EE 442 642 Thyristor Rectifiers

7/23/2019 EE 442 642 Thyristor Rectifiers

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6-1

Thyristor Converters

EE 442-642


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6-2

Thyristor Converters

Two-quadrant conversion


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6-3

Simple half-wave circuits with thyristors


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Thyristor Triggering

ICs available

st

controloo

V

v

180


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Case of Pure Resistive Load


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Full-Bridge Thyristor Converters Constant DC Current


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DC-Side Voltage

sdo

dod

VV

VV

9.0

cos

Average DC voltage:

where


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6-8

AC-Side Current

cos9.0dsdd

IVIVP

cos9.0

cos

%43.481)8/(100

,...7,5,3,/

9.0)/22(

2

1

1

PF

DPF

THD

hhII

III

II

ssh

dds

dsRSM value of source current

RMS value of fundamental current

RMS value of harmonic current

Current THDDisplacement Power Factor

Power Factor


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6-9

Effect of Source Inductance

)5.0cos(

)/2(cos9.0

)5.0cos(

2cos9.0

2

2cos)cos(

2

1

s

dsds

s

dd

s

ds

sd

s

ds

V

ILIV

DPFV

IVI

DPF

ILVV

V

ILCommutation angle:

Average of DC-side voltage:

Displacement Power Factor

RMS fundamental current


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Thyristor Converter with DC Source

Continuous current conduction mode

Discontinuous current conduction mode


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AC-Side Current Waveform(continuous conduction mode)

PSpice-based simulation example: Vs = 240 V, f = 60 Hz,

Ls = 1.4 mH, = 45 deg., Ld = 9 mH, Ed = 145 V.

Solution: Is = 60.1 A, Is1 = 59.7 A, DPF = 0.576, PF =

0.572, THD = 12.3%


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DC Voltage versus Load Current


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Inverter Mode (> 90o)


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Inverter Mode with DC Voltage Source

For a large value of Ld, idcan be assumed constant (= Id), then

dSsdd ILVVE

2

cos9.0


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Inverter Mode: Extinction Angle

Importance of extinction angle in inverter mode: The extinction timeinterval should be greater than the thyristor turn-off time:

)(180 o

qtt


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3-Phase Thyristor Converters: Simplified Case


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DC-side voltage waveforms

assuming zero ac-side inductance

cos35.1

cos23

cos

LL

LL

dod

V

V

VV


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Input Line-Current Waveform


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Input line-current waveforms assuming zero ac-side inductance

cos955.0cos

3

cos

%31]1)9/([100

,...7,5,3,/

78.0)/6(

816.03/2

2

1

1

PF

DPF

THD

hhII

III

III

ssh

dds

dds


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3-Phase Thyristor Converter with AC-side Inductance

)5.0cos(

3cos35.1

2

2

cos)cos(

DPF

ILVV

V

IL

ds

LLd

LL

ds


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Input Line-Current Harmonics


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Input Line-Current Harmonics

Typical Passive Filter Block (for each phase)


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12-Pluse Phase Controlled Rectifier

Harmonic Order: 1, 11, 13, 23, 25,


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3-Phase Thyristor Converter with Realistic Load

Continuous conduction

Mode

Discontinuous conduction

mode


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3-Phase Thyristor Inverter Constant Current


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Thyristor Inverter Constant Voltage & Current


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Thyristor Inverter Operation: Extinction Angle


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Thyristor Converters: Voltage Notching

sin2

2

LL

ds

V

IL

02

1

s

ss

L

LL

dsn

ILA 2

sin2LLn

VV Depth:

Area:

Width:


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Limits on Notching and Distortion

In practice, the notch depth at PCC depends on Ls1relative to Ls2. Let depth

factor be defined by

Given Ls1, a higher value of Ls2 results in a smaller notch.

21

1

ss

s

LL

L

EE 442 642 Thyristor Rectifiers

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