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Basics of the Power Inverter
| Date post: | 16-Jul-2015 |
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Engineering |
| Upload: | windpower-engineering-development |
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Basics of the Power Inverter
Before We Start q This webinar will be available at
www.windpowerengineering.com & email
q Q&A at the end of the presentation
q Hashtag for this webinar: #WindWebinar
Moderator Presenters
Paul Dvorak Windpower Engineering
& Development
John Greulich PSI Repair
Aaron Lawson PSI Repair
Our Livonia Campus
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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Repair Capabilities
Electronics
Robotics
Motion Control
Process Control Instrumentation
Hydraulics
Vacuum Pumps
Servo Valves
Ball Screw Gearboxes
What is an Inverter?
An inverter is a type of power converter that changes direct current (DC) to alternating current (AC).
Types of Power Converters
AC
AC
DC
DC
AC/DC Rectification
DC/AC Inverting
DC/DC Converting AC/AC Converting
Types of Power Converters
AC
AC
DC
DC
AC/DC Rectification
DC/AC Inverting
DC/DC Converting AC/AC Converting
Types of Power Converters
AC
AC
DC
DC
AC/DC Rectification
DC/AC Inverting
DC/DC Converting AC/AC Converting
Types of Power Converters
AC
AC
DC
DC
AC/DC Rectification
DC/AC Inverting
DC/DC Converting AC/AC Converting
Types of Power Converters
AC
AC
DC
DC
AC/DC Rectification
DC/AC Inverting
DC/DC Converting AC/AC Converting
Predecessor to Solid State Inverters
Rotary Converter - Converts alternating current (AC) to direct current (DC), or DC to AC power.
Where Are Inverters Used?
• Renewable Energy • Electric Vehicles • Industrial Applications • Medical
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
Generator Rec+fier AC-‐DC
DC Link Capacitors
Inverter DC-‐AC
Communica+on & Control Unit
3 Phase Transformer
What Does an Inverter Do?
How Does an Inverter Work?
PWM Waveform
AC Voltage
DC voltage
What is PWM • PWM: Pulse Width Modulation • Square wave with a varied duty cycle • Duty Cycle is the on-time/period
LOWHIAVG VDDVV )1( −+=
period
off-time on-time
DC Link Capacitor
Bus Structure
IGBT Heat Sink
Main Components of a Wind Inverter System Generator Pad Mount
Transformer
Utility Grid Drive Electronics
Control Electronics
Snubber Capacitor
Types of Generators Asyncronous Generators
Types: Squirrel Cage DFIG
Syncronous Generators Types: Permanent Magnet
Electrically Excited
Wind Applications
Doubly-Fed Asynchronous Generators
• Around 80% of wind turbines • Main Disadvantage: Slip ring contacts
Full Power Converter
• Reasonably priced, efficient converter • Disadvantages: Increased losses and Harmonics
Bi-Directional Full Power Converter
• Full power available in low wind conditions
Solar Applications
Basic Photovoltaic Inverter System
• Maximum Power Point (MPP) Tracker or DC-DC boost converter
String inverter
• Example: Rooftop photovoltaic systems • Outputs from 500 W to 5 kW
Multistring inverter
• Example: Medium sized rooftop or ground-based systems
• Outputs from 3 kW and 30 kW
Central inverter
• Example: Large three-phase solar farms
• Outputs from 60 kW to 1 MW
General Applications
Basic Converter
• Example: Machine Tools under 15kW • Not able to recover energy
Bi-Directional Converter
Energy Efficient: energy fed back to the grid
Well Balanced Switching
Goals of a Well Designed Inverter
Long Life Good Thermal
Efficiency
Wide Operating
Temperature Customer
Satisfaction
Fast Fault Detection
DC Link Capacitor
s
How Design Affects Inverter Operation
• Fast Switching • Cost effective – Typically 30-50% of
inverter cost
IGBTs
• Low equivalent series inductance (ESL) • Film vs Aluminum Electrolytic
Snubber Capacitor
s
Bus Structure
How Design Affects Inverter Operation
• Low Stray inductance
• Poor snubber circuits can increase ringing
Drive Electronic
s
Control Electronic
s
How Design Affects Inverter Operation
• Controls the IGBT • Short circuit and overvoltage
protection
• Controls Speed and Duty Cycle
Heat Sink
How Design Affects Inverter Operation • Surface flatness ≤ 50µm • Surface roughness ≤ 10µm
OEM specified screen
Thermal interface material
Thermal Resistance
Minimum Maximum
Thickness of TIM
Thermal Interface Material (TIM)
Thermal Resistance
Minimum Maximum
Thickness of TIM
Thermal Interface Material (TIM)
Thermal Resistance
Minimum Maximum
Thickness of TIM
Thermal Interface Material (TIM)
Thermal Resistance
Minimum Maximum
Thickness of TIM
Thermal Interface Material (TIM)
The Perfect Switch
Fast Turn On Fast Turn Off
No Overshoot or Ringing
Design Trade-offs
Speed
Excessive Voltage Spikes
Safe Operating Zone
Excessive Heat
The Worst Case: Overvoltage Excessive voltage overshoot
Excessive Ringing
V=𝐿𝑑𝑖/𝑑𝑡 1000V IGBT Nominal
1700V IGBT Peak
The Worst Case: Excessive Heat
Very Slow Turn Off
Excessive Heat Generation
Very Slow Turn On
The Real World Switch
Minimal Turn on time
Minimal Turn off Time
Minimal Overshoot Minimal Ringing
Failure Originating from Utility Grid
Grid Faults include: • Transients • Power Factor issues • High grid voltage • Low grid voltage
Failures
Questions? Paul Dvorak Windpower Engineering & Development [email protected] Twitter: @Windpower_Eng
John Greulich PSI Repair [email protected] Phone: 734.751.5133 Twitter: @psi_repair
Aaron Lawson PSI Repair [email protected] Phone: 734.8535427 Twitter: @psi_repair
Thank You q This webinar will be available at
www.windpowerengineering.com & email
q Tweet with hashtag #WindWebinar
q Connect with Windpower Engineering & Development
q Discuss this on the EngineeringExchange.com
