Patent Application
20170045924
The present disclosure relates generally to power supplies as are used in computer datacenters, and relates more particularly to an uninterruptible power supply system where multiple power supply paths have different component counts.
A great many different architectures and operating strategies have been proposed for electrical power supply and distribution over the years. In certain environments, it is desirable to have redundant or backup power available in the event of the failure of a primary power supply. One known design includes multiple, fully redundant pathways of essentially identical structure. Such systems provide reliable operation; however, there is always room for improvement.
A power supply system includes an alternating current (AC) input interface and a direct current (DC) output interface, in a plurality of power supply paths extending between the AC input interface and the DC output interface. A first one of the plurality of power supply paths has a lower component count, and a second one of the plurality of power supply paths has a higher component count. Each power supply path has a power converter structured to convert AC electrical power to DC electrical power. One of the power supply paths provides electrical power at a varying voltage, whereas the other provides electrical power at a fixed voltage.
For purposes of promoting an understanding of the principles of the ELECTRICALLY POWERED COMPUTER SYSTEM AND POWER SUPPLY SYSTEM FOR SAME, reference will now be made to the examples illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain examples of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention.
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System 11 may further include an AC input interface 18 structured to couple with AC electrical power supply 14, and potentially also with power supply 16. System 11 may also include a DC output interface 24 having at least one remote power panel 35, 37, and in the illustrated embodiment two remote power panels. System 11 may also include a plurality of power supply path 30, 32 structured to supply electrical power from the AC input interface 18 to DC output interface 24 so as to energize remote power panels 35 and 37 for powering an electrical load such as computers 12. As will be further apparent from the following description, system 11 is uniquely configured for reliability and redundancy in power supply while providing reduced costs and complexity as compared with known designs.
System 11 may further include one or more power supply units 39 that feed computers 12. Input circuitry 62 is provided and includes appropriate switching elements 64 and 66 which may have the form of automated transfer switches (ATS), structured to connect either one of power supplies 14 and 16 to either one of power supply paths 30 and 32. Maintenance switches 68 and 70 may be provided so as to enable selectively disconnecting circuitry 62 or parts of circuitry 62 from either or both of power supply paths 30 and 32.
DC output interface 24 may further include at least one power bus 34 structured to receive DC electrical power from power supply paths 30, 32, and in the illustrated embodiment includes a first power bus 34 associated with first power supply path 30 and a second power bus 35 associated with power supply path 32. A DC feeder 40 is also provided as a part of or coupled with output interface 24 and structured to feed DC electrical power from power supply paths 30, 32, or one of those power supply paths, to remote power panel 35 and/or 37, or a single remote power panel as the case may be. A first power distribution unit 44 forms part of DC output interface 24 and is associated with bus 34 and first power supply path 30, whereas a second power distribution unit 46 is associated with bus 35 and receives electrical power via power supply path 32. Each of power supply paths 30 and 32 may include a power converter 48 and 50, respectively, structured to convert AC electrical power from AC input interface 18 to DC electrical power to be supplied to power bus 34 and power bus 35. A power converter, charger, and battery may be provided together as one physical unit in a practical implementation strategy. In one embodiment, power converter 48 in first power supply path 30 converts AC electrical power to DC electrical power at a fixed voltage, and power converter 50 likewise converts AC electrical power to DC electrical at a fixed voltage. It will be recalled that DC feeders 40 and 42 are coupled between buses 34 and 35 and remote power panels 35 and 37, respectively. In the embodiment of
Those skilled in the art of redundant and uninterruptible power supply systems will be familiar with certain hardware differences among fixed voltage systems and varying voltage systems. Where voltage is predictable and reliable, hardware components such as cabling can be relatively less expensive than in instances where voltage is varying. In the case of systems where voltage is expected to vary, the less expensive fixed voltage hardware is generally unavailable. In a practical implementation strategy, each of power converter 48 and power converter 50 may include an AC to DC buck converter, otherwise known as a buck rectifier or step down converter. Each buck rectifier can be of a variety of different topologies and constructions, including a passive rectifier such as a thyristor-based rectifier. An actively controlled rectifier can also be used. The choice of rectifier may depend upon control and dynamics requirements of critical loads in computers 12, such as critical loads where computers 12 are part of a data center and thus corresponding to a minimum electrical power supply requirement to avoid data losses. Harmonics requirements or properties of power supply 14 and potentially power supply 16 can also affect selection of a suitable rectifier.
As noted above, each of converters 48 and 50 can generally supply DC electrical power to the corresponding bus 34 and 33 at a fixed voltage. As it is desirable to provide a backup power supply, second power supply path 32 is equipped with an energy storage device 52 such as a battery in parallel with converter 50 and structured to supply DC electrical power to bus 33 at a varying voltage. It can thus be appreciated that electrical power can be supplied to computers 12 by way of either or both of power supply paths 30 and 32. In a practical implementation strategy, one mode of operation can include supplying electrical power only via path 30, but transitioning via switching elements from path 30 to path 32 only in the event of a fault, such as a fault or failure in converter 48. In the event of a fault in power supply path 32, such as in converter 50, battery 52 may be operated to supply DC electrical current to bus 33. In the illustrated embodiment, battery 52 may be trickle charged by way of a charger 54 coupled with an AC input bus 74, with battery 52 electrically connected to bus 33 by way of a maintenance switch or the like 60. Diodes 56 and 58 may be positioned electrically between battery 52 and charger 54 and electrically between battery 52 and switch 60, respectively. As discussed above, in certain embodiments a standard or normal operating condition can include supplying power via path 30, whereas a backup operating condition can include supplying power via path 32. As charger 60 may trickle charge battery 52, it can be sized at a much reduced capacity. In instances and for operating strategies where substantially all of the load of power supply unit 39 and associated electrical loads is carried by path 30, the system efficiency will be determined principally by an efficiency of buck converter 50. In certain embodiments, converters 48 and 50 may reduce voltage from a first level that is from about 700 volts to about 800 volts down to a second level that is from about 350 volts to about 450 volts.
Those skilled in the art will further be familiar with the additional costs that typically accompany the addition of components. Additional components, additional connections, additional power supplies and duplications of hardware are typically understood to improve reliability, but of course typically increase costs. What is generally less intuitive is the addition of potential failure modes with the addition or duplication of hardware. In other words, a system that has many different components versus a relatively simpler system with fewer components will often at first impression appear to be more reliable. When a more quantitative consideration of the likelihood of failure of the overall system, as well as likelihood of failure of subcomponents of the system is conducted, however, as in the present instance it becomes apparent that likelihood of failure is not in fact increased or only modestly so, where some of the duplication and addition of hardware is avoided. As described herein, power supply path 30 may have a lesser component count, for example a count of one, corresponding to power converter 48. Power supply path 32 may have a greater component count, for example a count of two, corresponding to converter 50 and battery 52. In the present instance, a sufficiently reliable or even more reliable system can be provided even though one of the possible power supply paths has fewer components, and in fact lacks the backup power supply of an energy storage device altogether. When a fault occurs in path 32, system 11 can be switched to a backup mode where electrical power is supplied via battery 52. Conventional systems might have included multiple power supply paths that were substantially identical, with each including a battery or other energy storage device. In the present instance, it can be seen that only one of paths 30 and 32 includes a battery.
In recent years, DC power supply systems have been increasingly applied in areas that traditionally relied upon AC. Demands for so-called greener power have resulted in the increased exploitation of renewables such as solar and wind and DC systems may be better suited to such applications than traditional AC, especially respecting efficiency and cost. The present disclosure provides similar advantages over AC systems. The present disclosure also provides advantages over many of the DC systems that been developed as AC alternatives, particularly with regard to the conventional wisdom respecting component count and failure modes.
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The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.
