Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
2001-07-05
2004-03-23
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C307S066000
Reexamination Certificate
active
06711036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed primarily to the providing of electrical power, and more particularly to an apparatus and method for independently operating a plurality of AC voltage sources in parallel.
2. Background Art
The use of energy by residential and industrial customers is at an all time high. In particular, industry often works three shifts and heavy usage of electrical power to drive energy consuming lighting and machinery is constant.
To provide quality power to an installation, free of disturbances and power interruptions, it is possible to utilize a power system which has the ability to combine electrical power from one of a storage device (i.e. battery) and an outside power supply (i.e. grid power from a utility). Such a power source is capable of generating an AC voltage waveform free of disturbances and interruptions as output. In certain instances, it may become necessary or desirable to have multiple power systems attached in parallel to power a single load (i.e., a single factory).
As voltage sources, combining the power systems together in parallel has proven difficult inasmuch as the variations in the generated AC waveforms typically conflict with each other which can lead to catastrophic failure in the power supplies. Moreover, the independent operation, activation and deactivation of such systems independent of each other would pose more difficulties and conflicts.
Thus, it is an object of the invention to combine AC voltage sources together in parallel.
It is likewise an object of the invention to facilitate the independent operation of the separate AC voltage sources.
SUMMARY OF THE INVENTION
A voltage source capable of being coupled in parallel to at least one second voltage source, having an AC waveform, to power at least one load. The voltage source comprises a power supply and a controller. The controller is associated with the power supply and includes an AC waveform generator, sensing means and shifting means. The AC waveform generator is associated with the power supply, and is capable of providing a waveform to an output. The sensing means senses the AC waveform produced by a second voltage source. The phase shifting means is associated with the AC waveform generator and with the sensing means. The phase shifting means phase shifting the AC waveform generated by the AC waveform generator, to, in turn, synchronize same to the AC waveform of the second voltage source.
In a preferred embodiment, the voltage source further includes means for buffering the output of the at least one second voltage source, to, in turn, facilitate the phase shifting of the AC waveform by the phase shifting means. In one such embodiment, the buffering means comprises an isolation transformer associated with the output.
In a preferred embodiment, an outside power source is associated with the controller. In one such embodiment, the outside power source is associated with the controller, the voltage source further comprising means for protecting the outside power source from disturbances. In one such embodiment the protecting means comprises an isolation transformer associated with the input. In another such embodiment, the controller further includes means for controlling the distribution of power between the outside power supply, the power supply and the load. In one embodiment, the controlling means further includes means for directing power from the outside power supply to at least one of the power supply and the load. In another embodiment, the controlling means further includes means for directing power from the power supply to the load.
The invention further comprises a method for attaching at least two voltage sources in parallel. The method comprises the steps of (a) providing a first voltage source; (b) supplying an AC waveform from the first voltage source to a load; (c) supplying a second voltage source; (d) supplying an AC waveform from the second voltage source to the load; (e) sensing the AC waveform generated by the first voltage source; and (f) phase shifting the AC waveform generated by the second voltage source, so that the two AC waveforms are substantially in phase.
In a preferred embodiment, the method further comprises the step of buffering voltage sources, to in turn, provide sufficient time for the step of phase shifting.
In another preferred embodiment, the method further comprises the step of attaching a first voltage source to an outside power supply. In one such embodiment, the method further comprises the step of protecting the outside power supply.
In a preferred embodiment, the method further comprises the step of attaching at least a third power supply to the at least two power supplies. In one such embodiment, the step of attaching further comprises the steps of (a) supplying a third voltage source; (b) supplying an AC waveform from the third voltage source to the load; (c) sensing the AC waveform generated by at least one of the first voltage source and the second voltage source; and (d) phase shifting the AC waveform generated by the third voltage source, so that the three AC waveforms are substantially in phase relative to each other.
REFERENCES:
patent: 4665322 (1987-05-01), Eishima et al.
patent: 5075565 (1991-12-01), Severinsky et al.
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