Transient Stability Assessment of DC Microgrid using Nonlinear Decoupling Approach

Abstract

DC micro grid provides power locally with minimum transmission losses. However, due to presence of converters, dc micro grid suffers from the nonlinearities which led to instability of the system. It imposes challenge to integrate dc micro grid with the distribution network. Therefore, in this paper, the transient stability of the DC microgrid has been investigated considering linear load, nonlinear load, nonlinear load with DG and pole to ground fault. Due to the high-order and nonlinear nature of the dc microgrid system, the nonlinear decoupling method has been adopted for a more efficient analysis of the transient stability of dc microgrids. The nonlinear decoupling technique can resolve nonlinear difficulties, which is extremely appropriate for the transient stability assessment of dc microgrids. From the results, it is observed that in the case of nonlinear loads, the introduction of DG as an active power compensation in the system can considerably improve the overall active power in the system. Also, in case of fault, DG works as a backup and supplies power to the load. The simulation results also reflects that in some circumstances, adding and removing large loads and changes in voltage levels are not invertible. One of these changes in system dynamics could result in system instability.