This paper proposes a distributed control scheme to regulate the power flows among multiple microgrids operating in islanded mode. Each microgrid controller gathers information from neighboring microgrids and reduces dynamic interactions. Modal analysis and time-domain simulations are used to identify critical issues that degrade the stability of microgrids under different operating conditions. A case study comprising three interconnected microgrids is considered. Each microgrid includes distributed generation and is described through a detailed dynamic model. Time-domain analyses are carried out considering different scenarios and large disturbances. Simulation results indicate that, while conventional controllers can lead to poorly damped power oscillations among the interconnected microgrids, the proposed control scheme guarantees stability in the postdisturbance operating conditions.

In the coming years, plug-in hybrid electric vehicles (PHEVs) will strongly penetrate the French car fleet. Their impact on each element of the electric distribution grid needs to be estimated. In this paper, the impact of PHEVs on the life duration of the medium-voltage/low-voltage (LV) transformer using a thermal model to estimate the hot-spot temperature is studied. Based on probabilistic algorithms, three penetration rates of PHEVs are studied. A stochastic method is applied to construct domestic daily load profiles of houses constituting an LV residential electric grid supplied by the transformer. Correlated with the initial load rate (without PHEVs) of the transformer, two indices are proposed; the D_{TR_PHEV_X} and V_{TR_PHEV_X} to calculate, respectively, the life duration and aging rate of transformer in the presence of PHEVs. It is shown that the aging rate of the transformer is quadratic in the presence of PHEVs.

In this paper, a new strategy to control microgrids highly penetrated by voltage source converters (VSCs) is proposed. The strategy is based on the instantaneous measurements and calculations of voltages and currents and the application of instantaneous power theory. This approach employs each VSC along with an LC filter as a current source. The grid parameters are not known to the controller, only the filter inductance and capacitance. The approach characterizes a theoretical methodology to define a grid status parameter that provides multiple alternatives to operate the VSC autonomously. Moreover, one of those alternatives is sharing load among VSCs by regulating the voltage of the local connection bus. This grid status parameter is an external voltage contribution vector defined by the operation of the other VSCs in the microgrid. Because of the definition of this parameter, frequency manipulation is not employed as a communication link between VSCs, avoiding perturbation to the grid stability. The approach provides an approximation of the equivalent impedance of the system seen from the filter output. The load-sharing scheme under the proposed strategy is fully described. An experimental validation is performed in order to test the proposed approach for load sharing between three VSCs and the inclusion of nonlinear load.

This paper proposes an application of an evolutionary game dynamics called the escort dynamics (ED) for the decentralized load management of plug-in electric vehicles (PEV). Different from earlier contributions, in the present approach, PEVs work together in a fair scheme in order to provide several ancillary services to the grid: Load shifting, active power balancing, and partial supply of reactive power demand on each phase of the distribution transformer. Meanwhile, batteries are guaranteed to be fully charged according to the constraints imposed by the owners. In the proposed formulation, chargers can be either three phase or single phase; however, in this paper, only three-phase chargers are considered. The key concepts behind ED, especially for escort functions, are provided at the beginning of this paper. Based on these concepts, the assumptions and analogies followed for the construction of the proposed approach are explained in detail, especially for the proposed definition of escort functions. A multipopulation scenario is proposed for the interaction of several PEVs using local ED routines. This interaction among populations follows another well-known evolutionary game dynamics called the best reply dynamics. Performance is evaluated using real data measured from a distribution transformer from the SOREA utility grid company in the region of Savoie, France.