Abstract: A method and apparatus for determining the quenching angle in inverter valves, in which the pulse-shaped deviations, which occur in the valve voltages due to the current commutations as compared to the corresponding fundamental waveforms, are blanked out in the form of voltage blocks. For the duration of the quenching angle, a binary measuring signal is generated which is triggered by an end-of-conduction pulse and is terminated by a zero voltage crossing pulse. The end-of-conduction pulse indicating the completion of the commutation is formed by the flank at the end of the voltage shift caused by the preceeding commutation in the valve voltage as compared to the fundamental waveforms.

Abstract: The orthogonal components of the voltage vector of an a-c voltage network are transformed by means of a vector rotator, smoothed and transformed back. The frequency of the transformation elements required for the transformation in the vector rotator is set during a network disturbance under controlled conditions in accordance with a stored frequency value. After the end of the network disturbance, the direction given by the smoothed transformed orthogonal components is controlled to a reference value in that the frequency of the transformation elements is readjusted according to the direction deviation. The phase of the transformation elements determines the phase of the co-system fundamental of the network. A counter system fundamental can also be taken into consideration.

Abstract: In a first station operating as the rectifier, a fault indication quantity can replace the measured value of the HVDC voltage which regulates a control voltage. In normal operation in a second station of an HVDC transmission system operating as an inverter, a fault indication quantity is calculated from a control angle and the inductive D.C. voltage drop is calculated from the D.C. current and the A.C. voltage. In the second station operating as the inverter, the overlap angle can be precalculated from a fault indication quantity so that by automatic control of the control angle a preset extinction angle can be assured. Thereby stable, quickly controllable operation without any remote control signals is assured and rapid resumption of operation following a malfunction facilitated.

Abstract: Method and Apparatus for resumption of normal operation of a High Voltage Direct Current transmission line after a malfunction in one of two stations connected to a HVDC transmission line. A control angle of approximately 90 degrees is run up in the previously malfunctioning station in accordance with a given function, thus creating an indication quantity at the D.C. voltage connections of the other station, which is detected as the earliest possible information on the start of the external station and also enables the run-up of the control angle in accordance with a given run-up function, with the two run-up functions representing precalculated, compatible, actual substitute values for the fault indication quantity caused by the respective other station. At the end of the run-up, the run-up functions are switched over to measured values of fault indication quantities, thus attaining stable control with short run-up and control times.

Abstract: A method and apparatus are described for operating a high voltage d.c. (HVDC) transmission line system connecting two a.c. transmission line systems during normal operation and during malfunction in either the rectifier station or the inverter station of the HVDC system.When a malfunction exists in one station of a HVDC transmission line, such as a rectifier station, then the regular thyristor firings are disabled and a bypass circuit, preferrably one or several bridge paths of a converter, are fired. As soon as a corresponding change in the current or voltage occurs at the d.c. voltage connections of the other station, this station assumes rectifier operation during which the HVDC transmission line is utilized as a reactive load to stabilize the other system. Once the malfunction has ceased to exist, operation is first resumed in the first station by extinguishing the bypass thyristors and subsequently resumed also in the other station.