Microgrid Fault Protection Using Grid Reconnection Threshold Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microgrids face complex and expensive circuit protection designs due to varying fault currents in grid-connected and islanded modes, which can be unreliable and susceptible to cyberattacks when using intelligent devices.
Innovation Solution
Implementing a controller that manages electrical faults by isolating the microgrid from the grid and reconnecting it when fault currents are below a threshold, using fixed threshold current interrupters to leverage the grid's transient current for fault clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intelligent circuit protection devices are used to vary trip setpoints based on operating mode, then fault protection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a current source device as an intermediary component that provides supplemental fault current during islanded mode. This mediator enables simple fixed-setpoint circuit breakers to function effectively by ensuring sufficient current is available to trip them during faults, without requiring the breakers themselves to be complex or intelligent.
Solution Approach 2:
The patent replaces expensive intelligent circuit protection devices with inexpensive fixed-setpoint circuit breakers. The system accepts that these simpler devices have limitations but compensates for them through the current source device, achieving cost reduction while maintaining protection capability.
2Adaptability or versatility
If intelligent circuit protection devices with communication networks are used, then fault protection adaptability is improved, but susceptibility to cyberattacks increases
Solution Approach 1:
The patent eliminates intelligent circuit protection devices with communication networks and replaces them with simple fixed-setpoint circuit breakers. This removes the cyberattack vulnerability entirely while maintaining fault protection adaptability through the current source device that ensures sufficient fault current is available in islanded mode.
3Device complexity
If fixed-setpoint circuit breakers are used in islanded mode, then device simplicity is improved, but fault current magnitude becomes insufficient
Solution Approach 1:
The current source device acts as a mediator that supplements the fault current during islanded mode operations. It detects when the microgrid is islanded and provides additional current to ensure the total fault current magnitude is sufficient to trip the simple fixed-setpoint circuit breakers.
Solution Approach 2:
The system changes the operating parameters of the current source device based on the microgrid's operating mode. When islanded mode is detected, the current source device activates and adjusts its current output to ensure sufficient fault current magnitude is available for circuit breaker tripping.
Data Source
AI summary
In one aspect, a controller for managing electrical faults in a microgrid is provided. The microgrid includes electrical loads, electrical sources, and circuit protection devices that selectively couple the electrical loads and the electrical sources with each other. The controller comprises at least one processor configured to direct a grid tie switch to open to electrically isolate the microgrid from an electric grid, determine, in response to directing the grid tie switch to open, that an electrical fault exits in the microgrid, and determine whether a fault current of the electrical fault is less than a threshold value. The at least one processor is further configured to direct the grid tie switch to close to electrically connect the microgrid to the electric grid and increase the fault current above the threshold value in response to determining that the fault current is less than the threshold value.