Multi-source inverter (MSI) provides a low-cost and high-power-density solution for microgrids (MGs) applications due to the removal of the dc/dc converter, which offers direct power flow between dc-side and ac-side. The existing modulation strategies for MSI transplanted from those of multilevel inverters experience a limited power distribution range due to the finite control freedom of degree provided by redundant vectors. Moreover, the power distribution between the dc ports is highly coupled with the vector synthesis, this is especially true when the voltages of the dc-port are unbalanced. To address the above issue, this article proposes a decoupled modeling method and a wide-range power distribution strategy for the MSI. The decoupled model is proposed to simplify the modulation implementation process and power distribution analysis. In the proposed model, the reference voltage vector of MSI is proportionally decomposed into two decoupled parts which can be generated independently. As a result, it can not only avoid complex modulation calculations but also ensure decoupled power distribution. Moreover, detailed theoretical analysis indicates that the proposed solution can offer an expanded power distribution range by increasing the switching actions in one switching cycle. Finally, the effectiveness of the proposed multiple-carrier modulation strategy is verified by islanded MGs experimental tests.