Static converter circuit and method for controlling it

摘要

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.