WO2014209377A1

WO2014209377A1 - Uninterruptible power supply control

Info

Publication number: WO2014209377A1
Application number: PCT/US2013/048667
Authority: WO
Inventors: Kristian BUDDE
Original assignee: Schneider Electric It Corporation
Priority date: 2013-06-28
Filing date: 2013-06-28
Publication date: 2014-12-31

Abstract

At least some aspects and embodiments are directed toward a UPS system including an input configured to receive input power from an input power source, an output configured to provide output power to a load, and a plurality of units coupled to the input and the output, each of the plurality of units configured to provide an output contributing to the output power, each of the plurality of units comprising at least one temperature sensor. The UPS also includes a main controller coupled to the plurality of units, the main controller configured to receive, from the temperature sensors, information relating to temperatures of each of the plurality of units, calculate at least one average temperature based on the temperatures of each of the plurality of units, and provide the at least one average temperature to each of the plurality of units.

Description

UNINTERRUPTIBLE POWER SUPPLY CONTROL

BACKGROUND

1. Field of the Disclosure

Embodiments of the present disclosure relate generally to systems and methods for providing uninterruptible power. More specifically, embodiments relate to adaptive controllers for uninterruptible power supplies (UPS). 2. Description of Background

The use of uninterruptible power supplies having back-up systems to provide regulated, uninterrupted power for sensitive and/or critical loads, such as computer systems and other data processing systems, is known. FIG. 1 shows a typical, single phase, on-line UPS 10 used to provide regulated, uninterrupted power. The UPS 10 includes an input circuit breaker/filter 12, a rectifier 14, a control switch 15, a controller 16, a battery 18, an inverter 20 and an isolation transformer 22. The UPS also includes an input 24 for coupling to an AC power source, and an outlet 26 for coupling to a load.

The UPS 10 operates as follows. The circuit breaker/filter 12 receives input AC power from the AC power source through the input, filters the input AC power and provides filtered AC power to the rectifier 14. The rectifier 14 rectifies the input voltage. The control switch 15 receives the rectified power and also receives DC power from the battery 18. The controller 16 determines whether the power available from the rectifier 14 is within predetermined tolerances, and if so, controls the control switch 15 to provide the power from the rectifier 14 to the inverter 20. If the power from the rectifier 14 is not within the predetermined tolerances, which may occur because of "brown out" or "black out" conditions, or due to power surges, then the controller 16 controls the control switch 15 to provide the DC power from the battery 18 to the inverter 20.

The inverter 20 of the UPS 10 receives DC power and converts the DC power to AC power and regulates the AC power to predetermined specifications. The inverter 20 provides the regulated AC power to the isolation transformer 22. The isolation transformer 22 is used to increase or decrease the voltage of the AC power from the inverter 20 and to provide isolation between a load and the UPS 10. The isolation transformer 22 can be an optional device, the use of which is typically dependent on UPS output power specifications. Depending on the capacity of the battery 18 and the power requirements of the load, the UPS 10 can provide power to the load during brief power source dropouts or for extended power outages.

UPS systems may be configured to provide greater capacity and/or reliability. For example, to provide enhanced scalability and/or redundancy, two or more UPSs may be electrically connected to form a single parallel UPS system with one output. In such a system, the combination of UPSs may provide increased power capacity to a load attached to the parallel UPS system. Also, if a first one of the UPSs coupled in parallel fails, the second one of the UPSs coupled in parallel may backup for the failed UPS. Modular UPS systems having redundant control features also exist.

SUMMARY

At least some aspects and embodiments are directed toward a UPS system including an input configured to receive input power from an input power source, an output configured to provide output power to a load, and a plurality of units coupled to the input and the output, each of the plurality of units configured to provide an output contributing to the output power, each of the plurality of units comprising at least one temperature sensor. The UPS also includes a main controller coupled to the plurality of units, the main controller configured to receive, from the temperature sensors, information relating to temperatures of each of the plurality of units, calculate at least one average temperature based on the temperatures of each of the plurality of units, and provide the at least one average temperature to each of the plurality of units. In some embodiments, each of the plurality of units comprises a local controller configured to receive the at least one average temperature, compare the at least one average temperature to the temperature of the unit, and based on the comparison, adjust the output of the unit.

In some embodiments, the local controller of each of the plurality of units is configured to adjust the output of the unit by at least linearly increasing the output based on a positive difference between the at least one average temperature and the temperature of the unit.

In some embodiments, the local controller of each of the plurality of units is configured to adjust the output of the unit by at least linearly decreasing the output based on a negative difference between the at least one average temperature and the temperature of the unit.

In some embodiments, the local controller is further configured to decrease the output based on a threshold temperature of the unit.

In some embodiments, the output power has three phases, the output of each of the plurality of units contributes to one of the three phases, and the at least one average temperature includes an average temperature of the plurality of units contributing to each of the three phases.

In some embodiments, each of the plurality of units includes at least a first temperature sensor measuring a temperature of an inverter and a second temperature sensor measuring a temperature of a charger. In some embodiments, the at least one average temperature includes at least a first average temperature corresponding to an average of the temperatures of the inverters of the plurality of units and a second average temperature corresponding to an average of the temperatures of the chargers of the plurality of units. In some embodiments, each of the plurality of units provides a second output to the charger, and wherein the local controller is further configured to adjust the second output based on a comparison of the second average temperature and the local temperature of the charger. Aspects also include a method of controlling a UPS system including a main controller and a plurality of units each comprising at least one temperature sensor. The method includes receiving, from the temperature sensors, information relating to temperatures of each of the plurality of units, calculating at least one average temperature based on the temperatures of each of the plurality of units, and providing the at least one average temperature to each of the plurality of units. In some embodiments, each of the plurality of units comprises a local controller, and the method further includes receiving, at the local controller, the at least one average temperature, comparing, at the local controller, the at least one average temperature to the temperature of the unit, and based on the comparison, adjusting, by the local controller, the output of the unit.

In some embodiments, the method further includes adjusting, by the local controller, the output of the unit by at least linearly increasing the output based on a positive difference between the at least one average temperature and the temperature of the unit.

In some embodiments, the method further includes adjusting, by the local controller, the output of the unit by at least linearly decreasing the output based on a negative difference between the at least one average temperature and the temperature of the unit.

In some embodiments, the method further includes decreasing, by the local controller, the output based on a threshold temperature of the unit.

In some embodiments, the output power has three phases, the output of each of the plurality of units contributes to one of the three phases, and the calculating at least one average temperature based on the temperatures of each of the plurality of units includes calculating an average temperature of the plurality of units contributing to each of the three phases.

In some embodiments, the receiving, from the temperature sensors, information relating to temperatures of each of the plurality of units includes receiving information from a first temperature sensor measuring a temperature of an inverter and from a second temperature sensor measuring a temperature of a charger. In some embodiments, the calculating at least one average temperature based on the temperatures of each of the plurality of units includes calculating a first average temperature corresponding to an average of the temperatures of the inverters of the plurality of units and a second average temperature corresponding to an average of the temperatures of the chargers of the plurality of units. In some embodiments, the method further includes providing, by each of the plurality of units, a second output to the charger and adjusting, by the local controller, the second output based on a comparison of the second average temperature and the local temperature of the charger.

Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. Embodiments disclosed herein may be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein, and references to "an embodiment," "some embodiments," "an alternate embodiment," "various embodiments," "one embodiment" or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the disclosure. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures:

FIG. 1 is a block diagram of a prior art UPS system; FIG. 2 is a front view of an example modular UPS system according to aspects of the present disclosure;

FIG. 3 is a functional block diagram of an example power module used in the modular UPS system of FIG. 2 according to aspects of the present disclosure;

FIG. 4 is a block diagram of an example parallel UPS system according to aspects of the present disclosure;

FIG. 5A is block diagram of an example modular UPS system according to aspects of the present disclosure;

FIG. 5B is block diagram of an example modular UPS system according to aspects of the present disclosure;

FIG. 6 is a block diagram of a portion of an example modular UPS system according to aspects of the present disclosure;

FIG. 7 is a graph of an example model for adjusting load on modules of a modular UPS system according to aspects of the present disclosure; and

FIG. 8 is a flow chart of an example process for adjusting load on modules of a modular UPS system according to aspects of the present disclosure.

DETAILED DESCRIPTION

A UPS system running at 100% power capacity is able to support a load equivalent to 100% of the system's power rating. Being ready to handle this maximum load requires that all units, such as power modules of a modular UPS system, are running. DC busses typically are charged and all inverter components are switching. However, maximum power availability may only be continuously needed in very few systems. Often, maximum power availability is not required and a UPS may run at 50-60% load at times. For example, a UPS system may be acquired to fit a specific predefined setup, which could be a data center installation where a given load of lOOKVA is being used and the UPS is dimensioned to fit a load of 200KVA to allow for future expansions. In another example, a UPS in an office environment may have a utilization of 80% during office hours and the utilization may drop to 10% after office hours.

At least some aspects and embodiments are directed to methods and apparatuses for adaptively controlling UPS systems of the type having a plurality of units, such as a modular UPS system or a parallel UPS system, as will be described in further detail below. In one example, a unit may include a power module of a modular UPS system. In another example, a unit may include a UPS of a parallel UPS system.

In some embodiments, when the load is less than the power capacity of the modular UPS system, the load can be distributed among the plurality of power modules of the modular UPS system. In some embodiments, the UPS includes a controller that distributes the load among the plurality of power modules. The controller can distribute the load based on component stress levels. For example, the controller can determine the thermal stress on each of the power modules and adjust the load on the power modules based on the determination. In some embodiments, the UPS can distribute the load among the power modules to achieve a more uniform thermal stress across the power modules of the UPS.

One or more features disclosed herein may be implemented in one or more controllers or apparatuses configured to control one or more UPS systems. In various embodiments, controllers disclosed herein may be included in one or more UPS systems or may be separate from one or more UPS systems being controlled. Example UPS systems upon which various aspects may be implemented and example UPS systems which may be controlled based on various aspects are discussed in more detail below.

It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, elements and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiment.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Any references to embodiments or elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality of these elements, and any references in plural to any embodiment or element or act herein may also embrace embodiments including only a single element. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms.

FIG. 2 shows a front view of a modular UPS system 200 in accordance with some embodiments of the present disclosure. The modular UPS system 200 includes a number of components housed within a chassis 202. In some embodiments, the primary components of the UPS system 200 include power modules 204, battery modules 206, an AC distribution module 208, a display module 212, a controller 214A, a redundant controller 214B and a communications module. In some embodiments, the controller 214A may be a main intelligence module and the redundant controller 214B may be a redundant intelligence module. The controller 214A and the redundant controller 214B may be configured to control the UPS system 200 according to one or more features disclosed herein. In other embodiments, the UPS system 200 may include a single controller according to aspects disclosed herein.

The communications module is not visible in FIG. 2, but in one embodiment the communications module is disposed in the frame behind the controller 214A and the redundant controller 214B. The communications module may provide the interface between the controller 214A and/or the redundant controller 214B and a number of components such as external devices and the display module 212. The display module 212 provides a user interface to the UPS system 200. The UPS system 200 of FIG. 2 includes five power modules 204 and four battery modules 206. The particular number of power modules and battery modules used in a particular application may be selectable by a user depending on power and backup time desired.

In one embodiment, the power modules 204 are substantially identical, and each performs the functions of an uninterruptible power supply (without the battery) under the control of the controller 214A or the redundant controller 214B. FIG. 3 is a functional block diagram of one of the power modules 204 showing the major functional blocks and interconnections. In some embodiments, the power module 204 includes an input power stage 336, an output power stage 338, a controller 340 and a battery charging circuit 342. The input power stage 336 includes an AC/DC converter 344, a DC/DC converter 346, and a control switch 348. In some embodiments, the power module 204 includes two temperature sensors 350, 352. In some embodiments, the power module 204 includes two heat sinks 354, 356. A first heat sink 354 is configured to cool the input power stage 336 and the battery charging circuit 342, and a second heat sink 356 is configured to cool the output power stage 338, such as an inverter included in the output power stage 338. In some embodiments, each of the temperature sensors 350, 352 are coupled to each of the heat sinks 354, 356, respectively. In other embodiments, the power module 204 includes one temperature sensor or more than two temperature sensors.

In some embodiments, the AC/DC converter 344 receives input AC power and converts the input AC power to DC power. The DC/DC converter 346 receives DC battery power and modifies the voltage level to produce DC power at substantially the same voltage level as that generated by the AC/DC converter 344. The control switch 348, under the control of the controller 340, selects either the DC power from the AC/DC converter 344 or the DC power from the DC/DC converter 346 as the input power to the output stage 338. In one embodiment, the decision to switch to battery or line as the source power may be made individually by each power module. The output power stage 338 generates output AC power from the DC power received from the input power stage 336. The battery charger circuit 342 generates charge current using the DC power from the AC/DC converter 344 to charge the battery modules 206. The controller 340 controls operation of the input power stage 336, the output power stage 338 and the battery charging circuit 342. In addition, the controller 340 provides the primary interface in the power module to the controller 214A and the redundant controller 214B. The controller 340 is also configured to hibernate, turn off, activate, turn on, and adjust a load on the power module 204, for example based on input received from a master controller of the UPS system 200, such as the controller 214A. The controller 340 is also configured to receive temperature information from the temperature sensors 350, 352 of the power module 204.

In other embodiments, two or more UPSs may be electrically connected to form a single parallel UPS system with one output configured to be coupled to a load. In some embodiments of parallel UPS systems, the UPSs may communicate with each other directly (e.g., via a bus) to manage their joint operation in the parallel UPS system. In such a system, before the parallel UPS system is able to operate, the UPSs may exchange initial startup information to define how the UPSs will interact. In other embodiments of parallel UPS systems, the UPSs may utilize a master/controlled approach. In one master/controlled approach, a UPS is designated as a master UPS and the other UPSs are designated as controlled UPSs. The master UPS monitors the output voltage of its inverter (i.e., the output of the master UPS) and in response, generates an inverter current reference signal. Based on the inverter current reference signal, the master UPS controls the inverter to regulate its output. The master UPS also provides the inverter current reference signal to the controlled UPSs. The controlled UPSs share the load current based on the inverter current reference signal. Therefore, the master UPS controls the output of the entire parallel UPS system.

A parallel UPS system may be configured according to one or more features disclosed herein. In some embodiments, the parallel UPS system may include a master UPS having a controller configured according to aspects disclosed herein. The controller of the master UPS system may be coupled to one or more controlled UPSs and may be configured to provide control signals to hibernate, activate, turn on, turn off, and adjust loads for one or more controlled UPSs.

FIG. 4 is a block diagram of one example of a parallel UPS system 400. The parallel

UPS system 400 includes a first UPS 402, a second UPS 404, and a third UPS 406, each coupled in parallel to provide power to a load bus 452 via a single output 454. In other embodiments, the UPS system 400 may include more or less than three UPSs. Each UPS 402, 404, 406 is coupled to input AC mains line 456. Within each UPS 402, 404, 406 a Power Factor Correction (PFC) circuit 458 is coupled to the AC mains line 456 and a battery 460. An inverter 462 is coupled to the PFC 458 and to the output 454 via an inverter relay 464. Each UPS 402, 404, 406 also includes a bypass line coupled between the input AC mains line 456 and the output 454 via a bypass relay 468. According to one embodiment, each UPS 402, 404, 406 also includes a backfeed relay 470 coupled to the input AC mains line 456 to provide backfeed protection. Input AC power is provided by an external power source (e.g., a utility power source) to the input AC mains 456 and to each UPS 402, 404, 406. The PFC 458 of each UPS 402, 404, 406 converts the input AC power to DC power and provides the DC power to the inverter 462. According to one embodiment, where input AC power provided by the external power source is inadequate, each UPS 402, 404, 406 may instead receive DC power from a battery 460. The PFC 458 regulates the DC power from the battery and provides the DC power to the inverter 462.

The inverter 462 converts and regulates the received DC power into regulated AC power which is provided to the load bus 452. When regulation by the inverter 462 is not required or there is a problem with the inverter 462, unregulated power may be provided directly from the input AC mains line 456 to the output 454 via the bypass line 466. The inverter relay 464 and the bypass relay 468 are selectively controlled to determine whether each UPS 402, 404, 406 is operating regularly or in bypass mode.

According to one embodiment, one of the UPSs 402, 404, 406 is designated as the master UPS and controls the output of each one of the controlled UPSs inverters 462 to ensure that appropriate power is provided to the load bus 452 from each UPS. The master UPS may include a controller configured to hibernate, turn off, activate, turn on, and adjust a load for one or more controlled UPSs.

FIGS. 5A and 5B are block diagrams of an example modular UPS 500. In this example, the modular UPS 500 includes thirty power modules 502A-502J, 504A-504J, 506A-506J controlled by a controller 514. The power modules, 502, 504, 506 are coupled to the controller 514. The power modules 502, 504, 506 are also coupled to an input circuit and a battery charging circuit 536. The input circuit can include a rectifier that receives input AC power. In some embodiments, the modular UPS 500 is a three-phase UPS. The top row of power modules 502A, 502B, 502C, 502D, 502E, 502F, 502G, 502H, 5021, 502J can be configured to supply phase one of the three-phase UPS. The middle row of power modules 504A, 504B, 504C, 504D, 504E, 504F, 504G, 504H, 5041, 504J can be configured to supply phase two of the three-phase UPS. The bottom row of power modules 506A, 506B, 506C, 506D, 506E, 506F, 506G, 506H, 5061, 506J can be configured to supply phase three of the three-phase UPS. In some embodiments, each of the power modules is configured to charge a common battery with a common charge current reference.

Each of the power modules 502A-502J, 504A-504J, 506A-506J includes an inverter, which can receive varying loads, controlled by the controller 514. The loads on the inverters of the power modules 502, 504, 506 can vary individually or by phase. For example, the ten power modules of each phase can share a load equally, while the loads can differ between phases. Alternatively or additionally, each of the power modules 502, 504, 506 can receive different loads from one or more of the other power modules. In some embodiments, each of the power modules 502, 504, 506 includes two heat sinks. The first heat sink is configured to cool the input stage and the charging circuit 536. The second heat sink is configured to cool the inverter. In some embodiments, a temperature sensor is coupled to each of the heat sinks and provides temperature information to the controller 514. Each power module can provide a first and second temperature (Tl and T2) relating to the charger and the inverter, respectively. For example, power module Al 502A can provide information to the controller 514 showing the temperature of its charger, Tl, is 77 degrees Celsius (C) and the temperature of its inverter, T2, is 76 degrees Celsius. FIG. 5B shows shading gradients that depict an example temperature gradient across the power modules 502, 504, 506. In this example, the top left corner of the modular UPS 500 is the hottest, showing Tl at 77C and T2 at 76C for power module Al 502A. The bottom right corner of the modular UPS 500 is the coolest, showing Tl at 51C and T2 at 49C for power module 13 5061.

In some embodiments, the controller 514 can receive temperature information from each of the power modules 502, 504, 506 and calculate an average temperature. For example, the controller 514 can calculate an average temperature for each of the phases by computing an arithmetic mean of the temperatures of each of the ten power modules supplying each phase. For example, the controller 514 can calculate the average of the charger temperatures Tl for each of the power modules 502A-502J that supply phase one of the three-phase modular UPS 500. In some embodiments, other calculations can be used to compute an average temperature. For example, the average temperature can be determined using a weighted average. The weighted average can be weighted corresponding to differences between the power modules, such as maximum rated load of the power modules. Similarly, the controller 514 can calculate an average inverter temperature T2 for phase one of the modular UPS 500 by averaging the T2 temperature values of the power modules 502A-502J. The controller 514 can calculate average charger and inverter temperatures for each of the three phases.

In some embodiments, the controller 514 can compare the temperatures of each of the power modules to the average temperature. In some embodiments, the average temperature can be an average temperature of all the power modules of the modular UPS 500. In some embodiments, the average temperature can include a subset of the power modules. In some embodiments, separate average temperatures can be calculated for each phase. The controller 514 can compare the temperature of the power module to the average temperature of the phase for which the power module is providing power. For example, the controller 514 can compare the temperature of power module Al 502A to the average temperature for the power modules 502A-502J supplying phase one.

Based on the comparison, the controller 514 can adjust the load on the power module.

For example, if the temperature of the power module is higher than the average temperature for the phase, the controller 514 can lessen the load powered by the power module. Conversely, if the temperature of the power module is lower than the average temperature, the controller 514 can increase the load powered by the power module. In some embodiments, the amount of increase or decrease in load assigned by the controller 514 to the power module can be based on the difference in the temperature of the power module and the average temperature. In some embodiments, the adjusting of the loads on the power modules can be effected by the power modules. FIG. 6 shows a block diagram of a portion 600 of an example modular UPS. The UPS portion 600 includes a main controller 602, a communication layer 606, and a power module 608. While the UPS portion 600 shows one power module 608, the UPS can have a plurality of power modules, with a similar interface between the main controller 602, the communication layer 606, and the plurality of power modules. In some embodiments, the main controller 602 includes an inverter voltage regulator 604, which receives a system reference voltage level and a system output voltage measurement. The inverter voltage regulator 604 generates a reference current, which the inverter voltage regulator 604 transmits to the power module 608, via the communication layer 606. The communication layer 606 can also receive an average temperature, for example, the average temperature of the UPS, the average temperature of some or all of the power modules, and/or the average temperature of each of the phases of a three-phase UPS. The communication layer 606 can relay the reference current and the average temperature to the power module 608. The power module 608 can include a local current adjustment module 610, which receives the reference current and the average temperature from the communication layer 606. The local current adjustment module 610 can also receive temperature information about the power module 608. The local current adjustment module 610 can compute a difference between the average temperature and the power module temperature and generate a local reference current.

In some embodiments, the power module 608 can also include a current regulator 612, which receives the local reference current from the local current adjustment module 610 and outputs instructions to hardware of the power module 608 to produce the current indicated by the local reference current.

In some embodiments, the adjustment made to the output of the power module, for example, by the local current adjustment module 610, is determined based on the difference in the temperature between the power module and the average temperature. For example, FIG. 7 shows a graph 700 of an example algorithm for adjusting the load on the inverter of the power module based on the temperature difference. The x-axis 702 shows the temperature difference between the temperature of the inverter of the power module (T2) and the average temperature. The y-axis 704 shows the inverter load adjustment. In some embodiments, the percentage inverter load adjustment corresponds to the percentage load level placed on the power module. For example, if the load level on the power module is 50%, a 10% increase can mean raising the load level to 60%. In some embodiments, the percentage increase can correspond to a percentage of the load level. For example, if the load level on the power module is 50%, a 10% increase can mean raising the load level 10% of 50%, to 55%.

In some embodiments, the load on the inverter can be adjusted by a percentage corresponding to the thermal difference based on a linear model. For example, if the power module is at a temperature that is 5C higher than the average temperature, the load on the power module inverter can be reduced by 5%. In some embodiments, the percentage adjustment can include threshold limits. For example, the graph 700 shows the percentage adjustment limited to +/-10%, even if the temperature difference is greater than IOC. The algorithm can be applied to each of the power modules to adjust the load on each of the power modules based on the thermal load on the power modules. In some embodiments, as the loads on the power modules are adjusted based on an average thermal load, as loads are decreased on some power modules, a relatively similar corresponding increase can be expected on other power modules and/or an aggregate of other power modules. In some embodiments, adjusting the loads according to this or another appropriate algorithm can eventually provide for a more thermally uniform system. In some embodiments, the adjustment percentage can have no threshold limits. In some embodiments, power modules can be permitted to exceed a maximum rated load (i.e. output greater than 100%) for a period of time.

A similar algorithm can be used to adjust the load on the charger, based on the differences in charger temperature (Tl) of the power module and an average charger temperature. In some embodiments, the adjustment of the charger load can be greater than the adjustment of the inverter load. For example, in some embodiments, the charger load can be distributed between all the power modules to an extent permitted by converter hardware. An example algorithm for adjusting the charger load on the power modules can be a percentage corresponding to twice the degrees Celsius difference in temperature between the power module and the average temperature. For example, if a power module provides a charger temperature that is 3C cooler than the average temperature for the chargers on the UPS, the controller can adjust the charger load on the power module by increasing the charger load 6%. In some embodiments, a threshold limit can be placed on the adjustment percentage, such as +/- 20%. In some embodiments, power modules can be permitted to exceed a maximum rated threshold for a period of time. In some embodiments, a current limitation can be included in the thermal adjuster to prevent exceeding of a maximum current allowed. The current limiter can be based on a root mean square (RMS) calculation of the charger (or inverter) current.

FIG. 8 shows an example process 800, which can be executed on the modular UPS 200, for adjusting loads on power modules based on thermal load. The process 800 starts at act 802 with each power module measuring temperatures of local heat sinks. In some embodiments, each power module has two heat sinks, one for a charger and one for an inverter of the power module. In other embodiments, each power module has one heat sink. In other embodiments, each power module has more than two heat sinks.

At act 804, each power module transmits the measured temperatures to a main controller. At act 806, the main controller calculates an average temperature. In some embodiments, the average temperature is a system average of all the power modules of the UPS. In some embodiments, the average temperature is an average of the temperatures of the power modules supplying power to each phase. In some embodiments, the average inverter temperature can be calculated differently than the average charger temperature. At act 808, the main controller transmits the average temperature to each of the power modules. At act 810, each power module calculates the difference between the local temperature of the power module and the average temperature received from the main controller. In some embodiments, an inverter temperature and a charger temperature can be compared to one overall system average temperature that includes inverter and charger temperatures of each of the power modules. In some embodiments, separate average temperatures are provided for the inverters and the chargers. In some embodiments, separate average temperatures are provided for each of the three phases of a three-phase UPS.

At act 812, each power module adjusts a local current reference based on the thermal difference between the power module and the average temperature. If the power module is at a higher temperature than the average, the power module can decrease the current reference to decrease the load on the power module. Conversely, if the power module is at a lower temperature than the average, the power module can increase the current reference to increase the load on the power module. In some embodiments, the amount of adjustment can directly correlate to the amount of thermal difference.

The process 800 can be repeated to update the adjustments at each power module to achieve a more thermally uniform UPS. The rate of update can be configured to match the dynamic of the thermal system (e.g., 1 hertz).

In some embodiments, the power modules can also be limited by a threshold temperature. For example, the charger can have a maximum allowed charge current at predetermined temperatures. For example, the charger can be allowed 100% load up to 70C, at which point the maximum allowed charge can decrease linearly to 0% at 80C. Reducing the maximum allowed charge current can provide a method of controlling internal temperature of the UPS, ensuring load supply at the expense of charge power.

In some embodiments, the thermal loads on each of the power modules can be imbalanced due to system overload, high ambient temperature, air flow problems, and other reasons. The load on the UPS can be distributed based on the thermal load, independent of the cause of the imbalance. In some embodiments, the redistribution based on thermal load can allow the UPS to run for as hard as possible for as long as possible.

In some embodiments, a different number of temperature sensors can be used for each power module in other appropriate locations on the power modules.

Various aspects and functions described herein may be implemented in one or more controllers or apparatuses configured to control one or more UPS systems. In various embodiments, controllers disclosed herein may be included in one or more UPS systems or may be separate from one or more UPS systems being controlled.

Furthermore, various aspects and functions described herein in accord with the present disclosure may be implemented as hardware, software, or a combination of hardware and software on one or more computer systems. The one or more computer systems may be configured to communicate with the one or more UPS systems being controlled. There are many examples of computer systems currently in use. Some examples include, among others, network appliances, personal computers, workstations, mainframes, networked clients, servers, media servers, application servers, database servers, web servers, and virtual servers. Other examples of computer systems may include mobile computing devices, such as cellular phones and personal digital assistants, and network equipment, such as load balancers, routers and switches. Additionally, aspects in accord with the present invention may be located on a single computer system or may be distributed among a plurality of computer systems connected to one or more communication networks.

For example, various aspects and functions may be distributed among one or more computer systems configured to provide a service to one or more client computers, or to perform an overall task as part of a distributed system. Additionally, aspects may be performed on a client-server or multi-tier system that includes components distributed among one or more server systems that perform various functions. Thus, the invention is not limited to executing on any particular system or group of systems. Further, aspects may be implemented in software, hardware or firmware, or any combination thereof. Thus, aspects in accord with the present invention may be implemented within methods, acts, systems, system placements and components using a variety of hardware and software configurations, and the invention is not limited to any particular distributed architecture, network, or communication protocol. Furthermore, aspects in accord with the present invention may be implemented as specially- programmed hardware and/or software.

Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the disclosure. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the disclosure should be determined from proper construction of the appended claims, and their equivalents.

What is claimed is:

Claims

1. An uninterruptible power supply (UPS) system comprising:

an input configured to receive input power from an input power source;

an output configured to provide output power to a load;

a plurality of units coupled to the input and the output, each of the plurality of units configured to provide an output contributing to the output power, each of the plurality of units comprising at least one temperature sensor;

a main controller coupled to the plurality of units, the main controller being configured to:

receive, from the temperature sensors, information relating to temperatures of each of the plurality of units;

calculate at least one average temperature based on the temperatures of each of the plurality of units; and

provide the at least one average temperature to each of the plurality of units.

2. The UPS system of claim 1, wherein each of the plurality of units comprises a local controller configured to:

receive the at least one average temperature;

compare the at least one average temperature to the temperature of the unit; and based on the comparison, adjust the output of the unit.

3. The UPS system of claim 2, wherein the local controller of each of the plurality of units is configured to adjust the output of the unit by at least linearly increasing the output based on a positive difference between the at least one average temperature and the temperature of the unit.

4. The UPS system of claim 2, wherein the local controller of each of the plurality of units is configured to adjust the output of the unit by at least linearly decreasing the output based on a negative difference between the at least one average temperature and the temperature of the unit.

5. The UPS system of claim 2, wherein the local controller is further configured to decrease the output based on a threshold temperature of the unit.

6. The UPS system of claim 2, wherein the output power comprises three phases;

the output of each of the plurality of units contributes to one of the three phases; and the at least one average temperature comprises an average temperature of the plurality of units contributing to each of the three phases.

7. The UPS system of claim 2, wherein each of the plurality of units comprises at least a first temperature sensor measuring a temperature of an inverter and a second temperature sensor measuring a temperature of a charger.

8. The UPS system of claim 7, wherein the at least one average temperature comprises at least a first average temperature corresponding to an average of the temperatures of the inverters of the plurality of units and a second average temperature corresponding to an average of the temperatures of the chargers of the plurality of units.

9. The UPS system of claim 8, wherein each of the plurality of units provides a second output to the charger, and wherein the local controller is further configured to adjust the second output based on a comparison of the second average temperature and the local temperature of the charger.

10. A method of controlling a UPS system comprising a main controller and a plurality of units each comprising at least one temperature sensor, the method comprising:

receiving, from the temperature sensors, information relating to temperatures of each of the plurality of units;

calculating at least one average temperature based on the temperatures of each of the plurality of units; and

providing the at least one average temperature to each of the plurality of units.

11. The method of claim 10, wherein each of the plurality of units comprises a local controller, and the method further comprising:

receiving, at the local controller, the at least one average temperature;

comparing, at the local controller, the at least one average temperature to the temperature of the unit; and

based on the comparison, adjusting, by the local controller, the output of the unit.

12. The method of claim 11, the method further comprising:

adjusting, by the local controller, the output of the unit by at least linearly increasing the output based on a positive difference between the at least one average temperature and the temperature of the unit.

13. The method of claim 11, the method further comprising: adjusting, by the local controller, the output of the unit by at least linearly decreasing the output based on a negative difference between the at least one average temperature and the temperature of the unit.

14. The method of claim 11, the method further comprising decreasing, by the local controller, the output based on a threshold temperature of the unit.

15. The method of claim 11, wherein the output power comprises three phases;

the output of each of the plurality of units contributes to one of the three phases; and the calculating at least one average temperature based on the temperatures of each of the plurality of units comprises calculating an average temperature of the plurality of units contributing to each of the three phases.

16. The method of claim 11, wherein the receiving, from the temperature sensors, information relating to temperatures of each of the plurality of units comprises receiving information from a first temperature sensor measuring a temperature of an inverter and from a second temperature sensor measuring a temperature of a charger.

17. The method of claim 16, wherein the calculating at least one average temperature based on the temperatures of each of the plurality of units comprises calculating a first average temperature corresponding to an average of the temperatures of the inverters of the plurality of units and a second average temperature corresponding to an average of the temperatures of the chargers of the plurality of units.

18. The method of claim 17, the method further comprising:

providing, by each of the plurality of units, a second output to the charger; and adjusting, by the local controller, the second output based on a comparison of the second average temperature and the local temperature of the charger.

19. An uninterruptible power supply (UPS) system comprising:

an input configured to receive input power from an input power source;

an output configured to provide output power to a load;

a plurality of units coupled to the input and the output, each of the plurality of units configured to provide an output contributing to the output power; and

means for measuring, for each of the plurality of units, information relating to temperatures of each of the plurality of units;

20. The uninterruptible power supply of claim 19, further comprising means for:

receiving at least one average temperature of the UPS system;

comparing the at least one average temperature to a temperature of the unit; and based on the comparison, adjusting an output of the unit.