Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1997-05-05
1999-03-30
Sterrett, Jeffrey
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
363 37, 363 95, 307 66, H02M 540
Patent
active
058896597
ABSTRACT:
A method of delivering an optimized power level from a backup energy system to a load connected to a primary energy supply via a DC link and an inverter is provided. The method has the steps of: sensing a voltage of the DC link connected to the load; connecting a converter between the backup energy supply and the DC link; evaluating a rate of change of the voltage of the DC link; determining an estimate of the average load current using the rate of change of the DC link voltage; and controlling the converter using the average load current to switch the optimized power output from the backup energy supply to the load. In an embodiment, the step of determining an estimate of the average load current using the rate of change of the DC link voltage is performed in accordance with a formula I.sub.load =C.sub.DC link (dV.sub.DC link /dt). Also, the step of evaluating a rate of change of the DC link voltage is performed by representing a plurality of DC link voltage samples taken over time as points in an x-y coordinate system connected by a best fit line such that the slope of the line represents the rate of change of the voltage of the DC link. Further, the step of evaluating the rate of change of the DC link voltage may be implemented using a first plurality of serially connected sample and hold amplifiers having a second plurality of difference amplifiers selectively connected to the first plurality of sample and hold amplifiers and an operational amplifier summer connected to sum outputs of the difference amplifiers to produce an output. The output is used to control the converter for an optimized power level output switchover.
REFERENCES:
patent: 4707774 (1987-11-01), Kajita
patent: 4709318 (1987-11-01), Gephart et al.
patent: 4719550 (1988-01-01), Powell et al.
patent: 5204548 (1993-04-01), Dahler et al.
patent: 5315533 (1994-05-01), Stich et al.
patent: 5602462 (1997-02-01), Stich et al.
Sterrett Jeffrey
Superconductivity, Inc.
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