Method for handling failure of alternating current side of invertor side of mixed-type direct current transmission system

Abstract

This invention discloses a method for handling failure of alternating current side of invertor side of mixed-type direct current transmission system. The method is characterized by comprising the following steps: steps1, detect whether a serious failure is happened in an alternating current network of the invertor side; if so, enter the step 2; the serious failure means that the failure happened in the network of the invertor side makes the positive sequence voltage of the connection part of an inversion converter station and the alternating current network less than 0.6 time of a rated voltage; step2, shift the phase of a rectification converter station to an inversion state; in other words, adjust the trigger angle of a converter valve of a thyristor of the rectifier side to be greater than 90 degrees; and step 3, the voltage source type converter of the inversion converter station triggers a single-phase valve in three phases to run straightly and simultaneously locks the other two phases of valves. By adoption of this method, the mixed-type direct current transmission system can safely and reliably pass through the serious failure of the alternating current network of the invertor side; the overvoltage of the inner capacitor of the voltage source type converter and the overvoltage of the direct current side can be limited; and after the failure of alternating current network is cleared, the mixed-type direct current transmission system can be resumed quickly and steadily.

Description

technical field [0001] The invention relates to a fault handling method for a receiving end AC side of a hybrid direct current transmission system. Background technique [0002] HVDC transmission systems can be divided into two types: conventional DC transmission systems (LCC-HVDC) based on thyristor technology and flexible-HVDC systems based on fully controlled power electronic device technology (Flexible-HVDC), both of which have advantages and disadvantages , so the hybrid DC transmission system combining conventional DC transmission and flexible DC transmission will have engineering application prospects. It has the advantages of low conventional DC transmission loss, mature operation technology and flexible DC transmission can supply power to passive networks without commutation failure. The advantages. [0003] However, when the AC grid connected to the voltage source converter on the inverter side (receiving end) of the hybrid DC transmission system suffers a serious...

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Problems solved by technology

[0003] However, when the AC grid connected to the voltage source converter on the inverter side (receiving end) of the hybrid DC transmission system suffers a serious fault, the AC voltage drops severely, and the power output of the inverter side converter on the AC side is severely limited. However, the rectifier side converter still delivers DC power to the inverter side according to the established power reference value. At this time, the input power of the DC side of the voltage source converter on the inverter side is much greater than the output power of the AC side, and the power difference leads to voltage source conversion. The internal energy storage element of the inverter - the capacitor is severely overvoltage. At the same time, because the DC side voltage of the voltage source converter is the sum of the voltages of several internal capacitors, severe overvoltage will also occur

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