Abb Power Td & Company

John G Reckleff

Aftab H Khan

Vinod N Bapat

Kevin J Timko

Willie K Wong

Per A Danfors

Methods and apparatus for switching a load between first and second sources is shown to include first and second solid state switches connected to the load. First and second mechanical breakers are connected between the switches and the sources so that each source is connected to the load through a circuit breaker and solid state switch. A controller is connected to sense the voltage from the first and second sources. The controller is connected to the first and second switches and the first and second mechanical breakers. The controller senses the phase difference between the voltages from the first and second sources. The controller causes the first and second mechanical breakers to open and close in response to sensing the phase difference between the sources. The first and second mechanical breakers can include medium voltage vacuum breakers. In a preferred embodiment, when the controller senses that the phase difference between sources is more than 30 degrees out of phase, the controller will open the circuit breaker connected to the alternate source. In this manner voltage stress on the solid state switching devices is minimized.

Hybrid solid state switch

A dynamic mechanically-switched damping (DMSD) system is described which utilizes one or more mechanical switches and appropriate controls to switch series or shunt reactive impedances in order to provide power oscillation damping in power systems. The DMSD system provides a controller which can be configured based on the number of mechanical switches in the DMSD system, the type of reactive impedances interfaced to the power system by each switch and the magnitude of each of the reactive impedance. The DMSD system monitors parameters of the power system and the controller generates a modulation signal based on the monitored parameters. The modulation signal is processed to identify a reactive impedance of the available DMSD system reactive impedances required to damp power oscillations. Appropriate switches are selected for supplying the required reactive impedance. A switching control signal is generated and output to each of the selected switches to synchronously open or close the switch at a predetermined instant.

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Raleigh, NC, United States of America

John G Reckleff