Hybrid SVM With Duty Cycle Waveform Split for Power Allocation of Single-Stage Multiport Inverter-Formed Islanded Microgrids

The single-stage multiport inverter (SSMI) is a power-efficient solution for multisource integration in islanded microgrids. However, the modulation design for the SSMI is challenging since the ac voltage forming under unbalanced dc-port voltages and the power allocation between dc sources should be achieved simultaneously. To this end, this paper proposes a hybrid space vector modulation (HSVM) scheme to achieve direct power allocation while maintaining satisfactory ac voltage forming under unbalanced dc-port voltages. In the proposed HSVM scheme, SVM is first employed to realize ac voltage forming due to its superiority in dc voltage utilization, and the heavy computational burden under unbalanced dc-port voltages is avoided via a virtual two-level model. By precisely splitting the duty cycle waveforms obtained from the virtual two-level model, the power allocation is directly realized in the carrier-based frame, which avoids the complex and indirect regulation of redundant vectors in the space-vector frame. Moreover, the power conversion efficiency is enhanced due to the discontinuous characteristics of the split-obtained duty cycle waveforms. By combining two different frames, the proposed HSVM scheme simultaneously achieves satisfactory ac voltage forming and direct power allocation with a low computational burden and high efficiency. Experimental results validate the effectiveness and superiority of the proposed scheme.