Flexible DC access AC hybrid line double-end fault distance measurement method

Abstract

The invention provides a flexible DC access AC hybrid line double-end fault distance measurement method which comprises the following steps: (1) after an AC overhead line-cable mixed line fault is detected, acquiring voltage and current information of an AC power supply side of a line, acquiring voltage information of a current converter grid connection point, and obtaining negative sequence components of voltage and current; (2) on the basis of a distributed parameter model, calculating negative-sequence voltage distribution along the line by negative-sequence components of voltage and current collected by an alternating-current power supply side; and (3) calculating the negative-sequence voltage amplitude distribution along the line according to the electrical quantity information of the AC power supply side, comparing the negative-sequence voltage amplitude distribution with the negative-sequence voltage amplitude collected at the grid connection point of the converter, and determining the fault distance through an amplitude difference function according to the characteristic that the amplitude difference between the negative-sequence voltage amplitude distribution and the negative-sequence voltage amplitude collected at the grid connection point of the converter at the fault point is minimum.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a double-terminal fault distance measurement method of an AC hybrid line with flexible DC access. Background technique [0002] Due to the outstanding advantages of flexible control, no commutation failure, and low transmission loss, flexible DC has achieved a large number of practical engineering applications in the areas of asynchronous interconnection of large AC grids and strengthening of regional transmission grids in recent years, gradually forming a flexible DC network. The pattern of AC-DC hybrid transmission system. For AC transmission lines with flexible DC access, in the process of transmitting electric energy to urban load center substations, considering the investment cost and the high failure rate of high-voltage cable intermediate joints, large and long-distance cable lines cannot be used. However, in order to cooperate with th...

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Problems solved by technology

The double-ended ranging method is more accurate and reliable, but compared with the single-ended ranging method, the process is very complicated and has higher requirements for data synchronization and communication technology

[0004] Flexible DC access brings new fault characteristics to AC hybrid lines, and the control strategy of its converter configuration will affect the AC output characteristics, which will affect the performance of existing double-terminal fault location methods

The low-voltage ride-through control strategy of the converter makes the positive-sequence voltage at the grid-connected point and the positive-sequence current flowing through it present a nonlinear time-varying during the fault transient adjustment process, which affects the power supply based on dual Accuracy of Fault Location Method for Terminal Positive Sequence Electrical Quantities

The negative-sequence current suppression strategy of the converter suppresses the output negative-sequence current to zero, which makes the fault location method based on the double-terminal negative-sequence electrical quantity invalid

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