Bi-Directional Power Converter With Isolated Multi-Level DC-DC Stages
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Solution Overview
Problem
Existing DC fast chargers for electric vehicles require high-rated silicon carbide MOSFET switches due to wide voltage ranges, leading to increased switch requirements and current demands, which are not efficiently met by current technology.
Innovation Solution
A bi-directional power converter with an isolated DC-DC converter featuring a first stage converting DC to high frequency AC and a second stage capable of generating multi-level AC or DC voltages, using a high frequency transformer and symmetrical power conversion switches to optimize switch usage and voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high-rated silicon carbide MOSFET switches are used to handle wide voltage ranges, then the power converter can support various EV types, but the switch requirements and current demands increase significantly
Solution Approach 1:
The power converter is divided into two independent stages: a first stage handling DC to high frequency AC conversion, and a second stage handling high frequency AC to DC conversion. Each stage uses switches rated for specific voltage levels, avoiding the need for single high-rated switches to handle the entire voltage range. This segmentation allows each stage to be optimized independently for its voltage requirements.
Solution Approach 2:
A high frequency transformer is introduced as an intermediary between the first and second stages. The transformer provides voltage transformation and isolation, enabling the system to handle wide voltage ranges without requiring the switches in each stage to be rated for the maximum system voltage. The transformer acts as a mediator that decouples the voltage requirements of the input and output stages.
2Adaptability or versatility
If single stage power conversion is used, then device complexity is reduced, but the ability to handle wide voltage ranges without overloading switches is compromised
Solution Approach 1:
The power conversion process is segmented into two distinct stages with separate functional responsibilities. The first stage converts DC to high frequency AC using switches rated for DC bus voltage, while the second stage converts high frequency AC to DC using switches rated for output voltage. This segmentation enables wide voltage range handling while keeping each stage's switch requirements manageable.
Solution Approach 2:
The high frequency transformer serves as an intermediary that enables independent optimization of each stage. By placing the transformer between stages, each converter stage can be designed with switches appropriate for its specific voltage level, rather than requiring all switches to handle the full voltage range, thus managing complexity through functional decomposition.
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 bi-directional power converter efficiently handles a wide range of DC voltages without overloading switches, supporting various electric vehicle types and enabling bidirectional power transfer between vehicles and the grid.
Implementation Method 1
The intermediary stage 203 includes a high frequency transformer connected between the first stage 201 and the second stage 202
Data Source
AI summary
A bi-directional power converter, a control unit, a charging device and a method for transferring power between an EV and a power grid are provided. The bi-directional power converter includes an isolated DC-DC converter having a first stage converting a DC voltage into a high frequency AC voltage, a second stage capable of converting a high frequency AC voltage having an amplitude V2 into the DC voltage having an amplitude of V2 or 2V2, and converting the DC voltage into a multi-level high frequency AC voltage, and an intermediary stage electrically coupled to the first and the second stages, having a high frequency transformer of a turns ratio V1:V2.