Medium-to-high voltage power system for a transport refrigeration unit
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Solution Overview
Problem
Existing transport refrigeration units rely on unregulated AC power sources that vary in voltage and frequency, necessitating an all-electric solution for providing stable AC and DC power to various loads.
Innovation Solution
A high-voltage direct current (HVDC) system with converters, including DC-DC buck and boost converters, is implemented to manage power distribution to compressors, evaporators, and condensers, ensuring stable voltage levels for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unregulated AC power sources are used to drive compressor and fans, then the system can operate with simpler power supply components, but the voltage and frequency variations reduce system reliability and efficiency
Solution Approach 1:
The patent transforms the power supply from unregulated AC to regulated HVDC by changing the electrical parameters (voltage level, current type, and stability characteristics). This parameter transformation resolves the contradiction by providing stable, reliable power while enabling efficient motor control through DC-DC and DC-AC conversion stages.
Solution Approach 2:
The patent replaces traditional AC power generation systems with an all-electric HVDC architecture using battery or capacitor-based energy storage. This substitution eliminates the need for mechanical generators and associated regulation equipment, achieving both simplicity and reliability through electronic power management.
2Productivity
If conventional AC power distribution is used for all loads, then the system architecture remains simple, but efficiency is reduced due to unregulated voltage and frequency variations
Solution Approach 1:
The patent segments the power distribution system into distinct DC and AC domains, with DC power supplied to DC motors (compressor, condenser fans) and AC power generated on-demand for AC loads (evaporator fans). This segmentation enables each subsystem to operate at optimal efficiency while maintaining manageable architectural complexity through modular power conversion units.
3Reliability
If voltage regulation is implemented for all power loads, then power quality and efficiency improve, but the system complexity and cost increase
Solution Approach 1:
The patent applies voltage regulation locally at each power conversion stage (DC-DC buck/boost converters for DC loads, DC-AC inverters for AC loads) rather than attempting centralized AC regulation. This local quality approach ensures voltage stability for each specific load type while keeping individual converter circuits relatively simple and manageable.
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
The system provides stable AC and DC power to transport refrigeration units, enhancing efficiency and reliability by regulating voltage levels across different loads.
Implementation Method 1
a first converter coupling the HVDC source to a distribution bus, wherein the distribution bus is coupled to a compressor, at least one condenser, and an at least one evaporator
Implementation Method 2
a compressor bus that comprises a DC motor that is mechanically coupled to an open drive compressor
Implementation Method 3
an evaporator bus that comprises a DC-DC boost converter coupled to a DC-AC converter to convert voltage from the distribution bus for the at least one evaporator
Data Source
AI summary
A high-voltage system for a transport refrigeration unit (TRU) includes a high-voltage direct current (HVDC) source, and a first converter coupling the HVDC source to a distribution bus, the distribution bus is coupled to a compressor, at least one condenser, and at least one evaporator. A distribution bus is coupled to a compressor bus coupled to the compressor, a condenser bus coupled to the at least one condenser, and an evaporator bus coupled to the at least one evaporator.