Your SlideShare is downloading. ×
High frequency Sine wave inverter -Challenges in voltage feedback
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.


Saving this for later?

Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime - even offline.

Text the download link to your phone

Standard text messaging rates apply

High frequency Sine wave inverter -Challenges in voltage feedback


Published on

Published in: Technology

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

No notes for slide


  • 1. High frequency Sine wave inverter Challenges in voltage feedback www.controltrix.comcopyright 2011 controltrix corp www.
  • 2. System Configuration • DSC on primary (low voltage) side • Front end Switched mode isolated converter • Boost battery voltage to 400V • Hi bridge Inverter to generate sine wave Objective • Control the output to a sine wave under various loadscopyright 2011 controltrix corp www.
  • 3. Requirements of feedback circuit • High Voltage feedback • Isolation • Low cost /rugged • Linearitycopyright 2011 controltrix corp www.
  • 4. RMS control mode • Measure rms voltage err. @ (50Hz/60Hz freq) • Change ONLY modulation index ‘m’ with RMSV err • Duty d = m.sin(2. .f.t) is • @ Steady state maintains sine wave • Poor /slow dynamic response approximately 100ms • Distortion under non linear loads like rectifier • Extremely low bandwidth • Low computation load req. • Low execution ratecopyright 2011 controltrix corp www.
  • 5. RMS control mode feedback • Std Low grade/low cost 50Hz Potential Transformer(PT) • Std part in electric metering (widely available) • Satisfies 4 desirables  Isolation  Low cost  Ruggedness  Linearity @ 50/60 Hz output voltagecopyright 2011 controltrix corp www.
  • 6. Instantaneous control • Industry term for Hi bandwidth digital control • Hi sampling frequency and code execution rate ~ 20 KHz • Great dynamics approx. • ~400 us step response • Non linear and fast changing loads handled • Large stiffness (low output impedance) • Perfect regulation even with leading /lagging PFcopyright 2011 controltrix corp www.
  • 7. Feedback requirement Need • Accurate real-time fast high bandwidth voltage feedback PT limitations • PT magnetically coupled device • No output of PT for DC component in input signal • Any DC offset will not be visible to DSC/DSPcopyright 2011 controltrix corp www.
  • 8. PT feedback characteristics PT input with DC offset PT output (DC offset blocked) • Low and High frequency signals undergo significant distortioncopyright 2011 controltrix corp www.
  • 9. Challenge Using PT feedback would lead to… Output Voltage • Unstable or saturated intermittently (+/-400 Vdc) Result • Malfunction of Downstream equipment • Damage to Downstream equipment • Catastrophic results or shutdown !!!!copyright 2011 controltrix corp www.
  • 10. Actual voltage: 200 V/div PT output output voltage and PT feedback are not correlatedcopyright 2011 controltrix corp www.
  • 11. Summary • The PT works properly only @ 50/60Hz sine wave is being measured • To get accurate sine wave the PT needs to work properly in closed loop • Vicious dependency deadlock causes catastrophe !!!! • Chicken and egg problem !!!!copyright 2011 controltrix corp www.
  • 12. Proposed Solution • No DC offset in output waveform • PT based feedback instantaneous control • Pure software solution • Low THD (slightly worse wave shape than ideal feedback) • Expensive, Complex ,Non linear isolation solutions not needed !!! • E.g. : Opto-couplers, voltage to frequency converters, PWM generators • Patent pendingcopyright 2011 controltrix corp www.
  • 13. Experimental results Instantaneous closed loop control system Voltage output 100 V/div PT output Final output voltage waveformcopyright 2011 controltrix corp www.
  • 14. Thank You consulting@controltrix.comcopyright 2011 controltrix corp www.