Coupled Inductive Elements for EV Power Converter
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Solution Overview
Problem
Existing electrical vehicle converters face challenges with high costs, volume, weight, and efficiency due to the use of silicon switches and inductive elements, particularly at low loads where ZVS methods generate unacceptable power losses and require materials that saturate easily, limiting the use of high-saturation materials like Fe-Si-based ones.
Innovation Solution
The electrical circuit couples inductive elements to form a magnetic circuit that can be alternately controlled in common or differential modes, reducing flux inversions and allowing the use of high-saturation materials like Fe-Si-based ones, thereby minimizing power losses and reducing the volume of magnetic materials needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ZVS method is used in critical mode to reduce power losses, then efficiency is improved, but current inversions become excessive (>100% of peak current) causing unacceptable power losses in inductive elements
Solution Approach 1:
The patent divides the single inductive element into multiple coupled inductive elements (first and second inductive elements). Each inductive element handles a portion of the current inversion, reducing the inversion amplitude in each individual element while maintaining the overall ZVS critical mode operation. This segmentation allows current inversions to be distributed and controlled within acceptable limits.
Solution Approach 2:
The patent combines multiple inductive elements into a coupled system where they work together to achieve the desired current inversion. By coupling the inductive elements appropriately, the system achieves ZVS critical mode operation with reduced current inversion amplitude in each element, as the combined effect distributes the stress across multiple components.
2Ease of operation
If conventional inductive elements are used with ZVS critical mode, then current inversion is achieved, but magnetic material volume and weight increase due to high saturation requirements
Solution Approach 1:
The patent segments the magnetic circuit into multiple coupled inductive elements, each with smaller magnetic core requirements. By dividing the overall function across multiple elements, each element can use less magnetic material while the coupled system achieves the necessary current inversion capability.
Solution Approach 2:
The patent changes the operating parameters by using coupled inductive elements with specific coupling coefficients. This allows the system to achieve ZVS critical mode operation with reduced current inversion amplitude in each element, enabling the use of magnetic materials with lower saturation thresholds and reducing overall magnetic material volume.
3Loss of energy
If high-saturation materials like Fe-Si are used, then power losses are reduced, but the converter volume and weight increase
Solution Approach 1:
The patent uses multiple coupled inductive elements instead of a single large inductor. This segmentation allows the use of smaller magnetic cores with potentially lower saturation materials, as each element handles a portion of the magnetic flux. The coupled system achieves the necessary performance without requiring high-saturation materials in large volumes.
Solution Approach 2:
The patent changes the magnetic circuit parameters by introducing coupled inductive elements with specific inductance values and coupling coefficients. This allows the system to operate with reduced flux density in each element, enabling the use of magnetic materials with lower saturation thresholds and reducing overall converter volume.
4Power
If multiple cells are used to handle high power (20-1000 kW), then power capacity is improved, but cost and complexity increase due to quantity of silicon switches required
Solution Approach 1:
The patent combines multiple inductive elements into a coupled system that can be integrated with the multi-cell converter architecture. This coupling reduces the overall complexity by sharing magnetic components across cells, potentially reducing the total number of discrete inductive elements and associated switches required for high power operation.
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
This approach enables the use of ZVS in critical mode with reduced power losses and lower magnetic material volumes, enhancing efficiency and reducing the size of converters while maintaining high current inversions, suitable for high-frequency operations.
Implementation Method 1
inductive elements connected to transistors managing the current flowing in the said inductive elements
Implementation Method 2
the inductive elements are coupled so that they form a magnetic circuit that can be alternately controlled
Data Source
AI summary
An electrical circuit for supplying electrical propulsion power on board a motor vehicle is disclosed. The electrical power is obtained from power delivered to the electrical circuit by a battery of the vehicle and converted by at least two cells. The circuit includes inductive elements connected to transistors for managing the current flowing in the inductive elements, and the inductive elements are coupled to form a magnetic circuit. The magnetic circuit is alternatively controlled according to a common mode in which an apparent inductance of the said magnetic circuit is of the order of magnitude of the sum of the inductances specific to each inductive element, or according to a differential mode in which the apparent inductance of the said magnetic circuit is of the order of magnitude of the leakage inductance of the coupling between the said coupled inductive elements.