Patent Description:
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 common 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. In some UPS applications, a variably available renewable source, such as a photovoltaic source, may be coupled to the DC link of an on-line UPS to provide supplemental power, as described, for example, in <CIT> to Parmley and an article entitled "<NPL>.

Further, attention is drawn to <CIT>, which relates to an electronic interface that couples a combination of generation and storage devices with a power grid and/or a load. The interface comprises a DC bus; a DC storage device coupled to the DC bus; a first DC-to-AC inverter having a DC port operatively coupled to the DC bus, and an AC port; a second DC-to-AC inverter having a DC port operatively coupled to the DC bus, and an AC port; a switch for electrically coupling the AC port of the second DC-to-AC inverter to a first generator or an AC storage device; a first rectifier for coupling an AC output of the first generator to the DC bus; and a second rectifier for coupling an AC output of the AC storage device to the DC bus.

A frequent goal in such applications is to provide uninterruptible power with high efficiency. Towards this end, on-line UPSs that are used in such applications may support an "efficiency" mode in which the rectifier/inverter conversion chain is bypassed using a static switch when the utility source is within nominally acceptable bounds.

In accordance with the present invention, a UPS system and a method for operating a UPS system as set forth in claims <NUM> and <NUM> are provided. Further embodiments are inter alia disclosed in the dependent claims.

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. 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, 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.

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.

As will be appreciated by one of skill in the art, the inventive subject matter may be embodied as systems, methods and computer program products. Some embodiments of the inventive subject matter may include hardware and/or combinations of hardware and software. Some embodiments of the inventive subject matter include circuitry configured to provide functions described herein. It will be appreciated that such circuitry may include analog circuits, digital circuits, and combinations of analog and digital circuits.

Embodiments of the inventive subject matter are described below with reference to block diagrams and/or operational illustrations of systems and methods according to various embodiments of the inventive subject matter. It will be understood that each block of the block diagrams and/or operational illustrations, and combinations of blocks in the block diagrams and/or operational illustrations, can be implemented by analog and/or digital hardware, and/or computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, ASIC, and/or other programmable data processing apparatus, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or operational illustrations. In some implementations, the functions/acts noted in the figures may occur out of the order noted in the block diagrams and/or operational illustrations. For example, two operations shown as occurring in succession may, in fact, be executed substantially concurrently or the operations may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

The inventive subject matter relates to interfacing of variably available power sources with UPSs. As referred to herein, "variably available power sources" include power sources, such as solar, wind, tidal and similar renewable energy sources, having an availability (presence and/or capacity) that fluctuates with environmental conditions (e.g., availability of wind, sun or tidal change) and that are not, as a general rule, available on demand. Such power sources may also be referred to as "variable", "intermittent" or "non-dispatchable" and, for purposes of the present application, such sources shall be referred to as "variably available power sources.

<FIG> illustrates a UPS system <NUM> showing part of the features of the inventive subject matter. The UPS system <NUM> includes an AC input <NUM> configured to be coupled to an AC power source <NUM> and an AC output <NUM> configured to be coupled to a load <NUM>. The AC power source <NUM> may be single or multiphase and may comprise, for example, a utility source and/or a local source, such as a generator. The load <NUM> may comprise, in general, one load or an aggregation of single and/or multiphase loads, such as a collection of three-phase and single phase loads that may be found in a typical data center or similar facility.

The UPS system <NUM> includes a first power conversion circuit <NUM> including a first converter circuit <NUM> configured to receive power from a variably available power source <NUM>, a second converter circuit <NUM> coupled to the AC output <NUM>, and a DC link <NUM> coupling the first and second converter circuits <NUM>, <NUM>, Depending on the nature of the variably available source <NUM>, the first converter circuit <NUM> may operate as an AC/DC converter (a rectifier) or as a DC/DC converter.

The UPS system <NUM> also includes a second power conversion circuit <NUM> that is configured to operate as an on-line UPS. The second power conversion circuit <NUM> includes an AC/DC converter circuit <NUM> coupled to a DC/AC converter circuit <NUM> by a DC link <NUM>. An auxiliary power source <NUM> (e.g., one or more batteries) is coupled to the DC link <NUM>, and may supply backup power in the event of a failure of the AC power source <NUM>. An additional auxiliary power source <NUM> may be coupled to the DC link <NUM> of the first power conversion circuit <NUM>.

The UPS system <NUM> further includes a switching circuit, here shown as a bypass circuit <NUM> configured to selectively bypass the second conversion circuit <NUM> by selectively coupling and decoupling the AC input <NUM> and the AC output <NUM>. A control circuit <NUM> is operatively associated with the first power conversion circuit <NUM>, the second power conversion circuit <NUM> and the bypass circuit <NUM> and configured to cause concurrent transfer of power to the load <NUM> from the AC power source <NUM> and the variably available power source <NUM> via the bypass circuit <NUM> and the first power conversion circuit <NUM>, respectively.

<FIG> illustrates a modular UPS system <NUM> according to some embodiments that provide such functionality. The UPS system <NUM> includes first and second power conversion modules <NUM>, <NUM> having a common architecture, including first and second converter units <NUM>, <NUM> linked by a DC bus <NUM>, a battery interface unit <NUM> for coupling a battery to the DC bus <NUM> and a module control unit <NUM>. The module control units <NUM> may be operatively associated with a system control circuit <NUM> that, for example, defines interoperation of the power conversion modules <NUM>, <NUM> in various operating modes as described below. The modules <NUM>, <NUM> may have the same or different form factors and/or capacities. For example, the modules <NUM>, <NUM> may have a common form factor and/or external connection configuration, and may be designed to be interchangeably installed in a system chassis.

The second power conversion module <NUM> is configured to provide on-line UPS operation, with power being selectively supplied to a load <NUM> from an AC power source <NUM> and one or more backup batteries <NUM>. The first power conversion module <NUM> is configured to provide an interface for a variably available power source <NUM> such as a photovoltaic source or wind power generator. The first converter unit <NUM> of the first power conversion module <NUM> may be configured to provide an appropriate conversion depending on the nature of the variably available power source <NUM>, which may be different from a conversion provided by the first converter unit <NUM> of the second power conversion circuit <NUM>. For example, the first converter unit <NUM> of the first power conversion module <NUM> may comprise respective active bridge circuit that is selectively configurable to operate as a rectifier or a DC/DC converter depending on, for example, control signals applied thereto by the module control unit <NUM>. One or more additional backup batteries may be coupled to the battery interface unit <NUM> of the first power conversion module <NUM>.

The control circuits of the UPS system <NUM> support a plurality of operating modes. As illustrated in <FIG>, when the AC power source <NUM> is operating within normal limits such that the second power conversion module <NUM> is bypassed, power is concurrently delivered to the load <NUM> from the AC power source <NUM> and the variably available power source <NUM> via the bypass circuit <NUM> and the first power conversion module <NUM>, respectively. In another mode illustrated in <FIG>, when the bypass circuit <NUM> is opened and on-line conversion is performed by the second power conversion module <NUM>, power is concurrently delivered to the load <NUM> from the AC power source <NUM> and the variably available power source <NUM> via the second power conversion module <NUM> and the first power conversion module <NUM>, respectively. As illustrated in <FIG>, when the AC power source <NUM> fails, power may be delivered to the load <NUM> from the one or more batteries <NUM> coupled to the second power conversion module <NUM> and from the variably available power source <NUM> via the second power conversion module <NUM> and the first power conversion module <NUM>, respectively. Additional power may be supplied by one or more batteries <NUM> coupled to the first power conversion module <NUM>.

According to additional examples, not covered by the claims, similar functionality may be provided by coupling a power conversion module that receives power from a variably available source to the output of a static switch. <FIG> illustrates a UPS system <NUM> including a static switch <NUM> configured to couple and decouple an AC power source <NUM> to and from a load <NUM>. A power conversion module <NUM> including components along the lines described above with reference to <FIG> is also coupled to the load <NUM> and is configured to transfer power from a variably available power source <NUM> to the load <NUM>. One or more batteries <NUM> are coupled to the battery interface unit <NUM> of the power conversion module <NUM>. The power conversion module <NUM> and the static switch <NUM> are cooperatively controlled by a system control circuit <NUM>.

A shown in <FIG>, when the AC power source <NUM> is in a normal condition, power may be concurrently supplied from the AC power source <NUM> and the variably available power source <NUM> via the static switch <NUM> and the power conversion module <NUM>, respectively. As shown in <FIG>, upon failure of the AC power source <NUM>, power may be delivered to the load <NUM> from the variably available power source <NUM> and the one or more batteries <NUM> via the power conversion module <NUM>.

Claim 1:
An uninterruptible power supply, UPS, system (<NUM>; <NUM>), comprising:
an AC input (<NUM>) configured to be coupled to an AC power source (<NUM>);
an AC output (<NUM>) configured to be coupled to a load (<NUM>);
a first power conversion module (<NUM>; <NUM>) comprising a first converter circuit (<NUM>; <NUM>) configured to receive power from a variably available power source (<NUM>), a second converter circuit (<NUM>; <NUM>) coupled to the AC output (<NUM>), and a first DC link (<NUM>; <NUM>) coupling the first and second converter circuits (<NUM>, <NUM>; <NUM>, <NUM>);
a second power conversion module (<NUM>; <NUM>) comprising an AC/DC converter circuit (<NUM>; <NUM>) coupled to the AC input (<NUM>), a DC/AC converter circuit (<NUM>; <NUM>) coupled to the AC output (<NUM>) and a second DC link (<NUM>) coupling the AC/DC converter circuit (<NUM>; <NUM>) to the DC/AC converter circuit (<NUM>; <NUM>), isolated from the first DC link (<NUM>; <NUM>);
a bypass circuit (<NUM>; <NUM>) configured to selectively couple and decouple the AC input (<NUM>) and the AC output (<NUM>); and
a control circuit (<NUM>; <NUM>) operatively associated with the first power conversion module (<NUM>; <NUM>), the second power conversion module (<NUM>; <NUM>) and the bypass circuit (<NUM>; <NUM>) and configured to support the following modes of operation:
concurrent transfer of power to the load (<NUM>) at the AC output (<NUM>) from the AC power source (<NUM>) and the variably available power source (<NUM>) via the bypass circuit (<NUM>) and the first power conversion module (<NUM>; <NUM>), respectively;
concurrent transfer of power to the load (<NUM>) at the AC output (<NUM>) from the variably available power source (<NUM>) and a first auxiliary power source coupled to the DC link of the first power conversion module (<NUM>; <NUM>);
concurrent transfer of power to the load (<NUM>) at the AC output (<NUM>) from the AC power source and the variably available power source via the second power conversion module (<NUM>; <NUM>) and the first power conversion module (<NUM>; <NUM>), respectively.