This invention relates to an apparatus for controlling a D.C. power transmission system having a line-commutated converter which is connected between a first A.C. system and D.C. power transmission lines and which performs power conversion between A.C. power and D.C. power, and a forced-commutated converter which is connected between the D.C. power transmission lines and having a second A.C. system and which performs power conversion between A.C. power and D.C. power. In order to control transmission power in the two-terminal D.C. power transmission system wherein the two A.C. systems are associated by direct current, a control apparatus for a D.C. power transmission system according to this invention includes a voltage detector which detects a D.C. voltage of the D.C. power transmission lines, a first control circuit for comparing the output of the voltage detector with a voltage reference signal and for controlling ignition of the self-excited converter in accordance with the comparison, a detector which detects a current which is proportional to the conversion power of the line-commutated converter, and a second control circuit for comparing the output of the current detector with a power reference signal and for controlling ignition of the line-commutated converter in accordance with the comparison.

Control apparatus for D.C. power transmission system

An AC electrical motor is normally energized from an inverter which in turn is coupled to a rectifier. An alternator driven from a variable speed source supplies energy to the rectifier. During start-up non-regulated output energy of the alternator is passed directly to the motor until the system approaches operating speed. After start-up, the motor is energized from the inverter at the appropriate normal operating voltage and frequency. The system may be used in a car, where an alternator energizes the motor driving a compressor in the air conditioning system.

Start-up system for inverter driven motor including inverter bypass circuitry

A method and apparatus for regulation of the power factor of a 3-phase network fed with power from another 3-phase network via a short high-voltage direct current transmission link interconnecting the two networks. The d.c. transmission link includes rectifier and inverter stations connected at opposite ends of the link and the inverter station is controlled in such manner as to supply power to the fed network at a variable leading power factor in dependence upon the actual power factor of the fed network.

Short HVDC transmission system with power factor control

A static converter circuit has a voltage summing transformer (Tr-Tr13) with several part transformers (Tr1-Tr13) the static-converter-side winding of which are connected via one four-quadrant actuator each to a direct-voltage link circuit. The four-quadrant actuators are single-phase bridge circuits with one GTO thyristor each and a diode, which is antiparallel thereto, per bridge branch. The static-converter-side windings of the part transformers can be short circuited in each case by means of an alternating-current circuit breaker with antiparallel-connected thyristors. Each part transformer has a separate core. The power-system-side windings of the power transformers are connected in series and are connected at their ends to a railroad power system with 162/3-Hz. The direct-voltage link circuit is connected via power-system-commutated static converters and a static converter transformer to a national power system with 50 Hz. For generating an approximately sinusoidal alternating voltage part voltages of equal amplitude which are supplied by the part transformers are added and/or subtracted step-by-step in the voltage summing transformer. Each thyristor of a four-quadrant actuator is turned-on and turned-off at the most, twice per period of the alternating voltage. This reduces power losses and expenditures for cooling the semiconductor components. The static converter circuit is suitable for frequency converters and reactive-power compensators.

Static converter circuit and method for controlling it

In a current-source GTO converter, protection against a DC fault or a commutation fault condition is provided by immediately interrupting the conduction of a GTO device which is ON and by turning ON another GTO device to allow fault current to bypass the bridge or safely pass through the bridge. As a result, protective action is immediate and an early recovery is made possible. Bypassing of the bridge is done by freewheeling, with an auxiliary GTO switch or with one of the main GTO switches. Diversionary action is done through the bridge by changing the mode of operation of the bridge from rectifier to inversion, or conversely.

Static-controlled current-source AC/DC power converter and DC/AC power converter, and protection system embodying the same

A static converter composed of a converter-transformer and a rectifier bridge connected thereto has a bypass member connected in parallel with the bridge. Two series-connected rectifiers in one phase of the bridge constitute a bypass path. A direct voltage source can be connected with said two bypass rectifiers, the source having such a polarity as to furnish a current in the conducting direction of the two rectifiers.

By-pass connection of static converters

Power transmission equipment for high voltage direct current

A converter is formed of a group of rectifiers arranged in series with reactors. A protection device is provided which includes a short-circuiting arrangement for the rectifiers. The reactors are provided with iron cores which are saturated at approximately 1 percent-10 percent of the short-circuiting current of the converter.

Converter comprising a rectifier group containing reactors and an over-current protection for the rectifier group

In order to improve the performance of series connected thyristors these are provided with an individual electrode connected to a n-layer or a p-layer nearest the anode respectively the cathode of each thyristor. A separate DC voltage source supplies this electrode with a voltage, called booster voltage, and is connected in such a circuit that the source in the case of a chain of a number of series connected thyristors serves simultaneously two adjacent thyristors in the chain.

Carl Ingvar Boksjo

Papers

By-pass connection of static converters

Power transmission equipment for high voltage direct current

Converter comprising a rectifier group containing reactors and an over-current protection for the rectifier group

Booster voltage circuit for series-connected thyristors