Simulation and Control of Thyristor Drives

A simulation of a thyristor drive is developed using analog computing elements and logic components for converter switching. While the simulation can be easily extended to include polyphase systems, the single-phase case is considered here primarily to study the effect of the two modes of operation, namely discontinuous and continuous armature current flow, which are of most concern in the single-phase drive. Fully and half-controlled thyristor bridges are catered for, and firing angle control may have a linear or inverse cosine relationship. Frequency and transient responses highlight the wide variation in system dynamics and point to the need for some form of adaptive control. A practical adaptive control scheme is suggested for overcoming the conduction angle dependency and is shown to give a dramatic improvement in performance.