Uninterruptible power supply
By introducing a drive circuit and controller into the uninterruptible power supply to control the on and off states of the thyristor, the problem of the thyristor being accidentally triggered when it is turned off is solved, thus achieving the effect of preventing fault propagation and improving reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-03-27
AI Technical Summary
In existing uninterruptible power supplies, thyristors are easily triggered when they are off, causing AC grid faults to spread to the load and affecting the operation of the load.
By introducing a drive circuit and controller into the uninterruptible power supply, the on and off states of the thyristor are controlled, ensuring that the thyristor is not falsely triggered when the AC power grid is abnormal, and that the voltage is discharged through the overvoltage protection device when the voltage is too high to prevent breakdown.
This effectively prevents the thyristor from being accidentally triggered when it is off, prevents AC power grid faults from spreading to the load, and improves the reliability and stability of the uninterruptible power supply.
Smart Images
Figure CN121749476A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power supply technology, and in particular to an uninterruptible power supply. Background Technology
[0002] like Figure 1 As shown, a medium-voltage uninterruptible power supply (UPS) includes two power supply branches: a main power supply branch with forward and reverse thyristors, and an auxiliary power supply branch with a DC / AC conversion circuit. When the AC power grid is normal, the main power supply branch supplies power to the load; when the AC power grid is abnormal, both the forward and reverse thyristors in the main power supply branch are disconnected, and the auxiliary power supply branch supplies power to the load.
[0003] When a high voltage is applied across either the forward or reverse thyristor, the thyristor may break down due to the high voltage. To prevent this, a breakover diode (BOD) is placed between the gate and anode of both the forward and reverse thyristors. Specifically, as shown below... Figure 2 As shown. When there is a reverse high voltage between the anode and cathode of the forward thyristor VT1, that is, when the anode and cathode of the reverse thyristor VT2 are subjected to a forward high voltage, BOD2 conducts, thereby causing the reverse thyristor VT2 to conduct, so as to realize the reverse high voltage protection of the forward thyristor VT1.
[0004] but Figure 2 The corresponding thyristor high-voltage breakdown protection scheme can lead to false triggering of the thyristor when it is in the off state. Specifically, under abnormal AC power grid conditions, when the AC power grid voltage reaches its maximum value and the AC voltage output from the auxiliary power supply branch reaches its minimum value, the voltage across BOD1 connected to the forward thyristor VT1 becomes excessively high. BOD1 may be mistakenly turned on, resulting in the forward thyristor VT1 being falsely triggered to conduct. Similarly, the reverse thyristor VT2 may also be falsely triggered to conduct. This can cause the AC power grid fault to propagate to the load, affecting its operation. Therefore, preventing false triggering of the thyristor when it is in the off state is crucial. Summary of the Invention
[0005] This application provides an uninterruptible power supply that can effectively prevent the thyristor from being accidentally triggered when it is in the off state, thereby improving the reliability of the uninterruptible power supply.
[0006] Firstly, this application provides an uninterruptible power supply (UPS). The UPS has a DC input terminal for connecting to a DC source, an AC input terminal for connecting to an AC power grid, and an AC output terminal for connecting to an AC load. The UPS includes a DC / AC conversion circuit, a main circuit switching circuit, and a controller. The DC / AC conversion circuit is connected between the DC input terminal and the AC output terminal, used to convert the DC power from the DC source into AC power and output it to the AC load in the event of an AC power grid anomaly. The main circuit switching circuit is connected between the AC input terminal and the AC output terminal, used to transfer the AC power from the AC power grid to the AC load when the AC power grid is normal. The main circuit switching circuit includes a switching unit, which includes a first thyristor and a second thyristor connected in reverse parallel. The UPS also includes a drive circuit for driving the first thyristor to turn on or off. The drive circuit includes a first diode, a first resistor, and a first switching transistor. The cathode of the first diode is connected to the gate of the first thyristor, the first resistor is connected between the anode of the first diode and the cathode of the first thyristor, and the first switching transistor is connected in parallel with the first resistor. The controller is used to control the first switching transistor to turn on when both the first thyristor and the second thyristor are turned off.
[0007] It is understandable that for a thyristor to switch from the off state to the on state, the following two conduction conditions must be met simultaneously: (1) the potential of the anode of the thyristor is higher than the potential of the cathode; (2) the potential of the gate of the thyristor is greater than the potential of the cathode, so as to generate a sufficiently large gate trigger current. Based on this, when the first thyristor is off, the controller can control the first switching transistor to conduct, thereby short-circuiting the first resistor, that is, making there no voltage between the gate and cathode of the first thyristor VT1, so that the first thyristor never meets the conduction condition (2), thereby avoiding the situation where the first thyristor is mistakenly triggered to conduct when it is off.
[0008] In a first possible implementation, the controller is further configured to turn off both the first and second thyristors in the event of an AC power grid anomaly. The solution provided in this application for preventing thyristor turn-off from being falsely triggered is applicable to scenarios involving AC power grid anomalies. In this scenario, since the uninterruptible power supply (UPS) can effectively prevent thyristor turn-off from being falsely triggered, it can also prevent the fault from spreading to the AC load during an AC power grid failure.
[0009] In a second possible implementation, the drive circuit further includes a second resistor and an overvoltage protection device. The second resistor is connected in series with the first resistor between the anode and cathode of the first thyristor. The overvoltage protection device is connected in parallel with the second resistor and is used to be in a conducting state when the voltage across the second resistor is greater than a first voltage threshold. The controller is also used to control the first switching transistor to turn off when either the first or second thyristor is conducting.
[0010] In this embodiment, the first switching transistor is in the off state when the second thyristor is turned on, so that when the reverse voltage on the second thyristor (i.e., the voltage between the anode and cathode when the potential of the cathode of the thyristor is higher than the potential of the anode) is too high, the driving circuit of the first thyristor can automatically drive the first thyristor to turn on normally to discharge the reverse voltage on the second thyristor, so as to avoid the second thyristor being broken down by the reverse high voltage.
[0011] In a third possible implementation, the controller is also used to control the first thyristor or the second thyristor to conduct when the AC power grid is normal, so as to transmit the electrical energy of the AC power grid to the AC load.
[0012] In a fourth possible implementation, the overvoltage protection device includes a breakdown diode or a transient voltage suppression diode.
[0013] In a fifth possible implementation, the controller is further configured to generate drive signals for the first thyristor and the second thyristor. The drive circuit also includes a signal generation circuit for generating a drive signal for the first switching transistor based on the drive signals for the first and second thyristors, specifically including:
[0014] When both the first thyristor and the second thyristor are turned off, the drive signals for the first thyristor and the second thyristor are both first-level signals, and the drive signal for the first switch is a second-level signal, which is opposite to the first-level signal; when the drive signal for the first switch is a second-level signal, the first switch is in the on state.
[0015] When the first thyristor is turned on and the second thyristor is turned off, the drive signal for the first thyristor is a second-level signal, the drive signal for the second thyristor is a first-level signal, and the drive signal for the first switching transistor is a first-level signal.
[0016] In this embodiment, the drive signal for the first switching transistor is generated by the signal generation circuit based on the drive signals for the first and second thyristors generated by the controller. Furthermore, the logical OR result of the drive signal for the first switching transistor and the drive signals for the first thyristor VT1 and the second thyristor VT2 is the opposite. In this embodiment, the controller does not need to additionally generate the drive signal for the first switching transistor, simplifying the control method.
[0017] In a sixth possible implementation, the driving circuit further includes a first capacitor connected in parallel with a first resistor for supplying power to the signal generation circuit.
[0018] In this embodiment, the signal generation circuit draws power from the first capacitor in the driving circuit, eliminating the need for an external power supply, which simplifies the circuit and reduces costs.
[0019] In a seventh possible implementation, the driving circuit further includes a first capacitor and a third resistor, wherein the third resistor is connected in series between the anode and cathode of the first thyristor and is connected between the first resistor and the second resistor. The first capacitor is connected in parallel with the series-connected first and third resistors to supply power to the signal generation circuit.
[0020] In this embodiment, the first capacitor in the driving circuit is connected in parallel with the first and third resistors that are connected in series. The voltage of the first capacitor is the sum of the voltage across the first resistor and the voltage across the third resistor. The voltage range of the first capacitor is larger, that is, it can provide a wider power supply range for the signal generation circuit and is more flexible.
[0021] In the eighth possible implementation, the driving circuit further includes a fourth resistor, which is connected in series between the anode and cathode of the first thyristor, and the fourth resistor is connected to the second resistor, with the resistance of the fourth resistor being greater than that of the second resistor.
[0022] In this embodiment, considering that when the thyristor is subjected to reverse voltage, the overvoltage protection device in the corresponding drive circuit may experience excessive reverse voltage and be damaged by the high voltage, the drive circuit connects a fourth resistor in series between the anode and cathode of the corresponding thyristor. By setting the resistance value of the fourth resistor to be greater than that of the second resistor, the reverse voltage across the second resistor is reduced, that is, the reverse voltage across the overvoltage protection device is reduced, thereby preventing the overvoltage protection device from being reverse-broken.
[0023] In a ninth possible implementation, the driving circuit further includes a second diode connected in parallel with a fourth resistor, which is used to be in a conducting state when the difference between the anode voltage and the cathode voltage of the first thyristor is greater than a second voltage threshold.
[0024] Understandably, when the first thyristor is subjected to a forward voltage (i.e., the voltage between the anode and cathode when the potential of the anode is higher than that of the cathode), the second diode conducts, and the fourth resistor is short-circuited by the second diode. This ensures that the fourth resistor, which prevents reverse breakdown when the first thyristor is subjected to a forward voltage, does not affect the normal operation of the drive circuit. In short, in this implementation, the fourth resistor has no effect when the first thyristor is subjected to a forward voltage; it only functions when the first thyristor is subjected to a reverse voltage.
[0025] In a tenth possible implementation, the driving circuit further includes a voltage regulator connected between the anode of the first diode and the connection between the first resistor and the first switching transistor, for being in a conducting state when the voltage across the first resistor is greater than a third voltage threshold.
[0026] In this embodiment, adding a voltage regulator to the driving circuit allows the driving circuit to trigger the first thyristor to conduct only when a higher voltage threshold is met, thereby avoiding mis-conduction of the first thyristor at lower voltages and reducing the conduction loss of the first thyristor.
[0027] In the eleventh possible implementation, the voltage regulator includes a Zener diode. Attached Figure Description
[0028] Figure 1 This is a structural diagram of a medium-voltage UPS provided by existing technology;
[0029] Figure 2 This is a schematic diagram of the structure of a thyristor protection circuit against high voltage breakdown provided by existing technology;
[0030] Figure 3 This is a schematic diagram illustrating the application scenario of the uninterruptible power supply provided in this application;
[0031] Figure 4 This is a schematic diagram of the structure of the uninterruptible power supply provided in this application;
[0032] Figure 5 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0033] Figure 6 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0034] Figure 7 This is a control timing diagram of the uninterruptible power supply provided in this application;
[0035] Figure 8 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0036] Figure 9 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0037] Figure 10 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0038] Figure 11 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0039] Figure 12 This is another structural schematic diagram of the uninterruptible power supply provided in this application;
[0040] Figure 13 This is a comparison chart showing the effectiveness of the uninterruptible power supply provided in this application in protecting against high voltage during differential lightning strikes. Detailed Implementation
[0041] The UPS provided in this application is applicable to various fields such as new energy smart microgrids, power transmission and distribution, and photovoltaic-storage hybrid power generation. It is suitable for different application scenarios, such as photovoltaic-storage hybrid power supply scenarios, communication equipment rooms, network rooms, business halls, laboratories, instrument rooms, control rooms, office environments, billing centers, precision control rooms, and process control centers. The following explanation uses a communication equipment room as an example.
[0042] See Figure 3 , Figure 3 This is a schematic diagram illustrating an application scenario of the uninterruptible power supply (UPS) provided in this application. In a communication equipment room setting, the UPS provided in this application is... Figure 3 The UPS shown has its AC input connected to the AC power grid, its DC input connected to a battery pack, and its AC output connected to the server. Under normal AC power grid conditions, the UPS transmits power from the grid to the server via the main circuit switch. Under abnormal AC power grid conditions, the UPS converts the DC power from the battery pack to AC power via a DC / AC converter before outputting it to the server. Thus, the UPS provides a stable and reliable AC power supply to the server, ensuring uninterrupted power supply.
[0043] If the UPS main switch circuit adopts Figure 2 The thyristor high-voltage breakdown protection circuit shown may cause the thyristor in the main circuit switch to be accidentally triggered and turned on during AC power grid anomalies, leading to the AC power grid fault spreading to the server. Based on this, this application provides an uninterruptible power supply (UPS) that can prevent the thyristor from being accidentally triggered when it is in the off state. The following is a related explanation... Figures 4 to 13 The working principle of the uninterruptible power supply provided in this application is illustrated with examples.
[0044] See Figure 4 , Figure 4 This is a structural schematic diagram of the uninterruptible power supply provided in this application. For example... Figure 4As shown, the DC input terminal of the uninterruptible power supply (UPS) 1 is used to connect to a DC source, the AC input terminal is used to connect to the AC power grid, and the AC output terminal is used to connect to an AC load. The UPS 1 includes a DC / AC conversion circuit 11, a main circuit switching circuit 12, and a controller 13. The DC / AC conversion circuit 11 is connected between the DC input terminal and the AC output terminal of the UPS 1, and is used to convert the DC power from the DC source into AC power and output it to the AC load in the event of an AC power grid anomaly. The main circuit switching circuit 12 is connected between the AC input terminal and the AC output terminal of the UPS 1, and is used to transfer the AC power from the AC power grid to the AC load when the AC power grid is normal. The main circuit switching circuit 12 includes a switching unit 121, which includes a first thyristor VT1 and a second thyristor VT2 connected in reverse parallel. Specifically, the anode of the first thyristor VT1 is connected to the cathode of the second thyristor VT2, and the anode of the second thyristor VT2 is connected to the cathode of the first thyristor VT1. Here, the first thyristor VT1 and the second thyristor VT2 in this application include thyristors (Silicon Controlled Rectifier, SCR), integrated gate-commutated thyristors (IGCT), gate-turn-off thyristors (GTO), etc.
[0045] The uninterruptible power supply 1 also includes a drive circuit 1211, which is used to drive the first thyristor VT1 to turn on or off. The drive circuit 1211 includes a first diode D11, a first resistor R11, and a first switch S11. The cathode of the first diode D11 is connected to the gate of the first thyristor VT1, the first resistor R11 is connected between the anode of the first diode D11 and the cathode of the first thyristor VT1, and the first switch S11 is connected in parallel with the first resistor R11.
[0046] When both the first thyristor VT1 and the second thyristor VT2 are turned off, the controller 13 controls the first switching transistor S11 to turn on.
[0047] It is understandable that for a thyristor to switch from the off state to the on state, the following two on conditions must be met simultaneously: (1) the potential of the anode of the thyristor is higher than the potential of the cathode; (2) the potential of the gate of the thyristor is greater than the potential of the cathode, so as to generate a sufficiently large gate trigger current. Based on this, when the first thyristor VT1 is off, the controller 13 can control the first switch S11 to conduct, thereby short-circuiting the first resistor R11, that is, making there no voltage between the gate G and the cathode K of the first thyristor VT1, so that the first thyristor VT1 never meets the on condition (2), thereby avoiding the situation where the first thyristor VT1 is mistakenly triggered to conduct when it is off.
[0048] The above-described scheme to prevent thyristor turn-on from being mistakenly triggered when the thyristor is turned off is applicable to AC power grid fault scenarios. Specifically, when the AC power grid is abnormal, that is, when the voltage at the AC input terminal of the uninterruptible power supply 1 is less than or equal to Vth1, or when the voltage at the AC input terminal of the uninterruptible power supply 1 is greater than or equal to Vth2, the controller 13 controls both the first thyristor VT1 and the second thyristor VT2 to turn off. When both the first thyristor VT1 and the second thyristor VT2 are turned off, the controller 13 controls the first switch S11 to turn on. Here, Vth1 is less than the rated voltage of the AC power grid, and Vth2 is greater than the rated voltage of the power grid. For example, Vth1 is 0.9 times the rated voltage of the AC power grid, and Vth2 is 1.1 times the rated voltage of the AC power grid.
[0049] It should be noted that the above description uses VT1 as the first thyristor as an example; in reality, the first thyristor could also be VT2. Furthermore, in the scenario of an AC power grid fault, it is necessary that none of the thyristors in the switching unit 121 be falsely triggered when turned off to prevent the AC power grid fault from propagating to the AC load. Based on this, the uninterruptible power supply 1 also includes a drive circuit 1212, which is used to drive the second thyristor VT2 to turn on or off. The drive circuit 1212 includes a first diode D12, a first resistor R12, and a first switching transistor S12. The connection relationships of the internal components of the drive circuit 1212, and the connection relationship between the drive circuit 1212 and the second thyristor VT2, can be found in the description of the corresponding part of the drive circuit 1211, and will not be repeated here.
[0050] Similarly, when both the first thyristor VT1 and the second thyristor VT2 are turned off, the controller 13 also controls the first switch S12 to turn on, so that there is no voltage between the gate G and the cathode K of the second thyristor VT2, so that the second thyristor VT2 never meets the conduction condition (2), thereby avoiding the situation where the second thyristor VT2 is mistakenly triggered to turn on when it is turned off, so as to avoid the AC grid fault from spreading to the AC grid.
[0051] Furthermore, if the reverse voltage across the first thyristor VT1 or the second thyristor VT2 is too high, the thyristor may break down due to the excessive reverse voltage. Therefore, each drive circuit also includes a second resistor and overvoltage protection devices. For example... Figure 5 As shown, the drive circuit 1211 further includes a second resistor R21 and an overvoltage protection device 12111. The second resistor R21 and the first resistor R11 are connected in series between the anode and cathode of the first thyristor VT1, and the overvoltage protection device 12111 is connected in parallel with the second resistor R21. The drive circuit 1212 further includes a second resistor R22 and an overvoltage protection device 12121. The second resistor R22 and the first resistor R12 are connected in series between the anode and cathode of the second thyristor VT2, and the overvoltage protection device 12121 is connected in parallel with the second resistor R22. Either the overvoltage protection device 12111 or the overvoltage protection device 12121 includes a breakdown diode or a transient voltage suppression diode.
[0052] Specifically, when the first thyristor VT1 experiences a reverse voltage, the anode and cathode of the second thyristor VT2 experience a forward voltage, which is divided by the series connection of the first resistor R12 and the second resistor R22. When the reverse voltage across the first thyristor VT1 is too high, the voltage across the second resistor R22 exceeds the first voltage threshold, and the overvoltage protection device 12121 conducts. At this time, the current flowing through the first resistor R12 increases, and correspondingly, the voltage across the first resistor R12 increases. When the voltage across the first resistor R12 increases to a level sufficient to generate a gate trigger current between the gate G and cathode K of the second thyristor VT2, the second thyristor VT2 conducts to discharge the excessive reverse voltage across the first thyristor VT1, thereby preventing the first thyristor VT1 from being broken down by the excessive reverse voltage. Similarly, when the reverse voltage of the second thyristor VT2 is too high, the drive circuit 1211 can automatically drive the first thyristor VT1 to conduct in order to discharge the excessive reverse voltage of the second thyristor VT2, thereby preventing the second thyristor VT2 from being broken down by the excessive reverse voltage.
[0053] Optionally, the driving circuit 1212 further includes a voltage regulator 12122. The voltage regulator 12122 is connected between the anode of the first diode D12 and the connection point of the first resistor R12 and the first switching transistor S12. It is used to turn on the circuit when the voltage across the first resistor R12 is greater than a third voltage threshold. The third voltage threshold is the turn-on voltage threshold of the voltage regulator 12122, which includes a Zener diode. The difference between including and not including the voltage regulator 12122 in the driving circuit 1212 is only that: when the driving circuit 1212 includes the voltage regulator 12122, the first voltage value used to generate the gate trigger current between the gate G and cathode K of the second thyristor VT2 is higher than the second voltage value used to generate the gate trigger current between the gate G and cathode K of the second thyristor VT2 when the driving circuit 1212 does not include the voltage regulator 12122. This allows the drive circuit 1212, including the voltage regulator 12122, to trigger the second thyristor VT2 to turn on only when a higher voltage threshold is met, thereby avoiding the second thyristor VT2 from being mis-turned on at a lower voltage and reducing the conduction loss of the second thyristor VT2.
[0054] When the drive circuit 1212 also includes a voltage regulator 12122, the working principle of the drive circuit 1212 driving the second thyristor VT2 to conduct if the reverse voltage across the first thyristor VT1 is too high is as follows: When the first thyristor VT1 experiences a reverse voltage, the anode and cathode of the second thyristor VT2 experience a forward voltage, which is divided by the series connection of the first resistor R12 and the second resistor R22. When the reverse voltage across the first thyristor VT1 is too high, the voltage across the second resistor R22 exceeds the first voltage threshold, and the overvoltage protection device 12121 conducts. At this time, the current flowing through the first resistor R12 increases, and correspondingly, the voltage across the first resistor R12 increases. When the voltage across the first resistor R12 is greater than the third voltage threshold, the voltage regulator 12122 is turned on, thereby generating a gate trigger current between the gate G and the cathode K of the second thyristor VT2, causing the second thyristor VT2 to turn on, so as to discharge the excessive reverse voltage on the first thyristor VT1, thereby preventing the first thyristor VT1 from being broken down by the excessive reverse voltage.
[0055] Similarly, the drive circuit 1211 also includes a voltage regulator 12112. For a description of the voltage regulator 12112, please refer to the description of the corresponding part of the voltage regulator 12122. It will not be repeated here.
[0056] Since the switching state (including on and off) of the first switch S11 directly affects whether the drive circuit 1211 fails, and the switching state of the first switch S12 directly affects whether the drive circuit 1212 fails, the controller 13 controls both the first switch S11 and the first switch S12 to turn off when either the first thyristor VT1 or the second thyristor VT2 is on. This ensures that when the reverse voltage across the first thyristor VT1 is too high, the drive circuit 1212 can normally drive the second thyristor VT2 to conduct, thereby dissipating the reverse voltage across the first thyristor VT1; and that when the reverse voltage across the second thyristor VT2 is too high, the drive circuit 1211 can normally drive the first thyristor VT1 to conduct, thereby dissipating the reverse voltage across the second thyristor VT2.
[0057] The above-described scheme to prevent thyristor breakdown due to high voltage is applicable to scenarios where the AC power grid is normal. Specifically, when the AC power grid is normal, that is, when the voltage at the AC input terminal of the uninterruptible power supply 1 is greater than Vth1 and less than Vth2, the controller 13 controls either the first thyristor VT1 or the second thyristor VT2 to conduct. Specifically, when the AC power grid is normal and the AC power grid voltage is in the positive half-cycle, the controller 13 controls the first thyristor VT1 to conduct and controls the second thyristor VT2 to turn off; when the AC power grid is normal and the AC power grid voltage is in the negative half-cycle, the controller 13 controls the first thyristor VT1 to turn off and controls the second thyristor VT2 to conduct. Simultaneously, when either the first thyristor VT1 or the second thyristor VT2 is conducting, the controller 13 controls both the first switch S11 and the first switch S12 to turn off.
[0058] Furthermore, in this application, the first switching transistors S11 and S12 can be directly controlled by the controller 13 or indirectly controlled by the controller 13; this application does not impose any restrictions on this. The following description uses the example of the controller 13 indirectly controlling the first switching transistors S11 and S12.
[0059] like Figure 6 As shown, the drive circuit 1211 further includes a signal generation circuit 12113, which generates a drive signal for the first switch S11 based on the drive signals for the first thyristor VT1 and the second thyristor VT2 generated by the controller 13. The drive circuit 1212 further includes a signal generation circuit 12123, which generates a drive signal for the first switch S12 based on the drive signals for the first thyristor VT1 and the second thyristor VT2 generated by the controller 13.
[0060] Here, the drive signal of the first switch S11 is the same as the drive signal of the first switch S12, and the logical OR result of the drive signal of the first switch S11 is the opposite of the drive signal of the first thyristor VT1 and the drive signal of the second thyristor VT2. Specifically, when both the first thyristor VT1 and the second thyristor VT2 are turned off, the drive signals of the first thyristor VT1 and the second thyristor VT2 are both first-level signals, and the drive signal of the first switch S11 is a second-level signal, which is opposite to the first-level signal; when the drive signal of the first switch S11 is a second-level signal, the first switch S11 is in the on state. When the first thyristor VT1 is turned on and the second thyristor VT2 is turned off, the drive signal for the first thyristor VT1 is a second-level signal, the drive signal for the second thyristor VT2 is a first-level signal, and the drive signal for the first switch S11 is a first-level signal. At this time, the first switch S11 is in the off state. When the first thyristor VT1 is turned off and the second thyristor VT2 is turned on, the drive signal for the first thyristor VT1 is a first-level signal, the drive signal for the second thyristor VT2 is a second-level signal, and the drive signal for the first switch S11 is a first-level signal. The first-level signal can be either a high-level signal or a low-level signal.
[0061] For example, if the first level signal is a low level signal, then the drive signals for the first thyristor VT1, the second thyristor VT2, and the first switching transistors S11 and S12 are as follows: (See [link to relevant documentation] for details.) Figure 7 .like Figure 7 As shown, under normal AC power grid conditions, when the drive signal for one of the first thyristors VT1 and the second thyristor VT2 is high, and the drive signal for the other thyristor is low, the first thyristor is turned on, and the other thyristor is turned off. Correspondingly, when the drive signals for the first switches S11 and S12 are both low, both switches S11 and S12 are off. At this time, the driving circuits 1211 and 1212 are both effective and can normally drive their corresponding thyristors to turn on. Under abnormal AC power grid conditions, when the drive signals for both the first thyristors VT1 and the second thyristor VT2 are low, both thyristors VT1 and VT2 are off. Correspondingly, when the drive signals for the first switches S11 and S12 are both high, both switches S11 and S12 are on. At this time, the driving circuits 1211 and 1212 are ineffective and cannot drive their corresponding thyristors to turn on.
[0062] Furthermore, the signal generation circuit in this application can draw power from an external power source or from its own driving circuit; this application does not impose any restrictions on this. The following description uses the example of the signal generation circuit drawing power from its own driving circuit.
[0063] Specifically, such as Figure 8 As shown, the driving circuit 1211 also includes a first capacitor C11, which is connected in parallel with a first resistor R11 to supply power to the signal generation circuit 12113. Specifically, when the second thyristor VT2 is subjected to a reverse voltage, that is, when the first thyristor VT1 is subjected to a forward voltage, the first resistor R11 always shares this forward voltage, and correspondingly, the first capacitor C11 always has voltage, thus supplying power to the signal generation circuit 12113. In addition, when the voltage across the first capacitor C11 increases, the first thyristor VT1 will turn on momentarily, and the voltage across the first capacitor C11 will stop increasing. Therefore, no additional overvoltage protection circuit is needed across the first capacitor C11. Correspondingly, the driving circuit 1212 also includes a first capacitor C12, which is connected in parallel with a first resistor R12 to supply power to the signal generation circuit 12123.
[0064] Optional, such as Figure 9 As shown, the drive circuit 1211 also includes a first capacitor C11 and a third resistor R31. The third resistor R31 is connected in series between the anode and cathode of the first thyristor VT1, and is also connected between the first resistor R11 and the second resistor R21. The first capacitor C11 is connected in parallel with the series-connected first resistor R11 and third resistor R31 to supply power to the signal generation circuit 12113. Specifically, when the second thyristor VT2 experiences a reverse voltage, that is, when the first thyristor VT1 experiences a forward voltage, the first resistor R11 and the third resistor R31 always share the forward voltage. Correspondingly, the first capacitor C11 always has a voltage, thus supplying power to the signal generation circuit 12113. Furthermore, when the voltage across the first capacitor C11 increases, the first thyristor VT1 will momentarily turn on, and the voltage across the first capacitor C11 will stop increasing. Therefore, no additional overvoltage protection circuit is needed across the first capacitor C11. Correspondingly, the drive circuit 1212 also includes a first capacitor C12 and a third resistor R32. A third resistor R32 is also connected in series between the anode and cathode of the second thyristor VT2, and the third resistor R32 is connected between the first resistor R12 and the second resistor R22. The first capacitor C12 is connected in parallel with the series-connected first resistor R12 and third resistor R32 to supply power to the signal generation circuit 12123.
[0065] It is understandable that when the first capacitor in the driving circuit is connected in parallel with the first and third resistors in series, the voltage of the first capacitor is the sum of the voltage across the first resistor and the voltage across the third resistor. The voltage range of the first capacitor is larger, that is, it can provide a wider power supply range for the signal generation circuit and has higher flexibility.
[0066] Considering that when a thyristor is subjected to reverse voltage, the overvoltage protection device in the corresponding drive circuit may be overloaded and break down due to excessive reverse voltage, a fourth resistor is connected in series between the anode and cathode of the corresponding thyristor in the drive circuit. By setting the resistance of the fourth resistor to be greater than that of the second resistor, reverse breakdown of the overvoltage protection device is prevented. This scheme to prevent reverse breakdown of the overvoltage protection device is applicable to… Figure 5 , Figure 6 , Figure 8 and Figure 9 The uninterruptible power supply 1 shown below will be referred to as [missing information] for ease of explanation. Figure 9 For example, combined with Figure 10 Let me introduce it.
[0067] like Figure 10 As shown, the drive circuit 1211 also includes a fourth resistor R41. A fourth resistor R41 is connected in series between the anode and cathode of the first thyristor VT1. Furthermore, the fourth resistor R41 is connected to the second resistor R21, and the resistance of the fourth resistor R41 is greater than the resistance of the second resistor R21. It should be noted that... Figure 10 Taking the fourth resistor R41 located to the right of the second resistor R21 as an example, the fourth resistor R41 can also be located to the left of the second resistor R21. Specifically, the fourth resistor R41 is connected between the anode of the first thyristor VT1 and the connection point between the second resistor R21 and the overvoltage protection device 12111.
[0068] It is understandable that when the first thyristor VT1 is subjected to reverse voltage, the second resistor R21, the fourth resistor R41, and the third resistor R31 are connected in series to divide the voltage. Since the resistance of the fourth resistor R41 is greater than that of the second resistor R21, most of the reverse voltage across the second resistor R21 and the fourth resistor R41 is borne by the fourth resistor R41, while the second resistor R21 only bears a small portion of the reverse voltage. Correspondingly, this reduces the voltage across the overvoltage protection device 12111, thereby preventing the overvoltage protection device 12111 from being reverse-biased and broken down. Based on this, it can be concluded that the larger the resistance of the fourth resistor R41, the better the effect of preventing the overvoltage protection device 12111 from being reverse-biased and broken down.
[0069] Similarly, the drive circuit 1212 also includes a fourth resistor R42. A fourth resistor R42 is connected in series between the anode and cathode of the second thyristor VT2, and it is connected to the second resistor R22. The resistance of the fourth resistor R42 is greater than that of the second resistor R22. When the second thyristor VT2 is subjected to a reverse voltage, most of the reverse voltage across the second resistor R22 and the fourth resistor R42 is borne by the fourth resistor R42, while only a small portion of the reverse voltage is borne by the second resistor R22. Correspondingly, the voltage across the overvoltage protection device 12121 is relatively small, thus preventing the overvoltage protection device 12121 from being reverse-biased and broken down.
[0070] Optionally, the drive circuit 1211 further includes a second diode D21, which is connected in parallel with a fourth resistor R41. This second diode D21 is used to turn on the first thyristor VT1 when the difference between its anode and cathode voltages exceeds a second voltage threshold. The second voltage threshold is the diode's turn-on voltage threshold. Specifically, when the first thyristor VT1 is subjected to a forward voltage, and the difference between its anode and cathode voltages exceeds the second voltage threshold, the second diode D21 turns on. This shorts the fourth resistor R41, and the second resistor R21, the third resistor R31, and the first resistor R11 are connected in series to divide the voltage, resulting in the same voltage division as when the fourth resistor R41 is not present in the drive circuit 1211. In short, by adding the second diode D21 in parallel with the fourth resistor R41, the fourth resistor R41, which prevents reverse breakdown when the first thyristor VT1 is subjected to a forward voltage, does not affect the normal operation of the drive circuit 1211. In other words, the fourth resistor R41 has no effect when the first thyristor VT1 is subjected to a forward voltage, and only has an effect when the first thyristor VT1 is subjected to a reverse voltage.
[0071] Similarly, the drive circuit 1212 also includes a second diode D22, which is connected in parallel with the fourth resistor R42. This second diode D22 is used to turn on the second thyristor VT2 when the difference between the anode voltage and cathode voltage is greater than the second voltage threshold. This ensures that the fourth resistor R42, which prevents reverse breakdown when the second thyristor VT2 is subjected to a forward voltage, does not affect the normal operation of the drive circuit 1212.
[0072] Optionally, the drive circuit 1211 further includes a fifth resistor R51, which is connected in series between the anode and cathode of the first thyristor VT1. The fifth resistor R51 is used to prevent overcurrent between the anode and cathode of the first thyristor VT1. Similarly, the drive circuit 1212 also includes a fifth resistor R52, which is connected in series between the anode and cathode of the second thyristor VT2. The fifth resistor R52 is used to prevent overcurrent between the anode and cathode of the second thyristor VT2.
[0073] It should be noted that the above description is based on the example of one switching unit in the main circuit 12. In fact, this application does not limit the number of switching units in the main circuit 12. When there are multiple switching units in the main circuit 12, such as... Figure 11 As shown, the main circuit switching circuit 12 includes switching units 121, 122, ..., 12n, which are connected in series between the AC input and AC output terminals of the uninterruptible power supply 1. Here, n is an integer greater than 1. For the internal structure of switching units 122 to 12n, please refer to the description of the corresponding part of switching unit 121. For the internal structure, connection relationship, and working principle of drive circuits 1221, ..., and drive circuit 12n1, please refer to the description of the corresponding part of drive circuit 1211. For the internal structure, connection relationship, and working principle of drive circuits 1222, ..., and drive circuit 12n2, please refer to the description of the corresponding part of drive circuit 1212.
[0074] Furthermore, when a differential-mode lightning strike occurs in the uninterruptible power supply 1, the existing technology, using a standard surge arrester, increases the number of first thyristors connected in series with the first thyristor VT1, and increases the number of second thyristors connected in series with the second thyristor VT2, to prevent the thyristors from being broken down by high voltage through series voltage division. However, this method requires a large number of thyristors connected in series, resulting in high circuit cost. The uninterruptible power supply 1 provided in this application, compared to the existing technology of increasing the number of thyristors connected in series, can reduce the number of thyristors connected in series while using a standard surge arrester, thus achieving high voltage protection for the thyristors. The following is a simple example illustrating this using a three-phase uninterruptible power supply 1.
[0075] like Figure 12 As shown, uninterruptible power supply 1 is a three-phase uninterruptible power supply, and the main circuit switch circuit 12 mentioned above corresponds to... Figure 12The diagram shows main circuit switch circuits 12a, 12b, and 12c. The AC input terminals of the uninterruptible power supply 1 include phase A, phase B, and phase C AC input terminals, and the AC output terminals include phase A, phase B, and phase C AC output terminals. Main circuit switch circuit 12a is connected between the phase A AC input terminal and the phase A AC output terminal of the uninterruptible power supply 1; main circuit switch circuit 12b is connected between the phase B AC input terminal and the phase B AC output terminal of the uninterruptible power supply 1; and main circuit switch circuit 12c is connected between the phase C AC input terminal and the phase C AC output terminal of the uninterruptible power supply 1. Each of the main circuit switch circuits 12a to 12c includes two switching units connected in series, and each switching unit includes a first thyristor VT1 and a second thyristor VT2 connected in anti-parallel. Furthermore, the uninterruptible power supply 1 also includes a drive circuit corresponding to each first thyristor VT1 and a drive circuit corresponding to each second thyristor VT2. Here, for a description of the drive circuit corresponding to any first thyristor VT1, please refer to the description of the corresponding part of drive circuit 1211 in the above embodiment; for a description of the drive circuit corresponding to any second thyristor VT2, please refer to the description of the corresponding part of drive circuit 1212 in the above embodiment. Furthermore, the uninterruptible power supply 1 also includes a surge protection circuit 14, which includes protection units 141 to 143. Protection unit 141 is connected between the A-phase AC input terminal and the B-phase AC input terminal of the uninterruptible power supply 1, protection unit 142 is connected between the B-phase AC input terminal and the C-phase AC input terminal of the uninterruptible power supply 1, and protection unit 143 is connected between the A-phase AC input terminal and the C-phase AC input terminal of the uninterruptible power supply 1. The surge protection circuit 14 can be any circuit that implements differential mode lightning strike protection; for example, the surge protection circuit 14 is a standard surge arrester.
[0076] For example, in one implementation scenario, under normal AC grid conditions, the A-phase and B-phase AC power outputs from the AC grid are in the positive half-cycle, and the C-phase AC power is in the negative half-cycle. Controller 13 controls all first thyristors VT1 in the main circuit switching circuits 12a to 12b to turn on and all second thyristors VT2 to turn off, and controls all first thyristors VT1 in the main circuit switching circuit 12c to turn off and all second thyristors VT2 to turn on, thereby supplying power to the AC load. At this time, if there is a differential-mode lightning strike between phases A and B of the AC grid, such as... Figure 13 As shown in (a), the residual voltage V of the lightning strike on the lightning protection circuit 14 is... L This will cause the current I on the first thyristor VT1 in the main circuit switching circuit 12a to be... VT1 The voltage rapidly decreases to 0. Afterward, the first thyristor VT1 in the main circuit 12a experiences a reverse voltage V1, the magnitude of which is almost equal to the residual voltage V1 from the lightning strike. L .
[0077] In this application, the first switching transistor of the drive circuit is in the off state when the first thyristor VT1 or the second thyristor VT2 is turned on. Therefore, the drive circuit in the uninterruptible power supply 1 is always in an effective state and can automatically drive its corresponding thyristor to turn on. Specifically, if there is a differential-mode lightning strike between phase A and phase B of the AC power grid, and the first thyristor VT1 in the main switch circuit 12a is subjected to reverse high voltage (i.e., residual lightning voltage), then the drive circuits 12a12 and 12a22 automatically drive their respective corresponding second thyristors VT2 to turn on, so as to discharge the reverse high voltage borne by the first thyristor VT1 in the main switch circuit 12a, thereby achieving high voltage protection for the first thyristor VT1 in the main switch circuit 12a. Simply put, under normal AC power grid conditions, the uninterruptible power supply 1 provided in this application can, during a differential-mode lightning strike between phase A and phase B of the AC power grid, ensure that the reverse voltage V1 borne by the first thyristor VT1 in the main switch circuit 12 is as follows: Figure 13 As shown in (b), it is zero.
[0078] In another implementation scenario, under abnormal AC power grid conditions, controller 13 controls all first thyristors VT1 and second thyristors VT2 in the main circuit switching circuits 12a to 12c to be turned off. Since the first switching transistors in the drive circuit of this application are all in a conducting state when the first thyristors VT1 and second thyristors VT2 are turned off, the drive circuits in the uninterruptible power supply 1 are all in an invalid state and cannot drive their corresponding thyristors to conduct. At this time, if there is a differential-mode lightning strike between phase A and phase B of the AC power grid, the thyristors in the main circuit switching circuits 12a and 12b, along with the lightning protection circuit 14, jointly bear the residual voltage of the lightning strike, thereby achieving high-voltage protection for the thyristors in the main circuit switching circuits 12a and 12b.
[0079] In summary, the uninterruptible power supply 1 in this application can achieve high-voltage protection for thyristors in the event of a differential-mode lightning strike, regardless of whether the AC power grid is normal or abnormal, thereby reducing circuit costs.
[0080] In this application, the uninterruptible power supply 1 can, when the thyristor is off, control the first switch in the drive circuit corresponding to the thyristor to turn on, so that there is no voltage between the gate and cathode of the thyristor, and the thyristor will never meet the conduction condition (2), that is, the drive circuit corresponding to the thyristor is in a disabled state, thereby avoiding the situation where the thyristor is accidentally triggered to turn on when it is off. In addition, when one of the first thyristors VT1 and the second thyristor VT2 is on, the uninterruptible power supply 1 can control the first switch in the drive circuit corresponding to the thyristor to turn off, so that the drive circuit corresponding to the thyristor is in an effective state, and when the reverse voltage of the other thyristor of the first thyristor VT1 and the second thyristor VT2 is too high, the drive circuit corresponding to the thyristor can automatically drive the thyristor to turn on, so as to realize high voltage protection for the other thyristor.
[0081] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. An uninterruptible power supply, characterized in that, The uninterruptible power supply (UPS) has a DC input terminal for connecting to a DC source, an AC input terminal for connecting to an AC power grid, and an AC output terminal for connecting to an AC load. The UPS includes a DC / AC conversion circuit, a main circuit switching circuit, and a controller. The DC / AC conversion circuit is connected between the DC input terminal and the AC output terminal, and is used to convert the DC power from the DC source into AC power and output it to the AC load in the event of an AC power grid anomaly. The main circuit switch is connected between the AC input terminal and the AC output terminal, and is used to transmit the electrical energy of the AC power grid to the AC load when the AC power grid is normal. The main circuit switch includes a switch unit, which includes a first thyristor and a second thyristor connected in reverse parallel. The uninterruptible power supply further includes a driving circuit, which is used to drive the first thyristor to turn on or off. The driving circuit includes a first diode, a first resistor and a first switching transistor. The cathode of the first diode is connected to the gate of the first thyristor. The first resistor is connected between the anode of the first diode and the cathode of the first thyristor. The first switching transistor is connected in parallel with the first resistor. The controller is used to control the first switching transistor to turn on when both the first thyristor and the second thyristor are turned off.
2. The uninterruptible power supply according to claim 1, characterized in that, The controller is also configured to control both the first thyristor and the second thyristor to turn off in the event of an anomaly in the AC power grid.
3. The uninterruptible power supply according to claim 1 or 2, characterized in that, The driving circuit further includes a second resistor and an overvoltage protection device. The second resistor is connected in series with the first resistor between the anode and cathode of the first thyristor. The overvoltage protection device is connected in parallel with the second resistor and is used to be in the conducting state when the voltage across the second resistor is greater than a first voltage threshold. The controller is further configured to control the first switching transistor to turn off when the first thyristor or the second thyristor is turned on.
4. The uninterruptible power supply according to claim 3, characterized in that, The controller is also used to control the first thyristor or the second thyristor to conduct when the AC power grid is normal.
5. The uninterruptible power supply according to claim 3 or 4, characterized in that, The overvoltage protection device includes a breakdown diode or a transient voltage suppression diode.
6. The uninterruptible power supply according to claim 3, characterized in that, The controller is also configured to generate a drive signal for the first thyristor and a drive signal for the second thyristor; The driving circuit further includes a signal generation circuit for generating a driving signal for the first switching transistor based on the driving signal of the first thyristor and the driving signal of the second thyristor, specifically including: When both the first thyristor and the second thyristor are turned off, the drive signals for the first thyristor and the second thyristor are both first-level signals, and the drive signal for the first switch is a second-level signal, which is opposite to the first-level signal; when the drive signal for the first switch is the second-level signal, the first switch is in the on state. When the first thyristor is turned on and the second thyristor is turned off, the driving signal for the first thyristor is the second level signal, the driving signal for the second thyristor is the first level signal, and the driving signal for the first switching transistor is the first level signal.
7. The uninterruptible power supply according to claim 6, characterized in that, The driving circuit further includes a first capacitor, which is connected in parallel with the first resistor to supply power to the signal generation circuit.
8. The uninterruptible power supply according to claim 6, characterized in that, The driving circuit further includes a first capacitor and a third resistor, wherein: The third resistor is connected in series between the anode and cathode of the first thyristor and is connected between the first resistor and the second resistor; The first capacitor is connected in parallel with the first resistor and the third resistor, which are connected in series, to supply power to the signal generation circuit.
9. The uninterruptible power supply according to any one of claims 3-8, characterized in that, The driving circuit further includes a fourth resistor, which is connected in series between the anode and cathode of the first thyristor, and the fourth resistor is connected to the second resistor, with the resistance value of the fourth resistor being greater than that of the second resistor.
10. The uninterruptible power supply according to claim 9, characterized in that, The driving circuit further includes a second diode, which is connected in parallel with the fourth resistor and is used to be in a conducting state when the difference between the anode voltage and the cathode voltage of the first thyristor is greater than a second voltage threshold.
11. The uninterruptible power supply according to any one of claims 1-10, characterized in that, The driving circuit also includes a voltage regulator, which is connected between the anode of the first diode and the connection between the first resistor and the first switching transistor, and is used to be in a conducting state when the voltage across the first resistor is greater than a third voltage threshold.
12. The uninterruptible power supply according to claim 11, characterized in that, The voltage regulator device includes a Zener diode.