Module-10b ECEN 613 Rectifier & Inverter Circuits

Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University

http://www.ece.tamu.edu/People/bios/benjetip.htmlECEN 613Rectifiers & Inverters

ECEN 613

Rectifier & Inverter Circuits

Professor: Dr. P. Enjeti with Michael T. DanielRm. 024, WEBEmail: [email protected]

[email protected]

Textbook: Power Electronics – Converters, Applications & Design (Third edition), by: Ned Mohan et al., John Wiley

COURSE WEBPAGE: http://eCampus.tamu.edu

Module-10b

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DC-AC Inverters

� Single Phase- Half-bridge Inverter- Full-bridge Inverter- Dual output voltage configuration- Output filter design

� Three Phase Inverter- Dead-time effect

�PWM Techniques- Sinusoidal PWM- Selective harmonic elimination (SHE)- Space vector PWM

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Voltage Source Inverter

Advantages & Disadvantages

• Voltage source inverter (VSI) is a buck type converter – ac output voltage is limited and cannot exceed the dc-link

• VSI cannot tolerate short circuits – dead time between the gating of upper and lower switches need to be provided

• Three switches are on at any given instant

• VSI can supply multiple loads

• Output voltage in PWM and exhibits high dv/dt. In the case of long motor leads, voltage reflections cause over voltages at the motor terminals. Furthermore,

high dv/dt and common mode voltages contributes to ground currents and bearing fluting



Voltage Source Inverter – Common mode voltage Analysis



Voltage Source Inverter – Effect of Blanking time

S1g,ideal

S2g,ideal

S1g,actual

Van,ideal

S2g,actual

Van,actual

Verror= Van,ideal – Van,actual



Voltage Source Inverter – Effect of Blanking time

Ref: Y. Murai, etal “Waveform distortion and correction circuit for PWM inverters with switching

lag-times”, IEEE Transactions on Industry Applications, Sep/Oct 1987

Problem 8.12 page 246



Mathematical Modeling of Blanking Time Effect



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Current Source Inverter Operation



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Reference: P. Enjeti, P.D. Ziogas, J.F. Lindsay, “A current source PWM inverter with instantaneous current control capability”, IEEE Transactions on Industry Applications,

May/June 1991, pp 582-588


• CSI is a boost type converter

• Load voltage and current are sinusoidal (v.low THD) & no dv/dt issues.

• Reverse voltage blocking switches are needed

• Can tolerate short circuits

• No load operation / open circuit of the load is not possible

• Applicable for single or dedicated load

• Only two switches are on at any given instant

Current Source Inverter Operation



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Comparison of Current Source Inverter & Voltage Source Inverter

Current source inverter with symmetrical gated

commutated thyristors (SGCTs)

Voltage source inverter with NPC inverter and IGBT

devices

Ref: A.V. Meulen, J. Mauin “Current source inverter vs Voltage source inverter Topology”, Eaton Corp, Technical data

TD02004004E, Aug 2010



Comparison of Current Source Inverter & Voltage Source Inverter



Available Online Via http://libcat.tamu.edu

http://onlinelibrary.wiley.com/book/10.1002/0471773719;jsess

ionid=BE7EB55C85968F44A70290A287D9A702.d04t01

Further Reading



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Z Source Inverter


• Z source inverter is a buck-boost type converter – ac output voltage can be boosted and exceed the dc voltage source

• Z source inverter can be short circuited – the shoot through time T0 is used to boost the output voltage

• The PWM operation of the Z source Inverter is identical to a conventional VSI. Three switches are on at any given instant

• Dc voltage source current is discontinuous (similar to a buck-boost converter)

• Presence of stray inductance between the inverter and the Z-source (dc-link) causes voltage spikes and affects performance

• Equivalent resistance of the inductors limits the boost gain and also lowers the efficiency



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Z Source Inverter - Analysis



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Z Source Inverter – PWM Operation



Z Source Inverter – PWM Operation



Quazi - Z Source InvertersVSI with a boost converter

Module-10b ECEN 613 Rectifier & Inverter Circuits

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