DC voltage limit compliance in voltage-source converter based multi-terminal HVDC

By adjusting V/sub ref/, the voltage reference setting of the DC voltage regulator or the power reference settings P/sub i//sup sp/ of the remaining converter stations, the steady-state DC bus voltages of the voltage-source converter based multi-terminal HVDC system can be made to comply with voltage limits. When any one of the converter stations is lost, over-voltage can destroy a converter station within a fraction of a second. As there is no time to reset the settings, the references must be determined in the very beginning to anticipate the accidental loss of a converter. The paper shows how the well-known voltage sensitivity method and the Lagrange multiplier method are adapted successfully to determine the reference settings for pre- and post-fault conditions.