Stability properties of certain thyristor-bridge control systems. Part 1: The thyristor bridge as a discrete control system

The paper is concerned with the stability of thyristor-bridge control systems and develops the theoretical basis for the bridge model and its implications. A further paper will use the theoretical results to investigate new and existing design procedures. The present paper contains a description of the particular control schemes being studied. This is followed by a theoretical study of the bridge as a discrete control element, and a subsequent justification of the sampler and zero-order-hold model. Analysis of this model when operating with 1st- and 2nd-order systems is then made using z transformation and root-locus techniques. This results in simple design rules, which are then used as an illustration of some general properties of stable thyristor-bridge control systems.