Utilizing MPC Controlled Multilevel Neutral Point Clamped Rectifier for Supplying Loran Transmitter

The present work studies a model predictive controlled two- and three-level active front-end rectifier system for supplying LORAN transmitter system. Up to now, the LORAN transmitters have been supplied by only diode rectifiers, which inject sever harmonics into the AC network and induce a very low input power factor when supplying pulsed loads. Therefore, an MPC-controlled active rectifier system with three level neutral point clamped topology is proposed to attenuate the input current harmonics and improve the input power factor. Compared with the conventional methods (e.g. voltage oriented control (VOC), direct power control (DPC)), the proposed control method provides such advantages as improved power quality indices, reduced switching frequency, and simplicity for controlling different indices just by changing the weighting factors of the relevant cost function. The results of comparing these thee methods demonstrate that the MPC method could not only give a power factor close to unity and negligible harmonic distortion, but also very lower switching frequency, as compared to the two other methods. Using the MPC, VOC, and DPC control methods, the switching frequencies for a typical load were found to be 11.3, 74.5, and 60 kHz, respectively. Moreover, the intuitive logic and easy implementation of the MPC method, compared to the two other ones, besides achieving an improved operating point with a lower cost, represent the other important advantages of the MPC method.