Inverter-side control method and system based on extra high voltage direct-current transmission project

Abstract

The invention discloses an inverter-side control method and system based on an extra high voltage direct-current transmission project. The method comprises the steps of additionally adding an extinction angle modulation module at the inverter-side control system of a direct-current transmission system, increasing a reactive compensation capacity of an inverter station and setting an extinction angle given value when the direct-current transmission system is in a steady state; respectively obtaining second alternating current bus voltage values V0 and Vac at an inverter side when the system isin the steady state and goes wrong; judging whether the extinction angle given value is changed or not, and starting the extinction angle modulation module when a deviation between V0 and Vac is not in the range of +/-5%; and stopping modulation until the second bus voltage level restores to the given range, and restoring the original extinction angle set value. According to the method, the probability of commutation failures of a direct current can be reduced by additionally adding the extinction angle modulation module, the fluctuation range of the alternating current bus voltage is inhibited, the recovery speed of a direct current power is accelerated and the stability of the alternating current power grid voltage is improved.

Description

technical field [0001] The invention belongs to the technical field of electrical engineering, and more specifically relates to an inverter-side control method and system based on UHVDC power transmission projects. Background technique [0002] UHV DC transmission is suitable for long-distance and large-capacity power transmission, and can realize the optimal allocation of resources, which plays an important role in my country's energy strategy. With the rapid development of UHV DC transmission technology, the dominant form of my country's transmission network has undergone profound changes, from the initial pure AC system to the ultra-high voltage small-capacity DC and AC hybrid, and further developed to UHV large-capacity AC-DC Mixed layout. However, since the UHV DC project usually transmits a large power, the DC transmission power and the reactive power absorbed by the converter will change greatly when disturbed. After the weaker AC system is impacted, it is easy to cau...

AI Technical Summary

Problems solved by technology

However, since the UHV DC project usually transmits a large power, the DC transmission power and the reactive power absorbed by the converter will change greatly when disturbed. After the weaker AC system is impacted, it is easy to cause the receiving end system The problem of poor transient stability of the

[0003] For example, Hunan Power Grid, when the Qishao UHV DC is connected at ±800 kV, the proportion of received power of the grid increases, the reserve capacity of the system unit decreases relatively, the short-circuit ratio of the receiving end system decreases relatively, and the transient voltage support capability Insufficient; at the same time, if an N-1 fault occurs in the vicinity of the converter station, the DC is prone to continuous commutation failure, which will cause large fluctuations in the system voltage and cause the system to lose stability

[0004] At present, common measures to improve voltage stability include: changing the main wiring of the AC system to increase the strength of the AC system at the receiving end, but the actual operation of this method is difficult, so the current main measures are to optimize the parameters of the DC transmission system Or increased module control links, such as the low-voltage current limiting link in the DC transmission control system and the installation of reactive power compensation equipment to increase reactive power support for the receiving end system, etc. The commonly used reactive power compensation modules include synchronous condensers, SVC, STATCOM, Fixed capacitors, etc. Synchronous condensers can adjust reactive power output according to changes in AC bus voltage, but their operation and maintenance costs are high; static var compensation equipment such as SVC and STATCOM are less expensive than synchronous condensers, and their response speed is faster. But its structure is relatively complicated; adding a capacitor for compensation is the most economical solution, but when the system voltage drops, the reactive power output by the capacitor will also drop a lot, which is not conducive to maintaining the stability of the system voltage

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