Flexible low-frequency power transmission system synchronization check switching-on grid-connected method and device

Abstract

The invention discloses a synchronization detection closing grid-connected method and equipment for a flexible low-frequency power transmission system. The method comprises the following steps: disconnecting all switches of a grid-connected converter station; switching on a power frequency network side switch and a power frequency valve side switch of the grid-connected converter station, and charging a capacitor in the converter; in response to the fact that the capacitor voltage of the converter is stable, unlocking the converter, and controlling the low-frequency side to reach the rated voltage; in response to the fact that the capacitor voltage mean value and the low-frequency side voltage of the converter reach rated values, if a low-frequency bus side voltage transformer detects no voltage, a low-frequency valve side switch and a low-frequency network side switch are directly switched on for grid connection; if the low-frequency bus side voltage transformer detects voltage, the low-frequency valve side switch is directly switched on, then the low-frequency network side switch is detected to be switched on synchronously for grid connection, or the low-frequency network side switch is directly switched on, then the low-frequency valve side switch is detected to be switched on synchronously for grid connection. According to the invention, the number of low-frequency voltage transformers is reduced, the cost and complexity of the system are reduced, and engineering application is promoted.

Description

technical field [0001] The invention relates to the field of low-frequency or frequency-divided power transmission, in particular to a method and equipment for synchronizing, closing, and connecting to the grid for a flexible low-frequency power transmission system. Background technique [0002] The traditional high-voltage transmission technology adopts the method of increasing the voltage and reducing the current to achieve the purpose of improving the transmission efficiency and increasing the transmission capacity and distance, while the innovative low-frequency or frequency division transmission technology has the above advantages by reducing the transmission frequency. Expansion and reconstruction of old lines and long-distance power transmission have huge application potential. [0003] The low-frequency power transmission system is composed of multiple converter stations connected in parallel. A single converter station converts the power-frequency alternating curren...

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Problems solved by technology

[0004] The low-frequency side of the low-frequency transmission system is equipped with a low-frequency voltage transformer, which needs to be customized separately. Compared with the traditional power-frequency voltage transformer, the cost is increased. Therefore, it is necessary to study a flexible low-frequency transmission system. Quantity, reduce the cost of transmission system, and promote engineering application

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