Voltage conversion system for transport refrigeration system
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Solution Overview
Problem
Designing an electrical system for transport refrigeration units that is efficient, lightweight, and compatible with different battery configurations is challenging due to high voltage and low power operation, as well as the wide battery voltage range.
Innovation Solution
A voltage conversion system with a non-coupled or weakly coupled inductor structure and multiphase boost stage, which includes coils with air gaps, allows for independent phase current shaping and reduced current ripple, enabling efficient DC-to-AC power conversion for transport refrigeration systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coupled inductor structure is used, then magnetic coupling between phases is achieved, but the system becomes heavier and more complex with increased current ripple
Solution Approach 1:
The inductor is segmented into multiple independent coils (first coil, second coil, third coil, fourth coil) with non-coupled or weakly coupled magnetic circuits. Each coil is wound around separate legs of the magnetic core, eliminating the need for strong magnetic coupling between phases while reducing current ripple through interleaved operation of the multiphase boost stage.
2Reliability
If the number of coils is increased to reduce current ripple, then current ripple decreases, but the physical size and complexity of the inductor increases
Solution Approach 1:
Multiple independent coils are merged into a single integrated inductor structure sharing a common magnetic core with multiple legs. The first and second coils are wound around first and second legs respectively, while the third and fourth coils are wound around third and fourth legs, creating a compact unified structure that reduces current ripple without proportionally increasing physical size.
Solution Approach 2:
The inductor utilizes a three-dimensional magnetic core structure with multiple legs extending in different spatial dimensions. This allows multiple coils to be arranged in a compact configuration where each coil occupies a separate spatial zone, reducing the overall footprint while accommodating the required number of coils for low current ripple.
3Manufacturing precision
If air gaps are added to external legs to provide inductance, then inductance control is improved, but manufacturing complexity increases
Solution Approach 1:
Air gaps are selectively introduced only in the external legs (first, second, third, and fourth legs) where inductance control is required, while the central leg maintains continuous magnetic flux path without air gaps. This localized application of air gaps provides precise inductance control for each coil while minimizing manufacturing complexity by limiting air gap fabrication to specific locations.
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 high power density, compact size, and flexibility to operate with different battery voltages, enhancing battery life and reducing physical space requirements.
Implementation Method 1
an inductor, the inductor comprising a number of coils that are non-coupled or weakly coupled, with a coupling coefficient less than 0.05
Implementation Method 2
each respective external leg of the plurality of external legs comprising an air gap
Data Source
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AI summary
Voltage conversion system including an energy storage device (24); a power conversion unit (26) connected to the energy storage device, the power conversion unit comprising: an inductor (210), the inductor comprising a number of coils (216) that are non-coupled or weakly coupled, with a coupling coefficient less than 0.05, a multiphase boost stage (220) coupled to the inductor, wherein the multiphase boost stage comprises a number of phases that equals the number of coils, and an inverter (230) coupled to the multiphase boost stage; and a load (22) coupled to the power conversion unit.