Method for controlling a static converter in an HVDC power transmission system and a converter with control means for carrying out the method

摘要

A method for controlling a converter in an HVDC power transmission system and a converter with appropriate control means for carrying out said method. The current regulator influences the control angle of the converter in dependence on the difference (I0-Id- DELTA I) between, on the one hand, the measured current (Id) and, on the other hand, the current order signal (I0) decreased by a current margin value ( DELTA I), controlling the converter with a control angle which is dependent on the one hand, on a proportional component being linear proportional to said difference and, on the other hand, on an integral component corresponding to the time integral of said difference. The current regulator has a proportional regulator part (PR) and an integrating regulator part (INT1). The output signal of the integrating regulator part is limited in the upward direction to a value corresponding to a maximum value of the control angle of the converter. The output signals from the integrating and the proportional regulator part are added to form the output signal of the current regulator. The limiting value of the integrating regulator part is calculated by a calculating circuit as a function of the current order and the ideal direct voltage of the converter. The calculation is made by determining the control angle at which, at a load current equal to the current order, the extinction angle becomes equal to the smallest permissible turnoff angle. From this angle there is then subtracted the output of the proportional unit at a current equal to the current order, and the result constitutes the limiting value for the integrating regulator part.