A novel SVM algorithm for reducing oscillations in cascaded H-bridge multilevel inverters

Cascaded H-bridge inverters have been selected as one of the preferred power converter topologies for high-voltage, high-power applications. However, undesired oscillations could occur in the H-bridge inverter drive system particularly under light load conditions, which would cause high voltage or current stress on the motor and inverter. In this paper, the mechanism of the oscillations is analyzed and a novel mitigation method is proposed. The mitigation involves a simple inverter output voltage adjustment in the space vector PWM control in real time, such that the oscillation loop would be broken, leading to effective suppression of the oscillations. The proposed method features simple algorithm and easy implementation requiring only one voltage measurement per phase for any level H-bridge inverter. Simulation and experimental results are provided to demonstrate the efficiency of the method.

[1]  Yoshitaka Iwaji,et al.  A new PWM method to reduce beat phenomenon in large capacity inverters with low-switching frequency , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[2]  Bin Wu,et al.  A general space vector PWM control algorithm for multilevel inverters , 2003, Eighteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2003. APEC '03..

[3]  R.S. Colby,et al.  Simplified model and corrective measures for induction motor instability caused by PWM inverter blanking time , 1990, 21st Annual IEEE Conference on Power Electronics Specialists.

[4]  Wing Hong Lau,et al.  Analytical solution to harmonic characteristics of PWM H-bridge converters with dead time , 1998, ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187).

[5]  Frede Blaabjerg,et al.  Improved modulation techniques for PWM-VSI drives , 1997, IEEE Trans. Ind. Electron..

[6]  Li Li,et al.  Multilevel space vector PWM technique based on phase-shift harmonic suppression , 2000, APEC 2000. Fifteenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.00CH37058).

[7]  M. Lockwood.  Simulation of unstable oscillations in PWM variable-speed drives , 1988 .

[8]  M. Cade.  Improvement of induction machine stability by modulation techniques , 1994 .

[9]  C.O. Nwankpa,et al.  A new type of STATCOM based on cascading voltage source inverters with phase-shifted unipolar SPWM , 1998, Conference Record of 1998 IEEE Industry Applications Conference. Thirty-Third IAS Annual Meeting (Cat. No.98CH36242).