Microgrid Islanding Detection via PMU Voltage Analysis
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Solution Overview
Problem
The transition between grid-tied and islanded modes in microgrids is challenging due to power imbalances and transients, which can lead to instability and unsatisfactory voltage and frequency regulation, especially with electronically interfaced distributed generation units.
Innovation Solution
A control scheme that uses Phasor Measurement Units (PMUs) to detect islanding and estimate power imbalances by analyzing voltage changes within a predefined time window, allowing for immediate adjustments to the power references of distributed generation units to minimize transients and ensure stability during the islanding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DG units are integrated into the microgrid to enhance reliability and provide flexible control, then the system reliability and adaptability are improved, but power imbalances and transients occur during mode transitions causing voltage and frequency instability
Solution Approach 1:
The control scheme performs preliminary actions by detecting islanding conditions and estimating power imbalances before the transition is complete. PMU measurements are analyzed during a predefined time window to proactively determine the average power imbalance, allowing the system to prepare compensation actions in advance, thus preventing voltage and frequency instability during the transition process
2Adaptability or versatility
If the microgrid transitions between grid-tied and islanded modes smoothly, then the adaptability and reliability are improved, but transients and power imbalances occur during the transition process
Solution Approach 1:
The control scheme implements feedback by continuously monitoring PMU measurements and analyzing voltage changes within a predefined time window. The system uses the average value of sPMUt as feedback to determine the power imbalance, then adjusts DG unit power references accordingly. This closed-loop feedback mechanism minimizes transients during mode transitions by continuously adapting to system conditions
Solution Approach 2:
The control scheme changes parameters by adjusting the power references of DG units based on the estimated power imbalance. The system modifies operating parameters (power references) in response to detected islanding conditions, enabling smooth transitions between grid-tied and islanded modes while minimizing harmful transients
3Measurement precision
If PMU measurements are analyzed during a predefined time window to estimate power imbalance, then the measurement precision is improved, but the complexity of detection and control increases
Solution Approach 1:
The control scheme performs preliminary analysis by collecting PMU measurements during a predefined time window before making the power imbalance estimation. This preliminary data collection and averaging process improves measurement precision by reducing the impact of transient fluctuations, while the structured approach keeps the detection complexity manageable
Data Source
AI summary
System and methods are disclosed to handle power imbalance in one or more distributed generation (DG) units: detecting islanding at time t1; selecting Phasor Measurement Unit (PMU) measurements during a pre-defined time window [t1-τ, t1]; checking the time window for an abrupt voltage change; if no sudden change of voltage is detected, determining an average value of sPMUt between t1-τ and t1 and using the average as a best estimate of a system power imbalance; if a sudden change of voltage is detected at time instant t2, determining the average value of sPMUt between t1-τ and t2 and using the average as a best estimate of the system power imbalance; and adjusting a power reference of the DG units based on the best estimated system power imbalance.