How to calculate the efficiency of cascade H-Bridge multilevel inverter using MATLAB /Simulink?

I would like to implement subsytem using Matlab Simulink for multilevel inverter like cascade H-bridge multilevel inverter , but the problem which current and voltage should be taken from input because for example if I built 5 level cascade H bridge i need two bridge cell with two dc sources this is my problem .

I already build it as shown in figure below and its work if I have only one source but with two sources it didnt work .Hope that any one help me in this issue.