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DEMO TITLES

Variable Frequency drives Induction MotorCase I: Converter as an 18-Pulse Diode Rectifier

Case II: Converter as an Active Front Rectifier

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1. OBJECTIVE AND DESCRIPTION

The following document shows the simulation of a VFD (Variable Frequency Drives) 2-levelvoltage with an 18-Pulse Diode Rectifier and an Active Front End (AFE) Rectifier using thepower electronics components from the Engineering suite V6 Electrical library.

The AFE and motor controllers are designed using my published documents (Vector Control ofInduction Motor.pdf and Three Phase Rectifier Controllers Design.pdf).

A three phase voltage source supplies a VFD that drives an ungrounded Induction Motor. TheInduction Motor has the following parameters:

,

,

At t = 0 s the reference speed is set to 120 rad/s and reverse to -120 rad/s at t = 1.6 s. Themaximum torque allows is 300 Nm.

Simulate the motor drives using Current-Sourced Inverter (2-Level Voltage).

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Phase shifting transformers (Yz +20 deg, Yz -20 deg)

Transformers (Yy 0 deg)

DC link capacitor is pre-charged at 900 V and 1000 V as maximum voltage allowed

Breaking Resistor

Case II: The converter is an AFE Rectifier in abc reference frame follows by a 2-level voltage

The IGBT on the AFE side is built as an ideal switch in parallel with a diode.

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3. SIMULATION PARAMETERS

The simulation was run in time domain with sample time of

4. PROCESSES REPRESENTATION IN ES V6

See the end of the document

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6. ENGINEERING SUITE V6 RESULTS

Case I: The VFD is built has an 18-pulse diode Rectifier follows by a 2-level voltage

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Case II: The converter is an AFE Rectifier in abc reference frame follows by a 2-level voltage

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Conclusion

The following conclusions can be made: Visually, the network current in steady state for AFE converter contains less

harmonics than an 18-pulse diode converter, In order to avoid the inrush network current (normally due to the capacitor charging),

a precharged capacitor has been used, For the AFE converter, DC voltage is kept nearly the reference value, For the 18-pulse diode converter a breaking resistor has been used to avoid

overvoltage of the capacitor, the torque doesnt exceed the maximum allowed ( 300 Nm).

7. REFERENCE BOOKS

1. Power electronics. Converters, applications and design, 2nd edition.Mohan / Underland / Robbins.

2. Power electronics. Converter Harmonics. Multipulse methods for clean power.

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