CONVERTER CONTROL SYSTEM WITH TAPPED TRANSFORMER PROVIDING CONSTANT NO-LOAD SECONDARY VOLTAGE

摘要

1440368 Automatic voltage control HITACHI Ltd 7 Aug 1973 [12 Aug 1972] 37423/73 Heading G3R [Also in Division H2] In an HVDC power transmission system (see Division H2) an inverter transfers power from a D.C. line to the secondary of a 3-phase tapped transformer, the primary of which is connected to an A.C. network. The no-load secondary voltage is maintained constant by the arrangement shown, which operates by monitoring the primary voltage Ea and by rectifying at RD and smoothing at Ra, Ca. The monitored voltage is compared with a reference voltage - Vcc adjusted by switches S1 .... Sn and resistors Ro ... Rn 1 so as to provide an indication of which tap of the transformer is in use. An error signal is produced by amplifier A11 and feeds a controller LD arranged to alter the tap on the transformer in such a way as to maintain constant the no-load secondary voltage. The change of tap ceases when the reference voltage - Vcc has been changed sufficiently by switches S1 ... Sn to equalize the new value of primary voltage. This arrangement eliminates the effect of periodic short circuiting of the secondary of the transformer during commutation of the inverter.