Grid Integration of a Dual Two-Level Voltage-Source Inverter Considering Grid Impedance and Phase-Locked Loop

This article proposes a dual two-level voltage-source inverter (DTL VSI) and its control to effectively integrate two dc sources into the multi-infeed ac/dc (MIACDC) power architecture of fully integrated power and energy systems (FIPESs). The current-controlled method is also synthesized and proposed to control the grid-connected DTL VSI. To this end, this article provides mathematical analyses comparing the DTL VSI with the conventional current-controlled grid-connected two-level VSIs (TL VSIs). The linearized state-space models of both systems are mathematically derived for analyzing the dynamics of both structures. These models reveal the salient feature of the proposed DTL VSIs used in grid integration. To this end, space-phasor analysis is employed, and the dynamics of the phase-locked loop (PLL) and the grid impedance are also considered. The proposed grid-connected DTL VSI (with the current-controlled algorithm) not only in weak grids (for normal grid conditions) but even after fault removal (for faulty grid conditions) stabilizes the active and reactive power dynamics with improved transient performance compared with that of its conventional counterpart. Therefore, it enhances the operation range of the VSIs integrating various entities in FIPES' MIACDC power architecture. This article provides supportive simulation results and experiments generated by MATLAB and a scaled-down test rig, respectively.