Advanced Adaptive Virtual Impedance Based Dual Mode Inverter Controller for Power and Voltage Coordination in LV AC Microgrid

The LV AC microgrid, having DERs with BESS and Solar PV, generally suffers from power fluctuation. Moreover, the nonlinear and unbalanced loads cause undesirable negative sequence and harmonic currents, which disturb the power-sharing and voltage quality. These perturbations are adverse for both systems, i.e., grid-connected and islanded AC microgrids. Hence, the proposed inverter control scheme introduces a dual-mode, solo control system to reconfigure itself into voltage control or current control mode suitable for islanded or grid-connected operations. An adaptive virtual impedance-based advanced angle droop control is introduced to voltage-controlled inverters that consider the coupling between active and reactive power and source side power perturbation. Such a controller minimizes power-sharing error with quick power settling among DERs under various power dynamic conditions. However, an adaptive voltage compensator for current control inverters is introduced to minimize the voltage imbalance and harmonics within the permissible range. The proposed decentralized scheme brings adaptivity with unconstrained optimization-based selection criteria for virtual impedance and voltage function coefficients. In addition, it follows the eigenvalue concept for stability analysis of the inverter control system and selection of droop coefficients. The simulation is tested on a CIGRE LV testbed and experimentally validated on a single bus system.