Modeling, analysis and design of a thyristor-based bi-directional ac-dc converter

This paper presents the modeling, analysis, and design of a thyristor-based ac-dc converter, featuring bi-directional power flow and unity power factor at the ac side in both powering and regenerating modes. By applying the y-parameter modeling technique and eliminating the effects of the high-frequency poles and zeros, small-signal models of the converter in both modes and a unified controller have been developed. The controller regulates the voltage at the dc side and operates as a feedback controller in the powering mode and a feedforward controller in the regenerating mode. Systematic procedures for determining the circuit component values of the power conversion stage and the controller are presented. The operation is illustrated with the design of a 500-W, 100-V (ac)/200-V (dc) prototype, supplying to a motor-generator set. Experimental results showing operation in the powering mode, regenerating mode, and during mode changeover are included. Circuit operations during the transient of the changeover operation are clearly identified.