Operation Method of Power Factor Correction Circuit and Uninterruptible Power Supply Device

Abstract

The present invention provides an operation method for a power factor correction circuit of an uninterruptible power supply device. The power factor correction circuit includes two T-type converters, and each T-type converter includes four switches. The operation method includes: when the uninterruptible power supply device operates in a normal power supply mode, converting an AC input voltage into a positive bus voltage across a first capacitor and a negative bus voltage across a second capacitor, wherein the second capacitor is serially coupled to the first capacitor; and when the uninterruptible power supply device operates in a battery power supply mode, controlling the conduction states of the plurality of switches of the two T-type converters to balance the positive bus voltage and the negative bus voltage. The present invention also provides an operation method for an uninterruptible power supply device.

Description

Technical Field

[0001] The present invention relates to an operating method for a power factor correction (PFC) circuit of an uninterruptible power supply (UPS) device, and particularly to an operating method for a power factor correction circuit and an operating method for an uninterruptible power supply device. Background Art

[0002] Existing uninterruptible power supply products adopt a split bus topology and are connected with a single battery pack. When operating in the battery power supply mode, there are limitations in maintaining the balance between the positive bus voltage and the negative current bus voltage only through a DC-DC conversion circuit. To maintain the balance between the positive bus voltage and the negative current bus voltage, a balancing circuit is usually added to maintain the balance between the positive bus voltage and the negative current bus voltage. However, this additional balancing circuit not only increases the cost but also increases the circuit complexity. Summary of the Invention

[0003] An object of the present invention is to provide an operating method for a power factor correction circuit of an uninterruptible power supply device. The power factor correction circuit includes two T-type converters, and each T-type converter includes four switches. The operating method includes: when the uninterruptible power supply device operates in the normal power supply mode, converting an AC input voltage into a positive bus voltage across a first capacitor and a negative bus voltage across a second capacitor, where the second capacitor is serially coupled to the first capacitor; and when the uninterruptible power supply device operates in the battery power supply mode, controlling the conduction states of the multiple switches of the two T-type converters to balance the positive bus voltage and the negative bus voltage.

[0004] In some embodiments, the first T-type converter of the multiple T-type converters includes a first switch and a second switch serially coupled to each other, where the circuit after the first switch and the second switch are serially coupled is parallel to the circuit after the first capacitor and the second capacitor are serially coupled. The first T-type converter further includes a third switch and a fourth switch serially coupled to each other, where the circuit after the third switch and the fourth switch are serially coupled is located between a first inductor and a midpoint, where the midpoint is between the first capacitor and the second capacitor. The operating method further includes: when the uninterruptible power supply device operates in the battery power supply mode, turning off the first switch and the second switch and turning on the third switch and the fourth switch.

[0005] In some embodiments, the duration of the uninterruptible power supply device operating in the battery power supply mode includes a first duration and a second duration, and the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, adjusting the first duration and the second duration to balance the positive bus voltage and the negative bus voltage.

[0006] In some embodiments, the second T-type converter of the plurality of T-type converters includes a fifth switch and a sixth switch connected in series with each other, wherein the circuit after the fifth switch and the sixth switch are connected in series is connected in parallel with the circuit after the first capacitor and the second capacitor are connected in series, and the second T-type converter further includes a seventh switch and an eighth switch connected in series with each other, wherein the circuit after the seventh switch and the eighth switch are connected in series is located between the midpoint and the second inductor, and the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, during the first duration, turning on the fifth switch and turning off the sixth switch and the seventh switch.

[0007] In some embodiments, the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, during the second duration, turning off the fifth switch and the eighth switch and turning on the sixth switch.

[0008] In some embodiments, the operation method further includes: when the positive bus voltage is greater than the negative bus voltage, increasing the first duration.

[0009] In some embodiments, the operation method further includes: when the positive bus voltage is less than the negative bus voltage, increasing the second duration.

[0010] An object of the present invention is to further provide an operation method for an uninterruptible power supply device. The uninterruptible power supply device includes a power factor correction circuit, a DC-DC conversion circuit, and an inverter circuit. The inverter circuit is coupled to the power factor correction circuit and the DC-DC conversion circuit. The power factor correction circuit includes two T-type converters, and each T-type converter includes four switches. The operation method includes: when the uninterruptible power supply device operates in the normal power supply mode, converting the AC input voltage into a positive bus voltage across the first capacitor and a negative bus voltage across the second capacitor through the power factor correction circuit, wherein the second capacitor is connected in series with the first capacitor, and converting the positive bus voltage and the negative bus voltage into an AC output voltage through the inverter circuit; when the uninterruptible power supply device operates in the battery power supply mode, converting the DC input voltage into a positive bus voltage and a negative bus voltage through the DC-DC conversion circuit, and converting the positive bus voltage and the negative bus voltage into an AC output voltage through the inverter circuit; and when the uninterruptible power supply device operates in the battery power supply mode, controlling the conduction states of the plurality of switches of the two T-type converters to balance the positive bus voltage and the negative bus voltage.

[0011] In some embodiments, the first T-type converter of the plurality of T-type converters includes a first switch and a second switch coupled in series with each other, wherein the circuit after the series connection of the first switch and the second switch is connected in parallel with the circuit after the series connection of a first capacitor and a second capacitor, wherein the first T-type converter further includes a third switch and a fourth switch coupled in series with each other, wherein the circuit after the series connection of the third switch and the fourth switch is located between a first inductor and a midpoint, wherein the midpoint is located between the first capacitor and the second capacitor, and wherein the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, turning off the first switch and the second switch and turning on the third switch and the fourth switch.

[0012] In some embodiments, the duration of the uninterruptible power supply device operating in the battery power supply mode includes a first duration and a second duration, and wherein the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, adjusting the first duration and the second duration to balance the positive bus voltage and the negative bus voltage.

[0013] In some embodiments, the second T-type converter of the plurality of T-type converters includes a fifth switch and a sixth switch coupled in series with each other, wherein the circuit after the series connection of the fifth switch and the sixth switch is connected in parallel with the circuit after the series connection of the first capacitor and the second capacitor, wherein the second T-type converter further includes a seventh switch and an eighth switch coupled in series with each other, wherein the circuit after the series connection of the seventh switch and the eighth switch is located between the midpoint and a second inductor, and wherein the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, during the first duration, turning on the fifth switch and turning off the sixth switch and the seventh switch.

[0014] In some embodiments, the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, during the second duration, turning off the fifth switch and the eighth switch and turning on the sixth switch.

[0015] In some embodiments, the operation method further includes: when the positive bus voltage is greater than the negative bus voltage, increasing the first duration.

[0016] In some embodiments, the operation method further includes: when the positive bus voltage is less than the negative bus voltage, increasing the second duration.

[0017] In some embodiments, the power factor correction circuit further includes a relay, wherein the relay is coupled between an AC power supply for supplying an AC input voltage and the first inductor and the second inductor, and wherein the operation method further includes: when the uninterruptible power supply device operates in the battery power supply mode, turning off the relay.

[0018] In some embodiments, the above-mentioned uninterruptible power supply device further includes a balancing circuit, where the balancing circuit is coupled to a power factor correction circuit, a DC-DC conversion circuit, and an inverter circuit, and the operation method further includes: during the transition time of turning off the relay, balancing the positive bus voltage and the negative bus voltage through the balancing circuit.

[0019] To make the above features and advantages of the present invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows. Description of the Drawings

[0020] A better understanding of the embodiments of the present invention can be obtained from the following detailed description in conjunction with the drawings of the specification. It should be noted that, according to the standard practice in the industry, the features are not shown to scale. In fact, for the sake of clearer discussion, the dimensions of each feature can be arbitrarily increased or decreased.

[0021] Figure 1 is a circuit diagram of an uninterruptible power supply device according to an embodiment of the present invention.

[0022] Figure 2 is a circuit diagram of a power factor correction circuit of an uninterruptible power supply device according to an embodiment of the present invention.

[0023] Figure 3 is an equivalent circuit diagram of the power factor correction circuit when the uninterruptible power supply device operates in the battery-powered mode according to an embodiment of the present invention.

[0024] Figure 4a is an equivalent circuit diagram of the power factor correction circuit during a first duration when the uninterruptible power supply device operates in the battery-powered mode according to a first embodiment of the present invention.

[0025] Figure 4b is an equivalent circuit diagram of the power factor correction circuit during a second duration when the uninterruptible power supply device operates in the battery-powered mode according to a first embodiment of the present invention.

[0026] Figure 4c is an equivalent circuit diagram of the power factor correction circuit during a second duration when the uninterruptible power supply device operates in the battery-powered mode according to a second embodiment of the present invention.

[0027] Figure 4d is an equivalent circuit diagram of the power factor correction circuit during a first duration when the uninterruptible power supply device operates in the battery-powered mode according to a second embodiment of the present invention.

[0028] Figure 5 is a circuit diagram of a three-phase power factor correction circuit of an uninterruptible power supply device according to an embodiment of the present invention.

[0029] Description of Reference Numerals

[0030] 10: AC power supply

[0031] 20: Battery

[0032] 30: Load

[0033] 100: Uninterruptible power supply device

[0034] 110: Power factor correction circuit

[0035] 120: DC-DC conversion circuit

[0036] 130: Inverter circuit

[0037] 140: Balancing circuit

[0038] BAT+, BAT-: DC terminals

[0039] C1: First capacitor

[0040] C2: Second capacitor

[0041] D1-D8: Diodes

[0042] L1: First inductor

[0043] L2: Second inductor

[0044] Lin_A, Lin_B, Lin_C: AC input voltages

[0045] Lo_A, Lo_B, Lo_C: AC output voltages

[0046] N: Midpoint

[0047] NL: Neutral line

[0048] RL: Relay

[0049] Q1-Q8: Switches

[0050] T1-T8: Switching elements

[0051] V1: Positive bus voltage

[0052] V2: Negative bus voltage

[0053] VDC+: First terminal

[0054] VDC-: Second terminal Detailed implementation manners

[0055] Embodiments of the present invention are discussed in detail below. However, it can be understood that the embodiments provide many applicable concepts that can be implemented in a variety of specific contexts. The discussed and disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Regarding the use of "first", "second",... etc. in this text, it does not particularly refer to the meaning of order or sequence, but is only used to distinguish elements or operations described by the same technical term.

[0056] Figure 1 It is a circuit diagram of an uninterruptible power supply (UPS) device 100 according to an embodiment of the present invention. Figure 1 The shown uninterruptible power supply device 100 is a three-phase uninterruptible power supply device. The uninterruptible power supply device 100 includes a power factor correction (PFC) circuit 110, a DC-DC conversion circuit 120, an inverter circuit 130, and a balance circuit 140. The inverter circuit 130 is coupled to the power factor correction circuit 110 and the DC-DC conversion circuit 120. The balance circuit 140 is coupled to the power factor correction circuit 110, the DC-DC conversion circuit 120, and the inverter circuit 130.

[0057] When the AC power supply 10 operates normally, the uninterruptible power supply device 100 operates in the normal power supply mode, so that the power factor correction circuit 110 converts the AC input voltage (i.e., the three-phase AC input voltages Lin_A, Lin_B, Lin_C supplied by the AC power supply 10 as shown) into the positive bus voltage V1 across the first capacitor C1 (i.e., the voltage difference between the first terminal VDC+ and the midpoint N) and the negative bus voltage V2 across the second capacitor C2 (i.e., the voltage difference between the midpoint N and the second terminal VDC-), where the second capacitor C2 is serially coupled to the first capacitor C1, and then the inverter circuit 130 converts the positive bus voltage V1 and the negative bus voltage V2 into an AC output voltage (i.e., the three-phase AC output voltages Lo_A, Lo_B, Lo_C as shown) and transmits the AC output voltage to the load 30. Figure 1 When the AC power supply 10 is abnormal, the uninterruptible power supply device 100 operates in the battery power supply mode, so that the DC-DC conversion circuit 120 converts the DC input voltage (i.e., as shown Figure 1 The three-phase AC output voltages Lo_A, Lo_B, Lo_C) and transmits the AC output voltage to the load 30.

[0058] When the AC power supply 10 is abnormal, the uninterruptible power supply device 100 operates in the battery power supply mode, so that the DC-DC conversion circuit 120 converts the DC input voltage (i.e., as shown Figure 1The voltage difference between the DC terminals BAT+ and BAT- powered by the battery 20 shown is converted into a positive bus voltage V1 and a negative bus voltage V2, and then the inverter circuit 130 converts the positive bus voltage V1 and the negative bus voltage V2 into an AC output voltage and transmits the AC output voltage to the load 30.

[0059] When an existing uninterruptible power supply operates in a battery-powered mode, the existing uninterruptible power supply requires an additional balancing circuit to balance the positive bus voltage and the negative bus voltage. However, the additional balancing circuit of the existing uninterruptible power supply not only increases the cost but also increases the circuit complexity. In view of this, an object of the present invention is to utilize the power factor correction circuit 110 to balance the positive bus voltage V1 and the negative bus voltage V2 when the uninterruptible power supply 100 operates in a battery-powered mode.

[0060] Figure 2 is a circuit diagram of the power factor correction circuit 110 of the uninterruptible power supply 100 according to an embodiment of the present invention. The power factor correction circuit 110 includes a first T-type converter and a second T-type converter. The first T-type converter is composed of four switches Q1, Q2, Q3, and Q4, and the second T-type converter is composed of four switches Q5, Q6, Q7, and Q8. It should be noted that Figure 2 the power factor correction circuit 110 shown is a single-phase circuit, and Figure 2 the input signal of the power factor correction circuit 110 shown is a single-phase AC input voltage Lin_A. The three-phase power factor correction circuit will be shown later Figure 5 shown.

[0061] The switches of the T-type converter may include metal-oxide-semiconductor field effect transistors (MOSFETs), gallium nitride (GaN), or bipolar transistors (BJTs), but the present invention is not limited thereto. In some embodiments of the present invention, each of the switches Q1-Q8 includes an insulated gate bipolar transistor (IGBT). As Figure 2As shown, switch Q1 includes a switching element T1 and a diode D1 that are coupled in parallel with each other. The diode D1 is used to provide a freewheeling current path when the switching element T1 is turned off. Similarly, switch Q2 includes a switching element T2 and a diode D2 that are coupled in parallel with each other, switch Q3 includes a switching element T3 and a diode D3 that are coupled in parallel with each other, switch Q4 includes a switching element T4 and a diode D4 that are coupled in parallel with each other, switch Q5 includes a switching element T5 and a diode D5 that are coupled in parallel with each other, switch Q6 includes a switching element T6 and a diode D6 that are coupled in parallel with each other, switch Q7 includes a switching element T7 and a diode D7 that are coupled in parallel with each other, and switch Q8 includes a switching element T8 and a diode D8 that are coupled in parallel with each other.

[0062] Regarding the first T-type converter, as Figure 2 shown, switch Q1 is serially coupled to switch Q2. Switch Q1 is coupled between the first terminal VDC+ of the first capacitor C1 and the first inductor L1, where the first inductor L1 is coupled to the AC power supply 10. Switch Q2 is coupled between the first inductor L1 and the second terminal VDC- of the second capacitor C2. In other words, the circuit formed by the series connection of switch Q1 and switch Q2 is in parallel with the circuit formed by the series connection of the first capacitor C1 and the second capacitor C2.

[0063] Regarding the first T-type converter, as Figure 2 shown, switch Q3 is serially coupled to switch Q4 in reverse (i.e., switch Q3 and switch Q4 are serially connected and arranged in reverse, configured in reverse). Switch Q3 is coupled between the first inductor L1 and switch Q4, and switch Q4 is coupled between switch Q3 and the midpoint N, where the midpoint N is located between the first capacitor C1 and the second capacitor C2. The midpoint N has the same potential as the neutral line NL.

[0064] Regarding the second T-type converter, as Figure 2 shown, switch Q5 is serially coupled to switch Q6. Switch Q5 is coupled between the first terminal VDC+ of the first capacitor C1 and the second inductor L2, where the second inductor L2 is coupled to the AC power supply 10. Switch Q6 is coupled between the second inductor L2 and the second terminal VDC- of the second capacitor C2. In other words, the circuit formed by the series connection of switch Q5 and switch Q6 is in parallel with the circuit formed by the series connection of the first capacitor C1 and the second capacitor C2.

[0065] Regarding the second T-type converter, as Figure 2As shown, switch Q7 is serially coupled in reverse to switch Q8 (i.e., switch Q7 and switch Q8 are serially connected and arranged in reverse, configured in reverse), switch Q7 is coupled between the second inductor L2 and switch Q8, and switch Q8 is coupled between switch Q7 and the midpoint N, where the midpoint N is located between the first capacitor C1 and the second capacitor C2.

[0066] When the uninterruptible power supply device 100 operates in the battery power supply mode, the conduction states of switches Q1 - Q8 are controlled to balance the positive bus voltage V1 and the negative bus voltage V2 by using the power factor correction circuit 110. The balance between the positive bus voltage V1 and the negative bus voltage V2 described herein means that the positive bus voltage V1 is close to the negative bus voltage V2 or even the positive bus voltage V1 is equal to the negative bus voltage V2.

[0067] In some embodiments of the present invention, when the uninterruptible power supply device 100 operates in the battery power supply mode, the power factor correction circuit 110 turns off the switching elements T1 and T2 and turns on the switching elements T3 and T4. It should be noted that the power factor correction circuit 110 controls the conduction states of the switching elements T1 - T4 by applying control signals to the switching elements T1 - T4 respectively. Figure 3 is an equivalent circuit diagram of the power factor correction circuit 110 when the uninterruptible power supply device 100 operates in the battery power supply mode according to an embodiment of the present invention. As Figure 3 shown in the equivalent circuit is used to balance the positive bus voltage V1 and the negative bus voltage V2 when the uninterruptible power supply device 100 operates in the battery power supply mode.

[0068] In some embodiments of the present invention, when the uninterruptible power supply device 100 operates in the battery power supply mode, the duration of operating the equivalent circuit as Figure 3 shown includes a first duration and a second duration. During the first duration, the equivalent circuit as Figure 3 shown is controlled to turn on the switching element T5 and turn off the switching elements T6 and T7, where the switching element T8 can be either on or off. During the second duration, the equivalent circuit as Figure 3 shown is controlled to turn off the switching elements T5 and T8 and turn on the switching element T6, where the switching element T7 can be either on or off. It should be noted that the power factor correction circuit 110 controls the conduction states of the switching elements T5 - T8 by applying control signals to the switching elements T5 - T8 respectively.

[0069] In the first embodiment of the present invention, when the positive bus voltage V1 is greater than the negative bus voltage V2, the control is such that the first duration is increased. Figure 4aIt is an equivalent circuit diagram of the power factor correction circuit 110 during a first duration when the uninterruptible power supply device 100 operates in a battery power supply mode according to a first embodiment of the present invention. As Figure 4a shown, the first capacitor C1 releases energy, causing the first inductor L1 and the second inductor L2 to store the energy released by the first capacitor C1. As a result, the positive bus voltage V1 decreases. Figure 4b It is an equivalent circuit diagram of the power factor correction circuit 110 during a second duration when the uninterruptible power supply device 100 operates in a battery power supply mode according to a first embodiment of the present invention. As Figure 4b shown, the first inductor L1 and the second inductor L2 release energy, causing the second capacitor C2 to store the energy released by the first inductor L1 and the second inductor L2. As a result, the negative bus voltage V2 increases.

[0070] In a second embodiment of the present invention, when the positive bus voltage V1 is less than the negative bus voltage V2, the control is such that the second duration is increased. Figure 4c It is an equivalent circuit diagram of the power factor correction circuit 110 during a second duration when the uninterruptible power supply device 100 operates in a battery power supply mode according to a second embodiment of the present invention. As Figure 4c shown, the second capacitor C2 releases energy, causing the first inductor L1 and the second inductor L2 to store the energy released by the second capacitor C2. As a result, the negative bus voltage V2 decreases. Figure 4d It is an equivalent circuit diagram of the power factor correction circuit 110 during a first duration when the uninterruptible power supply device 100 operates in a battery power supply mode according to a second embodiment of the present invention. As Figure 4d shown, the first inductor L1 and the second inductor L2 release energy, causing the first capacitor C1 to store the energy released by the first inductor L1 and the second inductor L2. As a result, the positive bus voltage V1 increases.

[0071] Therefore, when the uninterruptible power supply device 100 operates in a battery power supply mode, the positive bus voltage V1 and the negative bus voltage V2 can be balanced by adjusting the ratio of the first duration to the second duration. In the first embodiment of the present invention, when the positive bus voltage V1 is greater than the negative bus voltage V2, the adjustment is made to increase the ratio of the first duration to the second duration, thereby balancing the positive bus voltage V1 and the negative bus voltage V2. In the second embodiment of the present invention, when the positive bus voltage V1 is less than the negative bus voltage V2, the adjustment is made to decrease the ratio of the first duration to the second duration, thereby balancing the positive bus voltage V1 and the negative bus voltage V2.

[0072] As Figure 2As shown, the power factor correction circuit 110 further includes a relay RL. One end of the relay RL is coupled to the AC power supply 10, and the other end of the relay RL is coupled to the first inductor L1 and the second inductor L2. When the AC power supply 10 is abnormal, the uninterruptible power supply device 100 operates in the battery power supply mode, and controls to turn off the relay RL of the power factor correction circuit 110. However, during the transition time of turning off the relay RL of the power factor correction circuit 110, as Figure 3 shown, the equivalent circuit cannot be used to instantaneously balance the positive bus voltage V1 and the negative bus voltage V2. Therefore, during the transition time of turning off the relay RL of the power factor correction circuit 110, as Figure 1 shown, the balancing circuit 140 is used to balance the positive bus voltage V1 and the negative bus voltage V2.

[0073] Specifically, as Figure 1 shown, the balancing circuit 140 only needs to be enabled during the transition time of turning off the relay RL of the power factor correction circuit 110 (to balance the positive bus voltage V1 and the negative bus voltage V2 during the transition time of turning off the relay RL of the power factor correction circuit 110). When the uninterruptible power supply device 100 operates in the battery power supply mode, the power factor correction circuit 110 is used to balance the positive bus voltage V1 and the negative bus voltage V2. Therefore, the capacity of the balancing circuit 140 for balancing the positive bus voltage V1 and the negative bus voltage V2 according to the present invention can be reduced, thereby reducing the manufacturing cost of the uninterruptible power supply device 100 and increasing the power density of the uninterruptible power supply device 100.

[0074] Figure 5 is a circuit diagram of a three-phase power factor correction circuit of the uninterruptible power supply device 100 according to an embodiment of the present invention. The three-phase AC input voltages Lin_A, Lin_B, and Lin_C are respectively input to three single-phase power factor correction circuits as Figure 2 shown. The operation method of the three-phase power factor correction circuit as Figure 5 shown is similar to the operation method of the single-phase power factor correction circuit as Figure 2 shown, so it will not be described in detail.

[0075] In summary, the present invention proposes an operation method of an uninterruptible power supply device and an operation method of a power factor correction circuit of an uninterruptible power supply device. When the uninterruptible power supply device operates in the battery power supply mode, the power factor correction circuit is used to balance the positive bus voltage and the negative bus voltage. Therefore, the manufacturing cost of the uninterruptible power supply device can be reduced and the power density of the uninterruptible power supply device can be increased.

[0076] The features of several embodiments are outlined above, so that those skilled in the art can better understand the implementation manners of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures, thereby achieving the same objectives and / or attaining the same advantages as those introduced in these embodiments. Those skilled in the art should also understand that these equivalent constructs do not depart from the concept and scope of the present invention, and they can make various changes, substitutions and alterations without departing from the concept and scope of the present invention.

Claims

1. A method of operating a power factor correction circuit of an uninterruptible power supply device, wherein the power factor correction circuit includes two T-type converters, and each of the T-type converters includes four switches, and the method of operation includes: When the uninterruptible power supply device operates in a normal power supply mode, converting an AC input voltage into a positive bus voltage across a first capacitor and a negative bus voltage across a second capacitor, wherein the second capacitor is serially coupled to the first capacitor; And When the uninterruptible power supply device operates in a battery power supply mode, controlling the conduction states of the switches of the T-type converter to balance the positive bus voltage and the negative bus voltage, wherein a first T-type converter of the T-type converter includes a first switch and a second switch serially coupled to each other, and a circuit after the first switch and the second switch are serially connected is parallel to a circuit after the first capacitor and the second capacitor are serially connected, and the first T-type converter further includes a third switch and a fourth switch serially coupled to each other, and a circuit after the third switch and the fourth switch are serially connected is located between a first inductor and a midpoint, and the midpoint is located between the first capacitor and the second capacitor.

2. The method of operation according to claim 1, wherein the method of operation further includes: When the uninterruptible power supply device operates in the battery power supply mode, turning off the first switch and the second switch and turning on the third switch and the fourth switch.

3. The method of operation according to claim 2, wherein the duration of the uninterruptible power supply device operating in the battery power supply mode includes a first duration and a second duration, and the method of operation further includes: When the uninterruptible power supply device operates in the battery power supply mode, adjusting the first duration and the second duration to balance the positive bus voltage and the negative bus voltage.

4. The method of operation according to claim 3, wherein a second T-type converter of the T-type converter includes a fifth switch and a sixth switch serially coupled to each other, and a circuit after the fifth switch and the sixth switch are serially connected is parallel to a circuit after the first capacitor and the second capacitor are serially connected, and the second T-type converter further includes a seventh switch and an eighth switch serially coupled to each other, and a circuit after the seventh switch and the eighth switch are serially connected is located between the midpoint and a second inductor, and the method of operation further includes: When the uninterruptible power supply device operates in the battery power supply mode, during the first duration, turning on the fifth switch and turning off the sixth switch and the seventh switch.

5. The method of operation according to claim 4, further includes: When the uninterruptible power supply device operates in the battery power supply mode, during the second duration, turning off the fifth switch and the eighth switch and turning on the sixth switch.

6. The method of operation according to claim 3, further includes: When the positive bus voltage is greater than the negative bus voltage, increasing the first duration.

7. The method of operation according to claim 3, further includes: When the positive bus voltage is less than the negative bus voltage, increasing the second duration.

8. A method for operating an uninterruptible power supply device, wherein the uninterruptible power supply device includes a power factor correction circuit, a DC-DC conversion circuit, and an inverter circuit, wherein the inverter circuit is coupled to the power factor correction circuit and the DC-DC conversion circuit, wherein the power factor correction circuit includes two T-type converters, and each of the T-type converters includes four switches, and the method for operating includes: When the uninterruptible power supply device operates in a normal power supply mode, converting an AC input voltage into a positive bus voltage across a first capacitor and a negative bus voltage across a second capacitor through the power factor correction circuit, wherein the second capacitor is serially coupled to the first capacitor, and converting the positive bus voltage and the negative bus voltage into an AC output voltage through the inverter circuit; When the uninterruptible power supply device operates in a battery power supply mode, converting a DC input voltage into the positive bus voltage and the negative bus voltage through the DC-DC conversion circuit, and converting the positive bus voltage and the negative bus voltage into the AC output voltage through the inverter circuit; And When the uninterruptible power supply device operates in the battery power supply mode, controlling the conduction states of the switches of the T-type converter to balance the positive bus voltage and the negative bus voltage, wherein a first T-type converter of the T-type converter includes a first switch and a second switch serially coupled to each other, and a circuit after the first switch and the second switch are serially connected is parallel to a circuit after the first capacitor and the second capacitor are serially connected, and the first T-type converter further includes a third switch and a fourth switch serially coupled to each other, and a circuit after the third switch and the fourth switch are serially connected is located between a first inductor and a midpoint, and the midpoint is located between the first capacitor and the second capacitor.

9. The method for operating according to claim 8, wherein the method for operating further includes: When the uninterruptible power supply device operates in the battery power supply mode, turning off the first switch and the second switch and turning on the third switch and the fourth switch.

10. The method for operating according to claim 9, wherein a duration of the uninterruptible power supply device operating in the battery power supply mode includes a first duration and a second duration, and the method for operating further includes: When the uninterruptible power supply device operates in the battery power supply mode, adjusting the first duration and the second duration to balance the positive bus voltage and the negative bus voltage.

11. The method for operating according to claim 10, wherein a second T-type converter of the T-type converter includes a fifth switch and a sixth switch serially coupled to each other, and a circuit after the fifth switch and the sixth switch are serially connected is parallel to a circuit after the first capacitor and the second capacitor are serially connected, and the second T-type converter further includes a seventh switch and an eighth switch serially coupled to each other, and a circuit after the seventh switch and the eighth switch are serially connected is located between the midpoint and a second inductor, and the method for operating further includes: When the uninterruptible power supply device operates in the battery power supply mode, the fifth switch is turned on and the sixth switch and the seventh switch are turned off during the first duration.

12. The operating method according to claim 11, further comprising: When the uninterruptible power supply device operates in the battery power supply mode, the fifth switch and the eighth switch are turned off and the sixth switch is turned on during the second duration.

13. The operating method according to claim 10, further comprising: When the positive bus voltage is greater than the negative bus voltage, the first duration is increased.

14. The operating method according to claim 10, further comprising: When the positive bus voltage is less than the negative bus voltage, the second duration is increased.

15. The operating method according to claim 11, wherein the power factor correction circuit further comprises a relay, wherein the relay is coupled between an AC power supply for supplying the AC input voltage, the first inductor, and the second inductor, and the operating method further comprises: When the uninterruptible power supply device operates in the battery power supply mode, the relay is turned off.

16. The operating method according to claim 15, wherein the uninterruptible power supply device further comprises a balancing circuit, wherein the balancing circuit is coupled to the power factor correction circuit, the DC-DC conversion circuit, and the inverter circuit, and the operating method further comprises: During a transition time of turning off the relay, the positive bus voltage and the negative bus voltage are balanced by the balancing circuit.

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