A Microcomputer-Based Commutation Failure-Free Control System for the Cascaded Rectifier Circuit

A Z80 microcomputer-based control system for the cascaded single-phase rectifier circuit is presented. The cascaded rectifier circuit is composed of two thyristor bridges, that is, one is the conventional bridge and the other thyristor bridge with forced commutation. This circuit configuration is adopted to improve the input power factor. The system uses the microcomputer to generate the required firing pulses to the thyristors and to monitor the commutating process. Once the commutation failure is detected, the gating sequence is changed to return the system to the normal condition, thus realizing the commutation failure-free thyristor converter.