Model Predictive Control Strategy for Multi-Phase Thyristor Matrix Converters - Advantages, Problems and Solutions

A 27-to-3-phase thyristor matrix converter using a model predictive control (MPC) is considered. Compared to the standard method the MPC considers the coupled overall system. Due to this, all 273 19683 switching states are to be considered. The result of the MPC strategy is, compared to classical control, a drastic reduction of the commutation frequency and respectively the converter losses. However, besides the advantages there are still some problems with the use of MPC for thyristor matrix converter. Therefor this contribution presents extensions of the standard direct model predictive control strategy to overcome these problems. The result is a predictive control structure with a fallback level for problematic working areas. By this, a low total harmonic distortion (THD) as well as a high efficiency can be achieved.