Inverter PWM Control for Electric Vehicle Torque and Temperature

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Solution Overview

Problem

Existing control devices for electric-powered vehicles with AC motors are ineffective in reducing total losses in inverters, particularly when considering both switching and on losses, leading to overheating and inefficiencies during low motor rotation and slope climbing conditions.

Innovation Solution

A control device with a signal producing unit and control unit that employs pulse width modulation (PWM) to variably control the central value of the modulated wave based on switching frequency and motor rotation, incorporating current and temperature sensing to balance losses and prevent current concentration, thereby reducing inverter losses and overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If AC motor operates at extremely low rotation number during slope climbing, then vehicle can maintain position against gravity, but current concentrates in specific phase causing inverter overheating

Engineering Contradiction:

Improvemotor torqueVSAvoidinverter temperature

Core Design Contradiction:

ForceVSTemperature

Solution Approach 1:

The invention changes the parameter of the modulated wave's central value to redistribute current among the three phases of the inverter. By shifting the central value from 0.5 to values closer to 0 or 1, the system alters the PWM duty cycles in a way that prevents current concentration in any single phase. This parameter modification ensures more balanced current distribution while maintaining the required motor torque for slope climbing, thereby preventing inverter overheating.

Inventive Principle:

Principle #35Parameter changes

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

Effectively reduces inverter losses by minimizing on losses and switching losses, preventing overheating and damage by optimizing PWM control during low motor rotation and slope climbing conditions.

Implementation Method 1

a signal producing unit producing a signal for turning on/off a switching element of the inverter based on a pulse width modulation method

Methodology Applied

Scientific EffectPulse Width Modulation:

Data Source

PatentEP2114005B1Device for controlling electric vehicle and electric vehicle equipped with the control device, and electric vehicle control method and computer readable recording medium on which program for allowing computer to execute the control method is recorded

Publication Date: 2019.05.15 TOYOTA JIDOSHA KK

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AI summary

A carrier frequency setting unit (64) sets a carrier frequency (FC) based on a torque command (TR) and a motor rotation number (MRN) of a motor generator. A PWM signal producing unit (68) produces phase modulated waves corresponding to respective phase voltage commands (Vu, Vv and Vw), and produces respective phase PWM signals (Pu, Pv and Pw) corresponding to a relationship in magnitude between the respective phase modulated waves and a carrier having the carrier frequency (FC). A PWM center control unit (66) produces a PWM center correction value (ΔCE) for variably controlling the PWM center when the carrier frequency (FC) is lower than a predetermined frequency, and provides the same to the PWM signal producing unit (68).