Sensorless AC Motor Control - solidThinking · 2018-03-28 · • Details drive setup • Open loop...

Sensorless AC Motor Control

solidThinking Embed

Prof. Dr. ir. D.W.J. Pulle

Isi Matalon

© 2018 solidThinking, Inc. Proprietary and Confidential. All rights reserved. An Altair Company.

Agenda

• Introduction

• Texas Instruments InstaSPIN™

• solidThinking Embed

• Open loop current & frequency control of an induction machine

• Encoderless field-oriented control of an induction machine


Prof. Dr. ir. D.W.J. Pulle

• University Guest Professor , RWTH-ISEA Aachen Germany,

• CEO EMsynergy Sydney Australia,

• Member of the Texas Instruments InstaSPIN™ development team

• Co-author of the Springer books:

• Fundamentals of Electrical Drives: A. Veltman, D. W. J. Pulle and R. De Doncker

• Advanced Electrical Drives: R. De Doncker, D. W. J. Pulle and A. Veltman

• Applied Control of Electrical Drives: D. W. J. Pulle, P. Darnell and A. Veltman


InstaSPIN™ Highlights

• Sensorless field oriented control

• Replace Mechanical encoders and resolver

• Motor Parameter Identification

• Field Weakening

• Increased efficiency at partial load

• Higher speeds

• Universally applicable

• FOC control of all AC machines: Induction, PM synchronous, IPM, Brushless DC as well as Synchronous Reluctance


From Motor Control Theory to Coding

• Memory restrictions

• Word size restrictions

• Full Control of the Microprocessor

• Debugging information not easily accessible

• Need to configure A/D, D/A, CAN, PWM, I2C, ….


Will it fit into memory? Will it be fast enough?

• Within 96% of the 3 phase sensorless FOC PMSM & Eight 100KHz parallel DC-DC buck converter control Texas Instruments algorithms

vs


Peripheral Support

ADC Config ePWM Config eQEP Config

Subsystem executed on

interrupt

128

pages…


TI Libraries

TI Digital Motor Control Library

TI MotorWare Library


Debugging in the real world

• Microcontroller Debugger & Oscilloscope

• solidThinking Embed Debug Interface (HIL)

• Plots

• Logging

• Inputs/Disturbances


Support & Learning Tools

• Learning Center with constantly expanding video library

• Partnered with field experts

• Models

• Videos

• Workshops

• Learning material

• Support and training sessions from Altair AEs globally

Embedded Code Generation for

AC motor drives

Design and generate C code for Embedded controllers using

solidThinking Embed

Application example: encoderless (sensorless) field-oriented control of a

three-phase induction machine using a real-time controller

Prof. Dr. ir. Duco W.J. Pulle


Agenda• Introduction

• Details induction machine used

• Details drive setup

• Open loop current & frequency control of an induction machine

• Operating principles

• Control implementation and generation of C code

• Results

• Encoderless field-oriented control of the induction machine

• Importance of correct orientation of the current vector, relative to the

rotor flux vector

• How to implement encoderless FOC control using the

Texas Instruments algorithm ‘FAST’

• Details of the implementation using solidThinking Embed

• Results

• Overview


Introduction

Details motor:

• Manufacturer: EMOD

• Nameplate data:

Interpretation of data:

• Star connected, 2 pole pair machine

• Peak phase voltage/current: 24 V/ 35 A

• Rated shaft torque/speed: 5 Nm/1425 RPM

• Rated stator flux: 78 mWb

• Rated stator frequency: 50 Hz

Measurements using an L-C-R meter ( via terminals):

• Stator resistance: 0.0555 Ohms

• Leakage inductance: 0.45 mH

Required data:

• Magnetizing current that produces rated stator flux: obtained via open loop current controlled drive operation

• Estimate for the rotor resistance, for now we assume: 𝑹𝑹 = 𝑹𝒔: actual value to be determined when operating field-oriented drive

Step 1: Operation of the machine with an open loop current controller:

• Operate drive at half rated stator frequency and determine current needed to achieve rated stator flux, which corresponds to voltage amplitude: 12. 2V (ignoring the resistance)


Drive setup : schematic representation showing MCU with converter and motor, ‘FAST’ prepared

+ DC Bus

C2000 MCU

Timers and

PWM

Compare

Units

Capture

Unit

ADC

Serial coms

(UART)Rx

Tx

SPI

Serial coms

PWM1PWM2PWM3PWM4PWM5PWM6

PWM1

PWM2

PWM3

PWM4

PWM5

PWM6

CAP/QEP

ADCIN0

SIMOSOMI

CLKSTE

Signal

Conditioning

Shunt

resistor

ADCIN1

ADCIN2

ADCIN3

ADCIN4

ADCIN5

ADCIN6

Introduction

Phase Voltage Meas

ADCIN4

ADCIN5

ADCIN6

ADCIN1ADCIN2

ADCIN3

Induction

machine

Note: ADC channels shown

here may not match those

actually in use DRV 8301-HC


Drive setup : actual hardware

• EMOD 0.75 kW, three-phase squirrel cage induction machine

• Texas Instruments DRV 8301-HC converter with F28069M control card

• 48V/4A DC power supply (not shown) connected to converter

• Laptop with solidThinking Embed installed and connected via USB cable to control board

Introduction


Open loop Current & Frequency control

Drive setup :

• Synchronous current controller, where we control the frequency and direct axis current reference values

• Converter PWM frequency set to 15 kHz, sampling frequency 15 kHz

• Machine operating no-load, so rotor flux in phase with current vector

• We have access to the per unit voltage vector

• We set drive operating at 25 Hz reference frequency and adjust 𝒊𝒅 ref until we reach the required voltage amplitude 12.2 V using :

𝒖𝒔 ≈ 𝒋𝝎𝒔𝑳𝝈Ԧ𝒊𝒔 + 𝒋𝝎𝒔𝝍𝑹 (ignoring the stator resistance)



Implementation in solidThinking Embed:

• ‘Open loop current controller’ module must be compiled to generate C code





• One level into ‘controller ’unit:






• One level into ‘Main motor control’ unit:







• One level into ‘current Controller’:



Implementation in solidThinking Embed :

• Running the generated C-code

• Measured current, using a DC current probe: 10A/div

Observations from experimental results:• Magnetizing current : 20A

• Peak voltage : 0.251x48= 12.07 V

• Rotor flux estimate: ൗ𝟏𝟐.𝟎𝟕(𝟐𝝅 𝟐𝟓)− 𝟐𝟎 𝑳𝝈 = 𝟔𝟕. 𝟖 𝐦𝐖𝐛

• Equivalent short circuit current: ൗ𝝍𝑹𝑳𝝈= 𝟏𝟓𝟎 𝐀

• Magnetizing inductance: 𝑳𝑴 = ൗ𝝍𝑹𝒊𝒅= 3.4 mH

per unit voltage: 𝒖𝜶

per unit current: 𝒊𝜶


Encoderless FOC control of an IM

Operating principles:• Current distribution due to the currents in the three phase windings is represented

by a vector Ԧ𝒊

• A 'rotating' flux, with speed 𝝎𝒔 is represented by the vector 𝝍• Rotor speed 𝝎𝒎 is not equal to flux vector speed 𝝎𝒔

• We need to control angle and amplitude of current vector relative to the flux vector

• Current component in 'd-axis' 𝒊𝒅, controls flux

• Current component in 'q-axis' 𝒊𝒒, controls torque

We must measure or estimate the angle, amplitude and speed of the flux vector relative to the stator in order to :

• Determine the required orientation of the vector Ԧ𝒊

• Estimate the shaft speed: 𝝎𝒎= 𝝎𝒔−𝒊𝒒𝑹𝑹

𝝍𝑹(for 2 pole IM)

Torque 𝑻𝒆 of the machine is given by:

• 'Out product' of two vectors 𝑻𝒆 =𝟑

𝟐𝝍× Ԧ𝒊 =

𝟑

𝟐𝛙 𝒊𝒒

• Two vectors must be stationary with respect to each other to maintain constant torque and constant flux

• Angle 𝚯 defines the orientation of the flux vector relative to the stationary 𝜶, 𝜷 plane

• Use of EMF vector 𝒆 = 𝐣𝝎𝒔𝝍 to find the vector 𝝍



Operating principles:• Use of Texas Instruments ‘FAST’ algorithm, which identifies the Flux amplitude 𝝍𝑹, Angle 𝜽, 𝐫𝐨𝐭𝐚𝐭𝐢𝐨𝐧𝐚𝐥 Speed 𝝎𝒔 of the flux

vector 𝝍𝑹 as well as the Torque

• FAST determines the EMF vector based on the measured voltage/currents and parameters 𝑳𝝈, 𝑹𝒔• Shaft speed variable 𝒇𝒎 requires knowledge of the rotor resistance value 𝑹𝑹• Use of synchronous current controller, to control the direct/quadrature reference values. Speed Controller controls the quadrature

current reference value

• Converter PWM frequency set to 15 kHz, sampling frequency 15 kHz




• ‘Drive controller with FAST’ module must be compiled to generate C code


















• One level into ‘Drive Controller’








• Modules present:

– FOC controller









– FOC controller

– FAST observer with stator resistance estimator









– FOC controller

– FAST observer with stator resistance estimator

– Speed controller



Implementation in solidThinking Embed :

• Running the generated C-code

• Measured current, using a DC current probe: 10A/div during no-load speed reversal from 750rpm → −𝟕𝟓𝟎 𝐫𝐩𝐦(𝐦𝐚𝐱 𝒊𝒒 𝐥𝐢𝐦𝐢𝐭𝐞𝐝

𝐭𝐨 𝟓𝐀)

Observations from experimental results:• Magnetizing current : 20A

• No-load operation under FOC speed control

• Max quadrature current limited due to power supply limits

per unit stator

current locus


Overview

• Understand what it takes to put together an

electrical drive system

• Use of solidThinking Embed greatly simplifies the process of drive development as it generates the required C code and uses an embedded approach that gives transparency to controller implementation

• Training courses available for industry to fast track development of any type of electrical drive. Contact Altair for more information or schedule an appointment

• solidThinking Embed examples given in this Webinar are freely accessible to customers

• Observe that implementing encoderless FOC control using FAST technology for electrical drive applications is effective

• ‘Question and Answer’ sessions on this Webinar will be used to answer any questions

Thank you for your attention

Thank you for your attention

For more information:

www.solidthinking.com

[email protected]

33

http://www.solidthinking.com/

mailto:[email protected]

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Sensorless AC Motor Control - solidThinking · 2018-03-28 · • Details drive setup • Open loop...

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