Novel passivity-based controller design for Back-to-back STATCOM with asymmetrically structured converters

This paper describes a nonlinear controller for a type of voltage-source converter based high voltage direct current called Back-to-back static synchronous compensator (BTB STAT-COM) system with asymmetrically structured converters. The BTB STATCOM employs a pulse width modulation technology for a rectifier station and a multipulse technology for an inverter station. To improve robustness and simplify controller design, a passivity-based controller (PBC) using Euler-Lagrange form is proposed for this system. The PBC, which consisted of the desired control input and a new control input considering the performance of all states, is designed based on error dynamics. The control input based on the Lyapunov theorem guarantees the exponential stability of equilibrium point of the system. The proposed method is validated through simulation and its effectiveness is compared with an input-output linearization controller. Simulation results show that PBC enhances the performances of the states of the inverter and DC voltage.