Use of Wind Farm Converter Controls for Transmission System Support under Voltage Stability Emergencies

This paper investigates the effect of reactive support by Wind Farms (WF) on the maximum power transfer, and thus the voltage stability limit of a transmission system. In particular, an insecure snapshot in a weak area of the Hellenic Interconnected System is examined. Several WFs in this area are connected to HV/MV substations through MV distribution feeders. MV feeder characteristics and substation controls, i.e. feeder resistance and reactance, automatic switched capacitive compensation, LTC controls, are all modelled in detail. Most importantly, the limits of the available capacity for reactive support, as well as the overvoltage limitations on the MV feeder, are taken into consideration in assessing the effect of the WFs.