A Power Electronic Transformer Based on Hybrid Modular Multilevel Converter

Abstract

The invention discloses a power electronic transformer based on a hybrid modular multilevel converter, which belongs to the technical field of power generation, transformation or distribution. A power electronic transformer includes an input stage, a transmission stage and an output stage. The transmission stage is an input parallel and output series structure of multiple DC / DC power units. The low-voltage side is connected in parallel to the low-voltage DC bus of the power electronic transformer system, and the high-voltage side is connected in series through a bypass circuit to connect to the high-voltage DC bus of the power electronic transformer system. According to the real-time power transmission of the power electronic transformer system, the number of DC / DC power units in series is changed through the bypass circuit of the transmission stage to realize the active adjustment of the high-voltage DC bus voltage. The modular multilevel converter of the output stage is a hybrid Modular structure for overshoot operation of the output stage. The invention can reduce the volume and weight of the power electronic transformer system, improve the power transmission efficiency and improve the system reliability.

Description

technical field [0001] The present invention relates to power electronic technology applied in new energy grid connection, more specifically, to a power electronic converter structure and corresponding control based on a hybrid modular multilevel converter, which belongs to power generation, power transformation or power distribution technical field. Background technique [0002] In recent decades, the world is facing the dual pressure of resource depletion and environmental pollution. Countries around the world have vigorously developed alternative energy sources such as renewable energy as a breakthrough to alleviate the energy crisis. The scale of global wind power generation has thus shown a trend of continuous expansion. [0003] At present, wind turbines are connected to the power grid after boosted by grid-connected converters and power frequency transformers. With the launch of ultra-high-power wind turbines, the voltage, capacity and manufacturing costs of grid-con...

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Problems solved by technology

[0006] The purpose of the present invention is to address the shortcomings of the above-mentioned background technology and provide a power electronic converter based on a hybrid modular multilevel converter, which reduces the power electronic transformer system by reducing the total volume of the output stage sub-module capacitor The overall volume, by flexibly controlling the input quantity of transmission-level converter units, reduces the operation loss of the transmission level and the requirement for redundant units in case of failure, effectively improves the power density of the wind turbine grid-connected power electronic transformer, and improves the wind turbine grid-connected The power transmission efficiency and operational reliability of the power electronic transformer solve the technical problems of low transmission-level work efficiency and low system power density of the existing power electronic transformer for grid-connected wind turbines

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