Nested Microgrid Control System Fault Isolation
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Solution Overview
Problem
Existing power grid control systems face challenges in accurately detecting and isolating faults, particularly with distributed energy resources (DERs), leading to increased downtime and reduced system reliability due to misinterpretation of fault currents and inaccurate fault detection.
Innovation Solution
A microgrid control system with network controllers that communicate with protective relays, circuit breakers, and switches to detect, locate, and isolate faults, and reconnect healthy portions to other microgrids with sufficient capacity, using topological and proximity classifications to manage fault currents and ensure efficient fault restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If distributed energy resources (DERs) are added to the power grid to provide additional power sources, then system reliability and power availability are improved, but fault detection accuracy deteriorates due to misinterpretation of fault currents from multiple power sources
Solution Approach 1:
The system segments the microgrid into multiple zones and uses distributed zone impedeance measurements to identify fault locations. Each zone independently measures impedeance, and the controller compares these segmented measurements to determine fault presence and location, resolving the ambiguity caused by multiple DER power sources.
Solution Approach 2:
The controller acts as an intermediary that collects and processes impedeance measurements from multiple zones. It uses these intermediate measurements to calculate total impedeance and determine fault conditions, mediating between the multiple DER sources and the fault detection system to achieve accurate identification despite multiple power flow directions.
2Device complexity
If existing power grid control systems are used to detect faults, then system complexity is minimized, but fault responsiveness deteriorates due to inaccurate fault detection and isolation
Solution Approach 1:
The system performs preliminary impedeance measurements in each zone before fault conditions develop. By pre-establishing baseline impedeance values and measurement pathways, the system can rapidly compare current measurements against these pre-established references when faults occur, achieving fast fault detection without complex real-time calculations.
3Object-affected harmful factors
If fault isolation is performed by disconnecting healthy portions of the microgrid, then fault impact is minimized, but system productivity deteriorates due to unnecessary downtime of healthy segments
Solution Approach 1:
The system applies local quality by isolating only the specific zone containing the fault while maintaining operation of other healthy zones. Each zone's impedeance measurements enable precise localization, allowing the controller to disconnect only the affected zone's DERs and loads, thereby minimizing fault impact while maintaining productivity of unaffected portions of the microgrid.
4Reliability
If DERs are used to support isolated healthy portions of the microgrid during faults, then system reliability is improved, but device complexity increases due to capacity matching requirements
Solution Approach 1:
The controller implements feedback by continuously monitoring impedeance measurements from each zone and using this information to determine when and how to reconnect DERs to support isolated healthy portions. The feedback loop compares post-fault impedeance values against pre-fault baselines to automatically identify restoration opportunities, managing DER capacity dynamically without requiring complex manual coordination.
Data Source
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AI summary
Unique systems, methods, techniques and apparatuses of a power grid control system. One exemplary embodiment is a nested microgrid system comprising a first microgrid including a network controller, a second microgrid, a third microgrid, a first restoration path selectively coupled between a second portion of the first microgrid and the second microgrid, and a second restoration path selectively coupled between the second portion of the first microgrid and the third microgrid. The network controller is configured isolate the first portion of the first microgrid from the second portion of the first microgrid, calculate weighting factors for the first and second restoration paths, select the first restoration path using the first weighting factor and the second weighting factor, and couple the second portion of the first microgrid to the second microgrid using the first restoration path.