Direct Duty Cycle Control-Based Power Allocation Strategy for Single-Stage Multiport Inverter in Islanded Microgrid

Single-stage multiport inverter offers direct power flow from the dc side to the ac side and has the advantages of compact size and low costs. However, due to its unbalanced dc-link voltages and coupled power features, it is challenging to realize desirable output current and flexible dc-port power allocation simultaneously. To address the above issues, this article proposes a direct duty cycle control-based power allocation strategy. The duty cycles can be solved based on the mathematical models of the single-stage multiport inverter via two stages. In the first stage, three duty cycles can be obtained by small hexagon selection according to the location of the reference voltage vector. In the second stage, the rest duty cycles are determined by solving the reference voltage vector synthesis and dc-port power tracking equations. Not only the output voltage/current quality is guaranteed, but also flexible dc-side power allocation can be realized under the unbalanced dc-link voltages. In addition, the proposed power allocation strategy has the advantages of simple concepts and fast dynamic response due to duty cycles being directly generated. Finally, the effectiveness of the proposed power allocation strategy is verified by islanded microgrid experimental tests.