A high voltage direct current system control method

Abstract

The invention discloses a high voltage direct current system control method. VDDCFP is arranged after a VDCOL controller. A VDDCFP control process comprises the steps that S1, three-phase voltage amplitude of an inverter side is monitored in real time, and the voltage value of each sub harmonic of a voltage instantaneous value through Fourier decomposition; S2, voltage distortion current limiting is carried out, namely the harmonic distortion rate is calculated through the voltage amplitude of each sub harmonic after Fourier decomposition, and the maximum harmonic distortion rate in three-phase voltage is taken as a feedback signal; S3, direct current deviation current limiting is carried out, namely the difference between a direct current instantaneous value Id and a rated value Id_ref is calculated in a direct current setting value, and the difference is used as an input signal with the feedback signal in step S2 in a gain process; and S4, an optimizing algorithm is used to select the appropriate gain size. According to the invention, when the harmonic distortion rate of commutation bus voltage is high, direct current is reduced; and commutation is failed due to insufficient influence of harmonics on commutation voltage time area.

Description

technical field [0001] The invention relates to the field of high-voltage direct current system control, in particular to a control method for preventing commutation failure in a high-voltage direct current transmission system. Background technique [0002] Due to its strong controllability and large transmission capacity, DC transmission is widely used in long-distance power transmission and has high economic benefits. Commutation failure is a principle problem of traditional DC transmission system based on thyristor commutation principle. With the development of my country's UHV DC transmission technology, the power of single-circuit DC transmission is getting larger and larger, and the number of multi-feed DC drop points is increasing. When commutation failure occurs, the disturbance to the connected AC system is also increasing. The larger the value, the more consecutive commutation failures will cause the DC transmission system to be blocked. [0003] Voltage drop and ...

AI Technical Summary

Problems solved by technology

At present, most of the research is based on the commutation failure prevention measures (such as CFPREV, commutation failure prevention) and recovery strategies based on the fundamental voltage reduction. The traditional low-voltage current limiting unit VDCOL (Voltage Dependent Current Order Limiter) control is to detect When the DC voltage decreases, the DC current is limited to avoid commutation failure, without considering the influence of harmonic distortion

In fact, with the increase in the complexity of the power grid and the use of a large number of power electronic devices, there are more and more factors that cause voltage distortion of the DC converter bus, and in the recovery stage of the DC transmission system, the rise of the DC current will cause the saturation of the converter transformer , the generation of a large number of harmonics will also cause voltage distortion, which will cause commutation failure

At present, there are few researches on the control methods to suppress the commutation failure caused by harmonics

Images