Multilevel inverters are the new structures of power electronic circuits that are used in high voltage DC-AC conversion systems. These kinds of inverters create more output voltage levels in which reduce the harmonic components. In this paper, a new three source multilevel inverter is proposed that consists of eight switches in basic structure. Proposed topology is aimed in symmetrical and asymmetrical state that can produce 7 and 11 levels in symmetrical and asymmetrical case, respectively. Modularity and extendibility are two important features of the proposed structure, so that the output voltage levels can be increased significantly. The Selective Harmonic Elimination (SHE) is utilized for switching modulation that omits selected harmonics. A comparative study between proposed structure, conventional topologies and recent ones with due attention to number of components is established. The proposed structure is simulated in MATLAB/Simulink software and a prototype is implemented in laboratory to validate the operation of the converter. The simulation and experimental results verify the accurate and proper performance.