The integration of photovoltaic (PV) systems and renewable energy sources into modern utility grids presents substantial opportunities for sustainable energy, yet also introduces critical power quality challenges due to the proliferation of nonlinear and unbalanced loads. This paper proposes a dynamic multi-function reference frame control (DMRFC) strategy for a multifunctional bidirectional grid-interactive converter (µG-MPGIC), designed for PV-grid interconnection with enhanced power quality assistance. Built upon the Synchronous Reference Frame (SRF) theory, the DMRFC approach enables autonomous multifunctionality: (i) dynamic regulation of active power transfer based on load demands and available DC-side energy, (ii) bidirectional energy flow between AC and DC interfaces considering the battery's state of charge (SOC), (iii) harmonic current mitigation, reactive power compensation, and (iv) neutral current suppression under unbalanced load conditions. A small-signal transfer function model is developed for stability analysis using frequency-domain methods. Simulation studies conducted in MATLAB/SIMULINK demonstrate that the proposed DMRFC control achieves a total harmonic distortion (THD) reduction in grid currents to 1.25% , compared to 1.79% with conventional symmetrical component theory (SCT)-based control and 2.80% with Instantaneous Power Theory (IPT)-based control under identical conditions. Furthermore, the system achieves unity power factor operation under highly nonlinear loading, superior to the 0.96 and 0.93 power factors achieved with SCT and IPT, respectively. Under dynamic loading and fluctuating irradiation, the converter maintains a near-constant DC-link voltage, demonstrating robust grid synchronization and operational stability. The system also effectively supports bidirectional power flow, handling battery charging at −4.96 kW and discharging at +4.95 kW with seamless transitions, validated through grid current magnitude variations between 32 A and 42 A. The proposed DMRFC strategy offers a significant enhancement over conventional methods, delivering superior power quality improvement, intelligent energy management, and adaptive multifunctional operation in grid-connected PV systems.
Kumar et al. (Tue,) studied this question.