Abstract: A problem to be solved by the present invention is to eliminate variation in potential in a turn-off time period of each GTO element, and to stabilize a gate drawing current by surely performing the turn-off of the GTO element. In an inverter apparatus having a three-phase inverter configured to include paired GTO elements an inverter control portion has a simultaneous switching prevention function of delaying a turn-on operation of each of the GTO elements which correspond to phases other than a phase corresponding to an optional one of the GTO elements and also correspond to an electrode opposite to an electrode corresponding to the optional one of the GTO elements by a predetermined time in a case where a turn-on command signal for turning on each of the GTO elements is generated within a predetermined time period since the turn-off of the optional one of the GTO elements.

Abstract: A problem to be solved by the present invention is to eliminate variation in potential in a turn-off time period of each GTO element, and to stabilize a gate drawing current by surely performing the turn-off of the GTO element.

Abstract: Frequencies fx between the measurement harmonic (mth-degree harmonic) and the (m±1)th-degree harmonics are determined from an expression of fx=(fs*m)±{(fs/n)*k)} where n and k are each an integer. Currents of inter-harmonics of the frequencies fx above and below the measurement harmonic are injected into an inject point in a power system in n cycles of the fundamental wave. Voltage at the inject point based on the injected currents and currents at least either upstream or downstream from the inject point are measured. Admittances for the inter-harmonics above and below the measurement harmonic on at least either the upstream or downstream side from the harmonic inject point are calculated from the measurement results. Interpolation processing based on the calculation results is performed, thereby finding and determining an admittance for the measurement harmonic.