Abstract: A harmonic suppressing device provided in a power system such as, for example, a transmission and distribution system or a power generating system, to filter higher harmonic currents generated by a higher harmonic current source of the power system such as, for example, a cycloconverter. The harmonic suppressing device comprises, as the principal components thereof, a passive filter serving as a high-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively high order among those generated by the higher harmonic current source, and an active filter serving as low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders among those generated by the higher harmonic current source.

Abstract: A switchgear operable to conduct or shut off the a.c. current to an a.c. load by use of a semiconductor switch. The switchgear is formed such that a common thyristor switch in serial connection with a switch is connected in parallel to a switch for each of capacitor banks, so that each capacitor bank is connected or disconnected to the a.c. power line in non-contact manner through the thyristor switch.

Abstract: A static var compensator connected to a line node in a power transmission system and having a capacitor and a first reactor for producing and absorbing reactive power, respectively, and a second reactor connected between the line node and the common node of the first reactor and the capacitor for providing, in combination with the capacitor and the first reactor, a maximum leading reactive capacity so as to effectively reduce the capacities of the elements and for compensating for changes in reactive power resulting from a current fluctuation in response to a load fluctuation. The second reactor increases the reactive power produced by the capacitor when the reactive power absorbed by the first reactor is low and decreases the reactive power produced by the capacitor when the reactive power absorbed by the first reactor is high.

Abstract: A device comprising a series circuit consisting of a plurality of thyristors connected in series, and a reverse-blocking semiconductor element such as a diode connected in an antiparallel relationship to the series circuit. The device further includes means for detecting whether a sufficient turn-off time is secured for each of the thyristors anterior or posterior to a reference moment at the zero point of a current flowing in the diode, and means for turning on the entirety of the thyristors when the sufficient turn-off time is not secured. Since none of the thyristors is turned off in the state where the turn-off time is insufficient, it becomes possible with certainty to achieve exact prevention of a fault that one or more thyristors, turned off earlier than others are led to breakdown by an overvoltage.

Abstract: A method of static reactive power compensation is disclosed wherein the system voltage is compensated by supplying advanced-phase or retarded phase reactive power in dependence upon the difference between the system voltage and a reference voltage. The difference is formed by a comparator which receives a variable reference voltage from a filter containing a time lag circuit and which receives the system voltage as an input. For transients, the output of the filter does not change and thus reactive power is applied. For smooth variations, the output of the filter follows that of the system voltage so that the output of the power compensation circuit is maintained at zero.

Abstract: A control circuit of a reactive power compensation apparatus which comprises a reactor and a capacitor are connected in parallel between a power source and a load to perform phase control of current passing through the reactor by a control switching element such as thyristor. The control circuit comprises a device for detecting instantaneous value of load current at a predetermined phase of the power voltage, a multiplier, a subtractor and a divider and a device for generating gate pulse in comparison of the output signal of the divider with the rating function generated in synchronizing to the peak phase of the power voltage.