A cascaded converter valve, direct current transmission system and control method thereof

Abstract

The invention discloses a cascade converter valve, a direct current transmission system and a control method thereof. The cascade converter valve is a high-pressure valve group and a low-pressure valve group connected in series on the direct-current side, the high-pressure valve group is the first converter, and the low-pressure valve group is the first converter. The group includes two parallel-connected second and third converters, at least one of which is a hybrid multi-level output converter, and the AC side of the first converter is connected to the third The AC side of the converter is connected in parallel through a transformer to form the first AC end of the cascade converter valve, and the AC side of the second converter forms the second AC end of the cascade converter valve. The cascade converter valve has multiple working modes and AC system access methods, and can realize high voltage, large capacity, long-distance DC power transmission and receiving-end AC network at the same time under the premise of reducing the overall manufacturing cost and floor space of the DC system Layered access and asynchronous partition interconnection, thereby improving system stability and reliability. The invention is applicable to the power system with multiple direct current feed-in points.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and more specifically relates to a cascaded converter valve, a direct current transmission system and a control method thereof. Background technique [0002] Since the 21st century, with the increasingly prominent environmental problems, in order to reduce carbon emissions and reduce the proportion of coal-fired power generation, it is necessary to develop and utilize renewable energy on a large scale. my country's new energy bases are characterized by dispersal, remote distribution, and strong volatility, and are distributed inversely with the load center, leading to an increasing demand for large-capacity long-distance transmission of electric energy. The grid-connected high-voltage AC transmission system has inherent defects such as high cost and serious stability problems. The conventional high-voltage DC transmission technology based on grid commutation ...

AI Technical Summary

Problems solved by technology

[0008] Aiming at the above defects or improvement needs of the prior art, the present invention provides a cascaded converter valve, a DC system and a control method thereof, which solve the problem of existing AC-DC transmission while realizing high-voltage and large-capacity long-distance DC transmission. Due to the lack of asynchronous partitioning of the AC system in the system, when the AC-DC fault occurs under the multiple DC feed-in of the receiving-end power grid, the AC-DC transmission system is unstable or the technical problem of decoupling occurs

Images