Modelling and control of switched circuits for high power applications

grantor: University of TorontoThis thesis presents exact modelling and control techniques for high power, slowly switched circuits. Long standing continuous time circuit approximations are abandoned, and discrete time modelling techniques are developed. The discrete time modelling approach is shown to account for all harmonic interaction effects introduced by the switching events. The approach may be employed to solve for the true cyclic steady state of a switched circuit and to characterize its dynamics via a linearization about this cyclic steady state. Applications of this linearization to both stability analysis and control design are demonstrated. The exact analysis techniques developed for slow switching circuits are also expanded for application to the pulse width modulated inverter. Time averaging in the 'dq'-frame is proposed, yielding a discrete time, time varying 'dq'-frame inverter model. Averaging in the synchronous reference frame is shown to offer several benefits over established ' abc' and ab -frame time averaging approaches. A new 'dq'-frame control is developed based entirely on discrete time concepts. Performance is maximized by eliminating unnecessary integral components in the control algorithm. Step tracking, however, is ensured through introduction of a bias estimation procedure. Experimental results from a laboratory setup are used to validate both the proposed model and control.Ph.D