Electricity: power supply or regulation systems – For phase shift or control – Using transformer
Patent
1995-11-01
1997-04-08
Nguyen, Matthew V.
Electricity: power supply or regulation systems
For phase shift or control
Using transformer
323212, G05F 100
Patent
active
056191197
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to AC network interconnections using susceptances, and more specifically to a method of phase-shifting voltages applied to such susceptances, and to a phase-shifting interconnecting apparatus implementing the method to control power transfers between two synchronous polyphase AC networks.
2. Brief Description of the Related Art
Hitherto, phase shifted voltages applied to susceptances of prior AC network interconnecting apparatus are produced by means of phase transposition devices and/or a judicious selection of transformer windings (e.g. combinations of Y-y, Y-d1, Y-y6, etc, -connected windings). Thus, it is possible to provide multiple angles of voltage phase-shifts by step of 30.degree. around a complete 360.degree. range. This method however has the drawback to require a transformer dimensioned to sustain the circulation of the whole power transferred by the interconnecting apparatus.
Moreover, although a continuum of phase-shift angles around 360.degree. can be obtained with partial zigzag combinations of transformer windings for the prior interconnecting apparatus, such topography is not considered in practice for reasons of efficiency.
OBJECT OF THE INVENTION
It is therefore an object of the invention to provide a method of phase-shifting voltages applied to susceptances used to interconnect two synchronous AC networks, and provide a phase-shifting interconnecting apparatus implementing the method to control power transfers between two synchronous polyphase AC networks, which overcome the above-mentioned drawbacks of the prior art methods and interconnecting apparatus.
Another object of the invention is to provide such a phase-shifting interconnecting apparatus using transformers having appreciable reduced sizes and MVA ratings with respect to the transformers required by the interconnecting apparatus of the prior art.
Another object of the present invention is to provide such a method which is effective and operative for a continuum of available phase-shift angles.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method of phase-shifting a voltage applied to at least one susceptance interconnecting a phase line of a first polyphase AC network with a corresponding phase line of a second polyphase AC network, both said AC networks being synchronous, comprising the steps of: series with said susceptance, said transformer having also a secondary winding; with respect to a phase voltage provided by said phase line of the first AC network; and winding, whereby said excitation voltage combines through said transformer with said phase voltage to cause phase-shifting of said voltage applied to said susceptance.
Preferably, the method comprises the additional step of changing an angle of phase-shifting produced by said transformer. This step is preferably carried out either by adjusting said at least a portion of the primary winding connected in series with said susceptance, or by modulating an amplitude of said excitation voltage, for changing said phase-shifting.
According to the present invention, there is also provided a phase-shifting interconnecting apparatus for interconnecting respective phase lines of first and second synchronous polyphase AC networks, said apparatus comprising, for each pair of respective phase lines subjected to an interconnection: branch points provided with connecting means for connecting respectively said branch points to said respective phase lines, said circuit branches including respectively inductive and capacitive susceptances; and one of said susceptances, said series transformer means including at least one primary winding having at least a portion connected in series with said at least one of said susceptances, and at least one secondary winding having at least a portion adapted to receive an excitation voltage derived from said AC networks, said excitation voltage having a phase angle with respect to a phase voltage provided by one of said respec
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Beauregard Fran.cedilla.ois
Brochu Jacques
Morin Gaston
Pelletier Pierre
Citeo
Nguyen Matthew V.
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