Modeling and analysis of AC/DC converter system with digital PI controller

A digitally controlled AC/DC converter system with a current control loop, based on a single-phase half-controlled thyristor bridge is presented. Three type proportional plus integral (PI) controller is described. When a digital PI controller is employed, in which the integral term is replaced by the summation one, the control system becomes a multirate sampled-data system having two different sampling rate. This paper gives the modeling and analysis procedures on the digitally controlled system including a multirate sampled-data system. For this control scheme, a microprocessor is used to implement the feed-back control and calculates the firing angle in real-time.