Predictive commutation failure prevention method and device

Abstract

The invention relates to a predictive commutation failure prevention method and device. In the method, a needed angle Alpha is taken from output of a phase-locked loop and the zero crossing point and half-period time of an AC synchronous voltage no longer need to be measured. Because the commutation margin areas of 12 bridge arms are calculated at the same time, the pre-trigger valve number does not need to be considered anymore, and minimum values of the 12 areas are selected so that the effect of commutation failure prevention is better. DC shaping and a nonlinear compensation technology are used to correct post-trigger commutation voltage and DC fluctuation so as to enhance the commutation failure prevention capability.

Description

technical field

[0001] The invention relates to the field of prevention of predictive commutation failure in direct current transmission, in particular to a method and device for preventing predictive commutation failure. Background technique

[0002] Commutation failure is one of the most common failures of inverters in DC transmission systems. Mainly in the inverter, when the phase is commutated between the two bridge arms, if the valve that has just exited conduction fails to recover the blocking ability within the time of reverse voltage action, or the commutation process fails during the reverse voltage If it can be completed, the valve that was originally scheduled to exit will be re-conducted when the valve voltage changes to positive. Failure of commutation will lead to adverse consequences such as reduction of DC voltage, reduction of transmission power, increase of current, shortening of the life of the converter valve, DC bias of the converter transformer, and ov...

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