Improvement of Stability Margin of Droop-Based Islanded Microgrids by Cascading of Lead Compensators

Microgrids are systems consisting of local generators based on renewable energy sources, energy storage elements, and loads. Such systems can be operated in grid connected and/or islanded modes. The islanded mode of operation is known to offer challenges in terms of stability. The work presented in this paper demonstrates a technique to enhance the stability margin of an islanded ac microgrid. Lead compensators are cascaded in series in the real power-frequency droop control of the distributed generators. This modification results in increased stability margin of the system. The study also investigates the possible limit upto which the stability margin can be increased. The effectiveness of the proposed technique is demonstrated through eigenvalue analysis and simulations on two systems: A low voltage islanded microgrid (system-1) and the islanded IEEE 33 bus system (system-2). Experimental results on a laboratory scale microgrid confirm the findings of the proposed strategy.