Improving the stability and damping of low-frequency oscillations in grid-connected microgrids with synchronous generators

The escalating demand for energy and the mounting environmental impacts of fossil fuel usage necessitate a paradigm shift toward the integration of renewable energy sources (RES) as the core of the electrical energy sector. Solar photovoltaic (SPV) and wind-based generation have emerged as the most promising and viable solutions, leading to a significant increase in the RES-based microgrid penetration into the power grid. However, the grid-connected microgrid operation presents challenges to the stability of the main grid. Due to small aggregated physical inertia of these microgrid, there is a significant deviation in system inertia that contributes to low frequency oscillations (LFO). These oscillations have a significant risk to power system stability. In the proposed work, a grid-connected microgrid that incorporates a synchronous generator along with SPV and wind integration is investigated. A synchronized governor combined with a power system stabilizer features a cascade structure, encompassing tilt integral derivative and fractional-order proportional integral derivative with a filter to effectively mitigate the oscillations. Furthermore, this cascaded controller is optimized using the improved reptile search algorithm. The controller efficacy is validated in the MATLAB platform by subjecting it to random variations in reference torque. Comparative analysis against conventional controllers, including Proportional Integral, Lead-Lag and Fractional Lead-Lag, demonstrates superior damping efficiency of the proposed controller since it damps LFO within the time period of 15 s.