Mitsubishi Denki Kabushiki Kaisha

Shotaro Murakami

Masahiko Akamatsu

Yasuhiko Hosokawa

Shinzo Tamai

Fuminori Nakamura

Tomohiko Aritsuka

Takeaki Asaeda

A compensation control device for a power system includes a switched capacitor connected in series with a transmission line, a voltage applying control connected in series with the transmission line, and a ganged control for controlling on/off operation of the switched capacitor and a linearizing voltage generated by the voltage applying control. The control ensures that a sum voltage of a stepped voltage generated across the switched capacitor and the linearizing voltage produced by the voltage applying control and that is applied to the transmission line is continuous. The control device realizes controllability of the total impedance of the transmission line and reduces the capacitance of the parts employed in the ganged control.

Compensation control device for a power system

A voltage source type power converting apparatus having voltage source type power converter units and phase-shifting transformers. The transformers have either a common multiple-phase primary winding or a group of parallel connected multiple-phase primary windings, either of which being connected in parallel or series to a multiple-phase AC system. The transformer further include a group of multiple-phase secondary windings with phase differences with respect to each other and which are connected to voltage source type power converter units. The voltage source type power converter units are operated with the phase differences. Accordingly, the construction of the multiplexing phase-shifting transformer is simple, and fundamental electric variables can be controlled by a simple phase controlling operation. In addition, a higher harmonic defect of the AC system can be reduced, and the DC voltage can be easily raised.

Voltage source type power converting apparatus

A power system compensator apparatus comprising a power converter unit that works in series with the transmission of a power system and switching control means for controlling the link voltage (V.sub.LINK) of the non-power system side. The switching control means controls the phase of, at least, the fundamental frequency of the power system. The power converter unit contains a static power converter transformer with phase differences taking place the secondary windings of the power converter unit. The static power converter unit is operated in non-PWM or fixed pulse width ratio. Switching rate is minimized. Loss is lowered while economy of operation is improved. Since the voltage that works in series with the power transmission line is controlled, direct compensation of system reactance voltage and direct control of line current are performed. Improved performance thus results.

Power system compensator apparatus and power converter apparatus

A power converter protecting apparatus include series transformers connected in series to phase power lines, respectively, of an electric power system, power converters connected to secondary windings of the transformers, respectively, a current detector for detecting system currents flowing through the phase power lines, a current detector for detecting converter currents flowing to the power converters from the secondary windings, respectively, a high-speed decision circuit for outputting a decision signal upon determination of occurrence of a system fault on the basis of the system current, a switch for issuing an output voltage zero command upon reception of the fault decision signal, and a pulse generating circuit for controlling a gate pulse signal supplied to the power converters for setting to zero the outputs of the power converters in response to the output voltage zero command at a time point when the converter current decreases below an allowable breaking current thereof.

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Tokyo, Japan

Shotaro Murakami