PR (proportional resonant) controller-based NMC-HVDC (modular multilevel converter-high voltage direct current) circulating current suppression method

Abstract

The invention discloses a PR (proportional resonant) controller-based NMC-HVDC (modular multilevel converter-high voltage direct current) circulating current suppression method. PR controller-based circulating current suppression is adopted at the inverter end to suppress positive-sequence and negative-sequence circulating currents, and meanwhile, a zero-sequence circulating current controller is used to suppress DC voltage fluctuation and zero-sequence circulating current; PR controller circulating current suppression is adopted at the rectifier end; or PR controller circulating current suppression is used at the rectifier end to suppress positive-sequence and negative-sequence circulating current, meanwhile, the zero-sequence circulating current controller is used to suppress the DC voltage fluctuation and zero-sequence circulating current, and PR controller circulating current suppression is adopted at the inverter end; or both the rectifier end and the inverter end use PR controller circulating current suppression to suppress positive-sequence and negative-sequence components and both use the zero-sequence circulating current controller to suppress the DC voltage fluctuation and zero-sequence circulating current. In each AC side system failure, the positive-sequence, negative-sequence and zero-sequence components of the circulating current can all be completely suppressed; the DC voltage fluctuation can also be suppressed; fault ride-through ability of an AC system during a fault can be improved; the problems occurring in the use of the traditional PR control method in NMC-HVDC are solved.

Description

technical field [0001] The invention relates to the technical field of flexible DC power transmission in power systems, in particular to a PR controller-based MMC-HVDC circulation suppression method. Background technique [0002] Modular multilevel converter (MMC) is a multilevel converter topology that has attracted much attention in recent years. It uses multiple submodules (submodules, SM) cascaded, and by controlling the input and disconnection states of each submodule separately, it can make the AC voltage waveform output by the converter contain many voltage steps to approach the sine wave to the maximum extent. Thereby reducing the harmonic content in the output voltage and reducing the waveform distortion to meet the harmonic requirements of the power grid. Compared with the VSC topology of the traditional two-level and three-level structure, the MMC topology has a modular structure, low output voltage and current harmonics, low switching loss, low switching stress ...

AI Technical Summary

Problems solved by technology

[0006] The present invention provides a MMC-HVDC circulation suppression method based on a PR controller. In order to solve the problem of DC voltage fluctuations caused when the PR controller circulation suppression method is directly applied to MMC-HVDC, an accurate model of the PR control method is first proposed, Then a zero-sequence circulating current controller based on the PR controller is proposed. Based on this controller, three circulating current suppression methods suitable for MMC-HVDC systems are proposed. The improved circulating current suppression method does not increase the number of controllers. In the case of low cost and low cost, the DC voltage fluctuation is completely eliminated, and the fault ride-through capability of the MMC-HVDC system is improved

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