Hybrid energy storage topological structure on basis of MMC modular multilevel converter

Abstract

The invention relates to a hybrid energy storage topological structure on the basis of an MMC (modular multilevel converter). The structure comprises a positive bridge arm and a negative bridge arm; the positive bridge arm is formed by sequentially connecting power conversion subunits 1 to n in series; one end of the positive bridge arm is connected with a high-voltage DC (Direct Current) positive bus bar and the other end of the positive bridge arm is connected to a high-voltage three-phase AC (Alternating Current) power grid by a current limiting reactor; the negative bridge arm is formed by sequentially connecting power conversion subunits n+1 to 2n in series; one end of the negative bridge arm is connected with a high-voltage DC negative bus bar and the other end of the negative bridge arm is connected to the high-voltage three-phase AC power grid by a current limiting reactor; each functional conversion subunit is formed by connecting a power conversion module, a potential isolation module and an energy storage module in series. According to the invention, various energy storage bodies are flexibly switched into a power system and an energy storage function and a service which are uninterrupted, high in quality, flexible to control and safe to operate are provided for the power system.

Description

technical field [0001] The invention relates to a hybrid energy storage topological structure based on an MMC modular multilevel converter. Background technique [0002] The storage of electric energy can bring many benefits, including improving the power quality of users, improving the reliability of power supply, smoothing the power fluctuation caused by the connection of renewable energy to the grid, and providing services for charging and replacing batteries of electric vehicles. At present, energy storage bodies mainly include lead-acid batteries, lithium batteries, supercapacitors, flow batteries, etc. The structure of energy storage devices is mainly a full-bridge or half-bridge AC-DC conversion and DC conversion structure. At present, there are mainly the following problems. The first is the problem of series-parallel connection of energy storage bodies during large-scale energy storage. Generally, the voltage of energy storage cells is low, the power is small, and t...

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Problems solved by technology

The first is the problem of series-parallel connection of energy storage bodies during large-scale energy storage. Generally, the voltage of energy storage cells is low, the power is small, and the capacity is small. and capacity meet the requirements of large-scale energy storage, but a large number of energy storage cells with a series-parallel structure will have voltage and current equalization problems during the charging and discharging process; second, grid-connected problems, large-scale energy storage systems need to Into a grid with a higher voltage level, the simple full-bridge or half-bridge power conversion structure directly connected to the grid often cannot meet the high voltage and high power quality requirements of its grid connection, and it is difficult to meet its grid-connected current through transformer grid connection limit

Third, the problem of safety potential isolation. Due to the failure to achieve potential isolation, the energy storage unit in the energy storage device cannot be loaded and unloaded when the equipment is running, and it cannot be applied to occasions that require frequent loading and unloading of the energy storage unit. Such as electric vehicle battery charging and replacement services, etc.

Fourth, the problem of energy storage differences. The energy storage bodies used in hybrid energy storage applications or new and old energy storage bodies or even different batches of energy storage bodies have differences in their charge and discharge characteristics, which requires independent Only measurement and control can ensure the reliable, safe and long-life use of the energy storage body

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