srm

Smooth transition between optimal control modes in

SWITCH RELUCTANCE MOTOR

By- Badal Patnaik - 1001227260Sanjit Debta - 1001227317D. Gouri Sankar - 1001227269Debendra Kido - 1001227267Ananya Subhadarsinee - 1001227255

Content

• Introduction

• Principle of operation

• Characteristics

• General control strategy

• Modes of operation

• Simulink model for proposed controller

• Simulation results and Analysis

• Conclusion

• References

Introduction

• Concept of SRM-1938

• Practical realization-mid 1960s,after the evolution of power electronics & computer aided EM design

• Also known as : -Variable Reluctance Motor -Brushless Reluctance Motor -Commutated Reluctance Motor

Construction

It’s a doubly-salient, singly-excited, independent stator

exited motor

The stator is same as PM motor but the rotor is

simpler having no permanent magnet

Stator windings on diametrically opposite poles

are connected in series or parallel to form one phase

Construction

• 6/4,8/4,10/6,12/6,4/2,2/2 etc

configurations are possible, but 6/4 &

8/4 are most common

• Higher the no. of stator/rotor pole

combination, higher the no. of phase

which aide to torque ripple reduction

Content

• Introduction


• Characteristics





• Conclusion

• References

Principle of Operation

Principle of Operation

• Inductance of stator phase winding varies with rotor

position

• Torque is produced only during variation of inductance

• Current is made available only during this variation, hence

the need for rotor position feed back sensor

Periodic change of inductance with Rotor position

Rotor

Unaligned Position

Lu

La

Inductance Profile

Stator

Aligned PositionRotor

θ1 θ3θ2 θ4θ

L

Content

• Introduction


• Characteristics





• Conclusion

• References

Characteristics of SRM

All these characteristics cannot be obtained at a

single operating point.

HENCE THE NEED OF OPTIMAL CONTROL STRATEGY

Content

• Introduction


• Characteristics





• Conclusion

• References

General Control Strategies

Voltage Source control

Hysteresis current control

Voltage Source control

Both transistors are switched on at θ0and both are switched off at θcConducts through D2 and D1 when negative voltage is applied between θc and θq

Voltage control waveforms

V

Voltage source Control

Converter6/4SRM

V

ω

SRM with voltage source controller


• Power switches are switched off or on according to the current is

greater than or less than a reference current.

• The instantaneous phase current is measured and fed back to

summing junction.

• The error is used directly to control the states of power

transistors.

SRM with hysteresis current controller

iref

Hysteresis CurrentController

Converter6/4

SRM

V

i

i

Content

• Introduction


• Characteristics





• Conclusion

• References

Modes of operation

Single pulse mode

PWM mode

Optimum Performance in Single Pulse modeL, Ψ

La

L

Lu

Ψc

Ψ

θθuθaθqθcθ1

θu

θ0

θ01

θ

βsβr

αp

θqθcθ1

θu

θ0

θe1 θe2

-Vdc

Vdc

Optimum turn-on & turn-off angle in single Pulse mode

11 e

opt

o c

11 1 e

opt

c c

Optimum Performance in PWM mode

La

Lu

L

θ

θ

θ1θu

θ01

i

θ0 θc θq

θe

θa

Vdc

iref

Ψc

-Vdc

θu

βs

βr

αp

Optimum turn-on & turn-off angle in PWM mode

dc

refu

V

iL 10

e

esk

opt

c

01

1 12

Content

• Introduction


• Characteristics





• Conclusion

• References

Simulation block diagram with basic controller

Simulation block diagram with developed controller

Turn-off angle (deg)

Turn-on angle (deg)

powergui

Discrete ,Ts = 1e-006 s.

peak value

max

peak flux max

Vdc

240

Unaligned ind

-C-

To Workspace2

offangle

To Workspace1

onangle

To Workspace

t

Theta e 1

Theta e

Theta 1

52 .5

Theta 01

Switched Reluctance

Motor

TL

m

A1

A2

B1

B2

C1

C2

A1

A2

B1

B2

C1

C2

TL

m

Switch 2

Switch 1

Subsystem-4

Theta 1

Theta e1

sp-off

Subsystem-3

Theta 1

Theta e1

sp-on

Subsystem-2

Theta 1

Theta 01

Theta e

pwm-off

Subsystem-1

Theta 1

Theta 01

pwm-on

Scope 1

Ref speed

Sig

na

l 4

Ref flux

|u|

Position _Sensor

w

alfa

beta

sig

Load torque

Signal 2

-K-

Flux Control

PID

Eqn -3

1/u

Current control

PI

Clock

CONVERTER

G

V+

V-

A1

A2

B1

B2

C1

C2

Base speed 325

Abstract

|u|

240 V

<Flux (V*s)><Flux (V*s)><Flux (V*s)><Flux (V*s)><Flux (V*s)><Flux (V*s)>

<w (rad/s)>

<w (rad/s)>

<I (A)><I (A)>

<Te (N*m)>

Block diagram of subsystems

• subsystem-1 • subsystem-1

1

pwm-onsum

2

Theta 01

1

Theta 1

pwm -off

1

stroke angle

60

constant

1

Subtract 2Subtract 1

Product 2

Product 1

Inv theta e 2

1/u

Theta e

3

Theta 01

2

Theta 1

1

Block diagram of subsystems

• subsystem-3 • subsystem-4

1

sp-on

0.25

c-lambda

Pre-eqn

Eqn-sp-on

2

Theta e1

1

Theta 1

1

sp-off

Product0.75

1-c lambda

2

Theta e1

1

Theta 1

Parameters of the 6/4 SRM

• Voltage = 240V dc, • Current = 450A max, • Rating of the SRM = 60 kw• No. of phases = 3 • No. of stator poles =6• No. of stator poles =4• Rotor pole pitch = 90 deg• Stator pole arc = 36.00 deg• Rotor pole arc = 38.50 deg

• Rotor position at which stator and rotor pole corners starts overlap =52.50 deg

• Aligned inductance =23.6x10-03 H

• Unaligned inductance=0.67x10-03 H

• Max flux linkage=0.486 V.s• Stator resistance=0.05 ohm• Inertia=0.05 Kg.m.m• Friction=0.02 N.m.s• Base speed = 3100 rpm

Content

• Introduction


• Characteristics





• Conclusion

• References

Simulation Results and

Analysis

At No-Load with basic controller

At No-Load with developed controller

At No-Load with developed controller while crossing base speed

At No-Load : turn-on angle

Tu

rn

on

an

gle

(d

eg

)

Time (sec)

At No-Load : turn-off angle

Analysis of simulation results on No-load

Type of controller

at steady state rpm

0f 6560

PWM mode Single pulse mode

Turn-on

(degree)

Turn-off

(degree)

Current

ripple

(Amps)

Torque

ripple

(Nm)

Turn-on

(degree)

Turn-off

(degree)

Current ripple

(steady state)

(Amps)

Torque ripple

(steady state)

(Nm)

Basic 45 75 0 to 200

(200)

36 to 148

(112)

45 75 0 to 30.5 (30.5) 10 to 18

(8)

Developed 52.5 to

52.3

104 to 81 0 to 230

(230)

30 to 100

(70)

45.2 72 to 75 0 to 30

(30)

10 to 17.5

(7.5)

Analysis on No-load

• The developed controller operates with varied turn-on and turn-of angles.

• The torque ripple is reduced in both PWM and single pulse mode when the SRM is used with the developed controller.

• This is one aspect of the optimal performance of the SRM with the developed controller.

• While operating at steady state in single pulse mode, the maximum current/current ripple is less when the SRM is used with the developed controller.

• The transition is smooth in terms of flux, current, torque or speed when the motor shifts its operation from PWM mode to single pulse mode.

• SRM delivers better performance when used with a controller having varied turn-on and turn-off angles

• The turn-on and turn-off angles are varied at every instant in synchronization with the formulae for optimal condition.

With heavy Load of 80 Nm

At 80 Nm Load: turn-on angle

Tu

rn

on

an

gle

(de

g)

Time (sec)

0 1 2 3 4 5 6 7 830

35

40

45

50

55

At 80 Nm Load: turn-off angle

Tu

rn

off

an

gle

(de

g)

Time (sec)

0 1 2 3 4 5 6 7 8

20

40

60

80

100

120

140

160

With speed dynamics (6560 to 8000 rpm)

With speed dynamics : Turn-on angle

Tu

rn

on

an

gle

(de

g)

Time (sec)

0 1 2 3 4 5 634

36

38

40

42

44

46

48

50

52

54

Tu

rn

off

an

gle

(de

g)

Time (sec)

1 2 3 4 5 660

70

80

90

100

110

With speed dynamics : Turn-off angle

With torque dynamics : 5 to 20 Nm

Tu

rn

on

an

gle

(de

g)

Time (sec)

0 1 2 3 4 5 6 7 834

36

38

40

42

44

46

48

50

52

54

With torque dynamics : turn-on angle

With torque dynamics : turn-off angle

Tu

rn

off

an

gle

(de

g)

Time (sec)

1 2 3 4 5 6 760

70

80

90

100

110

Analysis of Simulation results on Load

Application PWM mode Single-pulse mode

Turn-on

angle (degree)

Turn-off

angle(degree)

Turn-on

angle (degree)

Turn-off

angle(degree)

80 Nm of load at 6560 rpm ref speed 52.5 to 52 128 to 72 43 to 32.2 64 to 78

Steep increase of load from 5 to 20

Nm at 6560 rpm ref speed

52.5 to 52.2 104 to74 41.2 to 40 to 40.2

to 35.8

66 to 68 to73

Steep increase of speed from 6560 to

8000 rpm at 5 Nm of load

52.5 to 52.2 104 to74 41.2 to 40 to 40.2

to 34.4 to 36

67 to 68 to 75 to

73

Analysis on Load• The controller operates by varying the turn-on and turn-off angles at every

instant as per the requirement of that operating point.

• When the operation of the motor shifts from PWM mode to single pulse mode, the turn-on angle is advanced to cater to the torque demand as the overlapping of the phases is reduced.

• When there is a sudden increase of load from 5 Nm to 20 Nm or sudden increase of speed from 5650 rpm to 8000 rpm the turn-on angle is advanced and the turn-off angle is retarded to balance the new torque demand.

• The emphasis is made to show that to maintain optimal operating condition the turn-on and turn-off angles vary to make the transition smooth between the two optimal control modes

• It is proved now that the developed controller is able to control the SRM over its entire speed and torque range.

Content

• Introduction


• Characteristics





• Conclusion

• References

CONCLUSION

• This project studies optimal control modes of the SRM by striking a balance between maximum efficiency and minimum torque ripple and thus calculates the optimum switch on angles and switch off angles.

• The turn on and turn off angles are calculated through simple formulas and implemented through Simulink building blocks.

• The optimum controller determines the turn-on and turn-off angles at every instant and accordingly the converter switches are fired to cater to the torque and speed demand of that instant.

• To validate the effectiveness of the controller, simulation is carried out on a variety of load and speed combination and the effectiveness is verified.

REFERENCES

[1] C.J. Van Duijn, “Development of methods, algorithms and soft wares for optimal design of switched reluctance drives”

[2] F. Soares and P.J. Costa Branco, “Simulation of a 6/4 switched reluctance motor based on Matlab/Simulink environment

[3] R Krishnan,” Switched Reluctance Motor Drives; Modeling, Simulation, Analysis, Design and Applications”

[4] Han-Kyung Bae, “Control of Switched Reluctance Motors considering mutual inductance” [5] Ardeshir Motomedi-Sedeh, “Speed control of switched reluctance motors”

[6] M. T. DiRenzo, "Switched Reluctance Motor Control – Basic Operation and Example Using the TMS320F240, Texas Instruments Application Note," 2000.

[7] C. Mademlis and I. Kioskeridis, “Performance optimization in switched reluctance motor drives with online commutation angle control,” IEEE

[8] C. Mademlis and I. Kioskeridis, “Maximum efficiency in Single Pulse Controlled switched reluctance motor drives,” IEEE

[9] C. Mademlis and I. Kioskeridis, “Smooth Transition between Optimal Control Modes in switched reluctance motoring,” IEEE

[10] Matlab R 2008a, Version 7.6

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