Interleaved Variable Voltage Converter for EV Power Drives
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Solution Overview
Problem
Existing high-power variable voltage converters (VVCs) in electric vehicles require large inductors and capacitors, leading to high volume, weight, cost, and loss, and are challenged by varying battery internal impedance affecting battery ripple current across temperature ranges.
Innovation Solution
A bi-directional variable voltage converter with a small air-gapped transformer and reduced inductance and capacitance, utilizing an air-gapped transformer with three cores and three windings, and specific winding configurations to maintain low battery ripple current regardless of internal impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large inductors and capacitors are used in high-power variable voltage converters, then power transfer capability is improved, but volume, weight, cost, and loss increase
Solution Approach 1:
The patent segments the single large inductor into two smaller inductors (L1 and L2) arranged in an interleaved configuration. This segmentation allows the converter to achieve the same power transfer capability while reducing the overall volume and weight of the magnetic components, as the two smaller inductors can be more efficiently packed and have lower total core losses compared to one large inductor.
Solution Approach 2:
The interleaved converter operates with periodic switching of the two phase legs, where each phase leg switches at a different time interval. This periodic alternating action allows the inductors to be smaller because the ripple current is divided between the two phases, reducing the required inductance value for each while maintaining the same overall power handling capability.
2Power
If large inductors and capacitors are used in high-power variable voltage converters, then power transfer capability is improved, but volume and packaging efficiency worsen
Solution Approach 1:
The magnetic components are segmented into two separate inductors with their own cores, allowing for more efficient spatial arrangement and reduced total volume. The interleaved structure enables better utilization of available space in the converter housing.
Solution Approach 2:
The patent combines the two phase legs and their associated inductors into a single integrated converter unit with shared capacitors and control circuitry. This merging reduces the overall volume by eliminating redundant components and improving packaging efficiency, while the interleaved structure allows the inductors to be positioned to minimize total volume.
3Power
If large inductors and capacitors are used in high-power variable voltage converters, then power transfer capability is improved, but manufacturing cost increases
Solution Approach 1:
Segmenting the converter into two phase legs with smaller, standardized inductor cores reduces manufacturing cost. The smaller inductors can be produced using more economical core materials and winding techniques compared to one large inductor, and the modular structure allows for easier assembly and testing.
4Power
If large inductors and capacitors are used in high-power variable voltage converters, then power transfer capability is improved, but energy loss increases
Solution Approach 1:
The interleaved periodic switching of the two phase legs reduces energy loss by distributing the power transfer across two alternating cycles. This reduces the peak current stress on each inductor and decreases core losses and copper losses, as each inductor only needs to handle half the total power at any given time.
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 proposed solution reduces inductance and capacitance requirements while maintaining low battery ripple current, minimizing weight and cost, and is robust against changes in battery internal impedance, improving the efficiency and packaging of electric drive systems.
Implementation Method 1
an air-gapped transformer with three windings and no more than four terminals... transfers power between the traction battery and electric machine inverter
Implementation Method 2
air-gapped transformer with three cores and three windings... A first of the windings is wound around only a first of the cores
Data Source
AI summary
A bi-directional variable voltage converter transfers power between a traction battery and an electric machine inverter. The bi-directional variable voltage converter includes a capacitor, two power module phase legs, and an air-gapped transformer with three windings and no more than four terminals. A first of the windings defines a first terminal and a second terminal of the no more than four terminals. The first terminal is directly electrically connected with a positive terminal of the traction battery and the second terminal is directly electrically connected with a positive terminal of the capacitor and a junction between the second and third windings. A second of the windings defines a third terminal of the no more than four terminals directly electrically connected with one of the power module phase legs. A third of the windings defines a fourth terminal of the no more than four terminals directly electrically connected with the other of the power module phase legs.