Trinary asymmetric cascaded H bridge (1:3:9) multilevel inverter with self-balanced capacitor

A single-phase trinary asymmetrical cascaded H-bridge (TACHB) inverter with a level doubling network (LDN) is proposed in this paper. It consists of a LDN and 'n' H bridges, where 'n' represents the number of DC sources. The TACHB-LDN generates N number of levels at the output voltage using log(3) (N+1/2) DC sources, 4+4 log(3) (N+1/2) and a capacitor. The TACHB-LDN gives an improved power quality output when compared with the conventional trinary CHB inverter for a given number of DC sources. A detailed comparison analysis with existing topologies is presented to show the superiority of the proposed topology. The TACHB-LDN is verified in MATLAB/Simulink for the generation of a 17-level output voltage with two DC sources. The phase disposition level shift pulse width modulation (PD-LSPWM) technique is used to generate the required triggering pulse for the converter. The carrier frequency is considered to be the fundamental frequency to ensure low-frequency switching. Conduction and switching loss are analyzed with the help of PSIM software. The obtained simulation results are verified through a prototype model developed in the laboratory using dSPACE 1104. The total harmonic distortion (THD) of the 17-level output voltage waveform is found to be below 5% (IEEE 519 Standard). The efficiency of the prototype model under different loads is observed to be in the range of 93.65-97.35%.