| 摘要 |
1,258,974. Controlling HVDC transmission systems. ENGLISH ELECTRIC CO. Ltd. 12 June; 1970 [24 June, 1969], No. 31799/69. Heading H2F In a telecommunication control system for a HVDC system, a first control unit 1 associated with one converter transmits a signal 3 to a second control unit 2, associated with a second converter, control unit 2 sending back a signal 4 after checking that the signal 3 is correct, signal 4 being re-checked in control unit 1 and, if correct, allows a control signal I<SP>1</SP> to be'fed to the first converter. The checking arrangements are however, overridden if the main control signal I bears a predetermined relationship to the control signal I<SP>1</SP>. The transmission links 3; 4 may be line, radio or optical. As described, the main signal I, which may be arranged to control current or power in the link, is converted to digital at 6 and fed to a coder 12 where parity bits are included before transmission to a register 15, possible errors being checked at 16 before the output of the register 15 is gated into a further register 18 and d/a converter 19. A current margin AI is subtracted at 20 to provide the inverter conduction angle control signal I<SP>11</SP>. If signal 3' is correct a further signal is sent along link 4, which, if correct, opens a gate 24 to allow the signal from 6 to pass via stages 25, 26 to line I<SP>1</SP> where it controls the conduction angle of the rectifiers. Signals I and I<SP>1</SP> are compared in comparator 28 which sets a one-stage register 30 if the main order signal I is increasing. This arrangement allows a control signal I<SP>1</SP> to be provided under these circumstances even if a fault exists in the transmission links 3, 4. |
