APPARATUS AND METHOD FOR CONTROLLING A FORCE COMMUTATED INVERTER

Apparatus And Method For Controlling A Force Commutated Inverter 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 synchronize 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.