| 摘要 |
1300226 HVDC transmission systems ENGLISH ELECTRIC CO Ltd 5 May 1970 [9 May 1969] 23662/69 Heading H2F A circuit for controlling an inverter 19 (e.g. for an HVDC transmission system) is arranged to operate the inverter at a fixed extinction angle when the inverter current is greater than a first predetermined level and to operate at constant current when the inverter current tends to fall below a second predetermined level less than said first level and has additional extinction angle control means for modifying the extinction angle if the inverter current is between said first and second predetermined levels, said modified extinction angle being greater than said fixed extinction angle by an amount which varies in dependance upon the difference between said first predetermined current level and the actual inverter current so as to provide stable operation between said first and second current levels. As described, the inverter 19 has a first control loop 36, 34, 31 arranged to provide constant current operation in response to the difference between the desired current signal I01 and the actual current as monitored by a D.C. current transformer 37. At higher levels of current in the D.C. transmission line 16, constant extinction angle operation is achieved, the angle being monitored at 39 and compared with a desired extinction angle signal 41. A further amplifier 42 compares signals 37 and I01 and has inherent saturation limits such that when the line current falls below the desired value a progressively increased extinction angle is ordered. Diodes 32, 33 arrange that the loop having the larger output takes control. The rectifier 10 may be provided with a current control loop 28, 27.
|
