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3-Phase Shunt Active Filter for Harmonic compensation

Unnikrishnan A.K., Aby Joseph and Subhash Joshi T.G.,

CDAC Trivandrum

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The Case under studyPeekay Steels, CalicutInduction FurnaceAuxiliary Load

Furnace Load cycleLining / SinteringHeating

Current WaveformsLining / SinteringHeating

Overview of the Presentation

IEEE Standard 519PQ SolutionsImprovements in Current waveforms

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Site Study

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Casting plant in the mini steel plant selected11kV feeders connected to induction furnace and the auxiliary loadsThe electrical rating of the 9T furnace is 4MWFault level of the feeder is 250MVAMeasurement conducted at the 11kV incomer for voltage, current and harmonics

Peekay Steels, Calicut

FURNACECONVERTER

INDUCTIONFURNACE

11kV BUS

5MVA 11kV/850-850VD/D6-Υn11

BOCB

TOAUXILIARY

LOADS

500kVA11kV/433VDYn11

BOCB

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BOCB

11KV GRID

11KV INCOMING

TO AUXILIARY

LOAD

FURNACE CONVERTER

4000KW

5000KVA DYN11 & DD6

11KV/850V

BOCB

11KV/415V

INDUCTION FURNACE

Single Line Diagram of the Plant

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Input is through two 6P converters fed by a D/Y/D transformerThe furnace can operate with one 6P converter or both the converters to form 12PThe converter panel has AC capacitor banks to improve the converter power factorThe capacity of the furnace is 9 Ton, 4MWThe furnace has two crucibles which are used alternatively

The 4MW Induction Furnace

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Lining / SinteringForming the Refractory LiningHeats slowly starting with power level as low as 200kWStarts with single converter (6P) and continues till 2000kWPower factor fluctuates between 0.39 and 0.95Dominant Current harmonics are 5th and 7th

Furnace Load Cycle 1

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Furnace converter current in 6P mode at 2000kW load

Current Waveforms in Load cycle 1

19.8%

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HeatingSecond converter switched ON from 2000kW onwards and configuration becomes 12PMelting of scrap metalPower level fluctuates and reaches 4000kWPower factor is varying between 0.60 and 0.95Current harmonics exceeds 12% with 11th and 13th dominating

Furnace Load Cycle 2

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Furnace converter current in 12P mode at 4000kW load

Current Waveforms in Load cycle 2

6.6%

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MAXIMUM HARMONICS CURRENT DISTORTION IN PERCENT OF IL(Full load)Individual Harmonics Order (Odd Harmonics)

IEEE STANDARD 519-1992

Isc/IL <11 11<h<17

17<h<23

23<h<35

35<h TDDTotal Demand Distortion

<20 4.0 2.0 1.5 0.6 0.3 5.0

20<50 7.0 3.5 2.5 1.0 0.5 8.0

50<100 10.0 4.5 4.0 1.5 0.7 12.0

100<1000 12.0 5.5 5.0 2.0 1.0 15.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0

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Frequent failure of CTs and PTs in substationHeating of substation transformerFailure of fans and lamps in the plant

PQ Issues at Site

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PQ Solutions implemented by C-DAC(T)

11KV GRID

11KV INCOMING

FURNACE CONVERTER

4000KW

5000KVA DYN11 & DD6

11KV/850V

STATCOM

500kVAR

C-DAC’s Installation 500kVA

11KV/830VDYn11

ABSFU

Measuring point

INDUCTION FURNACE

BOCB

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STATIC COMPENSATOR (STATCOM)

LoadSystem bus

V

Coupling transformer

ICr

Xs

V0

DC-ACSwitchingconverter

+CsVdc

ILV

ILr

ILa

ICr

VO

VX

IL

VAR COMPENSATION

STATCOM

LOADAC MAINS

ILIS

IF

HARMOINCS FILTERING

Compensates VAR and

Harmonics

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AdvantagesEach switching device experiences half DC bus voltageHigher rated converters achieved with lower voltage device Better harmonic performance

Diode clamped 3-Level Converter

YR

+ve Bus

3-Level Voltage Source Converter

B

-ve Bus

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Power rating 500kVARGrid voltage 11kV +10% -15%, 3-phase, 50Hz±5%Grid connection Through step down transformer (11kV/830V)

DC bus voltage 1700VConfiguration 3-level voltage source converter

Switching freq. 10kHzAmbient temp. 450CCooling Forced AirController TMS320F240 DSP based

Specification of 500kVAR 3-Level STATCOM

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Hardware Configuration

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Converter Stack

IGBTsCapacitor bankOver temperature protectionGate driver PCBInter connections with sandwich busbars

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Multi layer bus (Sandwich bus) architecture

To minimise the stray inductanceFor compact constructionReliable electrical connectionEasy assembly and repair

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Gatedriver PCBMounted on heat sink, close to the deviceOptical interface for higher electrical isolation and noise immunityOver current protectionPower supply requirement: +15V, 2A

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Control Strategy

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Control Strategy for STATCOM

Unit Vector generation

EREYEB

3-Phase

D-Q

IR Load

IB Load

IY LoadID h LOAD

IQ f LOAD

reactive/ harmonic current

components

3-Phase

D-Q

IR STATCOMIY STATCOMIB STATCOM

reactive/ harmonic current

components

ID STATCOM

ID f LOAD

ID f STATCOM

IQ h STATCOM

IQ f STATCOM

ID h STATCOM

IQ STATCOM

ID Load

IQ LoadIQ h LOAD

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Control Strategy for STATCOM

VR*

VY*

VB*

Switching strategy

Switching PatternsController

I statcom

Unit vector

I Load

Vdcfb

Vdcref.

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Block Diagram of Digital Controller18 Analog Input

channels

32K word of RAM

CY7C1020

TMS 320F240

6 PWM

3 PWM

DSP

ADC interface(on-chip + external)

PWM Interface

PWM Interface

6 PWM

6 PWM

DACInterface

O/P Interfaces

I/PInterface

With isolation

Monitoring

Fault Interface

User Commands

Controls and Status Indication

RS 232Driver

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Digital Controller

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STATCOM SchematicVdc(regulated)

Grid

DSP BASEDCONTROLLER

Current F/BFiber opticlink

DISPLAY ANDCONTROL

OtherInterlocks

Series choke

3-Level Voltage source converter

Furnace Load

Voltage F/B

PTs

830V/11kV

Vdc f/b

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Test Results

28CCC---DAC TRIVANDRUMDAC TRIVANDRUMDAC TRIVANDRUM

Current Harmonics compensation by STATCOM at Full load

Un-compensated

Compensated

6.6%

2.5%

1. Un-compensated Furnace converter current

2. Compensated Furnace converter current

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Un-compensated

CCC---DAC TRIVANDRUMDAC TRIVANDRUMDAC TRIVANDRUM

Compensated

Current Harmonics compensation by STATCOM in Sintering Mode

19.8%

9.2%

1. Un-compensated Furnace converter current

2. Compensated Furnace converter current

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Voltage Harmonics Improvement

Waveform 1 (with compensation) Waveform 2 (without compensation)THD 2.97% THD 4.30%11th harmonic 1.14% 11th harmonic 2.77%13th harmonic 0.84% 13th harmonic 2.20%

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Load Current

Grid Current

Converter Current

Various Current Waveforms With STATCOM

Various Current Waveforms with 500kVAR STATCOM in Harmonic

Compensation mode

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STATCOM: OFF STATCOM: ON

Current TDD %as % of Full load current*

Current TDD %as % of Full load current*

P.F P.F

0.43

0.98

0.97

0.96

Aph Bph Cph Aph Bph Cph

0.38

0.97

0.97

0.96

Load (kVA)

Load %

787 19.69 10.45 9.60 9.63 4.95 4.66 4.66

2724 68.10 5.71 5.65 5.44 3.54 3.47 3.47

3646 91.15 9.88 9.60 9.75 3.64 3.64 3.64

3997 99.93 7.59 7.39 7.59 4.00 4.20 4.00

Current Harmonics Reduction at various load levels

*Note: Current TDD calculated as per IEEE 519, i.e as % of Full load current

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STATCOM INSTALLATION AT PEEKAY STEELS

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Thank youThank you