Abstract: The accident detection circuit of the present invention is such that in a voltage-type self-excited power converter composed of anode reactors 13 and 23 connected in series, respectively, to power semiconductor elements 11 and 21 of self turn off type connected in series, there are provided anode reactor voltage direction-detecting circuits 16 and 26 which detect, respectively, that the voltage in the direction generated in the anode reactors 13 and 23 exceeds a predetermined value when the current flowing in the direction of from the anode to the cathode of the each element 11, 21 increases, anode current direction-detecting circuits 17 and 27 which detect, respectively, that the current flows in the direction of from the anode to the cathode of the each element 11, 21, delay circuits 18 and 28 which delay, respectively, the output signal of each arm current direction-detecting circuit by a certain period of time, and AND circuits 19 and 29 which designate the output signal of the each anode reactor voltage

Abstract: A control system for a power conversion system composed of a plurality of power converters, each of which is connected between one of a plurality of AC power systems and a DC line to exchange an electric power between them, respectively. The control system is composed of a plurality of control units, each of which includes units for detecting an AC current flowing between the AC power system and the power converter, an AC voltage of the AC power system, and a DC voltage of the power converter, and a unit for detecting an active power and a reactive power exchanged between the power converter and the AC power system.

Abstract: An inverter control device that controls a self-commulated inverter connected to an AC power system via a three phase transformer and in so doing suppresses DC magnetization in the three-phase transformer. The device includes a current DC component detecting circuit for detecting the current DC components contained in at least two of the three phase output AC currents of the inverter and a DC magnetization suppressor signal generating circuit for producing two correcting signals from the current DC components. The two correcting signals are used to balance in amount the three voltage DC components contained in the three phase output AC voltage of the inverter, respectively. An output reference correcting circuit is provided to correct two of first output references in accordance with the two correcting signals and output three second references including the two corrected values and one of the first output reference.

Abstract: A coupling system in which power converters are coupled through a DC circuit to exchange active power between the converters comprises a control apparatus for controlling active power exchanged between each converter and its AC system. The control apparatus includes an automatic active power regulator for regulating active power exchanged between the converters and the AC system to be equal to be predetermined active power reference value, and an automatic DC voltage regulator for regulating a DC voltage of the DC circuit to be equal to a predetermined DC voltage reference value. When an output signal from the automatic active power requlator of each converter is input as an upper limit value of an output signal from the automatic DC voltage regulator, a DC voltage reference value of one converter is set to be equal to or larger than a DC voltage reference value of the remaining power converter.

Abstract: In a DC power transmission system wherein two AC systems are interconnected by a first converter, a DC transmission line and a second converter to transmit power from one of the AC systems to the other of the AC systems via the DC transmission line, the DC power transmission system is provided wherein at least one of the first and second converters operating as an inverter is a current type self-commutated converter capable of being pulse-width controlled, the reactive power of the current type self-commutated converter is regulated by controlling a phase difference angle between its AC voltage and current, the DC voltage is regulated by pulse-width controlling the current type self-commutated converter, and the DC current is regulated by the converter operating as a rectifier.

Abstract: A power converter device that interchanges power between a first A. C. system and a second A. C. system, including an externally commutated power converter controlled such that the D. C. voltage of a D. C. line tracks a reference value, a voltage type self-commutated power converter which converts the output D. C. power of the externally commutated power converter to A. C. power under pulse width control and supplies the converted A. C. power to the second A. C. system, interchange power control means for controlling the phase difference angle of the voltage on the A. C. side of the voltage type self-commutated power converter and the voltage of the second A. C. system such that the interchange power tracks a reference value, and reactive power control means for controlling the control factor of the pulse width control such that the reactive power generated by the voltage type self-commutated power converter tracks another reference value.

Abstract: A power converter control apparatus includes an automatic power controller for controlling a rectifier and an automatic reactive power controller for controlling an inverter. The inverter is coupled via DC power transmission lines to the rectifier. An output from the automatic power controller is utilized to change a control angle (or margin angle) of the inverter if a DC current flowing through the DC power transmission lines increases to exceed a rated current value of the apparatus, thereby allowing a stable power transmission.

Abstract: A converter control system for DC power transmission line performs the following operation. When the DC current flowing through an inverter decreases to a value being smaller than a rated current value by a value in excess of a predetermined value, a reference voltage value determining the DC voltage of the inverter decreases. The decrease of this reference voltage value is limited to a given extent, so that a partial constant current characteristic portion appears at the voltage decreased portion in the DC voltage/current characteristic of the inverter. Then, an automatic voltage regulator of the inverter is rendered always active.

Abstract: In a method and a system for terminating inverter operation of a converting device connected to a DC power transmission system and having a bridge connection of thyristor valves, absence of a current flowing through the converting device is detected to provide an absence detection signal indicative of such absence, and the absence detection signal is used as one condition for effecting termination of the inverter operation. According to the invention, the absence is found when all the valves in at least one of the lower potential side and the higher potential side are found concurrently non-conducting, and each valve is found non-conducting when a voltage is found present across each valve.

Abstract: A control device for a converter used in a DC transmission system comprises an automatic current regulator, an automatic margin-angle regulator and an automatic voltage regulator. The output of the automatic voltage regulator is supplied to the automatic margin-angle regulator to vary a margin-angle reference of the automatic margin-angle regulator.