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: A power fluctuation monitoring unit which monitors and detects the power fluctuation at a receiving point 9 by means of the measurement results of the voltage at injection point 14 of an intermediate-order harmonic current and the current at incoming line 10, a power compensation unit which forms the compensation power injection signal for canceling out the power fluctuation based on the detection results of the power fluctuation, and an inverter device 18 which is driven and controlled by the signal resulting from the addition of the intermediate-order harmonic current injection signal and the compensation power injection signal and injects the intermediate-order harmonic current and the compensation power into the injection point, are equipped.

Abstract: A power fluctuation monitoring unit which monitors and detects the power fluctuation at a receiving point 9 by means of the measurement results of the voltage at injection point 14 of an intermediate-order harmonic current and the current at incoming line 10, a power compensation unit which forms the compensation power injection signal for canceling out the power fluctuation based on the detection results of the power fluctuation, and an inverter device 18 which is driven and controlled by the signal resulting from the addition of the intermediate-order harmonic current injection signal and the compensation power injection signal and injects the intermediate-order harmonic current and the compensation power into the injection point, are equipped.

Abstract: A harmonic injection point a is set on a power line extending downstream from a harmonic measuring point b in an electric power system. The currents of interharmonics are injected to the harmonic injection point a by a current injection device. The frequencies of the interharmonics are located on both sides of the frequency of an n-th targeted harmonic in frequency spectrum and each of the frequencies is a nonintegral multiple of the frequency of a fundamental wave of an electric power transmitted by the electric power system. The current values and voltage values of the interharmonics at the harmonic measuring point are detected to thereby obtain admittance values of an equivalent circuit of a power line extending upstream from the harmonic measuring point b when the interharmonics flow therethrough. An admittance value of the equivalent circuit of the power line when the targeted harmonic flows therethrough is determined by interpolating the admittance values for the interharmonics.

Abstract: Single-phase currents at two frequencies f.alpha. and f.beta. (f.alpha.<n.multidot.fs<f.beta.) of non-integral multiples of a system fundamental wave frequency fs sandwiching an targeted harmonic (frequency n.multidot.fs) are injected between two phases of a three-phase power system as interharmonic currents. A frequency analysis of measurement current and measurement voltage of each phase in the system is carried out and a positive-phase-sequence current I1, a positive-phase-sequence voltage V1, a negative-phase-sequence current I2, and a negative-phase-sequence voltage V2 are detected for each of the two frequencies f.alpha. and f.beta. in the system based on injecting of the interharmonic currents. Positive-phase-sequence and negative-phase-sequence admittances Y1 and Y2 or positive-phase-sequence and negative-phase-sequence impedances Z1 and Z2 are found for each of the frequencies f.alpha. and f.beta. in the system as Y1=I1/V1 and Y2=I2/V2 or Z1=V1/I1 and Z2=V2/I2.