Commutation Failure Suppression Method for Current Mode HVDC Transmission System Based on Series Voltage Injection

Abstract

The invention discloses a series voltage injection-based current-type high voltage direct current transmission (LCC-HVDC) system commutation failure suppression method. The core of the method is thatthree-phase voltage series injection is carried out between the inverter of the LCC-HVDC and a receiving-end AC system to compensate dynamic fall of the voltage of the receiving-end AC system, seriesvoltage injection is realized through a unified power flow controller, a parallel transformer of the unified power flow controller is parallelly connected at the AC system side, and a series transformer is serially connected at the inverter side of the LCC-HVDC. A dynamic voltage series injection control algorithm is designed for the series converter of the unified power flow controller, so as toenable the three-phase voltage generated by the series converter of the unified power flow controller to dynamically compensate the dynamic fall of the voltage at the AC system side through the seriestransformer. Voltage distortion and voltage fall at the LCC-HVDC inverter side can be further reduced, and finally, the LCC-HVDC inverter commutation failure possibility is reduced.

Description

technical field [0001] The invention relates to the technical field of high-voltage direct current transmission, in particular to a method for suppressing commutation failure of a current-type high-voltage direct current transmission system (LCC-HVDC) based on series voltage injection. Background technique [0002] At present, most of the HVDC transmission systems operating in China are LCC-HVDC. Since the converter station of LCC-HVDC adopts the thyristor technology, the commutation of the thyristor depends on the three-phase AC voltage provided by the AC side. Generally, the increase of DC current and the drop of AC side voltage may cause the commutation failure of the LCC-HVDC inverter. The probability of commutation failure on the rectification side of LCC-HVDC is very low under normal conditions. Therefore, the research on the commutation failure of LCC-HVDC inverters has a very long history, however, so far there is still no effective method that can reliably suppres...

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Problems solved by technology

[0006] The purpose of the present invention is to solve the above-mentioned problem of commutation failure of LCC-HVDC, and provide a method for suppressing commutation failure of current-mode HVDC transmission system based on series voltage injection, considering that the main cause of commutation failure is the AC system at the receiving end In case of voltage drops, a unified power flow controller is installed between the inverter and the receiving-end AC system to inject three-phase voltage in series on the receiving-end AC system side, so that the three-phase voltage obtained by the inverter side is an ideal sine wave

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