Power device and method of operating the same and non-transitory computer readable medium

Abstract

The present invention provides an electric power device, a method of operating the same, and a non-transitory computer readable medium. The electric power device includes an input configured to receive input power, a backup input configured to receive backup power from a backup power source, an output configured to provide output power to a load from at least one of the input power and the backup power, an inverter coupled to the input, the backup input, and the output, the inverter configured to provide inverter output current, a sensor configured to detect a parameter indicative of the inverter output current, a relay coupled between the input and the output, and a controller coupled to the sensor, the at least one controller configured to determine that the relay has closed, and to shut down the inverter in accordance with the determination that the relay has closed. The present invention is capable of overcoming at least one drawback of the prior art.

Description

[0001] Cross Reference to Related Applications

[0002] 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,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present invention relates generally to systems and methods for controlling a power device, i.e., an uninterruptible power supply (UPS). BACKGROUND

[0004] It is known to use power devices, e.g., uninterruptible power supplies, to provide stable, uninterruptible power to sensitive and / or critical loads, e.g., computer systems and other data processing systems. Known uninterruptible power supplies include on-line UPSs, off-line UPSs, line interactive UPSs, and other devices. On-line UPSs provide conditioned ac power and backup ac power in the event of a disruption in the main ac power source. Off-line UPSs generally do not provide regulation of the input ac power, but do provide backup ac power in the event of a disruption in the main ac power source. Line interactive UPSs are similar to off-line UPSs in that they switch to battery power in the event of a power outage, but generally also include a multi-tapped transformer for regulating the output voltage provided by the UPS. SUMMARY

[0005] According to one embodiment, a power device, i.e., an uninterruptible power supply (UPS), includes an input configured to receive input power; a backup input configured to receive backup power from a backup power source; an output configured to provide output power to a load from at least one of the input power and the backup power; an inverter coupled to the input, the backup input, and the output, and the inverter is configured to provide inverter output current; a sensor configured to detect a parameter indicative of the inverter output current; a relay coupled between the input and the output; and at least one controller coupled to the sensor, and the at least one controller is configured to: determine that the relay has closed; and shut down the inverter in accordance with the determination that the relay has closed.

[0006] In one embodiment, the at least one controller is configured to determine that the relay has closed in accordance with the parameter indicative of the inverter output current.

[0007] In another embodiment, the at least one controller is configured to determine that the relay has closed based on a derivative value of the inverter output current.

[0008] In one embodiment, the at least one controller is coupled to the inverter, and the at least one controller is configured to detect that the inverter output current exceeds a threshold value, and determine that the relay has closed based on the detection that the inverter output current exceeds the threshold value.

[0009] In another embodiment, the at least one controller is configured to determine that the relay has closed based on an elapse of a predetermined time period after an indication that the relay has closed.

[0010] In one embodiment, the power device includes a power factor correction circuit, and the sensor is configured to detect a current at an input of the power factor correction circuit as the parameter indicative of the inverter output current.

[0011] In another embodiment, the power device further includes a second input configured to receive second input power, and provide the second input power to the relay.

[0012] In one embodiment, the sensor is configured to detect the inverter output current at an output of the inverter.

[0013] In another embodiment, the sensor is configured to detect a current at an input of the inverter as the parameter indicative of the inverter output current.

[0014] According to one embodiment, a method for operating a power device includes receiving input power at an input, receiving backup power from a backup power source, providing output power to a load from at least one of the input power and the backup power, detecting a parameter indicative of an inverter output current from an inverter of the power device, determining that a relay has closed, and shutting down the inverter based on the determination that the relay has closed.

[0015] In one embodiment, the method further includes determining that the relay has closed based on the parameter indicative of the inverter output current.

[0016] In another embodiment, the method further includes, in response to an indication that the relay has closed, detecting that the parameter indicative of the inverter output current exceeds a threshold value, and determining that the relay has closed based on the detection that the inverter output current exceeds the threshold value.

[0017] In one embodiment, the determination that the relay has closed is based on an elapse of a predetermined time period.

[0018] According to one embodiment, a non-transitory computer readable medium having stored thereon sequences of computer executable instructions for controlling a power device, the power device comprising: an input configured to receive input power; an auxiliary input configured to receive auxiliary power from an auxiliary power source; an output configured to provide output power to a load from at least one of the input power and the auxiliary power; an inverter coupled to the input, the auxiliary input, and the output; a sensor configured to detect a parameter related to an inverter output current of the inverter; a relay coupled between the input and the output and configured to provide output power; and at least one controller coupled to the sensor, the sequences of computer executable instructions instructing the at least one controller to: detect the parameter related to the inverter output current; determine that the relay has closed; and shut down the inverter based on the determination that the relay has closed.

[0019] In one embodiment, the sequences of computer executable instructions instruct the at least one controller to determine that the relay has closed based on the parameter related to the inverter output current.

[0020] In another embodiment, the at least one controller is coupled to the relay, and the sequences of computer executable instructions instruct the at least one controller to: in response to an indication that the relay is closed, detect that the parameter related to the inverter output current exceeds a threshold; and determine that the relay has closed based on the detection that the inverter output current exceeds the threshold.

[0021] In one embodiment, the power device comprises a power factor correction circuit, and the sequences of computer executable instructions instruct the at least one controller to detect a current at an input of the power factor correction circuit as the parameter related to the inverter output current.

[0022] In another embodiment, the sequences of computer executable instructions instruct the at least one controller to determine that the relay has closed based on an elapse of a predetermined time period.

[0023] In one embodiment, the sequences of computer executable instructions instruct the at least one controller to detect the inverter output current at an output of the inverter.

[0024] In another embodiment, the computer-executable instruction sequences instruct the at least one controller to detect a current at an input of the inverter as the parameter related to the inverter output current. BRIEF DESCRIPTION OF DRAWINGS

[0025] Various aspects of at least one embodiment are discussed in the following detailed description with reference to the drawing figures in which like numerals represent similar components as understood by persons skilled in the art. The following detailed description does not intentionally repeat matter

[0026] IN THE DRAWINGS

[0027] Figure 1 is a block diagram of an online UPS in an online mode in accordance with aspects described herein.

[0028] Figure 2 is a block diagram of an online UPS transitioning to a green / bypass mode in accordance with aspects described herein.

[0029] Figure 3 is a block diagram of an online UPS in an online mode in accordance with aspects described herein.

[0030] Figure 4 is a block diagram of an online UPS transitioning to a green / bypass mode in accordance with aspects described herein.

[0031] Figure 5 is a logic flow diagram showing control of operation of an inverter of a UPS in accordance with aspects described herein.

[0032] Figure 6 is a logic flow diagram showing a transition from an online mode to a green / bypass mode in accordance with aspects described herein without Figure 5 is a timing diagram showing a transition from an online mode to a green / bypass mode in accordance with aspects described herein.

[0033] Figure 7 is a timing diagram showing a transition from an online mode to a green / bypass mode in accordance with aspects described herein. DETAILED DESCRIPTION

[0034] Examples of the methods and systems discussed herein are not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The methods and systems can be implemented in other embodiments and can be practiced or carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements, and features discussed in connection with any one or more examples are not excluded from the scope of similar acts, components, elements, and features in any other example.

[0035] In addition, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular can also include implementation having one or more of the pluralities, and any references in plural to any implementation, component, element or act herein can also include implementation having one or more of the pluralities. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof as well as other items. References to "or" can be construed as inclusive so that any terms described using "or" can indicate any of a single, one or more, and all of the described terms. In addition, in the event of inconsistent usages of terms throughout this document, the usages that are

[0036] In existing power devices, i.e., Uninterruptible Power Supply (UPS) systems, a parallel operation of an inverter and utility power can occur briefly during the transition from on-line mode operation to bypass mode operation after the bypass relay is closed. After the bypass relay is closed, a conductive path can be formed between the inverter, inverter relay, bypass relay, and utility line connected to the bypass relay. During the time that the utility line is connected in parallel with the inverter, the current in the components of the UPS can continue to increase until the inverter is turned off. This can put stress on the components of the UPS and can result in the need for more robust, more expensive components to handle the increased current. For the relays transitioning from the on-line mode to the bypass mode, the increased current can cause the relays to fuse and permanently damage if not controlled properly. Also, during this parallel, the inverter can backfeed into the utility line.

[0037] At least some embodiments of the present disclosure provide methods, power devices (Uninterruptible Power Supplies), and non-transitory computer readable media for adaptively adjusting the timing of turning off the output of an inverter of a power device (Uninterruptible Power Supply) after a bypass relay is reached (closed). At least some embodiments disclosed herein improve existing UPS systems by enabling existing UPS systems to handle inconsistent relay timing and unit-to-unit timing variations without additional hardware circuitry while reducing the time during which parallel operation occurs.

[0038] Reference will now be made to Figure 1 An embodiment of an Uninterruptible Power Supply system 100 according to the present disclosure is described, Figure 1A functional block diagram of a first uninterruptible power supply (UPS) 100 is shown. The UPS 100 is an online UPS and includes a controller 12, a rectifier / power factor correction (PFC) circuit 14, a DC-DC converter 16, a battery 18, a polarization capacitor 20, a DC bus 22, an inverter 24, an inductor 26, a current sensor 28, a backfeed line relay 32, a backfeed neutral relay 34, a bypass relay 36, an inverter relay 38, an input 101, a neutral input 103, an output 104, and a neutral output 105. The UPS 100 supplies power to a load 110 based on input power received at the input 101 and / or power from the battery 18.

[0039] In some embodiments, the inductor 26 is one of a coreless inductor, a ferromagnetic core inductor, and a ferrite core inductor.

[0040] The input 101 is coupled to the reverse feed relay 32, which is coupled to the PFC circuit 14. Each output of the PFC circuit 14 is coupled to the inverter 24. The outputs of the PFC circuit 14 are coupled together through the polarization capacitor 20, with the outputs of the PFC circuit coupled to the anode of the polarization capacitor 20 forming the DC bus 22, which is coupled to the DC-DC converter 16. The DC bus 22 also serves as a backup input that receives backup power from the battery 18 through the DC-DC converter 16. The battery 18 serves as a backup power source. The cathode of the polarization capacitor 20 is coupled to the PFC circuit 14, the inverter 24, and the DC-DC converter 16. An output of the DC-DC converter 16 is coupled to the anode of the battery 18, and another output of the DC-DC converter 16 is coupled to the cathode of the battery 18 and to ground. The inverter 24 has an output coupled to the inductor 26 and another output coupled to the neutral output 105. The neutral output 105 is coupled to the PFC circuit 14, the inverter 24, the reverse feed neutral relay 34, and the load 110. The inductor 26 is coupled to the current sensor 28, which is coupled to the invert relay 38. The invert relay 38 is coupled to the bypass relay 36 and the output 104, which is coupled to the load 110. The load 110 is coupled between the output 104 and the neutral output 105. The bypass relay 36 is coupled to the input 101 and the reverse feed relay 32.

[0041] In Figure 1 the controller 12 is shown coupled to the PFC circuit 14, the DC-DC converter 16, the inverter 24, the current sensor 28, the reverse feed relay 32, the reverse feed neutral relay 34, the bypass relay 36, and the invert relay 38. Each solid line connected to the controller 12 represents a communication path that can send signals from or receive signals at the controller 12 from one or more internal components of the UPS 100. As Figure 1 each relay 32, 34, 36, 38 is configured to switch between an open position and a closed position at the direction of the controller 12. In the closed position, a conductive path is formed between a first terminal and a second terminal of a given relay. For example, when the bypass relay 36 is open (as shown in FIG. 1), a conductive path is formed between the input 101 and the output 104. When the bypass relay 36 is closed, the conductive path between the input 101 and the output 104 is broken, and a conductive path is formed between the output 104 and the neutral output 105. Figure 1As shown, no current is conducted between the input 101 and the output 104 within the bypass relay 36. Conversely, when the bypass relay 36 is closed, current is conducted at the relay connection of the input 101 and at the relay connection of the output 104, and power is present at the input 101 when the load 110 is coupled between the output 104 and the neutral output 105.

[0042] As shown in FIG. 1, the UPS 100 is a single-phase UPS having a dual conversion (AC to DC, DC to AC) topology. In other embodiments, the UPS 100 can be a multi-phase UPS, such as a three-phase UPS. The UPS 1 is shown in FIG. 1 operating in an online mode, in which the UPS 100 is configured to provide output power to the load 110 using the inverter 24. As shown in FIG. 1, the reverse feed line relay 32 is configured in a closed position to connect the input 101 with the PFC circuit 14. The bypass relay 36 is configured in an open position. The reverse feed neutral relay 34 and the inverter relay 38 are shown in the closed position. When the reverse feed line relay 32, the reverse feed neutral relay 34, the bypass relay 36, and the inverter relay 38 are configured in these positions, the UPS 100 is configured to operate in an online mode of operation. To enter bypass mode, a higher efficiency mode of operation, the controller 12 activates (closes) the bypass relay 36 and turns off the inverter 24. Figure 1 Figure 1 Figure 1

[0043] ​​​In some embodiments, one or more of the reverse feed line relay 32, the reverse feed neutral relay 34, the bypass relay 36, and the inverter relay 38 are electromechanical relays (EMRs). Electromechanical relays are devices that convert magnetic flux into mechanical force, which is typically used to operate electrical contacts within the relay using a spring. On the other hand, solid state relays (SSRs) lack moving parts and cannot achieve their functionality through semiconductors. Due to the mechanical nature of EMRs, the time it takes for the internal switch to move away from one contact and land on the other can vary depending on the age of the EMR, the type of EMR, the spring strength, contact wear, coil damage, temperature, and other factors. As a result, it is not possible to predict exactly how long it will take for the internal switch of an EMR to move from one position to another when the control instructs the EMR to close. Therefore, if the controller 12 only uses a fixed time to interrupt the output of the inverter 24 after instructing the bypass relay 36 to close, the inverter 24 can provide power to the input 101 through the bypass relay 36.

[0044] Figure 2 A functional block diagram showing the UPS 100 transitioning to bypass mode operation. Figure 2 Unlike Figure 1 The difference between the two is that the bypass relay 36 is closed and there is current 120 between the inverter relay 38 and the bypass relay 36. During the transition from the online mode operation to the bypass mode operation 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. As a result, the input AC power is provided directly to the output 104 through the bypass relay 36. After instructing the inverter 24 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 reverse feed line relay 32 and the reverse feed neutral relay 34 to open to prevent reverse feed to the utility grid.

[0045] In an ideal situation, the optimal transition from the online mode to the bypass mode would cause the inverter 24 to stop at the same time the bypass relay 36 reaches (closes). However, if the controller 12 stops the inverter 24 too early (before the bypass relay 36 reaches), the load 110 can drop and / or the load input capacitor can be depleted, resulting in a large inrush current when the bypass relay 36 reaches. If the controller 12 stops the inverter 24 too late (a significant amount of time after the bypass relay 36 reaches), the parallel of utility power and inverter power can cause the inverter 24 to source or sink large currents, which can cause stress or damage to internal components of the UPS 100. In this case, the inverter 24 can be attempting to supply power to the connected utility line (back-feeding). Figure 3 and Figure 4 A second Uninterruptible Power Supply (UPS) 200 is shown, which is substantially identical to the first UPS 100, except that the second UPS 200 includes a second input 102. Common elements in the UPS 100 and the UPS 200 are labeled with the same reference numerals. The second input 102 is coupled to the bypass relay 36. As shown in Figure 3 and Figure 4 The second input 102 can receive input power and is separate from the input 101, as shown. In some embodiments, the input 101 and the second input 102 are designed to receive power from different power sources to provide additional margin. In one embodiment, one of the input 101 and the second input 102 receives power from a utility grid and the other receives power from an alternative energy source. In some embodiments, the alternative energy source is one or more of solar, wind, and hydroelectric power.

[0046] In each of Figure 1 , Figure 2 , Figure 3 and Figure 4 some embodiments include an optional capacitor connected between the neutral output 105 and a wire connecting the current sensor 28 and the inverter relay 38.

[0047] As Figure 1 and Figure 2As shown, the current sensor 28 is coupled between the inductor 26 and the inverter relay 38 to measure an inverter output current of the inverter 24 as a parameter indicative of the current output by the inverter 24. In some embodiments, the UPS 100 or the UPS 200 includes one or more current sensors, including the current sensor 28. Each of the one or more current sensors can be coupled at a different location in the UPS 100 or the UPS 200. In one embodiment, in addition to or instead of the current sensor 28 coupled between the inductor 26 and the inverter relay 38, the current sensor is coupled to the direct current (DC) bus 22 to measure a current received by the input of the inverter 24 as a parameter indicative of the output current of the inverter 24. In some embodiments, a scaling factor is applied to the received current to estimate the output current of the inverter 24. Other scaling factors can be similarly applied to other locations of one or more current sensors. In another embodiment, the current sensor 28 is coupled to the input of the PFC circuit 14 that is connected to both the PFC circuit 14 and the reverse feed relay 32. A scaling factor or a separate threshold can be compared to the value of the current sensor 28 at the input of the PFC circuit 14 to determine whether the bypass relay 36 has been closed. In some embodiments, multiple of the one or more sensors are used, including the current sensor 28, and the parameter indicative of the output current is a weighted average of the current measured by each of the current sensors.

[0048] In Figures 1 to 4 , straight lines that cross and intersect each other are not electrically connected. A solid circle that overlaps a straight line indicates that the line under the circle is electrically connected. In each of the reverse feed relays 32, the reverse feed neutral relay 34, the bypass relay 36, and the inverter relay 38, there are three electrical contacts represented by circles. A straight line connecting one of the circles and a component outside of the respective relay indicates a connection. For example, in Figure 1 , the input 101 is connected to the PFC circuit 14 through the reverse feed relay 32. The discussion of the operation of the first UPS 100 continues below. The second UPS 200 operates in substantially the same manner except for having an additional input 102 for receiving an input power source, the purpose here being to apply to the first UPS 100 in all respects.

[0049] The operation of the first UPS 100 will now be described in more detail with reference to the method 500, which is shown in Figure 5The method 500 is depicted as a logical flow diagram. The method 500 includes at least three actions 502, 506, and 510, and two conditions 504 and 508. In some embodiments, the controller 12 performs each action and condition in the method 500. Certain embodiments implement the method 500 as a firmware algorithm, stored as program instructions in internal memory of the UPS 100.

[0050] In the method 500, converting the inverter output current to an ADC measurement with the current sensor 28 allows the controller 12 to detect a rise in the ADC measurement, indicating the landing of the bypass relay 36 and the start of backfeeding of current 120.

[0051] In the first action 502 of the method 500, the controller 12 instructs the UPS 100 to transition from the online mode to the bypass mode. To transition to the bypass mode, the controller 12 instructs the bypass relay 36 to close. After instructing the bypass relay 36 to close, the controller 12 begins monitoring the current detected by the current sensor 28. In some embodiments, the controller 12 waits a predetermined time before monitoring the current with the current sensor 28. In one embodiment, the predetermined time is in the range of about 0.1 milliseconds (ms) to about 5 ms. In another embodiment, the predetermined time is in the range of about 0.01 ms to about 10 ms. In one embodiment, the predetermined time is in the range of about 0.001 ms to about 50 ms.

[0052] The controller 12 then compares the most recent current value detected by the current sensor 28 to a predetermined current value as a first condition 504. In some embodiments, the predetermined value is about 125% of the nominal current output by the inverter 24. In certain embodiments, the predetermined value is a current threshold adjusted for a particular load 110. In one embodiment, the load consumed by the server rack is about 5.5 kilowatts (kW), the maximum capacity of the inverter 24 is about 30 amperes (A), and the current threshold is set to about 80% of the maximum capacity, or about 24 A. In another embodiment, the current threshold is in a range. According to certain aspects, the range is about 3 times to about 5 times the RMS value. For example, if the RMS value is about 30 A, then a range of about 100 A is reasonable. In some examples, the range is about 30 A to about 100 A. In other embodiments, the range is about 24 A to about 30 A. In some embodiments, the range is about 10 A to about 50 A. If the current value detected by the current sensor 28 exceeds the predetermined value (YES), then the first condition 504 is satisfied and the method 500 proceeds to a second action 506. If the current value detected by the current sensor 28 does not exceed the predetermined value (NO), then the method 500 continues to evaluate a second condition 508. In some embodiments, the first condition 504 compares the increase in current per unit time detected by the current sensor 28 to a threshold value representing a predetermined derivative value of current.

[0053] In Figures 1 to 4 In the illustrated embodiment, the current sensor 28 is electrically coupled to the output of the inverter 24. The output of the inverter is coupled to the inductor 26, which is coupled to the current sensor 28, which is coupled between the inductor 26 and the inverter relay 38 to measure the output current of the inverter 224. In other embodiments, the current sensor 28 or an additional sensor can be coupled to the input of the inverter 24. For example, in some embodiments, the current sensor 28 is coupled to the DC bus 22. Other locations for current (or voltage) sensors within the UPS 100 are included in the embodiments disclosed herein. Although the particular value indicative of the presence of the current 120 monitored by the current sensor 28 can vary depending on the location of the current sensor 28 within the UPS 100, the actions and conditions of the method 500 are the same for each location. More specifically, in different embodiments, any sensor that determines a parameter related to the output current of the inverter can be used in addition to or instead of the current sensor 28 to detect an increase in output current after the UPS 100 switches to bypass mode.

[0054] The second condition 508 compares the time elapsed since the controller 12 instructed the UPS 100 to close the bypass relay 36 in the first action 502 to a predetermined threshold value. The threshold value represents the maximum fixed period of time that can elapse since the bypass relay 36 was instructed to close. According to certain aspects, the predetermined threshold value is approximately 1 ms to approximately 2 ms. In some embodiments, the predetermined threshold value is 10 ms. In certain embodiments, the threshold value is 13 ms. In some embodiments, the threshold value is a value between 10 ms and 13 ms. If the current time (as of the second condition 508 currently being evaluated) exceeds the predetermined threshold value, the second condition 508 is satisfied (YES), and the method 500 proceeds to the third action 510. If the current time does not exceed the predetermined threshold value, the second condition 508 is not satisfied (NO), and the method 500 returns to evaluating the first condition 504. Certain embodiments determine the time to interrupt the inverter 24 after the controller 12 commands the bypass relay 36 to close based on an average relay closing time (for the type of relay used as the bypass relay 36) plus a margin, using the fixed relay time as the predetermined threshold value.

[0055] In some embodiments, when the second condition is not satisfied (NO), the method 500 returns to evaluating the second condition 508. In an embodiment, the method 500 includes one or more evaluations of the first condition 504 before proceeding to evaluate the second condition 508 if the first condition 504 is not satisfied. Some examples include a predetermined wait period in the first condition 504 before comparing the parameter indicative of the current of the inverter 24 to the predetermined threshold value, then proceeding to evaluate the second condition 508.

[0056] The time to interrupt the inverter 24 after commanding the bypass relay 36 to close should not be less than the fly time of the relay, or else it can result in a large inrush current from utility power to the load 110, which can result in relay damage and / or damage to other UPS components.

[0057] In some embodiments, the method 500 results in one of two possible outcomes. In one outcome, the first condition 504 is satisfied and the controller 12 instructs the inverter 24 to shut down early (before a predetermined time threshold has been exceeded). In another outcome, the second condition 508 is satisfied and the controller 12 instructs the inverter 24 to shut down due to the expiration of the predetermined time period. Certain embodiments include additional conditions or actions. In one embodiment, a third condition 505 (not shown) can be evaluated between the first condition 504 and the second condition 508, the third condition 505 evaluating whether the inverter current is different from a value checked at the first condition 504. In such an embodiment, the first condition 504 evaluates the current for a first current value and if the current value is not exceeded, a second, higher current value is evaluated in the third condition 505. If the current in the third condition 505 is exceeded, the method 500 proceeds to the second action 506, and if not, the method 500 proceeds to the second condition 508.

[0058] Figure 6 A timing sequence 600 is shown for the first UPS 100 and the second UPS 200 for the transition between the online mode and the bypass mode when the second condition 508 in the method 500 is satisfied. In the timing sequence 600 at a first time point 602, the controller 12 provides a command to the bypass relay 36 to instruct the bypass relay 36 to close. After a fixed time period of 13 ms, the controller 12 commands the inverter 24 to shut down at a second time point 604. The inverter relay 38 is then commanded to open at the next zero crossing point 606 of the output voltage waveform. The first parallel duration 610 shown shows the duration of time from when the bypass relay 36 has landed to when the controller 12 instructs the inverter relay 38 to open. The amount of time at which the first parallel duration 610 occurs depends on the actual closing time of the bypass relay 36, which can vary between different relay samples. During the first parallel duration 610, both the inverter 24 and utility power are connected to the load 110, which can result in current 120 being fed back to the utility power. The resulting current 120 is related to the difference between the connected load 110 and the output voltage of the inverter 24 and the voltage of the utility power at the input 101. The current 120 can result in damage to the bypass relay 36 and / or stress to components of the inverter 24 or any other components of the UPS 100. Figure 6The scenario described for the second case is similar to typical UPS operation. In the embodiments disclosed herein, the UPS's operation for detecting the first condition (whether together with or alone from the second condition) provides an improvement in the transition time from the online mode to the bypass mode.

[0059] Figure 7 This displays the timing 700 of the transition between the online mode operation and the bypass mode operation of the first UPS 100 and the second UPS 200 when the first condition 504 of the method 500 is satisfied. In the timing, as shown... Figure 6 As shown, at a first time point 602, the controller 12 provides a command to the bypass relay 36, instructing the bypass relay 36 to close. After the controller 12 instructs the bypass relay 36 to close, method 500 begins. Once the bypass relay 36 has arrived, the current in the current sensor 28 begins to rise. The second parallel duration 710 and the detection period 712 both begin at the point where the bypass relay 36 has arrived. The detection period 712 indicates the length of time for which the controller 12 detects that the value from the current sensor 28 has exceeded a predetermined threshold in the first condition 504 of method 500. At the end of the detection period 712, the first condition 504 of method 500 is satisfied, and the controller 12, in the second action 506 of method 500, instructs the inverter 24 to shut down at a time point 704 earlier than the fixed threshold time evaluated in the second condition 508. Once the controller 12 instructs the inverter 24 to shut down, the controller 12 instructs the inverter relay 38 to open at the next estimated zero-crossing point 706. As a result of satisfying the first condition 504 during the detection period 712, the second parallel duration 710 is shorter than the first parallel duration 610.

[0060] While one or more of the embodiments described above relate to UPS systems, it should be understood that these and other embodiments may replace or include general-purpose power supplies in addition to UPS systems. Other embodiments include the use of the techniques described herein in other power systems. Some embodiments include the use of the techniques described herein in other types of UPSs, including but not limited to standby UPSs, line-interactive UPSs, standby on-line hybrid UPSs, standby-ferro UPSs, delta conversion on-line UPSs, and offline UPSs. Other embodiments include the use of the techniques described herein in conjunction with devices other than relays.

[0061] Having thus described several aspects of at least one embodiment of the application, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the application. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. An electric power device, characterized by: The power device includes: an input configured to receive input power; a backup input configured to receive backup power from a backup power source; an output configured to provide output power to a load from at least one of the input power and the backup power; an inverter coupled to the input, the backup input, and the output, and the inverter is configured to provide inverter output current; a sensor configured to detect a parameter indicative of the inverter output current; a bypass relay coupled between the input and the output; and at least one controller coupled to the sensor, and the at least one controller is configured to: determine that the bypass relay has closed; and turn off the inverter in accordance with the determination that the bypass relay has closed, wherein the at least one controller is configured to determine that the bypass relay has closed in accordance with the parameter indicative of the inverter output current.

2. The power device of claim 1, wherein: The at least one controller is configured to determine that the bypass relay has closed in accordance with a derivative value of the inverter output current.

3. The power device of claim 1, wherein: The at least one controller is coupled to the bypass relay, and the at least one controller is configured to: detect that the inverter output current exceeds a threshold; and determine that the bypass relay has closed in accordance with the detection that the inverter output current exceeds the threshold.

4. The power device of claim 1, wherein: The at least one controller is configured to determine that the bypass relay has closed in accordance with the elapse of a predetermined time period after the indication that the bypass relay has closed.

5. The power device of claim 1, wherein: The power device includes a power factor correction circuit, and the sensor is configured to detect a current at an input of the power factor correction circuit as the parameter indicative of the inverter output current.

6. The power device of claim 1, wherein: The power device further includes a second input configured to receive second input power, and the second input power is provided to the bypass relay.

7. The power device of claim 1, wherein: The sensor is configured to detect the inverter output current at an output of the inverter.

8. The power device of claim 1, wherein: The sensor is configured to detect a current at an input of the inverter as the parameter indicative of the inverter output current.

9. A method of operating an electric power device, characterized by: The method includes the steps of: receiving input power at an input; receiving backup power from a backup power source; providing output power to a load from at least one of the input power and the backup power; detecting a parameter indicative of inverter output current from an inverter of the power device; determining that a bypass relay has closed; and turning off the inverter in accordance with the determination that the bypass relay has closed, wherein the bypass relay is determined to have closed in accordance with the parameter indicative of the inverter output current. The method further includes:

10. The method of claim 9, wherein: detecting that the parameter indicative of the inverter output current exceeds a threshold in response to the indication that the bypass relay has closed; and determining that the bypass relay has closed in accordance with the detection that the inverter output current exceeds the threshold. The method further includes:

11. The method of claim 9, wherein: determining that the bypass relay has closed in accordance with the elapse of a predetermined time period. The power device includes a power factor correction circuit, and the sensor is configured to detect a current at an input of the power factor correction circuit as the parameter indicative of the inverter output current. The power device further includes a second input configured to receive second input power, and the second input power is provided to the bypass relay. The sensor is configured to detect the inverter output current at an output of the inverter. The sensor is configured to detect a current at an input of the inverter as the parameter indicative of the inverter output current. The method includes the steps of: receiving input power at an input; receiving backup power from a backup power source; providing output power to a load from at least one of the input power and the backup power; detecting a parameter indicative of inverter output current from an inverter of the power device; determining that a bypass relay has closed; and turning off the inverter in accordance with the determination that the bypass relay has closed, wherein the bypass relay is determined to have closed in accordance with the parameter indicative of the inverter output current. The method further includes: detecting that the parameter indicative of the inverter output current exceeds a threshold in response to the indication that the bypass relay has closed; and determining that the bypass relay has closed in accordance with the detection that the inverter output current exceeds the threshold. The method further includes: determining that the bypass relay has closed in accordance with the elapse of a predetermined time period.

12. A non-transitory computer readable medium having stored thereon sequences of computer executable instructions for controlling a power device, the power device comprising: an input configured to receive input power; a backup input configured to receive backup power from a backup power source; an output configured to provide output power to a load from at least one of the input power and the backup power; an inverter coupled to the input, the backup input, and the output; a sensor configured to detect a parameter related to an inverter output current of the inverter; a bypass relay coupled between the input and the output and configured to provide output power; and at least one controller coupled to the sensor, the sequences of computer executable instructions directing the at least one controller to perform operations comprising: detecting the parameter related to the inverter output current; determining that the bypass relay has closed; and shutting down the inverter in accordance with the determination that the bypass relay has closed, wherein the determination that the bypass relay has closed is in accordance with the parameter related to the inverter output current. the at least one controller is coupled to the bypass relay, and the sequences of computer executable instructions direct the at least one controller to perform operations comprising:

13. The non-transitory computer-readable medium of claim 12, wherein: detecting that the parameter related to the inverter output current exceeds a threshold in response to an indication that the bypass relay is closed; and determining that the bypass relay has closed in accordance with the detection that the inverter output current exceeds the threshold. the power device comprises a power factor correction circuit, and the sequences of computer executable instructions direct the at least one controller to detect a current at an input of the power factor correction circuit as the parameter related to the inverter output current.

14. The non-transitory computer-readable medium of claim 12, wherein: the sequences of computer executable instructions direct the at least one controller to perform operations comprising:

15. The non-transitory computer-readable medium of claim 13, wherein: determining that the bypass relay has closed in accordance with an expiration of a predetermined time period. the sequences of computer executable instructions direct the at least one controller to detect the inverter output current at an output of the inverter.

16. The non-transitory computer-readable medium of claim 12, wherein: the sequences of computer executable instructions direct the at least one controller to detect a current at an input of the inverter as the parameter related to the inverter output current.

17. The non-transitory computer-readable medium of claim 12, wherein: ​

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