Siemens Aktiengesellschaft

Siemens Aktiengesell Schaft

Stephan Weiss

Karl-Friedrich Leowald

Franz-Josef Unterlass

A method and apparatus is described for generating a synchronizing signal for a firing-circuit subassembly to trigger a power converter valve of a controlled series compensator. According to the invention, a sinusoidal substitute variable is provided, which can be either a measured line current or the sum of a capacitor current and a valve current, such that the zero crossings of said substitute variable do not vary. This substitute variable is modified in terms of its phase position so that a synchronizing signal that corresponds to the phase position of the capacitor voltage of the series capacitor of the controlled series compensator is made available to the firing-circuit subassembly. The result, even in the bypassed state, is a sinusoidal synchronizing signal whose zero crossings do not vary, so that operating stability problems no longer occur in the transient state during operation close to resonance.

Method and apparatus for generating a synchronizing signal for a

A method and an apparatus for relieving a capacitor of a controlled series compensator as a function of the load on its arrester when high-current line faults occur. The current flowing through the arrester is used to determine its absorbed energy, from which a temperature gradient is then determined as an indicator of a sudden load on the arrester and compared with a limit value. This comparison value is processed, as a function of the determined actual arrester temperature and the measured line current, to yield a control signal. The power converter valve of the controlled series compensator is triggered in response to this control signal in such a way that its equivalent impedance is switched from capacitative to inductive. The number of disconnections required as a result of high-current line faults is thereby considerably reduced, thus greatly increasing availability of the system.

Method and apparatus for relieving a capacitor of a controlled series

A method and a device for recognizing defects in a triggering system of a controlled series compensator. An intervention is made in the closed-loop control of the controlled series compensator on the basis of an impedance differential (.DELTA.Z) determined from a setpoint impedance (Z.sub.S1, Z.sub.S2) and from an effective impedance (Z.sub.i) calculated from system variables (i.sub.L,u.sub.C), and in dependence upon the voltage level of a measured conduction current (i.sub.L). When the conduction currents (i.sub.L) are smaller than a limiting value (i.sub.LG), the firing is blocked in the branches, and when the conduction currents (i.sub.L) are greater than a limiting value (i.sub.LG), a firing-angle signal (S.sub..alpha.S) is generated, through which means the valve (Th1, Th2) can be protectively fired. Thus, one is able to recognize defects in the triggering system of the controlled series compensator by applying system variables (i.sub.L,u.sub.c), and this series compensator is able to be brought into such a state that disadvantages are avoided for the network operation, through which means the availability of the system and the quality of the compensation are increased.

Method and apparatus for recognizing defects in a triggering system of a

A method and an apparatus for symmetrically modulating a controlled series compensation system (2) in electrical networks (6). Impedance manipulated variables determined from a current control for the series compensators (14) of the system (2) are limited by determining an upper or lower limiting value (Z.sub.OO,Z.sub.OU). The upper and lower limiting values are respectively determined by adding a positive or negative deviation (.DELTA.Z.sub.+,.DELTA.Z.sub.-) to and subtracting it from a reference manipulated variable (Z.sub.O) for impedance. The reference manipulated variable (Z.sub.O) for impedance is selected from the impedance manipulated variables (Z.sub.y1,Z.sub.y2,Z.sub.y3). Thus, small asymmetries can be corrected and, given network faults of generally only a brief duration, unnecessary control deviations can be avoided.

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Mergentheim, Germany

Stephan Weiss