Implementation of Single Phase Cascaded H-Bridge Nine Level Inverter and Simulation Study with PI Controller

A new single phase cascaded H-bridge nine level inverter is presented in this paper. The PWM technique using multicarrier based PD (phase disposition) strategy is used to generate the pulses with the help of AT89C51 microcontroller. By varying the modulation indices value to 0.25, 0.5, 0.75 and 1, accordingly different levels of output voltages such as 3, 5, 7 and 9 levels can be achieved with R-L load. The working principle of the proposed circuit with different modes is explained in detail. In order to keep the output voltage constant and to have high dynamic performance even in the change in load condition, PI controller is used as a closed loop and verified with MATLAB/SIMULINK. In the proposed 9 level inverter with the modulation index of 1, THD of 13.55% is achieved in the output voltage. Based on power circuit component count and DC source, the proposed inverter is compared with conventional topologies. To verify the performance of the proposed architecture, simulation and experimentations are carried out on a prototype in open loop and the respective results are presented.