Robust control of a power supply system for an arc heater

In this work we deal with the problem of controlling the current in an electric arc heater by means of the delay angle of a 70 MW electric power system thyristor bridge. To guarantee the current regulation inside the arc heater we propose a control scheme consisting of two actions: a feedforward control action obtained off-line by means of a numerical nonlinear inversion of the model and implemented on-line with a look-up table to guarantee the perfect regulation in absence of external disturbances, and an output feedback control action to counteract possible disturbances acting during the operating of the arc heater. Since the electric linearized model depends on a number of uncertain parameters, the feedback control action is designed so as to guarantee robust stabilization of the closed loop; moreover constraints regarding the speed of convergence are imposed. Simulation results are provided for the whole nonlinear scheme