High voltage direct current system control method

A control method, high-voltage DC technology, applied in power transmission and AC networks, etc., can solve problems such as commutation failure, voltage distortion, and little research, and achieve the effect of preventing serious deviations

Inactive Publication Date: 2015-11-18
SICHUAN UNIV +4
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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 reduction of the fundamental voltage. The traditional low-voltage current limiting unit VDCOL (VoltageDependentCurrentOrderLimiter) control is to pass the limit when the DC voltage is detected. DC current to avoid commutation failure without considering the effects of harmonic distortion
In fact, with the increase in the complexity of the power gr

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[0023] The purpose of the present invention is to provide a high-voltage direct current system control method that can suppress the commutation failure caused by harmonics, mainly adding a commutation failure current-limiting prevention controller that considers the harmonic distortion rate after the VDCOL on the inverter side of the DC transmission system VDDCFP. The principle is that the time area of ​​the commutation voltage required for the commutation process of the DC transmission system is fixed (by the DC current I d Decision), harmonics will cause voltage distortion, and voltage distortion will increase the corresponding commutation time, thereby increasing the commutation overlap angle, reducing the arc extinguishing angle, and causing commutation failure. Therefore, in the commutation bus voltage harmonics When the distortion rate is high, by reducing the DC current, the influence of harmonics on the time area of ​​the commutation voltage is not enough to cause commut...

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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 ...

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Application Information

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IPC IPC(8): H02J3/36
CPCY02E60/60
Inventor 刘天琪王峰李保宏李兴源彭慧敏张英敏曾琦
Owner SICHUAN UNIV
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