| 摘要 |
In a high-voltage d-c transmission system in which power fed in from a three-phase a-c network is rectified by thyristor valves into d-c at one station and transmitted as d-c to a receiving station where it is inverted to a-c power by thyristor valves, line-frequency overvoltage stresses on the valves are avoided, in the case of a disturbance of the type in which partial or complete dumping of the load occurs, by progressively controlling back the d-c to a value greater than zero thus to continue absorption of reactive power from the a-c feeding network. The progressive control-back involves a progressive change-over from rectifier to inverter operation by effecting a progressive change in the ignition angle for the valves. |
