Predictive Fast DSP-Based Current Controller for a 12-Pulse Hybrid-Mode Thyristor Rectifier

This paper proposes a novel 12-pulse hybrid-mode thyristor rectifier (HMTR) that can operate in either parallel mode or series mode with the help of a switch. No matter in which mode it operates, the proposed 12-pulse HMTR keeps the same pulses in the load current. It is designed to operate in parallel mode when low output voltage is required and in series mode when high output voltage is required. This way, the firing angle of the thyristor is reduced and thereby the total harmonic distortion (THD) in the input current is improved. The predictive current control strategy is also proposed to achieve the hybrid-mode operation. Fast current response is achieved both in parallel and series modes as well as in transitions between parallel and series modes. The concept of the proposed predictive current control scheme is quite simple and understandable, and easy to be implemented by a microprocessor. This paper includes analysis, simulation, experiment, and a comparison of the proposed control method with the conventional PI controller. Results from both simulation and experiment demonstrate the validity of the proposed 12-pulse HMTR and the effectiveness of the predictive current control algorithm.