Feedback linearization for the DC voltage control of a VSC-HVDC terminal

This paper investigates the use of feedback linearization to develop a control system for regulating the DC voltage and the reactive power of a VSC terminal. Firstly, a direct-quadrature (dq) state-space model of the VSC terminal is established. By analyzing the zero dynamics of the system, the static feedback linearization can be applied when the VSC terminal operates in inversion mode (power flowing from the DC side to the AC one). However, the system is not feedback linearizable when the VSC works in rectification mode (power flowing from the AC side to the DC one). Then, based on a simplified model, a new dynamic is introduced by an additional control variable which yields a higher order system, allowing the terminal to operate in rectification mode. Numerical simulations are carried out to verify the validity of the proposed control system.