Meter Adapter Isolation for Islanded Microgrid Power Continuity
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Solution Overview
Problem
Grid-tied renewable energy systems shut down during grid outages, preventing power generation and distribution from local secondary energy sources due to shutdown requirements defined by National Electric Code, ANSI/UL 1741, California Rule 21, and IEEE 1547, and appliances operate inefficiently with varying frequencies.
Innovation Solution
A microgrid system with an adapter and power controller that isolates secondary power systems from the grid, allowing continued power supply by disconnecting from the grid during outages and converting DC power to AC power with variable frequency to match load requirements, using sensors and frequency converters to manage grid information and energy flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grid-tied inverters are connected to the electrical grid to enable power distribution, then power can be supplied to the facility, but the system must shut down during grid outages to prevent backfeeding, resulting in loss of power supply continuity
Solution Approach 1:
The patent introduces an adapter as an intermediary device positioned between the inverter and the electrical grid. This adapter includes a disconnect switch that physically isolates the inverter from the grid during outages, eliminating backfeeding risk while maintaining continuous power supply to the facility. The adapter acts as a mediator that enables safe islanded operation without requiring inverter shutdown.
2Object-affected harmful factors
If the inverter shuts down during grid outages to comply with safety codes, then backfeeding is prevented, but power generation and distribution from local secondary energy sources ceases
Solution Approach 1:
The system is segmented into two independent parts: the grid-connected portion (controlled by the adapter's disconnect switch) and the islanded portion (inverter supplying local loads). This segmentation allows the inverter to continue generating power for the facility during grid outages while the adapter ensures physical disconnection from the grid, simultaneously achieving safety compliance and maintaining productivity.
3Adaptability or versatility
If the electrical grid frequency is maintained at predetermined values (50 Hz or 60 Hz), then grid compatibility is ensured, but appliances requiring variable frequency operation cannot optimize their performance
Solution Approach 1:
The patent implements dynamic frequency control where the inverter can operate at variable frequencies when islanded from the grid. The adapter enables this by providing physical disconnection, allowing the inverter to adjust output frequency according to load requirements rather than being constrained to fixed grid frequencies, thus achieving both adaptability and simplified compliance through automatic mode switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures continuous power supply from secondary sources, optimizes energy efficiency by matching frequency to load demands, and prevents backfeeding into the grid, enhancing the reliability and effectiveness of renewable energy systems.
Implementation Method 1
The adapter can isolate a secondary power system, such as grid-tied solar system or a battery system from the electric grid, prevent the isolated or islanded secondary power system from feeding power back into the grid
Implementation Method 2
The power controller is further configured to convert the generated DC power from the secondary energy source to second AC power and to supply the second AC power to loads
Data Source
AI summary
A microgrid comprises a meter adapter for interconnection to the electric grid, facility loads, and renewable energy resources using connectors, bus bars, and switches. Adapter connectors and internal bus bars and can be stressed with excessive heat rise from heat losses that arise from carrying high currents due to constraints in the physical size and airflow restrictions. Exhaust ports and/or vents are arranged to achieve a chimney cooling effect in such conditions to meet stringent UL requirements against resultant heat rise within a meter adapter.