A self-synchronizing resistance differential protection method for a DC boost collection access system

Abstract

The present invention provides a self-synchronizing resistance differential protection method for a DC step-up collection access system. The method comprises continuously obtaining the voltage samplevalues of ND sampling points, and if the ND sampling points all satisfy |u[n]-u[n-N]|>[epsilon], determining that the DC step-up collection access system fluctuates; determining the time scale tD of the NDth sampling point as a time tick starting point; defining the differential resistance, and determining a specific fault type according to the specific value of the differential resistance; and for an in-area fault with transition resistance and a metallic in-area fault, transmitting a start differential protection command. In the present application, the time scale tD of the NDth sampling point is determined as the time tick starting point, and by using the characteristic that the cable of the DC step-up collection access system has a short length, the time tick starting point is determined based on the sudden change amount of voltage or current so as to realize the instant synchronization of data at different ends. The method defines the differential resistance, establishes the mechanism of resistance differential protection, realizes the identification of in-area faults, and has good protection sensitivity and selectivity.

Description

technical field [0001] The present application relates to the technical field of power grid protection, and in particular to a method for self-synchronizing resistance differential protection of a DC step-up converging access system. Background technique [0002] With the continuous development of the national distribution network and the continuous improvement of the automation level of the distribution network, the requirements for the reliability of the power supply are getting higher and higher. Various intelligent monitoring and protection devices for the automation of the distribution network are important to improve the reliability of the power supply. Protection, especially the fault isolation and power supply self-recovery functions in the distribution network, among which the differential protection has incomparable advantages in the rapid detection and isolation of distribution network faults compared to other intelligent devices. Differential protection usually r...

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Problems solved by technology

Using GPS time synchronization and NTP time synchronization is also a common synchronization method for high-voltage transmission lines. However, due to the addition of auxiliary equipment, it reduces the technical economy and also brings the risk of incorrect action of protection due to auxiliary equipment failure.

In addition, some studies have proposed a method of using reference vectors to achieve synchronization, but because the accuracy of this synchronization method is affected by the line model and DC attenuation factors, it is difficult to apply in practice

[0004] For the DC boost collection and connection system of photovoltaic power plants, there are many branches and the system topology is complex. The data synchronization method using the traditional high-voltage power grid does not have good economic and technical characteristics, and the DC boost and collection connection can be realized without adding any auxiliary equipment. The data synchronization and differential protection of the input system are relatively difficult

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