A Self Commutated Power Converter for Stabilizing Torsional Interactions

A recently proposed method of counteracting torsional interactions referred to as transmission current feedback involves the measurement of the transmission system currents from which the subsynchronous components that produce torsional interactions are extracted. Once extracted, these are suitably amplified by a power converter and injected into the generator bus of the affected steam turbine so as to cancel the original subsynchronous components which would otherwise produce torsional interactions. In this paper, a power converter capable of supplying the required subsynchronous currents is described. An analytic model relating the converter output currents to its controlling variables is derived and a suitable control strategy is formulated. A detailed hybrid computer simulation of the converter is used to verify the accuracy of the analytic representation of the converter and the effectiveness of the control strategy.