Electric power conversion systems – Frequency conversion without intermediate conversion to d.c. – By semiconductor converter
Patent
1990-06-26
1991-09-10
Wong, Peter S.
Electric power conversion systems
Frequency conversion without intermediate conversion to d.c.
By semiconductor converter
363 50, 361 77, 361 84, H02M 5257
Patent
active
050479156
ABSTRACT:
A current fed unrestricted frequency converter (UFC) for supplying power with balanced voltages to a three-phase unbalanced load generates two sets of existence functions for controlling the switching matrices of the UFC to generate positive and negative sequence current components in the load. Existence function generators generating the positive and negative sequence existence functions are phase locked, respectively, to a positive sequence reference signal generated by a clock and a negative sequence reference signal derived by circuits which monitor the negative sequence voltage in the load. Select circuits alternately gate the positive and negative sequence existence functions to the UFC switching matrices in proportion to the detected magnitude of the negative sequence voltage in a sense to drive the negative sequence voltage in the load to zero. A neutral forming transformer eliminates any zero sequence voltage in the load so that all that remains is the positive sequence components of voltage which by definition are balanced.
REFERENCES:
patent: 3740638 (1973-06-01), Thorborg
patent: 3768001 (1973-10-01), Thorborg
patent: 4312030 (1982-01-01), Byers
patent: 4439823 (1984-03-01), Gyugyi et al.
patent: 4652989 (1987-03-01), Kurosawa et al.
patent: 4669024 (1987-05-01), Stacey
Gyugyi Laszlo
Putman Thomas H.
Smith Geoffrey M.
Stacey Eric J.
Lenart R. P.
Westinghouse Electric Corp.
Wong Peter S.
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