HYBRID ARCHITECTURE FOR DC POWER PLANTS AND A METHOD OF MINIMIZING BATTERY CONDUCTOR CURRENT

Abstract

Included herein is a DC power plant, a DC power system and a method of reducing battery current. In one embodiment, the DC power plant includes: (1) a rectifier system including an AC power input and a DC power output, the rectifier system configured to receive an AC input voltage at the AC power input and produce a DC output voltage at the DC power output and (2) a controller configured to monitor a battery current associated with a battery distribution conductor coupled to the rectifier system for a remote battery system and dynamically adjust the DC output voltage to maintain the battery current at substantially zero amperes.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is related to and claims priority based on U.S. Provisional Patent Application Ser. No. 61/287,322, filed by Davis, et al., on Dec. 17, 2009, entitled “Hybrid Power Architecture for DC Power Plants,” commonly owned herewith and incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The invention is related, in general, to electrical power sources, and, more specifically to DC power plants for providing power to telecommunication systems.

BACKGROUND OF THE INVENTION

Telecommunication and data switching systems are used to route tens of thousands of calls and data connections per second. The failure of such a system, due to either an equipment breakdown or a loss of power, is generally unacceptable since it would result in a loss of millions of voice and data communications along with its corresponding revenue. The traditionally high reliability of telecommunication systems, that users have come to expect, is partially based on the use of redundant equipment including power supplies.

DC Power plants are used in the telecommunications industry to provide large amounts of DC power to critical loads and insure un-interrupted operation through the use of batteries or other energy storage media. DC Power plants typically include rectifiers that receive and rectify AC power to produce DC power for powering external equipment (i.e., loads) during normal operation. When an AC source is unable to provide power for the rectifiers to produce DC power for the loads, DC power plants can utilize the batteries as back-up to provide DC power for the equipment.

SUMMARY OF THE INVENTION

This disclosure provides a power plant. In one embodiment, the power plant includes: (1) a rectifier system including an AC power input and a DC power output, the rectifier system configured to receive an AC input voltage at the AC power input and produce a DC output voltage at the DC power output and (2) a controller configured to monitor a battery current associated with a battery distribution conductor coupled to the rectifier system for a remote battery system and dynamically adjust the DC output voltage to maintain the battery current at substantially zero amperes.

In another aspect, a DC power system is disclosed. In one embodiment, the DC power system includes: (1) a DC power bus, (2) a battery system coupled to the DC power bus, (3) a battery charger coupled to the DC power bus, (4) primary DC distribution interrupting devices coupled to the DC power bus, and (5) a power plant coupled to the DC power bus through the primary DC distribution interrupting devices, the power plant located remotely from the DC power bus, the battery system and the battery charger.

In still another aspect, a method of reducing a battery current associated with a rectifier system of a DC power plant is disclosed. In one embodiment, the method includes: (1) receiving a sensed current from a location on a battery distribution conductor connecting the DC power plant to a remote battery system and (2) dynamically adjusting a DC output voltage of the DC power plant based on the sensed current to reduce the battery current to substantially zero amperes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosure, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a system diagram of an embodiment of a DC power system constructed according to the principles of the disclosure;

FIG. 2 illustrates a block diagram of an embodiment of a DC power plant constructed according to the principles of the disclosure;

FIG. 3 illustrates a schematic diagram of an embodiment of a DC power system constructed according to the principles of the disclosure;

FIG. 4 illustrates a schematic diagram of another embodiment of a DC power system constructed according to the principles of the disclosure; and

FIG. 5 illustrates a flow diagram of an embodiment of a method of reducing a battery current carried out according to the principles of the disclosure.

DETAILED DESCRIPTION

DC power systems may be structured in different configurations. In a centralized architecture, the power plants and batteries are positioned at a central location. Often, this may be the basement of a central office of a telecommunications company. DC power is then provided through battery distribution conductors to loads, such as telecommunications equipment, that are remotely located from the central location. As a result of high currents flowing in the long conductors, DC losses associated with the remote location of the power plants to the loads can occur. In a distributed architecture, batteries and power plants are split into smaller units and positioned proximate the loads. While this may reduce the DC losses, the distributed architecture also can also be costlier due to the cost of suitable batteries with chemistry compatible with load equipment co-location.

The present disclosure provides a DC power system that allows centrally located batteries and also reduces DC losses associated with battery distribution conductors between the centrally located batteries and remote loads. The disclosed DC power system advantageously employs cost efficient battery technology that can be centrally located with DC power plants that can be co-located with the load equipment to provide DC efficiency. Thus, the disclosed DC power systems place the disclosed DC power plants close to load equipment, eliminating the resistive losses associated with the long battery distribution conductors from the central power plant. As such, the central located batteries incur or essentially incur conductor loss only when in discharge mode.

The disclosed DC power plant includes a rectifier system (i.e., a rectifier or rectifiers) that receives an AC input voltage and produces a DC output voltage. Additionally, the DC power plant includes a controller that monitors and controls the operation of the rectifier system and reduces battery current during normal operation between the DC power plant and the distal batteries that are centrally located. The individual DC power plants that are powering the loads are equipped with a battery current elimination feature to reduce the current flowing from the DC power plants to the batteries to substantially zero (which includes zero) during normal operation. In one embodiment, this is achieved by monitoring the battery current using a traditional resistance current shunt, and dynamically adjusting the DC power plant voltage to force the current to zero amperes. This occurs when the voltages on either side of the shunt are the same. Instead of using the resistance from the shunt, the resistance of the battery distribution conductor may also be used. Reducing the current flowing in the battery distribution conductors insures that there are minimal losses in these conductors during normal operation and also enables the battery charging power plant to optimize the battery charging voltage.

The disclosure also provides a battery charger located proximate with the batteries that is dedicated to charge the centrally located batteries. The battery charger can be sized and optimized to provide battery charging current for the battery system. The remotely located DC power plants do not have to be used to charge the battery system. Accordingly, the distributed DC power plants do not have to cooperate to provide the optimum charging current for the battery system that is remotely located from the DC power plants. Additionally, DC losses are not incurred over the battery distribution conductors during the charging process. Instead, the battery charger that is proximate the batteries can be dedicated just for charging allowing the battery charger to be optimized for providing battery charging current for the battery system.

As discussed in more detail below, the disclosed DC power system architecture moves rectifiers closer to loads, preserves existing battery room investments, avoids the costs of re-cabling a DC infrastructure while maintaining a low risk battery location and minimizes DC operating losses. Additionally, DC output voltage of the disclosed DC power plants can be dynamically controlled to reduce current on battery distribution conductors to zero and minimize losses. Furthermore, a battery charger can be dedicated to charging the centrally located battery system allowing an optimized voltage being set for charging.

FIG. 1 illustrates a system diagram of an embodiment of a DC power system 100 constructed according to the principles of the disclosure. The DC power system 100 includes a DC power bus 110, a battery system 120, a battery charger 130, primary DC distribution interrupting devices 140, DC power plants 150 and 155, DC power distribution centers 160 and 165, battery distribution conductors 170 and DC distribution connections 180, 185.

The DC power bus 110 may be a conventional DC bus that is used in a DC power system having a centralized architecture. The battery system 120 and the primary DC distribution interrupting devices 140 may also be conventional devices that are used in conventional centralized architecture DC power systems. The battery system 120, for example, may be conventional lead acid batteries. In other embodiments, the battery system 120 may include another type of battery used for storing energy. The primary DC distribution interrupting devices 140 may be conventional DC switches. In other embodiments, the primary DC distribution interrupting devices 140 may be another type of device for interrupting DC load such as a circuit breaker or a fuse.

The DC power bus 110, the battery system 120 and the primary DC distribution interrupting devices 140 may all be located in a single location. For example, these devices may be centrally located in a basement or single room. In some embodiments, the DC power bus 110, the battery system 120 and the primary DC distribution interrupting devices 140 may be centrally located in a central office of a telecommunications company.

The battery charger 130 may also be located proximate the DC power bus 110, the battery system 120 and the primary DC distribution interrupting devices 140 at a single location. The battery charger 130 receives an AC power and generates DC power. As such, the battery charger 130 can provide a DC battery charging current. The AC power may be supplied from a commercial utility company or even an emergency AC source. The battery charger 130 is coupled to the DC power bus 110 and, therethrough provides a charging current for the battery system 120. The battery charger 130 may be a DC power plant that is specifically sized and designated to provide the battery charging current for the battery system 120. As such, the battery charger 130 includes sufficient capacity (e.g., rectifiers) to produce the needed battery charging current for the battery system 120. With the DC power system 100, the battery charger 130 is not needed to provide DC power for loads. As such, the battery charger 130 can be sized only for generating the needed battery charging current for the battery system 120. The battery charger 130, along with the battery system 120 and the primary DC distribution interrupting devices 140 may be coupled to the DC power bus 110 via conventional connectors, cables or bus bar.

The battery distribution conductors 170 may be battery distribution cables, bus bars or other current carrying components that may be typically used in a DC power system having a centralized architecture. The battery distribution conductors 170 electrically couple the DC power plants 150, 155, to the primary DC distribution interrupting devices 140. The battery distribution conductors 170 are sized to provide DC power to loads when the AC power supply is unavailable for the DC power plants 150, 155. The size of the battery distribution conductors 170, therefore, may vary depending on the needed capacity and the distance between the primary DC distribution interrupting devices 140 and the DC power plants 150, 155, which are located proximate to the loads.

The DC power plants 150, 155, receive an AC power supply and produce DC power. The DC power plants 150, 155, include a rectifier system that receives the AC power supply and generates the DC power. However, the DC power plants 150, 155, do not include a battery for storing the generated DC power. The rectifier system may be a conventional rectifier or rectifiers. The DC power plants 150, 155, also include controllers that monitor and direct the operation of the rectifier systems. The controllers and rectifier systems are not denoted in FIG. 1 but are illustrated in FIG. 2 and correspondingly discussed below. The DC power plants 150, 155, may be located in cabinets 151, 156.

During normal operation (i.e., when there is AC power and the rectifier system is producing DC power therefrom) the DC power plants 150, 155, provide DC for the loads. As such, the battery system 120 is not discharging or in a discharge mode. The DC power is provided to the loads from the DC power plants 150, 155, via the DC distribution connections 180, 185, and the power distribution centers 160, 165. The DC distribution connections 180, 185, may be conventional cables or bus for transmitting DC power. Additionally, the power distribution centers 160, 165, may be conventional devices used to provide secondary fusing, switching or circuit breaking for DC power delivered to equipment. The power distribution centers 160, 165, can provide battery redundancy to the loads through the use of multiple load buses. In one embodiment, either of the power distribution centers 160, 165, may be a Battery Distribution Fuse Bay (BDFB) available from Lineage Power Corporation of Plano, Tex. In other embodiments, either of the power distribution centers 160, 165, may be a Battery Distribution Circuit Breaker Bay (BDCBB) available from Lineage Power Corporation.

As illustrated, the battery distribution conductors 170 may also provide redundancy between the DC power bus 110 and the DC power plants 150, 155. During normal operation, the battery distribution conductors 170 do not need to provide DC power to the loads since this is handled by the DC power plants 150, 155. Accordingly, to prevent battery current on the battery distribution conductors 170 during normal operation, the controller is configured to monitor the battery current (i.e., distal battery current) on the battery distribution conductors 170. The battery current on the battery distribution conductors 170 includes current generated by the rectifier system of the DC power plants 150, 155, via a DC bus of the DC power plants 150, 155. The controllers of the DC power plants 150, 155, dynamically adjust the DC output voltage from the rectifier systems to maintain the distal battery current at substantially zero amperes. The accuracy of measuring circuits or control circuits employed with the DC power system 100 may determine how close to zero amperes the distal battery current can be maintained. Accordingly, the battery distribution conductors 170 may only incur resistive losses when in discharge mode (i.e., when the battery system 120 is providing DC power to the loads).

FIG. 2 illustrates a block diagram of an embodiment of a DC power plant 200 constructed according to the principles of the disclosure. The DC power plant 200 includes a rectifier system 210, a controller 220, a DC bus 230, a remote battery connection 240 and a proximate load connection 250.

The rectifier system 210 includes an AC power input 212 and a DC power output 216. Coupled to the rectifier system 210 is the controller 220. The controller 220 is configured to monitor and manage the operation of the rectifier system 210. The controller 220 includes a processor 222 and a current sensing interface 226. The controller 220 may include additional components and interfaces that are typically included in a power plant controller.

The rectifier system 210 is configured to receive an AC input voltage at the AC power input 212 and produce a DC output voltage at the DC power output 216. The rectifier system 210 may be a conventional AC to DC rectifier or rectifiers. In one embodiment, the DC output voltage 216 may be at +24 volts and −48 volts. Of course, in other embodiments, the DC output voltage may vary. Coupled to the DC power output is a DC bus 230. Connected to the DC bus 230 are a remote battery connection 240 and a proximate load connection 250. The DC bus 230 includes a positive bus bar and relative thereto, a negative bus bar. The DC bus 230 may be a typical DC bus included in a conventional power plant. The remote battery connection 240 is sufficiently sized to physically and electrically couple a battery distribution conductor to the DC bus 230. Unlike DC power plants that are located proximate to a central battery system (e.g., in a central architecture), the remote battery connection 240 is sized for the battery distribution conductor that connects the DC power plant 200 to a central battery system that is distal. In contrast, the DC power plant is located proximate a load instead of the battery system. As such, the proximate load connection 250 is sufficiently sized to physically and electrically connect DC distribution connections to the DC bus 230.

The processor 222 includes the necessary hardware and software to direct the operation of the DC power plant 200 including the rectifier system 210. For example, the processor 222 may be a digital data processor that is programmed or stores executable programs of sequences of software instructions to perform one or more of the described functions. The software instructions of such programs may be encoded in machine-executable form on conventional digital data storage media, e.g., magnetic or optical disks, random-access memory (RAM), magnetic hard disks, flash memories, and/or read-only memory (ROM), to enable various types of digital data processors or computers to perform one, multiple or all of the described functions of the controller 220. As such, the processor 222 is configured to monitor a distal battery current generated by the rectifier system 210 for a remote battery system and dynamically adjust the DC output voltage to maintain the distal battery current at substantially zero amperes. The distal battery current would be located on a battery distribution conductor connected to the DC bus 230 via a remote battery connection 240.

The processor 222 may be configured to dynamically adjust the DC output voltage based on the sensed current representing the distal battery current. As such, the processor 222 may generate control signals to direct the operation of the rectifier system 210. The controller 220 may receive the sensed current via the current sensing interface 226. The sensed current may represent the different sides of a resistance current shunt coupled to the battery distribution conductor. To reduce the battery current to substantially zero amperes, the processor 222 is configured to use the sensed current to determine the voltages on the two different sides of the resistor of the current shunt. The processor 222 is then configured to adjust the DC output voltage so that the two voltages match (i.e., are substantially the same). As such, the distal battery current is reduced to zero or substantially zero amperes.

FIG. 3 illustrates a schematic diagram of an embodiment of a DC power system 300 constructed according to the principles of the disclosure. The schematic diagram of FIG. 3 illustrates how currents may be sensed to zero out battery current on the battery distribution conductors between DC power plants and centrally located battery systems during normal operation. The DC power system includes a DC power bus 310, a battery charger 320, a battery system 330, three DC power plants 340, 342, 344, battery distribution conductors 350 connecting the DC power plants 340, 342, 344, to the DC power bus 310 and three resistance current shunts 360, 362 and 364. The resistance current shunts 360, 362, 364, allow currents to be sensed in each battery conductor. Employing the resistance current shunts 360, 362, 364, also allows a calibrated reading of the battery current on the battery distribution conductors 350. The DC power plants 340, 342, 344, receive the sensed currents and determine the voltage on either side of the current shunt resistance. The DC power plants 340, 342, 344, (i.e., the controller thereof) then dynamically determine the voltage needed on the power plant side of the resistance current shunts 360, 362, 364, for the voltages on either side of the current shunt resistance to match or at least substantially match. The DC power plants 340, 342, 344, then dynamically adjust the DC voltage and, therefore, substantially reduce the battery current on the battery distribution conductors 350 to obtain or at least substantially approach zero amperes. As noted above, the resistance current shunts 360, 362, 364, allow a calibrated reading of the battery currents. However, in some embodiments, when a calibrated reading of the battery currents is not needed, the resistance current shunts 360, 362, 364, can be eliminated and the resistance of the battery distribution conductors themselves can be used.

FIG. 4 illustrates a schematic diagram of an embodiment of a DC power system 400 constructed according to the principles of the disclosure that uses the resistance of the battery conductors instead of resistance current shunts for zeroing-out current on the battery conductors. The DC power system 100 illustrated in FIG. 1 may be configured as the DC power system 300 or the DC power system 400 for reducing the battery current on the battery distribution conductors. As illustrated, the DC power system 400 does not include resistance current shunts. Instead, the DC power plants 340, 342, 344, employ the resistance of the battery distribution conductors 350 to determine how to dynamically adjust the DC voltage output to reduce the battery current to zero. In this embodiment, the value of the resistance is not relevant since the control circuit (i.e., processor of the controller) in the DC power plants 340, 342, 344, is being used to force the current to zero instead of to a calibrated value as done when using a resistance current shunt.

FIG. 5 illustrates a flow diagram of an embodiment of a method 500 of reducing a distal battery current carried out according to the principles of the disclosure. The method 500 may be carried out by a DC power plant located proximate with a load to prevent battery current from the DC power plant to a remote battery system during normal operation. A controller of a DC power plant including a processor may include the necessary circuitry and sequence of operating instructions to perform the method 500. The processor may be directed by the stored sequence of operating instructions to perform the method 500 or at least a portion thereof when the sequence is initiated. The method 500 begins in a step 505.

In a step 510, a sensed current is received from a location on a battery distribution conductor connecting the DC power plant to a remote battery system. The remote battery system is a centrally located battery system that is distal from the DC power plant and the load or loads proximate the DC power plant. The sensed current may be received from a resistance current shunt associated with the battery distribution conductor. In one embodiment, the location may be on the DC power plant side of the resistance current shunt. In some embodiments, resistance of the battery distribution conductor may be used to distinguish between the sensed currents. In a step 520, a DC output voltage of the DC power plant is dynamically adjusted based on the sensed current to reduce the distal battery current to substantially zero amperes. Whether employing a resistance current shunt or employing the battery conductor resistance, dynamically adjusting includes matching voltages on either side of the resistance as determined from the sensed current to reduce the battery current to zero. As such, the DC output voltage of the DC power plant is dynamically adjusted to match the voltage on the other side of the resistance. The method 500 then ends in a step 530.

The present disclosure provides a DC power plant architecture that employs cost efficient battery technology with the DC efficiency obtained by co-locating the DC power plants with the load equipment. Additionally, the DC power plants are configured to reduce current on the battery distribution conductors to ideally zero amperes during normal operation. Furthermore, a dedicated battery charger is provided to allow easier optimization of the charging current.

The disclosed architecture of the DC power system also allows for the DC power plants to be placed in load cabinets. Thus, the DC power plant 200 may be located in a cabinet with the load to further reduce DC distribution losses. While this may be used for new installations, the disclosed architecture can also be implemented with existing centralized architectures without significant changes to distribution and load wiring. Accordingly, installation costs and potential service interruptions can be minimized.

Those skilled in the art to which the invention relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments without departing from the scope of the invention.

Claims

1. A power plant, comprising:

a rectifier system including an AC power input and a DC power output, said rectifier system configured to receive an AC input voltage at said AC power input and produce a DC output voltage at said DC power output; and

a controller configured to monitor a battery current associated with a battery distribution conductor coupled to said rectifier system for a remote battery system and dynamically adjust said DC output voltage to maintain said battery current at substantially zero amperes.

2. The power plant as recited in claim 1 wherein said controller is configured to dynamically adjust said DC output voltage based on sensed current representing said distal battery current.

3. The power plant as recited in claim 2 wherein said controller includes a current sensing interface configured to receive said sensed current.

4. The power plant as recited in claim 1 further comprising a DC bus coupled to said DC power output.

5. The power plant as recited in claim 4 further comprising a cabinet, wherein said rectifier system, said controller and said DC bus are included in said cabinet.

6. The power plant as recited in claim 4 wherein said DC bus includes a remote battery connection.

7. The power plant as recited in claim 4 wherein said DC bus includes a proximate load connection.

8. A DC power system, comprising:

a DC power bus;

a battery system coupled to said DC power bus;

a battery charger coupled to said DC power bus;

primary DC distribution interrupting devices coupled to said DC power bus; and

a power plant coupled to said DC power bus through said primary DC distribution interrupting devices, said power plant located remotely from said DC power bus, said battery system and said battery charger.

9. The DC power system as recited in claim 8 wherein said power plant is coupled to said primary DC distribution interrupting devices via battery distribution conductors.

10. The DC power system as recited in claim 8 wherein said battery charger is dedicated to providing battery charging current for said battery system.

11. The DC power system as recited in claim 8 wherein said power plant includes:

a rectifier system including an AC power input and a DC power output, said rectifier system configured to receive an AC input voltage at said AC power input and produce a DC output voltage at said DC power output, and

a controller electrically configured to monitor a distal battery current generated by said rectifier system for said battery system and dynamically adjust said DC output voltage to maintain said distal battery current at substantially zero amperes.

12. The DC power system as recited in claim 11 wherein said controller is configured to dynamically adjust said DC output voltage based on a sensed current representing said distal battery current.

13. The DC power system as recited in claim 12 wherein said controller includes a current sensing interface configured to receive said sensed current.

14. The DC power system as recited in claim 13 further comprising a resistance current shunt coupled to battery distribution conductors connecting said DC power output to said primary DC distribution interrupting devices, wherein said sensed current is provided by said resistance current shunt.

15. The DC power system as recited in claim 11 further comprising a DC power distribution center located proximate to said power plant and coupled to said DC power output thereof.

16. The DC power system as recited in claim 15 wherein said DC power distribution center is a battery distribution fuse base.

17. The DC power system as recited in claim 8 further comprising multiple DC power plants coupled to said DC power bus via said primary DC distribution interrupting devices.

18. A method of reducing a battery current associated with a rectifier system of a DC power plant, comprising:

receiving a sensed current from a location on a battery distribution conductor connecting said DC power plant to a remote battery system; and

dynamically adjusting a DC output voltage of said DC power plant based on said sensed current to reduce said battery current to substantially zero amperes.

19. The method as recited in claim 18 wherein said sensed current is received from a resistance current shunt coupled to said battery distribution conductor.

20. The method as recited in claim 19 wherein said location is on a DC power plant side of said resistance current shunt.