چكيده به لاتين
Power electronics converters have various applications such as transportation, motor drives, and medium voltage. Different converters with various structures have been proposed in numerous papers which some of them have been implemented in industrial scales. In these converters parameters like number of devices, blocking voltages, number of current sources, switching frequency, reliability, total harmonic distortion, and modulation technique are issued.
In this disseration, two modified H-bridge five-level inverters and a three-phase multi-level inverter have been proposed. The inverters have the lower number of switches than the similar structures, and this feature causes low implementation cost. Simulation results have been discussed from view of point of power loss, and implementation results have been taken for a 3kVA laboratory prototype.
By using the proposed single-phase topologies, three-phase structures have been proposed, and three novel structures of three-level, five-level, and seven-level proposed. In the three-level structure the minimum number of switches has been used which this factor cannot be found in other structures. Also, all the proposed three-phase structures have been implemented for a 5kVA load. In order to obtain the modular connectivity, a modified structure with modular capability is proposed.
Besides mention parameters, the proposed structures have been extended, and their modular structures have been presented which these structures can be used in multiphase systems, four-leg or photovoltaic applications. Also, to reach better performance and obtain low harmonic components a novel method for switching scheme is proposed. The proposed pulse width modulation technique is gives rise to decreasing the voltage Total Harmonic Distortion. To examine the performance of the proposed modulation technique, the proposed inverters have been used in simulation and experimental tests. In comparison with typical pulse width modulation methods, the presented pulse width modulation approach produces low harmonic parts in the voltage of output with lower switching frequency. The OCP-PWM has been applied to the proposed single phase five-level inverter and output voltage THDv decreased to 21.79%. Also, for the proposed three-phase three-level inverter, THDv is 27%. To investigate the reliability of the presented pulse width modulation scheme for single-phase five-level converter and three-phase inverter a 3kVa/400v prototype is carried out by applying a TMS320F28335 digital signal processor.
