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This paper presents a novel full-order nonlinear observer-based excitation controller design for interconnected power systems. Exact linearization approach of feedback linearization is used to design the nonlinear observer when the power system is fully linearized. The excitation control law is derived for the exactly linearized power system model. The observed states of power system are directly used as the input to the controller where the control law does not need to be expressed in terms of all measured variables. A single machine infinite bus (SMIB) system is used as test system and all the states are observed for SMIB system. To validate the effectiveness of the proposed control scheme on a large system, a benchmark 3 machine 11 bus system is also simulated. Simulation results show the accuracy and performance of observer-based nonlinear excitation controller by comparing with the exact linearizing controller where the control law is expressed in terms of all measured variables.

This paper presents a robust nonlinear distributed controller design for islanded operation of microgrids in order to maintain active and reactive power balance. In this paper, microgrids are considered as inverter-dominated networks integrated with renewable energy sources (RESs) and battery energy storage systems (BESSs), where solar photovoltaic generators act as RESs and plug-in hybrid electric vehicles as BESSs to supply power into the grid. The proposed controller is designed by using partial feedback linearization and the robustness of this control scheme is ensured by considering structured uncertainties within the RESs and BESSs. An approach for modeling the uncertainties through the satisfaction of matching conditions is also provided in this paper. The proposed distributed control scheme requires information from local and neighboring generators to communicate with each other and the communication among RESs, BESSs, and control centers is developed by using the concept of the graph theory. Finally, the performance of the proposed robust controller is demonstrated on a test microgrid and simulation results indicate the superiority of the proposed scheme under different operating conditions as compared to a linear-quadratic-regulator-based controller.

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This paper presents a new approach to control the grid current and dc link voltage to maximum power point tracking (MPPT) and dynamic stability of a three-phase gridconnected photovoltaic (PV) system. To control the grid current and dc link voltage, zero dynamic design approach of feedback linearization is used which linearizes the system partially and enables to design controller for reduced order photovoltaic systems. This paper also describes the zero dynamic stability of three-phase grid-connected PV system which is a key requirement for the implementation of such controller. Simulation results on a large-scale grid-connected PV system show the effectiveness of the proposed control scheme in terms of delivering maximum power into the grid.

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International audienceThis 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 dy- namic 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 post- disturbance operating conditions