A kind of non-linear backstepping control strategy for back-to-back three-level VSC-HVDC system is studied

and such problem existed in the PI linear control strategy as slow dynamic response and long more stable recovery time of system is solved. According to Lyapunov stability principle

the Lyapunov function is constructed and the non-linear bus voltage and inner ring current controller are designed respectively. It is shown by the simulation and experiment result that in case of power perturbation of power grid or flow reversal

the backstepping control has superior dynamic and stable performance to traditional PI control and

at the same time

reduces greatly transient ripple of bus voltage and capacitive voltage.