Voltage Sag Analysis for Multi-Stage Grid Fault Control
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Solution Overview
Problem
Current methods for controlling voltage sags are inadequate for multi-stage events, which are increasingly frequent due to the integration of distributed generation devices and complex power system protections, leading to challenges in determining cause, classifying fault lines, and accurately inferring specific fault events.
Innovation Solution
A system comprising a power quality monitoring device, voltage sag analysis device, and early warning device that analyzes voltage sag data and fault clearing information to determine the cause of multi-stage voltage sags, adjust relay protection devices, and issue notifications for retrofitting electric power stabilizing devices, reducing computational load and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If comprehensive monitoring devices are installed at all bus lines to accurately capture voltage sags, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent introduces a voltage sag analysis device as an intermediary that processes data from limited monitoring devices and infers sag characteristics at unmonitored bus lines. This mediator enables comprehensive voltage sag assessment without requiring monitoring devices at every location, thus maintaining measurement precision while reducing device complexity
Solution Approach 2:
The system creates a virtual model of voltage sags at unmonitored locations by copying and analyzing patterns from monitored locations. Through data processing and inference algorithms, the system reconstructs sag characteristics for the entire power system based on partial measurements, avoiding the need for physical monitoring devices at every bus line
2Measurement precision
If detailed analysis of all candidate fault lines is performed to determine multi-stage sag causes, then measurement precision is improved, but productivity decreases due to high computational load
Solution Approach 1:
The patent segments the fault analysis process into multiple stages: initial data collection, preliminary filtering of candidate fault lines based on voltage sag characteristics, detailed analysis of filtered candidates, and final determination. This segmentation allows the system to process large numbers of candidate fault lines efficiently by eliminating unlikely candidates early, maintaining accuracy while improving productivity
Solution Approach 2:
The system performs partial analysis on all candidate fault lines by first applying quick filtering criteria to eliminate obviously incorrect candidates, then conducting comprehensive analysis only on the remaining plausible candidates. This partial action approach ensures high accuracy for the final result while significantly reducing overall computational load and improving analysis speed
3Reliability
If relay protection devices operate with traditional settings to ensure grid stability, then reliability is maintained, but adaptability decreases when facing multi-stage voltage sags
Solution Approach 1:
The patent implements dynamic adjustment of relay protection device parameters based on real-time voltage sag detection and analysis. When multi-stage sags are detected, the system automatically modifies protection settings and coordination parameters to adapt to the specific sag pattern, enabling the protection system to maintain reliability while becoming adaptable to different sag scenarios
Solution Approach 2:
The system establishes a feedback loop where voltage sag characteristics are continuously monitored, analyzed, and used to adjust relay protection device settings. The analysis device provides feedback information about detected sags to the protection devices, which then modify their operation accordingly, ensuring both reliability through stable normal operation and adaptability through dynamic response to multi-stage sags
Data Source
AI summary
Disclosed is a system and a method for controlling a multi-stage voltage sag. The system includes a power quality monitoring device with a processor, a voltage sag analysis device, a voltage sag data storage device, and an early warning device. The power quality monitoring device is configured to read voltage sag data and fault clearing information and send the voltage sag data to a power terminal device. The voltage sag analysis device is configured to determine a cause of the multi-stage voltage sag at different grid locations; determine an updated value of a fault clearing time of a relay protection device and retrofit location information of an electric power stabilizing device; control a corresponding relay protection device to adjust a count of capacitors and types of the capacitors to be connected to a circuit; and issue an early warning notification of retrofitting the electric power stabilizing device to a user.