Restoration of frequency response in inverter-based micro-grids using a novel controlstrategy

In this paper, a novel frequency droop control scheme for a islanded VSI-based micro-grid with no physical communication link is developed. For the purpose of sharing active and reactive power in VSI-based micro-grids, droop method is employed instead of communication links. In this scheme, when the demand or generation changes, the output voltage of DG units and the frequency of the system will also change. This study presents an adaptive frequency droop (AFD) for improving the system dynamic and decentralized controlling power sharing in multi-bus micro-grids, in addition to preserve the network stability. Note that the controller coefficients are optimized to improve the small signal stability and obtain good operating point. In order, an optimization problem is formulated and solved using the modified shuffled frog-leaping optimization algorithm (SFLA). For comparison purposes, the proposed AFD method was applied to a case study, 5-bus micro-grid. The stability margin analysis and time response simulations prove this algorithm to be have better performance.