Inverter Step-Up Conversion for 800V Battery Charging
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Solution Overview
Problem
Existing fast DC charging stations for electric vehicles typically operate at 400 volts, making it difficult to charge vehicles equipped with 800-volt high-power systems, as they require expensive and space-consuming DC/DC converters for voltage conversion, which also increase vehicle weight and reduce range.
Innovation Solution
The method utilizes the vehicle's drive inverter and electrical machine to perform a step-up conversion, allowing the 800-volt battery to be charged at conventional 400-volt charging stations without additional electronics, by connecting the charging station to the star point of the electrical machine and using the inverter's switches to establish a suitable voltage through clocked operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a dedicated DC/DC converter is used to convert charging voltage from 400V to 800V, then voltage conversion is achieved, but the converter is expensive and occupies large installation space
Solution Approach 1:
The drive inverter, originally designed for motor control, is made multi-functional by enabling it to also perform DC/DC voltage conversion during charging operations. The inverter uses its existing IGBT modules and phase inductors to function as a boost converter, converting 400V charging voltage to 800V battery voltage without requiring a separate dedicated DC/DC converter.
Solution Approach 2:
The patent merges the function of voltage conversion with the existing drive inverter system. By combining the charging function and voltage conversion function into a single integrated system using the inverter's components (IGBTs, phase inductors, star point connection), it eliminates the need for separate conversion hardware.
2Adaptability or versatility
If a dedicated DC/DC converter is used for voltage conversion, then charging compatibility is achieved, but the vehicle weight increases significantly
Solution Approach 1:
The drive inverter is designed to perform multiple functions: motor control during operation and DC/DC voltage conversion during charging. This multi-functionality eliminates the need for additional weight-bearing components while maintaining charging compatibility across different voltage standards.
Solution Approach 2:
The vehicle's existing inverter system serves itself by performing the voltage conversion function that would otherwise require separate dedicated equipment. The inverter uses its own internal components (phase inductors, switching elements) to convert voltages, making the system self-sufficient and avoiding additional weight.
3Device complexity
If the drive inverter is used for voltage conversion by connecting to the star point, then additional electronics are eliminated, but voltage synchronization according to IEC 61851 cannot be performed
Solution Approach 1:
Instead of connecting both poles of the charging station directly to the battery as per standard procedure, the patent inverts the connection topology by connecting one pole to the star point of the electrical machine and using the phase inductor as the conversion element. This unconventional connection enables voltage conversion while maintaining synchronization capability.
Solution Approach 2:
The system implements voltage synchronization through feedback control by measuring the battery voltage and adjusting the switching duty cycle of the inverter's IGBT modules accordingly. This closed-loop control ensures that the converted voltage matches the battery's required voltage level within tolerance, complying with IEC 61851 standards.
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 standardized charging compatible with IEC 61851 standards, reduces the need for additional electronics, and minimizes weight and space while allowing 800-volt batteries to be charged at any charging station, thereby improving user convenience and vehicle efficiency.
Implementation Method 1
the conversion is performed by means of the phase inductor of the electrical machine (from phase to star point)
Implementation Method 2
the phase inductance of the electrical machine and by suitably driving the semiconductor elements of the drive inverter
Data Source
AI summary
A method for charging a battery of an electric vehicle, at a direct-current charging apparatus, wherein the vehicle has an inverter which is connected to the battery, and an electric motor which is connected to the inverter. During the charging process, the inverter and at least one inductor of the electric motor are used for the step-up conversion of a low charging voltage of the direct-current charging apparatus into a higher voltage which is required for charging the battery.