Research on PI controller tuning for VSC-HVDC system

Dual closed loop structure is often adopted in VSC-HVDC control system, and the PI controller design and parameters tuning can be regarded as the core content in the control system design. This paper first designs the inner current loop follow three methods: typical I-type, typical II-type and second-order system, designs outer voltage loop under the low-frequency model, and then the step response and dynamic performance under different methods is analyzed through simulation. In order to improve the system stability, a novel strategy is also proposed for the outer voltage loop based on cutoff frequency and phase margin. Simulation is carried out to testify the feasibility of this strategy and shows that the PI parameters tuned by this method can drop into the actual value range, and the system's performance can be satisfied, which proves the correctness of this novel strategy.