Aiming at the general micro-grid with large harmonic component and undesirability of output voltage waveform and so on, a kind of micro-grid structure which connects the solar, wind and other micro-source inverter output is studied. The system output voltage characteristics and series micro-grid power balance control based on the method of carrier amplitude variation and phase shift modulation are mainly studied. First, a brief description of the structure of the system is made, then followed by analysis of the carrier amplitude variation and phase shift modulation, Fourier expression of system output voltage is derived, based on this, the system voltage characteristics are analyzed. Finally, Matlab/Simulink simulation analysis based on the series micro-grid with three micro-sources is made. Simulation results verify the effectiveness of the control method.