Damping of Power Swings in AC Tie Lines Using a Parallel DC Link Operating at Constant Reactive Power Control

This paper presents a method for the damping of power swings in the ac lines interconnecting two power systems, utilising the fast electronic power flow control characteristics of a parallel dc link. The basic principle of the method is that the dc link is operated in order to maintain constant active power flow in the ac tie lines and constant reactive power consumption at the converter terminals. The proposed control strategy was tested using dynamic simulation techniques and the results obtained show that, under certain conditions, the contribution of a parallel dc link to the stability the ac system can be significant.