Method for reducing stress on UPS components during transition from inverter to green / bypass operation

Abstract

To provide a system and method for controlling an Uninterruptible Power Supply (UPS).SOLUTION: In the method, after an inverter of an UPS is instructed to transition from an on-line mode to a green mode, a monitoring period begins. During the monitoring period, a parameter related to an output current of the inverter is monitored and compared to a predetermined threshold. If the parameter exceeds the predetermined threshold before a fixed period of time has elapsed, the inverter is turned off early. If the inverter current does not exceed the predetermined value within the fixed period of time, the inverter is turned off.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Application No. 62 / 914,034, filed October 11, 2019, entitled "SYSTEM AND METHOD FOR PREVENTING BYPASS-RELAY DAMAGE IN A POWER SUPPLY", which is hereby incorporated by reference in its entirety.

[0002] This disclosure generally relates to systems and methods for controlling an uninterruptible power supply (UPS).

Summary of the Invention

Problems to be Solved by the Invention

[0003] Power devices such as uninterruptible power supplies (UPSs) that supply regulated and / or uninterrupted power to sensitive and / or critical loads such as computer systems and other data processing systems are known. Known uninterruptible power supplies include online UPSs, offline UPSs, and other devices. An online UPS supplies regulated AC power and backup AC power in the event of an interruption of the primary power source of AC power. An offline UPS generally does not regulate the input AC power in the event of an interruption of the primary AC power source, but supplies backup AC power. A line-interactive UPS is similar to an offline UPS in that it switches to battery power when a power outage occurs, but generally has a multi-tap transformer that regulates the output voltage supplied by the UPS.

Means for Solving the Problems

[0004] According to one embodiment, an uninterruptible power supply (UPS) includes an input unit configured to receive input power, a backup input unit configured to receive backup power from a backup power source, an output unit configured to supply output power to a load from at least one of the input power or the backup power, an inverter connected to the input unit, the backup input unit, and the output unit and configured to supply an inverter output current, a sensor configured to detect a parameter indicating the inverter output current, a relay connected between the input unit and the output unit, and at least one controller connected to the sensor, the controller being configured to determine that the relay is closed and to turn off the inverter based on the determination that the relay is closed.

[0005] In one example, the at least one controller is configured to determine that the relay is closed based on a parameter indicating the inverter output current.

[0006] In another example, the at least one controller is configured to determine that the relay is closed based on a derivative value of the inverter output current.

[0007] In one example, the at least one controller is connected to the relay, configured to detect that the inverter output current exceeds a threshold value, and configured to determine that the relay is closed based on the detection that the inverter output current exceeds the threshold value.

[0008] In another example, the at least one controller is configured to determine that the relay is closed based on the elapse of a predetermined period of time after instructing the relay to close.

[0009] In one embodiment, the UPS includes a power factor correction (PFC) circuit, and the sensor is configured to detect a current at an input of the PFC circuit as a parameter indicating the inverter output current.

[0010] In other embodiments, the uninterruptible power supply further includes a second input unit configured to receive a second input power and supply the second input power to the relay.

[0011] In one embodiment, the sensor is configured to detect the inverter output current at an output of the inverter.

[0012] In other embodiments, the sensor is configured to detect a current at an input of the inverter as a parameter indicating the inverter output current.

[0013] According to one embodiment, a method for operating an uninterruptible power supply (UPS) includes receiving input power at an input unit, receiving backup power from a backup power source, supplying output power from at least one of the input power or the backup power to a load, detecting a parameter indicating an inverter output current from an inverter of the UPS, determining that a relay is closed, and turning off the inverter included based on the determination that the relay is closed.

[0014] In one embodiment, the method further includes determining that the relay is closed based on a parameter indicating the inverter output current.

[0015] In other embodiments, the method further includes detecting that a parameter indicating the inverter output current exceeds a threshold in response to instructing the relay to close, and determining that the relay is closed based on the detection that the inverter output current exceeds the threshold.

[0016] In one embodiment, the method further comprises determining that the relay has closed based on the elapse of a predetermined period of time.

[0017] According to one embodiment, a persistent computer-readable medium stores a sequence of computer-executable instructions for controlling an uninterruptible power supply (UPS) comprising an input section configured to receive input power, a backup input section configured to receive backup power from a backup power source, an output section configured to supply output power to a load from at least one of the input power or the backup power, an inverter connected to the input section, the backup input section, and the output section, a sensor configured to detect a parameter regarding an inverter output current of the inverter, a relay connected between the input section and the output section and configured to supply output power, and at least one controller connected to the sensor, the sequence of computer-executable instructions causing the at least one controller to detect a parameter regarding the inverter output current, determine that the relay has closed, and instruct the inverter to turn off based on the determination that the relay has closed.

[0018] In one embodiment, the sequence of computer-executable instructions causes the at least one controller to determine that the relay has closed based on a parameter regarding the inverter output current.

[0019] In other embodiments, the at least one controller is connected to the relay, and the sequence of computer-executable instructions causes the at least one controller to detect that a parameter indicating the inverter output current exceeds a threshold in response to an instruction to close the relay, and determine that the relay has closed based on the detection that the inverter output current exceeds the threshold. which is to command as follows.

[0020] In one embodiment, the UPS includes a power factor correction (PFC) circuit, and the sequence of computer-executable instructions commands the at least one controller to detect a current at an input of the PFC circuit as a parameter related to the inverter output current.

[0021] In other embodiments, the sequence of computer-executable instructions commands the at least one controller to determine that the relay has closed based on the elapse of a predetermined period of time.

[0022] In one embodiment, the sequence of computer-executable instructions commands the at least one controller to detect the inverter output current at an output of the inverter.

[0023] In other embodiments, the sequence of computer-executable instructions commands the at least one controller to detect a current at an input of the inverter as a parameter related to the inverter output current.

[0024] The following describes the accompanying drawings, which are not intended to be drawn to scale, showing various aspects in at least one embodiment. These drawings are included to illustrate various aspects and embodiments and to provide a further understanding, and are incorporated into and form a part of the present specification, but are not intended to define the limits of the present disclosure. In these drawings, each identical or nearly identical component shown in the various drawings is denoted by a similar reference numeral. For clarity of illustration, not all components may be labeled in all drawings.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0026] Examples of the methods and systems described in this specification are not limited to being applied to the details of the structures and configurations of the components described in the following description or illustrated in the accompanying drawings. These methods and systems can be implemented in other embodiments and can be executed or implemented in various ways. Examples of specific embodiments are presented in this specification for illustrative purposes only and are not intended to be limiting. In particular, the act of describing any one or more of the embodiments, components, elements, and features is not intended to exclude their similar roles in any other embodiments.

[0027] Furthermore, the terminology and phraseology used herein are for descriptive purposes and should not be construed as limiting. Any reference herein to an embodiment, implementation, component, element, or act of a system and method in the singular encompasses embodiments that include a plurality, and any reference in the plural to any embodiment, component, element, or act encompasses embodiments that include only the singular. References in the singular or plural are not intended to limit the system or method, their components, acts, or elements described herein. The use of "including", "comprising", "having", "containing", "involving", and variations thereof herein is intended to cover the listed items and their equivalents, as well as additional items. References to "or" can be construed as inclusive, and thus can indicate any single one, more than one, or all of the recited items. Further, in the event of any discrepancy in the use of terms between this specification and the documents incorporated herein by reference, the terms used in the incorporated references are intended to supplement the terms of this specification, and the use of terms in this specification controls for any irreconcilable discrepancies.

[0028] In an existing UPS system, the parallel operation of the inverter and the commercial power source can occur instantaneously during the transition from the online operation mode to the bypass operation mode after the bypass relay is closed. After the bypass relay is closed, a conduction path can be formed between the inverter, the inverter relay, the bypass relay, and the commercial line connected to the bypass relay. During this time of the parallel connection of the commercial line and the inverter, the current in the components of the UPS can continue to increase until the inverter is turned off. This can stress the components of the UPS and result in the use of more robust and expensive components to handle the increasing current. If the increasing current is not properly controlled for the relays used in the transition from the online mode to the bypass mode, there is a risk of melting the relays and causing permanent damage to them. Further, there is a risk that the inverter may back-feed the commercial power source during this parallel connection.

[0029] At least some embodiments of the present invention disclosure provide a method, a UPS, and a persistent computer-readable medium for adaptively adjusting the timing to turn off the power source or the inverter output of the UPS after the bypass relay is latched (closed). At least some embodiments disclosed herein can handle non-constant relay timing and inter-unit timing variations without using additional hardware circuits, and improve the existing UPS system by shortening the time for the parallel operation to occur.

[0030] An embodiment of the uninterruptible power supply device 100 according to the present invention disclosure will be described below with reference to FIG. 1, which shows a functional block diagram of the first UPS 100. This UPS 100 is an online UPS and also includes a controller 12, a rectifier / power factor correction (PFC) circuit 14, a DC-DC converter 16, a battery 18, a polarized capacitor 20, a DC bus 22, an inverter 24, an inductor 26, a current sensor 28, a backfeed line relay 32, a backfeed non-polar relay 34, a bypass relay 36, an inverter relay 38, an input section 101, a neutral input section 103, an output section 104, and a neutral output section 105. The UPS 100 supplies power to the load 110 based on the input power received at the input section 101 and / or the power from the battery 18.

[0031] In some embodiments, the inductor 26 is one of an air-core inductor, an iron-core inductor, and a ferrite-core inductor.

[0032] The input section 101 is connected to the backfeed line relay 32 which is connected to the PFC circuit 14. Each output section of the PFC circuit 14 is connected to the inverter 24. The output sections of the PFC circuit 14 are connected to each other by the polarized capacitor 20, and the output section of the PFC circuit connected to the anode of the polarized capacitor 20 forms the DC bus 22 which is connected to the DC-DC converter 16. This DC bus 22 also acts as a backup input section that receives power from the battery 18 via the DC-DC converter 16. The battery 18 acts as a backup power supply. The cathode of the polarized capacitor 20 is connected to the PFC circuit 14, the inverter 24, and the DC-DC converter 16. One output section of the DC-DC converter 16 is connected to the anode of the battery 18, and the other output section of the DC-DC converter 16 is connected to the cathode of the battery 18 and the ground terminal. The inverter 24 has an output section connected to the inductor 26 and another output section connected to the neutral output section 105. The neutral output section 105 is connected to the PFC circuit 14, the inverter 24, the backfeed non-polar relay 34, and the load 110. The inductor 26 is connected to the current sensor 28 which is connected to the inverter relay 38. This inverter relay 38 is connected to both the bypass relay 36 and the output section 104 connected to the load 110. The load 110 is connected between the output section 104 and the neutral output section 105. The bypass relay 36 is connected to the input section 101 and the backfeed line relay 32.

[0033] In FIG. 1, the controller 12 is shown as being connected to a PFC circuit 14, a DC-DC converter 16, an inverter 24, a current sensor 28, a backfeed relay 32, a backfeed polarity-free relay 34, a bypass relay 36, and an inverter relay 38. Each solid line connected to the controller 12 represents a communication path through which the controller 12 can transmit a signal or receive a signal from one or more internal components of the UPS 100. Each relay 32, 34, 36, 38 shown in FIG. 1 is configured to switch between an open position and a closed position when receiving an instruction from the controller 12. In the closed position, a conductive path is formed between the first terminal and the second terminal of a given relay. For example, when the bypass relay 36 is in the open state (as shown in FIG. 1), current does not conduct between the input section 101 and the output section 104 within the bypass relay 36. Conversely, when the bypass relay 36 is in the closed state, the load 110 is connected between the output section 104 and the neutral output section 105, and if power is present at the input section 101, current conducts through the relay connection to the input section 101 and the relay connection to the output section 104.

[0034] The UPS 100 shown in FIG. 1 is a single-phase UPS having a double-conversion (AC-DC, DC-AC) topology. In other embodiments, the UPS 100 can be a polyphase UPS such as a three-phase UPS. In FIG. 1, the UPS 100 is shown as operating in the online mode, in which case the UPS is configured to supply output power to the load 110 using the inverter 24. As shown in FIG. 1, the backfeed line relay 32 is configured to connect the input section 101 to the PFC circuit 14 in the closed position. The bypass relay 36 is configured to be in the open position. The backfeed polarity-free relay 34 and the inverter relay 38 are shown as being in the closed position. When the backfeed line relay 32, the backfeed polarity-free relay 34, the bypass relay 36, and the inverter relay 38 are configured to be in these positions, the UPS 100 is configured to operate in the online mode. To proceed to the bypass mode, which is a more efficient operating mode, the controller 12 activates (closes) the bypass relay 36 and turns off the inverter 24.

[0035] In some embodiments, one or more of the backfeed line relay 32, the backfeed non-polar relay 34, the bypass relay 36, and the inverter relay 38 are electromechanical relays (EMRs). An electromechanical relay is a device that converts magnetic flux into mechanical force and often uses a spring to operate electrical contacts within the relay with this mechanical force. On the other hand, a solid-state relay (SSR) has no moving parts and obtains its function from semiconductors. Due to the mechanical nature of the EMR, the time required for the internal switch to separate from one contact and make contact with the other contact can vary based on the aging of the EMR, the type of EMR, spring force, contact wear, coil damage, temperature, and other factors. Therefore, when controlling the closing of an EMR, it is impossible to fully predict how long it will take for the internal switch of the EMR to make contact from one position to the other. Therefore, if the controller 12 uses only a fixed time to interrupt the output of the inverter 24 after instructing the bypass relay 36 to close, the inverter 24 can supply power to the input section 101 via the bypass relay 36.

[0036] FIG. 2 shows a functional block diagram of the UPS 100 transitioning to the bypass operation mode. What FIG. 2 differs from FIG. 1 is that the bypass relay 36 is closed and there is a current 120 between the inverter relay 38 and the bypass relay 36. During the transition from the online operation mode to the bypass operation mode under normal operation of the UPS 100, the controller 12 instructs the bypass relay 36 to close and then disables (turns off) the inverter 24, so that the input AC power is supplied directly to the output line 104 via the bypass relay 36. After the inverter 24 is instructed to turn off, the inverter relay 38 is instructed to open. In some embodiments, after the controller 12 instructs the inverter 24 to turn off, the controller 12 instructs the backfeed line relay 32 and the backfeed non-polar relay 34 to open to prevent power from being backfed to the power grid.

[0037] In an ideal scenario, the optimal transition from online mode to bypass mode is that the bypass relay 36 closes and at the same time the inverter 24 stops. However, if the controller 12 stops the inverter 24 too early (before the bypass relay 36 closes), the load 110 will drop and / or the load input capacitor will be drained, which may result in a large inrush current when the bypass relay 36 closes. If the controller 12 stops the inverter 24 too late (a long time after the bypass relay 36 has closed), the parallel connection of the commercial power supply and the inverter power supply may supply or conduct a large current that may stress or damage the internal components of the inverter 24. In such a scenario, the inverter 24 may attempt to supply (back-feed) power to the connected commercial power supply. FIGS. 3 and 4 show a second UPS 200 that is substantially the same as the first UPS 100 except that the second UPS 200 includes a second input section 102. Common elements in the UPS 100 and UPS 200 are labeled with the same reference numerals. The second input section 102 is connected to the bypass relay 36. As shown in FIGS. 3 and 4, the second input section 102 can receive input power and is separate from the input section 101. In some embodiments, the input section 101 and the second input section 102 are designed to receive power from different power sources to provide additional redundancy. In one example, one of the input section 101 and the second input section 102 receives power from a commercial power supply and the other receives power from an alternative energy source. In some embodiments, the alternative energy source is one or more of solar power, wind power, and hydroelectric power.

[0038] Some embodiments include an optional capacitor connected between the neutral output section 105 and the conductive line connecting the sensor 28 and the inverter relay 38 in each of FIGS. 1, 2, 3, and 4.

[0039] As shown in FIGS. 1 and 2, a current sensor 28 is connected between an inductor 26 and an inverter relay 38, and the inverter output current of an inverter 24 is measured as a parameter indicating the current output by the inverter 24. In some embodiments, the UPS 100 or UPS 200 has one or more current sensors including the current sensor 28. Each of the one or more current sensors can be connected to different locations within the UPS 100 or UPS 200. In one embodiment, in addition to or instead of the current sensor 28 connected between the inductor 26 and the inverter relay 38, a current sensor is connected to the DC bus 22, and the current received by the input section of the inverter 24 is measured as a parameter indicating the output current of the inverter 24. In some embodiments, a magnification factor is applied to the current received to estimate the output current of the inverter 24. Other magnification factors can be similarly applied to other locations of the one or more current sensors. In other embodiments, the current sensor 28 is connected to the input section of the PFC circuit 14 that is connected to both the PFC circuit 14 and the backfeed line relay 32. A magnification factor or an individual threshold is compared with the value of the current sensor 28 at the input section of the PFC circuit 14 to determine whether the bypass relay 36 is closed. In some embodiments, a plurality of one or more sensors are used, and the plurality includes the current sensor 28, and the parameter indicating the output current is the weighted average of the current measurement values of each current sensor.

[0040] In FIGS. 1 to 4, the lines that are mutually toleranced and crossover are not electrical connections. The solid black circles that linearly overlap indicate that the line below the circle is electrically connected. Inside each of the backfeed line relay 32, the backfeed non-polar relay 34, the bypass relay 36, and the inverter relay 38, there are three electrical contacts indicated by circles. The line connecting one of these circles to the component outside the corresponding relay indicates a connection. For example, the input section 101 is connected to the PFC circuit 14 via the backfeed relay 32. The operation of the first UPS 100 will be continued below. The second UPS 200 operates in substantially the same manner because it receives the input power applied to all points of the first UPS 100 except that it has an additional input section 102.

[0041] The operation of the first UPS 100 will be described in detail below with respect to method 500 shown as a logic flowchart in FIG. 5. Method 500 includes at least three acts 502, 506, and 506 and two conditions 504 and 508. In some embodiments, the controller 12 executes each act and condition in method 500. Some embodiments implement this method 500, such as a firmware algorithm stored as program instructions in the internal storage device of the UPS 100.

[0042] In method 500, the current sensor 28 is used to convert the inverter output current into an ADC measurement value so that the controller 12 can detect an increase in the ADC measurement value, and an increase in the ADC measurement value indicates the landing of the bypass relay 36 and the start of backfeeding of the current 120 to the commercial power supply.

[0043] In the first act 502 of method 500, the controller 12 instructs the UPS 100 to shift from the online mode to the bypass mode. For the shift to the bypass mode, the controller 12 instructs the bypass relay 36 to close. After the bypass relay 36 is instructed to close, the controller 12 begins to monitor the current detected by the current sensor 28. In some embodiments, the controller 12 waits for a predetermined period of time before monitoring the current by the current sensor 28. In one example, this predetermined time is in the range of about 0.1 ms to about 5 ms. In other examples, this predetermined time is in the range of about 0.01 ms to about 10 ms. In one example, this predetermined time is in the range of about 0.001 ms to about 50 ms.

[0044] The controller 12 then compares, as a first condition 504, the most recent current value detected by the current sensor 28 with a predetermined value of the current. In some embodiments, this predetermined value is about 125% of the normal current output by the inverter 24. In some embodiments, this predetermined value is a current threshold adjusted for a specific load 110. In one example, the load is about 5.5 kW consumed by a server rack, the maximum capacity of the inverter 24 is about 30 A, and the current threshold is set to about 24 A, which is about 80% of the maximum capacity. In other examples, the current threshold takes on a range. According to some aspects, this range is about 3 to about 5 times the RMS value. For example, if the RMS value is about 30 A, a range of approximately 100 A is appropriate. In some embodiments this range is from about 30 A to 100 A. In other examples this range is from about 24 A to 30 A. In some embodiments this range is from about 10 A to 50 A. If the current value detected by the sensor 28 exceeds the predetermined value (yes), the first condition 504 is satisfied and method 500 proceeds to the second act 506. If the current value detected by the sensor 28 does not exceed the predetermined value (no), method 500 proceeds to evaluate the second condition 508. In some embodiments, the first condition 504 compares the current increase per unit time detected by the sensor 28 with a threshold representing a predetermined differential value of the current.

[0045] In the embodiments shown in FIGS. 1-4, current sensor 28 is electrically connected to the output of inverter 24. This inverter output is connected to inductor 26, which is connected between inductor 26 and inverter relay 38 and to current sensor 28 that measures the output current of inverter 224. In other embodiments, sensor 28 or an additional sensor can be connected to the input of inverter 24. For example, in some embodiments, current sensor 28 is connected to DC bus 22. Other locations of current (voltage) sensors within UPS 100 are included within the embodiments described herein. The specific value indicating the presence of current 120 that sensor 28 monitors can vary based on the location of sensor 28 within UPS 100, and the acts and conditions of method 500 are the same for each location. More specifically, in different embodiments, any sensor for determining parameters regarding the output current from the inverter can be used in addition to or in place of current sensor 28 to detect an increase in output current after UPS 100 switches to bypass mode.

[0046] The second condition 508 compares the time elapsed since the controller 12 commands the UPS 100 to close the bypass relay 36 in the first action 502 with a predetermined time threshold. This threshold represents the maximum period of time that can elapse since the bypass relay 36 is commanded to close. According to some aspects, this predetermined threshold is from about 1 ms to about 2 ms. In some embodiments, this predetermined threshold is 10 ms. In some embodiments, this threshold is 13 ms. When the current time (of the second condition 508 being evaluated at that point) exceeds the predetermined threshold, the second condition 508 is satisfied (yes), and the method 500 proceeds to the third action 510. When the current time does not exceed the predetermined threshold, the second condition 508 is not satisfied (no), and the method 500 returns to evaluating the first condition 504. Some embodiments use a fixed relay time as the predetermined threshold for closing, taking into account a margin for determining the time to interrupt the inverter 24 after the controller 12 commands the bypass relay 36 to close, based on the average relay time (for the type of relay used as the bypass relay 36).

[0047] In some embodiments, when the second condition is not satisfied (no), the method 500 returns to evaluating the second condition 508. In one embodiment, the method 500 includes the step of evaluating the first condition 504 one or more times before proceeding to evaluate the second condition 508 when the first condition 504 is not satisfied. Some examples include a predetermined waiting period in the first condition 504 before comparing a parameter representing the current of the inverter 24 with a predetermined threshold, and then proceeding to evaluate the second condition 508.

[0048] After commanding the bypass relay 36 to close, the time to interrupt the inverter 24 must not be less than the relay flyback time; otherwise, a large inrush current from the commercial power supply to the load 110 may occur, damaging the relay and / or causing damage to other UPS components.

[0049] In some embodiments, method 500 is configured to result in one of two possible outcomes. In one outcome, the first condition 504 is satisfied and the controller 12 commands the inverter 24 to turn off early (before exceeding a predetermined time threshold). In the other outcome, the second condition 508 is satisfied and as a result of the elapse of a predetermined period of time, the controller 12 commands the inverter 24 to turn off. Some embodiments include additional conditions or actions. In one example, a third condition 505 (not shown) can be evaluated between the first condition 504 and the second condition 508, and this third condition evaluates whether the inverter current is different from the value checked at the first condition 504. In such an example, the first condition 504 evaluates the current against a first current value, and if the current does not exceed that current value, a second, higher current value is evaluated at the third condition 505. If the current is exceeded at the third condition 505, method 500 proceeds to the second action 506, and if not, proceeds to the second condition 508.

[0050] Figure 6 shows a timing sequence 600 in the first UPS 100 and the second UPS 200 regarding the transition between the online mode and the bypass mode when the second condition 508 of the method 500 is satisfied. In this timing sequence 600, at the first point in time 602, the controller 12 gives a command to the bypass relay 36 to close the bypass relay 36. After a fixed period of 13 ms has elapsed, the controller 12 commands the inverter 24 to turn off at the second point in time 604. Next, the inverter relay 38 receives a command to open at the subsequent zero-crossing point 606 of the output voltage waveform. The first coexistence duration 610 shown in the figure indicates the duration that starts when the bypass relay 36 is latched and ends when the controller 12 commands the inverter relay 38 to open. The amount of time during which this first coexistence operation 610 occurs depends on the actual closing time of the bypass relay 36, which can vary between different relay embodiments. During this coexistence duration 610, both the inverter 24 and the commercial power supply are connected to the load 110, and as a result, the current 120 is fed back to the commercial power supply. The resulting current 120 is related to the difference between the connected load 110 and the output voltage of the inverter 24 and the commercial power supply voltage at the input section 101. This current 120 may cause the result of damaging the bypass relay 36 and / or stressing the components of the inverter 24 or other components in the UPS. The scenario shown in Figure 6 for the second condition is similar to the operation of a typical UPS. In the embodiments described herein, the UPS operation for detecting the first condition improves the transition time from the online mode to the bypass mode, either in relation to the second condition or alone.

[0051] FIG. 7 shows a timing sequence 700 in the first UPS 100 and the UPS 200 regarding the transition between the online operation mode and the bypass operation mode when the first condition 504 of the method 500 is satisfied. In this timing sequence 700, as shown in FIG. 6, at the first time point 602, the controller 12 gives a command to the bypass relay 36 to close the bypass relay 36. After the controller 12 commands the bypass relay 36 to close, the method 500 starts. After the bypass relay 36 is latched, the current in the sensor 28 begins to increase. Both the second coexistence duration 710 and the detection period 712 start when the bypass relay 36 is latched. The detection period 712 indicates to the controller 12 the length of time for detecting whether the value from the sensor 28 exceeds a predetermined threshold value in the first condition 504 of the method 500. When the first condition 504 of the method 500 is satisfied at the end of the detection period 712, at a time point 704 earlier than the fixed threshold time evaluated by the second condition 508, the controller 12 commands to turn off the inverter 24 in the second action 506 of the method 500. After the controller 12 commands to turn off the inverter 24, the controller 12 then commands to open the inverter relay 38 at the next estimated zero crossing time point 706. As a result of the first condition 504 being satisfied during the detection period 712, the second coexistence duration 710 is shorter than the first coexistence duration 610.

[0052] One or more embodiments have been described above for a UPS device, but it should be understood that these and other embodiments can include a general-purpose power supply in place of or in addition to the UPS device. Other embodiments include using the techniques described herein for other power supply devices. Some embodiments include, but are not limited to, using the techniques described herein for other types of UPSs, including standby UPSs, line-interactive UPSs, standby-online hybrid UPSs, standby-ferro UPSs, delta conversion online UPSs, and offline UPSs. Other embodiments include using the techniques described herein for devices other than relays.

[0053] Although some aspects in at least one embodiment described in this specification have been explained, it will be readily envisioned by those skilled in the art that various modifications, changes, and improvements will occur. Such modifications, changes, and improvements are intended to form part of this disclosure and are intended to be within the spirit and scope of the present disclosure. Therefore, the above description and drawings are merely examples.

Explanation of Reference Numerals

[0054] 12 Controller 14 Rectifier / Power Factor Correction (PFC) Circuit 16 DC-DC Converter 18 Battery 20 Polarized Capacitor 22 DC Bus 24 Inverter 26 Inductor 28 Current Sensor 32 Backfeed Line Relay 34 Backfeed Non-Polar Relay 36 Bypass Relay 38 Inverter Relay 100 First UPS 101 Input Section 102 Second Input Section 103 Neutral Input Section 104 Output Section 105 Neutral Output Section 110 Load 120 Current 200 Second UPS 500 Method 600 Timing Sequence 700 Timing Sequence

Claims

1. In an uninterruptible power supply (UPS), an input unit configured to receive input power, a backup input unit configured to receive backup power from a backup power source, an output unit configured to supply output power to a load from at least one of the input power or the backup power, an inverter connected to the input unit, the backup input unit, and the output unit and configured to supply an inverter output current, a sensor configured to detect a parameter indicating the inverter output current, a bypass relay connected between the input unit and the output unit, an inverter relay connected between the inverter and the output unit, at least one controller connected to the sensor, configured to determine that the bypass relay is closed, configured to turn off the inverter based on the determination that the bypass relay is closed, and configured to issue an instruction to open the inverter relay after turning off the inverter, the controller; and An uninterruptible power supply comprising the same.

2. The uninterruptible power supply according to claim 1, wherein the at least one controller is configured to determine that the bypass relay is closed based on a parameter indicating the inverter output current.

3. The uninterruptible power supply according to claim 1, wherein the at least one controller is configured to determine that the bypass relay is closed based on a differential value of the inverter output current.

4. The uninterruptible power supply according to claim 1, wherein the at least one controller is connected to the bypass relay, configured to detect that the inverter output current exceeds a threshold value, and configured to determine that the bypass relay is closed based on the detection that the inverter output current exceeds the threshold value. The uninterruptible power supply.

5. The uninterruptible power supply according to claim 1, wherein the at least one controller is configured to determine that the bypass relay is closed based on the elapse of a predetermined period of time after instructing the bypass relay to close.

6. In the uninterruptible power supply device according to claim 1, the UPS includes a power factor correction (PFC) circuit, and the sensor is configured to detect the current at the input of the PFC circuit as a parameter indicating the inverter output current. Uninterruptible power supply device.

7. In the uninterruptible power supply device according to claim 1, further comprising a second input unit configured to receive a second input power and supply the second input power to the bypass relay. Uninterruptible power supply device.

8. In the uninterruptible power supply device according to claim 1, the sensor is configured to detect the inverter output current at the output of the inverter. Uninterruptible power supply device.

9. In the uninterruptible power supply device according to claim 1, the sensor is configured to detect the current at the input of the inverter as a parameter indicating the inverter output current. Uninterruptible power supply device.

10. In a method of operating an uninterruptible power supply (UPS), Receiving input power at an input unit; Receiving backup power from a backup power source; Supplying output power to a load from at least one of the input power or the backup power; Detecting a parameter indicating an inverter output current from an inverter of the UPS; Determining that the bypass relay is closed; Turning off the inverter included based on the determination that the bypass relay is closed; After turning off the inverter, instructing to open an inverter relay; A method comprising:

11. The method according to claim 10, further comprising determining that the bypass relay is closed based on a parameter indicating the inverter output current.

12. The method according to claim 10, further Detecting that a parameter indicating the inverter output current exceeds a threshold in response to instructing the bypass relay to close; and Determining that the bypass relay is closed based on the detection that the inverter output current exceeds the threshold; A method comprising:

13. The method according to claim 10, further comprising determining that the bypass relay is closed based on the elapse of a predetermined period of time.

14. An input unit configured to receive input power, a backup input unit configured to receive backup power from a backup power source, an output unit configured to supply output power to a load from at least one of the input power or the backup power, an inverter connected to the input unit, the backup input unit, and the output unit, a sensor configured to detect a parameter related to an inverter output current of the inverter, a bypass relay connected between the input unit and the output unit and configured to supply output power, an inverter relay connected between the inverter and the output unit, and at least one controller connected to the sensor, a persistent computer-readable medium storing a sequence of computer-executable instructions for controlling an uninterruptible power supply (UPS) including: the sequence of computer-executable instructions causes the at least one controller to detect a parameter related to the inverter output current, determine that the bypass relay is closed, turn off the inverter based on the determination that the bypass relay is closed, and open the inverter relay after turning off the inverter is commanded. Persistent computer-readable medium.

15. The persistent computer-readable medium according to claim 14, wherein the sequence of computer-executable instructions causes the at least one controller to determine that the bypass relay is closed based on a parameter related to the inverter output current. Persistent computer-readable medium.

16. In the persistent computer-readable medium according to claim 14, the at least one controller is connected to the bypass relay, and the sequence of computer-executable instructions causes the at least one controller to detect that a parameter indicating the inverter output current exceeds a threshold in response to a command to close the bypass relay, and determine that the bypass relay is closed based on the detection that the inverter output current exceeds the threshold is commanded. Persistent computer-readable medium.

17. In the persistent computer-readable medium according to claim 14, the UPS includes a power factor correction (PFC) circuit, and the sequence of computer-executable instructions instructs the at least one controller to detect a current at an input of the PFC circuit as a parameter related to the inverter output current. Persistent computer-readable medium.

18. In the persistent computer-readable medium according to claim 16, the sequence of computer-executable instructions instructs the at least one controller to determine that the bypass relay has closed based on the elapse of a predetermined period of time. Persistent computer-readable medium.

19. In the persistent computer-readable medium according to claim 14, the sequence of computer-executable instructions instructs the at least one controller to detect the inverter output current at an output of the inverter. Persistent computer-readable medium.

20. In the persistent computer-readable medium according to claim 14, the sequence of computer-executable instructions instructs the at least one controller to detect a current at an input of the inverter as a parameter related to the inverter output current. Persistent computer-readable medium.

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