Valve section short circuit test device and test method in flexible DC transmission system

Abstract

The invention provides a valve-section short circuit test device in a flexible DC power transmission system. After that a valve section reaches a highest stable junction temperature and achieves heat balance, a control unit controls a sinusoidal current loop to output a group of amplitude and cycle time adjustable sinusoidal currents and controls a DC attenuation current loop to output a group of amplitude adjustable DC attenuation currents; after reaching a peak value, the DC attenuation currents are superposed with the sinusoidal currents to form a short-circuit test current; and when the waveform of the short-circuit test current does not exceed 0, fifth and sixth switching assemblies are switched on, the current whose waveform does not exceed 0 is input to the valve section, a third switching assembly is also switched on when the waveform of the short-circuit test current exceeds 0, and the current whose current exceeds 0 flows through the third switching assembly, and the valve section bears an inverse voltage when the short-circuit test current is interrupted. Correspondingly, a short-circuit test method is provided. Thus, the valve section can withstand corresponding transient current, voltage and thermal stress in the same practical condition.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a short-circuit test device for a valve section in a flexible direct current transmission system, and a short-circuit test method for a valve section in a flexible direct current transmission system. Background technique [0002] In the flexible DC transmission system based on the H half-bridge sub-module topology, after a short circuit occurs on the DC side, the system will quickly block all the IGBTs in each H half-bridge sub-module, and open the IGBTs connected in reverse parallel with each H half-bridge sub-module lower tube T2. SCR (Thyristor), and issue a system protection command to disconnect the front-end AC circuit breaker. However, since the disconnection of the AC circuit breaker at the front stage takes a long time, usually about 100ms, in order to verify the reliability of the diode D2 and SCR connected in antiparallel with the lower tub...

AI Technical Summary

Problems solved by technology

However, when the DC decay current rises to its peak value, the short-circuit current should flow through the upper transistor T1 of the H half-bridge sub-module instead of the diode D2 and SCR connected in antiparallel with the lower transistor T2, which results in an antiparallel connection with the lower transistor T2 The diode D2 and SCR are not fully resistant to the same short-circuit current stress as the actual;

[0006] 2) It is impossible to realize the assessment of the H half-bridge sub-module's ability to withstand back pressure under the condition that the short-circuit current of the measured valve section crosses zero intermittently;

[0007] 3) It cannot meet the assessment of the thermal stress resistance of the H half-bridge sub-module under the most severe conditions, that is, the short-circuit test cannot be performed immediately after the valve section under test operates to the highest steady-state junction temperature and enters thermal equilibrium

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