For solving the problem of low frequency oscillation in multi-area interconnected power system linked with VSC-HVDC

we proposed a constant transmission capacity damping control method for VSC-HVDC which keeps the voltage sourced converter’s transmission capacity constant based on the oscillation transient energy theory. This method solved the problem caused by converter’s modulation ability limitation by using active power and reactive power to suppress power oscillation simultaneously. Firstly

we deduced a correlation between converter’s active（reactive） power modulation and system damping according to transient energy consumed by the damping of system. Then

we proposed a constant transmission capacity method and designed the parameters of the proposed controller. Finally

a traditional damping controller designed by pole place theory was designed as a contrast to identify the performance of the proposed controller. The simulation results show that the proposed constant transmission capacity damping controller can suppress low frequency oscillation efficiently and have strong robustness. Besides

the proposed damping controller can take full use of active and reactive power modulation capacity of voltage sourced converter while keeping the transmission capacity constant

and has no restrictions on converter’s modulation ability.