Phase correction method for arbitrary impulse converter transformer current difference

Abstract

The invention relates to a phase correction method for arbitrary impulse converter transformer current difference. When a converter transformer is at a no-load status, a phase difference theta exists in positive sequence current of a line side winding and a valve side winding, and the theta is any angle. The phase correction method comprises the following steps: selecting a side winding of the converter transformer as a reference winding, and performing phase correction to the other side winding current towards the reference winding current; using a phase relationship of three-phase current sequence components on the two sides of the converter transformer, and a conversion method of the sequence components and the phase components to calculate differential current. Due to the adoption of the phase correction method, the differential current of any impulse converter transformer can be calculated, so that a high-voltage direct-current power transmission system safely and stably operates for a long time; the method has the advantages of easily applying and preventing the generation of false differential current. Moreover, according to the phase correction method, a problem that the phase correction is only achieved when the same-phase current phase difference on the two sides of the converter transformer is 30 N (N is an integral number) as the current phase correction method adopts the adding and subtracting of the three-phase current vectors on certain side can be solved.

Description

technical field [0001] The invention belongs to the technical field of power systems, and in particular relates to a phase correction method when the phase difference of the phase currents of the same name on both sides of a converter transformer is at any angle. Background technique [0002] Due to its unique advantages, such as: long distance, high power, asynchronous networking, fast power adjustment, power flow controllability, transmission economy, etc., HVDC transmission is more and more widely used. In order to reduce the harmonic components of the system, different connection methods of transformer windings are used. At present, most high-voltage DC projects use 12-pulse valve group connection methods, such as figure 1 As shown, it provides two sets of three-phase symmetrical commutation voltages with equal amplitudes and a phase difference of 30° (fundamental electrical angle) for the two transformers connected in series, so as to realize twelve-pulse commutation. ...

AI Technical Summary

Problems solved by technology

At this time, the differential protection of the converter transformers T2 and T4 can still be realized by the formula (3), but the differential protection between the converter transformers T1 and T3 cannot use the above formula to realize the phase correction of the phase current of the same name, so it is impossible to calculate the The three-phase differential current of T1 and T3, that is, the current phase correction method is only applicable to the case where the phase difference of the phase current of the same name on both sides of the converter transformer is 30N (N is an integer)

Images