DSP-based control strategies for an inverter-based compensator
The focus of this thesis is on the study and experimental implementation of a voltage source inverter-based reactive power compensator. A general mathematical model of the system has been developed, from which a approximate linearized model is derived. The approximate model introduces a simple means of characterizing the fundamental frequency behaviour of the compensator. This permits the characterization of the stationary and dynamic behaviour of the compensator in terms of the system parameters and the switching scheme used. The experimental results have verified that this approximate model represents very well the fundamental frequency behaviour of the system over the operating range of interest. Feedforward and feedback control on the dc bus voltage are also investigated. Piecewise linearization of the compensator's stationary response proved to be a good solution in overcoming the deviation from the desired values in feedforward control. Feedback control not only reduced the steady-state errors, but also improved the dynamic performance of the compensation system. It is demonstrated that the laboratory prototype behaves satisfactorily under stationary and dynamic conditions. Furthermore, details of the system hardware and software are described. Theoretical and experimental results concerning the solvability of harmonic elimination schemes are also presented.