUS-. The voltage conversion circuit operates in BUCK mode (i.e., buck mode), and steps down the BUS voltage output from the DC bus capacitor E1 (i.e., the voltage obtained after filtering the DC power converted by the PFC by the DC bus capacitor E1) to obtain the charging voltage for the battery pack, which is then used to charge the battery pack. In this case, the battery pack serves as the output source of the voltage conversion circuit.

[0077] Reference Figure 1 In existing technologies, when using a charger to charge a battery pack, the charger needs to include a rectifier circuit and a buck circuit. The rectifier circuit rectifies the AC power supplied by the mains AC power source to obtain DC power. The buck circuit reduces the voltage of this DC power to obtain the charging voltage for the battery pack. Because the AC power supplied by the mains AC power source fluctuates over a wide range, the buck circuit in the charger needs to achieve a wide range of voltage regulation, resulting in low voltage conversion efficiency. Therefore, when using a charger to charge a battery pack, the charging efficiency of the charger is relatively low.

[0078] In this embodiment of the invention, the BUS voltage output by the DC bus capacitor E1 is a stable DC voltage obtained by PFC rectification of the three-arm converter circuit. Therefore, when using the BUS voltage output by the DC bus capacitor E1 to charge the battery pack, the voltage conversion circuit can be reused to step down the BUS voltage output by the DC bus capacitor E1, and there is no need to set up a separate rectification circuit. In other words, by reusing the PFC of the three-arm converter circuit, DC power for charging the battery pack is obtained.

[0079] In addition, since the BUS voltage output by the DC bus capacitor E1 is a stable DC voltage, there is no need to use a voltage conversion circuit with a wide voltage regulation range to step down the BUS voltage output by the DC bus capacitor E1, which improves the conversion efficiency of the voltage conversion circuit and thus improves the charging efficiency of the battery pack.

[0080] In battery-powered mode, the switch can control the voltage conversion circuit to discharge the battery pack. For example, the switch can connect the voltage conversion circuit between the high-frequency inductor (i.e., the first inductor L1) on the PFC side and BUS-. In this case, the voltage conversion circuit is connected in series with the "first inductor L1 and the first arm of the three-arm converter circuit forming a Boost circuit," achieving two-stage voltage boosting during battery discharge. Specifically, the voltage conversion circuit operates in Boost mode (i.e., boost mode), performing a first-stage boost on the battery pack's output voltage. The first inductor L1 and the first arm of the three-arm converter circuit form a Boost circuit, performing a second-stage boost on the battery pack's output voltage. The boosted voltage is then input to the DC bus capacitor E1 of the three-arm converter circuit to maintain bus voltage balance.

[0081] In UPS systems with low-voltage, high-current batteries, the battery pack outputs a lower voltage, while the load requires a higher voltage. Therefore, when this three-arm topology is applied to such a system, it needs to boost a lower voltage to a higher voltage—that is, it requires a significant voltage difference boosting process. If the voltage conversion circuit is connected in parallel with the first inductor L1 and the first arm of the three-arm conversion circuit to form a boost circuit, and only the voltage conversion circuit is used to perform this boosting operation (i.e., using the voltage conversion circuit for a single-stage boosting process), the following problems arise:

[0082] 1. The voltage conversion circuit has a maximum boost ratio (e.g., output voltage divided by input voltage), which may result in the voltage boosted by the voltage conversion circuit using the maximum boost ratio still being less than the voltage required by the load of the UPS system with low battery voltage and high current, thus failing to meet the usage requirements of the UPS system with low battery voltage and high current.

[0083] 2. The higher the boost ratio, the lower the conversion efficiency of the voltage conversion circuit, and the greater the risk of current stress and heat loss in the voltage conversion circuit. Therefore, the above-mentioned use of a voltage conversion circuit for a single-stage boost process requires the voltage conversion circuit to perform a high boost ratio, resulting in lower conversion efficiency and higher risks of current stress and heat loss in the voltage conversion circuit.

[0084] Considering the problems associated with using a voltage conversion circuit for single-stage boosting, this invention achieves a two-stage boosting method by connecting the voltage conversion circuit in series with a "Boost circuit formed by the first inductor L1 and the first arm of the three-arm converter circuit." This allows the Boost circuit, composed of the first inductor L1 and the first arm of the three-arm converter circuit, to share some of the voltage boosting operation, thereby achieving a larger boost ratio while eliminating the need for the voltage conversion circuit itself to perform a large voltage difference boosting process. The smaller the voltage difference between the input and output voltages of the voltage conversion circuit, i.e., the smaller the boost ratio, the higher the voltage conversion efficiency of the voltage conversion circuit. Therefore, this two-stage boosting method improves the conversion efficiency of the voltage conversion circuit, thereby reducing the current stress risk and heat loss risk of the voltage conversion circuit, and improving the reliability of UPS systems with low-voltage, high-current batteries.

[0085] In battery-powered mode, the battery pack serves as the input source for the voltage conversion circuit, and the output of the voltage conversion circuit powers the three-arm converter circuit. At this time, the three-arm converter circuit operates in DC-AC mode. For example, the first arm and the first inductor L1 of the three-arm converter circuit operate in Boost mode, the DC bus capacitor E1 filters the boosted DC power to obtain a stable DC power, and the third arm operates in inverter mode, converting the stable DC power into AC power and outputting it to the load to power it. Simultaneously, the DC bus capacitor E1 can store energy. In this battery-powered mode, both the voltage conversion circuit and the three-arm converter circuit participate in the operation; that is, all components of the three-arm topology device are involved in the operation.

[0086] It is understood that the voltage conversion circuit involved in the embodiments of the present invention can be any circuit with bidirectional voltage conversion function. For example, a voltage conversion circuit with soft switching, a voltage conversion circuit with hard switching, etc. This voltage conversion circuit can be a voltage conversion circuit with electrical isolation or a voltage conversion circuit without electrical isolation. For example, this voltage conversion circuit can also be called a DC-DC converter.

[0087] Figure 3 Schematic diagram of the first three-arm topology device provided by the present invention Figure 2 ,like Figure 3As shown, for example, the voltage conversion circuit involved in the embodiments of the present invention may include: a fourth bridge arm, a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, a transformer TX11, a third inductor L3, a second capacitor C2, and a third capacitor E2.

[0088] The fourth bridge arm includes a seventh switch Q7 and an eighth switch Q8, with the first end of the seventh switch Q7 connected to the first end of the eighth switch Q8. The common terminal of the seventh switch Q7 and the eighth switch Q8 is referred to as the midpoint of the fourth bridge arm.

[0089] The fifth bridge arm includes a ninth switch Q9 and a tenth switch Q10, with the first end of the ninth switch Q9 connected to the first end of the tenth switch Q10. The common end of the ninth switch Q9 and the tenth switch Q10 is then referred to as the midpoint of the fifth bridge arm.

[0090] The sixth bridge arm includes an eleventh switch Q11 and a twelfth switch Q12, with the first end of the eleventh switch Q11 connected to the first end of the twelfth switch Q12. The common end of the eleventh switch Q11 and the twelfth switch Q12 is then referred to as the midpoint of the sixth bridge arm.

[0091] The seventh bridge arm includes a thirteenth switch Q13 and a fourteenth switch Q14, with the first end of the thirteenth switch Q13 connected to the first end of the fourteenth switch Q14. The common terminal of the thirteenth switch Q13 and the fourteenth switch Q14 is then referred to as the midpoint of the seventh bridge arm.

[0092] The fourth bridge arm is connected in parallel with the fifth bridge arm. For example, the second end of the seventh switch Q7 is connected to the second end of the ninth switch Q9, and the second end of the eighth switch Q8 is connected to the second end of the tenth switch Q10.

[0093] The sixth bridge arm, the seventh bridge arm, and the third capacitor E2 are connected in parallel. For example, the second terminal of the eleventh switch Q11 is connected to the second terminal of the thirteenth switch Q13 and the first terminal of the third capacitor E2, and the second terminal of the twelfth switch Q12 is connected to the second terminal of the fourteenth switch Q14 and the second terminal of the third capacitor E2. It should be understood that the third capacitor E2 can be a DC capacitor used to provide filtering function so that the voltage conversion circuit provides a stable DC current when charging or discharging the battery pack.

[0094] The first terminal A of the transformer TX11 is connected to the midpoint of the fourth bridge arm, the second terminal B of the transformer TX11 is connected to the midpoint of the fifth bridge arm, the third terminal C of the transformer TX11 is connected to the midpoint of the fifth bridge arm through the third inductor L3 and the second capacitor C2, and the fourth terminal D of the transformer TX11 is connected to the midpoint of the sixth bridge arm.

[0095] In this voltage conversion circuit, the second terminal of the seventh switch Q7 is the positive terminal of the first terminal of the voltage conversion circuit, the second terminal of the eighth switch Q8 is the negative terminal of the first terminal of the voltage conversion circuit, the second terminal of the thirteenth switch Q13 is the positive terminal of the second terminal of the voltage conversion circuit, and the second terminal of the fourteenth switch Q14 is the negative terminal of the second terminal of the voltage conversion circuit.

[0096] When using Figure 3 In the voltage conversion circuit shown, when charging the battery pack, Q11, Q12, Q13, and Q14 act as switching transistors, while the external diodes (also known as parasitic diodes, etc.) of Q7, Q8, Q9, and Q10 act as rectifiers. Q11 and Q14 conduct simultaneously, as do Q12 and Q13. For example, a fixed-frequency, fixed-duty-cycle control method can be used to charge the battery pack. "Fixed duty cycle" here means using the same duty cycle for control, so that the conduction duration of Q11 and Q14 is the same as that of Q12 and Q13. "Fixed frequency" here refers to using a fixed frequency for voltage regulation control.

[0097] When using Figure 3 The voltage conversion circuit shown uses Q7, Q8, Q9, and Q10 as switching transistors during battery discharge, and the external diodes (also called parasitic diodes, etc.) of Q11, Q12, Q13, and Q14 as rectifiers. Q7 and Q10 conduct simultaneously, as do Q8 and Q9. For example, a variable frequency constant duty cycle control method can be used to discharge the battery pack. Here, constant duty cycle means using the same duty cycle to control Q7, Q8, Q9, and Q10, so that the conduction duration of Q7 and Q10 is the same as that of Q8 and Q9. Variable frequency refers to using frequency conversion for voltage regulation control.

[0098] The structure of the voltage conversion circuit described above enables soft switching. Soft-switching is a switching technique relative to hard-switching. Soft-switching technology allows the voltage of the switching transistor in the voltage conversion circuit to be reduced to zero before turn-on and the current to be reduced to zero before turn-off (i.e., zero-voltage turn-on and zero-current turn-off). This eliminates the overlap of voltage and current during the switching process, reduces their rate of change, and thus significantly reduces or even eliminates the switching losses in the voltage conversion circuit, enabling high-frequency operation of the voltage conversion circuit.

[0099] Because voltage conversion circuits with soft switching have poor voltage regulation capability. That is to say, when the voltage conversion circuit achieves voltage regulation with a large voltage difference, it can only achieve zero-voltage turn-on and cannot achieve zero-current turn-off. As a result, the voltage conversion circuit cannot achieve soft switching under all operating conditions of zero-voltage turn-on and zero-current turn-off. In other words, the voltage conversion circuit cannot operate under the full operating condition of zero-voltage turn-on and zero-current turn-off, which leads to a lower conversion efficiency than under the full operating condition, increasing the current stress risk and heat loss risk of the voltage conversion circuit.

[0100] Therefore, when the aforementioned voltage conversion circuit with soft switching is applied to the three-arm topology device provided in the embodiments of the present invention, by connecting the voltage conversion circuit in series with "the first inductor L1 and the first arm of the three-arm conversion circuit forming a Boost circuit", the voltage conversion circuit can achieve a soft-switching function with a fixed boost ratio (which, for example, can achieve voltage regulation with a small voltage difference), and the Boost circuit formed by the first inductor L1 and the first arm of the three-arm conversion circuit can achieve a voltage regulation function. That is, while obtaining a large boost ratio, the voltage conversion circuit with soft switching itself does not need to perform a large voltage difference boosting process. In this way, the voltage conversion circuit with soft switching can operate under the full operating condition of zero voltage turn-on and zero current turn-off, improving the conversion efficiency of the voltage conversion circuit with soft switching, thereby reducing the current stress risk and heat loss risk of the voltage conversion circuit with soft switching, and improving the reliability of the UPS system with low battery voltage and high current.

[0101] It should be understood that Figure 3 This is merely an illustration of a voltage conversion circuit with soft switching. In actual implementation, other voltage conversion circuits with soft switching can also be used in the embodiments of the present invention, which will not be elaborated further.

[0102] In addition, although the above Figure 3 Therefore, a voltage conversion circuit with electrical isolation (e.g.) Figure 3The diagram illustrates an example of a voltage conversion circuit where the transformer provides electrical isolation. However, it should be understood that the voltage conversion circuit described in this embodiment can be either electrically isolated or non-electrically isolated. For example, the voltage conversion circuit may have electrical isolation while the first arm of the three-arm converter circuit lacks electrical isolation; or, the voltage conversion circuit may lack electrical isolation while the first arm of the three-arm converter circuit has electrical isolation; or, the voltage conversion circuit may have electrical isolation while the first arm of the three-arm converter circuit has electrical isolation; or, the voltage conversion circuit may lack electrical isolation while the first arm of the three-arm converter circuit lacks electrical isolation, etc.

[0103] It should be noted that when the above-mentioned three-arm topology device switches from AC power supply mode to battery power supply mode, or from battery power supply mode to AC power supply mode, there is a certain time difference in the mode switching (for example, there may be a time difference of X seconds from AC power disconnection to battery power supply). Therefore, during this time difference, the three-arm topology device can use the voltage stored in the DC bus capacitor E1 to supply power to the load, so as to provide stable AC power to the load and avoid power loss to the load.

[0104] The three-arm topology device provided in this invention achieves battery charging or discharging through a voltage conversion circuit, eliminating the need for an additional charger. Furthermore, both the voltage conversion circuit and the three-arm switching circuit operate in both AC and battery-powered modes, meaning all components of the three-arm topology device are active. When this three-arm topology device is applied to a low-voltage, high-current UPS system, it improves component reuse, avoids redundant design, and ultimately reduces the cost of the UPS system.

[0105] The following example illustrates how the above-mentioned switch can be implemented:

[0106] Continue to refer to Figure 2 In a three-arm topology device, the switching switches may include, for example, a first switch K1, a second switch K2, and a balancing element.

[0107] In this circuit, the positive terminal of the second end of the voltage conversion circuit is connected to the fixed terminal of the first switch K1, the first selection terminal of the first switch K1 is connected to the first terminal of the balancing component, the second terminal of the balancing component is connected to BUS+, the second selection terminal of the first switch K1 is connected to the positive voltage input terminal AC_L, the first terminal of the second switch K2 is connected to the live wire of the AC mains power supply, the second terminal of the second switch K2 is connected to the positive voltage input terminal AC_L, and the negative terminal of the second end of the voltage conversion circuit is connected to BUS-.

[0108] In mains power supply mode, the fixed terminal of the first switch K1 is connected to the first selector terminal of the first switch K1, and the second switch K2 is closed. In battery power supply mode, the fixed terminal of the first switch K1 is connected to the second selector terminal of the first switch K1, and the second switch K2 is open. For example, the first switch K1 can be any selector switch that can be turned on or off according to a control signal, such as a double-throw relay, a bidirectional electronic switch, or a thyristor. The second switch K2 can be any switch that can be turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, or a thyristor.

[0109] The aforementioned balancing components are used to balance the voltage between the BUS and the voltage conversion circuit of the three-bridge-arm converter circuit in the mains power supply mode, thereby preventing a large current from being input to the voltage conversion circuit at the moment when the fixed terminal of the first switch K1 is connected to the first select terminal of the first switch K1, thus enabling overcurrent protection for the voltage conversion circuit.

[0110] Continue to refer to Figure 2 In one possible implementation, the aforementioned balancing component could be, for example, a varistor RZ.

[0111] Figure 4 This is a schematic diagram of a second three-arm topology device provided by the present invention. Figure 4 As shown, in the second possible implementation, the aforementioned balancing component can be, for example, a thermistor RT with a negative temperature coefficient.

[0112] Figure 5 This is a schematic diagram of the third three-arm topology device provided by the present invention. Figure 5 As shown, in the third possible implementation, the aforementioned balancing component can be, for example, a third inductor L3.

[0113] Figure 6 This is a schematic diagram of the fourth three-arm topology device provided by the present invention. Figure 6 As shown, in a fourth possible implementation, the balancing component can be, for example, a resistor R1. In this implementation, the switching switch may further include a third switch K3.

[0114] Continue to refer to Figure 6 The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the third switch K3, and the second end of the third switch K3 is connected to BUS+. Figure 7 This is a schematic diagram of the fifth three-arm topology device provided by the present invention. Figure 7 As shown, in the fifth possible connection method, the third switch K3 is connected in parallel with the resistor R1.

[0115] Reference Figure 6 or Figure 7The switch shown closes the third switch K3 in AC power mode, when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, so that the voltage conversion circuit charges the battery pack. In battery power mode, the third switch K3 is open.

[0116] For example, the third switch K3 mentioned above can be any switch that can be turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, a thyristor, etc.

[0117] It should be understood that the second switch K2 and the third switch K3 can be the same switch or different switches. For example, the second switch K2 can be a thyristor, and the third switch K3 can be a unidirectional electronic switch.

[0118] The following is based on Figure 6 Taking the structure of the three-arm topology shown as an example, the states of each switch, each switching transistor, and the current flow of the three-arm topology under different power supply modes are illustrated:

[0119] In AC power supply mode: the fixed terminal of the first switch K1 is connected to the first select terminal of the first switch K1, the second switch K2 is closed, and when the voltage difference between the BUS+ of the three-arm topology and the voltage conversion circuit of the three-arm topology is less than or equal to a preset threshold, the third switch K3 is closed. At this time, the voltage conversion circuit operates in Buck mode.

[0120] Figure 8 This is a schematic diagram of the current supply in the mains power mode for the fourth three-arm bridge topology device provided by the present invention. Figure 8 As shown, in the first stage of the positive half-cycle of the AC current, the second switch Q2 and the fourth switch Q4 controlling the three-arm converter circuit are turned on, while the first switch Q1 and the third switch Q3 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0121] 1. The live wire of the AC mains power supply → the first inductor L1 → the second switch Q2 → the fourth switch Q4 → the neutral wire of the AC mains power supply forms the energy storage circuit of inductor L1.

[0122] 2. BUS+ → Positive terminal of voltage conversion circuit → Positive terminal of battery pack → Negative terminal of battery pack → Negative terminal of voltage conversion circuit → BUS-, which constitutes the energy storage circuit of battery pack.

[0123] Figure 9 A schematic diagram of the current supply of the fourth three-arm bridge topology device provided by the present invention in the mains power supply mode is shown below. Figure 9As shown, in the second stage of the positive half-cycle of the alternating current, the first switch Q1 and the fourth switch Q4 are turned on, while the second switch Q2 and the third switch Q3 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0124] 1. The live wire of the AC mains power supply → first inductor L1 → first switch Q1 → DC bus capacitor E1 → fourth switch Q4 → neutral wire of the AC mains power supply constitutes an energy storage circuit in which inductor L1 and AC mains power simultaneously store energy for DC bus capacitor E1.

[0125] 2. BUS+ → Positive terminal of voltage conversion circuit → Positive terminal of battery pack → Negative terminal of battery pack → Negative terminal of voltage conversion circuit → BUS-, which constitutes the energy storage circuit of battery pack.

[0126] Figure 10 A schematic diagram of the current supply of the fourth three-arm bridge topology device provided by the present invention in the mains power supply mode is shown below. Figure 10 As shown, in the first stage of the negative half-cycle of the alternating current, the first switch Q1 and the third switch Q3 are turned on, while the second switch Q2 and the fourth switch Q4 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0127] 1. The neutral wire of the AC mains power supply → the third switch Q3 → the first switch Q1 → the first inductor L1 → the live wire of the AC mains power supply forms the energy storage circuit of inductor L1.

[0128] 2. BUS+ → Positive terminal of voltage conversion circuit → Positive terminal of battery pack → Negative terminal of battery pack → Negative terminal of voltage conversion circuit → BUS-, which constitutes the energy storage circuit of battery pack.

[0129] Figure 11 A schematic diagram of the current supply of the fourth three-arm bridge topology device provided by the present invention in the mains power supply mode is shown below. Figure 11 As shown, in the second stage of the negative half-cycle of the AC current, the second switch Q2 and the third switch Q3 are turned on, while the first switch Q1 and the fourth switch Q4 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0130] 1. The neutral wire of the AC mains power supply → the third switch Q3 → the DC bus capacitor E1 → the second switch Q2 → the first inductor L1 → the live wire of the AC mains power supply constitutes an energy storage circuit in which inductor L1 and the AC mains power supply simultaneously store energy for the DC bus capacitor E1.

[0131] 2. BUS+ → Positive terminal of voltage conversion circuit → Positive terminal of battery pack → Negative terminal of battery pack → Negative terminal of voltage conversion circuit → BUS-, which constitutes the energy storage circuit of battery pack.

[0132] Battery powered mode: The fixed terminal of the first switch K1 is connected to the second select terminal of the first switch K1, while the second switch K2 and the third switch K3 are disconnected. At this time, the voltage conversion circuit operates in Boost mode.

[0133] Figure 12 A schematic diagram of the current of the fourth three-arm bridge topology device provided by the present invention in battery-powered mode is shown below. Figure 12 As shown, in the first stage of the battery-powered mode, the second switch Q2 is turned on, while the first switch Q1, the third switch Q3, and the fourth switch Q4 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0134] The battery pack positive terminal → voltage conversion circuit positive terminal → first inductor L1 → second switch Q2 → voltage conversion circuit negative terminal → battery pack negative terminal forms the energy storage circuit of the first inductor L1.

[0135] Figure 13 A schematic diagram of the current supply of another three-arm topology device provided by the present invention in battery-powered mode is shown below. Figure 13 As shown, in the second stage of the battery-powered mode, the first switch Q1 is turned on, while the second switch Q2, the third switch Q3, and the fourth switch Q4 are turned off. At this time, the current flow in the three-arm topology is as follows:

[0136] The battery pack positive terminal → voltage conversion circuit positive terminal → first inductor L1 → first switching transistor Q1 → DC bus capacitor E1 → voltage conversion circuit negative terminal → battery pack negative terminal forms the energy storage circuit of DC bus capacitor E1.

[0137] It should be understood that, although the above Figures 8 to 12 The current flow of the three-arm topology shown is all in the direction of Figure 6 The fourth type of three-bridge topology is illustrated as an example. However, those skilled in the art will understand that the current flow, as well as the states of each switch and each switching transistor, also apply to this. Figure 7 The three-bridge topology shown is implemented on a similar principle, and will not be described in detail here.

[0138] In addition, when adopting Figures 2 to 5 For any three-arm topology device, the states of each switch, the states of each switching transistor, and the current flow in different modes are shown below:

[0139] In AC power supply mode: the fixed terminal of the first switch K1 is connected to the first select terminal of the first switch K1, and the second switch K2 is closed. At this time, the voltage conversion circuit operates in Buck mode.

[0140] In this mode, the state of each switch in the three-arm topology device under mains power supply mode is related to... Figure 6 The three-arm bridge topology shown has the same state for each switch in the AC power supply mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in mains power mode; see reference for details. Figures 8 to 11 The corresponding descriptions will not be repeated here.

[0141] Battery powered mode: The fixed terminal of the first switch K1 is connected to the second select terminal of the first switch K1, and the second switch K2 is disconnected. At this time, the voltage conversion circuit operates in Boost mode.

[0142] In this mode, the state of each switch in the three-arm topology device under battery power mode is similar to... Figure 6 The three-arm bridge topology shown has the same state for each switch in battery-powered mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in battery-powered mode; see reference for details. Figures 12 to 13 The corresponding descriptions will not be repeated here.

[0143] Figure 14 This is a schematic diagram of the sixth three-arm topology device provided by the present invention. Figure 4 As shown, in a three-arm topology device, the switching switch may include, for example, a first switch K1, a second switch K2, and a balancing element.

[0144] The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the first switch K1 and the first selection terminal of the second switch K2. The second end of the first switch K1 is connected to the first end of the balancing component. The second end of the balancing component is connected to BUS+. The second selection terminal of the second switch K2 is connected to the live wire of the AC power supply. The fixed terminal of the second switch K2 is connected to the positive voltage input terminal AC_L. The negative terminal of the second end of the voltage conversion circuit is connected to BUS-.

[0145] In mains power supply mode, the first switch K1 is closed, and the fixed terminal of the second switch K2 is connected to the second selector terminal of the second switch K2. In battery power supply mode, the first switch K1 is open, and the fixed terminal of the second switch K2 is connected to the first selector terminal of the second switch K2. For example, the first switch K1 can be any switch that can be turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, or a thyristor. The second switch K2 can be any selector switch that can be turned on or off according to a control signal, such as a double-throw relay, a two-way electronic switch, or a thyristor.

[0146] The aforementioned balancing components are used to balance the voltage between the BUS+ of the three-bridge-arm converter circuit and the voltage conversion circuit when the mains power supply is in mode, thereby preventing a large current from being input to the voltage conversion circuit at the moment when the fixed terminal of the first switch K1 is connected to the first select terminal of the first switch K1, thus enabling overcurrent protection for the voltage conversion circuit.

[0147] Continue to refer to Figure 14 The sixth possible implementation is that the aforementioned balancing component can be, for example, a varistor RZ.

[0148] Figure 15 This is a schematic diagram of the seventh three-arm topology device provided by the present invention. Figure 15 As shown, in the seventh possible implementation, the aforementioned balancing component can be, for example, a thermistor RT with a negative temperature coefficient.

[0149] Figure 16 This is a schematic diagram of the eighth three-arm topology device provided by the present invention. Figure 16 As shown, in the eighth possible implementation, the aforementioned balancing component can be, for example, a third inductor L3.

[0150] When using Figures 14 to 16 For any three-arm topology device, the states of each switch, the states of each switching transistor, and the current flow in different modes are shown below:

[0151] In AC power supply mode: the first switch K1 is closed, and the fixed terminal of the second switch K2 is connected to the second select terminal of the second switch K2. At this time, the voltage conversion circuit operates in Buck mode.

[0152] In this mode, the state of each switch in the three-arm topology device under mains power supply mode is related to... Figure 6 The three-arm bridge topology shown has the same state for each switch in the AC power supply mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in mains power mode; see reference for details. Figures 8 to 11 The corresponding descriptions will not be repeated here.

[0153] Battery powered mode: The first switch K1 is opened, and the fixed terminal of the second switch K2 is connected to the first select terminal of the second switch K2. At this time, the voltage conversion circuit operates in Boost mode.

[0154] In this mode, the state of each switch in the three-arm topology device under battery power mode is similar to... Figure 6 The three-arm bridge topology shown has the same state for each switch in battery-powered mode. The current flow of this three-arm bridge topology is... Figure 6The three-bridge topology shown has the same current flow in battery-powered mode; see reference for details. Figures 12 to 13 The corresponding descriptions will not be repeated here.

[0155] Figure 17 This is a schematic diagram of the ninth three-arm topology device provided by the present invention. Figure 17 As shown, in the ninth possible implementation, the balancing component can be, for example, a resistor R1. In this implementation, the switching switch may further include a third switch K3.

[0156] Continue to refer to Figure 17 The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the third switch K3, and the second end of the third switch K3 is connected to BUS+. Figure 18 This is a schematic diagram of the tenth three-arm topology device provided by the present invention. Figure 18 As shown, in the tenth possible connection method, the third switch K3 is connected in parallel with the resistor R1.

[0157] Reference Figure 17 or Figure 18 The switch shown closes the third switch K3 in AC power mode, when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, so that the voltage conversion circuit charges the battery pack. In battery power mode, the third switch K3 is open.

[0158] For example, the third switch K3 mentioned above can be any switch that can be turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, a thyristor, etc.

[0159] It should be understood that the first switch K1 and the third switch K3 can be the same switch or different switches. For example, the first switch K1 can be a thyristor, and the third switch K3 can be a unidirectional electronic switch.

[0160] When using Figures 17 to 18 For any three-arm topology device, the states of each switch, the states of each switching transistor, and the current flow in different modes are shown below:

[0161] In AC power supply mode: the first switch K1 is closed, the fixed terminal of the second switch K2 is connected to the second select terminal of the second switch K2, and the third switch K3 is closed when the voltage difference between the BUS of the three-arm topology and the voltage conversion circuit of the three-arm topology is less than or equal to a preset threshold. At this time, the voltage conversion circuit operates in Buck mode.

[0162] In this mode, the state of each switch in the three-arm topology device under mains power supply mode is related to... Figure 6The three-arm bridge topology shown has the same state for each switch in the AC power supply mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in mains power mode; see reference for details. Figures 8 to 11 The corresponding descriptions will not be repeated here.

[0163] Battery powered mode: Control switches K1 and K3 are disconnected, and the fixed terminal of switch K2 is connected to the first select terminal of switch K2. In this mode, the voltage conversion circuit operates in Boost mode.

[0164] In this mode, the state of each switch in the three-arm topology device under battery power mode is similar to... Figure 6 The three-arm bridge topology shown has the same state for each switch in battery-powered mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in battery-powered mode; see reference for details. Figures 12 to 13 The corresponding descriptions will not be repeated here.

[0165] Figure 19 This is a schematic diagram of the eleventh three-arm topology device provided by the present invention. Figure 19 As shown, in a three-arm topology device, the switching switches may include, for example, a first switch K1, a second switch K2, a third switch K3, and a balancing component.

[0166] The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the first switch K1 and the first end of the third switch K3. The second end of the first switch K1 is connected to the positive voltage input terminal AC_L. The first end of the second switch K2 is connected to the live wire of the AC power supply. The second end of the second switch K2 is connected to the positive voltage input terminal AC_L. The second end of the third switch K3 is connected to the first end of the balancing component. The second end of the balancing component is connected to BUS+. The negative terminal of the second end of the voltage conversion circuit is connected to BUS-.

[0167] In mains power supply mode, the first switch K1 is open, and the second switch K2 and the third switch K3 are closed; in battery power supply mode, the first switch K1 is closed, and the second switch K2 and the third switch K3 are open.

[0168] The aforementioned balancing components are used to balance the voltage between the BUS and the voltage conversion circuit of the three-bridge-arm converter circuit in the mains power supply mode, thereby preventing a large current from being input to the voltage conversion circuit at the moment the first switch K3 is closed, thus enabling overcurrent protection for the voltage conversion circuit.

[0169] Continue to refer to Figure 19In the eleventh possible implementation, the aforementioned balancing component can be, for example, a varistor RZ.

[0170] Figure 20 This is a schematic diagram of the twelfth three-arm topology device provided by the present invention. Figure 20 As shown, in the twelfth possible implementation, the aforementioned balancing component can be, for example, a thermistor RT with a negative temperature coefficient.

[0171] Figure 21 This is a schematic diagram of the thirteenth three-arm topology device provided by the present invention. Figure 21 As shown, in the thirteenth possible implementation, the aforementioned balancing component can be, for example, a third inductor L3.

[0172] When using Figures 19 to 21 For any three-arm topology device, the states of each switch, the states of each switching transistor, and the current flow in different modes are shown below:

[0173] Mains power supply mode: Control switch K1 to open, and switch K2 and switch K3 to close. At this time, the voltage conversion circuit operates in Buck mode.

[0174] In this mode, the state of each switch in the three-arm topology device under mains power supply mode is related to... Figure 6 The three-arm bridge topology shown has the same state for each switch in the AC power supply mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in mains power mode; see reference for details. Figures 8 to 11 The corresponding descriptions will not be repeated here.

[0175] Battery powered mode: Controls the first switch K1 to close, and the second switch K2 and the third switch K3 to open. At this time, the voltage conversion circuit operates in Boost mode.

[0176] In this mode, the state of each switch in the three-arm topology device under battery power mode is similar to... Figure 6 The three-arm bridge topology shown has the same state for each switch in battery-powered mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in battery-powered mode; see reference for details. Figures 12 to 13 The corresponding descriptions will not be repeated here.

[0177] Figure 22 This is a schematic diagram of the fourteenth three-arm topology device provided by the present invention. Figure 22As shown, in the fourteenth possible implementation, the balancing component can be, for example, a resistor R1. In this implementation, the switching switch may further include a fourth switch K4.

[0178] Continue to refer to Figure 22 The positive terminal of the second end of the voltage conversion circuit is connected to the first end of the fourth switch K4, and the second end of the fourth switch is connected to BUS+. Figure 23 This is a schematic diagram of the fifteenth three-arm topology device provided by the present invention. Figure 23 As shown, in the fifteenth possible connection method, the fourth switch K4 is connected in parallel with the resistor R1.

[0179] Reference Figure 22 or Figure 23 The switch shown closes the fourth switch K4 in AC power mode, when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, so that the voltage conversion circuit charges the battery pack. In battery power mode, the fourth switch K4 is open.

[0180] For example, the fourth switch K4 can be any switch that can be turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, a thyristor, etc.

[0181] In this embodiment, the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 can be any switch capable of being turned on or off according to a control signal, such as a single-throw relay, a one-way electronic switch, or a thyristor. It should be understood that the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 can be the same switch or different switches. For example, the first switch K1 can be a thyristor, while the second switch K2, the third switch K3, and the fourth switch K4 can be single-throw relays, etc. This embodiment does not limit this.

[0182] When using Figures 22 to 23 For any three-arm topology device, the states of each switch, the states of each switching transistor, and the current flow in different modes are shown below:

[0183] In AC power supply mode: the first switch K1 is opened, the second switch K2 and the third switch K3 are closed, and the fourth switch K4 is closed when the voltage difference between the BUS of the three-arm topology and the voltage conversion circuit of the three-arm topology is less than or equal to a preset threshold. At this time, the voltage conversion circuit operates in Buck mode.

[0184] In this mode, the state of each switch in the three-arm topology device under mains power supply mode is related to... Figure 6The three-arm bridge topology shown has the same state for each switch in the AC power supply mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in mains power mode; see reference for details. Figures 8 to 11 The corresponding descriptions will not be repeated here.

[0185] Battery powered mode: Controls the first switch K1 to close, and the second switch K2, the third switch K3, and the fourth switch K4 to open. At this time, the voltage conversion circuit operates in Boost mode.

[0186] In this mode, the state of each switch in the three-arm topology device under battery power mode is similar to... Figure 6 The three-arm bridge topology shown has the same state for each switch in battery-powered mode. The current flow of this three-arm bridge topology is... Figure 6 The three-bridge topology shown has the same current flow in battery-powered mode; see reference for details. Figures 12 to 13 The corresponding descriptions will not be repeated here.

[0187] It should be understood that the above Figure 2 , Figures 4 to 7 ,as well as, Figures 14 to 23 The switch shown is merely an example. Since there are many ways to implement switchboards, they will not be listed here in detail for applications in three-arm topologies. In actual implementation, a switchboard can be selected according to actual needs to control the voltage conversion circuit to charge the battery pack in AC power mode and to control the voltage conversion circuit to discharge the battery pack in battery power mode. This will not be elaborated further.

[0188] Furthermore, although the above three-arm topology circuits are illustrated using an example of a low-voltage, high-current battery UPS system, those skilled in the art will understand that the three-arm topology circuits can also be applied to other UPS systems (such as high-power UPS systems), or other systems that use different power sources (mains power or battery packs) under different circumstances (such as inverter systems), etc., which will not be elaborated further.

[0189] Furthermore, in the above Figure 2 , Figures 4 to 7 ,as well as, Figures 14 to 23 In the example of the three-arm topology shown, the voltage conversion circuit can be any circuit with bidirectional voltage conversion capability. For example, Figure 3 The voltage conversion circuits shown are not limited in this respect.

[0190] The present invention also provides an uninterruptible power supply system, comprising: an AC mains power supply, a load, and the three-arm topology device shown in the foregoing embodiments (e.g., Figure 2, Figures 4 to 7 ,as well as, Figures 14 to 23 (Any of the three-bridge topologies shown in the diagram). The live wire of the AC power supply is connected to the positive voltage input terminal AC_L of the three-bridge topology, the neutral wire of the AC power supply is connected to the negative voltage input terminal AC_N of the three-bridge topology, and the output terminal of the three-bridge topology is connected to the load.

[0191] The uninterruptible power supply system provided by this invention can be, for example, a battery-powered low-voltage high-current UPS system, or an online low-to-medium power UPS system.

[0192] The UPS system provided by this invention has a similar implementation principle and technical effect to the aforementioned three-arm topology device, and will not be described again here.

[0193] It is understood that the various designations used in this invention (e.g., first switch transistor, second switch transistor, first switch, second switch, etc.) are merely for ease of description and are not intended to limit the scope of the embodiments of this invention.

[0194] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-leg topology device, characterized by, The three-bridge-arm topological device comprises a battery pack, a voltage conversion circuit, a switching switch and a three-bridge-arm conversion circuit; The three-bridge-arm conversion circuit comprises a first bridge arm, a second bridge arm, a third bridge arm, a first inductor, a second inductor, a DC bus capacitor and a first capacitor; The first bridge arm comprises a first switch tube and a second switch tube connected in series; The second bridge arm comprises a third switch tube and a fourth switch tube connected in series; The third bridge arm comprises a fifth switch tube and a sixth switch tube connected in series; The first bridge arm, the second bridge arm, the third bridge arm and the DC bus capacitor are connected in parallel between a bus positive output end and a bus negative output end; a midpoint of the first bridge arm is connected with a first end of the first inductor, a second end of the first inductor is used as a positive voltage input end of the three-bridge-arm topological device; a midpoint of the second bridge arm is used as a negative voltage input end of the three-bridge-arm topological device; a midpoint of the third bridge arm is connected with a first end of the second inductor, a second end of the second inductor is used as an output end of the three-bridge-arm topological device, and is connected with a load and a first end of the first capacitor respectively, a second end of the first capacitor is connected with the negative voltage input end; A positive pole of the battery pack is connected with a positive pole of a first end of the voltage conversion circuit, a negative pole of the battery pack is connected with a negative pole of the first end of the voltage conversion circuit, a positive pole of a second end of the voltage conversion circuit is connected with the bus positive output end and the positive voltage input end through the switching switch respectively, a negative pole of the second end of the voltage conversion circuit is connected with the bus negative output end, a live wire of a commercial alternating current power supply is connected with the positive voltage input end through the switching switch, and a zero line of the commercial alternating current power supply is connected with the negative voltage input end; The switching switch is used for controlling the voltage conversion circuit to charge the battery pack in a commercial power supply mode, and connecting the voltage conversion circuit in series with a boost circuit composed of the first inductor and the first bridge arm to control the voltage conversion circuit to discharge the battery pack in a battery power supply mode; The switching switch comprises a balance component, and the balance component is any one of a pressure-sensitive resistor, a negative temperature coefficient thermistor and a third inductor; The voltage conversion circuit comprises a fourth bridge arm, a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, a transformer, a third inductor, a second capacitor and a third capacitor.

2. The apparatus of claim 1, wherein, The switching switch further comprises a first switch and a second switch; A fixed end of the first switch is connected with the positive pole of the second end of the voltage conversion circuit, a first selection end of the first switch is connected with a first end of the balance component, a second end of the balance component is connected with the bus positive output end, a second selection end of the first switch is connected with the positive voltage input end, a first end of the second switch is connected with the live wire of the commercial alternating current power supply, a second end of the second switch is connected with the positive voltage input end, and a negative pole of the second end of the voltage conversion circuit is connected with the bus negative output end; The balance component is used for balancing voltage between a bus and the voltage conversion circuit. In the mains power supply mode, the fixed end of the first switch is in communication with the first selection end of the first switch, and the second switch is closed; in the battery power supply mode, the fixed end of the first switch is in communication with the second selection end of the first switch, and the second switch is opened.

3. The apparatus of claim 2, wherein, The balancing component is a resistor, and the switching switch further comprises a third switch. The positive pole of the second end of the voltage conversion circuit is connected with the first end of the third switch, and the second end of the third switch is connected with the positive output end of the bus; or the third switch is connected in parallel with the resistor. In the mains power supply mode and when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the third switch is closed; in the battery power supply mode, the third switch is opened.

4. The apparatus of claim 1, wherein, The switching switch further comprises a first switch and a second switch. The positive pole of the second end of the voltage conversion circuit is connected with the first end of the first switch and the first end of the third switch respectively, the second end of the first switch is connected with the positive voltage input end, the first end of the second switch is connected with the live wire of the mains AC power supply, the second end of the second switch is connected with the positive voltage input end, the second end of the third switch is connected with the first end of the balancing component, the second end of the balancing component is connected with the positive output end of the bus, and the negative pole of the second end of the voltage conversion circuit is connected with the negative output end of the bus. The balancing component is used for balancing the voltage between the bus and the voltage conversion circuit. In the mains power supply mode, the first switch is closed, and the fixed end of the second switch is in communication with the second selection end of the second switch; in the battery power supply mode, the first switch is opened, and the fixed end of the second switch is in communication with the first selection end of the second switch.

5. The apparatus of claim 4, wherein, The balancing component is a resistor, and the switching switch further comprises a third switch. The positive pole of the second end of the voltage conversion circuit is connected with the first end of the third switch, and the second end of the third switch is connected with the positive output end of the bus; or the third switch is connected in parallel with the resistor. In the mains power supply mode and when the voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the third switch is closed; in the battery power supply mode, the third switch is opened.

6. The apparatus of claim 1, wherein, The switching switch further comprises a first switch, a second switch and a third switch. The positive pole of the second end of the voltage conversion circuit is connected with the first end of the first switch and the first end of the third switch respectively, the second end of the first switch is connected with the positive voltage input end, the first end of the second switch is connected with the live wire of the mains AC power supply, the second end of the second switch is connected with the positive voltage input end, the second end of the third switch is connected with the first end of the balancing component, the second end of the balancing component is connected with the positive output end of the bus, and the negative pole of the second end of the voltage conversion circuit is connected with the negative output end of the bus. The balancing component is used for balancing the voltage between the bus and the voltage conversion circuit. In the mains power supply mode, the first switch is closed, and the second switch and the third switch are opened; in the battery power supply mode, the first switch is opened, and the second switch and the third switch are closed.

7. The apparatus of claim 6, wherein, The balancing component is a resistor, and the switching switch further comprises a fourth switch. A positive electrode of a second end of the voltage conversion circuit is connected with a first end of the fourth switch, and a second end of the fourth switch is connected with the positive bus output end; or the fourth switch is connected in parallel with the resistor. In the mains power supply mode, and when a voltage difference between the bus and the voltage conversion circuit is less than or equal to a preset threshold, the fourth switch is closed; in the battery power supply mode, the fourth switch is opened.

8. The apparatus of claim 1, wherein, The fourth bridge arm comprises a seventh switch tube and an eighth switch tube, and a first end of the seventh switch tube is connected with a first end of the eighth switch tube. The fifth bridge arm comprises a ninth switch tube and a tenth switch tube, and a first end of the ninth switch tube is connected with a first end of the tenth switch tube. The sixth bridge arm comprises an eleventh switch tube and a twelfth switch tube, and a first end of the eleventh switch tube is connected with a first end of the twelfth switch tube. The seventh bridge arm comprises a thirteenth switch tube and a fourteenth switch tube, and a first end of the thirteenth switch tube is connected with a first end of the fourteenth switch tube. The fourth bridge arm and the fifth bridge arm are connected in parallel, the sixth bridge arm, the seventh bridge arm, and the third capacitor are connected in parallel, a first end of the transformer is connected with a midpoint of the fourth bridge arm, a second end of the transformer is connected with a midpoint of the fifth bridge arm, a third end of the transformer is connected with the midpoint of the fifth bridge arm through the third inductor and the second capacitor, and a fourth end of the transformer is connected with a midpoint of the sixth bridge arm. A second end of the seventh switch tube is a positive electrode of a first end of the voltage conversion circuit, a second end of the eighth switch tube is a negative electrode of the first end of the voltage conversion circuit, a second end of the thirteenth switch tube is a positive electrode of a second end of the voltage conversion circuit, and a second end of the fourteenth switch tube is a negative electrode of the second end of the voltage conversion circuit.

9. An uninterruptible power supply system characterized by comprising: The system comprises a mains AC power supply, a load, and a three-bridge-arm topology device as claimed in any one of claims 1 to 8. The firewire of the mains AC power supply is connected with the positive voltage input end of the three-bridge-arm topology device, the zero line of the mains AC power supply is connected with the negative voltage input end of the three-bridge-arm topology device, and the output end of the three-bridge-arm topology device is connected with the load.

10. A control method of a three-leg topology device, characterized by, The method is used for controlling the three-bridge-arm topology device as claimed in claim 2, and the method comprises: In the mains power supply mode, the fixed end of the first switch is controlled to be in communication with the first selection end of the first switch, and the second switch is closed; in the battery power supply mode, the fixed end of the first switch is controlled to be in communication with the second selection end of the first switch, and the second switch is opened.

11. The method of claim 10, wherein, The method further comprises: In the mains power supply mode, the third switch is controlled to be closed when a voltage difference between the bus and a voltage conversion circuit of the three-bridge-leg topology device is less than or equal to a preset threshold; in the battery power supply mode, the third switch is controlled to be opened.

12. A control method of a three-leg topology device, characterized by, The method is used for controlling the three-bridge-leg topology device as claimed in claim 4, and the method comprises: In the mains power supply mode, the first switch is controlled to be closed, and a fixed end of the second switch is in communication with a second selection end of the second switch; in the battery power supply mode, the first switch is controlled to be opened, and the fixed end of the second switch is in communication with a first selection end of the second switch.

13. The method of claim 12, wherein, The method further comprises: In the mains power supply mode, the third switch is controlled to be closed when a voltage difference between the bus and a voltage conversion circuit of the three-bridge-leg topology device is less than or equal to a preset threshold; in the battery power supply mode, the third switch is controlled to be opened.

14. A control method of a three-leg topology device, characterized by, The method is used for controlling the three-bridge-leg topology device as claimed in claim 6, and the method further comprises: In the mains power supply mode, the first switch is controlled to be opened, and the second switch and the third switch are controlled to be closed; in the battery power supply mode, the first switch is controlled to be closed, and the second switch and the third switch are controlled to be opened.

15. The method of claim 14, wherein, The method further comprises: In the mains power supply mode, the fourth switch is controlled to be closed when a voltage difference between the bus and a voltage conversion circuit of the three-bridge-leg topology device is less than or equal to a preset threshold; in the battery power supply mode, the fourth switch is controlled to be opened.

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