Abstract:
An uninterruptible power supply (UPS) includes a frame, at least one AC input supported by the frame and configured to be coupled to at least one external power source and at least one AC output supported by the frame and configured to be coupled to at least one external load. The UPS also includes a power conversion circuit supported by the frame and having an output coupled to the at least one AC output, the power conversion circuit configured to selectively provide power from first and second power sources. The UPS further includes first and second static switches supported by the frame and configured to couple and decouple the at least one AC input to and from the at least one AC output and a control circuit supported by the frame and configured to cooperatively control the power conversion circuit and the first and second static switches.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/644,936, filed on Oct. 4, 2012, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The inventive subject matter relates to power conversion apparatus and methods and, more particularly, to uninterruptible power supply (UPS) apparatus and methods. 
       BACKGROUND 
       [0003]    UPS systems are commonly used in installations such as data centers, medical centers and industrial facilities to provide backup power to maintain operation in event of failure of the primary utility supply. These UPS systems often have an “on-line” configuration including a rectifier and inverter coupled by a DC link that is also coupled to an auxiliary power source, such as a battery, fuel cell or other energy storage device. Other configurations, such as standby and line-interactive configurations, may also be used. UPS systems may have a modular structure including two or more UPS modules, each of which may include, for example, a rectifier, an inverter and a DC/DC converter for interfacing to a battery or other DC power source. The modules commonly are designed to operate in parallel to provide scalable power capacity, e.g., the modules may be coupled in common to an AC source, a DC source (e.g., a battery) and/or a load. 
         [0004]    Power supply systems using UPSs, such as those used for data center applications, may be configured in a variety of different redundant configurations to increase reliability and availability. Various redundant UPS arrangements are described, for example, in U.S. Pat. No. 7,265,458 to Edelen et al. 
         [0005]    As shown in  FIG. 1 , UPSs may be used in what is referred to an “A-B” configuration. A UPS  110  may have a first AC input  101  coupled to a power conversion chain including a rectifier  112  and an inverter  114  and a second AC input  102  coupled to a semiconductor static switch  116  that acts as a bypass. The UPS  110  may also include a DC/DC converter  118  coupled to a DC link between the rectifier  112  and the inverter  114  and configured to be coupled to a battery  10 . 
         [0006]    Both of the AC inputs  101 ,  102  of the UPS  110  may be coupled to a first source A. An AC output  103  of the UPS  110  may be coupled to a first static switch  122  of a separate dual switch assembly  120 . A second static switch  124  of the dual switch assembly  120  may be coupled to a second AC source B, which may be another UPS. An output of the dual switch assembly  120  is coupled to a critical load  130 . If the source A fails, the UPS  110  may provide power from its battery. If the UPS  110  fails, the load  130  may be served from the second source B via the second static switch  124  of the dual switch assembly  120 . 
       SUMMARY 
       [0007]    Some embodiments of the inventive subject matter provide an uninterruptible power supply (UPS) including a frame, at least one AC input supported by the frame and configured to be coupled to at least one external power source and at least one AC output supported by the frame and configured to be coupled to at least one external load. The UPS also includes a power conversion circuit supported by the frame and having an output coupled to the at least one AC output, the power conversion circuit configured to selectively provide power from first and second power sources. The UPS further includes first and second static switches supported by the frame and configured to couple and decouple the at least one AC input to and from the at least one AC output and a control circuit supported by the frame and configured to cooperatively control the power conversion circuit and the first and second static switches. 
         [0008]    The power conversion circuit may include a rectifier having an input coupled to the at least one AC input, a DC link coupled to an output of the rectifier and an inverter having an input coupled to the DC link and an output coupled to the at least one AC output. In some embodiments, the control circuit may be configured to concurrently close the first static switch and open the second static switch to support an increased efficiency mode of operation. The frame may include an enclosure containing the power conversion circuit and the first and second static switches. 
         [0009]    Some embodiments provide a system including a plurality of UPSs, each including a frame, at least one AC input supported by the frame and configured to be coupled to at least one external power source, at least one AC output supported by the frame and configured to be coupled to at least one external load, a power conversion circuit supported by the frame and having an output coupled to the at least one AC output, first and second static switches supported by the frame and configured to couple and decouple the at least one AC input to and from the at least one AC output and a control circuit supported by the frame and configured to cooperatively control the power conversion circuit and the first and second static switches. The system further includes first and second AC power sources coupled to respective ones of the first and second static switches of the plurality of UPSs. The plurality of UPSs may include a plurality of first UPSs and the second AC power source may include at least one second UPS. Respective ones of the plurality of UPSs may be coupled to respective loads. 
         [0010]    Further embodiments provide a system including a UPS that includes a frame, at least one AC input supported by the frame and configured to be coupled to at least one external power source, at least one AC output supported by the frame and configured to be coupled to at least one external load, a power conversion circuit supported by the frame and having an output coupled to the at least one AC output, first and second static switches supported by the frame and configured to couple and decouple the at least one AC input to and from the at least one AC output and a control circuit supported by the frame and configured to cooperatively control the power conversion circuit and the first and second static switches. The system further includes first and second loads coupled to respective ones of the first and second static switches. 
         [0011]    In some embodiments, the first static switch may be coupled between an AC power source and the first load and the second static switch may be coupled between the first static switch and the second load. In further embodiments, the first static switch may be coupled between an AC power source and the first load and the second static switch may be coupled between the AC power source and the second load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic diagram illustrating a conventional power distribution system configuration. 
           [0013]      FIG. 2  is a schematic diagram illustrating an uninterruptible power supply (UPS) according to some embodiments of the inventive subject matter. 
           [0014]      FIGS. 3-7  are schematic diagrams illustrating power distribution systems according to various embodiments of the inventive subject matter. 
           [0015]      FIG. 8  is an elevation showing a physical configuration of a UPS according to some embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Specific exemplary embodiments of the inventive subject matter now will be described with reference to the accompanying drawings. This inventive subject matter may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. In the drawings, like numbers refer to like elements. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0017]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0018]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0019]      FIG. 2  illustrates a UPS  200  according to some embodiments of the inventive subject matter. The UPS  200  includes a frame  210 . The frame  210  supports at least one AC input  201  for connection to at least one external AC power source and at least one AC output  202  for connection to at least one external load. Such connections may be provided using, for example, plug-in type connectors, terminal strips, wire lugs or the like. The UPS  200  also includes a power conversion circuit including a rectifier  211  and an inverter  212 , also supported by the frame  210 . The UPS  200  further includes a DC/DC converter  213 , first static switch  215 , second static switch  216  and associated control circuit  217  supported by the frame  210 . 
         [0020]    The rectifier  211  is coupled to the at least one AC input  201 , and is configured to produce a DC voltage on a DC link  214  from AC power provided at the at least one AC input  201 . The inverter  212  is coupled to the DC link  214  and to the at least one AC output  202  and is configured to generate an AC voltage at the at least one AC output  202  from a DC voltage on the DC link  214 . The DC/DC converter  213  is also coupled to the DC link  214  and is configured to interface to a battery  10 , here shown as located external to the UPS  200 . In some embodiments, the DC/DC converter  213  may be omitted, and a direct connection between the battery  10  and the DC link  214  may be provided. In some embodiments, the battery  10  may be included in the UPS  200 , i.e., may be supported by the common frame. 
         [0021]    The first static switch  215  is coupled to the at least one AC input  201  and to the at least one AC output  202  and provides a switchable path therebetween under control of the control circuit  217 . Similarly, the second static switch  216  is coupled to the at least one AC input  201  and to the at least one AC output  202  and provides a switchable path therebetween under control of the control circuit  217 . As shown, the first and second static switches  215 ,  216  may be implemented using anti-parallel connected thyristors (e.g., silicon-controlled rectifiers (SCRs)), but it will be understood that the first and second static switches  215 ,  216  may be implemented using other arrangements of semiconductor and/or mechanical switching devices. Although the UPS  200  of  FIG. 2  may provide respective external connections for the rectifier  211 , inverter  212  and the first and second static switches  215 ,  216  it will be appreciated that common external connections may be provided for subsets of these components. For example, the rectifier  211  and the first static switch  215  may be internally connected such that a single external connection may be used for both the rectifier  211  and the first static switch  215 . Similarly, the inverter  212  and the first static switch  215  may be internally connected such that a single external connection may be used for both the inverter  212  and the first static switch  215 . 
         [0022]    A control circuit  217  is configured to control the rectifier  211 , inverter  212 , DC/DC converter  213  and the first and second static switches  215 ,  216  in a coordinated manner. For example, in the event of a failure of the rectifier  211 , the inverter  212  or an AC power source coupled to the rectifier  211 , the control circuit  217  may operate one of the first and second static switches  215 ,  216  to provide an alternate path for power flow to the load  20 . The control circuit  217  may also operate one of the first and second static switches  215 ,  216  to support an increased efficiency mode of operation in which the rectifier  211  and the inverter  212  are bypassed to provide power directly to the load  20 , with the inverter  212  operating in a standby or active filter mode to provide battery backup power and/or power conditioning. It will be understood that, in general, the control circuit  217  may be implemented using analog circuitry, digital circuitry or combinations thereof. The control circuit  217  may include, for example, one or more data processing devices, such as a microprocessor or microcontroller, along with circuitry for driving power conversion components of the rectifier  211  and inverter  212  and the first and second static switches  215 ,  216 . 
         [0023]    As described herein, a UPS, such as the UPS  200  of  FIG. 2 , is a unitary, discrete assembly configured as a single unit, as opposed to a collection of physically separated units interconnected by wiring external to the units (e.g., cables run loosely or in conduits or cable trays). In  FIG. 2 , the UPS  200  is shown as including a frame  210  conceptually illustrated using a bounding rectangle. In some embodiments, the frame  210  may be a supporting structure, such as an enclosure or housing or a set of housings conjoined or otherwise attached in a manner that provides a unitary structure. The enclosure or housing may be open, closed or may have open and closed portions and/or portions that may be accessible via doors or similar features. The enclosure or housing may contain components, such as support struts, support rails, interior shelves, etc., that are used to support electrical components of the UPS, such as the rectifier  211 , inverter  212 , DC/DC converter  212  and other electrical components of the UPS  200  of  FIG. 2 . An example of such a frame is illustrated in  FIG. 8 , which shows a UPS  800  with a unitary frame  810  including multiple cabinet-like sections  812   a ,  812   b ,  814 ,  816   a ,  816   b ,  816   c  conjoined to form a structural unit. The UPS  800  is provided for purposes of illustration, and it will be appreciated that other frame arrangements may be used in some embodiments. 
         [0024]      FIG. 3  illustrates an exemplary use of the UPS  200  of  FIG. 2  to provide source redundancy according to some embodiments. First and second UPSs  200   a ,  200   b  have their rectifiers  211  coupled to a first AC power source A and their inverters  212  coupled to respective loads  20   a ,  20   b . The first static switches  215  of the first UPS  200   a  and the second UPS  200   b  are also coupled to the first AC power source A, while the second static switches  216  of the first UPS  200   a  and the second UPS  200   b  are coupled to a second power source B. It will be appreciated that coupling between the first static switches  215  and the rectifiers  211  and inverters  212  may be external and/or may be internal to the UPSs  200   a ,  200   b , as discussed above with reference to  FIG. 2 . 
         [0025]    Some UPSs having a static bypass may be operated to provide a high efficiency mode wherein the bypass path is closed, allowing power to be transferred directly from the UPS input to the UPS output without passing through a rectifier/inverter chain, thus reducing losses associated with the operation of those components. Such a mode may be used, for example, when the AC input meets power quality criteria, with the rectifier/inverter chain being placed in a standby and/or active filter state. In such a state, the rectifier/inverter chain may be re-engaged should the AC input cease to meet those power quality criteria. Examples of such high-efficiency operating modes are described, for example, in U.S. Pat. No. 6,295,215 to Faria et al. 
         [0026]    An arrangement along the lines shown in  FIG. 3  may be particularly advantageous for providing redundant sourcing while also supporting a high efficiency mode. Referring to  FIG. 3 , when operating the first UPS  200   a  or the second UPS  200   b  in an on-line mode, the first and second static switches  215 ,  216  are open. If it is desired to transfer to a high-efficiency bypass mode, the control circuit  217  may close the first static switch  215 , thus bypassing the rectifier  211  and inverter  212 . In this mode, the inverter  212  may operate in a standby and/or active filtering mode, along the lines discussed above. The second static switch  216  provides the capability for the control circuit  217  to transition from the high-efficiency mode to the alternative second AC source B in the event the first AC source A fails. Because control of the first and second static switches  215 ,  216  is integrated with control of the rectifier  211  and the inverter  212  in a single UPS, this operation may be performed more smoothly and/or reliably, as coordination with external switches or other downstream devices may not be required. 
         [0027]    UPSs according to some embodiments may also be used advantageously in isolated redundant and other power system arrangements. For example, as shown in  FIG. 4 , a power system may include first, second and third UPSs  200   a ,  200   b ,  200   c , each including a rectifier  211 , inverter  212 , DC/DC converter  213  and first and second static switches  215 ,  216 . The rectifiers  211  and first static switches  215  of the UPSs  200   a ,  200   b ,  200   c  are coupled to a first power source A. The second static switches  216  of the UPSs  200   a ,  200   b ,  200   c  are coupled to the output of a fourth UPS  300 . A rectifier  311  of the fourth UPS  300  is configured to be coupled to the first power source A such that, in the event of the failure of the rectifier  211  and/or inverter  212  or one or more of the first, second and third UPSs  200   a ,  200   b ,  200   c , power may be passed via the rectifier  311  and inverter  312  of the fourth UPS  300  and the second static switch  216  of the affected one or more of the first, second and third UPSs  200   a ,  200   b ,  200   c . If the first power source A fails when in this configuration, power may be supplied from the battery associated with the fourth UPS  300  via the inverter  312  of the fourth UPS  300  and the second static switch  216  of the affected one or more of the first, second and third UPSs  200   a ,  200   b ,  200   c . Should the rectifier  311  and/or inverter  312  of the fourth UPS  300  fail, a static switch  315  of the fourth UPS  300  may be closed, allowing power to pass from an alternative power source B to the second static switches  216  of the first, second and third UPSs  200   a ,  200   b ,  200   c.    
         [0028]    It will be appreciated that UPSs according to some embodiments of the inventive subject matter may be advantageously used in other power system arrangements, for example, to enable provision of power to separate loads from a single UPS.  FIG. 5  illustrates an application in which a first UPS  200  as discussed above with reference to  FIG. 2  is coupled to a first power source A and to a first load  20   a . A second UPS  500 , which includes a rectifier  511  and an inverter  512  and a DC/DC battery converter  513  coupled to a DC link  514 , is coupled to a second power source B and a second load  20   b . A static switch  515  is configured to bypass the rectifier  511  and the inverter  512 . The second power source B is coupled to the rectifier  511  and the static switch  515 , and the second load  20   b  is coupled to the inverter  512  and the static switch  515 . 
         [0029]    The rectifier  211  of the first UPS  200  is coupled to the first power source A, while the inverter  212  is coupled to the first load  20   a . A first static switch  215  of the first UPS  200  is coupled connected to the first power source A and to the first load  20   a  and a second static switch  216  of the first UPS  200 . The second static switch  216  of the first UPS  200  is also coupled to the second load  20   b . This arrangement allows the first UPS  200  to provide power to the second load  20   b  from the inverter  212  or from the first power source A via the second static switch  216 . The second static switch  216  may also be used to provide power to the first load  20   a  from the second UPS  500 , i.e., from either the inverter  512  or via the static switch  515 . 
         [0030]      FIG. 6  illustrates a further application of a UPS  200  along the lines discussed above with reference to  FIG. 2 . A rectifier  211  is coupled to a power source A, while an inverter  212  is coupled to a first load  20   a . A first static switch  215  is connected between the power source A and the first load  20   a , while the second static switch  216  is coupled between the power source A and a second load  20   b . The first load  20   a  may be, for example, a critical load for which UPS redundancy is desirable, while the second load  20   b  may be, for example, non-critical load that does not require UPS protection. 
         [0031]      FIG. 7  illustrates yet another application of a UPS  200  along the lines discussed above with reference to  FIG. 2 . A rectifier  211  is coupled to a power source A, which an inverter  212  is coupled to a first load  20   a . A first static switch  215  is coupled between the power source A and the first load  20   a . A second static switch  216  is coupled between inverter  212  and first static switch  215  and a second load  20   b . This arrangement may allow for shedding of the second load  20   b  under certain circumstances, for example, when the UPS  200  is operating in an on-line and/or on-battery mode and has insufficient capacity to power both the first load  20   a  and the second load  20   b.    
         [0032]    It will be appreciated that the power system arrangements of  FIGS. 3-7  are provided for purposes of illustrations, and that UPSs according to further embodiments may be used in other ways. 
         [0033]    In the drawings and specification, there have been disclosed exemplary embodiments of the inventive subject matter. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter being defined by the following claims.