Abstract-The introduction of microgrids in distribution networks based on power electronics facilitates the use of renewable energy resources, distributed generation (DG) and storage systems while improving the quality of electric power and reducing losses thus increasing the performance and reliability of the electrical system, opens new horizons for microgrid applications integrated into electrical power systems. The hierarchical control structure consists of primary, secondary, and tertiary levels for microgrids that mimic the behavior of the mains grid is reviewed. The main objective of this paper is to give a description of state of the art for the distributed power generation systems (DPGS) based on renewable energy and explores the power converter connected in parallel to the grid which are distinguished by their contribution to the formation of the grid voltage and frequency and are accordingly classified in three classes. This analysis is extended focusing mainly on the three classes of configurations grid-forming, grid-feeding, and gridsupporting. The paper ends up with an overview and a discussion of the control structures and strategies to control distribution power generation system (DPGS) units connected to the network.

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In this paper we tackle the on-line estimation of state variables in MIMO continuous stirred chemical reactor (CSTR) using a nonlinear observer. We prove the asymptotic stability of the resulting error system. Moreover, this observer has robust performance in the presence of model uncertainty and measurement noise. Finally, computer simulations are developed for showing the performance of the proposed nonlinear observer.

In this paper, a power control study analysis of a wind energy conversion system (WECS) based on a doubly fed induction generator (DFIG) connected to the electric power grid is presented. The main objective of this work is to compare the energy production unit performances by the use of two types of controllers (namely, Polynomial RST and Sliding Mode (SM) Controllers) for the WECS control in terms of instruction tracking and robustness with respect to the wind fluctuation and the impact on the quality of the energy produced. A vector control with stator flux orientation of the DFIG is also presented to control the active and reactive powers between the stator and the network. To show the effectiveness of both control methods performances analysis of the system are analyzed and compared by simulation and results included in this paper.

Voltage fluctuations due to random load variation are amongst the most important power-quality problem in a self-excited induction generator (SEIG) and wind energy conversion system. This paper presents a comprehensive modeling analysis and control strategy of a three-phase cage induction machine used as a self-excited induction generator. The proposed load voltage control strategy is based on the action of the static synchronous Compensator (STATCOM) which can not only provide the necessary reactive power but also may enhance the load ability. Moreover, a feed forward control method for the STATCOM is introduced and applied for controlling the SEIG's terminal voltage by using an outer control loop. An inner loop was also used to control the STATCOM's output reactive power to achieve the regulation of the AC bus voltage during load variation. To achieve this objective, we have designed and introduced an RST inner loop controller. To demonstrate the effectiveness of the proposed RST controller, a comprehensive set of simulation results are presented and thoroughly discussed in comparison with those of two other classical controllers, namely, the proportional-integral controller and the integral-proportional controller.