Islanding Detection Device Using Reactive Power Injection
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Solution Overview
Problem
In grid interconnection systems, especially in areas far from the electric main line, frequency variations due to disturbances can lead to erroneous detection of islanding operations, causing distributed power supplies to be disconnected from the grid power supply unnecessarily, resulting in safety issues and missed power sale opportunities.
Innovation Solution
A detection device and method that monitor frequency and voltage changes to accurately determine islanding operations, adjusting power supply amounts and using reactive power injection to differentiate between correct and erroneous detections, thereby preventing unnecessary disconnections and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency-based islanding detection is used in areas far from the electric main line, then islanding operation can be detected, but frequency variations due to disturbances cause erroneous detection and unnecessary disconnection
Solution Approach 1:
The patent introduces a power processing unit as an intermediary between the detection unit and the disconnection control. This unit actively modifies the power supply amount (increasing or decreasing it) to create a controlled disturbance that amplifies frequency variations only when actual islanding occurs, thereby mediating between the detection requirement and the disturbance sensitivity problem
Solution Approach 2:
The patent changes the power supply amount parameter dynamically based on detection results. When islanding is detected, the power supply amount is adjusted (increased or decreased) to create observable frequency variations. This parameter change allows the system to differentiate between natural frequency fluctuations and true islanding conditions
2Measurement precision
If the power supply amount is changed to confirm islanding operation, then accurate detection can be achieved, but voltage instability occurs during the confirmation period
Solution Approach 1:
The patent performs preliminary action by changing the power supply amount immediately when islanding is detected, rather than waiting for voltage stabilization. This proactive approach allows the system to create the necessary frequency variations for accurate detection before voltage instability becomes problematic
Solution Approach 2:
The patent introduces dynamic control of the power supply amount based on real-time detection results. The system transitions from a static power supply mode to a dynamic mode where the power amount is actively adjusted to facilitate detection, accepting temporary voltage instability as a necessary trade-off for accurate measurement
3Measurement precision
If reactive power injection is used to amplify frequency variations, then islanding detection sensitivity is improved, but system complexity increases
Solution Approach 1:
The patent makes the power processing unit multi-functional by combining its existing power amount control function with a new frequency variation amplification function. Instead of adding a separate reactive power injection device, the existing unit is enhanced to perform both power regulation and detection assistance, thereby achieving sensitivity improvement without increasing overall system complexity
Data Source
AI summary
A detection device includes a first detection unit that detects whether a power source may be in an islanding operation based on a frequency of an power supplied from a power source connected to a system, a power processing unit that changes the amount of power supplied from the power supply to the system in response to that the first detection unit detects that the power source may be in the islanding operation, a second detection unit that detects a voltage of a system with the power supply amount having been changed, and a disconnection processing unit that determines whether to disconnect a power source from a system in response to a change in a voltage of a system with the power supply amount having been changed.