![]() Several works that deal with these issues will be investigated. Some issues, such as control strategies and converter design, will be approached for the analysis of the inherent complexities of each topology. Therefore, it aims to synthesize the main works in the literature, and reveal the advantages and disadvantages in terms of power losses, number of semiconductor devices, output current harmonic distortions, relevant number of control loops and the required sensors. In view of the above, this paper proposes to perform a review of the main topologies of power converters involved in BESS and present a comprehensive insight into converter technologies for this application. The same idea applies to the dc/dc stage, which can be isolated with high frequency transformers. However, a comprehensive analysis of cost-benefit, efficiency and system complexity is necessary to verify the advantages of these trends. Therefore, trends of transformerless dc/ac converter technologies are being applied in BESS, such as two levels with serial switches and modular multilevel converter (MMC). A disadvantage of these topologies is the high current on the transformer low voltage side, which can decrease their efficiency. If low voltage switches are employed in the dc/ac stage for two or three level topologies, a step-up transformer is required to connected the BESS to the MV grid. The converter topologies in each stage are classified in topologies with transformer or transformerless. This system is composed of the battery pack, dc/dc stage and dc/ac stage. In this sense, the general structure of a BESS connected to the MV grid is shown in Fig. It is worth mentioning that the dc/dc converter must be bidirectional to ensure the power flow of charge and discharge of the batteries. The dc/dc converters also allow using less batteries in series, since the converters can boost the voltages to the grid connection. Under such conditions, it is possible to increase the degree of freedom to control the battery state of charge (SOC). Furthermore, a controllable dc-link voltage can be achieved by inserting a dc/dc stage, between the battery bank and the dc-link. In several applications, this voltage is usually 600 V, which is converted into ac for the grid connection through an inverter. Therefore, it is common to connect several cells in series to form a bank of batteries that is capable of delivering a minimum recommended voltage on the dc-link. The connection of these systems in MV grids can contribute with various services, such as peak shaving, time shifting and spinning reserve. For example, the rated voltage of a lithium battery cell ranges between 3 and 4 V/cell, while the BESS are typically connected to the medium voltage (MV) grid, for example 11 kV or 13.8 kV. The nominal voltage of the electrochemical cells is much lower than the connection voltage of the energy storage applications used in the electrical system. Despite their benefits, the implementation of such systems faces considerable challenges. Therefore, the installation of BESS has increased throughout the world in recent years. However, in this scenario of high level of renewable energy, BESS plays a key role in the efforts to combine a sustainable energy source with a reliable dispatched load and mitigates the impacts of the intermittent sources. Today, solar and wind electricity generation, among other alternatives, account for a significant part of the electric power generation matrix all around the world. ![]() There has been a revolution inelectricity generation. ![]() Finally, a case study is performed to compare and analyze the converter topologies for BESS, considering some aspects such as efficiency, power quality and number of components.īattery energy storage system (BESS) have been used for some decades in isolated areas, especially in order to supply energy or meet some service demand. In addition, the different services that BESS can carry out when connected to the distribution system are analyzed in order to demonstrate all the main contributions to the electrical systems. The topologies used for each conversion stage are presented and their combinations are analyzed. This work aims to carry out a literature review on the main converter topologies used in BESS and highlight the main advantages and disadvantages of each one. There is no defined and standardized solution, especially for medium voltage applications. Several power converter topologies can be employed to connect BESS to the grid. In the scenario of high penetration level of renewable energy in the distributed generation, BESS plays a key role in the effort to combine a sustainable power supply with a reliable dispatched load. Recent works have highlighted the growth of battery energy storage system (BESS) in the electrical system.
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