A h-mmc-based wind power grid-connected system and its control method

Abstract

The invention discloses a H-MMC-based wind power generation-grid-connected system and a control method thereof. The system includes a three-phase direct drive permanent magnet wind generator and an H-MMC; the H-MMC includes six bridge arms, each The bridge arms are connected end to end in sequence; each of the bridge arms includes N full-bridge sub-modules and a reactor, and the N full-bridge sub-modules are connected in series end-to-end with the reactor in turn; the three-phase direct drive permanent The three-phase winding of the magnetic wind generator and the three-phase of the power frequency AC grid are alternately connected to the six vertices of the H-MMC. This system adopts maximum power tracking control, grid side current control, H‑MMC capacitor voltage balance control, H‑MMC bridge arm current tracking control, which can realize direct grid connection at different voltage levels, saves the step-up transformer, and solves the problem of fan The problem that the capacitor voltage of the MMC sub-module fluctuates too much during startup.

Description

technical field [0001] The invention relates to the technical field of wind power generation, in particular to an H-MMC-based wind power 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 Kingdom and...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a wind power grid-connected system based on H-MMC and its control method, which not only simplifies the multi-level converter structure of the wind power system, reduces the number of sub-modules of the converter, but also improves the efficiency of the converter system. Reliability, and realize the direct grid connection of wind power generation system, cancel the booster station, and solve the problem of excessive fluctuation of capacitor voltage of sub-modules of traditional modular multi-level converters when the wind turbine is started

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