A Hybrid Cascaded Multilevel Inverter with Diode Assisted Boosting Network

Abstract This paper investigates a diode assisted cascaded H-bridge multilevel inverter to serve as an alternative to the traditionally available pulse width modulated inverters for large hybrid electric vehicle (HEV) drive train applications. This research extends earlier work which involved constant equal dc sources with invariant behaviour to include variable dc sources which improves its voltage transfer ratio and the voltage rating of the capacitors is thus reduced. The implemented diode assisted cascaded H-bridge MLI uses lower power rated switches, can be used for active as well as reactive power compensation and contains less number of switching devices and isolated DC sources. The proposed method results in equalized current stresses across all the components. A modified carrier-cascaded PWM method is used to accomplish the control of the inverter and equalization of voltage. Investigation of the total harmonic distortion is done for a wide range of possible output control voltages and a number of voltage levels are used to obtain the desired waveform.. Theoretical analysis is verified by simulation in MATLAB/Simulink environment and experimental implementation.