1. A Comparison of Modulation Techniques for Three-Level Neutral-Point-Clamped Inverter Fed Motor Drives
William Karls1, Ruirui Chen2, Dr Fred Wang2
1The University of Wisconsin-Platteville 2The University of Tennessee, Knoxville
List schemes, include diagram
INTRODUCTION
Pulse width modulation (PWM) is the most popular method for driving inverter-fed motor drive.
PWM also generates undesired harmonics in addition to the required sinusoidal voltage/current.
Different modulation techniques will have a different impact on the common mode voltage, harmonic distortion, and switching loss of the motor drive system.
Large common mode voltage and harmonic distortion may cause failure of motors.
Large losses of the inverter may increase cost and degrade motor drive system performance.
Fig. 1. A typical motor drive system in aircraft application.
OPERATION AND IMPLEMENTATION OF MODULATION TECHNQUES
OOO
PPP
NNN
PNN
PON
OPN
NPN
NPO
NPP
NOP
NNP
ONP
PNP
PNO
POO
ONN
OON
PPO
OPO
NON
NOO
OPP
OOP
NNO
ONO
POP 1 2 3 4 5 6
Vreference
Table 1. List of the modulation techniques that were implemented and examined.
Carrier- Based Modulation
Space Vector Modulation
Phase Disposition
Nearest Three Vector Modulation
Phase Opposite Disposition & Alternative Phase Opposite Disposition
Discontinuous Pulse Width Modulation
Common Mode Reduction Modulation
Common Mode Elimination Modulation
Fig. 2. One phase leg of the three-level ANPC inverter (left) and its PWM sequences (right).
Fig. 4. Space vectors for the Nearest Three Vector Modulation.
ONN 4 t
sub2 2
PNN
sub5
PON
POO
sub4
Bigsector = 1
Subsector = 2
Fig. 3. Modulating wave (orange) and two carrier waves (green) for Phase Disposition carrier-based pulse width modulation.
Fig. 5. Switching sequence of subsector 2 of sector I for Nearest Three Vector Modulation.
Fig. 6. Simulink model utilized to implement each modulation technique.
COMPARISON OF MODULATION TECHNIQUES
Fig. 7. Peak common mode voltage for each pulse width modulation technique.
Fig. 8. Switching losses for each pulse width modulation technique.
Fig. 9. Line voltage total harmonic distortion for each pulse width modulation technique.
Fig. 10. Line current total harmonic distortion for each pulse width modulation technique.
CONCLUSION AND FUTURE GOALS 1
PON
OPN
NPO
NOP
ONP
PNO
OOO 2 3 4 5 6
Vreference
Common mode reduction pulse width modulation is the best of the seven modulation techniques.
Second lowest peak common mode voltage.
Second lowest switching losses.
Future goals:
Modify the common mode elimination modulation to reduce switching loss.
Fig. 11. Space vector diagram for common mode elimination modulation.
This work was supported primarily by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC and the CURENT Industry Partnership Program.
Other US government and industrial sponsors of CURENT research are also gratefully acknowledged.