MMC-based high-frequency AC bus electric energy routing structure and control strategy

Abstract

The invention relates to an MMC-based high-frequency AC bus electric energy routing structure and a control strategy, and belongs to the technical field of electric energy conversion. The routing structure comprises a medium-voltage conversion stage, a high-frequency isolation stage and a low-voltage stage. The control strategy comprises medium-voltage conversion stage AC / DC conversion control, high-frequency isolation stage control and high-frequency AC bus low-voltage output end control. According to the invention, a modular multi-level converter is combined with an isolation transformer and a full-bridge structure to form a high-frequency AC bus electric energy routing structure and realize electric isolation, so that electric energy conversion links can be reduced, the capacitance volume of the modular multi-level converter is reduced, submodule voltage fluctuation suppression and automatic equalization are realized, the power density is improved, and system control is simplified.

Description

technical field [0001] The invention relates to an MMC-based high-frequency AC bus power routing structure and control strategy, and belongs to the technical field of power conversion. Background technique [0002] With the increase in the penetration rate of distributed energy generation and the increase in the proportion of DC loads such as electric vehicles and LED power supplies, the grid structure is becoming more and more diversified. The traditional transmission and distribution network and operation mode are difficult to meet the needs of coordinated and stable operation of the system. Connecting various forms of energy sources and loads and realizing the coordinated operation of "source-network-load-storage" has become a new requirement for the development of smart grids and green grids in the future. In order to make full use of distributed energy and meet the needs of various forms of load operation, the Energy Internet with energy coordination and management capa...

AI Technical Summary

Problems solved by technology

The scheme of cascading DABs of sub-modules to form a common DC bus requires a large number of switches and transformers, and the cost is high, and the common DC bus is used as the power conversion hub to realize AC-DC conversion. Many conversion links are required, which seriously affects the energy conversion efficiency of the system.

[0004] MMC-based power routing has a large number of modules in the MMC structure and large-scale capacitors are required to suppress voltage fluctuations in sub-module capacitors, which limits the increase in system power density. high complexity

At present, as a strategy to solve the voltage fluctuation of the capacitor of the sub-module of the MMC structure, some scholars have proposed a scheme of injecting common-mode voltage on the AC side and injecting circulating current into the phase unit to suppress voltage fluctuation, but there are problems such as increased bridge arm current and poor quality of DC output waveform.

And this method of suppressing voltage fluctuations usually requires closed-loop control, which increases the complexity of the control system

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