International Fuel Cells, LLC

Douglas G Young

Kenneth Lipman

A current balancing structure in which an alternating current output is produced by alternately connecting a DC potential to an output voltage bus through the switching action of a paralleled array of semiconductor devices forces equal current to flow through each device. During switching intervals, some semiconductor devices may 'turn-on' or 'turn-off' faster than others thus possibly forcing any conductive devices to carry a much higher current than when all the devices are conducting. Diodes protect the conductive devices by providing alternative circuit path to a DC reference potential voltage bus when one device becomes non-conductive before another paralleled device.

Current balancing structure for semiconductor switching devices

A method and apparatus is disclosed for generating thyristor gating signals for a force commutated inverter in order to produce variable frequency pulse-width modulated output waveforms with the appropriate percent fundamental voltage content for reactive power control and with the correct phase relationship to the utility line for real power control. A signal processor in conjunction with a memory is used to store individual patterns for generating a wide variety of PWM waveforms at different frequencies over the entire modulation range so as to provide the designer with the flexibility to select the most advantageous harmonic cancellation for each operating point. An embodiment of the invention .disclosed uses three microprocessors to generate the PWM waveforms and a fourth microprocessor to synhcronize the other three and produce the required phase shift. The principles disclosed apply to inverters used and controlled in parallel with a grid of real and reactive control signal commands and also those used independently by means of voltage magnitude commands.

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West Hartford, CT, United States of America

Douglas G Young