Modular uninterruptible power supply

• US 20010033502A1
• Filed: 02/20/2001
• Published: 10/25/2001
• Est. Priority Date: 02/18/2000
• Status: Active Grant

• Current Assignee: Vertiv Corporation (Vertiv Holdings Co.)
• Original Assignee: Liebert Corporation (Vertiv Holdings Co.)
• Inventors: Blair, Charles F., Birchmeier, John R., Crawford, Christopher, Weber, Dennis, Reinbolt, Brad, Gabel, Mark
• Granted Patent: US 6,700,351 B2
• Time in Patent Office: Days
• US Class Current: 363/65
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Claims

1. a method of equalizing output current among a plurality of alternating current devices connected in parallel, the method comprising:

measuring an output current of each device, thereby generating a plurality of output current signals;

selecting an output current signal having the largest magnitude, designated the highest output current signal;

providing the highest output current signal to a control input of each device;

comparing the output current signal for each device to the highest output current signal;

adjusting the output current of each device to match the output current corresponding to the highest output current signal.

2. A circuit for equalizing output current among a plurality of alternating current devices connected in parallel, the circuit comprising:

a plurality of current sensors, each having an output signal corresponding to an output current of a corresponding alternating current device;

a selection circuit having inputs receiving output signals from each current sensor and having an output signal corresponding to the current sensor output signal having the greatest magnitude;

a plurality of summing circuits, each having a first input receiving a corresponding current sensor output signal and having a second input receiving the selection circuit output signal, each summing circuit generating an output error signal corresponding to the difference between the selection circuit output signal and the corresponding current sensor output signal;

a plurality of control circuits, each receiving as an input the corresponding error signal and adjusting the output current of the corresponding alternating current device to minimize the magnitude of the error signal.

3. A power module comprising:

a PWM-controlled inverter

a current sensor, having an output signal corresponding to an output current of the power module;

a selection circuit having a first input receiving the output signal from the current sensor and having a second input receiving a signal corresponding to a highest output current of one or more other power modules connected in parallel with the power module, said selection circuit generating an output signal corresponding to larger of the current sensor output signal and the highest output current signal from the other power modules;

a summing circuit, having a first input receiving the current sensor output signal and a second input receiving the selection circuit output signal, the summing circuit generating an output error signal corresponding to the difference between the selection circuit output signal and the current sensor output signal;

a PWM inverter control circuit, receiving as an input the error signal and adjusting a PWM signal supplied to the inverter so as to cause the output current of the power module to minimize the magnitude of the error signal.

4. An uninterruptible power supply comprising one or more power modules in accordance with

claim 3

connected in parallel.

10. The UPS of

claim 9

further comprising one or more power modules in accordance with

claim 3

.

5. A method of equalizing output current among a plurality of alternating current devices connected in parallel, the method comprising:

measuring an output power level of each device;

adding the output power levels for each device to arrive at a total output power;

dividing the total output power by the number of devices to derive an output power setpoint;

adjusting the output power of each device to match the output power setpoint.

6. An intelligent battery module comprising at least one battery string, a fuse, and a relay, all connected in series, the battery module further comprising a microprocessor based controller for monitoring and controlling the battery module components.

7. The intelligent battery module of

claim 6

wherein the microprocessor monitors the charge status of the battery strings.

8. The intelligent battery module of

claim 6

wherein the microprocessor controls the relay to disconnect the battery strings from a UPS bus when a failure of the battery strings is detected.

9. A UPS comprising one or more battery modules in accordance with

claim 6

, wherein the battery modules may be accommodated in any bay of the UPS frame.

11. A method of battery module status monitoring comprising:

setting an empirical energy rating to an initial value corresponding to a manufacturer'"'"'s rating of the battery module;

setting a present energy value equal to 0.9 times the initial empirical energy rating;

determining the deliverable energy of the battery by multiplying the initial present energy by a temperature derating factor and a load derating factor;

updating the present energy value to account for charging or discharging of the battery;

updating the deliverable energy to account for temperature or load changes;

updating the empirical energy rating at the end of a substantially full discharge cycle to equal the sum of the total energy delivered by the battery during the discharge cycle and the present energy value at the end of the discharge cycle.

12. A method of determining the battery run time of a UPS comprising a plurality of battery modules comprising the steps of:

determining the present energy stored in each battery module;

determining the deliverable energy stored in each battery module by multiplying the present energy of each battery module by a temperature derating factor and a load derating factor;

determining the run time of the UPS by adding the deliverable energy of each battery module and dividing by the total load on the UPS.

13. A method of determining the state of charge of a plurality of battery modules in a UPS comprising the steps of:

determining an empirical energy rating for each battery module;

determining the present energy stored in each battery module;

determining the state of charge of the battery modules by adding the present energy of each battery module and dividing by the sum of the empirical energy rating for each battery module.

14. A floating safe connector consisting essentially of:

a connector housing receiving a standard connector; and

a plurality of locking tabs on the connector housing to retain the housing in the plane of an opening in a frame;

wherein the opening in the frame is sufficiently larger than the connector housing to allow the connector housing to move within the plane of the opening, and wherein the connector housing shrouds the energized parts of the standard connector.

15. A method of minimizing an interruption of an output voltage of a UPS during a bypass transition, the method comprising:

minimizing the time required for a bypass contactor to change states;

centering the time required for the contactor to change states about a zero crossing of the output waveform.

16. The method of

claim 15

wherein minimizing the time required for the bypass contactor to change states is accomplished by overdriving a coil of the bypass contactor.

17. A shipping pallet comprising:

a pallet frame;

a plurality of padded feet affixed to a bottom of the frame;

a metallic bracing member affixed to the frame.

18. The shipping pallet of

claim 17

wherein the metallic bracing member may be configured as a ramp for unloading the pallet.

19. A method of adjusting the state of charge of a battery module in a UPS, the method comprising:

periodically receiving time and date stamps from a control module;

storing the time and date stamps in a battery module controller memory when the battery module is removed from the UPS;

computing a time the battery module has been removed from the UPS when the battery module is re-inserted; and

adjusting the battery'"'"'s capacity information to account for charge capacity lost during the time the battery module was removed from the UPS.

20. A method of adjusting the state of charge of a battery module in a UPS, the method comprising:

periodically receiving time and date stamps from a control module;

storing the time and date stamps in a battery module controller memory when the UPS is turned off;

computing a time the UPS has been turned off when the UPS is turned back on; and

adjusting the battery'"'"'s capacity information to account for charge capacity lost during the time the battery module was removed from the UPS.