slides topic 4 - ryerson university · 2006. 3. 30. · 2 3 • operation modes for ac motors 1....

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EE8412Advanced AC Drive Systems

Topic 4Voltage Source Inverter Fed Drives

ACS1000 MV Drive Source: ABB

Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley-IEEE Press, 2006, ISBN: 0-471-73171-4

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Lecture Topics• Steady-state Operation Modes

• Two-level VSI Fed MV Drives

• Neutral-point Clamped (NPC) Inverter Fed Drives

• Cascaded H-Bridge (CHB) Inverter Fed Drives

EE8412 Advanced AC Drive Systems

Voltage Source Inverter Fed Drives


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• Operation Modes for ac motors

1. Constant Flux Operation: V / f = constant

2. Constant Power Operation: V = constant, f = variable

3. Voltage Compensation at low rotor speeds

V – stator voltage, f – stator frequency

Topic 4 Voltage Source Inverter Fed Drives

Steady-state Operation ModesEE8412


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• Constant Flux Operation

- If Φ > Φ rated , magnetic core will be saturated.

- If Φ < Φ rated , rated torque cannot be achieved.

Φ – motor magnetic flux (general term)

Toque = flux x current (general term)




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Induced emf in a magnetic circuit:E = 4.44 Φ N fwhere N – number of turns of the coil

Φ = E / ( 4.44 N f ) Φ = const → E / f = const → V / f = const




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eTRatedeT MaxeT

TeMax = constant




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• Constant Power Operation

When f > frated → rotor speed n > nrated , but V should be kept const to avoid insulation breakdown

Since Φ = E / ( 4.44 N f )V = const and f ↑ → Φ ↓




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• Constant Power Operation

eTRatedeT MaxeT




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• Voltage Compensation at Low Rotor Speeds

To compensate the voltage drop on the stator resistors at low rotor speeds

Ratedf

RatedV

compV




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Two-level Inverter Fed DrivesEE8412

VDM5000 Two-level VSI Source: Alstom


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• System Block Diagram

fC

fL

dC

⎪⎭

⎪⎬⎫




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• Main Functional Blocks1) Rectifier circuit- Phase shifting transformer- 12 pulse diode rectifier for line current THD reduction

2) DC circuit- Dynamic braking circuit- Capacitor Filter

3) Inverter circuit - PCBB: power converter building block- Series devices for high voltage operation

4) Motor side filter- dv/dt reduction- THD reduction- Common mode voltage elimination




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• Inverter Topology PCBB




Source: Alstom

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• PCBB – Power Converter Building Block

sRpR

sC




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NPC Inverter Fed DrivesEE8412

VDM6000 Multilevel NPC Inverter Source: Alstom


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dCsC

sC

sD

sDsR

sL

dC

sL

sR

fC

fL

• Drive System Diagram

Switching devices: IGCTs


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• Main Functional Blocks1) Rectifier circuit- Phase shifting transformer- 12 pulse diode rectifier for line current THD reduction

2) DC circuit - Capacitor Filter- di/dt clamping circuit

3) Inverter circuit- Three-level NPC inverter

4) Motor side filter- dv/dt reduction- THD reduction- Common mode voltage elimination


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• Drive System Specifications

NoRegenerative braking capability

> 6 yearsMean time between failure (MTBF)

Forced air or liquidCooling

Standard: 10% for one minute every 10 minutesOptional: 150% for one minute every 10 minutes

Overload capability

Induction or synchronousMotor type

Sinusoidal (with output filter)Output waveform

> 0.95 ( Displacement power factor > 0.97)Input power factor

Typically > 98.0% (including output filter losses but excluding transformer losses)Drive system efficiency

0 ~ 66Hz (up to 200Hz optional)Output frequency

0 ~ 2300V, 0 ~ 3300V, 0 ~ 4160V Output voltage rating

400 ~ 6700HP (0.3 ~ 5 MW) Output power rating

2300V, 3300V, 4160V Nominal input voltage

Drive system Specifications


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• Drive System Specifications (Continued)

Non-rupture, non-arcInverter/rectifier switch failure mode

Hysteresis modulation generated by DTC schemeModulation technique

2Number of clamping diodes per phase

4Number of GCTs per phase

500HzGCT switching frequency

PWM, three-level NPC inverterInverter type

Standard: 12-pulse diode rectifier Optional: 24-pulse diode rectifier Rectifier type

Power Converter

Specifications

<10msTorque response time

< 0.5% without encoder< 0.01% with encoderSteady state speed error

< 0.4% without encoder< 0.1% with encoderDynamic speed error

Direct torque control (DTC)Control scheme

Control Specificatio

ns


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• IGBT Based NPC Inverter Drives

fC

fLdC

dC


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• System Specifications – IGBT based drives

Typically > 98.5% (at rated operating point, excluding transformer losses)

Drive system efficiency

1:1000 (with encoder)Motor speed range

0 ~100Hz (standard)Output frequency

0 ~ 2300V, 0 ~ 3300V, 0 ~ 4160V, 0 ~ 6600V Output voltage range

0.8 ~ 2.4MW @2300V1.0 ~ 3.1MW @3300V1.3 ~ 4.0MW @4160V4.7 ~ 7.2MW @4160V (Parallel converter configuration) 0.6 ~ 2.0MW @6600V

Output power rating

2300V, 3300V, 4160V, 6600V Nominal utility/motor voltage

> 0.96 (12-pulse diode rectifier)Displacement power factor

Standard: 12-pulse diode rectifierOptional: 24-pulse diode rectifier

or active front end (PWM IGBT rectifier)Rectifier


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Cascaded H-bridge Inverter Fed DrivesEE8412

Perfect Harmony MV Drive Source: ASI Robicon


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• Block Diagram

°−= 20δ

°= 0δ

°+= 20δ

dC


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• Main Functional Blocks

1) Rectifier circuit- Phase shifting transformer- Multipulse diode rectifier for THD reduction

2) Modular structure- Power Modules

3) Line- and motor-side filters- No


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• Line-side Waveforms


Source: ASI Robicon

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• Drive Configurations

6000Hz600Hz480V1160154515304160V

4800Hz600Hz480V948123612243300V

3600Hz600Hz480V7369279182300V

Inverter

fsw

Device

fsw

NominalPower Cell

Output

Voltage Levels

IGBTs

Power

Cells

Transformer

SecondaryCables

Secondary

Windings

Rectifier Pulses

NominalUtility/Motor

Voltage

Multilevel CHB InverterMultipulse Diode Rectifier


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• 6600V CHB Fed Drive

UtilitySupply

PowerCell

MPhase ShiftingTransformer

N

A B C

Dual 3300V Drive


28Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley-IEEE Press, 2006, ISBN: 0-471-73171-4

EE8412 Advanced AC Drive Systems


slides topic 4 - ryerson university · 2006. 3. 30. · 2 3 • operation modes for ac motors 1....

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