This document provides an overview of power inverters. It defines an inverter as a device that converts direct current (DC) to alternating current (AC). It describes the main components of a typical inverter system and how inverters are used in applications such as renewable energy, electric vehicles, and industrial machinery. The document also discusses factors that affect inverter design such as switching components, heat dissipation, and protection from voltage spikes or grid faults.

1. Basics of the Power Inverter

2. Before We Start
q This webinar will be available at
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3. Moderator Presenters
Paul Dvorak
Windpower Engineering
& Development
John Greulich
PSI Repair
Aaron Lawson
PSI Repair

5. Our Livonia Campus

6. PSI Repair Services, Inc.
• Electronic
• Mechanical
• Ballscrew
• Electronic Design
• Mechanical Design
• Manufacturing
• Failure Analysis
• RAC
• Find Parts
Repair Services
Engineering Services
On-­‐‑Line Services
Surplus

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General Motors
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Toyoda
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LuOin
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SKF

8. Repair Capabilities
Electronics
Robotics
Motion Control
Process Control
Instrumentation
Hydraulics
Vacuum Pumps
Servo Valves
Gearboxes Ball Screw

9. What is an Inverter?
An inverter is a type of power converter that changes
direct current (DC) to alternating current (AC).

10. Types of Power Converters
AC
AC/AC Converting DC/DC Converting
AC
DC
DC
AC/DC Rectification
DC/AC Inverting

11. Types of Power Converters
AC
AC/AC Converting DC/DC Converting
AC
DC
DC
AC/DC Rectification
DC/AC Inverting

12. Types of Power Converters
AC
AC/AC Converting DC/DC Converting
AC
DC
DC
AC/DC Rectification
DC/AC Inverting

13. Types of Power Converters
AC
AC/AC Converting DC/DC Converting
AC
DC
DC
AC/DC Rectification
DC/AC Inverting

14. Types of Power Converters
AC
AC/AC Converting DC/DC Converting
AC
DC
DC
AC/DC Rectification
DC/AC Inverting

15. Predecessor to Solid State Inverters
Rotary Converter - Converts alternating current (AC)
to direct current (DC), or DC to AC power.

16. Where Are Inverters Used?
• Renewable Energy
• Electric Vehicles
• Industrial Applications
• Medical

17. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

18. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

19. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

20. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

21. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

22. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

23. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

24. Generator
Rec+fier
AC-­‐DC
DC
Link
Capacitors
Inverter
DC-­‐AC
Communica+on
&
Control
Unit
3
Phase
Transformer
What Does an Inverter Do?

25. How Does an Inverter Work?
PWM Waveform
AC Voltage
DC voltage

26. What is PWM
• PWM: Pulse Width Modulation
• Square wave with a varied duty cycle
• Duty Cycle is the on-time/period
AVG HI LOW V = DV + (1−D)V
period
on-time off-time

27. Main Components of a Wind Inverter System
Generator
DC Link
Capacitor
Bus
Structure
IGBT
Heat Sink
Pad Mount
Transformer
Control
Electronics
Drive Utility Grid
Electronics
Snubber
Capacitor

28. Types of Generators
Asyncronous Generators
Types: Squirrel Cage
DFIG
Syncronous Generators
Types: Permanent Magnet
Electrically Excited

29. Wind Applications

30. Doubly-Fed Asynchronous Generators
• Around 80% of wind turbines
• Main Disadvantage: Slip ring contacts

31. Full Power Converter
• Reasonably priced, efficient converter
• Disadvantages: Increased losses and Harmonics

32. Bi-Directional Full Power Converter
• Full power available in low wind conditions

33. Solar Applications

34. Basic Photovoltaic Inverter System
• Maximum Power Point (MPP) Tracker or DC-DC boost
converter

35. String inverter
• Example: Rooftop photovoltaic systems
• Outputs from 500 W to 5 kW

36. Multistring inverter
• Example: Medium sized
rooftop or ground-based
systems
• Outputs from 3 kW and
30 kW

37. Central inverter
• Example: Large
three-phase solar
farms
• Outputs from 60 kW
to 1 MW

38. General Applications

39. Basic Converter
• Example: Machine Tools under 15kW
• Not able to recover energy

40. Bi-Directional Converter
Energy Efficient: energy fed back to the grid

41. Goals of a Well Designed Inverter
Well
Balanced
Switching
Wide
Operating
Temperature
Long Life
Good Thermal
Efficiency
Customer
Satisfaction
Fast Fault
Detection

42. How Design Affects Inverter Operation
DC Link
Capacitor
s
• Fast Switching
• Cost effective – Typically 30-50% of
inverter cost
IGBTs
• Low equivalent series inductance (ESL)
• Film vs Aluminum Electrolytic

43. How Design Affects Inverter Operation
Bus
Structure
Snubber
Capacitor
s
• Low Stray inductance
• Poor snubber circuits can increase
ringing

44. How Design Affects Inverter Operation
Drive
Electronic
s
Control
Electronic
s
• Controls the IGBT
• Short circuit and overvoltage
protection
• Controls Speed and Duty Cycle

45. How Design Affects Inverter Operation
Heat Sink
• Surface flatness ≤ 50μm
• Surface roughness ≤ 10μm
OEM
specified
screen
Thermal
interface
material

46. Thermal Interface Material (TIM)
Thermal
Resistance
Minimum Maximum
Thickness of TIM

47. Thermal Interface Material (TIM)
Thermal
Resistance
Minimum Maximum
Thickness of TIM

48. Thermal Interface Material (TIM)
Thermal
Resistance
Minimum Maximum
Thickness of TIM

49. Thermal Interface Material (TIM)
Thermal
Resistance
Minimum Maximum
Thickness of TIM

50. The Perfect Switch
No Overshoot or
Ringing
Fast Turn On Fast Turn Off

51. Design Trade-offs
Speed
Excessive
Voltage
Spikes
Safe
Operating
Zone
Excessive Heat

52. The Worst Case: Overvoltage
Excessive voltage
overshoot
V=퐿 푑푖/푑푡
Excessive
Ringing
1700V
IGBT Peak
1000V
IGBT Nominal

53. The Worst Case: Excessive Heat
Very Slow Turn
Off
Excessive Heat
Generation
Very Slow Turn
On

54. The Real World Switch
Minimal Overshoot Minimal Ringing
Minimal Turn
on time
Minimal Turn
off Time

55. Failure Originating from Utility Grid
Grid Faults include:
• Transients
• Power Factor issues
• High grid voltage
• Low grid voltage

56. Failures

57. Questions?
Paul Dvorak
Windpower Engineering & Development
pdvorak@wtwhmedia.com
Twitter: @Windpower_Eng
Aaron Lawson
PSI Repair
Alawson.rsi@psi-corp.com
Phone: 734.8535427
Twitter: @psi_repair
John Greulich
PSI Repair
John.greulich@psi-corp.com
Phone: 734.751.5133
Twitter: @psi_repair

58. Thank You
q This webinar will be available at
www.windpowerengineering.com & email
q Tweet with hashtag #WindWebinar
q Connect with Windpower Engineering & Development
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