| 摘要 |
PCT No. PCT/SE90/00425 Sec. 371 Date Nov. 19, 1991 Sec. 102(e) Date Nov. 19, 1991 PCT Filed Jun. 15, 1990 PCT Pub. No. WO90/16104 PCT Pub. Date Dec. 27, 1990.A system for discharging electrical power from a high-voltage direct-current (HVDC) transmission line to a local network, utilizes a first, single-phase converter bridge comprising semiconductor switches which are energized by signals and which are de-energized solely with current zero crossing, and a first, single-phase transformer having a primary winding connected to a HVDC line and a secondary winding; a second converter bridge connected to the secondary winding; a secondary direct voltage network connected to the second converter bridge; a third converter bridge connected to the secondary direct voltage network for generating an alternating current for the local network; and the second and the third converter bridges each comprise ON/OFF controllable semiconductor switches, and the first and the second converter bridges commutate with a frequency that is 2-4 times higher than the normal frequency of the local network and the third converter bridge commutates at the normal frequency of the local network. |
