A dual-mode cascaded H-bridge multilevel inverter for improving THD
- 22 Downloads
Conventionally, multilevel inverters utilise multi-carrier pulse width modulation or multi-stepped (staircase) modulation to produce high-power quality waveforms. Though multi-carrier modulation schemes reduce total harmonic distortion (THD), they lead to considerable switching loss at higher modulation indexes. The staircase modulation, which operates at low switching frequencies, has a limitation of excessive high THD at low modulation indexes, making it unsuitable at lower modulation indexes. The proposed modulation technique blends the advantages of multi-carrier pulse width modulation and staircase modulation to improve the THD and reduce the switching losses over a wide range of modulation indexes. The proposed multilevel inverter employs a modified level-shifted multi-carrier modulation at lower modulation indexes and shifts to sinusoidally approximated multi-stepped at moderate and higher modulation indexes. The carrier frequency of the multi-carrier modulation is varied according to the switching loss analysis to further enhance the THD. A 1 KW prototype was built to confirm the practicality of the proposed method.
KeywordsAsymmetric cascaded H-bridge Field programmable gate arrays Multi-carrier modulation Multi-stepped modulation and switching loss
The authors express sincere gratitude to Dr. Jaison Mathew, Associate professor, Department of Electrical and Electronics Engineering, Government Engineering College Thrissur, for his invaluable help in the hardware design of the circuit.
- 18.Francis R, Meganathan D (2016) Efficient 81-level sinusoidal and modified sinusoidal multi-stepped inverter. In: 8th IET international conference on power electronics machines and drives (PEMD 2016), pp 1–6. IETGoogle Scholar
- 20.Maswood AI (2008) A switching loss study in spwm IGBT inverter. In: IEEE 2nd International power and energy conference (PECon 2008), pp 609–613Google Scholar
- 22.Alimeling JH, Hammer WP (1999) PLECS-piece-wise linear electrical circuit simulation for Simulink. In: Proceedings of the IEEE 1999 international conference on power electronics and drive systems. PEDS’99 (Cat. No. 99TH8475), vol 1, pp 355–360Google Scholar
- 23.Mohan N, Undeland TM (2007) Power electronics: converters, applications, and design. Wiley, New YorkGoogle Scholar
- 25.Un E, Hava AM (2007) A near state PWM method with reduced switching frequency and reduced common mode voltage for three-phase voltage source inverters. In; 2007 IEEE international electric machines and drives conference, vol 1, pp 235–240Google Scholar