Abstract
The intermittent characteristics of microgrids (MGs) have motivated the development of energy management systems (EMSs) in order to optimize the use of distributed energy resources. In current studies, the implementation of an EMS followed by experimental-based analyses for both grid-tied and stand-alone MG operation modes is often neglected. Additionally, the design of a management strategy that is capable of preserving the storage device lifetime in battery-based MGs using a power gradient approach is hardly seen in the literature. In this context, this work presents the application of an EMS for battery-based MGs which is suitable for both grid-tied and stand-alone operation modes. The proposed EMS is formulated as an optimal power flow (OPF) problem using the $\boldsymbol {\epsilon }$ -constraint method which is responsible for computing the current references used by the EMS to control the MG sources. In the optimization problem, the total generation cost is minimized such that the active power losses are kept within pre-established boundaries, and a battery management strategy based on power gradient limitation is included. Finally, the effectiveness of the proposed EMS is evaluated by two scenarios which enable detailed analyses and validation. The first considers a dispatchable and a non-dispatchable source, whereas the second a dispatchable source and a storage device. The experimental results showed that the proposed EMS is efficient in both operation modes and is also capable of smoothing the state of charge ( SoC ) behavior of the storage device.
Highlights
The connection of distributed generators (DGs) to electrical power systems and the renewable energy sources intermittent characteristics have motivated the study of energy management strategies to optimize microgrids (MGs) operations, improving DGs performance in an intelligent, safe, reliable and coordinated way [1].The control concepts applied to MGs are established hierarchically through the primary, secondary and tertiary levels
In this work, an energy management system based on an optimal power flow (OPF) problem for MG, which allows operation in both grid-tied and stand-alone modes, was presented
The optimization problem was solved by the -constraint method and prioritized the generation cost minimization while ensuring that the active power losses remained below a pre-established value and suppressing damaging fast transients in the energy storage device
Summary
The connection of distributed generators (DGs) to electrical power systems and the renewable energy sources intermittent characteristics have motivated the study of energy management strategies to optimize microgrids (MGs) operations, improving DGs performance in an intelligent, safe, reliable and coordinated way [1]. An effective solution for saving the device lifetime, which is usually approached in the literature, is based on the battery power gradient limitation introduced in the objective function or in the optimization problem constraints [8], [17]. In a way to reduce the weighted sum method implementation difficulties, which are related to the weights definition and the objectives normalization values, the EMS optimization algorithm is based on the solution of an OPF problem performed according to the -constraint method. This algorithm minimizes the MG total generating cost and keeps the active power losses below a pre-established value. Experimental tests were carried out to evaluate the proposed EMS in terms of MG energy management and effectiveness in reducing battery degradation by avoiding high battery power and SoC gradients
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