Uninterruptible power supply and method for suppressing interference in uninterruptible power supply

Abstract

An uninterruptible power supply and a method for suppressing interference in an uninterruptible power supply are provided, the uninterruptible power supply including an input switch, an output switch, and an automatic voltage regulator connected between the input switch and the output switch, the output switch being selectively connected to one of the automatic voltage regulator and a battery, the automatic voltage regulator comprises a boost switch, a buck switch and a transformer switch, and the uninterruptible power supply is configured as follows: under the condition that the automatic voltage regulator works, when the input voltage is detected to be abnormal, the output switch is connected to the battery side to enter a second battery mode, and waits for a first time; then, the states of the boost switch, the buck switch and the transformer switch are controlled according to the input voltage; and waiting for a second time, and then controlling the state of the input switch according to the input voltage, the second time being greater than the first time.

Description

Technical Field

[0001] The present invention relates to the field of uninterruptible power supplies, and in particular to an online interactive uninterruptible power supply and a method for suppressing interference in the uninterruptible power supply. Background Art

[0002] The statements in this section are merely intended to provide background information related to the present invention to assist in understanding the present invention. Such background information does not necessarily constitute prior art.

[0003] In a backup uninterruptible power supply (UPS), the output voltage follows the input voltage when the mains power is present. However, since the UPS lacks regulation capabilities, in areas with harsh power grid conditions, when the mains voltage exceeds the load's tolerance, it can damage the load. To address this issue, a line-interactive UPS has been proposed, which incorporates an automatic voltage regulator (AVR) between the input and output. When the mains power exceeds the permitted range, the AVR is connected to the UPS circuit to adjust the output voltage, enhancing protection for the output load. Summary of the Invention

[0004] In response to the above-mentioned problems in the prior art, the present invention provides an uninterruptible power supply, comprising an input switch, an output switch, and an automatic voltage regulator connected between the input switch and the output switch, wherein the output switch is selectively connected to one of the automatic voltage regulator and a battery, the automatic voltage regulator comprising a step-up switch, a step-down switch, and a transformer switch, and the uninterruptible power supply is configured as follows:

[0005] When the automatic voltage regulator is operating, when an abnormal input voltage is detected, the output switch is connected to the battery side to enter a second battery mode, waits for a first time, and then controls the states of the boost switch, the buck switch, and the transformer switch according to the input voltage; and waits for a second time, and then controls the state of the input switch according to the input voltage, wherein the second time is greater than the first time.

[0006] In one embodiment, after waiting for a first time, if the input voltage is not within a safe range, the system continues to wait for a third time, and then controls the states of the boost switch, the buck switch, and the transformer switch according to the input voltage.

[0007] In one embodiment, if the input voltage is within a safe range, the boost switch, the buck switch, and the transformer switch change states according to the input voltage, and after the uninterruptible power supply operates in the second battery mode for at least the minimum battery mode operating time, the output switch is controlled to switch to the automatic voltage regulator side.

[0008] In one embodiment, after continuing to wait for a third time, if the input voltage is not within a safe range, the transformer switch is controlled to be disconnected, the boost switch and the buck switch are in normal mode, and the uninterruptible power supply continues to operate in the second battery mode.

[0009] In one embodiment, after waiting for a second time, if the input voltage is within a safe range, the input switch remains on; if the input voltage is not within the safe range, the input switch is turned off.

[0010] In one embodiment, after the input switch is turned off, the uninterruptible power supply continues to read the state of the input voltage, and turns on the input switch if the input voltage is within a safe range.

[0011] In one embodiment, an input voltage abnormality flag is set, and whether the input voltage is within a safe range is determined by determining whether the input voltage abnormality flag is cleared.

[0012] In one embodiment, the second time is greater than or equal to the time it takes for the automatic voltage regulator to decay or reset the excitation current after the input voltage is powered off, and the second time is less than the sum of the first time and the third time.

[0013] In one embodiment, the boost switch and the buck switch switch switch states when the input voltage phase is 80°-100° or 260°-280°.

[0014] The present invention also provides a method for suppressing interference in an uninterruptible power supply, comprising: when an automatic voltage regulator in the uninterruptible power supply is operating, when an input voltage abnormality is detected, controlling the output switch of the uninterruptible power supply to be connected to the battery side, waiting for a first time, and then controlling the states of the boost switch, the buck switch and the transformer switch of the automatic voltage regulator according to the input voltage; and waiting for a second time, and then controlling the state of the input switch of the uninterruptible power supply according to the input voltage, wherein the second time is greater than the first time.

[0015] The method for suppressing interference in an uninterruptible power supply of the present invention can eliminate the interference source by improving the logic to eliminate the excitation energy without adding any extra circuits, that is, without increasing any cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a line-interactive UPS according to one embodiment is shown.

[0017] Figure 2 A flow chart of a method for suppressing interference in an uninterruptible power supply according to an embodiment of the present invention is shown.

[0018] Figure 3 The figure shows a waveform diagram of the mains power when it changes from low voltage to high voltage in the prior art.

[0019] Figure 4 The figure shows a waveform diagram of the mains power when the high voltage power is lost in the prior art.

[0020] Figure 5 The figure shows a waveform diagram when the mains voltage changes from low voltage to high voltage when the method of the present invention is used.

[0021] Figure 6 The figure shows a waveform diagram of the mains power when the high voltage power is lost when the method of the present invention is used. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be noted that the embodiments given in the present invention are only for illustration and do not limit the scope of protection of the present invention.

[0023] Figure 1 FIG1 shows a schematic diagram of an online interactive UPS according to an embodiment. Figure 1 As shown, the line-interactive UPS 100 includes an input EMI filter 102, an input (safety) switch 103, an automatic voltage regulator 104, an output switch 105, and an output EMI filter 106, which are sequentially connected between an AC input terminal 101 and an AC output terminal 107. The AC input terminal 101 is used to receive an input voltage, such as mains electricity. The following description uses mains electricity as an example. The AC output terminal 107 is used to output AC power to a load. The UPS 100 also includes a charging branch, which includes a charger 109 and a battery 108. One end of the charger 109 is connected to the battery 108, and the other end is connected to the node between the switch 105 and the output EMI filter 106. The UPS 100 also includes a discharging branch, which includes a battery 108, a DC / DC converter 110, and an inverter 111, which are sequentially connected. The output switch 105 can selectively connect one of the automatic voltage regulator 104 and the inverter 111 to the AC output terminal 107. The line-interactive UPS 100 further includes a control unit (not shown in the figure) for controlling the operation of the UPS. The control unit may be, for example, a microprocessor (MCU).

[0024] In one embodiment, the input switch 103 is configured as a double-pole single-throw relay or includes a switch unit 103a and a switch unit 103b. In one embodiment, the output switch 105 is a relay.

[0025] Figure 1Figure 1 shows the specific structure of the automatic voltage regulator 104. Automatic voltage regulator 104 includes a transformer Tr, a boost switch 104a, a buck switch 104b, and a transformer switch 104c. The boost switch 104a is operable to connect the input switch 103 to the first terminal T1 of the transformer Tr and one of the taps T3. The buck switch 104b is operable to connect the output switch 105 to the first terminal T1 of the transformer Tr and one of the taps T3. One end of the transformer switch 104c is connected to the second terminal T2 of the transformer Tr, and the other end is connected between the input switch 103 and the output switch 105. By configuring the transformer switch 104c, the automatic voltage regulator 104 can be connected to or disconnected from the UPS 100. By configuring the boost switch 104a and the buck switch 104b, the automatic voltage regulator 104 can be operated in either boost mode or buck mode. In one embodiment, the boost switch 104a, the buck switch 104b, and the transformer switch 104c are all relays.

[0026] Although Figure 1 The specific structure of the automatic voltage regulator 104 is shown in FIG. However, those skilled in the art will appreciate that this structure is merely an example and that automatic voltage regulators of other structures may also be used in actual applications. An automatic voltage regulator typically includes a transformer, a boost switch, a buck switch, and a transformer switch.

[0027] The following combination Figure 1 The working mode of UPS100 is described in detail.

[0028] (1) When the utility voltage is within the normal range, the online interactive UPS 100 is controlled to be in normal mode. The input switch 103 is controlled to be on, and the output switch 105 is controlled to connect the automatic voltage regulator 104 to the AC output terminal 107. The transformer switch 104c is disconnected, and the boost switch 104a and the buck switch 104b are both connected to the first terminal T1 of the transformer Tr, thereby disconnecting the automatic voltage regulator 104 from the UPS 100, and power is directly transmitted from the AC input terminal 101 to the AC output terminal 107. In this normal mode, the charger 109 is controlled to convert the AC power from the automatic voltage regulator 104 into DC power to charge the rechargeable battery 108.

[0029] (2) When the mains voltage is high, that is, higher than the normal range but still within the safe range, the online interactive UPS 100 is controlled to be in the automatic voltage step-down regulation mode. In this mode, the input switch 103 is controlled to be on, and the output switch 105 is controlled to connect the automatic voltage regulator 104 to the AC output terminal 107. The transformer switch 104c is turned on, the boost switch 104a is connected to the first terminal T1 of the transformer Tr, and the buck switch 104b is connected to the tap T3 of the transformer Tr. The automatic voltage regulator 104 operates in the step-down mode. The electric energy from the AC input terminal 101 is stepped down by the automatic voltage regulator 104 and then transmitted to the AC output terminal 107. In this automatic voltage step-down regulation mode, the charger 109 is controlled to convert the AC power from the automatic voltage regulator 104 into DC power to charge the rechargeable battery 108.

[0030] For ease of understanding, in one embodiment, the normal range refers to a voltage within a range of 180V-270V, and the safe range refers to a voltage within a range of 160V-180V or 270V-290V.

[0031] (3) When the mains voltage is low, that is, lower than the normal range but still within the safe range, the online interactive UPS 100 is controlled to be in the automatic voltage boost regulation mode. In which, the input switch 103 is controlled to be on, and the output switch 105 is controlled to connect the automatic voltage regulator 104 to the AC output terminal 107. The transformer switch 104c is turned on, the boost switch 104a is connected to the tap T3 of the transformer Tr, and the step-down switch 104b is connected to the first terminal T1 of the transformer Tr, and the automatic voltage regulator 104 operates in the boost mode. The electric energy from the AC input terminal 101 is boosted by the automatic voltage regulator 104 and transmitted to the AC output terminal 107. In this automatic voltage boost mode, the charger 109 is controlled to convert the AC power from the automatic voltage regulator 104 into DC power to charge the rechargeable battery 108.

[0032] (4) When the mains voltage is abnormal (e.g., the voltage is outside the safe range or the voltage jump is greater than the threshold), the online interactive UPS 100 is controlled to be in the first battery mode. In this case, the input switch 103 is controlled to be disconnected, and the output switch 105 is controlled to connect the battery 108 to the AC output terminal 107. The transformer switch 104c is disconnected, and the boost switch 104a and the buck switch 104b are connected to the first terminal T1 of the transformer Tr. The electric energy from the battery 108 is converted into DC by the DC / DC converter 110 and inverted by the inverter 111 before being output to the AC output terminal 107.

[0033] For ease of understanding, in the present invention, when the boost switch 104a and the buck switch 104b are both connected to the first terminal T1 of the transformer Tr, it is called the normal mode of the automatic voltage regulator 104; when the transformer switch 104c is turned on, the boost switch 104a is connected to the tap T3 of the transformer Tr, and the buck switch 104b is connected to the first terminal T1 of the transformer Tr, it is called the boost mode of the automatic voltage regulator 104; when the transformer switch 104c is turned on, the boost switch 104a is connected to the first terminal T1 of the transformer Tr, and the buck switch 104b is connected to the tap T3 of the transformer Tr, it is called the buck mode of the automatic voltage regulator 104.

[0034] Automatic voltage regulators are usually connected to the circuit through relays. The operation of relays often causes interference. This phenomenon is more serious when it comes to automatic voltage regulators. Because the magnetic flux of the automatic voltage regulator needs to be reset when it is disconnected, if there is no suitable circuit to absorb the excitation energy, serious interference will be generated, which will in turn affect sensitive devices in the circuit.

[0035] The inventors discovered that, under the above control logic, when the automatic voltage regulator is operating, after the control unit (e.g., MCU) samples a mains power anomaly, it switches to the first battery mode. Simultaneously, the mains input switch 103 and the transformer switch 104c are disconnected, and the boost switch 104a and the buck switch 104b are disconnected (i.e., in normal mode). At this time, the excitation current of the automatic voltage regulator 104 suddenly loses its circuit path, and a very high voltage is induced across the transformer Tr. This high dv / dt voltage will generate strong electromagnetic interference, affecting the normal operation of some sensitive devices (e.g., the MCU).

[0036] The present invention provides a method for suppressing interference in an uninterruptible power supply. Figure 2 FIG. 1 is a flow chart showing a method for suppressing interference in an uninterruptible power supply according to an embodiment of the present invention. Figure 2 As shown, the method includes:

[0037] Step 201: When the automatic voltage regulator is working and a mains power anomaly is detected, steps 202, 203 and 204 are executed simultaneously.

[0038] A mains power abnormality means that the mains voltage is outside a safe range or the mains voltage jump is greater than a threshold, for example, greater than 40V.

[0039] Step 202: The output switch is switched to the battery side, and the UPS enters the second battery mode.

[0040] Different from the first battery mode, in the second battery mode, only the output switch is switched to the battery side, and the states of other switches are not limited.

[0041] At this time, the UPS operates in the second battery mode for at least the minimum battery mode operating time (eg, 5 seconds).

[0042] Step 204: When a mains power anomaly is detected, a first waiting time is performed, during which the states of the boost switch, the buck switch, and the transformer switch remain unchanged. Step 204a is then executed to determine whether the mains power is within a safe range. If so, step 204b is executed, where the boost switch, the buck switch, and the transformer switch change their states based on the mains power. After the UPS has operated in the second battery mode for at least the minimum battery mode operating time, the output switch switches to the automatic voltage regulator. If not, step 204c is executed, where a third waiting time is continued, during which the states of the boost switch, the buck switch, and the transformer switch remain unchanged. Step 204d is then executed to determine whether the mains power is within a safe range. If so, step 204b is executed, where the boost switch, the buck switch, and the transformer switch change their states based on the mains power. After the UPS has operated in the second battery mode for at least the minimum battery mode operating time, the output switch switches to the automatic voltage regulator. If not, step 204e is executed, where the transformer switch is disconnected, the boost switch and the buck switch are in normal mode, and the UPS continues to operate in the second battery mode.

[0043] In one embodiment, a mains abnormality flag is set. When a mains abnormality is detected, the mains abnormality flag is set (e.g., set to 1). While waiting for the first time and the third time, the control unit reads the mains status at regular intervals (e.g., 20ms) to determine whether the mains is within a safe range. Once the mains is detected to be within a safe range, the mains abnormality flag is cleared. Therefore, in steps 204a and 204d, it is also possible to determine whether the mains is within a safe range by determining whether the mains abnormality flag is cleared. By setting the mains abnormality flag, it is possible to easily determine whether the mains is within a safe range, thereby simplifying the operating process.

[0044] In one embodiment, the first time and the third time are equal, both being 400 ms. In one embodiment, the first time and the third time range from 200 ms to 1000 ms. In one embodiment, the third time is shorter than the first time, so as to increase the sensitivity of the system detection.

[0045] In one embodiment, in step 204b, the boost switch and the buck switch switch switch states when the mains phase is 90° or 270° (i.e., the mains voltage is at its peak value). Because the excitation current is 90° out of phase with the mains voltage, the excitation current is 0 at this time, and the operation of the boost switch and the buck switch does not generate an induced voltage across the transformer. In one embodiment, in step 204b, the boost switch and the buck switch switch switch states when the mains phase is 80°-100° or 260°-280°. At this time, the excitation current is relatively small, the interference is relatively small, and the uninterruptible power supply will not be interfered with.

[0046] In step 204b, when it is detected that the mains power is low, the boost switch and the buck switch are configured to be in boost mode; when it is detected that the mains power is high, the boost switch and the buck switch are configured to be in buck mode; when it is detected that the mains power is within the normal range, the boost switch and the buck switch are configured to be in normal mode.

[0047] In one embodiment, in step 204e, the original states of the boost switch, the buck switch, and the transformer switch may be maintained unchanged because, at this time, the input switch has been disconnected and the states of the boost switch, the buck switch, and the transformer switch will not affect the uninterruptible power supply.

[0048] Although the above embodiment includes two waiting steps, namely step 204 and step 204c, those skilled in the art will appreciate that more or fewer waiting steps may be provided. For example, after step 204d, if the AC power is not within a safe range, the system continues to wait for a fourth time, and then determines whether the AC power is within a safe range. If so, the system proceeds to step 204b; if not, the system proceeds to step 204e. In one embodiment, the fourth time is less than the third time. In another embodiment, the fourth time, the third time, and the first time are equal.

[0049] In one embodiment, after step 204e, the UPS may continue to read the mains power status, and if it is determined that the mains power is within a safe range, step 204b is further executed.

[0050] Step 203: When a mains power anomaly is detected, a second time period is waited, during which the input switch remains unchanged. Step 203a is then executed to determine whether the mains power is within a safe range. If so, step 203b is executed to keep the input switch on. If not, step 203c is executed to turn the input switch off.

[0051] In one embodiment, while waiting for the second time, the control unit reads the mains power status at regular intervals (e.g., 20ms) to determine whether the mains power is within a safe range. Once the mains power is detected to be within a safe range, the mains power abnormality flag is cleared. Therefore, in step 203a, whether the mains power is within a safe range can also be determined by determining whether the mains power abnormality flag is cleared.

[0052] According to UPS operating specifications, when the mains power is abnormal, the input switch must be disconnected within 1 second, i.e., 1 second is counted from the time the mains power abnormality flag is set. Therefore, the second time is less than 1 second. In one embodiment, the second time is 600 ms. In another embodiment, the second time ranges from 200 ms to 1000 ms.

[0053] In one embodiment, the second time is greater than the first time and less than the sum of the first and third times, to ensure that the input switch can be disconnected before switching the boost switch, the buck switch, and the transformer switch. At this time, the operation of the boost switch, the buck switch, and the transformer switch does not interfere with the uninterruptible power supply. In one embodiment, the second time is greater than or equal to the time it takes for the automatic voltage regulator to decay or reset the excitation current after a mains power outage. That is, the second time is long enough to ensure that the excitation current can decay or reset to zero through the mains circuit if the mains power is actually lost.

[0054] In one embodiment, after the input switch is turned off in step 203c, the UPS may continue to read the mains power status. If it is determined that the mains power is within a safe range, step 203b is further executed to turn on the input switch.

[0055] The following describes the method for suppressing interference in an uninterruptible power supply according to the present invention by taking three specific embodiments as examples, wherein the first time is 400 ms, the second time is 600 ms, and the third time is 400 ms.

[0056] In the first embodiment, when the mains voltage jumps from low to high voltage, the control unit detects a mains power anomaly, sets the mains power anomaly flag, switches the output switch to the battery side, and the UPS enters the second battery mode. For the next 400 ms, the boost switch, buck switch, and transformer switch remain in the initial boost mode. After more than 400 ms, the control unit detects that the mains power is within a safe range and clears the mains power anomaly flag. At this point, the mains power is at a high voltage, and the boost and buck switches switch to the buck mode when the mains power phase is 90°. Because the excitation current is 90° out of phase with the mains voltage, the excitation current is zero at this point, and the switching operation does not generate an induced voltage across the transformer. For 600 ms after the mains power anomaly flag is set, the input switch remains on. After 600 ms, the mains power anomaly flag is cleared, and the input switch remains on. After the UPS operates in the second battery mode for 5 seconds (the minimum operating time in battery mode), the output switch switches to the automatic voltage regulator side, and the UPS enters the buck mode and continues to operate.

[0057] In a second embodiment, when the mains voltage jumps from high to low, the control unit detects a mains abnormality, sets the mains abnormality flag, and switches the output switch to the battery side, causing the UPS to enter the second battery mode. For the next 400 ms, the boost switch, buck switch, and transformer switch remain in the initial buck mode. After more than 400 ms, the control unit detects that the mains voltage is within a safe range, and the mains abnormality flag is cleared. At this point, the mains voltage is at a low voltage, and the boost and buck switches switch to boost mode when the mains phase is 90°. Because the excitation current is 90° out of phase with the mains voltage, the excitation current is zero at this point, and the switching operation does not generate an induced voltage across the transformer. For 600 ms after the mains abnormality flag is set, the input switch remains on. After 600 ms, the mains abnormality flag is cleared, and the input switch remains on. After the UPS operates in the second battery mode for 5 seconds (the minimum operating time in battery mode), the output switch switches to the mains side, and the UPS enters the buck mode and continues to operate.

[0058] In the third embodiment, when the mains power is actually cut off, the control unit detects a mains power anomaly, the mains power anomaly flag is set, the output switch is switched to the battery side, and the UPS enters the second battery mode. For 600ms after the mains power outage, the input switch remains closed, and the terminals of the automatic voltage regulator are clamped by the mains power terminal, with the voltage at 0. After 600ms, the input switch is opened. For 800ms after the mains power outage, the transformer switch, the boost switch, and the buck switch remain in their original states. After 800ms, the boost switch and the buck switch switch are switched to normal mode, the transformer switch is opened, the automatic voltage regulator is not connected to the UPS circuit, and the UPS continues to operate in the second battery mode.

[0059] Figure 3 The figure shows a waveform diagram of the prior art when the mains voltage changes from low voltage to high voltage. Figure 4 The waveform diagram of the mains power when the high voltage is cut off in the prior art is shown in FIG. Figure 3 and Figure 4 The lower figure is a magnified view of the waveform at the boxed position in the upper figure. As can be seen from the waveform, after the MCU detects a mains power anomaly, the output switch, input switch, boost switch, and transformer switch all operate rapidly within a short period of time. This results in no return path for the excitation energy within the automatic voltage regulator, generating a high voltage spike across the transformer. This high dv / dt voltage significantly interferes with the MCU's reset pin, potentially causing the MCU to reset.

[0060] Figure 5 The figure shows a waveform diagram of the mains power when it changes from low voltage to high voltage when the method of the present invention is used. Figure 6 The waveform diagram of the mains power when the high voltage power is lost is shown in FIG. Figure 5 and Figure 6 The figure below is an enlarged view of the waveform at the box position in the figure above. From the waveform, we can see that after the MCU detects the mains power anomaly, the output switch acts quickly, and the input switch chooses to act or not act according to the mains power status after 600ms. Figure 5 In the process, the boost switch, buck switch and transformer switch will be operated at 270° phase according to the mains status after 400ms to ensure that the excitation current is 0; Figure 6 In the circuit, the boost switch, buck switch and transformer switch will operate according to the mains status after 800ms, which ensures that the automatic voltage regulator has enough time to discharge the excitation energy through the mains circuit and no voltage spike will be generated at both ends of the automatic voltage regulator.

[0061] The present invention effectively and thoroughly suppresses interference by eliminating interference sources. The method of suppressing interference in an uninterruptible power supply of the present invention allows the input switch to select whether to disconnect based on the mains power status after a second time, and the boost switch, buck switch, and transformer switch to operate based on the mains power status after a first time and a third time. This ensures that the automatic voltage regulator has sufficient time to discharge excitation energy through the mains power circuit, and no voltage spikes are generated at both ends of the automatic voltage regulator. The method of suppressing interference in an uninterruptible power supply of the present invention can eliminate interference sources by improving logic to eliminate excitation energy or using existing circuits to create an excitation energy discharge circuit without adding additional circuits, that is, without increasing any costs.

[0062] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein but includes various changes and modifications that may be made without departing from the scope of the present invention.

Claims

1. An uninterruptible power supply comprising an input switch, an output switch, and an automatic voltage regulator connected between the input switch and the output switch, the output switch being selectively connected to one of the automatic voltage regulator and a battery, the automatic voltage regulator comprising a step-up switch, a step-down switch, and a transformer switch, the uninterruptible power supply being configured to: When the automatic voltage regulator is operating, when an abnormal input voltage is detected, the output switch is connected to the battery side to enter a second battery mode, waits for a first time, and then controls the states of the boost switch, the buck switch, and the transformer switch according to the input voltage; and waits for a second time, and then controls the state of the input switch according to the input voltage, wherein the second time is greater than the first time.

2. The uninterruptible power supply according to claim 1, wherein: After waiting for the first time, if the input voltage is not within the safety range, continue to wait for a third time, and then control the states of the boost switch, the buck switch, and the transformer switch according to the input voltage.

3. The uninterruptible power supply according to claim 1 or 2, wherein: If the input voltage is within a safe range, the boost switch, the buck switch, and the transformer switch change states according to the input voltage, and the uninterruptible power supply controls the output switch to switch to the automatic voltage regulator side after operating in the second battery mode for at least the minimum battery mode operating time.

4. The uninterruptible power supply according to claim 2, wherein: After continuing to wait for a third time, if the input voltage is not within a safe range, the transformer switch is controlled to be disconnected, the boost switch and the buck switch are in a normal mode, and the uninterruptible power supply continues to operate in the second battery mode.

5. The uninterruptible power supply according to claim 1, wherein: After waiting for a second time, if the input voltage is within a safe range, the input switch remains on; if the input voltage is not within the safe range, the input switch is turned off.

6. The uninterruptible power supply according to claim 5, wherein: After the input switch is turned off, the uninterruptible power supply continues to read the state of the input voltage, and turns on the input switch if the input voltage is within a safe range.

7. The uninterruptible power supply according to claim 1, wherein: An input voltage abnormality flag is set, and whether the input voltage is within a safe range is determined by determining whether the input voltage abnormality flag is cleared.

8. The uninterruptible power supply according to claim 2, wherein: The second time is greater than or equal to the time it takes for the automatic voltage regulator to decay or reset the excitation current after the input voltage is powered off, and the second time is less than the sum of the first time and the third time.

9. The uninterruptible power supply according to claim 3, wherein: The boost switch and the buck switch switch switch states when the input voltage phase is 80°-100° or 260°-280°.

10. A method for suppressing interference in an uninterruptible power supply, comprising: In the case where the automatic voltage regulator in the uninterruptible power supply is operating, when an input voltage abnormality is detected, the output switch of the uninterruptible power supply is controlled to be connected to the battery side, a first time is waited, and then the states of the boost switch, the buck switch and the transformer switch of the automatic voltage regulator are controlled according to the input voltage; and a second time is waited, and then the state of the input switch of the uninterruptible power supply is controlled according to the input voltage, wherein the second time is greater than the first time.

Images