Investigation of the Dynamic Stability of Microgrid

Microgrid is an aggregation of distributed generators (DGs) and energy storage systems (ESS) through corresponding power interface, such as synchronous generators, asynchronous generators and power electronic devices. Without the support from the public grid, the control and management of an autonomous microgrid is more complex due to its poor equivalent system inertia. To investigate microgrid dynamic stability, a small-signal model of a typical microgrid containing asynchronous generator based wind turbine, synchronous diesel generator, power electronic based energy storage and power network is proposed in this paper. The small-signal model of each of the subsystem is established respectively and then the global model is set up in a global reference axil frame. Eigenvalues distributions of the microgrid system under certain steady operating status are identified to indicate the damping of the oscillatory terms and its effect on system stability margin. Eigenvalues loci analysis is also presented which helps identifying the relationship among the dynamic stability, system configuration and operation status, such as the variation of intermittent generations and ESS with different control strategies. The results obtained from the model and eigenvalues analysis are verified through simulations and experiments on a study microgrid system.