| 摘要 |
PCT No. PCT/SE98/00421 Sec. 371 Date Dec. 28, 1998 Sec. 102(e) Date Dec. 28, 1998 PCT Filed Mar. 10, 1998 PCT Pub. No. WO98/21924 PCT Pub. Date May 28, 1998An active filter (2) is connected to a dc circuit (L1, L2) in a converter (SR1) in an installation for transmission of high-voltage direct current. Control equipment (5) generates, in dependence on a control signal, a control order (SCF) for the active filter which, in dependence thereon, generates and supplies to the dc connection one of a filter voltage (UF) and a filter current (IF) for reducing at least one tone of a chosen tone frequency in a current (Id) in the dc connection. The control equipment comprises a controlling unit which forms a controller signal in dependence on a supplied current measurement value (IM) of the current in the dc connection, and an identification unit. The identification unit forms a first compensating parameter in dependence on the current measurement value and on an excitation signal generated by the control equipment and added to the control order. The control equipment forms the control signal in dependence on the controlling signal and the compensating parameter, which has been formed such that the sum thereof and of the phase shift for a transfer function from the control signal to the current measurement value at the chosen tone frequency is at least approximately equal to a preselected value. |
