| 摘要 |
A converter station (STN1, STN2) having a voltage source converter (CON1, CON2) is coupled between a direct current link (W1, W2) and an alternating current network (N1, N2) in a high voltage direct current transmission system. A control system (CTRL1, CTRL2) for the converter station has means for control of active power flow (P) between the direct current link and the alternating current network by influencing the phase displacement (gamma) between a bus voltage (UL1, UL2, UL) in the alternating current network and a bridge voltage (UV1, UV2, UV) of the voltage source converter. The control system comprises detection means (48) for generation of a phase change order signal (PCO) in response to an indication of an abnormal voltage condition at the direct current link, and means (49) for influencing the phase position of the bridge voltage in response to said phase change order signal, so as to ensure that the phase displacement between the bridge voltage and the bus voltage will result in an active power flow from the direct current link to the alternating current network.
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