Isolated Bidirectional DC-DC Converter for Wide EV Voltage Range
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Solution Overview
Problem
Conventional DC fast chargers for Electric Vehicles (EVs) face challenges in providing a wide range of DC output voltages efficiently, requiring high-rated switches and increasing current ratings, which complicates the design and operation for varying EV battery voltages from 150V to 1500V.
Innovation Solution
A bi-directional power converter with an isolated DC-DC converter structure, comprising a first stage for high frequency AC conversion, a second stage capable of power conversion or power inversion modes, and an intermediary high frequency transformer, along with capacitors and switches, dynamically controls DC voltage between V2 and 2V2, optimizing switch requirements and voltage delivery across the range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional DC fast chargers use high-rated switches to deliver high power, then power delivery capability is improved, but device complexity and cost increase
Solution Approach 1:
The power converter is divided into multiple stages (first stage converter, second stage converter, and DC-DC converter) with each stage handling specific voltage and power conversion tasks. This segmentation allows each component to operate at optimized voltage levels, reducing the need for high-rated switches throughout the entire system.
Solution Approach 2:
The patent introduces an intermediary voltage level (V1) between the input voltage (Vin) and output voltage (Vout), creating a multi-level voltage architecture. This dimensional approach to voltage management enables power delivery without requiring single-stage high-voltage switches, thereby reducing device complexity.
2Adaptability or versatility
If DC output voltage range is extended from 150V to 1500V to support various EVs, then adaptability is improved, but switch current ratings and device complexity increase
Solution Approach 1:
The DC-DC converter stage dynamically adjusts the output voltage within the range of V2 to 2V2 based on the connected EV's battery voltage requirements. This dynamic adjustment capability allows the system to adapt to different EV types without requiring hardware changes or increasing overall device complexity.
Solution Approach 2:
The multi-stage converter architecture serves multiple functions: the first stage converts Vin to V1, the second stage converts V1 to V2, and the DC-DC converter adjusts V2 to the final output voltage. This universal design handles the entire voltage range from 150V to 1500V through coordinated operation of all stages, rather than requiring different hardware configurations.
3Device complexity
If single-stage high voltage conversion is used, then device complexity is reduced, but power delivery efficiency decreases
Solution Approach 1:
The conversion process is segmented into multiple stages, each operating at optimized voltage and power levels. This segmentation reduces energy losses in each individual stage compared to a single high-voltage stage, improving overall power delivery efficiency while maintaining manageable device complexity.
Solution Approach 2:
The patent introduces intermediary voltage levels (V1 and V2) that act as mediators between the input and output voltages. These intermediary stages enable efficient power transfer by avoiding direct high-voltage conversion, thereby reducing energy losses without significantly increasing device complexity.
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 delivers a wide range of DC voltages, optimizing the number of switches and current ratings, enabling efficient charging and energy transfer between EVs and the power grid, supporting both G2V and V2G charging applications.
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, having four power conversion switches and capacitors, capable of converting a high frequency AC voltage having an amplitude V2 into the DC voltage having an amplitude of V2 or 2V2 in a power conversion mode, and converting the DC voltage into a multi-level high frequency AC voltage in a power inversion mode, and an intermediary stage) electrically coupled to the first and the second stages, having a high frequency transformer of a turns ratio V1:V2.