<p>The secondary control is applied in islanded Microgrids (MGs), after the primary control, in order to restore the buses voltage and frequency to specified values. The existing power flow methods can accurately calculate the power flow for droop-controlled islanded MGs, but in many cases, they cannot calculate the steady-state solution of the MG after the action of secondary controllers. The main challenge in the steady-state modelling of the secondary layer lies in that the secondary controllers consist of integral parts, which can integrate functions with different integral histories, and therefore, under certain circumstances, can imply inaccurate power sharing between the distributed generation units (DGs). This phenomenon is most pronounced under communication failures, as will be shown in the simulations. In this way, this paper proposes a power flow method for calculating, accurately, the steady-state solution of hierarchically controlled islanded AC MGs, including droop-based primary control and secondary control. The paper includes four main features: a) generalized implementation in several communication strategies e.g., centralized, decentralized, consensus, distributed averaging, b) precise simulation of communication links and integral parts of secondary controllers, c) low computation time, and d) accurate 4-wire network representation. Simulations were executed to validate the proposed method against Simulink and to highlight the importance of an accurate modelling of secondary control in the power flow method for islanded MGs</p>

<p>This paper proposes a comprehensive optimization approach based on linear programming (LP) for the installation of multiple hybrid power plants (HPPs) in non-interconnected islands. Contrary to the current state-of-the-art solutions, the proposed approach optimizes simultaneously the size, location, and technology of each HPP in order to minimize the long-term electricity cost of the island. The optimization problem is formulated as a LP problem to ensure convergence and global optimum solution. Moreover, a series of system constraints are included in the optimization problem, e.g., power reserves, transmission constraints, etc., to ensure the secure and reliable operation of the grid; this is compatible with the actual preventive measures imposed by the network operator in real non-interconnected islands. Simulations are executed in a real Greek Island (Rhodes), confirming the applicability of the proposed method as an optimization tool for network planning studies in non-interconnected islands.</p>

<p>This paper proposes a comprehensive optimization approach based on linear programming (LP) for the installation of multiple hybrid power plants (HPPs) in non-interconnected islands. Contrary to the current state-of-the-art solutions, the proposed approach optimizes simultaneously the size, location, and technology of each HPP in order to minimize the long-term electricity cost of the island. The optimization problem is formulated as a LP problem to ensure convergence and global optimum solution. Moreover, a series of system constraints are included in the optimization problem, e.g., power reserves, transmission constraints, etc., to ensure the secure and reliable operation of the grid; this is compatible with the actual preventive measures imposed by the network operator in real non-interconnected islands. Simulations are executed in a real Greek Island (Rhodes), confirming the applicability of the proposed method as an optimization tool for network planning studies in non-interconnected islands.</p>

<p>The secondary control is applied in islanded Microgrids (MGs), after the primary control, in order to restore the buses voltage and frequency to specified values. The existing power flow methods can accurately calculate the power flow for droop-controlled islanded MGs, but in many cases, they cannot calculate the steady-state solution of the MG after the action of secondary controllers. The main challenge in the steady-state modelling of the secondary layer lies in that the secondary controllers consist of integral parts, which can integrate functions with different integral histories, and therefore, under certain circumstances, can imply inaccurate power sharing between the distributed generation units (DGs). This phenomenon is most pronounced under communication failures, as will be shown in the simulations. In this way, this paper proposes a power flow method for calculating, accurately, the steady-state solution of hierarchically controlled islanded AC MGs, including droop-based primary control and secondary control. The paper includes four main features: a) generalized implementation in several communication strategies e.g., centralized, decentralized, consensus, distributed averaging, b) precise simulation of communication links and integral parts of secondary controllers, c) low computation time, and d) accurate 4-wire network representation. Simulations were executed to validate the proposed method against Simulink and to highlight the importance of an accurate modelling of secondary control in the power flow method for islanded MGs</p>

<p>The secondary control is applied in islanded Microgrids (MGs), after the primary control, in order to restore the buses voltage and frequency to specified values. The existing power flow methods can accurately calculate the power flow for droop-controlled islanded MGs, but in many cases, they cannot calculate the steady-state solution of the MG after the action of secondary controllers. The main challenge in the steady-state modelling of the secondary layer lies in that the secondary controllers consist of integral parts, which can integrate functions with different integral histories, and therefore, under certain circumstances, can imply inaccurate power sharing between the distributed generation units (DGs). This phenomenon is most pronounced under communication failures, as will be shown in the simulations. In this way, this paper proposes a power flow method for calculating, accurately, the steady-state solution of hierarchically controlled islanded AC MGs, including droop-based primary control and secondary control. The paper includes four main features: a) generalized implementation in several communication strategies e.g., centralized, decentralized, consensus, distributed averaging, b) precise simulation of communication links and integral parts of secondary controllers, c) low computation time, and d) accurate 4-wire network representation. Simulations were executed to validate the proposed method against Simulink and to highlight the importance of an accurate modelling of secondary control in the power flow method for islanded MGs</p>