Voltage Angle Sudden-Change Detection for Electrical Islanding
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Solution Overview
Problem
Current electrical islanding detection methods are either costly, unreliable, or have a large 'non-detection zone', failing to accurately and sensitively detect islanding phenomena in power systems without impacting power quality.
Innovation Solution
A method and apparatus that utilize three-phase voltage analysis, specifically calculating voltage angle sudden-changes and determining their directions to differentiate between electrical islanding and system faults, reducing mal-operations and costs by employing a low-cost, passive detection approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active methods are used for islanding detection by periodically disturbing output voltage or frequency, then detection sensitivity is improved, but power quality deteriorates and effectiveness decreases when multiple distributed generations interact
Solution Approach 1:
The patent replaces active disturbance-based detection (mechanical/electrical intervention) with passive voltage angle analysis (electrical measurement). By analyzing the sudden change in voltage angle between distributed generation and grid voltage without injecting disturbances, the method achieves sensitive islanding detection while avoiding power quality degradation associated with active methods
Solution Approach 2:
The patent introduces voltage angle as an intermediary parameter to detect islanding. Instead of directly detecting islanding through voltage or frequency disturbances, the method uses the voltage angle difference between DG and grid as a mediator indicator, which changes characteristically during islanding events without requiring active injection
2Object-affected harmful factors
If passive methods such as under frequency, over frequency, under voltage, or over voltage protection are used, then power quality is maintained, but detection sensitivity decreases due to large non-detection zone
Solution Approach 1:
The patent changes the detection parameter from traditional voltage magnitude or frequency (used in passive methods) to voltage angle. By monitoring the sudden change in voltage angle between distributed generation and grid voltage, the method achieves high detection sensitivity while maintaining the passive, non-intrusive nature that preserves power quality
Solution Approach 2:
The patent uses a simplified voltage angle measurement approach that focuses on the critical parameter (angle sudden change) rather than comprehensive system analysis. This partial action on the most discriminative parameter enables sensitive detection without the complexity and non-detection zones of traditional passive methods
3Measurement precision
If ROCOF or VVS methods are used for islanding detection, then detection sensitivity is improved, but reliability decreases due to mal-operation during system faults
Solution Approach 1:
The patent establishes a baseline voltage angle reference before islanding occurs and compares subsequent voltage angle changes against this reference. By having the voltage angle relationship established in advance during normal operation, the method can reliably distinguish between normal variations and actual islanding events, reducing false operations during faults
Solution Approach 2:
The patent converts the voltage angle parameter, which can be affected by system faults, into a beneficial detection tool. By analyzing the sudden change in voltage angle between DG and grid voltage, the method transforms a potentially problematic parameter into a reliable islanding indicator that maintains high sensitivity while improving reliability through characteristic pattern recognition
4Reliability
If communication-based islanding detection is used to issue trip commands, then detection reliability is improved with no non-detection zone, but system complexity and cost increase due to special communication network requirements
Solution Approach 1:
The patent enables the distributed generation system to self-detect islanding conditions by analyzing its own voltage angle relationship with the grid. The DG unit independently monitors the voltage angle between its output and the grid voltage, eliminating the need for external communication networks or centralized control systems while achieving reliable detection
Solution Approach 2:
The patent extracts the islanding detection function from the communication system and implements it locally within the distributed generation unit. By taking out the detection capability from the communication infrastructure and embedding it in the DG control system, the method eliminates communication network complexity while maintaining detection reliability
Data Source
AI summary
The present invention provides method, apparatus, and computer readable storage medium for an electrical islanding detection. The method for electrical islanding detection method includes: receiving a three-phase voltage in an electrical power system; for the three-voltage voltage, calculating a voltage angle sudden-change of each phase, respectively; determining whether an absolute value of the voltage angle sudden-change of each phase is greater than a first angle sudden-change setting value; determining whether directions of the voltage angle sudden-changes of three phase are the same if the absolute value of the voltage angle sudden-change of each phase is greater than the first angle sudden-change setting value; and determining that the electrical islanding appears if the directions of the voltage angle sudden-changes of the three phases are the same.