Capacitor commutated converter using an adaptive active capacitor for HVDC system

Thyristor rectifiers for HVDC transmission have two drawbacks, which are its sensitivity to commutation failure and its consumption of reactive power. One way to overcome these drawbacks is the use of capacitors connected between the thyristor rectifier and the AC bus. This paper introduces an approach to capacitor-commutated converter (CCC) using an active capacitor. A three-phase voltage source PWM converter is connected to resemble the effect of the capacitor. The control strategy is discussed. The simulation results are presented using PSCAD/EMTDC.