Analysis method and device of influence of direct drive fans on subsynchronous resonance of power transmission system

Abstract

Provided is an analysis method and device of influence of direct drive fans on subsynchronous resonance of a power transmission system. The method comprises the steps of conducting equivalence on a series compensation power transmission system to obtain an equivalent parameters; building a simulation system according to single direct drive fan and a power transmission system equivalent model, obtaining a direct drive fan impedance characteristic of the direct drive fan in a subsynchronous frequency band through frequency scanning, and obtaining a double-fed fan impedance characteristic of a double-fed fan in the subsynchronous frequency band; performing calculating to obtain a mixed fan impedance characteristic after multiple double-fed fans and multiple direct drive fans are connected in parallel and a single fan impedance characteristic after the multiple double-fed fans are connected in parallel according to the direct drive fan impedance characteristic, the double-fed fan impedance characteristic and matching of the double-fed fans and the direct drive fans; judging subsynchronous resonance influence condition of the direct drive fans to the double-fed fan series compensation power transmission system under the matching by comparing the mixed fan impedance characteristic with single fan impedance characteristic. According to the analysis method and device of influence of the direct drive fans on the subsynchronous resonance of the power transmission system, subsynchronous resonance influence of the direct drive fans can be effectively analyzed.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to an analysis method and device for the influence of a direct drive fan on the subsynchronous resonance of a power transmission system. Background technique [0002] Wind power has become an important component of China's energy strategy, but most of China's wind power is concentrated in Xinjiang, Gansu, Inner Mongolia and other northwest regions, while energy load centers are concentrated in southeast coastal areas. Therefore, high voltage, large The capacity of the transmission mode realizes "West-to-East power transmission". New transmission lines will bring problems such as project cost and transmission corridor occupancy, so it is of great significance to improve the transmission capacity of existing AC lines. [0003] Adding series compensation capacitors in the transmission line can reduce the line reactance and improve the static stability limit and transmission ca...

AI Technical Summary

Problems solved by technology

However, this long-distance, high-series power transmission method may induce subsynchronous resonance problems in the wind power system, thereby affecting the safe and stable operation of large-scale wind power bases and external transmission systems.

Previous academic research believed that the negative resistance of double-fed wind turbines at sub-synchronous frequency is the key reason for the divergence of sub-synchronous currents, while direct-drive wind turbines do not participate in the generation of negative resistance due to the decoupling of full-power converters and power grids.

However, through the research on the impedance characteristics of the direct-drive fan, it is found that when the short-circuit capacity of the system is small and the series compensation degree is within a certain range, connecting the direct-drive fan to the double-fed fan-series compensation system will worsen the system damping , increasing the risk of resonance

[0004] At present, there is no method to effectively analyze when the direct drive fan can improve the subsynchronous resonance of the DFIG-SCC system, and when it will worsen the subsynchronous resonance of the DFIG-SCC system

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