Variable-frequency flexible tuning device, half-wavelength alternating-current power transmission system and control method thereof

Abstract

The invention provides a variable-frequency flexible tuning device, a half-wavelength alternating-current power transmission system and a control method thereof. The variable-frequency flexible tuning device comprises a first MMC module and second MMC module, wherein each MMC module comprises three parallel phase units. Each phase unit comprises two serially connected bridge arms, and each bridge arm comprises an electric reactor and a power module unit which are connected in series. The power module unit comprises multiple serially connected power sub-modules, wherein each power sub-module is a half-bridge structure power sub-module or a full-bridge structure power sub-module including a full-controllable power electronic device. Compared with the prior art, by adopting the variable-frequency flexible tuning device, the half-wavelength alternating-current power transmission system and the control method, output signal frequency, voltage amplitude, phase and other electric quantity parameters of the variable-frequency flexible tuning device can be flexibly adjusted, flexible tuning and flexible grid connection of the half-wavelength alternating-current power transmission system are achieved, system parameters of the device are adjusted, overvoltage and secondary arc current of a half-wavelength alternating-current power transmission line are inhibited, and fault isolation is achieved.

Description

technical field [0001] The invention relates to the technical field of half-wavelength AC power transmission, in particular to a frequency conversion flexible tuning device, a half-wavelength AC power transmission system and a control method thereof. Background technique [0002] The development of technologies such as photovoltaics and wind power has promoted intensive large-scale development in areas where resource conditions are not the best, thus making the transmission and implementation of ultra-long-distance, high-power electric energy have extensive significance and practical value. [0003] Half Wavelength AC Transmission (HWACT) refers to the ultra-long-distance three-phase AC transmission whose electrical distance of power transmission is close to one power frequency half wavelength, that is, 3000km (50Hz) or 2600km (60Hz). A half-wavelength AC line without loss is like an ideal transformer with a transformation ratio of -1.0. The voltage at the head end and the e...

AI Technical Summary

Problems solved by technology

[0006] (1) The passive tuning circuit has relatively poor adaptability to system structure, operation mode or parameter changes, and it is easy to lose half-wavelength characteristics;

[0007] (2) The function of the passive tuning circuit is relatively single, which only solves the tuning problem, and cannot meet the development requirements of flexible and intelligent power grids;

[0008] (3) When a short-circuit fault occurs in a passive tuning circuit or a half-wavelength AC transmission line, it is easy to cause resonance and generate a high-amplitude overvoltage, which requires the line and equipment to increase the corresponding insulation requirements, or requires the installation of a corresponding overvoltage limiter measures to suppress the overvoltage of the line

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