Design of a supplementary modulation control function for the Chester SVC

The Chester static volt-ampere reactive (VAr) compensator (SVC) was recently installed in New England on the 345 kV interconnection between Maine and New Brunswick. This SVC provides dynamic voltage support to prevent the rejection of generation in New Brunswick following contingencies related to the phase II high-voltage direct-current (HVDC) interconnection between Quebec and New England. As the project evolved from the planning to design stages, a control function, referred to as the supplementary modulation control, became an important aspect of the overall SVC system. The criteria and analysis necessary to design this control function are described. Stability and subsynchronous torsional interaction are considered