An uninterrupted power supply switching control method and uninterrupted power supply system

Abstract

The application discloses an uninterrupted power supply switching control method and an uninterrupted power supply system, and relates to the technical field of uninterrupted power supply. In order to solve the problem that the uninterrupted power supply is prone to switching failure when switching from battery power supply to mains power supply, the application provides an uninterrupted power supply switching control method. The method is applied to an uninterrupted power supply system comprising multiple parallel modules. When switching from battery power supply to mains power supply, the switching of one-phase power supply of one module is sequentially performed until the switching of three-phase power supply of all modules is completed. When switching of any module, the output power of the current module is reduced, the output power of the remaining modules is increased, and the total output power of the system is kept unchanged. When switching of any phase, the remaining two phases of the current module are kept in power supply output and the output power is increased, and the output power of the current module is kept unchanged. Therefore, the system always has power input during the whole switching process, and the DC bus voltage is maintained. Moreover, the overload is controlled in a safe range, and reliable and uninterrupted switching is realized.

Description

Technical Field

[0001] This application relates to the field of uninterruptible power supply (UPS) technology, and in particular to a UPS switching control method and a UPS system. Background Technology

[0002] To reduce hardware costs, modular uninterruptible power supplies (UPS) typically employ a power topology that combines three-phase AC power factor correction (PFC) with three battery boost circuits. In this topology, when the AC power is normal, the three-phase PFC circuit operates in rectification mode. When the battery discharges, the same three-phase branch is reused for boosting, sending battery energy to the DC bus. When the equipment is in battery mode (e.g., during AC power failure), each phase load is powered by the corresponding battery boost branch. Once the AC power returns to normal, the equipment needs to be switched back from battery mode to AC power mode.

[0003] During the switch from battery to AC power, the entire UPS system receives no power input, but the UPS requires uninterrupted output. In this situation where input is interrupted but output still needs to be maintained, the DC bus voltage will be pulled down by the load. Since the switch takes time to complete, the DC bus voltage cannot be maintained during this downtime, making the switch prone to failure.

[0004] Therefore, those skilled in the art urgently need an uninterruptible power supply switching control method to solve the problem that current UPS systems are prone to switching failures when switching from battery to AC power. Summary of the Invention

[0005] The purpose of this application is to provide an uninterruptible power supply (UPS) switching control method and UPS system to solve the problem that current UPS systems are prone to switching failures when switching from battery to AC power.

[0006] To solve the above-mentioned technical problems, this application provides an uninterruptible power supply (UPS) switching control method, which is applied to an UPS system. The UPS system includes multiple UPS modules connected in parallel, and the UPS modules are powered by three-phase power supply through batteries or mains power. The methods include: The power supply of one phase of each uninterruptible power supply module is switched from battery power to mains power in sequence until all three phases of the uninterruptible power supply modules have been switched. When any of the uninterruptible power supply modules switches power, the output power of the current uninterruptible power supply module is reduced, the output power of the other uninterruptible power supply modules is increased, and the total output power of the uninterruptible power supply system remains unchanged. When any phase of any of the uninterruptible power supply modules switches power, the other two phases of the current uninterruptible power supply module are controlled to maintain power output and increase output power, so as to keep the output power of the current uninterruptible power supply module unchanged.

[0007] In one optional embodiment, the sequential switching of one phase of the uninterruptible power supply module from battery power to AC power includes: After completing the sequential switching of the three-phase power supply of one of the uninterruptible power supply modules, the sequential switching of the three-phase power supply of the next uninterruptible power supply module is performed.

[0008] In one optional embodiment, the sequential switching of one phase of the uninterruptible power supply module from battery power to AC power includes: After each of the uninterruptible power supply (UPS) modules that have completed the power supply of one phase has switched sequentially, the UPS modules that have completed the power supply of the next phase have switched sequentially.

[0009] In one alternative embodiment, each of the uninterruptible power supply modules includes three sub-units corresponding one-to-one with the three-phase power supply; The process of sequentially switching the power supply of one phase of each uninterruptible power supply module from battery power to AC power, until all three phases of the uninterruptible power supply modules have completed the power supply switching, includes: The power supply of each subunit is switched from battery power to AC power in sequence until all subunits have completed the power supply switch. During the power supply switching process of any of the sub-units: The output power of the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit is reduced, and the output power of the sub-units belonging to the other uninterruptible power supply modules is increased, so as to keep the total output power of the uninterruptible power supply system constant. Based on the reduced output power of the current uninterruptible power supply module, the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit are controlled to maintain power output and increase output power, so as to keep the output power of the uninterruptible power supply module unchanged.

[0010] In one alternative embodiment, controlling the current output power reduction of the uninterruptible power supply module includes: The output power of the uninterruptible power supply module is reduced according to the preset load reduction ratio. The load reduction ratio is determined based on the parameters of the uninterruptible power supply system, and the target condition is to minimize the maximum value between the overload ratio of the current uninterruptible power supply module during the switching process and the overload ratio of the other uninterruptible power supply modules during the switching transition period.

[0011] In one optional embodiment, determining the load reduction ratio includes: The overload ratio of the current uninterruptible power supply module during the switching process is determined according to the first formula and used as the first intermediate value; The overload ratio of the remaining uninterruptible power supply modules during the switching transition period is determined according to the second formula and used as the second intermediate value. The load reduction ratio is determined based on the first intermediate value, the second intermediate value, and the target condition; The first formula is: P1 = 1.5 × K; The second formula is: P2=(Pt-K×Pm) / [(N-1)×Pm]; The objective condition is: min{max(P1,P2)}; In the formula, P1 is the first intermediate value; K is the load reduction ratio; P2 is the second intermediate value; Pt is the total output power of the uninterruptible power supply system; Pm is the output power of a single uninterruptible power supply module; and N is the number of uninterruptible power supply modules operating in the uninterruptible power supply system.

[0012] In one optional embodiment, the step of sequentially switching the power supply of one phase of the uninterruptible power supply module from battery power to AC power includes: After any phase power supply switching of any of the uninterruptible power supply modules is completed and the power supply output is stable, the next phase power supply switching of one of the uninterruptible power supply modules will begin.

[0013] In one alternative embodiment, determining that the power supply output is stable includes: Collect DC bus voltage; If the fluctuation range of the DC bus voltage within a preset time period is less than a preset fluctuation threshold, the power supply output is determined to be stable.

[0014] In one alternative embodiment, determining that the power supply output is stable includes: The timer starts when a phase power supply switch of one of the uninterruptible power supply modules is triggered; When the preset duration is reached, the power supply output is confirmed to be stable.

[0015] To address the aforementioned technical problems, this application also provides an uninterruptible power supply system, comprising: multiple uninterruptible power supply modules and a control module connected in parallel; Each of the uninterruptible power supply modules is powered by a battery or mains power. The control module is used to implement the uninterruptible power supply switching control method described above.

[0016] The uninterruptible power supply (UPS) switching control method provided in this application utilizes a three-phase power supply achieved through a shared Vienna topology, where batteries and AC mains power are supplied in three phases. During the switch from battery power to AC mains power, each phase is sequentially switched from battery power to AC mains power. Specifically, for the shared Vienna topology corresponding to the current phase, the battery branch drive is stopped, and the shared Vienna topology is switched from battery boost mode to AC mains power factor correction mode. During this switching process, the other two shared Vienna topologies maintain continuous power supply. Since only the shared Vienna topology corresponding to the current phase temporarily exits battery power supply due to the cessation of battery branch drive during the switching process, while the other two shared Vienna topologies continue to operate in battery boost mode and continuously supply battery energy to the DC bus, the DC bus always has energy input during the entire switching window, and the DC bus voltage will not be continuously pulled down by the load. Simultaneously, the load originally borne by all three circuits is borne by the other two circuits during the switching period, maintaining the total output power of the three-phase power supply and ensuring uninterrupted load power supply. Once the phase switching is complete and the mains power factor correction mode is activated, the mains power will participate in the power supply. This allows subsequent phase switching to occur under a shared load of battery and mains power, thus distributing the power supply pressure at each switching stage. As a result, the DC bus voltage can be maintained throughout the entire battery-to-mains switching process, avoiding switching failures caused by the bus voltage dropping during the switching window. This achieves reliable and uninterrupted switching of the uninterruptible power supply from battery power to mains power, solving the problem of easy switching failures when switching from battery to mains power in existing shared topology UPS systems.

[0017] The uninterruptible power supply system provided in this application corresponds to the above method and has the same effect. Attached Figure Description

[0018] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A structural diagram of an uninterruptible power supply system provided in an embodiment of the present invention; Figure 2 A flowchart of an uninterruptible power supply switching control method provided in an embodiment of the present invention; Figure 3 This is a structural diagram of an uninterruptible power supply module provided in an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0021] The core of this application is to provide an uninterruptible power supply (UPS) switching control method and an UPS system.

[0022] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In related technologies, an uninterruptible power supply (UPS) is a special power supply that requires uninterrupted power output. To achieve uninterrupted output, UPS typically uses two input sources: AC power and battery power, with AC power as the default. In the event of a AC power failure, the battery takes over AC power supply; once AC power is restored, it switches back to AC power supply. However, during the switching process, neither the battery nor the AC power supply can provide power input. If the UPS load is high at this time, or the switching time is long, the DC bus voltage may not be maintained, leading to output interruption and failure to meet the uninterrupted output requirement.

[0024] To address the aforementioned problems, this application provides an uninterruptible power supply (UPS) switching control method. This method is applied to UPS systems, such as... Figure 1 As shown, it includes multiple uninterruptible power supply modules connected in parallel (i.e., Figure 1 Modules 1-6 in the module provide three-phase power via battery or AC mains power.

[0025] In related technologies, current uninterruptible power supply (UPS) systems operate with each UPS module sharing the load power during normal operation. For example... Figure 1 The illustrated scenario shows an uninterruptible power supply (UPS) module consisting of six UPS modules with a rated output power of 100K. When the load power is 600K, each UPS module provides 100K of power. It should be noted that... Figure 1 This is only one optional embodiment. This application does not limit the rated power of each uninterruptible power supply module, the capacity of the entire uninterruptible power supply system, or the number of modules included in the system.

[0026] Furthermore, the uninterruptible power supply switching control method provided in this application is as follows: Figure 2 As shown, it includes: S100: Sequentially switch the power supply of one phase of an uninterruptible power supply module from battery power to AC power, until all three phases of the uninterruptible power supply modules have completed the power supply switch.

[0027] In step S100, the power supply switching involves two different levels: the module level below the system level, and the three-phase level below the module level. This method provides specific switching schemes for the module level and the three-phase level switching respectively, meaning that the implementation of step S100 specifically includes: 1. Module layer; S101: When any uninterruptible power supply (UPS) module switches power, control the output power of the current UPS module to decrease, the output power of the remaining UPS modules to increase, and keep the total output power of the UPS system unchanged.

[0028] 2. Three-phase layer; S102: When any phase of any uninterruptible power supply module is switched, control the other two phases of the current uninterruptible power supply module to maintain power output and increase output power, so as to keep the output power of the current uninterruptible power supply module unchanged.

[0029] This embodiment also provides another optional implementation scheme. For example... Figure 3 As shown, each uninterruptible power supply module includes three sub-units corresponding to the three-phase power supply. Therefore, step S100 specifically involves sequentially switching the power supply of each sub-unit from battery power to AC power until all sub-units have completed the power supply switch.

[0030] Accordingly, during the power supply switching process of any sub-unit, the switching control schemes of the module layer and the three-phase layer described above are adapted to become: Three-phase layer: Controls the output power of the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit to decrease, and controls the output power of the sub-units belonging to other uninterruptible power supply modules to increase, so as to keep the total output power of the uninterruptible power supply system constant; Module layer: When the output power of the current uninterruptible power supply module is reduced, the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit are controlled to maintain power output and increase output power, so as to keep the output power of the uninterruptible power supply module unchanged.

[0031] In other words, this embodiment implements the smallest unit of switching defined at the logical level using a specific hardware structure called a sub-unit. Therefore, during sequential switching, a tangible physical entity can be used as the switching object, facilitating sequential switching and the implementation of switching control schemes at the module level and three-phase level.

[0032] It should also be noted that the sequential switching in step S100 refers to using the lowest level, i.e., any phase of any module, as the object of a switch (or the smallest unit). Therefore, when determining the order of sequential switching, only this needs to be used as the smallest unit; this application does not restrict the specific switching order. For example, the correspondence between modules and phases can be completely disrupted, treating each smallest unit that can be used as a switch object as an independent individual, and arranging the switching in any order. For example, a random order can be used for sequential switching, such as first switching phase B of module 3, then switching phase A of module 5, and so on, until all three phases of all modules have been switched.

[0033] In addition, switching can also be performed according to a pre-set specific sequence. For example, in an optional embodiment, the switching sequence rule for step S100 is: after the uninterruptible power supply modules supplying one phase of power are switched sequentially, the uninterruptible power supply modules supplying the next phase of power are switched sequentially. Figure 1 For example, after switching one phase (such as phase A) of 6 modules in sequence (the order between modules is not limited), then switching another phase (such as phase B) of 6 modules in sequence, and finally switching the last phase (such as phase C) of 6 modules in sequence.

[0034] In another optional embodiment, the switching sequence rule for step S100 is as follows: after the three-phase power supply switching of one uninterruptible power supply module is completed, the three-phase power supply switching of the next uninterruptible power supply module is performed. Furthermore... Figure 1 For example, the process involves first switching the three phases of a module (such as module 1) sequentially (the order of the three phases is not limited), then switching the three phases of the next module (such as module 2) sequentially, and so on, until all six modules have completed the sequential switching of the three phases.

[0035] Although this application does not restrict the specific order of switching, to better illustrate the specific switching schemes proposed by this method for the module layer and the three-phase layer respectively, the following explanation uses the example of completing the three-phase switching of one module before proceeding to the three-phase switching of the next module (still using... Figure 1 The optional example shown is an uninterruptible power supply system with a total output power of 600K, including six uninterruptible power supply modules 1-6 with a rated output power of 100K.

[0036] 1. For three-phase layers: First switch: Assume that the first switch is to phase A of module 1. In the three-phase layer, that is, the three phases ABC of module 1, since phase A is switched this time, phase A of module 1 has no power input. The other two phases B and C of module 1 maintain their original power input (i.e., battery) to bear the original output power of module 1, ensuring uninterrupted output of module 1.

[0037] Second switching: After phase A of module 1 completes the switching, assume that phase B of module 1 will perform the switching. Since phase B is the one switching, phase B of module 1 will have no power input. The other two phases of module 1, phases A and C, will maintain their power input to handle the original output power of module 1, thus ensuring uninterrupted output. Phase A has already completed the switching, so its power input is AC power. Phase C has not yet completed the switching, so its power input remains battery power.

[0038] The third switchover: After phase B of module 1 completes the switchover, only phase C of module 1 remains unswitched. At this time, phase C has no power input, and the other two phases of module 1, phases A and B, maintain power input to handle the original output power of module 1. Since phases A and B have already completed the switchover, their power input is AC mains power.

[0039] The three-phase switching for other modules is the same as in Module 1, and will not be repeated here. It is clear from the above that the purpose of this method is to set up the aforementioned three-phase switching scheme to ensure that the power output of a single uninterruptible power supply module remains uninterrupted, thus guaranteeing the basic function of the uninterruptible power supply module. However, this also brings a new problem: the power output that should have been shared by all three phases is now borne by only two of the unswitched phases. The output load borne by these two phases changes from one-third to one-half, equivalent to a 150% overload. Excessive overload increases the risk of circuit damage. This problem is addressed in this method through a module-level switching scheme.

[0040] 2. For the module layer: Since the first three switching operations all involve power supply switching to module 1, according to the specific switching scheme of the module layer, when module 1 is switched, its output power is reduced, i.e., it operates under reduced load. Meanwhile, the output power of the remaining modules 2-5 is increased to maintain the total output power of the entire uninterruptible power supply system, thus ensuring the basic functional requirements of the uninterruptible power supply.

[0041] For example, assuming the output power of module 1 is reduced to 70% of its original value, then the output power of module 1 is 100K. 70% = 70K. The 100K - 70K = 30K less power output by module 1 needs to be shared by modules 2-5. Assuming that modules 2-5 share the current (i.e., equally distribute the less power output by module 1 to ensure that the increase in output power of each module is as small as possible), then for modules 2-5, the overload ratio = 100% + 30K / 5 / 100K = 106%.

[0042] Similarly, for module 1 undergoing switching, its output power is reduced to 70% of its original value (70K) due to the reduced load operation. Therefore, even if the other two phases need to bear the full output power of module 1 during any phase switching, they only need to bear the reduced output power (70K), meaning each phase only needs to bear 70K / 2 = 35K. Therefore, the overload ratio of each of the other two phases is 35K / (100K / 3) = 105%. Alternatively, the overload ratio can be calculated using the following formula: Overload ratio = 150%. 70% = 105%, which is less than the overload ratio of 106% for modules 2-5. Therefore, after adjusting the module output power using the module-level switching scheme of this method, the maximum overload ratio of any smallest unit in the entire system (i.e., any phase of any module) is only 106%. This reduces the impact of overload on the circuit to an acceptable or even negligible level, while ensuring uninterrupted power supply output for the entire system.

[0043] Furthermore, the above examples also demonstrate that when adopting the second specific sequence option implementation (i.e., the specific switching sequence of first performing three-phase switching of a single module sequentially, and then performing three-phase switching of the next module), the number of power output adjustments required by the module-level switching control scheme is minimized. Only one control adjustment is needed to complete the three-phase switching of one module, and the entire system requires only six power adjustments. In contrast, for the first specific sequence option implementation, since the switching is performed sequentially by phase, each phase requires six different modules to complete the sequential switching, resulting in six output power adjustments, and a total of three adjustments for all three phases. The first scheme requires 18 output power adjustments (6 = 18), significantly more than the second scheme. Therefore, the second specific sequence implementation is superior to the first in terms of implementation difficulty and reliability. Furthermore, it's easy to understand that random or other specific sequence schemes require fewer output power adjustments than the first scheme but more than the second. Therefore, considering only implementation difficulty and reliability, the second specific sequence implementation has a more significant advantage.

[0044] As described above, the uninterruptible power supply (UPS) switching control method provided in this application, on the one hand, ensures that the basic functions of the UPS can still be realized during power input switching by switching one phase at a time during three-phase switching within the module, and by having the other two phases share the load when any phase cannot maintain output due to switching, thus maintaining a constant output power. On the other hand, this method also sets up a current imbalance control method between modules, causing the module currently switching to operate at reduced load while other modules operate at overload. By utilizing the difference in the number of modules, the lost output power during reduced load operation is compensated for while preventing excessive overload of any module. Furthermore, because the module currently switching operates at reduced load, the overload ratio of the other two phases that are not switching and require overload operation can be smaller during three-phase switching within the module, thereby controlling the overload ratio of each component circuit in the entire system within a small range and avoiding additional safety hazards. For example, in one of the examples given in the above embodiments, the maximum overload ratio of the system during switching is only 106%, and the increased output power is only 6%, which can be ignored in most scenarios of uninterruptible power supply applications.

[0045] On the other hand, the 70% derating ratio mentioned in the above embodiments is only an optional implementation scheme, and this application does not limit this value. In practical applications, the derating ratio can be a value pre-set according to actual needs to guide the implementation of the module-level switching scheme. It is known that the lower the derating ratio, the lower the overload ratio of the two phases of the unswitched uninterruptible power supply module currently being switched, but the overload ratio of the remaining unswitched uninterruptible power supply modules increases because they have to share more output power. Conversely, when the derating ratio is higher, the overload ratio of the remaining modules decreases, while the overload ratio of the other two phases of the current module increases. It is also known that the overall stability and reliability of the uninterruptible power supply system are affected by each component circuit. That is, an increase in the risk of burnout of each module and each phase circuit (which is directly positively correlated with the overload ratio) will lead to a decrease in the stability and reliability of the entire system.

[0046] Based on this, this embodiment provides an optional implementation scheme for the load reduction ratio. When controlling the output power of the current uninterruptible power supply (UPS) module to decrease in step S101, it specifically includes: controlling the output power of the current UPS module to decrease according to a preset load reduction ratio. The load reduction ratio is determined based on the parameters of the UPS system, and the target condition is to minimize the maximum value between the overload ratio of the current UPS module during the switching process and the overload ratio of other UPS modules during the switching transition period.

[0047] In other words, this embodiment aims to minimize the overall overload ratio of each smallest unit capable of power input switching in the entire uninterruptible power supply system, thereby constraining the value of the load reduction ratio. This ensures that the load reduction ratio determined by this objective condition achieves the goal of minimizing the overall overload ratio of the uninterruptible power supply system, avoiding a significant increase in the risk of circuit burnout due to the implementation of this method.

[0048] Furthermore, this embodiment also provides an optional implementation scheme for determining the load reduction ratio based on the target conditions determined above: the overload ratio of the current uninterruptible power supply module during the switching process is determined according to the first formula, as the first intermediate value; the overload ratio of the remaining uninterruptible power supply modules during the switching transition period is determined according to the second formula, as the second intermediate value; and the load reduction ratio is determined according to the first intermediate value, the second intermediate value and the target conditions.

[0049] The first formula is: P1 = 1.5 × K; The second formula is: P2=(Pt-K×Pm) / [(N-1)×Pm]; The objective condition is: min{max(P1,P2)}; In the formula, P1 is the first intermediate value; K is the load reduction ratio; P2 is the second intermediate value; Pt is the total output power of the uninterruptible power supply system; Pm is the output power of a single uninterruptible power supply module; and N is the number of uninterruptible power supply modules operating in the uninterruptible power supply system.

[0050] The objective condition is in the form of min{f(x)}, where f(x) is a function, i.e., max(P1,P2), indicating that the objective condition is to minimize max(P1,P2), which means minimizing the larger of P1 and P2. Regarding the definition of N, it's important to emphasize that the example above assumes all six uninterruptible power supply (UPS) modules in the UPS system are operating. However, in practical applications, due to redundancy considerations, not all UPS modules may be operating. Therefore, when calculating P2, the total number of UPS modules cannot be used.

[0051] This embodiment provides a scheme for determining the load reduction ratio based on mathematical methods, which conforms to the processing logic of hardware devices with data processing capabilities such as computers. This makes it easier to automate the load reduction ratio determination step using machines and other equipment, reducing reliance on manual labor and improving the efficiency and reliability of the entire method.

[0052] On the other hand, the sequential switching emphasized in this method, besides referring to the order of switching, also implies that the two switching actions should not be performed simultaneously. Generally, since both "two" refer to switching actions, the next switching action should begin only after the previous one is completed. Furthermore, regarding the connection between the two switching actions in step S100, this embodiment also provides an optional implementation: after the power supply switching of any phase of any uninterruptible power supply module is completed and the power output is stable, the next one-phase power supply switching of an uninterruptible power supply module begins.

[0053] As described above, this embodiment adds another condition to the existing condition of starting the next switch only after the previous switch is completed: the power supply output of the target object in the previous switch must be stable. As also described above, when this method sequentially switches between any phase of any module, other smallest switching units not involved in the switch need to adjust their output power to ensure the overall system output is stable and does not experience excessive overload. However, this embodiment, by performing the next switch only after the smallest switching unit of the previous switch has stabilized, effectively ensures that the output power of other smallest switching units not involved in the switch (mainly the smallest switching unit of the previous switch) remains stable during the next switch, thus ensuring that the aforementioned effect is achieved better.

[0054] Furthermore, regarding how to determine whether the power supply output was stable during the last switch, this embodiment provides an optional implementation scheme: S201: The timer starts when a phase power supply switch of an uninterruptible power supply module is triggered; S202: When the timer reaches the predetermined duration, the power supply output is confirmed to be stable.

[0055] It is known that, except in special cases, the time required for any smallest switching unit to complete the power input switching will fall within a certain range. Based on this time range, a predetermined duration that can cover this event can be set, thereby ensuring that the power output of the smallest switching unit has stabilized after the predetermined delay. The determination scheme provided in this embodiment is simple to implement and does not involve complex determination logic; it can be implemented using only the simplest delay logic or delay circuit.

[0056] In addition, this embodiment also provides another optional method for determining whether the power supply output is stable: S301: Acquires DC bus voltage; S302: If the fluctuation range of the DC bus voltage within a preset time period is less than the preset fluctuation threshold, the power supply output is determined to be stable.

[0057] In this embodiment, the stability of the power supply output is determined by collecting the DC bus voltage parameter. Based on the structure and principle of the uninterruptible power supply module, it is readily known that output fluctuations in the smallest switching unit will cause fluctuations in the DC bus voltage. Therefore, this embodiment can directly determine the stability of the power supply output by monitoring the fluctuations in the DC bus voltage. Furthermore, the determination method provided in this embodiment is not limited to a fixed predetermined duration and can detect the stabilization time in different markets under different operating conditions, thereby improving the overall efficiency of the method for sequentially switching power supply inputs.

[0058] In the above embodiments, an uninterruptible power supply (UPS) switching control method has been described in detail. This application also provides an embodiment corresponding to an UPS system. Figure 1 As shown, this embodiment provides an uninterruptible power supply (UPS) system, including: multiple UPS modules connected in parallel and a control module; each UPS module is supplied with three-phase power via a battery or mains power; the control module is used to implement the UPS switching control method as described in any of the above embodiments.

[0059] Since the embodiments of the system part correspond to the embodiments of the method part, please refer to the description of the embodiments of the method part for the embodiments of the system part, and they will not be repeated here.

[0060] The uninterruptible power supply (UPS) system provided in this embodiment achieves the same technical effects as the aforementioned UPS switching control method. Specifically, during three-phase switching within a module, this system switches phase-by-phase sequentially, and if any phase cannot maintain output due to switching, the other two phases share the load to maintain a constant output power. This ensures that the basic functions of the UPS are still implemented during power input switching. Furthermore, this system employs a current imbalance control method between modules, causing the currently switching module to operate at reduced load while other modules operate at overload. Utilizing the difference in the number of modules, this compensates for the lost output power during reduced load operation while preventing any single module from experiencing excessive overload. Simultaneously, because the currently switching module operates at reduced load, the overload ratio of the other two phases that are not switching and require overload operation can be even smaller during three-phase switching within this module. This keeps the overload ratio of each component circuit in the entire system within a small range, avoiding additional safety hazards.

[0061] The uninterruptible power supply (UPS) switching control method and UPS system provided in this application have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of this application.

[0062] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for uninterruptible power supply switching control, characterized in that, It is applied to an uninterruptible power supply system, which includes multiple uninterruptible power supply modules connected in parallel, and the uninterruptible power supply modules are provided with three-phase power supply through batteries or mains power; The methods include: The power supply of one phase of each uninterruptible power supply module is switched from battery power to mains power in sequence until all three phases of the uninterruptible power supply modules have been switched. When any of the uninterruptible power supply modules switches power, the output power of the current uninterruptible power supply module is reduced, the output power of the other uninterruptible power supply modules is increased, and the total output power of the uninterruptible power supply system remains unchanged. When any phase of any of the uninterruptible power supply modules switches power, the other two phases of the current uninterruptible power supply module are controlled to maintain power output and increase output power, so as to keep the output power of the current uninterruptible power supply module unchanged.

2. The uninterruptible power supply switching control method according to claim 1, characterized in that, The sequential switching of power supply from battery power to AC power for one phase of the uninterruptible power supply module includes: After completing the sequential switching of the three-phase power supply of one of the uninterruptible power supply modules, the sequential switching of the three-phase power supply of the next uninterruptible power supply module is performed.

3. The uninterruptible power supply switching control method according to claim 1, characterized in that, The sequential switching of power supply from battery power to AC power for one phase of the uninterruptible power supply module includes: After each of the uninterruptible power supply (UPS) modules that have completed the power supply of one phase has switched sequentially, the UPS modules that have completed the power supply of the next phase have switched sequentially.

4. The uninterruptible power supply switching control method according to claim 1, characterized in that, Each of the uninterruptible power supply modules includes three sub-units corresponding to the three-phase power supply; The process of sequentially switching the power supply of one phase of each uninterruptible power supply module from battery power to AC power, until all three phases of the uninterruptible power supply modules have completed the power supply switching, includes: The power supply of each subunit is switched from battery power to AC power in sequence until all subunits have completed the power supply switch. During the power supply switching process of any of the sub-units: The output power of the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit is reduced, and the output power of the sub-units belonging to the other uninterruptible power supply modules is increased, so as to keep the total output power of the uninterruptible power supply system constant. Based on the reduced output power of the current uninterruptible power supply module, the other two sub-units belonging to the same uninterruptible power supply module as the current sub-unit are controlled to maintain power output and increase output power, so as to keep the output power of the uninterruptible power supply module unchanged.

5. The uninterruptible power supply switching control method according to any one of claims 1 to 4, characterized in that, The control of reducing the output power of the current uninterruptible power supply module includes: The output power of the uninterruptible power supply module is reduced according to the preset load reduction ratio. The load reduction ratio is determined based on the parameters of the uninterruptible power supply system, and the target condition is to minimize the maximum value between the overload ratio of the current uninterruptible power supply module during the switching process and the overload ratio of the other uninterruptible power supply modules during the switching transition period.

6. The uninterruptible power supply switching control method according to claim 5, characterized in that, Determining the load reduction ratio includes: The overload ratio of the current uninterruptible power supply module during the switching process is determined according to the first formula and used as the first intermediate value; The overload ratio of the remaining uninterruptible power supply modules during the switching transition period is determined according to the second formula and used as the second intermediate value. The load reduction ratio is determined based on the first intermediate value, the second intermediate value, and the target condition; The first formula is: P1 = 1.5 × K; The second formula is: P2=(Pt-K×Pm) / [(N-1)×Pm]; The objective condition is: min{max(P1,P2)}; In the formula, P1 is the first intermediate value; K is the load reduction ratio; P2 is the second intermediate value; Pt is the total output power of the uninterruptible power supply system; Pm is the output power of a single uninterruptible power supply module; and N is the number of uninterruptible power supply modules operating in the uninterruptible power supply system.

7. The uninterruptible power supply switching control method according to any one of claims 1 to 4, characterized in that, The sequential switching of power supply from battery power to AC power for one phase of the uninterruptible power supply module includes: After any phase power supply switching of any of the uninterruptible power supply modules is completed and the power supply output is stable, the next phase power supply switching of one of the uninterruptible power supply modules will begin.

8. The uninterruptible power supply switching control method according to claim 7, characterized in that, Ensuring stable power output includes: Collect DC bus voltage; If the fluctuation range of the DC bus voltage within a preset time period is less than a preset fluctuation threshold, the power supply output is determined to be stable.

9. The uninterruptible power supply switching control method according to claim 7, characterized in that, Ensuring stable power output includes: The timer starts when a phase power supply switch of one of the uninterruptible power supply modules is triggered; When the preset duration is reached, the power supply output is confirmed to be stable.

10. An uninterruptible power supply system, characterized in that, include: Multiple uninterruptible power supply modules and control modules connected in parallel; Each of the uninterruptible power supply modules is powered by a battery or mains power. The control module is used to implement the uninterruptible power supply switching control method as described in any one of claims 1 to 9.

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