Dr. Jenny Z. Zhou, Senior Supervising Engineer, Teshmont Consultants LP, Canada.

Speech Title: Investigation, Control and Mitigation of SSTI and SSCI Associated with HVDC and Wind Plant Installations

Abstract: Sub-synchronous torsional interactions (SSTI) occur when an interaction happens between an HVDC link, FACTS device, or other power electronic controller and the mechanical mass system of a generator. The power electronic controller can exhibit negative damping at sub-synchronous frequencies, which can cause un-damped or growing oscillations in the known mechanical torsional modes of oscillation in the generator shaft system. Sub-synchronous control instability (SSCI) phenomenon is a control interaction that can occur between any power electronic devices, such as wind turbine, and a series-compensated system. The oscillations resulting from SSCI may grow very quickly. Another SSCI phenomenon is the interaction between power electronic controllers such as grid-connected inverters for renewable energy sources integration. Such resonances can be both sub-synchronous and super-synchronous and may lead to inverter control instability and other dynamic problems when the connected grid is becoming weak. The objective of this presentation is to give a guide on how to identify potential where SSTI and/or SSCI may be an issue; how to study the phenomena; how to control, mitigate, and/or protect against any adverse effects associated with these interactions; and potential types of system changes or additions that would require equipment owners and/or operators to re-examine their system for the possibility of SSTI and/or SSCI.