Transfer capability study of tie-line installed TCSC considering transient stability constraints

The transfer capability of tie-lines installed Thyristor Controlled Series Capacitor (TCSC) is studied in multi-machine systems considering transient stability constraints. Since the conversion time of TCSC mode has the important effect on transient stability, the discrete control strategy(DCS) is presented based on corrected transient energy function. The multi-machine system is divided up sending-end and receiving-end two equivalent machine systems. The moment just at which the corrected kinetic energy reach the maximum value is used as the start moment of TCSC maximum capacitive impedance in order to increase compensation degree, and the moment just at which the corrected potential energy reach especial value is used as the start moment of TCSC bypass mode in order to reduce short-circuit current. IEEE 4-generator system and New England 10-generator system are used as case studies, transfer capabilities of tie-lines considering transient stability constraints are calculated with the conventional control of TCSC and with the discrete control of TCSC, respectively. The calculation results show that the discrete control of TCSC enhances significantly the transfer capability of tie-lines in multi-machine system considering transient stability constraints compared with the conventional control of TCSC.