DC Link Converter Control to Prevent Refrigeration Load Shutdowns
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Solution Overview
Problem
The DC link in transport refrigeration systems experiences voltage fluctuations, leading to unintended shutdowns of mechanical loads, which can result in spoilage of cargo intended to be heated or cooled.
Innovation Solution
A system comprising a power converter that monitors the DC link voltage and adjusts power supply or draw based on an operating voltage setpoint, using proportional and integral control terms to stabilize the voltage, and load controllers that reduce power consumption when the voltage falls below a setpoint to prevent fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DC link voltage is monitored and power is dynamically adjusted based on voltage deviations, then voltage stability is improved and shutdowns are prevented, but the system complexity increases due to additional control mechanisms
Solution Approach 1:
The power converter continuously monitors the DC link voltage and adjusts its power output based on the voltage deviation from a reference value. This closed-loop feedback control ensures voltage stability by dynamically compensating for load variations, preventing shutdowns while maintaining system reliability without requiring overly complex control architecture.
Solution Approach 2:
The system uses the power converter's inherent control capabilities to stabilize the DC link voltage. The power converter serves dual functions: its primary power conversion role and its secondary role as a voltage stabilizer through active power adjustment. This self-service approach eliminates the need for separate voltage stabilization equipment, reducing overall system complexity.
2Reliability
If the power converter actively stabilizes the DC link voltage, then shutdowns are prevented and cargo spoilage is avoided, but the energy consumption of the power converter increases
Solution Approach 1:
The system changes the operating parameters of the power converter dynamically based on DC link voltage conditions. When voltage deviations occur, the power converter adjusts its output power and operating point to restore voltage stability. This parameter adaptation allows the system to maintain reliability during critical events while minimizing unnecessary energy consumption during normal operation.
Solution Approach 2:
The power converter applies active voltage stabilization only when necessary, based on the magnitude of voltage deviations. The control system monitors voltage levels and activates corrective power adjustments only when voltage exceeds predefined thresholds, rather than continuously operating at maximum stabilization effort. This partial action approach prevents excessive energy consumption while ensuring reliability when needed.
Data Source
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AI summary
The present disclosure relates to a system 200 for stabilising a DC link 230 that supplies power to a load 242, 244. The system 200 comprises a power converter 220 electrically coupled to the DC link 230. The power converter 220 is configured to: supply 452 power to or draw 454 power from the DC link; monitor 410 a voltage of the DC link 230; and control 405 the power supplied to, or drawn from, the DC link 230 based on the monitored voltage of the DC link 230 and an operating voltage setpoint.