Electrical transmission or interconnection systems – Plural supply circuits or sources – Connecting or disconnecting
Patent
1996-12-19
1998-09-15
Elms, Richard T.
Electrical transmission or interconnection systems
Plural supply circuits or sources
Connecting or disconnecting
307127, H02J 304
Patent
active
058083782
ABSTRACT:
A control arrangement and method is provided for high-speed source-transfer switching systems (HSSTSS). The HSSTSS supplies an electrical load with alternating current from either a first source or a second source via respective first and second solid-state switches. The HSSTSS also includes a controller that samples the voltage waveforms of each of the first and second sources to detect when transfer between the sources is desirable, e.g. outages or voltage that is either too low or too high. The controller provides appropriate control signals to control operation of the solid-state switches and transfer supply of the load therebetween. The control arrangement avoids undesirable current flow between sources via a comparison of the voltages of the sources and current in the outgoing source, i.e. a polarity comparison to ensure that the current that will flow in the incoming source after transfer will be in opposition to the current flowing in the outgoing source before transfer. Thus, the transfer is delayed until the polarity comparison is satisfied. Either separately or in combination with the polarity comparison, the control arrangement minimizes undesirable transfer delays by establishing a forced commutation condition before issuing control signals to perform the transfer between sources, i.e. the transfer is delayed until after a forced commutation condition of the current in the outgoing source is established. The forced commutation condition is preferably established by the incoming source voltage differential and the outgoing current being of the same polarity such that the voltage differential across the solid-state switch that is being turned on will establish an initial change in current flow in opposition to the current flow in the solid-state switch to be turned off.
REFERENCES:
patent: 4356402 (1982-10-01), Morimoto et al.
patent: 5644175 (1997-07-01), Galm
Elms Richard T.
Lapacek James V.
S & C Electric Company
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