Abstract:
Two different nonlinear control methodologies based robust Sliding Mode Control
(SMC) for HVDC LightTM transmission system's possessing parameters uncertainties
are proposed. Appropriate feedback signals are formulated to control the active and
reactive powers towards their specified set point values and to govern the DC link
voltage to its desired value. The first controller maintains the active and reactive powers
to their anticipated rated values using their corresponding reference signals directly. The
other uses an additional auxiliary controller based proportional-integral (PI) controller
or the two degrees of freedom proportional-integral-derivative (2DOF-PID) controller to
govern the DC voltage and to generate the necessary direct and quadrature currents
reference signals that are inserted to the main controller based SMC in order to control
the corresponding powers. The controllers' gains are adjusted using Lyapunov method
to guarantee zero tracking error in order to ensure the system's stability. The feasibility
and effectivity of both control techniques are evaluated in terms of performance
enhancement and their robustness are compared under parameters uncertainties and
verified for different DC link lengths using MATLAB©.