Uninterruptible power supply and method of controlling the same

Abstract

An uninterruptible power supply and a control method thereof, the uninterruptible power supply comprising: an input configured to be electrically connectable to an alternating current power source; an output configured to be electrically connectable to a load; a three-bridge circuit electrically connected between the input and the output, configured to provide a rectified inverter output from the input to the output; and a controller configured to: compare a first alternating current voltage received by the input to a second alternating current voltage output by the output; compare the first alternating current voltage to a first voltage threshold when the first alternating current voltage and the second alternating current voltage reverse; and execute a reverse control logic to the three-bridge circuit when the first alternating current voltage is greater than the first voltage threshold.

Description

Technical Field

[0001] This invention relates to the field of power supply, and more specifically to an uninterruptible power supply. Background Technology

[0002] The statements in this section are merely to provide background information in relation to the present invention to aid in understanding the invention, and such background information does not necessarily constitute prior art.

[0003] An Uninterruptible Power Supply (UPS) is a regulated AC power supply that includes an energy storage device (such as a battery). It primarily consists of components such as a rectifier, inverter, and energy storage device. Its core function is to provide uninterrupted power to computer and communication network systems, including computers, servers, storage devices, and network equipment, as well as industrial control systems and industrial equipment requiring continuous operation. When the mains power is normal, the UPS regulates the mains voltage before supplying power to the load, simultaneously charging the energy storage device. If the mains power is interrupted, the UPS quickly switches to the energy storage device, continuously supplying AC power to the load, ensuring that the load continues to operate normally during the power outage, thus effectively preventing data loss or equipment damage due to power interruption.

[0004] With the continuous development of power electronics technology, the circuit topology of UPS has undergone various evolutions, among which the three-arm circuit topology has attracted much attention due to its unique structure. Compared with the traditional dual-bus circuit topology, the three-arm circuit topology has significant advantages in terms of component quantity and cost. Traditional dual-bus circuit topologies typically require more switching devices and bus capacitors, which not only increases system complexity but also raises costs. In contrast, the three-arm circuit topology significantly reduces the number of bus capacitors and switching devices by reusing some arms, lowering system costs and improving component utilization. Furthermore, the voltage across each arm of the three-arm circuit topology is only half that of the DC-side input voltage, a characteristic that gives it a significant advantage in terms of switching losses. This low switching loss characteristic not only improves system efficiency but also enables the three-arm circuit topology to operate at higher frequencies, achieving high-frequency operation and high speed.

[0005] However, current UPS systems with a three-arm circuit topology still have some limitations and need to be improved. Summary of the Invention

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide an uninterruptible power supply and its control method.

[0007] According to one aspect of the embodiments of this application, an uninterruptible power supply is provided, comprising:

[0008] The input terminal is configured to be electrically connected to an AC power source.

[0009] The output terminal is configured to be electrically connected to the load.

[0010] A three-arm bridge circuit electrically connected between the input and the output is configured to provide a rectified and inverted output from the input to the output.

[0011] The controller is configured to:

[0012] Compare the first AC voltage received at the input terminal with the second AC voltage output at the output terminal;

[0013] When the first AC voltage and the second AC voltage are reversed, the first AC voltage is compared with a first voltage threshold; wherein, the reverse includes the first AC voltage being greater than zero and the second AC voltage being less than zero, or the first AC voltage being less than zero and the second AC voltage being greater than zero;

[0014] When the first AC voltage is greater than the first voltage threshold, reverse control logic is executed on the three-bridge arm circuit.

[0015] According to the uninterruptible power supply of the present invention, the controller is further configured to:

[0016] Determine the start time of the reversal when the first AC voltage and the second AC voltage reverse.

[0017] Determine whether the second AC voltage has passed through zero at the start of the reverse. If so, execute the reverse control logic on the three-bridge circuit when the first AC voltage is greater than the first voltage threshold and the phase of the second AC voltage is greater than the first phase threshold.

[0018] According to the uninterruptible power supply of the present invention, when the first AC voltage and the second AC voltage recover to both positive voltages or both negative voltages, the execution of the reverse control logic is terminated.

[0019] According to the uninterruptible power supply of the present invention, the three-bridge-arm circuit includes a rectifier bridge arm, a common bridge arm, and an inverter bridge arm; the rectifier bridge arm has a first switching module on the high side and a second switching module on the low side; the common bridge arm has a third switching module on the high side and a fourth switching module on the low side; the inverter bridge arm has a fifth switching module on the high side and a sixth switching module on the low side.

[0020] According to the uninterruptible power supply of the present invention, wherein the reverse control logic includes:

[0021] Control the controllable switch in the first switch module and the controllable switch in the second switch module to turn off;

[0022] Simultaneously, a first pulse width modulation signal and a second pulse width modulation signal with a first frequency are sent to the control terminals of the controllable switches in the third switch module and the fourth switch module, respectively, wherein the first pulse width modulation signal and the second pulse width modulation signal are complementary and the first frequency is greater than the frequency of the AC power supply; and

[0023] When the second AC voltage is greater than zero, the controllable switch in the fifth switch module is turned on and the controllable switch in the sixth switch module is turned off; when the second AC voltage is less than zero, the controllable switch in the fifth switch module is turned off and the controllable switch in the sixth switch module is turned on.

[0024] According to the uninterruptible power supply of the present invention, wherein the reverse control logic includes:

[0025] When the first AC voltage is greater than zero, a third pulse width modulation signal with a second frequency is sent to the control terminal of the controllable switch in the first switch module, and the controllable switch in the second switch module is turned off; when the first AC voltage is less than zero, the controllable switch in the first switch module is turned off and a fourth pulse width modulation signal with a second frequency is output to the control terminal of the controllable switch in the second switch module, wherein the second frequency is greater than the frequency of the AC power supply.

[0026] Simultaneously, the third pulse width modulation signal and the fourth pulse width modulation signal are output to the control terminals of the controllable switches in the third switch module and the fourth switch module, respectively, wherein the third pulse width modulation signal and the fourth pulse width modulation signal are complementary; and

[0027] When the second AC voltage is greater than zero, the controllable switch in the fifth switch module is turned on and the controllable switch in the sixth switch module is turned off; when the second AC voltage is less than zero, the controllable switch in the fifth switch module is turned off and the controllable switch in the sixth switch module is turned on.

[0028] According to the uninterruptible power supply of the present invention, the AC power source is mains power, and the first voltage threshold is determined based on the effective value of the first AC voltage.

[0029] According to the uninterruptible power supply of the present invention, the first phase threshold is between 8 and 10 degrees. According to another aspect of the embodiments of this application, a control method for an uninterruptible power supply is also provided, wherein the uninterruptible power supply has a three-arm bridge circuit, and the control method includes:

[0030] Compare the first AC voltage received at the input terminal of the uninterruptible power supply with the second AC voltage output at the output terminal of the uninterruptible power supply;

[0031] When the first AC voltage and the second AC voltage are reversed, the first AC voltage is compared with a first voltage threshold; wherein, the reverse includes the first AC voltage being greater than zero and the second AC voltage being less than zero, or the first AC voltage being less than zero and the second AC voltage being greater than zero;

[0032] When the first AC voltage is greater than the first voltage threshold, reverse control logic is executed on the three-bridge-arm circuit. According to the control method of the present invention, the method further includes: determining the start time of the reverse inversion between the first AC voltage and the second AC voltage;

[0033] Determine whether the second AC voltage has passed through zero at the start of the reverse. If so, execute the reverse control logic on the three-bridge circuit when the first AC voltage is greater than the first voltage threshold and the phase of the second AC voltage is greater than the first phase threshold.

[0034] This invention provides an uninterruptible power supply (UPS) and its control method. By introducing a tolerance judgment mechanism, the UPS only activates its response mechanism and enters reverse control when a reverse event exceeds a strictly set threshold condition, thus effectively avoiding overreaction to minor or transient reverse events. This innovative design significantly reduces unnecessary reverse control intervention, substantially lowers switching losses and noise, and effectively extends the service life of the equipment. Furthermore, it significantly enhances the adaptability and reliability of the UPS under complex power grid conditions, enabling it to operate stably under various harsh operating conditions and providing strong support for the safe and reliable operation of the power system. Attached Figure Description

[0035] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0036] Figure 1 A schematic diagram of the circuit structure of an uninterruptible power supply according to an embodiment of the present invention is shown;

[0037] Figure 2 The diagram shows control waveforms of multiple controllable switches in an uninterruptible power supply according to an embodiment of the present invention.

[0038] Figure 3A control waveform diagram of a plurality of controllable switches of an uninterruptible power supply according to another embodiment of the present invention is shown.

[0039] Figure 4 The diagram shows the waveforms of the input AC voltage and output AC voltage of the uninterruptible power supply according to an embodiment of the present invention at the initial moment of the reverse event, when the inverter just enters the zero-crossing point.

[0040] Figure 5 A flowchart of a control method for an uninterruptible power supply according to an embodiment of the present invention is shown. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0042] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0043] The block diagrams shown in the attached figures are merely functional entities and do not necessarily correspond to physically independent entities. These functional entities can be implemented in software, within one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0044] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0045] Figure 1 A schematic diagram of the circuit structure of an uninterruptible power supply according to an embodiment of the present invention is shown. Figure 1As shown, UPS10 is an uninterruptible power supply with a three-arm circuit. Typically, the three-arm circuit includes a rectifier arm, a common arm, and an inverter arm. Under normal AC input power (e.g., mains power), UPS10 uses high-frequency (e.g., 60-100kHz) pulse width modulation signals to control the switching transistors in the two switching modules on the rectifier arm; simultaneously, it uses complementary mains frequency (e.g., 50Hz) pulse width modulation signals to control the switching transistors in the two switching modules on the middle common arm; and it uses two high-frequency complementary pulse width modulation signals to control the switching transistors in the two switching modules on the inverter arm, thereby converting the AC mains input into DC and then inverting it back into AC to supply the load.

[0046] However, the output frequency of the AC input power supply often fluctuates due to various interference factors (such as transmission line faults, load changes, etc.), and these fluctuations may cause the input AC voltage and output AC voltage of the uninterruptible power supply to reverse. In this article, "reverse" refers to the uninterruptible power supply's input AC voltage and output AC voltage being reversed, which includes two situations: the input AC voltage is greater than zero and the output AC voltage is less than zero; and the input AC voltage is less than zero and the output AC voltage is greater than zero. In this case, if the power frequency complementary pulse width modulation signal continues to be used to control the switching transistors in the two switching modules on the middle common bridge arm, the current in the rectifier-side inductor (also known as the input inductor) L1 will continue to increase in one direction, leading to adverse consequences. Specifically, for example, when both the input AC voltage and the output AC voltage are greater than 0, the switching transistors in the two switching modules Q1 and Q2 on the rectifier bridge arm are both turned on or off at high frequency, while the switching transistor in the switching module Q4 on the lower side of the common bridge arm is continuously turned on (e.g., for 10ms). If the mains power output frequency suddenly changes, causing the input AC voltage of UPS 10 to suddenly be less than 0, the input AC voltage, which is opposite to the output AC voltage, will continuously charge the input inductor L1 through the switching transistor in switching module Q4 and the diode in switching module Q2, causing the current in the input inductor L1 to increase continuously in one direction, thereby damaging the rectifier.

[0047] Therefore, when the input AC voltage and output AC voltage of an uninterruptible power supply (UPS) are reversed, existing UPS control methods implement reverse control on the three-arm circuit to avoid adverse effects such as damage to rectifier devices caused by continuously increasing current in one direction. Reverse control precisely controls the on and off timing of the high-side and low-side switches in each arm of the three-arm circuit, thereby suppressing the continuous increase of reverse current in the rectifier circuit, ensuring stable circuit operation, and maintaining stable bus voltage.

[0048] However, in practical applications, the frequency of the AC input power supply may fluctuate frequently, causing the uninterruptible power supply (UPS) to frequently engage in reverse control. Through long-term practice and in-depth research, the inventors discovered that not every reversal results in a large inrush current that immediately leads to serious adverse consequences. On the contrary, blindly responding to every reversal without discrimination can cause the UPS to frequently interrupt its normal operation and enter reverse control mode. This unnecessary and frequent intervention not only significantly increases the switching losses and noise level of the UPS but also negatively impacts its efficiency, and in extreme cases, may even cause the equipment to malfunction.

[0049] To overcome the limitations of the uninterruptible power supply with a three-bridge-arm circuit, the present invention provides an improved uninterruptible power supply and its control method.

[0050] like Figure 1 As shown, the uninterruptible power supply UPS 10 includes: an input terminal IN, an output terminal OUT, an input inductor L1, a three-arm circuit 100, and a controller 103. The input terminal IN is electrically connected to an AC power source 11 (e.g., mains power), the output terminal OUT is electrically connected to a load 12, the three-arm circuit 100 is electrically connected between the input terminal IN and the output terminal OUT, and the input inductor L1 is electrically connected between the input terminal IN and the three-arm circuit 100.

[0051] The three-arm circuit 100 is configured to provide rectified and inverted output from input IN to output OUT to supply power to load 12. The three-arm circuit 100 may include a rectifier bridge arm having a first switching module Q1 on the high side and a second switching module Q2 on the low side, a common bridge arm having a third switching module Q3 on the high side and a fourth switching module Q4 on the low side, and an inverter bridge arm having a fifth switching module Q5 on the high side and a sixth switching module Q6 on the low side. Furthermore, the three-arm circuit 100 may also include a bus capacitor C1, an inverter-side inductor L2, and a filter capacitor C2.

[0052] In an embodiment of the invention, the rectifier bridge arm is configured to convert AC power supplied by AC power source 11 into DC power, the common bridge arm is configured to regulate and control power transmission, and the inverter bridge arm is configured to invert DC power into AC power to supply the load 12. The controller 103 is configured to control the UPS 10. Specifically, the controller 103 is configured to: compare a first AC voltage Uin received at input terminal IN with a second AC voltage Uout output at output terminal OUT; when the first AC voltage Uin and the second AC voltage Uout are reversed, compare the first AC voltage Uin with a first voltage threshold; wherein, the reverse includes the first AC voltage Uin being greater than zero and the second AC voltage Uout being less than zero, or the first AC voltage Uin being less than zero and the second AC voltage Uout being greater than zero; and when the first AC voltage Uin is greater than the first voltage threshold, execute reverse control logic on the three-arm circuit 100.

[0053] In some embodiments of the present invention, the controller 103 is further configured to exit the execution of the reverse control logic when the first AC voltage Uin and the second AC voltage Uout return to both positive voltages or both negative voltages, or when the reverse control logic has been continuously executed for a specified time (e.g., 10ms).

[0054] In some embodiments of the present invention, each of the switching modules Q1-Q6 may include a controllable switch and a diode connected in reverse parallel with the controllable switch. For example, the first switching module Q1 includes a first controllable switch S1 and a first diode D1, and so on.

[0055] In some embodiments of the present invention, the controllable switches included in the switching modules Q1-Q6 can be semiconductor switching transistors, such as MOSFETs, IGBTs, etc.

[0056] In an embodiment of the present invention, the UPS 10 further includes a bypass branch 101 from the input terminal IN to the output terminal OUT.

[0057] Figure 2 The diagram shows control waveforms of multiple controllable switches in an uninterruptible power supply (UPS) according to an embodiment of the present invention. The UPS 10 is in operation. Figure 2As shown, at time t1-t2, the first AC voltage Uin is in the positive half-cycle. The controller 103 controls the first controllable switch S1 in the first switch module Q1 to remain off, and uses a high-frequency pulse width modulation signal to control the second controllable switch S2 in the second switch module Q2 to turn on / off. At the same time, it controls the third controllable switch S3 in the third switch module Q3 to remain off and controls the fourth controllable switch S4 in the fourth switch module Q4 to remain on. It also uses two high-frequency complementary pulse width modulation signals to control the fifth controllable switch S5 in the fifth switch module Q5 and the sixth controllable switch S6 in the sixth switch module Q6 to turn on / off, respectively. When the second controllable switch S2 is turned on, the current output from the AC power supply 11 flows from the input terminal IN through the input inductor L1 into the three-bridge circuit 100, and then through the second controllable switch S2 into the fourth controllable switch S4 to form a loop, charging the input inductor L1. When the second controllable switch S2 is turned off, the input inductor L1 discharges, and the discharge current flows through the first diode D1 into the bus capacitor C1, and then into the fourth controllable switch S4 to form a loop, charging the bus capacitor C1. Simultaneously, the fifth controllable switch S5 and the sixth controllable switch S6 alternately turn on, inverting the DC power supplied by the bus capacitor C1 into AC power and outputting it to the load 12. During times t1-t2, both the first AC voltage Uin and the second AC voltage Uout are in the positive half-cycle.

[0058] like Figure 2 As shown, during time t3-t4, the first AC voltage Uin is in the negative half-cycle. The controller 103 uses a high-frequency pulse width modulation signal to control the first controllable switch S1 to turn on / off, and controls the second controllable switch S2 in the second switch module Q2 to remain off; at the same time, it controls the third controllable switch S3 in the third switch module Q3 to continue to turn on and controls the fourth controllable switch S4 in the fourth switch module Q4 to remain off; and it uses two high-frequency complementary pulse width modulation signals to control the fifth controllable switch S5 in the fifth switch module Q5 and the sixth controllable switch S6 in the sixth switch module Q6 to turn on / off respectively. When the first controllable switch S1 is turned on, the current output from the AC power supply 11 flows from the input terminal IN through the input inductor L1 into the three-bridge circuit 100, and then through the first controllable switch S1 into the third controllable switch S3 to form a loop, charging the input inductor L1. When the first controllable switch S1 is turned off, the input inductor L1 discharges, and the discharge current flows through the second diode D2 into the bus capacitor C1, and then into the third controllable switch S3 to form a loop, charging the bus capacitor C1. Simultaneously, the fifth controllable switch S5 and the sixth controllable switch S6 alternately turn on, inverting the DC power supplied by the bus capacitor C1 into AC power and outputting it to the load 12. During times t3-t4, both the first AC voltage Uin and the second AC voltage Uout are in the negative half-cycle.

[0059] Figure 3 A control waveform diagram of multiple controllable switches of an uninterruptible power supply according to another embodiment of the present invention is shown. The UPS 10 is in operation, and the controller 103 compares a first AC voltage Uin received at input terminal IN with a second AC voltage Uout output at output terminal OUT. Figure 3 As shown, at time t0, due to frequency fluctuations in the AC input power supply, the first AC voltage Uin jumps from a negative voltage to a positive voltage, while the second AC voltage Uout remains negative. Controller 103 determines that the first AC voltage Uin and the second AC voltage Uout have reversed direction since time t0. Then, controller 103 compares the first AC voltage Uin with a first voltage threshold Uth. When the first AC voltage Uin is not greater than the first voltage threshold Uth, controller 103 does not execute the reverse control logic on the three-bridge arm circuit 100. Figure 3 As shown, at the moment corresponding to dashed line 1, the first AC voltage Uin is greater than the first voltage threshold Uth, and the controller 103 executes reverse control logic on the three-bridge arm circuit 100. At moment t1, the second AC voltage Uout becomes a positive voltage, and the controller 103 stops executing the reverse control logic.

[0060] like Figure 3 As shown, at time t2, the first AC voltage Uin changes from positive to negative, while the second AC voltage Uout remains positive. Controller 103 determines that the first AC voltage Uin and the second AC voltage Uout reverse direction starting from time t2. Then, controller 103 compares the first AC voltage Uin with a first voltage threshold Uth. When the first AC voltage Uin is not greater than the first voltage threshold Uth, controller 103 does not execute the reverse control logic on the three-bridge arm circuit 100. Figure 3 As shown, at time t2, the first AC voltage Uin is greater than the first voltage threshold Uth, and the controller 103 executes the reverse control logic. At time t3, the second AC voltage Uout becomes negative, and the controller 103 stops executing the reverse control logic.

[0061] In some embodiments of the present invention, during the period when the first AC voltage Uin and the second AC voltage Uout reverse and the first AC voltage Uin does not exceed the first voltage threshold Uth, the controller 103 may also be configured to control the first controllable switch S1 and the second controllable switch S2 to turn off, and keep the original control logic of other switch modules unchanged, so as to mitigate the adverse effects of the reverse event.

[0062] In some embodiments of the present invention, the AC power supply 11 is AC mains power, and the first voltage threshold Uth is determined based on the effective value of the first AC voltage Uin. Through long-term practical experience, the inventors have found that the first voltage threshold Uth is 5%-10% of the effective value of the first AC voltage Uin, preferably 10V, 12V, or 15V.

[0063] The embodiments of the present invention, by reasonably setting a first voltage threshold Uth, not only ensure that reverse events, although potentially causing some temporary adverse effects, will not disrupt the normal operation of UPS 10 within a limited time, but also allow for immediate response and intervention when a reverse event meets the threshold condition, thereby guaranteeing system stability and continuity. The optimized uninterruptible power supply effectively prevents UPS 10 from overreacting to reverse events, preventing the intervention mechanism from being triggered by false or short-lived reverse events, thus interrupting the normal operation of UPS 10. Through this optimized threshold setting, the present invention improves the system's tolerance to reverse events while also enhancing the overall reliability and operating efficiency of the system.

[0064] According to some embodiments of the present invention, the reverse control logic is configured to control a plurality of controllable switches included in the three-bridge arm circuit 100 to prevent the input inductor L1 of the uninterruptible power supply 10 from being continuously charged during the period when the first AC voltage Uin and the second AC voltage Uout are reversed, thereby suppressing the reverse surge current in the rectifier circuit from damaging the switching devices and ensuring the stability of the second AC voltage Uout.

[0065] According to some embodiments of the present invention, the reverse control logic can be configured to: control the first controllable switch S1 in the first switch module Q1 and the second controllable switch S2 in the second switch module Q2 to turn off; simultaneously, send a first pulse width modulation signal and a second pulse width modulation signal with a first frequency to the control terminal of the third controllable switch S3 in the third switch module Q3 and the control terminal of the fourth controllable switch S4 in the fourth switch module Q4, respectively, wherein the first pulse width modulation signal and the second pulse width modulation signal are complementary and the first frequency is greater than the frequency of the AC power supply 11; and when the second AC voltage Uout is greater than zero, control the fifth controllable switch S5 in the fifth switch module Q5 to turn on and control the sixth controllable switch S6 in the sixth switch module Q6 to turn off; when the second AC voltage Uout is less than zero, control the fifth controllable switch S5 in the fifth switch module Q5 to turn off and control the sixth controllable switch S6 in the sixth switch module Q6 to turn on.

[0066] According to some embodiments of the present invention, the reverse control logic can also be configured to: when the first AC voltage Uin is greater than zero, send a third pulse width modulation signal with a second frequency to the control terminal of the first controllable switch S1 in the first switch module Q1, and control the second controllable switch S2 in the second switch module Q2 to turn off; when the first AC voltage is less than zero, control the first controllable switch S1 in the first switch module Q1 to turn off and output a fourth pulse width modulation signal with a second frequency to the control terminal of the second controllable switch S2 in the second switch module Q2, wherein the second frequency is greater than the frequency of the AC power supply 11; simultaneously, send signals to the third switch... The control terminals of the third controllable switch S3 in module Q3 and the fourth controllable switch S4 in module Q4 output a third pulse width modulation signal and a fourth pulse width modulation signal, respectively, which are complementary. When the second AC voltage Uout is greater than zero, the fifth controllable switch S5 in module Q5 is turned on, and the sixth controllable switch S6 in module Q6 is turned off; when the second AC voltage Uout is less than zero, the fifth controllable switch S5 in module Q5 is turned off, and the sixth controllable switch S6 in module Q6 is turned on. By executing this reverse control logic, UPS 10 can achieve lower switching losses, thereby significantly improving the overall efficiency and reliability of the system.

[0067] The above embodiments of the present invention, by introducing a tolerance judgment mechanism and optimizing the reverse control logic, can not only effectively prevent the UPS 10 from overreacting to reverse events and prevent the uninterruptible power supply from interrupting normal operation due to frequent execution of reverse control logic, thereby significantly enhancing the stability and continuity of the system; but also reduce the switching losses caused by the execution of reverse control logic, further improving the operating efficiency of the uninterruptible power supply.

[0068] In an uninterruptible power supply (UPS) with a three-arm circuit, the common arm and the inverter arm constitute the inverter to achieve DC-to-AC conversion. Typically, to improve inverter efficiency, the H4 inverter bridge uses unipolar control, meaning the common arm acts as the power frequency arm and the inverter arm as the high-frequency arm. However, because the inverter's power frequency arm is prone to waveform distortion, oscillation, or voltage spikes near the zero-crossing point, which can adversely affect the normal operation of the load equipment, the controller 103 performs high-frequency control on the power frequency arm at the zero-crossing point to suppress distortion and oscillation, making the inverter's output waveform smoother and more stable. Therefore, during UPS operation, the initial moment of a reverse event may coincide with the moment the inverter enters the zero-crossing point. Figure 4The diagram shows the waveforms of the input AC voltage and output AC voltage of the uninterruptible power supply according to an embodiment of the present invention at the initial moment of a reverse event, when the inverter has just entered the zero-crossing point. Figure 4 As shown, at the initial moment of the reverse event—time t1—the inverter just enters the zero-crossing point (the second AC voltage Uout passes through the zero-crossing point). Therefore, this invention further optimizes the uninterruptible power supply and its controller to avoid conflicts between the reverse control logic and the high-frequency control of the zero-crossing point.

[0069] Because the controller 103 interrupts the high-frequency control of the inverter and instead executes reverse control logic, the operating condition of the uninterruptible power supply may further deteriorate, leading to a series of problems such as output AC voltage distortion. Furthermore, the high-frequency control of the inverter at the zero-crossing point by the controller 103 can mitigate the adverse effects caused by the reverse event, such as reducing the charging speed of the input inductor L1. Therefore, the controller 103 can be configured to: determine whether the second AC voltage Uout has passed through the zero-crossing point at the start of the reverse event (the initial moment of the reverse event) when the first AC voltage Uin and the second AC voltage Uout reverse; if the second AC voltage Uout has passed through the zero-crossing point at the start of the reverse event, then when the first AC voltage Uin is greater than the first voltage threshold Uth, compare the phase of the second AC voltage Uout with the first phase threshold Rth1; and execute the reverse control logic when the phase of the second AC voltage Uout is greater than the first phase threshold Rth1. Specifically, the controller 103 performs zero-crossing high-frequency control of the inverter between 0 degrees and the first phase threshold Rth1. Additionally, the first AC voltage Uin may exhibit an approximately square wave waveform. These waveforms exhibit extremely steep rising and falling edges, with the voltage value rising rapidly within a very short time. In such cases, if a reversal occurs and the criterion for the uninterruptible power supply (UPS) to execute reverse control logic is solely based on whether the first AC voltage Uin is greater than the first voltage threshold Uth, these waveforms will frequently trigger the UPS to execute reverse control logic, severely impacting its normal operation. This invention, through further optimization of the UPS by adding a condition for determining the phase of the second AC voltage Uout, effectively avoids this situation. This improvement significantly enhances the stability and efficiency of the UPS, ensuring reliable operation even under complex conditions.

[0070] In at least one embodiment of the present invention, the zero-crossing high-frequency control of the inverter is specifically implemented by: employing an adaptive frequency conversion modulation strategy to increase the switching frequency of the semiconductor switching devices to a preset high-frequency value (e.g., 80 kHz) between the zero-crossing point and the first phase threshold Rth1, thereby improving the waveform quality at the zero-crossing point, reducing oscillations and distortion, and improving the quality of the inverter's output power. According to some embodiments of the present invention, the first phase threshold Rth1 is between 8 and 10 degrees. Preferably, the first phase threshold Rth1 is 9 degrees.

[0071] Embodiments of the present invention also provide a control method for an uninterruptible power supply, wherein the uninterruptible power supply has a three-arm bridge circuit 100. For example... Figure 5 As shown, the control method includes the following steps:

[0072] S100: Compare the first AC voltage Uin with the second AC voltage Uout.

[0073] S101: Determine whether the first AC voltage Uin and the second AC voltage Uout are reversed. If yes, proceed to step S102; otherwise, proceed to step S109. Reverse polarity includes the first AC voltage Uin being greater than zero and the second AC voltage Uout being less than zero, or the first AC voltage Uin being less than zero and the second AC voltage Uout being greater than zero.

[0074] S102: Determine whether the first AC voltage Uin is greater than the first voltage threshold Uth. If yes, proceed to step S103; otherwise, proceed to step S100. That is, when the first AC voltage Uin is not greater than the first voltage threshold, the uninterruptible power supply does not respond to the above reverse event; the uninterruptible power supply executes the next step only when the first AC voltage Uin is greater than the first voltage threshold Uth.

[0075] S103: Determine whether the second AC voltage Uout has passed the zero-crossing point at the initial moment of the reverse event. If yes, proceed to step S104; otherwise, proceed to step S106. Step S103 is used to determine whether the inverter in the uninterruptible power supply is being controlled at high frequency because it has just entered the zero-crossing point at the initial moment of the reverse event.

[0076] S104: Compare the phase of the second AC voltage Uout with the first phase threshold Rth1. The first phase threshold Rth1 can be determined according to the actual operating conditions.

[0077] S105: Determine whether the phase of the second AC voltage Uout is greater than the first phase threshold Rth1. If yes, proceed to step S106; otherwise, proceed to step S104.

[0078] S106: Execute reverse control logic.

[0079] S107: Compare the first AC voltage Uin with the second AC voltage Uout.

[0080] S108: Determine whether the first AC voltage Uin and the second AC voltage Uout have returned to being both positive voltages or both negative voltages. If yes, proceed to step S109; otherwise, proceed to step S106.

[0081] S109: End.

[0082] In embodiments of the present invention, the above steps can be arbitrarily combined or rearranged according to actual needs. For example, when the judgment result of step S102 is "yes", steps S103-S105 can be omitted, and step S106 can be performed directly, that is, the reverse control logic is executed.

[0083] According to embodiments of the present invention, by optimizing the uninterruptible power supply (UPS) and its controller and introducing a tolerance judgment mechanism, a precise response to reverse events is achieved. The optimized UPS only activates the response mechanism and enters reverse control when a reverse event exceeds a strictly set threshold condition, thereby effectively avoiding overreaction to minor or transient reverse events. This innovative design significantly reduces unnecessary reverse control intervention, substantially lowers switching losses and noise, and thus effectively extends the service life of the equipment. Simultaneously, it significantly enhances the adaptability and reliability of the UPS under complex power grid conditions, enabling it to operate stably under various harsh operating conditions and providing strong support for the safe and reliable operation of the power system.

[0084] In this invention, the input AC voltage, first AC voltage, output AC voltage, or second AC voltage of the uninterruptible power supply all refer to the effective value of the AC voltage. The phase of the output AC voltage and the phase of the second AC voltage Uout refer to their numerical phase values. For example, the actual phase of the second AC voltage Uout is -15 degrees, and its phase is 15 degrees.

[0085] References to "various embodiments," "some embodiments," "one embodiment," or "embodiment," etc., in this specification refer to a specific feature, structure, or property described in connection with the said embodiment, included in at least one embodiment. Therefore, the appearance of the phrases "in various embodiments," "in some embodiments," "in one embodiment," or "in an embodiment," etc., throughout this specification does not necessarily refer to the same embodiment. Furthermore, specific features, structures, or properties can be combined in any suitable manner in one or more embodiments. Therefore, a specific feature, structure, or property shown or described in connection with one embodiment can be combined, in whole or in part, with features, structures, or properties of one or more other embodiments without limitation, provided that the combination is not illogical or inoperable.

[0086] The terms "comprising," "having," and similar expressions used in this specification are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses. Furthermore, the elements in the accompanying drawings are for illustrative purposes only and are not drawn to scale.

[0087] While the present invention has been described through preferred embodiments, it is not limited to the embodiments described herein, and various changes and modifications are made without departing from the scope of the invention.

Claims

1. An uninterruptible power supply, comprising: The input terminal is configured to be electrically connected to an AC power source. The output terminal is configured to be electrically connected to the load. A three-arm bridge circuit electrically connected between the input and the output is configured to provide a rectified and inverted output from the input to the output. The controller is configured to: Compare the first AC voltage received at the input terminal with the second AC voltage output at the output terminal; When the first AC voltage and the second AC voltage are reversed, the first AC voltage is compared with a first voltage threshold; wherein, the reverse includes the first AC voltage being greater than zero and the second AC voltage being less than zero, or the first AC voltage being less than zero and the second AC voltage being greater than zero; When the first AC voltage is greater than the first voltage threshold, reverse control logic is executed on the three-bridge arm circuit.

2. The uninterruptible power supply according to claim 1, wherein, The controller is also configured to: Determine the start time of the reversal when the first AC voltage and the second AC voltage reverse. Determine whether the second AC voltage has passed through zero at the start of the reverse. If so, execute the reverse control logic on the three-bridge circuit when the first AC voltage is greater than the first voltage threshold and the phase of the second AC voltage is greater than the first phase threshold.

3. The uninterruptible power supply according to claim 1 or 2, wherein, When the first AC voltage and the second AC voltage return to being both positive or both negative, the execution of the reverse control logic is terminated.

4. The uninterruptible power supply according to claim 1 or 2, wherein, The three-bridge-arm circuit includes a rectifier bridge arm, a common bridge arm, and an inverter bridge arm; the rectifier bridge arm has a first switching module on the high side and a second switching module on the low side; the common bridge arm has a third switching module on the high side and a fourth switching module on the low side; the inverter bridge arm has a fifth switching module on the high side and a sixth switching module on the low side.

5. The uninterruptible power supply according to claim 4, wherein, The reverse control logic includes: Control the controllable switch in the first switch module and the controllable switch in the second switch module to turn off; Simultaneously, a first pulse width modulation signal and a second pulse width modulation signal with a first frequency are sent to the control terminals of the controllable switches in the third switch module and the fourth switch module, respectively, wherein the first pulse width modulation signal and the second pulse width modulation signal are complementary and the first frequency is greater than the frequency of the AC power supply; and When the second AC voltage is greater than zero, the controllable switch in the fifth switch module is turned on and the controllable switch in the sixth switch module is turned off; when the second AC voltage is less than zero, the controllable switch in the fifth switch module is turned off and the controllable switch in the sixth switch module is turned on.

6. The uninterruptible power supply according to claim 4, wherein, The reverse control logic includes: When the first AC voltage is greater than zero, a third pulse width modulation signal with a second frequency is sent to the control terminal of the controllable switch in the first switch module, and the controllable switch in the second switch module is turned off; when the first AC voltage is less than zero, the controllable switch in the first switch module is turned off and a fourth pulse width modulation signal with a second frequency is output to the control terminal of the controllable switch in the second switch module, wherein the second frequency is greater than the frequency of the AC power supply. Simultaneously, the third pulse width modulation signal and the fourth pulse width modulation signal are output to the control terminals of the controllable switches in the third switch module and the fourth switch module, respectively, wherein the third pulse width modulation signal and the fourth pulse width modulation signal are complementary; and When the second AC voltage is greater than zero, the controllable switch in the fifth switch module is turned on and the controllable switch in the sixth switch module is turned off; when the second AC voltage is less than zero, the controllable switch in the fifth switch module is turned off and the controllable switch in the sixth switch module is turned on.

7. The uninterruptible power supply according to claim 1 or 2, wherein, The AC power source is AC mains power, and the first voltage threshold is determined based on the effective value of the first AC voltage.

8. The uninterruptible power supply according to claim 2, wherein, The first phase threshold is between 8 and 10 degrees.

9. A control method for an uninterruptible power supply, wherein, The uninterruptible power supply has a three-arm bridge circuit, and the method includes: Compare the first AC voltage received at the input terminal of the uninterruptible power supply with the second AC voltage output at the output terminal of the uninterruptible power supply; When the first AC voltage and the second AC voltage are reversed, the first AC voltage is compared with a first voltage threshold; wherein, the reverse includes the first AC voltage being greater than zero and the second AC voltage being less than zero, or the first AC voltage being less than zero and the second AC voltage being greater than zero; When the first AC voltage is greater than the first voltage threshold, reverse control logic is executed on the three-bridge arm circuit.

10. The control method according to claim 9, further comprising: Determine the start time of the reversal when the first AC voltage and the second AC voltage reverse. Determine whether the second AC voltage has passed through zero at the start of the reverse. If so, execute the reverse control logic on the three-bridge circuit when the first AC voltage is greater than the first voltage threshold and the phase of the second AC voltage is greater than the first phase threshold.

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