General Algebraic Modulation Scheme for Single-Stage Multiport Inverters

The single-stage multi-port inverter (SSMPI) provides a cost-effective solution for multi-source systems thanks to its compact design that eliminates the need for additional dc/dc converters. However, the modulation scheme for SSMPI is challenging to design, because the degrees of freedom (DoFs) provided by conventional carrier-based or space-vector frameworks are insufficient for synthesizing ac voltage and distributing power among all dc ports simultaneously, especially when the number of ports is large. To bridge this research gap, this paper proposes a general algebraic modulation scheme that provides sufficient DoFs for simultaneously achieving ac voltage synthesis and power distribution, regardless of the number of ports. In the proposed scheme, the modulation design is formulated as a straightforward solution process for algebraic equations from a switching-duty-cycle perspective, allowing the available DoFs to expand autonomously as the variable space increases. Based on this concept, the modulation implementation is further carried out using a two-step method, where the duty cycle differences are first solved to guarantee power distribution performance, and the volt-second balance constraint is then calculated for ac voltage synthesis, providing the advantages of easy implementation and low computational burden. Finally, the effectiveness and advantages of the proposed scheme are verified through simulation and experimental results.