Power distribution systems using distributed current sensing

A system includes a plurality of power conversion devices, for example, uninterruptible power supply (UPS) devices, having inputs coupled in common to a power input line and each including a control circuit configured to operate the power conversion device responsive to a current sense signal at a current sense input thereof. The system further includes a first current transformer having a primary winding inductively coupled to the power input line, a current sense line coupled in series with a secondary winding of the first current transformer and a plurality of second current transformers, each including a primary winding inductively coupled to the current sense line and including respective secondary windings coupled to respective ones of the current sense inputs.

BACKGROUND

The inventive subject matter relates to power distribution and, more particularly, to power distribution systems including multiple power conversion devices.

Uninterruptible power supply (UPS) devices are commonly used to provide uninterrupted power in critical applications, such as industrial, medical and data processing applications. For example, in data center applications, multiple UPS devices may have inputs coupled in common to an AC power source (e.g., a utility input), and may provide uninterrupted power to groups of equipment racks housing servers, routers and other network equipment. Similar arrangements of UPS devices may be used in telecommunications installations.

Recently developed UPS devices include power conversion circuitry that may perform functions such as harmonic compensation. The control circuitry for such functions may rely on sensing various input and output voltages and currents. UPS systems capable of harmonic compensation are described, for example, in U.S. Pat. No. 6,295,215 to Faria et al. and U.S. Pat. No. 6,906,933 to Taimela.

SUMMARY

In some embodiments of the inventive subject matter, a system includes a plurality of power conversion devices having inputs coupled in common to a power input line and each including a control circuit configured to operate the power conversion device responsive to a current sense signal at a current sense input thereof. The system further includes a first current transformer having a primary winding inductively coupled to the power input line, a current sense line coupled in series with a secondary winding of the first current transformer and a plurality of second current transformers, each including a primary winding inductively coupled to the current sense line and including respective secondary windings coupled to respective ones of the current sense inputs. In some embodiments, the plurality of power conversion devices may include a plurality of uninterruptible power supply devices. The second current transformers may be co-located with the uninterruptible power supply devices and/or positioned remotely from the uninterruptible power supply devices.

In further embodiments, an uninterruptible power supply apparatus includes a plurality of uninterruptible power supply modules, each having a current sense input and at least one current transformer having a primary winding configured to be inductively coupled to a secondary winding of an external current transformer and a secondary winding coupled to the current sense inputs of the uninterruptible power supply modules. The at least one current transformer may include a plurality of current transformers and secondary windings of respective ones of the plurality of current transformers may be coupled to current sense inputs of respective ones of the uninterruptible power supply modules. The apparatus may further include a bypass circuit configured to bypass the plurality of current transformers. The uninterruptible power supply modules may be configured to provide harmonic compensation responsive to a current sense signal produced by the at least one current transformer.

In additional embodiments of the inventive subject matter, a system includes a first current transformer including a primary winding inductively coupled to a power line of a power distribution system, a current sense line coupled in series with a secondary winding of the first current transformer and a plurality of second current transformers, each second current transformer including a primary winding inductively coupled to the current sense line. Respective ones of the second current transformers have a secondary winding configured to be coupled to respective current monitoring devices.

DETAILED DESCRIPTION OF EMBODIMENTS

Specific 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.

As will be appreciated by one of skill in the art, the inventive subject matter may be embodied as systems and methods. 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 diagrams of systems and methods according to various embodiments of the inventive subject matter. It will be understood that each block of the diagrams, and combinations of blocks in the diagrams, 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 diagrams.

FIG. 1illustrates a power distribution system100. The system100includes a plurality of power conversion devices110, e.g., uninterruptible power supply (UPS) devices, coupled to a power distribution network30. Each of the power conversion devices110includes a control circuit112, which may be configured to perform various control, monitoring and other functions associated with operations of the power conversion devices110. For example, for power conversion devices110in the form of UPS devices, the control circuits122may control UPS system components, such as rectifiers, inverters, bypass circuits and the like.

As illustrated, a first current transformer120is configured to sense a current imainin an input line30aof the power distribution network30. In particular, a primary winding of the first current transformer120may be inductively coupled to the input line30a, inducing a current isensein a secondary winding of the first current transformer120that is connected in series with a current sense line125.

Respective second current transformers130are operatively coupled to the current sense line125and to respective ones of the control circuits112of the power conversion devices110. In particular, primary windings of the second current transformers130may be inductively coupled to the current sense line125, such that the sense current isensein the current sense line125induces corresponding currents in the secondary windings of the second current transformers130. These secondary winding currents may be sensed by the respective control circuits112. The second current transformers130may be co-located with the power conversion devices110and/or may remotely located.

FIG. 2illustrates a power distribution system200according to further embodiments. The power distribution system200includes a plurality of modular UPS assemblies210coupled to a power distribution network30. Each of the modular UPS assemblies210includes a plurality of uninterruptible power modules (UPMs)212, which may include, for example, a combination of an input rectifier and output inverter linked by a DC bus. The UPMs212may include additional circuitry, such as battery interface and bypass circuitry.

Current sensing circuitry includes a first current transformer220configured to sense a current imainin an input line30aof the power distribution network30. Along lines described above with reference toFIG. 1, a primary winding of the first current transformer220may be inductively coupled to the input line30a, inducing a current isensein a secondary winding of the first current transformer130that is connected in series with a current sense line225.

Second current transformers214of the UPS assemblies210are operatively coupled to the current sense line225, i.e., have primary windings inductively coupled the current sense line225. Secondary windings of the respective second transformers214are coupled to respective ones of the UPMs212, such that each UPM212may sense the current isense. As further illustrated, bypass circuits216may be provided to bypass the second current transformers214associated with the individual UPS assemblies210for maintenance and other purposes. The bypass circuit216may include, for example, mechanical and/or solid state switching elements and/or other means for providing an interruptible connection, such as wire jumpers. As further illustrated, protective elements250(e.g., zener diodes or varistors) may be coupled to the secondary windings of the first and second current transformers220,214.

FIG. 3illustrates a power distribution system300with an alternative arrangement. The power distribution system300includes a plurality of modular UPS assemblies310coupled to a power distribution network30. Each UPS assembly310includes a plurality of UPMs312. A first current transformer220senses an input current imainin an input line30aof the power distribution network30, generating a sense current isensein a current sense line225. A current sense circuit320includes second current transformers324located apart from the UPS assemblies310(e.g., at a centralized location). Respective bypass circuits326may be configured to bypass respective groups of the second current transformers314associated with respective ones of the UPS assemblies310. The second current transformers314are configured to sense a sense current isenseand to provide current sense signals to respective UPMs312of the UPS assemblies310. It will be appreciated that, in some embodiments, the arrangements inFIGS. 2 and 3may be combined, e.g., some UPS devices may use co-located current transformers as shown inFIG. 2, while others use remote current transformers as shown inFIG. 3.

FIG. 4illustrates an example of a UPM400. The UPM400includes a rectifier circuit410having an input configured to be coupled to an AC power distribution network and an output coupled to an inverter circuit420by a DC bus415. An output of the inverter circuit420is configured to be coupled to a load. A battery interface circuit430is also coupled to the DC bus415, and may be used to provide auxiliary power to the inverter circuit410from a battery in case of a failure of the AC power at the input of the rectifier circuit410.

A control circuit440controls operations of the rectifier circuit410, the inverter circuit420and the battery interface circuit430. As shown, the control circuit440may control these UPM components responsive to a sense current isense, which, as explained above, may be representative of an input current of the power distribution network. This current sensing may be used, for example, to control the rectifier circuit410and/or the inverter circuit420to implement, for example, harmonic compensation. For example, when a bypass circuit460is used to bypass the inverter circuit420in a high-efficiency mode of operation, the control circuit440may operate the inverter circuit420responsive to the sense current isenseto t provide harmonic compensation while power is directly delivered to the load from the power distribution network.

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.