Micro-grid dynamic self-adapting relay protection method and self-adapting protection device

Abstract

The invention discloses a micro-grid dynamic self-adapting relay protection method which is based on a central control unit and multiple self-adapting protection devices. The method comprises the steps of collecting analog quantity and digital quantity information in a micro-grid in real time, carrying out full network connectivity judgment on line, and obtaining a real-time network topology structure; establishing calculation modules for distributed power sources, branch subsystems and loads inside and outside the micro-grid, and establishing a state estimation module; transmitting calculated micro-grid operation state information to all the self-adapting protection devices, and matching area protection constant values after output optimization according to a setting valve rule library. Relay protection of a system can be achieved in grid connection, intelligent protection can be achieved in isolated grid operation, misoperation and operation failure of the system can be reduced, the usability of the micro-grid system can be improved. The invention further provides the self-adapting protection device and an internal integration setting valve rule library, protection, measurement and control are integrated, and real-time protection and control of regions can be achieved well.

Description

technical field [0001] The invention relates to the field of low-voltage micro-grid relay protection, in particular to a micro-grid dynamic adaptive relay protection method and an adaptive protection device used in the method. Background technique [0002] Like conventional power systems, microgrids also need to meet the requirements of safety and stability, and their relay protection principles must meet reliability, quickness, sensitivity and selectivity. When the microgrid is connected to the grid, its power flows in two directions. The current magnitude and direction of incoming line switch and feeder switch are closely related to microgrid power generation and load power consumption, and cannot be uniquely determined. Line protection algorithms based on power direction cannot be used, and new methods can only be found to realize microgrid protection. . [0003] At the same time, the microgrid access uses a large number of distributed power sources realized by power el...

AI Technical Summary

Problems solved by technology

In the fault analysis of the traditional power grid, it is often regarded as an infinite source. When a short-circuit fault occurs, the fault current can be more than ten times the normal current; while the inverter is a constant current source. When a short-circuit fault occurs when it is connected to the grid, the output current of the inverter is only increases slightly and remains stable, but the voltage at the inverter terminal decreases significantly, which affects the conventional distribution network relay protection

Prone to misoperation of protective devices, refusal to operate and unsuccessful reclosing

[0004] There are three problems in the current micro-grid relay protection design: 1. It is increasingly difficult to meet the requirements of the traditional relay protection mode of "pre-setting, real-time action, and regular inspection", and the protection cannot be foreseen in the design process. For all system conditions, the changes of the system should be considered to realize the self-adaptive setting of the protection

2. When the microgrid system is in a tense state, the misoperation of the protection will make the system worse, which will lead to the repeated start and stop of the distributed power supply

In many cases, due to manpower shortage or difficulty in planning and other reasons, the relay protection setting inspection cannot be carried out in accordance with the regulations, and some relay protection setting values ​​have reached a critical state and have not been noticed by engineers.

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