Opposite Vector Modulation-Based Bidirectional Power Allocation for Single-Stage Multiport Inverter-Connected Hybrid Energy Storage System

The single-stage multiport inverter (SSMI) directly connects the hybrid energy storage system (HESS) to the ac side, which presents the merits of low cost and high efficiency due to the removal of dc–dc converter. The existing space vector modulation (SVM) schemes transplanted from the corresponding multilevel inverters cannot achieve bidirectional active power flow for both dc ports due to the limited degree of freedom. To this end, this article proposes an opposite vector modulation to release an extra degree of freedom for bidirectional active power allocation in the SSMI. A novel two-level inverter model of the SSMI is proposed to obtain the capability of generating opposite vectors, where the straight-forward relationship between dc-port power and opposite vector can be revealed. Then, vector phasor diagram-based theoretical analysis is proposed to demonstrate that the power allocation range is expanded by decomposing the reference voltage vector into opposite vectors. Finally, the experimental tests are conducted to verify the effectiveness of the proposed opposite vector modulation. Compared to conventional SVM strategies, not only bidirectional power allocation of both dc ports can be realized, but also the power allocation range has been increased by 21<inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula>.