Power Inverter Switching Frequency Control for Electric Drives

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Solution Overview

Problem

There is a need to improve the efficiency of electric motor drives in automobiles by reducing power losses and noise in alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles, while maintaining effective control over the motor.

Innovation Solution

A method and system for controlling a power inverter in an electric drive system, where the switching frequency is set at a first frequency for commanded torques below a certain level and adjusted as a function of the commanded torque between two levels, while maintaining the frequency above a dynamic limit, reducing power loss and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the switching frequency of the power inverter is reduced to decrease power loss, then power loss is reduced and efficiency is improved, but motor control effectiveness deteriorates

Engineering Contradiction:

Improvepower lossVSAvoidmotor control effectiveness

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control system dynamically adapts the switching frequency based on operating conditions (torque levels), allowing the system to optimize between power loss reduction and control effectiveness in different operational scenarios.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of switching frequency based on torque levels. By adjusting this critical parameter according to operating conditions, the system achieves reduced power loss while maintaining adequate motor control effectiveness across different torque ranges.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the switching frequency of the power inverter is reduced to improve efficiency, then power loss decreases, but acoustic noise emissions increase

Engineering Contradiction:

Improvepower lossVSAvoidacoustic noise emissions

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The system dynamically adjusts switching frequency based on torque conditions, enabling the inverter to operate at lower frequencies (reducing power loss) only when torque is below the threshold, while maintaining higher frequencies when needed to control acoustic noise emissions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The switching frequency parameter is changed according to torque levels, allowing the system to optimize the balance between power loss and acoustic noise by operating at different frequency points in different torque ranges.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the switching frequency is set high to maintain effective motor control, then motor control effectiveness is maintained, but power loss increases

Engineering Contradiction:

Improvemotor control effectivenessVSAvoidpower loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent segments the torque operating range into different levels (above and below a threshold). For torque below the threshold, lower switching frequency is used to reduce power loss. This segmentation allows the system to apply different frequency strategies for different operational conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The switching frequency parameter is adjusted based on torque levels, changing from high frequency (when torque is high) to low frequency (when torque is low), thereby reducing power loss while maintaining control effectiveness in each torque range.

Inventive Principle:

Principle #35Parameter changes

4Loss of energy

If the switching frequency is set low to reduce power loss, then power loss decreases, but the switching frequency may fall below the dynamic frequency limit reducing control effectiveness

Engineering Contradiction:

Improvepower lossVSAvoidmotor control effectiveness

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The control system uses feedback by continuously monitoring torque levels and adjusting the switching frequency accordingly. This feedback mechanism ensures that the switching frequency remains above the dynamic frequency limit while still reducing power loss by operating at lower frequencies when conditions permit.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8165737B2Method and system for controlling a power inverter in electric drives of vehicles with two-mode transmissions

Publication Date: 2012.04.24 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

Methods and systems for controlling a power inverter in automobiles utilizing two-mode transmissions are provided. The various embodiments control the power inverter by, responsive to a commanded torque of the electric motor being below a first torque level, controlling the power inverter to set a switching frequency of the power inverter at a first set frequency; and, responsive to the commanded torque of the electric motor being between the first torque level and a second torque level, controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above a dynamic frequency limit. The method reduces switching frequencies in the inverter at high commanded torques, while maintaining the switching frequencies above dynamic frequency limit that provides effective control over the motor.