Rotary Electric Machine Control for Fast Pole Angle Estimation

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Solution Overview

Problem

Existing sensorless magnetic pole position estimation methods for rotary electric machines face challenges in balancing response speed and switching frequency, with methods using dq-axis PID control offering slow response but low switching frequency, and those using UVW-axis providing faster response but increased switching frequency and noise.

Innovation Solution

A controller that generates a voltage command for estimation on a stationary coordinate system fixed to the winding, with a carrier wave of the same period, allowing direct estimation of rotational angle from current detection values, reducing switching frequency and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high-frequency voltage is applied for magnetic pole position estimation, then position estimation accuracy is improved, but noise increases

Engineering Contradiction:

Improvemagnetic pole position estimation accuracyVSAvoidnoise

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies periodic high-frequency voltage at a frequency equal to the carrier wave frequency, which creates a regular pattern that allows the control unit to distinguish the position estimation signal from noise through synchronous detection. The periodic nature at carrier frequency enables the system to extract position information while filtering out irregular noise components.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent converts the potentially harmful high-frequency noise into a useful position estimation signal by applying high-frequency voltage at the same frequency as the carrier wave. The control unit then uses this frequency-matched signal to estimate magnetic pole position, transforming what would normally be considered noise into beneficial position information.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Loss of energy

If dq-axis PID control is used for position estimation, then switching frequency is reduced, but position estimation response speed decreases

Engineering Contradiction:

Improveswitching lossVSAvoidposition estimation response speed

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The patent replaces the mechanical PID control loop with a direct frequency-based estimation method. Instead of using proportional-integral-derivative control to estimate position, the system directly calculates position from the amplitude of current responses to high-frequency voltage, eliminating the need for iterative PID calculations and significantly improving response speed while reducing switching operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses the current response waveform as a direct copy of the applied high-frequency voltage waveform, where the amplitude of the copied current signal directly indicates position information. This eliminates the need for complex PID control algorithms and allows immediate position estimation from the current measurement.

Inventive Principle:

Principle #26Copying

3Speed

If UVW-axis high-frequency voltage is used for position estimation, then position estimation response speed increases, but switching frequency increases

Engineering Contradiction:

Improveposition estimation response speedVSAvoidswitching loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent changes the frequency parameter of the applied voltage to match the carrier wave frequency exactly, rather than using arbitrary high frequencies. This specific frequency parameter choice allows the system to achieve fast response through direct frequency matching while minimizing switching losses by aligning with the existing carrier wave frequency used in PWM control.

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

The solution reduces switching loss and electromagnetic noise while maintaining fast position estimation, offering a trade-off between response speed and switching frequency.

Implementation Method 1

The superimposing high frequency method which estimates the magnetic pole position of the rotor using the saliency of the rotary electric machine

Methodology Applied

Scientific EffectSaliency:

Implementation Method 2

The induced voltage method which estimates the magnetic pole position of the rotor by estimating the induced voltage of the rotary electric machine

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12184206B2Controller for rotary electric machine

Publication Date: 2024.12.31 MITSUBISHI ELECTRIC CORP

AI summary

To provide a controller for rotary electric machine which can suppress the increase in the switching frequency by the voltage for estimation while reducing the estimation delay of the magnetic pole position (the rotational angle). A controller for rotary electric machine turns on and off switching devices which the inverter has and applies voltage to the winding, based on a comparison result between the voltage command and the carrier wave; generates the voltage command for estimation of a preliminarily set one period on a stationary coordinate system fixed to the winding; generates the carrier wave of the same one period as the one period of the voltage command for estimation; extracts the frequency component of the one period of the voltage command for estimation from the current detection value; and estimates a rotational angle based on the frequency component.