Digital current control of a thyristor-based converter using a DSC

The design and construction of a thyristor-controlled converter based on a Digital Signal Controller, suitable for high power applications is presented in this paper. The converter topology developed is based on an three-phase six-pulse arrangement, where tasks associated with control and digital signal processing are performed in a digital signal controller. The control system is developed in a discrete time domain using a zero order hold representation for the power converter. Besides, a PI digital controller is developed for a constant-current closed-loop operation, providing significant improvements in stability, dynamic behavior and response of the converter to external perturbations. Simulations carried-out in the Simulink program confirm that the converter operates with a wide range of firing angles, including operation with sudden perturbations such as change to load. Further experiments carried out in the laboratory with the prototype prove that the DSC-based control system corrects waveform distortion due to asymmetrical or distorted power supply by implementing an equidistant firing control scheme.