In this thesis, a new four-level rectifier topology based on unidirectional switches is proposed. Rectifiers are extensively used in industrial applications as one of the main power electronic energy conversion systems. Conventional high-power rectifiers usually inject considerable low frequency harmonics to the grid. Therefore, the researchers have been trying to modify the existing converter topologies or present new topologies to reduce the distortion imposed by conventional rectifiers. The multi-level rectifiers are a proper solution for medium and high-power applications. In multi-level rectifiers, as the number of voltage level increases, the quality of input current is improved. But at the same time, the number of switching components, as well as the complexity of the system, is also increased. In this thesis, a novel 4-level rectifier topology is proposed with reduced number of active power switch. The switching states and the operation of the proposed rectifier is studied. A space vector modulation technique along with appropriate controller are implemented. A proper algorithm is proposed to balance the flying capacitor voltages. Using the PSIM software, the simulation results are provided for the 3L-Vienna, the C and the proposed rectifiers with considering a specific high-power medium-voltage industrial application. In comparison with the C and proposed topologies, the 3L-Vienna has the lower number of voltage level, higher blocking voltage of the switches and more limited inductor reactance. The simulation results show that the C and the proposed topology have the identical input voltage and current waveforms, equal blocking voltage of switches and the same efficiency. The main advantage of the proposed topology is the lower number of active switches, which is 9 as compared to C topology. In order to verify the practicability of the proposed topology, a scaled-down prototype is implemented and the associated results are presented. Key Words: Rectifier, Four-level topology, Modulation, DSP, Flying capacitor, VOC controller
