Wind power generation-grid connected system based on H-MMC and control method thereof

Abstract

The invention discloses a wind power generation-grid connected system based on an H-MMC and a control method thereof. The system includes a three-phase direct-drive permanent magnet wind generator andan H-MMC. The H-MMC comprises six bridge arms, which are sequentially connected from head to tail. Each bridge arm comprises N full-bridge sub-modules and a reactor, wherein the N full-bridge sub-modules are serially connected with the reactor head and tail in sequence. A three-phase winding of the three-phase direct-drive permanent magnet wind generator and the three-phase of a power frequency alternating current grid are alternately connected to the six vertices of the H-MMC. The maximum power is adopted for tracking control, grid-side current control, H-MMC capacitance and voltage balancecontrol and H-MMC bridge arm current tracking control, direct grid connection of different voltage grades can be realized, a step-up transformer is not needed, and the problem that the capacitance andvoltage of an MMC sub-module fluctuates too much when a fan is started is solved.

Description

technical field [0001] The invention relates to the technical field of wind power generation, in particular to an H-MMC-based wind power generation-grid-connected system and a control method thereof. Background technique [0002] Wind power is a strategic emerging industry in my country. Vigorously developing wind power is the only way to cope with climate change, realize clean substitution, promote energy conservation and emission reduction, and ensure energy security. It is an important measure for my country to seize the commanding heights of a new round of global energy transformation and economic and technological competition. In 2016, my country's new installed capacity of wind power was 23.37 million kW, ranking first in the world. Among them, the cumulative installed capacity of offshore wind power was 1.63 million kW, making it the fourth country in the world whose installed capacity of offshore wind power exceeded the million-kilowatt mark after Denmark, the United ...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a wind power generation-grid-connected system based on H-MMC and its control method, which not only simplifies the multilevel converter structure of the wind power generation system, reduces the number of sub-modules of the converter, and improves the efficiency of the converter system. The reliability of the wind power generation system can be directly connected to the grid, and the step-up station can be canceled, and the problem of excessive fluctuation of the capacitor voltage of the sub-module of the traditional modular multi-level converter can be solved when the wind turbine is started.

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