Small signal stability of islanded microgrids with washout filter-based droop controller considering source dynamics and active load

This paper presents a washout filter-based droop control technique for power sharing of distributed generators (DG) in a low-voltage (LV) autonomous microgrid with active and passive loads. Also, the proposed controller aims to regulate the voltage and frequency of the microgrid accurately. A complete small signal model of the islanded microgrid is derived to select the appropriate droop control parameters and study the impact of source dynamics of solar PV. The obtained small signal model is used to perform eigenvalue, participation factor, and sensitivity analysis of the microgrid. The comprehensive small signal analysis indicates that there is a significant impact of source side dynamics and active load on the stability of the system. Furthermore, the proposed controller is integrated with virtual impedance to enhance the stability and reactive power sharing of the microgrid, and its performance is also verified with the small signal analysis. Simulation is carried out in MATLAB/Simulink environment on a microgrid with three DGs with passive and active loads at different locations. From participation factor analysis, it is found that each state corresponding to a source has around 16.5% association with low-frequency modes. Also, the steady-state frequency error is significantly reduced to 0.02% with the proposed controller. After integrating virtual impedance, the reactive power sharing error is reduced by 109.09% and 18.27% for the DG1 and DG2 with only PL of operation from 5 to 7 s. The obtained results clearly show that the proposed washout filter-based droop controller has a better performance compared to the conventional droop with respect to power sharing, frequency regulation, and dynamic behavior.