Tokamak modelling and control

This thesis is concerned with the modelling and control of tokamak nuclear fusion reactors. A nonlinear model is derived using the classical arguments of Hamiltonian mechanics from which a low-order linear model is derived. The modelling process addresses flux and energy conservation issues explicitly and self-consistently, and shows the relationship between the initial modelling assumptions and the resulting predictions. The mechanisms behind the creation of uncontrollable modes in tokamak models are discussed. A system identification procedure is applied to the large JT-60U tokamak in Japan to identify the open loop response from closed loop experiments. The measured time and frequency domain responses are predicted accurately by the model. Parametric model optimisation methods are developed and applied to further improve the model fit. A normalised coprime factorisation H-infinity controller is developed for the TCV tokamak in Switzerland using the verified linear model. Recent theory is applied to reduce the controller order significantly whilst guaranteeing a priori bounds on the robust stability and performance. The controller is shown to successfully track reference signals that dictate the plasma's shape, position and current. The tests used to verify this were carried out on linear and nonlinear models. (author)