A digitally based HVDC firing-pulse synchronization control-description and model development

The design and basic operation of a digitally based DC firing-pulse synchronization control is described. A discrete-time model, suitable for small-signal analysis is also presented. The basic dynamic performance of the loop indicates good regulation capability for changes in firing angle order from the primary regulator and for changes in the AC supply frequency or phase angle. The potential for steady-state error during rapid AC supply system acceleration was identified, and improved performance was achieved by modifying the frequency input portion to the firing-angle correction path. By developing a small-signal model of the synchronizing function, the authors lay the foundation for further control system stability analysis which examines the impact that the AC and DC systems have on the synchronizing loop and vice versa