Harmonic instability evaluation method for DC transmitting and receiving end weak systems

A stable evaluation and harmonic technology, which can be applied to DC circuits to reduce harmonics/ripples, AC networks to reduce harmonics/ripples, harmonic reduction devices, etc. It can solve problems such as ignoring harmonic impedance and achieve accurate The effect of the analysis results

Inactive Publication Date: 2018-12-28
ELECTRIC POWER RESEARCH INSTITUTE, CHINA SOUTHERN POWER GRID CO LTD +2
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Problems solved by technology

[0004] In the judging methods for the harmonic instability of the DC transmission system, only the harmonic amplification phenomenon caused by the modulation of the converter is considered when there is a harmonic source in the system, but these judging methods ignore the harmonics caused by the system itself. There is resonance in the wave impedance

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  • Harmonic instability evaluation method for DC transmitting and receiving end weak systems
  • Harmonic instability evaluation method for DC transmitting and receiving end weak systems
  • Harmonic instability evaluation method for DC transmitting and receiving end weak systems

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Embodiment Construction

[0049] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. The method for evaluating harmonic instability in weak systems at the DC sending and receiving ends includes the following steps:

[0050] Step 1: Calculate the AC side current of the converter:

[0051] Assume that at time t, there is a fundamental frequency harmonic component on the DC side of the converter as

[0052]

[0053] In the formula, I dc1 is the fundamental frequency harmonic current amplitude of the DC side, ω is the angular frequency, is the initial phase.

[0054] According to the switching function modulation principle, after it is modulated to the AC side of the converter, two currents with the same phase are generated, as shown in formula (2).

[0055]

[0056] In the formula, is the second positive sequence harmonic current on the AC side at time t; is the zero-order negative-sequence harmonic current ...

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Abstract

A harmonic instability evaluation method for DC transmitting and receiving end weak systems comprises the steps: at first, the current of the AC side of a converter and the positive sequence second harmonic current generated by the DC bias magnetic field are calculated, then the sum of the positive sequence second harmonic current generated by DC bias and the second harmonic current generated by converter modulation is calculated, then the second harmonic impedance from the converter transformer valve side to the AC system is calculated, and then the harmonic voltage at the outlet of the sending-end converter station in the port impedance network is calculated. Finally, the harmonic instability of the system is judged according to the phase angle difference between the AC and DC harmonic impedance equivalents. A method for judging the harmonic instability of a DC transmiting and a receiving end weak system based on a Nyquist stability criterion and the DC bias magnetic action of a converter transformer and considering the equivalent harmonic impedance of an AC system and a DC system, wherein the considered factors are comparatively identical with the conditions in actual application, so that more accurate analysis results can be obtained.

Description

technical field [0001] The invention relates to the technical field of high-voltage direct current transmission harmonic analysis, in particular to a method for evaluating harmonic instability of a weak system at a direct current transmission and receiving end. Background technique [0002] With the development of China's HVDC transmission technology, China has become the country with the most DC transmission lines, the highest transmission voltage level and the largest transmission capacity in the world. Compared with the traditional high-voltage AC transmission technology, DC transmission has the advantages of asynchronous networking, large transmission capacity, low loss, flexible and fast power flow regulation, short-circuit current limitation, saving transmission corridors, and high degree of intelligence, making it a long-distance large-capacity Widely used in power transmission engineering. With the rapid development of high-voltage direct current transmission techno...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J1/02H02J3/36H02J3/01
CPCH02J1/02H02J3/01H02J3/36H02J2203/20Y02E40/40Y02E60/60
Inventor 柳勇军涂亮赵睿张野杨健赵利刚周挺辉刘天琪陈相卢智雪常鹏飞
Owner ELECTRIC POWER RESEARCH INSTITUTE, CHINA SOUTHERN POWER GRID CO LTD
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