Current-fed Quasi Z-source Inverter-topology And Control

Current-fed quasi Z-source inverter (CF-QZSIs) is an enhancement to Z-source inverter (ZSIs). Current-fed quasi Z-source inverter is different from the conventional Z-source inverter which includes the lower components rating decreased source stress and prosaic control synthesis. The conventional current-source inverter (CSI) has two major problems: unidirectional power flow and voltage boost operation, which makes it impossible to use in many applications such as hybrid electric vehicles and general-purpose variable-speed motor drives. With its distinct structure, the CF-QZSI inverter can insert a novel open-circuit zero state in the traditional zero states to buck the output voltage,which improves the inverter dependability greatly,and provides a tantalizing single stage dc-ac conversion that is able to buck and boost the voltage.For dedications with a variable input voltage,this inverter is a very competitive topology.This thesis starts with the discussion of the circuit structure and its operating principle. Mainly focuses on the modulation methods include SVPWM method and their digital implementation with FPGA,and it involves the design of the novel inverter. Three PWM methods are proposed with different boost ratios. In order to reduce the switching loss, a modified SVPWM scheme presented. A comparative study of the modified SVPWM method and a commonly used PWM method conducted.This thesis presents a comprehensive study on the new features of the CF-QZSI including the advantageous buck-boost function, improved reliability,reduced passive components rating and unique regeneration ability. In the end of the thesis, some simulation results are provided to verify the validity of the theoretical analysis.