Motor Inverter Converter Layout to Avoid Torque During 400V Charging

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Solution Overview

Problem

800V-class battery electric vehicles require an interface converter to be compatible with 400V DC charging stations, which can introduce design complexity and unintentional torque when using motor windings as inductor coils and the inverter as a boost converter, especially when charging, leading to potential motor heating and loop current issues.

Innovation Solution

An automotive power system with a traction battery, inverter, switch bank, filter, and electric machine, featuring parallel pairs of series-connected power semiconductor devices with body diodes and additional parallel diodes, along with smaller inductors and current sensors, allowing for efficient 400V to 800V DC charging without using the electric machine windings, thus reducing complexity and heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If motor windings are used as inductor coils and inverter as boost converter for 400V to 800V charging, then charging functionality is achieved, but unintentional torque and motor heating occur

Engineering Contradiction:

Improvecharging functionalityVSAvoidunintentional torque and motor heating

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the charging function from the motor drive system by adding a dedicated DC-DC converter with separate inductors, isolating the motor windings from charging current paths. This prevents unintentional torque generation and motor heating during DC fast charging operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a dedicated DC-DC converter as an intermediary device between the traction battery and charging station, using separate inductors and power semiconductor switches. This mediator handles the voltage conversion for charging without involving the motor windings, eliminating the harmful effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If interface converter is added for 400V to 800V charging compatibility, then charging compatibility is improved, but device complexity increases

Engineering Contradiction:

Improvecharging compatibilityVSAvoidconverter complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent designs the DC-DC converter with a modular architecture that can handle both DC fast charging (400V to 800V conversion) and vehicle load management functions. The converter uses standard power semiconductor devices and control circuits that can be integrated with existing vehicle power management systems, reducing overall complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If smaller inductors are used in DC-DC converter, then loop current issues are prevented, but converter size increases

Engineering Contradiction:

Improveloop current preventionVSAvoidconverter volume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent segments the DC-DC converter into multiple independent phase legs, each with its own smaller inductor. This segmentation prevents large loop currents by distributing the current across multiple parallel paths, while the individual inductors remain compact. The modular structure allows efficient heat dissipation and reduces overall converter volume.

Inventive Principle:

Principle #1Segmentation

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 configuration enables seamless 400V to 800V charging, mitigates unintentional torque and motor heating, and balances current flow, reducing the number of semiconductor switches needed and preventing semiconductor switch overcurrent and loop current issues, while allowing for real-time circuit protection.

Implementation Method 1

A switch bank has a plurality of switches electrically connected between the traction battery and DC charge terminals. An inverter is electrically connected between the traction battery and switch bank, and includes (i) a plurality of pairs of series connected power semiconductor devices

Methodology Applied

Scientific EffectElectrical switching:

Implementation Method 2

each of the power semiconductor devices having a body diode in parallel therewith, and (ii) a plurality of diodes connected in parallel with the power semiconductor devices such that only one of the power semiconductor devices of each of the pairs has one of the diodes connected in parallel therewith

Methodology Applied

Scientific EffectDiode rectification: Diode

Implementation Method 3

a plurality of current sensors each configured to measure a current flow associated with one of the phase legs. The controller receives data from the current sensors and generates commands for the switches based on the data

Methodology Applied

Scientific EffectElectrical measurement:

Data Source

PatentUS11876467B1Motor inverter based converter for charging traction battery

Publication Date: 2024.01.16 FORD GLOBAL TECH LLC

AI summary

An inverter is electrically connected between a traction battery and a switch bank. The inverter includes a plurality of pairs of series connected power semiconductor devices. Each of the pairs is electrically connected in parallel with the traction battery to define a phase leg, and each of the power semiconductor devices has a body diode in parallel therewith. The inverter also includes a plurality of diodes connected in parallel with the power semiconductor devices such that only one of the power semiconductor devices of each of the pairs has one of the diodes connected in parallel therewith.