Patent Publication Number: US-11031806-B2

Title: Uninterruptible power supply systems and methods using interconnected power routing units

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/154,194; filed Oct. 8, 2018 which is a continuation of U.S. patent application Ser. No. 15/139,957, filed Apr. 27, 2016, the contents of which are incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     The inventive subject matter relates to power distribution systems and methods and, more particularly, to uninterruptible power supply (UPS) systems and methods. 
     UPS systems are commonly used in installations such as data centers, medical centers and industrial facilities. UPS systems may be used in such installations to provide backup power to maintain operation in event of failure of the primary utility supply. These UPS systems commonly 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 UPS systems may use standby, line-interactive or other architectures. 
     UPS systems may be implemented using modular assemblies. For example, a UPS system may include multiple UPS modules, each of which may include, for example, a rectifier, an inverter and a DC/DC converter for interfacing to a battery. The UPS modules may be mounted in a common chassis, along with control and interface circuitry, such as bypass switches and the like. The UPS modules may be 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. An example of such a modular UPS assembly is the Eatona Power XPert 9395 UPS (described at http://powerquality.eaton.com), which may be configured to include two or more uninterruptible power modules (UPMs), each of which include a double conversion UPS circuit including a rectifier, inverter and battery converter coupled to a common DC bus. Other modular UPS architectures are described in U.S. patent application Ser. No. 13/936,741 entitled “UPS Systems and Methods Using Variable Configuration Modules,”, filed Jul. 8, 2013 and incorporated herein by reference. 
     SUMMARY 
     Some embodiments of the inventive subject matter provide a system including a plurality of power routing units. Each of the power routing units includes a first AC port, a second AC port, and a static switch configured to couple and decouple the first AC port and the second AC port. Each of the power routing units further includes a DC port and a bidirectional converter circuit coupled between the second AC port and the DC port. The DC ports of the power routing units are coupled in common to a DC bus and the system further includes a control circuit configured to control the power routing units to provide power transfer between at least two of the power routing units via the DC bus. 
     In some embodiments, the first AC port of a first power routing unit may be coupled to a first AC power source and the first AC port of a second power routing unit may be coupled to a second AC power source. The control circuit may be configured to cause the second power routing unit to provide power to the first power routing unit via the DC bus responsive to a failure of the first AC power source and/or a failure of the static switch of the first power routing unit. 
     In further embodiments, the second AC port of the first power routing unit may be coupled to a first load and the second AC port of the second the power routing unit may be coupled to a second load. The second power routing unit may be configured to provide power to the first load from the second AC power source via the static switch and converter circuit of the second power routing unit, the DC bus and the converter circuit of the first power routing unit. 
     In some embodiments, the control circuit may be configured to control the power routing units to provide power to a first power routing unit from a second power routing unit and a third power routing unit via the DC bus. The control circuit may be configured to operate the second power routing unit to regulate a voltage on the DC bus and to operate the third power routing unit as a regulated current source to provide power to the first power routing unit. The second AC ports of the first, second and third power routing units may be coupled in common to an AC power source, and the first AC ports of the first, second and third power routing units may be coupled to respective first, second and third loads. 
     According to further embodiments, the first AC ports of a first power routing unit and a second power routing unit may be coupled in common to an AC power source, the second AC ports of the first and second power routing units may be coupled to respective first and second loads, and the control circuit may be configured to concurrently provide power from the AC power source to the first load via the static switch of the first power routing unit and to the second load via the converter circuits of the first and second power routing units. The control circuit may be configured to operate two of the power routing units to provide a multiple converter power chain from an AC source to a load coupled to one of the two power routing units. 
     In some embodiments, the control circuit may include respective local control circuits in respective ones of the power routing units and a master controller configured to control the local control circuits of the power routing units. 
     In some embodiments, the control circuit may include respective local control circuits positioned in the power routing units and configured to operate the associated converter circuit to selectively provide a first mode wherein the converter circuit regulates a voltage on the DC bus and a second mode wherein the converter circuit provides a regulated current to the DC bus. 
     In some embodiments, the system may further include a DC power source coupled to the DC bus. 
     In further embodiments, the static switch may be a first static switch and each of the power routing units may further include a third AC port and a second static switch configured to couple and decouple the third AC port and the second AC port. 
     Further embodiments provide a power routing unit including a first AC port configured to be coupled to an external AC source, a second AC port configured to be coupled to an external load, and a static switch configured to couple and decouple the first AC port and the second AC port. The power routing unit further includes a DC port configured to be coupled to an external DC bus, a bidirectional converter circuit coupled between the second AC port and the DC port, and a control circuit configured to control the static switch and the converter circuit to selectively provide a first mode wherein the converter regulates a voltage on the external DC bus and a second mode wherein the converter provides a regulated current to the external DC bus. 
     Further embodiments provide methods including providing a plurality of power routing units, each comprising a first AC port, a second AC port, a static switch configured to couple and decouple the first AC port and the second AC port, a DC port, and a bidirectional converter circuit coupled between the second AC port and the DC port. The methods further include coupling the DC ports of the power routing units in common to a DC bus and controlling the power routing units to provide power transfer between at least two of the power routing units via the DC bus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an uninterruptible power supply (UPS) system using interconnected power routing units according to some embodiments. 
         FIG. 2  is a schematic diagram illustrating an example of a circuit configuration for the power routing units of  FIG. 1 . 
         FIG. 3  is a schematic diagram illustrating a static UPS system according to some embodiments. 
         FIG. 4  is a schematic diagram illustrating catcher UPS system according to some embodiments. 
         FIGS. 5 and 6  is a schematic diagram illustrating a UPS system with reconfigurable operational modes using power routing units according to some embodiments. 
         FIG. 7  is a schematic diagram illustrating a control architecture for DC bus control in a UPS system according to some embodiments. 
         FIG. 8  is a schematic diagram illustrating applications of the control architecture of  FIG. 7  in a UPS system according to some embodiments. 
         FIG. 9  is a schematic diagram illustrating a UPS system using power routing units with multiple static switches according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     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 items. It will be understood that when an item is referred to as being “connected” or “coupled” to another item, it can be directly connected or coupled to the other item or intervening items may be present. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     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, items, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, items, components, and/or groups thereof. 
     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. 
       FIG. 1  illustrates a system according to some embodiments of the inventive subject matter. The system includes a plurality of power routing units  110 , which are connected in common to an external DC bus  120 . Each of the power routing units  110  includes at least one static switch  112 , which is connected between an AC input port  111  and an AC output port  113  of the power routing unit  110 . Each power routing unit  110  further includes at least one bidirectional converter circuit  114 , which is coupled between the AC output port  113  and a DC port  115 , the latter of which is coupled to the DC bus  120 . The converter circuit  114  is configured to support power flows in two directions to support a variety of different arrangements of power routing units  110 , as explained in greater detail with reference to  FIGS. 3-9 . 
     It will be appreciated that the power routing units  110  may be implemented using any of a number of different types of circuitry. For example, the statics switches  112  may be implemented using any of a variety of different types of solid-state switching devices, such as SCRs or power MOSFETs. The converter circuits  114  may be implemented using different types of converter architectures, such as bridge converter circuits. These circuits may use any of a variety of different types of solid-state switching devices, such as IGBTs or power MOSFETs. The static switches  112  and converters  114  may be controlled using any of a variety of different analog and/or digital control circuits including, but not limited to, microcontroller-based or other types of digital control circuits. 
       FIG. 2  illustrates an example of a circuit configuration for a power routing unit according to further embodiments. A power routing unit  210  includes a three-phase static switch  212 , which is implemented using pairs of anti-parallel connected silicon controlled rectifiers (SCRs). The static switch  212  is coupled between an AC input port  211  and an AC output port  213  of the power routing unit. The power routing unit  210  further includes a three-phase bridge circuit  214 , which incorporates transistors Q (e.g., IGBTs or power MOSFETs) coupled respective half-bridge pairs for the respective phases and respective inductors L for the respective phases. The bridge circuit  214  is coupled between the AC output port  213  and a DC port  215 . The bridge circuit  214  may further include one or more DC link capacitors C coupled to the DC port  215 , which may provide energy storage to support maintenance of a voltage on a DC bus connected to the DC port  215 , but it will be appreciated that such capacitance could be provided or supplemented by capacitors located external to the power routing unit  210 . A control circuit  216  is configured to control the static switch  212  and the bridge circuit  214  to provide various modes of operation that support various power flows between the AC ports  211 ,  213  and the DC port  215 . The control circuit  215  may be implemented using any of a variety of different analog and/or digital circuits, including, for example, control circuitry employing data processing circuitry, such as microcontroller or microprocessor. 
     According to some embodiments, power routing units along the lines described above with reference to  FIGS. 1 and 2  may be used to provide a variety of different uninterruptible power supply (UPS) systems. For example, referring to  FIG. 3 , a UPS system may include first and second power routing units  310   a ,  310   b , each of which includes a static switch  312 , a converter circuit  314  and a control circuit  316  that controls the static switch  312  and the converter circuit  314 . Respective first and second sources  10   a ,  10   b  are coupled to the AC input ports of respective ones of the power routing units  310   a ,  310   b , and respective loads  20   a .  20   b  are connected to the AC output ports of respective ones of the power routing units  310   a ,  310   b . DC ports of the power routing units  310   a ,  310   b  are connected in common to a DC bus  320 . 
     The arrangement illustrated in  FIG. 3  may be implemented as a battery-free static UPS system. In particular, under normal operating conditions, power may be provided to the first and second loads  20   a ,  20   b  from respective ones of the first and second AC sources  10   a ,  10   b  via the static switches of respective ones of the first and second power routing units  310   a ,  310   b . Responsive to failure of for example, the first AC source  10   a , power may be provided to the first load  20   a  from the second power source  20   b  via the converter circuit  314  of the second power routing unit  310   b , the DC bus  320 , and the converter circuit  314  of the first power routing unit  310   a . Similarly, in response to failure of the second AC source  10   b , power may be provided to the second load  20   b  from the first AC source  10   a  via the converter circuit  314  of the first power routing unit  310   a , the DC bus  320 , and the converter circuit  314  of the second power routing unit  310   b.    
     As further shown in  FIG. 3 , a DC power source  15  may be coupled to the DC bus  320 . The DC power source  15  may include, for example, a battery, fuel cell generator, photovoltaic source, or the like. In some embodiments, the DC source  15  may be used to provide additional backup power in case of failure of either or both of the AC sources  10   a ,  10   b . In further embodiments, the DC source  15  may be used, for example, to support power sharing operations, such as peak shaving operations that use the DC source  15  to provide supplemental power during peak rate periods for either or both of the AC sources  10   a ,  10   b.    
       FIG. 4  illustrates another UPS system arrangement that advantageously uses power routing units as described above. First, second and third power routing units  310   a ,  310   b ,  310   c  have AC output connected to respective loads  20   a ,  20   b ,  20   c , have their AC input ports connected in common to an AC source  10  and have their DC ports coupled in common to a DC bus  320 . Each of the first, second and third power routing units  310   a ,  310   b ,  310   c  includes a static switch  312 , a converter circuit  314  and a control circuit  316  that controls the static switch  312  and the converter circuit  314 . A master controller  30  is configured to communicate with the control circuits  316  to provide monitoring and supervisory control. 
     The power routing units  310   a ,  310   b ,  310   c  may be operated to provide backup power delivery options. For example, under normal conditions, the power routing units  310   a ,  310   b ,  310   c  may provide power their respective loads  20   a ,  20   b ,  20   c  via their static switches  312 . In response to failure of, for example, the static switch  312  of the first power routing unit  310   a , the second and third power routing units  310   b ,  310   c  may provide power to the first load  20   a  via the DC bus  320 . Such operations may be controlled by the master controller  330 , which may, for example, receive status information from the first power routing unit  310   a  indicating failure of its static switch  312 , and may command the first power routing unit  310   a  to operate its converter circuit  314  as an inverter to provide power to the first load  20   a . The master controller  330  may concurrently command the second and third power routing units  310   b ,  310  to operate their converter circuits  314  as rectifiers to provide power needed to support operation of the converter  314  of the first power routing unit  310   a.    
     The arrangement shown in  FIG. 4  may also be used to support flexible configuration of power delivery paths that provide different levels of power security for loads having differing levels of criticality. For example, referring to  FIG. 5 , the second load  20   b  may have a greater criticality than the first and third loads  20   a ,  20   c , and the first and second power routing units  310   a ,  310   b  may be used to provide a double conversion chain for providing increased power quality for the second load  20   b . In particular, the first power routing unit  310   a  may provide power to the first load  20   a  via its static switch  312 , and may concomitantly operate its converter circuit  314  as a rectifier to provide power to the DC bus  320 . The second power routing unit  310   b  may open its static switch  312  and operate its converter circuit  314  as an inverter to provide power to the second load  20   b  from the DC bus  320 , thus isolating the second load  20   b  from quality deviations of the AC source  10 . In this functional mode, the static switch  312  of the second power routing unit  310   b  may be used as in a manner similar to that way a static bypass switch is used in a conventional double conversion UPS. For example, the static switch  312  of the second power routing unit  310   b  may be closed and the converter circuit  314  of the second power routing unit  310   b  may e inactivated responsive to a power quality of the AC source  10  meeting a certain power quality criterion, such that the second load  20   b  may be provided power in a more efficient manner. If the power quality of the AC source  10  again deviates, the static switch  312  may be opened and the second load  20   b  again powered using the double conversion power train. 
     In further embodiments, the third power routing unit  310   c  may be used in a similar manner, such that both of the first and third power routing units  310   a ,  310   c  provide power to the DC bus  320  for use by the converter circuit  314  of the second power routing unit  310   b . Power security allocations may also be dynamically adjusted. For example, as shown in  FIG. 6 , the system may be configured to transition to operating the converter circuits  314  of the second and third power routing units  310   b ,  310   c  to provide double conversion power train for the third load  20   c . Such dynamic configurability may be particularly useful in some applications, such as data center applications in which the loads  20   a ,  20   b ,  20   c  are different groups of servers or other computing equipment that run processes that have changing power security needs. 
       FIG. 7  illustrates a control architecture that may be used to support power transfers among power routing units according to further embodiments. Referring to  FIG. 7  in conjunction with  FIG. 8 , power routing units  310   a ,  310   b ,  310   c  may be configured to operate their converter circuits  314  to provide voltage or current control of the DC bus  320 . As shown in  FIG. 8 , the first and second power routing units  310   a ,  310   b  may be used to provide power to the third power routing unit  310  having a failed static switch  312 . To facilitate this transfer, the converter circuit  314  of the first power routing unit  310   a  may be operated in a voltage control mode wherein it maintains a desired voltage on the DC bus  320 , while the converter circuit  314  of the second power routing unit  310  is used in a controlled current mode wherein it provides a desired amount of current to the DC bus  320 . The amount of current provided by the second power routing unit  310   b  may be commanded by the master controller  330 . 
     Each of the power routing units  310   a ,  310   b ,  310   c  may be configured to provide a control architecture supporting multiple control modes for their converters  314 . In a voltage control mode, a compensator  710  of a voltage loop provides a first current command I DC1  via a selector  720  to a current loop having a compensator  730  that provides a control signal to a pulse width modulation (PWM) driver circuit  740 , which drives transistors or other switching elements of the converter. When operating in a current control mode, however, the selector  720  provides a second current command I DC2  to the current loop instead, wherein the second current command I DC2  represents a desired current output of the converter. The second current command I DC2  may be provided, for example, from the master controller  330 . The compensators  710 ,  730  may take any of a variety of different forms, including, but not limited to, proportional, differentiator, integrator, proportional integrator-differentiator (PID), lead-lag, and combinations thereof. 
     According to further embodiments, a power routing unit may include more than one static switch to support other UPS system configurations. For example, referring to  FIG. 9 , a system may include first and second power routing units  910   a ,  910   b , each of which includes first and second static switches  912   a ,  912   b  and a converter circuit  914 . AC output ports of the first and second power routing units  910   a ,  910   b  are coupled to respective first and second loads  20   a ,  20   b . First and second AC inputs of the power routing units  910   a ,  910   b  are connected to respective ones of first and second AC sources  10   a ,  10   b . DC ports of the first and second power routing units  910   a ,  910   b  are coupled in common to a DC bus  920 . 
     This arrangement can be used to provide flexibility in power routing and redundancy in the event of component or source failure. For example, this arrangement allows the loads  20   a ,  20   b  to be coupled to either of the AC sources  10   a ,  10   b  via the static switches  912   a ,  912   b . This arrangement can also be used to provide a double conversion power chain for either of the loads  20   a ,  20   b.    
     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.