An improved method of power frequency variation direction protection suitable for upfc access

Abstract

The invention discloses a power frequency variation direction protection improvement method suitable for UPFC access and belongs to the technical field of UPFC-containing line protection. A relay protection device is arranged at a head end of a line where a UPFC is located, a current transformer (TA) is connected to the head end of the line, voltage transformers (PT) are connected to a P measuringpoint at the head end of the line and an L measuring point at an outlet in a right side of a UPFC series transformer, and positive sequence break variable impedance phase angles of the two measuringpoints during a fault are obtained respectively. Positive direction action area membership functions lambda 1 and lambda 2 and negative direction action area membership functions lambda 3 and lambda 4respectively corresponding to the positive sequence break variable impedance phase angles of the P measuring point and the L measuring point are calculated, a comprehensive membership function mu issolved, and a power frequency variable quantity direction element can correctly judge forward and reverse faults by judging the size relationship between mu and a threshold eta. The method is simple and easy to implement and low in investment, and the problem of misoperation of the power frequency variable quantity direction element caused by the existence of the UPFC in power frequency variable quantity direction protection can be effectively solved.

Description

technical field [0001] The invention belongs to the technical field of UPFC-containing line protection, and in particular relates to an improved method for protecting the direction of power frequency variation suitable for UPFC access. Background technique [0002] Optimizing the power flow distribution of the existing power network is one of the effective methods to solve the current rapid load growth and uneven utilization of transmission channels in my country. Flexible AC Transmission Systems (FACTS) use high-power power electronic devices to quickly and accurately change electrical parameters, and have unique advantages and broad fields in controlling power flow distribution, increasing system transmission capacity, and improving power system stability. application prospects. Typical FACTS devices can be divided into the following three categories according to different ways of connecting to the power grid: 1) Parallel devices, such as Static Synchronous Compensators (...

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Problems solved by technology

[0004] In the existing literature, there are few studies on the fault direction discrimination scheme of the line containing UPFC. Lin Jinjiao et al. ) points out that when the non-UPFC line is faulty, it will cause UPFC line directional protection to malfunction or non-UPFC line directional protection to refuse to operate; Kong Xiangping (Kong Xiangping. Analysis of the impact of unified power flow controller on line longitudinal protection[J]. Protection and Control, 2017,45(2):14-21.) qualitatively analyzed the impact of UPFC on the protection of the power frequency fault component direction, and pointed out that the existence of UPFC on the line may cause the power frequency fault component protection to malfunction in the opposite direction, but No specific solution was given

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