Grid shield
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Solution Overview
Problem
Transportation refrigeration units (TRUs) used in ship-based cargo transportation face shutdowns due to unbalanced or lost phases in three-phase grid power, leading to potential cargo losses, as existing systems lack the ability to detect and mitigate these issues.
Innovation Solution
A grid-shielded electrical system with a three-phase bus, voltage sensors to detect unbalanced phases and phase losses, and a controller to automatically shut down and restart electrical components, ensuring continuous operation by monitoring voltage and current readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TRU operates in standby mode with grid power on ship, then power is provided without diesel operation, but unbalanced phases or phase loss causes shutdown and cargo loss
Solution Approach 1:
The voltage sensor continuously monitors the grid power phases before a shutdown occurs. When unbalanced phases or phase loss is detected, the controller preemptively activates the backup power source or takes protective actions to prevent cargo loss, rather than waiting for the shutdown to occur.
Solution Approach 2:
The system implements continuous feedback monitoring of grid power quality through voltage sensors on each phase. The controller receives real-time voltage readings and adjusts operations accordingly, shutting down only when necessary and automatically restarting when power quality is restored, thereby maintaining reliability despite grid instability.
2Measurement precision
If voltage sensor monitors each phase of three-phase bus, then root cause issues are detected, but device complexity increases
Solution Approach 1:
The voltage sensor is designed to perform multiple functions: monitoring voltage levels, detecting phase balance, identifying phase loss conditions, and providing data for controller decision-making. This multi-functionality reduces the need for separate sensors for each detection task, thereby limiting the increase in device complexity while maintaining high measurement precision.
Data Source
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AI summary
A grid-shielded electrical system (101) for a transportation refrigeration system is provided. The grid-shielded electrical system (101) includes a bus (110) to deliver three-phase grid power, which is received from a grid (310), to electrical components (112) of the transportation refrigeration system, a voltage sensor (120) disposed to sense a condition of voltage on the bus (110) and configured to generate voltage readings accordingly and a controller (140) disposed in signal communication with the voltage sensor (120) and configured to detect a root cause issue with the grid (310) based on the voltage readings.