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The fluctuation and intermittence of renewable energies are raising concerns about the economical scheduling and the security operation of power system. The shift from traditional fossil energies to renewable energies causes the shortage in rotational inertia and affects the frequency stability of power system. One of the promising solutions is to construct a certain number of energy storage facilities with virtual inertia in suitable places for improving stability, which simulates the characteristics of traditional generators through specific controls over the converters of energy storages. While transient issues about the optimal allocation of energy storages have not been well addressed. From the perspective of system inertia support, the system state-space model is firstly established in this paper. Then the guidance of allocating energy storages optimally is provided via ℋ 2 -norm calculation and projected gradient derivation. Moreover, for the purpose of evaluating system disturbances more precisely, an appropriate method for equivalenting the disturbance strength of nodes is proposed, the advantages of which are later examined in comparative simulations. The contribution of this paper is verified through the time-domain simulations of the New England 39-bus system together with the illustration and comparative analysis of the optimal results. • Construct the guidance of allocating energy storages optimally for inertia support. • Propose a method for equivalenting node disturbance and its transmission mechanism. • The proposed method can improve both transient performance and allocation costs. [ABSTRACT FROM AUTHOR]

Highlights • A work package of energy storage system for grid frequency regulation is proposed. • The package includes grid network modeling, ESS sizing, and control algorithms. • The proposal shows ESS is able to maintain frequency under photovoltaic systems. • The required cyclical operation of ESS for frequency regulation remains a concern. • The modularity design of the test system allows various permutations to be tested. Abstract Grid frequency deviation occurs due to the power mismatch and is corrected by a series of control actions carried out by the generators. At present, the correction of the frequency deviation is limited by the ramp rates of generators, which depend on the inertia of their rotating masses. Under the increasing penetration of intermittent renewable energy sources, the task of frequency regulation becomes more demanding in terms of response times due to the frequent power mismatches and reduction of system inertia. An energy storage system (ESS) can be an effective means of regulating the frequency due to its general fast response characteristics. A comprehensive work package is developed in MATLAB/Simulink and Matpower to study how ESS can handle the rapid changes of frequency continuously within a specified window of its state of charge (SOC). This paper includes an IEEE 24-Bus grid network modeling, the sizing of ESS and also proposes ESS controllers with offset control algorithms as the sustainable solution for frequency regulation. As such, the modularity design of the test system allows various types of ESS or loads to be tested. The locations for ESS to be placed on the network are also identified for the best frequency regulation response without causing any grid voltage violations. Meanwhile, the scenarios of high penetration of photovoltaic systems and undersized ESS are also investigated. The results indicate that ESS is able to maintain the grid frequency under the intermittency of photovoltaic systems continuously. [ABSTRACT FROM AUTHOR]

• An establishment method for iLES-MDP knowledge base is proposed. • A dynamic updating approach is introduced to expand reference solutions in knowledge base. • A multi-objective optimization framework is designed to find feasible trade-off dispatch schemes. • Feasible Pareto solutions can be obtained efficiently for iLES-MDPs. Integrated local energy system (iLES) can take full advantage of local energy resources and diversify energy supplies. However, the complexity and flexibility of multiple-input multiple-output system structure makes it difficult for iLES to guarantee energy supply quality, which needs be solved by making reliable dispatching schemes. In this paper, the optimization model of typical iLES multi-objective dispatch problem (MDP) is built and the common problems are analyzed. Aiming at adapting to the changes of the iLES-MDPs model during the practical operation process, a dynamic knowledge base-based multi-objective optimization method is proposed, by which a knowledge base is established for iLES-MDPs taking account of the characteristic of system before optimization process. Besides, considering the frequent variations of system parameters, iLES structure, energy input and load demands, an updating approach is introduced to dynamically adjust the knowledge base. Thereafter, a multi-objective optimization framework is designed to find the feasible Pareto solutions for the iLES-MDPs, by utilizing the reference solutions in knowledge base during the evolutionary procedure. Finally, the proposed method is applied to a series of iLES-MDPs, which involve renewable energy sources, combined cooling heating and power system, energy storage devices and different operation modes. The simulation results verify that the method can well adapt to the challenges of all types of iLES-MDPs. Moreover, it can obtain feasible Pareto solutions efficiently as well as reduce the performance requirement of optimization algorithms. [ABSTRACT FROM AUTHOR]