SOGI-FLL-WDCRC Filter for Seamless Control of Microgrid for Optimal Coordination of Conventional and Renewable Energy Resources

An efficient control strategy is presented in this paper to obtain seamless synchronization and improved power quality (PQ) for an AC microgrid feeding highly distorted and unpredictable loads. This paper proposes an improved second-order generalized integrator-frequency locked loop with DC-offset rejection capacity (SOGI-FLL-WDCRC) filter in an AC microgrid to mitigate the grid pollution and the PQ issues caused by the nonlinear loads. The SOGI-FLL-WDCRC filter accurately estimates the positive sequence components (PSCs), phase angle and frequency from the abnormal grid voltages. Thereby, high-quality grid currents and seamless synchronization are realized even at abnormal grid voltages. Moreover, it accurately extracts the fundamental active weight component of the nonlinear load currents, even during dynamic conditions. This results in the generation of accurate reference source currents, thus allowing efficient functioning of the voltage source converter (VSC) and delivering high-quality power to the system by mitigating the load's harmonics, reactive power and unbalanced components. The proposed control is designed in MATLAB/Simulink platform and its performance is studied. A 3.2 kW solar PV array integrated to a 220 V (line), 50 Hz three-phase utility grid/DEG set is designed and developed as a laboratory prototype to validate the simulated responses. Furthermore, the effectiveness of the proposed control is verified and compared with conventional controls using dSPACE-1202 MicroLabBox on a laboratory test bed. The results obtained from the simulation software and laboratory test bed confirm the effectiveness of the proposed control in estimating the accurate PSCs of grid voltages and oscillations free weight components with higher convergence and better stability under abnormal grid and load conditions.