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In recent years, the proliferation of grid-connected microgrid systems has witnessed a remarkable surge, driven by the need to enhance the availability and reliability of renewable energy sources during peak demand periods. By reducing reliance on fossil fuels, these systems offer promising avenues for sustainable energy integration. To ensure seamless synchronization of renewable energy sources with the grid, Phase-Locked Loop (PLL) controllers have emerged as a key solution. However, the information available about these PLLs is limited. In this paper, the analysis, design, and comparison of PLLs, along with the exploration of a recently developed PLL synchronization method. Specifically, we evaluate the performance of prominent PLL techniques, including PSRF-PLL, SOGI-PLL, DSOGI-PLL, E-PLL, and IPT-PLL, under diverse test scenarios such as voltage sag, swell, unbalance, and harmonics. To assess their effectiveness, hardware-in-loop virtual and real-time test-beds are employed, enabling rigorous examination of the PLL techniques for grid synchronization. The reported results demonstrate the phase tracking capability when operating in grid-connected mode. Finally, conclusions are drawn from studies conducted in the electrical grid network's healthy and unhealthy environments. • The design and analysis of PLL synchronization methods are provided. • Performances of PSRF-PLL, SOGI-PLL, DSOGI-PLL, E-PLL, and IPT-PLL are examined. • The PSRF-PLL, SOGI-PLL, DSOGI-PLL, E-PLL, and IPT-PLL designs are briefly explained. • The directions of PLL preference in a healthy and unhealthy grid environment are listed. • The synchronization efficiency and distortion management capacity of PLLs are listed. [ABSTRACT FROM AUTHOR]

• Output line impedance of parallel-connected distributed generation sources. • Voltage and frequency restoration. • Improved come robust droop control method. • State-space small-signal modeling and investigation of a microgrid. • Power-sharing accuracy. • Microgrid hardware in loop test-bed. The control and protection are critically essential to facilitate the stable operation of an island microgrid. To accomplish the exact power sharing in an islanded AC microgrid, the frequency and the voltage restoration need to be sustained. In this regard, a robust control strategy pooling an improved droop with a virtual impedance control based droop control for power sharing with f/V restoration is proposed in this article. The proposed droop controller state-space small signal modeling and an investigation for the total microgrid system are presented in this article. Meanwhile, the robustness of the strategy is escalated for a step change in the system power loads. The overall controller performance has been tested in the hardware-in-loop (HIL) test-bed. [ABSTRACT FROM AUTHOR]