Post on 24-Jan-2023
Inverters for Variable Frequency Drives
Prof. Thomas Jahns
May 11, 2016 UW-Madison Dynamics and Control of AC Drives
Bruce Beihoff
May 11, 2016
WEMPEC
TMJ, BCB - 2 Inverters for Variable Frequency Drives
Outline Introduction
Power Converter/Inverter Classification Structure
HVAC/ Refrigeration Inverter Applications
Future Inverter Technologies of Importance to HVAC/ Refrigeration
Conclusions
May 11, 2016
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TMJ, BCB - 3 Inverters for Variable Frequency Drives
Voltage-Source PWM Inverters
Voltage-source PWM inverters are the most widely-used class of ac drives today
Matrix Multi-Level
May 11, 2016
WEMPEC
TMJ, BCB - 4 Inverters for Variable Frequency Drives
Electrical Power Source
Electrical Power Converter
AC Machine
Modulation and Control
Command
Basic AC Drive Architecture
May 11, 2016
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TMJ, BCB - 5 Inverters for Variable Frequency Drives
Examples of AC Drive Power Converters
May 11, 2016
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TMJ, BCB - 6 Inverters for Variable Frequency Drives
PWM Waveform Synthesis
PWM is based on the concept of time-varying duty cycle control
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May 11, 2016
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TMJ, BCB - 7 Inverters for Variable Frequency Drives
Pulse Width Modulation for VSI Drives
PWM makes it possible to use same inverter switches for frequency and amplitude control, plus low-harmonic reduction
PWM voltage waveforms ‘saturate’ to 6-step when pulses drop
May 11, 2016
WEMPEC
TMJ, BCB - 8 Inverters for Variable Frequency Drives
PWM Synthesis – A, B & C Phases
• Three PWM sequences are progressively time-shifted by 120 elec. deg.
• No adjustment of dc link voltage amplitude is necessary – Phase-controlled rectifier can
be replaced by simpler uncontrolled rectifier
May 11, 2016
WEMPEC
TMJ, BCB - 9 Inverters for Variable Frequency Drives
V/Hz Control of PWM VSI-IM Drive
Simple open-loop V/Hz control of PWM VSI-IM drive follows same basic principles as for 6-step VSI drive – PWM modulation control is slaved to frequency command
Core of V/Hz Control
May 11, 2016
WEMPEC
TMJ, BCB - 10 Inverters for Variable Frequency Drives
PWM VSI Induction Motor Drives Advantages
– No need to provide means to adjust bus voltage
– Reduced low-frequency current harmonics and torque ripple
Disadvantages
– Much higher switching frequency reduces inverter efficiency
– High-frequency current harmonics may still cause noticeable motor losses, requiring machine derating
– High inverter switch dv/dt’s and di/dt’s can cause damage to winding insulation or bearings
May 11, 2016
WEMPEC
TMJ, BCB - 11 Inverters for Variable Frequency Drives
Current-Regulated PWM (CRPWM) VSI Drive
Instantaneous phase current waveforms can be regulated by closing feedback loops using measured phase currents
Provides basis for high-performance ac machine torque control
May 11, 2016
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TMJ, BCB - 13 Inverters for Variable Frequency Drives
Simplified Block Diagram of CRPWM VSI-IM Drive using FOC
By aligning currents appropriately with IM machine flux, torque and flux amplitudes can be individually controlled
Induction Machine
May 11, 2016
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TMJ, BCB - 14 Inverters for Variable Frequency Drives
CRPWM-VSI Induction Motor Drives
Advantages
– Capable of achieving excellent dynamic torque control
– Can achieve very low levels of torque ripple
– Availability of phase currents simplifies protection
Disadvantages
– Control is more complicated than for basic VSI drive
– High-performance control typically requires current sensors plus rotor position or speed feedback
May 11, 2016
WEMPEC
TMJ, BCB - 15 Inverters for Variable Frequency Drives
AC-AC Converter Induction Machine Drives
Cycloconverters and matrix converters eliminate the need for an intermediate dc link in the power converter
Multi-Level
May 11, 2016
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TMJ, BCB - 16 Inverters for Variable Frequency Drives
Matrix Converter: Direct ac↔ac
• Three-phase ac input: Three line input • Three-phase output: Three line output
– Requires 3 triple-throw switches – Each switch capable of turning on and off, plus
blocking voltage & current in both polarities
May 11, 2016
WEMPEC
TMJ, BCB - 17 Inverters for Variable Frequency Drives
Matrix Converter Implementation Using IGBTs
• Each bilateral switch implemented using 2 IGBT’s and 2 diodes • Requires total of 18 IGBTs and and 18 diodes
May 11, 2016
WEMPEC
TMJ, BCB - 18 Inverters for Variable Frequency Drives
Matrix Converter Motor Drives
Advantages – High input and output power quality using PWM – Input and output power factor are independently controlled – Inherent 4-quadrant operating capabilities – No dc link capacitors
Disadvantages – Unavailability of bilateral controlled switch devices requires
high power semiconductor parts count – Maximum output voltage as fraction of input is limited – Harmonic filters on input lines can be substantial
May 11, 2016
WEMPEC
TMJ, BCB - 19 Inverters for Variable Frequency Drives
Multi-Level
Synchronous Machine Drives
Preferred converters overlap with those of induction machines, but there are differences
May 11, 2016
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TMJ, BCB - 20 Inverters for Variable Frequency Drives
Open-Loop VSI Synchronous Motor Drive
No rotor position feedback needed for low-performance applications – Damper cage typically needed for improved stability
Constant V/Hz control holds flux ~ constant, just as for IM
May 11, 2016
WEMPEC
TMJ, BCB - 21 Inverters for Variable Frequency Drives
Current-Regulated VSI-SM Drive
Growing popularity of permanent magnet SMs is creating growing opportunities for CRPWM VSI drives for lower power
“Self-synchronous control” is key to field-oriented control of SM
May 11, 2016
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TMJ, BCB - 23 Inverters for Variable Frequency Drives
HVAC/Refrigeration Inverter Applications
Variable Torque – Fans – Pumps – Centrifugal and Scroll
Constant Torque
– Reciprocating Compressors
– Screw Compressors
– Positive Displacement Pumps
May 11, 2016
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TMJ, BCB - 24 Inverters for Variable Frequency Drives
HVAC/Refrigeration Inverter Applications Inverter Based VFD have found applications in every major sub-system
May 11, 2016
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TMJ, BCB - 25 Inverters for Variable Frequency Drives
Inverter Based Systems Entering Market
May 11, 2016
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TMJ, BCB - 26 Inverters for Variable Frequency Drives
The Inverter VFD Value Proposition HVAC/Refrigeration
Advantages • Energy savings • Low motor starting current • Reduction of thermal and mechanical stresses on motors and belts during starts • Simple installation • High power factor • Lower KVA
May 11, 2016
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TMJ, BCB - 27 Inverters for Variable Frequency Drives
HVAC/ Refrigeration VFD Inverter Challenges
Motor Transient Voltages Power line Harmonics
Electromagnetic Interfence
Progress vs. Challenges (2006-2016) • Intrinsic Filtering and Smart switching
have reduced standard drive power line harmonics below 5% THD
• Motor Transient voltages on med/long cables have been reduced by 50% by better switching and filters
• EMI/RFI has been reduced by 50 % through smart layout , grounding, filters, and better switching
May 11, 2016
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TMJ, BCB - 28 Inverters for Variable Frequency Drives
High Speed VFD Compressors
Multi Piston Reciprocating Turbo Compressor ( 15,000-22,000 rpm)
May 11, 2016
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TMJ, BCB - 29 Inverters for Variable Frequency Drives
Future Technologies
Advanced Semiconductor Switches
Advanced Controls
Advanced Power System Integration
May 11, 2016
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TMJ, BCB - 30 Inverters for Variable Frequency Drives
Advanced Semiconductor Switch
Improved Silicon Based Switches
Wide Bandgap Semiconductor Switches
May 11, 2016
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TMJ, BCB - 31 Inverters for Variable Frequency Drives
Power Semiconductor Limits
Operation Frequency (Hz)
DISCRETE MOSFET
MOSFET Modules
BIPOLAR TRANSISTOR MODULES
IGBT
MODULES
100M
10M
1M
100
10
Pow
er (V
A)
100K
10K
1K
10 100 1K 10K 100K 1M
Thyristors GTOs IGCTs
• Some devices are pushing Si boundary
• SiC and GaN offer promise for advances
May 11, 2016
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TMJ, BCB - 32 Inverters for Variable Frequency Drives
Wide Band Gap Semiconductors
May 11, 2016
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TMJ, BCB - 33 Inverters for Variable Frequency Drives
Advanced Controls
Advanced Micro Controller Chip Sets
Per switch cycle Commutation and Control
Model Predictive Control / Adaptive Control
May 11, 2016
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TMJ, BCB - 34 Inverters for Variable Frequency Drives
Per Switch Cycle Direct Control
DEADBEAT-DIRECT TORQUE CONTROL OF INDUCTION MACHINES ( Example)
DIRECT INSTANTANEOUS FORCE CONTROL (DIFC) (Example)
Advantages • Precise control of speed and torque
without position sensors • Fast dynamic response with superior
stability • Very high efficiency • Intrinsic noise cancellation
possibilities…
Disadvantages • Requires more powerful processor • More complex control code
May 11, 2016
WEMPEC
TMJ, BCB - 35 Inverters for Variable Frequency Drives
Advanced Micro Controllers
Advantages • Cost decreasing at 12% /year • Control MIPS > 30 • Capable of processing 8
control loops at 1 us update cycles
Disadvantages • May still be too expensive
????? • Control code still complex to
integrate
May 11, 2016
WEMPEC
TMJ, BCB - 36 Inverters for Variable Frequency Drives
Model Predictive Control
Advantages • Robust under the most non-linear
conditions • Combines auto-tuning and
commissioning • Combines stability with optimality
Disadvantages • Requires more powerful processor • Requires reasonable model of process
May 11, 2016
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TMJ, BCB - 37 Inverters for Variable Frequency Drives
Advanced Power System Integration
High Temperature Inverters
Standard Cell Power Integration
Integrated Motor Drive – pumps, fans, compressors
May 11, 2016
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TMJ, BCB - 38 Inverters for Variable Frequency Drives
High Temperature Power Electronics Lighting
Automotive Motor Drives
Solar PV
HiT Power Electronics
May 11, 2016
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TMJ, BCB - 39 Inverters for Variable Frequency Drives
>150°C Inverter Operation
SiC Diodes, MOSFETs
Stacked Ceramic
Capacitors
Packaging is key to achieving reliable operation up to 200ºC
Si or SiC are options
APEI
May 11, 2016
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TMJ, BCB - 40 Inverters for Variable Frequency Drives
High-Temperature Motor Drives
Cissoid
Performance Controls
250°C
175°C
50 kW
May 11, 2016
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TMJ, BCB - 41 Inverters for Variable Frequency Drives
Integrated Motor Drives
Danfoss
Controller in separate module mounted onto motor
Ratings up to 10 kW
Profiles of power converters are shrinking
Danfoss
Rexroth
May 11, 2016
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TMJ, BCB - 42 Inverters for Variable Frequency Drives
Future Integrated Motor Drives
Inverter
Wireless Control
May 11, 2016
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TMJ, BCB - 43 Inverters for Variable Frequency Drives
Integrated Modular Motor Drive
Pole face Coil
Back iron
SMC Pole Piece Communication
Bus Module
Controller + +
Machine Pole
Modular Pole-Drive
Unit
Power Electronics Controller
IMMD
Each modular pole-drive unit performs as an independent building block in motor drive stator configuration
CPES (UW)
May 11, 2016
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TMJ, BCB - 44 Inverters for Variable Frequency Drives
Gen 2 IMMD Implementation
• Prototype 10 kW, 6-phase IMMD motor and drive built for experimental verification
• Each drive unit includes independent controller for testing fault-tolerant control characteristics
May 11, 2016
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TMJ, BCB - 45 Inverters for Variable Frequency Drives
200 V, 1.2 kW, 100 kHz Gen 3 IMMD Implementation
• Uses GaN switches in multi-level converter configuration
May 11, 2016
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TMJ, BCB - 46 Inverters for Variable Frequency Drives
Alternative Building DC-Based Architecture
340 VDC Bus 340 / 48 VDC
48VDC
48VDC 48 VDC Bus
Power electronics can contribute to major efficiency improvements and new electrical distribution architectures
May 11, 2016
WEMPEC
TMJ, BCB - 47 Inverters for Variable Frequency Drives
Concluding Observations I
Induction machines are the most popular choices for ASDs, but synchronous machines are widely used at both high power (>1 MW) and high-performance low-power applications (PM machines)
PWM provides a powerful means of combining functions of adjusting frequency, changing amplitude, and suppressing low-frequency harmonics
DC link drive architectures dominate ASDs, but AC-AC matrix converters may become more popular in future if mature bidirectional switches are developed
May 11, 2016
WEMPEC
TMJ, BCB - 49 Inverters for Variable Frequency Drives
Concluding Observations III VSI (Voltage Source Inverters) have made major in roads
through out the HVAC and Refrigeration applications Current-regulated VSI inverters are very popular when higher
performance is required – Provides basis for field-oriented control – These see further use in advanced compressors
High Speed compressors and higher frequency inverters are coming with advanced inverters
Inverters based on wide bandgap semi-conductors that are higher frequency and very mechanically tough are beginning to appear
Integrated Motor Drives are making their second foray into broader HVAC and Refrigeration applications.