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AssigneeAsea Brown Boveri AG
InventorsPer-Erik Bjorklund, Tomas Jonsson, Lars-Erik Juhlin
Estimating the term…
A series-compensated converter station included in an installation for transmission of high-voltage direct current comprises a converter (SR1, SR2) with at least one 6-pulse bridge (BR). Via series capacitors (SCR, SCS, SCT) the 6-pulse bridge is connected to a three-phase alternating-voltage network (N1, N2) with a fundamental frequency (f.sub.01, f.sub.02). Control equipment (CE1, CE2) generates an ordered value (AOL) of a control angle (.alpha.) for valves (V1-V6) included in the 6-pulse bridge in dependence on a limiting signal (AMAXL) capable of being influenced. An amplitude signal (AMPL) is formed which corresponds to the amplitude (C.sub.1) for a component (C.sub.1 cos(2.pi.f.sub.0 t+.phi..sub.1)) of the fundamental frequency in the direct voltage (Udb) of the 6-pulse bridge and a compensating signal (ACOMP) is continuously calculated in dependence on a sensed voltage (Un1, Un2) at the converter station and on the amplitude signal. The limiting signal is formed in dependence on the compensating signal for the purpose of maintaining the commutating margin (.gamma..sub.m) for the valves equal to at least the preselected value (.gamma..sub.p) in case of unbalance between the voltages (UCR, UCS, UCT) of the series capacitors. (FIG. 6)
A method for controlling a series-compensated converter station included in an installation for transmission of high-voltage direct current, said converter station comprising a converter (SR1, SR2), controlled by control equipment (CE1, CE2), with at least one 6-pulse bridge (BR), said 6-pulse bridge via series capacitors (SCR, SCS, SCT) being connected to a three-phase alternating-voltage network (N1, N2) with a fundamental frequency (f.sub.01, f.sub.02), said control equipment generating an ordered value (AOL) of a control angle (.alpha.) for valves (V1-V6) included in the 6-pulse bridge in dependence on a limiting signal (AMAXL) capable of being controlled, said method comprising the steps of:
A device for control of a series-compensated converter station included in an installation for transmission of high-voltage direct current, said converter station comprising a converter (SR1, SR2), controlled by control equipment (CE1, CE2), with at least one 6-pulse bridge (BR), said 6-pulse bridge via series capacitors (SCR, SCS, SCT) being connected to a three-phase alternating-voltage network (N1, N2) with a fundamental frequency (f.sub.01, f.sub.02), said control equipment generating an ordered value (AOL) of a control angle (.alpha.) for valves (V1-V6) included in the 6-pulse bridge in dependence on a limiting signal (AMAXL) capable of being controlled, and voltage measuring devices (UM1, UM2) for sensing the direct voltage (Udb11, Udb12, Udb21, Udb22) of at least one of the 6-pulse bridges, wherein the control equipment comprises an amplitude-value forming unit (AVU), which is supplied with a measured value (UDM) of the direct voltage of at least one of the 6-pulse bridges and forms an amplitude signal (AMPL) corresponding to the amplitude (C.sub.1) for a component of the fundamental frequency in the direct voltage (Udb) of the 6-pulse bridge, a calculating unit (CALC2), which is supplied with said amplitude signal and a value (UDI01, UDI02) of the ideal no-load direct voltage (Udi01, Udi02) and forms a compensating signal (ACOMP) in dependence on a continuously calculated value of a control-angle addition (.DELTA..phi.), calculated in dependence on a voltage (Un1, Un2) at the converter station and on the amplitude signal according to a relationship (H0, H1) which at least approximately imitates a relationship according to which the control-angle addition, at a commutating margin (.tau..sub.m) for the valves equal to a preselected value (.tau..sub.p), is a function (F0) of a current (Id1, Id2) in the converter station, said voltage at the converter station and the amplitude (C.sub.1) for said component of fundamental frequency in the direct voltage of the 6-pulse bridge, and wherein the limiting signal is formed in dependence on the compensating signal for the purpose of maintaining the commutating margin (.tau..sub.m) for the valves equal to at least the preselected value (.tau..sub.p) in case of unbalance between the voltages (UCR, UCS, UCT) of the series capacitors.
Dependencies are inferred from the claim text.