WO2014205794A1

WO2014205794A1 - Battery charger control

Info

Publication number: WO2014205794A1
Application number: PCT/CN2013/078405
Authority: WO
Inventors: Yunfeng Chen; Xie LI; Wei-Shih Chiang
Original assignee: Schneider Electric It Corporation
Priority date: 2013-06-28
Filing date: 2013-06-28
Publication date: 2014-12-31

Abstract

An uninterruptible power supply is provided which comprises a first input (102) configured to be coupled to an AC source and to receive input power, a second input configured to be coupled to a battery (118) and to receive backup power, an output (106) configured to be coupled to a load and to provide output AC power to the load derived from at least one of the input power and the backup power, a battery charger (116) coupled between the first input (102) and the battery (118) and configured to receive the input power and charge the battery (118) using a charging current, and a controller (120) coupled to the first input (102) and the battery charger (116), the controller (120) configured to monitor the input power at the first input (102), determine a quality level of the input power, and adjust the charging current of the battery charger (116) based on the quality level of the input power.

Description

BATTERY CHARGER CONTROL

BACKGROUND OF INVENTION

1. Field of Invention

At least some embodiments described herein relate generally to the charging of a battery within an Uninterruptible Power Supply (UPS).

2. Discussion of Related Art

Uninterruptible power supplies ("UPS") are used in a variety of applications to provide power to electrical loads, for example, loads that are intended to operate during interruptions in a primary source of electrical power. In general, a UPS includes, or is connected to, both a primary source of power and an alternate source of power where the alternate source of power can be employed to supply power to the electrical load when the primary source is not available (i.e., in a backup mode of operation). Often, the primary source of power is an AC power source such as power supplied from an electric utility. The alternate source of power generally includes one or more batteries supplying DC power which is converted by the UPS into AC power and provided to the electrical load during the backup mode of operation. The batteries are generally recharged by a battery charger coupled to the UPS that receives power provided to the UPS by the primary source of power.

SUMMARY OF INVENTION

At least one aspect of the invention is directed to an Uninterruptible Power Supply (UPS) comprising a first input configured to be coupled to an AC source and to receive input power, a second input configured to be coupled to a battery and to receive backup power, an output configured to be coupled to a load and to provide output AC power to the load derived from at least one of the input power and the backup power, a battery charger coupled between the first input and the battery and configured to receive the input power and charge the battery using a charging current, and a controller coupled to the first input and the battery charger, the controller configured to monitor the input power at the first input, determine a quality level of the input power, and adjust the charging current of the battery charger based on the quality level of the input power.

According to one embodiment, the controller is further configured to sample the input power over a defined period and determine the quality level of the input power based on input power samples. In one embodiment, the controller is further configured to identify, within the input power samples, occurrences of unacceptable input power and determine the quality level of the input power based on the occurrences of unacceptable input power. In another embodiment, the controller is further configured to determine the quality level of the input power based on an amount of time between occurrences of unacceptable input power.

According to another embodiment, the UPS further comprises a memory coupled to the controller, wherein the controller is further configured to determine, in reference to a first predefined mapping stored in the memory, an input power based charging current adjustment associated with the quality level of the input power and to adjust the charging current of the battery charger based on the input power based charging current adjustment. In one embodiment, the UPS further comprises an inverter including an input configured to receive at least one of the input power and the backup power and an output coupled to the output of the UPS.

According to one embodiment, the controller is further configured to determine a charge level of the battery and adjust, based on the charge level of the battery, the charging current of the battery charger. In one embodiment, the controller is further configured to determine, in reference to a second predefined mapping stored in the memory, a battery capacity based charging current adjustment associated with the charge level of the battery and to adjust the charging current of the battery charger based on the battery capacity based charging current adjustment. In another embodiment, the controller is further configured to determine a total charging current index by combining the input power based charging current adjustment with the battery capacity based charging current adjustment and to adjust the charging current of the battery charger based on the total charging current index.

Another aspect of the invention is directed to a method for operating a UPS, the UPS having an input, an output, a battery, and a battery charger, the method comprising

monitoring input AC power provided to the input of the UPS from an AC power source, operating the battery charger to charge the battery at a charging rate with the input AC power, determining a quality level of the input AC power, and adjusting the charging rate of the battery charger based on the quality level of the input AC power.

According to one embodiment, determining a quality level of the input AC power includes sampling the input AC power over a period of time. In one embodiment, determining a quality level of the input AC power further includes identifying within the input AC power samples any occurrences of unacceptable input power and determining the quality level of the input AC power based on any identified occurrences of unacceptable input power. In another embodiment, determining the quality level of the input AC power based on any identified occurrences of unacceptable input power includes determining the quality level of the input AC power based on an amount of time between occurrences of unacceptable input power.

According to another embodiment, the method further comprises referencing a first predefined mapping to associate the determined quality level of the input AC power with an input power based charging current adjustment, and adjusting the charging current of the battery charger based on the input power based charging current adjustment. In one embodiment, the method further comprises determining a charge level of the battery, and adjusting, based on the charge level of the battery, the charging current of the battery charger. In another embodiment, adjusting the charging current of the battery charger based on the charge level of the battery includes referencing a second predefined mapping to associate the charge level of the battery with a battery capacity based charging current adjustment, and adjusting the charging current of the battery charger based on the battery capacity based charging current adjustment.

According to one embodiment, the method further comprises determining a total charging current index by combining the input power based charging current adjustment with the battery capacity based charging current adjustment, and adjusting the charging current of the battery charger based on the total charging current index. In one embodiment, the method further comprises dynamically updating at least one of the input power based charging current adjustment and the battery capacity based charging current adjustment. In another embodiment, adjusting the charging rate of the battery charger includes increasing the charging rate of the battery charger to rate greater than 0.1C.

One aspect of the invention is directed to a computer readable medium comprising computer-executable instructions that when executed on a processor performs a method for operating a UPS having an input, an output, a battery, and a battery charger, the method comprising acts of monitoring input AC power provided to the input of the UPS from an AC power source, operating the battery charger to charge the battery at a charging rate with the input AC power, determining a quality level of the input AC power, and adjusting the charging rate of the battery charger based on the quality level of the input AC power. BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, 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 drawing. In the drawings:

FIG. 1 illustrates a UPS according to aspects of the current invention;

FIG. 2 illustrates a process for operating a battery charger according to aspects of the current invention;

FIG. 3 is a block diagram of a general-purpose computer system upon which various embodiments of the invention may be implemented; and

FIG. 4 is a block diagram of a computer data storage system with which various embodiments of the invention may be practiced.

DETAILED DESCRIPTION

Various embodiments and aspects thereof will now be discussed in detail with reference to the accompanying drawings. It is to be appreciated that this invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing", "involving", and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

As discussed above, the alternate source of power within a typical UPS is a battery that is charged by a battery charger within the UPS. Common battery chargers are configured to charge a battery at a fixed charging current. For example, standard battery chargers are typically configured to charge a battery at a fixed rate of 0.1C. C is a measure of the rate at which a battery is discharged relative to its maximum capacity. For instance, a battery having a 1C rate will completely discharge in 1 hour. With a battery having a capacity of lOOAh, a 1C rate of discharge equates to a discharge current of 100A, a 5C rate of discharge equates to a discharge current of 500A, and a 0.1C rate of discharge equates to a discharge current of 10A. Accordingly, if a battery having a capacity of 100 Ah is being charged by a battery charger at a rate of 0.1C, the charging current is fixed to a 1 OA level. Such a fixed charging current may prove inadequate where the utility power supplied to the UPS (and also the battery charger) is of poor quality. For example, each time utility power provided to the UPS and the battery charger fails, the battery is required to support the load coupled to the UPS in the backup mode (i.e., the battery discharges). When the utility power provided to the UPS and the battery charger returns to an acceptable level, the utility power is not only provided to the load but is also provided to the battery to charge the battery. However, as the fixed charging current of the battery charger is typically less than the discharging current of the battery, if the utility power provided to the UPS and the battery charger fails frequently (i.e., the utility power is of poor quality), the battery charger may not have adequate time to charge the battery to a sufficient level between outages and the repeatedly failing utility power may result in the battery charge falling below a level necessary to power the load in the backup mode.

In at least some embodiments described herein, a battery charger control scheme is provided that adjusts the charging current of a battery charger based on the quality of the utility power provided to the battery charger. For example, if utility power of poor quality is determined (i.e., the utility power is frequently failing), the charging current of the battery charger may be increased (e.g., increased to a level greater than 0.1C) to charge the battery more quickly when acceptable utility power is available. According to one embodiment, the charging current of a battery charger may also be adjusted based on the remaining charge on the battery. By dynamically adjusting the charging current based on current conditions rather than leaving the charging current at a fixed level, the battery charger control scheme described herein can account for poor quality utility power and adjust the charging current of a battery charger to avoid a failed battery condition.

FIG. 1 illustrates an online UPS 100 according to aspects of the current invention. The UPS 100 includes in input 102, an output 106, a bypass line 104, an AC/DC converter 110, a DC bus 114, a DC/ AC inverter 112, a battery charger 116, a battery 118, a DC/DC converter 122, and a controller 120. The input 102 is configured to be coupled to an AC power source such as a utility power source and to the AC/DC converter 110. The input 102 is also selectively coupled to the output 106 via the bypass line 104 and the switch 108.

The AC/DC converter 110 is also coupled to the DC/ AC inverter 112 via the DC bus

114. The DC/ AC inverter 112 is also selectively coupled to the output 106 via the switch 108. The battery 118 is coupled to the DC bus 114 via the battery charger 116 and also to the DC bus 114 via the DC/DC converter 122. The controller 120 is coupled to the input 102, the switch 108, the battery charger 116, the AC/DC converter 110, and the DC/ AC inverter 112. In other embodiments, the battery 118 and the charger 116 may be coupled to the AC/DC converter 110.

Based on the quality of the AC power received from the utility source, the UPS 100 is configured to operate in different modes of operation. For example, according to one embodiment, the controller 120 monitors the AC power received from the utility source at the input 102 and, based on the monitored AC power, sends control signals to the switch 108, the battery charger 116, the AC/DC converter 110, and the DC/ AC inverter 112 to control operation of the UPS 100.

In response to a determination that the AC power received from the utility source is acceptable (e.g., at a desired level), the controller 120 operates the UPS 100 to enter a "bypass" mode of operation. In the "bypass" mode of operation, the controller 120 transmits control signals to operate the switch 108 to selectively couple the output 106 to the bypass line 104. Accordingly, in the "bypass" mode of operation, the input 102 of the UPS 100 (coupled to the utility source) is coupled directly to the output 106 of the UPS 100 via the bypass line 104 and unconditioned AC power received at the input 102 from the utility source is provided directly to the output 106 to power a load.

In response to a determination that the AC power received from the utility source is in a sag or swell condition, the controller 120 operates the UPS 100 to enter an "online" mode of operation. In the "online" mode of operation, the controller 120 transmits control signals to operate the switch 108 to selectively couple the output 106 to the DC/ AC inverter 112 and the AC/DC converter 110 receives AC power from the utility source coupled to the input 102. The controller 120 operates the AC/DC converter 110 to convert the AC power into DC power and provide the DC power to the DC bus 114. The inverter DC/ AC inverter 112 is operated by the controller 120 to convert the DC power on the DC bus 114 into conditioned AC power and the conditioned AC power is provided to the output 106. Also in the "online" mode of operation, the controller 120 operates the battery charger 116 to charge the battery 118 with DC power from the DC bus 114 at a desired rate.

In response to a determination that the AC power received from the utility source is in a brownout or blackout condition, the controller 120 operates the UPS 100 to enter a

"battery" mode of operation. In the "battery" mode of operation, the controller 120 transmits control signals to operate the switch 108 to couple the output 106 to the DC/ AC inverter 112, and DC power from the battery 118 is provided to the DC/DC converter 122 as the battery 118 discharges. The DC/DC converter 122 converts the received DC power from the battery 118 into DC power at a desired level and provides the converted DC power to the DC bus 114. The DC/ AC inverter 112 is operated by the controller 120 to convert the DC power received from the battery 118, via the DC/DC converter 122 and the DC bus 114, into conditioned AC power and the conditioned AC power is provided to the output 106.

As discussed above, in the "online" mode of operation, the controller 120 is configured to operate the charger 116 to charge the battery 118 with power from the DC bus 114 at a desired rate. According to one embodiment, the initial rate (i.e., upon initially entering the "online" mode of operation) at which the controller 120 operates the charger 116 to charge the battery 118 is 0.1C; however, in other embodiments, the initial rate at which the controller 120 operates the charger 116 to charge the battery 118 may be defined differently.

Also, according to at least one embodiment described herein, the controller 120 is configured to adjust the rate at which the battery 1 18 is being charged in response to a determination regarding the quality of the AC power being provided to the input 102 by the utility source. For example, according to at least one embodiment, the controller 120 monitors the AC power provided to the input 102 by the utility source over a predefined period. For example, in one embodiment, the controller 120 takes a predefined number of input power samples and determines the quality of the utility power based on the predefined number of samples. In one embodiment, the controller 120 makes the utility power quality determination based on ten previous input power samples; however, in other embodiments, the controller 120 may be configured to make the utility power quality determination based on any number of input power samples.

According to one embodiment, the controller 120 analyzes the input power samples to identify any continuous blackout or brownout conditions in the utility power. According to one embodiment, a continuous blackout or brownout is defined as a blackout or brownout that lasts at least one hour; however, in other embodiments, a continuous blackout or brownout may be defined differently. Upon identifying any continuous blackout or brownout conditions in the sampled input utility power, the controller 120 determines the amount of time between the identified continuous blackout or brownout conditions (i.e., the amount of time at which the utility power was continuously provided to the input 102 at an acceptable level). Based on the amount of time sensed between continuous blackout or brownout conditions, the controller 120 determines the quality of the utility power. According to one embodiment, based on the amount of time sensed between continuous blackout or brownout conditions, the controller 120 assigns a quality level to the utility power. For example, according to one embodiment, a quality level (level 1 being the highest quality and level 5 being the lowest quality) is assigned to the utility power based on Table 1 shown below.

Table 1

As shown in Table 1, the controller 120 assigns a quality level to utility power based on the sensed duration between continuous blackout or brownout conditions. For example, in response to identifying a relatively long time (e.g., greater than thirteen hours) between continuous blackout or brownout conditions, the controller 120 determines that the utility power at the input 102 is of relatively high quality and assigns a quality level of one to the utility power. Alternatively, in response to identifying a relatively short time (e.g., less than six hours) between continuous blackout or brownout conditions, the controller 120 determines that the utility power at the input 102 is of relatively poor quality and assigns a quality level of five to the utility power. According to other embodiments, the defined durations between continuous blackout or brownout conditions and the corresponding utility quality levels may be defined differently.

Based on the quality level assigned by the controller 120 to the utility power provided to the input 102, the controller 120 determines a utility quality based charging current adjustment. For example, according to one embodiment, the controller 120 determines a utility quality based charging current adjustment based on Table 2 shown below. Utility quality level Utility Quality based charging

current adjustment

5 0.15C

4 0.14C

3 0.12C

2 0.11C

1 0.1C

Table 2

As shown in Table 2, the controller 120 determines a utility quality based charging current adjustment based on the quality level assigned to the utility power. For example, if the utility power is assigned a quality level of one (i.e., the utility power is of the highest quality), the controller 120 determines that the utility quality based charging current adjustment is 0.1C and the charging current will remain at the initial 0.1C (due to the high quality of the utility power). Alternatively, if the utility power is assigned a quality level of five (i.e., the utility power is of the lowest quality), the controller 120 determines that the utility quality based charging current adjustment is 0.15C and the charging current is increased to 0.15C (due to the low quality of the utility power). By increasing the charging current due to a determination of low quality utility power, the battery 118 may be charged more quickly to take advantage of the limited time at which the utility power is at an acceptable level. According to other embodiments, the defined relationships between utility quality levels and the utility quality based charging current adjustments may be defined differently.

According to one embodiment, in addition to utility quality, the controller 120 is also configured to adjust the rate at which the battery 1 18 is being charged in response to a determination regarding the current charge level of the battery 118. For example, according to one embodiment, the controller determines the current charge state of the battery 118 (i.e., the percentage of utilized battery capacity) and determines a battery capacity based charging current adjustment in response to the charge stage. According to one embodiment, the controller 120 determines the battery capacity based charging current adjustment based on Table 3 shown below. Battery Capacity Battery Capacity based

charging current adjustment

>95% OC

80%-95% 0.02C

60%-79% 0.04C

40%-59% 0.06C

20%-39% 0.08C

0%-19% 0.1C

Table 3

As shown in Table 3, the controller 120 determines a battery capacity based charging current adjustment based on the current charge level of the battery 118. For example, if the battery 118 is charged to more than ninety- five percent of its total capacity, the controller 120 determines that the battery capacity based charging current adjustment is 0C and the charging current will not be further adjusted based on the current charge level of the battery 118.

Alternatively, if the battery 118 is charged to less than nineteen percent of its total capacity, the controller 120 determines that the utility quality based charging current adjustment is 0.1C and the charging current is further increased by 0.1C (due to the low charge level of the battery 118). By increasing the charging current due to a determination of a low charge level of the battery, the battery 118 may be charged more quickly to avoid total discharging of the battery during a subsequent power outage. According to other embodiments, the defined relationships between the charge levels of the battery 118 and the battery capacity based charging current adjustments may be defined differently.

According to one embodiment, the controller 120 is configured to adjust the rate at which the battery 118 is being charged based on the determination of utility quality, as discussed above. In another embodiment, the controller 120 is configured to adjust the rate at which the battery 118 is being charged based on the current charge level of the battery 118, as discussed above. In another embodiment, the controller 120 is configured to adjust the rate at which the battery 118 is being charged based on the determination of utility quality and current charge level of the battery 118. For example, according to one embodiment, the controller 120 combines the utility quality based charging current adjustment and the battery capacity based charging current adjustment to determine a total battery charging current index that is utilized to adjust the charging current of the battery 118 based on the utility quality and the charge state of the battery 118 to avoid a failed battery condition.

For example, according to one embodiment, where the controller 120 determines that the utility quality based charging current adjustment is .12C (based on the utility power being assigned a quality level of three) and the battery capacity based charging current adjustment is .06C (based on the battery 118 being charged to between forty percent and fifty-nine percent of its total capacity), the total battery charging current index is .18C (.12C + .06C) and the charging current of the battery charger 116 is adjusted to .18C to best utilize the available utility power to charge the almost half-empty battery 118.

Control of the battery charger 116 is discussed in greater detail with regard to FIG. 2. FIG. 2 is a flow chart 200 illustrating a process for controlling the battery charger 116 to charge the battery 118. At block 202, the UPS 100 is powered on. At block 204, the controller 120 retrieves, from memory, the current utility quality based charging current adjustment (e.g., bChargeCurrentO). According to one embodiment, if the UPS 100 is being powered on for the first time, the variable bChargeCurrentO is predefined in memory as a desired initial charging current (e.g., .1C). According to another embodiment, the variable bChargeCurrentO is defined previously during prior operation of the UPS 100 and saved in memory. According to one embodiment, the memory is an Electrically Erasable

Programmable Read-Only Memory (EEPROM); however, in other embodiments, the memory may be any other appropriate type of memory device. Upon retrieving the current utility quality based charging current adjustment (e.g., bChargeCurrentO) from memory, the controller 120 enters background loop 206.

In the background loop 206, multiple tasks are performed. In a first task at block 208, a determination is made whether the UPS is in the "online" mode of operation, as discussed above. In response to a determination that the UPS is not in the "online" mode of operation (e.g., the UPS 100 is in the "battery" or "bypass" mode of operation), at block 226 the controller 120 initiates a Return To System (RTS) command and the first task of the background loop 206 is restarted.

In response to a determination that the UPS is in the "online" mode of operation, at block 210 the controller 120 samples the utility power and determines the amount of time between continuous blackout or brownout conditions, as described above. As also discussed above, based on the amount of time between continuous blackout or brownout conditions, the controller 120 assigns a quality level to the utility power. In reference to a predefined mapping between utility quality levels and utility quality based charging current adjustments stored in memory (e.g., such as Table 2), the controller 120 determines an updated utility quality based charging current adjustment based on the current utility quality level. At block 214, a determination is made whether the updated utility quality based charging current adjustment is the same as the current utility quality based charging current adjustment (e.g., bChargeCurrentO). In response to a determination that the updated utility quality based charging current adjustment is the same as the current utility quality based charging current adjustment, at block 226 the controller 120 initiates a Return To System (RTS) command and the first task of the background loop 206 is restarted. In response to a determination that the updated utility quality based charging current adjustment is not the same as the current utility quality based charging current adjustment, at block 216 the updated utility quality based charging current adjustment is stored in memory as the new current utility quality based charging current adjustment (e.g., bChargeCurrentO). Upon updating the variable bChargeCurrentO, at block 226 the controller 120 initiates a Return To System (RTS) command and the first task of the background loop 206 is restarted.

In a second task of the background loop 206 at block 218, the controller 120 determines the current charge level of the battery 1 18 (i.e., the percentage of total battery capacity currently charged). According to one embodiment, the controller 120 monitors the charge on the battery 118 and calculates the charge level of the battery 118 itself. In another embodiment, the controller 120 receives a signal, from the battery 118 or battery charger 116, indicating the charge level of the battery 118. At block 220, the controller 120 updates the variable bChargeCurrentl with the determined current charge level of the battery 118. Upon updating the variable bChargeCurrentl , at block 226 the controller 120 initiates a Return To System (RTS) command and the second task of the background loop 206 is restarted.

In a third task of the background loop 206 at block 222, a determination is made whether the UPS is in the "online" mode of operation. In response to a determination that the UPS is not in the "online" mode of operation (e.g., the UPS 100 is in the "battery" or

"bypass" mode of operation), at block 226 the controller 120 initiates a Return To System (RTS) command and the third task of the background loop 206 is restarted.

In response to a determination that the UPS is in the "online" mode of operation, at block 224 the controller 120 calculates the total battery charging current index (variable bChargeCurrent) by summing the current utility quality based charging current adjustment (bChargeCurrentO) and the current battery capacity based charging current adjustment

(bChargeCurrentl), as discussed above. The controller 120 adjusts the charging current of the battery charger 116 based on the updated total battery charging current index

(bChargeCurrent). Upon adjusting the charging current of the battery charger 116, at block 226 the controller 120 initiates a Return To System (RTS) command and the third task of the background loop 206 is restarted.

According to one embodiment, the background loop 206 may be interrupted by an Interrupt Service Routine (ISR) 228. The ISR 228 has a higher priority than the background loop 206 and allows the UPS 100 (or the user of the UPS 100) to interrupt the background loop 206 to manually set the charging current of the battery charger 116 to a desired level.

Various embodiments according to the present invention may be implemented on one or more computer systems or other devices. A computer system may be a single computer that may include a minicomputer, a mainframe, a server, a personal computer, or combination thereof. The computer system may include any type of system capable of performing remote computing operations (e.g., cell phone, PDA, tablet, smart-phone, set-top box, or other system). A computer system used to run the operation may also include any combination of computer system types that cooperate to accomplish system-level tasks. Multiple computer systems may also be used to run the operation. The computer system also may include input or output devices, displays, or data storage units. It should be appreciated that any computer system or systems may be used, and the invention is not limited to any number, type, or configuration of computer systems.

These computer systems may be, for example, general-purpose computers such as those based on Intel PENTIUM-type processor, Motorola PowerPC, Sun UltraSPARC, Hewlett-Packard PA-RISC processors, or any other type of processor. It should be appreciated that one or more of any type computer system may be used to partially or fully automate operation of the described system according to various embodiments of the invention. Further, the system may be located on a single computer or may be distributed among a plurality of computers attached by a communications network.

For example, various aspects of the invention may be implemented as specialized software executing in a general-purpose computer system 300 such as that shown in FIG. 3. The computer system 300 may include a processor 302 connected to one or more memory devices (i.e., data storage) 304, such as a disk drive, memory, or other device for storing data. Memory 304 is typically used for storing programs and data during operation of the computer system 300. Components of computer system 300 may be coupled by an interconnection mechanism 306, which may include one or more busses (e.g., between components that are integrated within a same machine) and/or a network (e.g., between components that reside on separate discrete machines). The interconnection mechanism 306 enables communications (e.g., data, instructions) to be exchanged between system components of system 300.

Computer system 300 also includes one or more input devices 308, for example, a keyboard, mouse, trackball, microphone, touch screen, and one or more output devices 310, for example, a printing device, display screen, and/or speaker. In addition, computer system 300 may contain one or more interfaces (not shown) that connect computer system 300 to a

communication network (in addition or as an alternative to the interconnection mechanism 306).

The storage system 312, shown in greater detail in FIG. 4, typically includes a computer readable and writeable nonvolatile recording medium 402 in which signals are stored that define a program to be executed by the processor or information stored on or in the medium 402 to be processed by the program. The medium may, for example, be a disk or flash memory. Typically, in operation, the processor causes data to be read from the nonvolatile recording medium 402 into another memory 404 that allows for faster access to the information by the processor than does the medium 402. This memory 404 is typically a volatile, random access memory such as a dynamic random access memory (DRAM) or static memory (SRAM). It may be located in storage system 312, as shown, or in memory system 304. The processor 302 generally manipulates the data within the integrated circuit memory 304, 404 and then copies the data to the medium 402 after processing is completed. A variety of mechanisms are known for managing data movement between the medium 402 and the integrated circuit memory element 304, 404, and the invention is not limited thereto. The invention is not limited to a particular memory system 304 or storage system 312.

The computer system may include specially-programmed, special-purpose hardware, for example, an application-specific integrated circuit (ASIC). Aspects of the invention may be implemented in software, hardware or firmware, or any combination thereof. Further, such methods, acts, systems, system elements and components thereof may be implemented as part of the computer system described above or as an independent component.

Although computer system 300 is shown by way of example as one type of computer system upon which various aspects of the invention may be practiced, it should be

appreciated that aspects of the invention are not limited to being implemented on the computer system as shown in FIG. 3. Various aspects of the invention may be practiced on one or more computers having a different architecture or components that that shown in FIG. 3.

Computer system 300 may be a general-purpose computer system that is programmable using a high-level computer programming language. Computer system 300 may be also implemented using specially programmed, special purpose hardware. In computer system 300, processor 302 is typically a commercially available processor such as the well-known Pentium class processor available from the Intel Corporation. Many other processors are available. Such a processor usually executes an operating system which may be, for example, the Windows 95, Windows 98, Windows NT, Windows 2000 (Windows ME), Windows XP, or Windows Visa operating systems available from the Microsoft Corporation, MAC OS System X available from Apple Computer, the Solaris Operating System available from Sun Microsystems, or UNIX available from various sources. Many other operating systems may be used.

The processor and operating system together define a computer platform for which application programs in high-level programming languages are written. It should be understood that the invention is not limited to a particular computer system platform, processor, operating system, or network. Also, it should be apparent to those skilled in the art that the present invention is not limited to a specific programming language or computer system. Further, it should be appreciated that other appropriate programming languages and other appropriate computer systems could also be used.

One or more portions of the computer system may be distributed across one or more computer systems (not shown) coupled to a communications network. These computer systems also may be general-purpose computer systems. For example, various aspects of the invention may be distributed among one or more computer systems configured to provide a service (e.g., servers) to one or more client computers, or to perform an overall task as part of a distributed system. For example, various aspects of the invention may be performed on a client-server system that includes components distributed among one or more server systems that perform various functions according to various embodiments of the invention. These components may be executable, intermediate (e.g., IL) or interpreted (e.g., Java) code which communicate over a communication network (e.g., the Internet) using a communication protocol (e.g., TCP/IP).

It should be appreciated that the invention is not limited to executing on any particular system or group of systems. Also, it should be appreciated that the invention is not limited to any particular distributed architecture, network, or communication protocol. Various embodiments of the present invention may be programmed using an object-oriented programming language, such as SmallTalk, Java, C++, Ada, or C# (C-Sharp). Other object- oriented programming languages may also be used. Alternatively, functional, scripting, and/or logical programming languages may be used. Various aspects of the invention may be implemented in a non-programmed environment (e.g., documents created in HTML, XML or other format that, when viewed in a window of a browser program, render aspects of a graphical -user interface (GUI) or perform other functions). Various aspects of the invention may be implemented as programmed or non-programmed elements, or any combination thereof.

As described herein, control of a battery charger within an online UPS is provided; however, in other embodiments, control of a battery charger within any other type of UPS (e.g., an offline or line-interactive UPS) may be similarly performed.

As described herein, the battery charging current of the battery charger 116 is adjusted in an "online" mode of operation; however, in other embodiments, the battery charging current of the battery charger 116 may be adjusted during any other appropriate mode of operation in which the battery 118 is being charged.

As described herein, control of a battery charger within a UPS coupled to a utility power source is provided; however, in other embodiments, the UPS may be coupled to another type of AC power source.

As described herein, control of a battery charger within a UPS is provided; however, in other embodiments, control of a battery charger within any other type of system including a battery charger and battery may similarly be performed.

Accordingly, at least some embodiments described herein provide a battery charger control scheme that adjusts the charging current of a battery charger based on the quality of the utility power provided to the battery charger. According to at least one embodiment, the charging current of a battery charger may also be adjusted based on the remaining charge on the battery. By dynamically adjusting the charging current based on current conditions of the utility power and the battery capacity, rather than leaving the charging current at a fixed level, the battery charger control scheme described herein can account for poor quality utility power and adjust the charging current of a battery charger to avoid a failed battery condition.

Having thus described several aspects of at least one embodiment of this invention, 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 spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. What is claimed is:

Claims

1. An Uninterruptible Power Supply (UPS) comprising:

a first input configured to be coupled to an AC source and to receive input power;

a second input configured to be coupled to a battery and to receive backup power;

an output configured to be coupled to a load and to provide output AC power to the load derived from at least one of the input power and the backup power;

a battery charger coupled between the first input and the battery and configured to receive the input power and charge the battery using a charging current; and a controller coupled to the first input and the battery charger, the controller configured to monitor the input power at the first input, determine a quality level of the input power, and adjust the charging current of the battery charger based on the quality level of the input power.

2. The UPS of claim 1, wherein the controller is further configured to sample the input power over a defined period and determine the quality level of the input power based on input power samples.

3. The UPS of claim 2, wherein the controller is further configured to identify, within the input power samples, occurrences of unacceptable input power and determine the quality level of the input power based on the occurrences of unacceptable input power.

4. The UPS of claim 3, wherein the controller is further configured to determine the quality level of the input power based on an amount of time between occurrences of unacceptable input power.

5. The UPS of claim 1, further comprising a memory coupled to the controller, wherein the controller is further configured to determine, in reference to a first predefined mapping stored in the memory, an input power based charging current adjustment associated with the quality level of the input power and to adjust the charging current of the battery charger based on the input power based charging current adjustment.

6. The UPS of claim 5, wherein the controller is further configured to determine a charge level of the battery and adjust, based on the charge level of the battery, the charging current of the battery charger.

7. The UPS of claim 6, wherein the controller is further configured to determine, in reference to a second predefined mapping stored in the memory, a battery capacity based charging current adjustment associated with the charge level of the battery and to adjust the charging current of the battery charger based on the battery capacity based charging current adjustment.

8. The UPS of claim 7, wherein the controller is further configured to determine a total charging current index by combining the input power based charging current adjustment with the battery capacity based charging current adjustment and to adjust the charging current of the battery charger based on the total charging current index.

9. The UPS of claim 1, further comprising an inverter including an input configured to receive at least one of the input power and the backup power and an output coupled to the output of the UPS.

10. A method for operating a UPS, the UPS having an input, an output, a battery, and a battery charger, the method comprising:

monitoring input AC power provided to the input of the UPS from an AC power source;

operating the battery charger to charge the battery at a charging rate with the input AC power;

determining a quality level of the input AC power; and

adjusting the charging rate of the battery charger based on the quality level of the input AC power.

11. The method of claim 10, wherein determining a quality level of the input AC power includes sampling the input AC power over a period of time.

12. The method of claim 11, wherein determining a quality level of the input AC power further includes identifying within the input AC power samples any occurrences of unacceptable input power and determining the quality level of the input AC power based on any identified occurrences of unacceptable input power.

13. The method of claim 12, wherein determining the quality level of the input AC power based on any identified occurrences of unacceptable input power includes determining the quality level of the input AC power based on an amount of time between occurrences of unacceptable input power.

14. The method of claim 10, further comprising:

referencing a first predefined mapping to associate the determined quality level of the input AC power with an input power based charging current adjustment; and

adjusting the charging current of the battery charger based on the input power based charging current adjustment.

15. The method of claim 14, further comprising:

determining a charge level of the battery; and

adjusting, based on the charge level of the battery, the charging current of the battery charger.

16. The method of claim 15, wherein adjusting the charging current of the battery charger based on the charge level of the battery includes:

referencing a second predefined mapping to associate the charge level of the battery with a battery capacity based charging current adjustment; and

adjusting the charging current of the battery charger based on the battery capacity based charging current adjustment.

17. The method of claim 16, further comprising:

determining a total charging current index by combining the input power based charging current adjustment with the battery capacity based charging current adjustment; and adjusting the charging current of the battery charger based on the total charging current index.

18. The method of claim 16, further comprising dynamically updating at least one of the input power based charging current adjustment and the battery capacity based charging current adjustment.

19. The method of claim 10, wherein adjusting the charging rate of the battery charger includes increasing the charging rate of the battery charger to rate greater than 0.1C.

20. A computer readable medium comprising computer-executable instructions that when executed on a processor performs a method for operating a UPS having an input, an output, a battery, and a battery charger, the method comprising acts of:

determining a quality level of the input AC power; and