Uninterruptible power supply

Details Uninterruptible power supply Uninterruptible power supply

1999-07-29

2001-02-06

Ballato, Josie (Department: 2836)

Electrical transmission or interconnection systems

Plural supply circuits or sources

Substitute or emergency source

C307S080000

Reexamination Certificate

active

06184593

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to power transmission and distribution systems, and more particularly to a novel Uninterruptible Power Supply (UPS) designed to be coupled to at least one auxiliary source of ac power.
BACKGROUND OF THE INVENTION
FIG. 1
is a one-line diagram of a typical arrangement of a main ac supply (e.g., power grid)
10
, an on-line UPS
12
, a load
14
and a battery bank
16
. The on-line UPS typically contains a controlled rectifier DR
1
, a dc-to-ac inverter A
1
, a static bypass switch S
1
, and isolation transformers T
1
and T
2
(T
2
is typically a nine-winding transformer, with a three-phase primary for S
1
, a three-phase primary for A
1
and a three-phase secondary for the load). The dc bus
12
-
1
is designed specifically to support the bank of batteries
16
. The bus can provide charging current and also draw current from the batteries in the event of an outage on the main ac supply
10
. UPSs usually contain a static (electronic) bypass switch S
1
so that the output of inverter A
1
can be switched to the main supply
10
in the event of a fault or high inrush load.
FIG. 2
depicts an example of a system employing an auxiliary generator
18
in combination with a UPS
12
. Battery supplied UPSs provide backup power for short periods of time, typically on the order of minutes. The backup time can be substantially increased by adding a generator to the system. This is typically accomplished using an automatic transfer switch S
2
at the input of the UPS
12
, as shown in FIG.
2
. When the main ac power supply
10
fails, the batteries
16
supply power to the UPS. If the power remains down for a predetermined period of time, the automatic transfer switch S
2
will start the auxiliary generator
18
and switch the UPS
12
input to the auxiliary generator output through S
2
.
The solution shown in
FIG. 2
has several drawbacks:
1. The controlled rectifier DR
1
in the UPS
12
tends to draw harmonically rich currents that are not easily handled by the generator
18
. It is therefore necessary to oversize the generator or to add substantial filtering in front of the UPS. Both of these solutions increase cost and losses.
2. Operating the generator
18
in grid-parallel mode requires added complexity. Circuitry must be provided for synchronizing the generator with the grid (i.e., the mains
10
). In most circumstances, parts must also be added to prevent the generator from generating power into the grid in the event of a power failure.
Accordingly, a goal of the present invention is to provide a combined UPS/auxiliary generator system that avoids the problems discussed above, and that provides improved compatibility with many forms of stored or generated energy.
SUMMARY OF THE INVENTION
The present invention provides an electronic circuit, such as, e.g., a UPS, for interfacing a main ac power source and at least one secondary power source to a load. The secondary power source(s) may include one or more auxiliary generators, a flywheel motor generator or microturbine with high speed motor generator, and/or any of a variety of dc storage devices. The electronic circuit, which in a presently preferred implementation is a UPS, comprises a dc bus, a first uncontrolled rectifier in combination with a first filter for coupling the main ac power supply to the dc bus, a second uncontrolled rectifier in combination with a second filter for coupling the auxiliary generator to the dc bus, and a dc-to-ac inverter (between the dc bus and the load) for providing ac output power to the load.
As discussed in greater detail below, the present invention provides a combined UPS/auxiliary generator system that avoids the problems of the prior art and offers improved compatibility with many forms of stored or generated energy. Other features of the present invention are disclosed below.


REFERENCES:
patent: 5198971 (1993-03-01), Recker et al.
patent: 5610452 (1997-03-01), Shimer et al.
patent: 5612581 (1997-03-01), Kageyama
patent: 5646458 (1997-07-01), Bowyer et al.
patent: 5694307 (1997-12-01), Murugan
patent: 5745356 (1998-04-01), Tassitino, Jr. et al.
patent: 5745670 (1998-04-01), Linde
patent: 5767591 (1998-06-01), Pinkerton
patent: 5939798 (1999-08-01), Miller
patent: 5994794 (1999-11-01), Wehrlen

Affiliated with

Also associated with

Rating

Uninterruptible power supply does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Uninterruptible power supply, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Uninterruptible power supply will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2568065