Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
2000-03-28
2001-03-13
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C363S089000, C307S105000
Reexamination Certificate
active
06201715
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to power distribution systems. More specifically, the present invention relates to synchronous frame regulation in a power distribution system.
It is not unusual for a power distribution system to have a three-phase distribution feeder that supplies multiple loads. However, different loads connected to the feeder can cause the line voltage to become unbalanced. The voltage is considered unbalanced if the line-to-line voltages are not equal. For instance, consider a situation when a three-phase motor and a single-phase load are connected to a distribution feeder line. If the three-phase motor and the single-phase load are operated at the same time, a voltage unbalance on the feeder line will occur.
When an unbalanced voltage is applied to an active rectifier, control algorithms used to regulate the active rectifier can cause third harmonic current to be generated in the power distribution system. These currents are extremely undesirable, partly because they affect the active rectifier's control and partly because they can cause overheating of the loads that receive power from the distribution system.
SUMMARY OF THE INVENTION
These problems are overcome by the present invention. According to one aspect of the invention, a system comprises a distribution feeder line; an active rectifier connected to the distribution line; and a controller for controlling the active rectifier. The controller extracts the positive sequence component of a Park vector representing the line voltage (which may contain both positive and negative sequence components), and utilizes the extracted positive sequence component to perform synchronous frame regulation to control the active rectifier. Using the positive sequence component can prevent low frequency harmonic currents from being generated in the power distribution system.
REFERENCES:
patent: 5428283 (1995-06-01), Kalman et al.
patent: 5883796 (1999-03-01), Cheng et al.
patent: 5949204 (1999-09-01), Huggett et al.
Huggett Colin
Kalman Gabor
Honeywell International , Inc.
Riley Shawn
Zak, Jr. Esq. William J.
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