Two-Level Voltage Converter Precharging for Electric Vehicle Cables
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Solution Overview
Problem
Conventional electric vehicle charging cables have limited precharging power due to space, cost, and weight constraints, which is insufficient for charging at all conventional charging columns, especially when dealing with high-voltage batteries like the 800-volt system in electric vehicles.
Innovation Solution
The use of a two-level voltage converter system that transforms charging voltage to an intermediate voltage, allowing the charging cable to be precharged using existing components, eliminating the need for a separate precharging circuit and enabling higher power precharging by connecting the charging cable to an intermediate circuit, which can be adjusted based on charging column voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a separate precharging circuit is used, then the charging cable can be precharged, but the precharging power is limited due to space, cost, and weight constraints
Solution Approach 1:
The precharging function is merged with the existing intermediate circuit of the two-level voltage converter. The intermediate circuit, which already exists for converting high voltage to low voltage, is now also used to precharge the charging cable by connecting it to the intermediate circuit terminal. This eliminates the need for a separate precharging circuit and provides sufficient precharging power for all charging columns.
Solution Approach 2:
The intermediate circuit is given multiple functions: it continues to perform its original role of transforming high voltage to low voltage for the low-voltage battery, and simultaneously serves as a precharging circuit for the charging cable. This multi-functionality increases precharging power without adding separate components.
2Power
If the intermediate circuit is used for precharging, then precharging power is significantly increased, but current reverse flow must be prevented
Solution Approach 1:
A diode is introduced as an intermediary component between the intermediate circuit and the charging cable. The diode allows current to flow from the intermediate circuit to precharge the charging cable, but blocks any reverse current flow from the charging cable back into the intermediate circuit and voltage converters, ensuring system reliability.
Solution Approach 2:
The precharging function is extracted from the main charging path through the voltage converters and placed directly at the intermediate circuit. This separation allows the precharging operation to occur independently without affecting the main charging conversion path, and the diode ensures no interference or reverse flow between the two functions.
3Adaptability or versatility
If a unidirectional voltage converter is used for 800V to 400V conversion, then the high-voltage battery can be charged at 400V charging columns, but the charging cable cannot be directly connected to the high-voltage battery for precharging
Solution Approach 1:
The two-level voltage converter's intermediate circuit serves itself by providing precharging capability. Instead of requiring an external or separate precharging circuit, the intermediate circuit uses its own capacity and components to precharge the charging cable, making the system self-sufficient for both voltage conversion and precharging functions.
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 solution allows for reliable precharging and charging of electric vehicles with significantly higher power, preventing reverse current flow and enabling flexible adjustment to different charging voltages, thus overcoming the limitations of conventional precharging systems.
Implementation Method 1
A first voltage converter transforms a charging voltage that is applied to a charging cable to a high voltage for a high-voltage battery
Implementation Method 2
a second, in particular two-level, voltage converter to charge a low-voltage battery and to transform the high voltage to a low voltage for the low-voltage battery. The second voltage converter transforms the high voltage for an intermediate circuit to an intermediate voltage and transforms the intermediate voltage to the low voltage
Implementation Method 3
The intermediate circuit is designed to precharge the charging cable using the intermediate voltage before the beginning of a charging process
Implementation Method 4
A flow of current from the charging cable to the intermediate circuit is prevented, in particular, by a diode
Data Source
AI summary
A method and an apparatus (100) use a charging cable (108) for charging an electric vehicle. The apparatus has a first voltage converter (110) to transform a charging voltage applied to the charging cable (108) to a high voltage for a high-voltage battery (104) of the electric vehicle. The apparatus (100) also has a second two-level voltage converter (112) to charge a low-voltage battery (106) of the electric vehicle by transforming the high voltage to an intermediate voltage for an intermediate circuit (118) and transforming the intermediate voltage to a low voltage for the low-voltage battery (106). The intermediate circuit (118) is designed to precharge the charging cable (108) using the intermediate voltage before the beginning of a charging process.