Inverter Voltage Deviation Detection for Single-Phase Open Circuits
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Solution Overview
Problem
Existing methods struggle to reliably detect single-phase opens (SPOs) located arbitrarily between a utility power source and the point of interconnection (POI) of an inverter-based distributed energy resource (IBDER) in three-phase electrical power distribution grids.
Innovation Solution
The method involves measuring and calculating the standard deviations of per-phase voltages over successive time intervals, determining a difference value between the maximum and minimum standard deviations, and automatically disconnecting the IBDER if the difference value exceeds a predetermined threshold for a specified time period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current-imbalance methods are used to detect SPO at the POI, then detection simplicity is improved, but detection reliability deteriorates for arbitrarily located SPOs
Solution Approach 1:
The patent changes the detection parameter from current imbalance to voltage standard deviation. By measuring voltage variations over time and calculating standard deviation, the system can detect SPOs at any location along the distribution circuit, not just at the POI. This parameter transformation resolves the contradiction by maintaining operational simplicity while significantly improving detection reliability for arbitrarily located SPOs.
2Productivity
If IBDER current flows into downstream loads during SPO, then voltage regeneration occurs making detection difficult, but continuous operation is required for power supply
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring voltage standard deviation and comparing it against threshold values. The system measures voltage over successive time intervals, calculates standard deviation, and uses this feedback to detect SPO conditions. This allows the IBDER to maintain continuous power supply while the monitoring system reliably detects SPOs despite voltage regeneration effects, resolving the contradiction between productivity and detection difficulty.
3Measurement precision
If SPO detection threshold is set to be sensitive, then detection accuracy is improved, but false positive rate increases
Solution Approach 1:
The patent employs dynamic threshold evaluation by analyzing voltage standard deviation over multiple successive time intervals rather than using a static single-threshold comparison. The system evaluates whether the standard deviation exceeds the threshold for a sustained period, which dynamically adapts to normal voltage fluctuations while maintaining sensitivity to actual SPO conditions. This dynamic approach improves detection accuracy while reducing false positives caused by transient voltage variations.
Data Source
AI summary
Methods, apparatuses, and systems for detecting arbitrarily located SPOs between a utility power source and a POI of an IBDER and mitigating the effects of such a SPO. Generally, a SPO will cause certain persistent, predictable variations and differences in voltages between phases. The standard deviations of the per-phase voltages can be calculated for each of a series of successive time intervals, and a difference value between the maximum and minimum standard deviation for each interval can be determined. If the difference value exceeds a threshold value for successive intervals covering a predetermined time period, the presence of a SPO is reliably indicated, and the IBDER can be automatically disconnected to prevent damage to connected equipment. The threshold value, number of intervals, and time period can be selected to provide appropriate sensitivity and selectivity.