Real-Time Calculation of Switching Angles Minimizing THD for Multilevel Inverters With Step Modulation

Multilevel inverters have been widely applied in industries. A family of optimal pulsewidth modulation (PWM) methods for multilevel inverters, such as step modulation, can generate output voltage with less harmonic distortion than popular modulation strategies, such as the carrier-based sinusoidal PWM or the space vector PWM. However, some drawbacks limit the application of optimal PWM. One of such crucial drawback is that the optimal switching angles could not be calculated in real-time and one has to rely on lookup tables with precalculated angles. We propose a novel real-time algorithm for calculating switching angles that minimizes total harmonic distortion (THD) for step modulation. We give a mathematical proof that the output voltage has the minimum THD. We implemented the algorithm on a digital signal processor and provide experimental results that verify the performance of the proposed algorithm.

[1]  F. L. Luo,et al.  Trinary hybrid multilevel inverter used in STATCOM with unbalanced voltages , 2005 .

[2]  Jan T. Bialasiewicz,et al.  Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey , 2006, IEEE Transactions on Industrial Electronics.

[3]  P. Pillay,et al.  Multilevel selective harmonic elimination PWM technique in series-connected voltage inverters , 1998, Conference Record of 1998 IEEE Industry Applications Conference. Thirty-Third IAS Annual Meeting (Cat. No.98CH36242).

[4]  Zhong Du,et al.  An Optimal Combination Modulation Strategy for a Seven-level Cascade Multilevel Converter Based STATCOM , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[5]  Fang Zheng Peng,et al.  Multilevel inverters: a survey of topologies, controls, and applications , 2002, IEEE Trans. Ind. Electron..

[6]  J. Chiasson,et al.  Elimination of harmonics in a multilevel converter using the theory of symmetric polynomials and resultants , 2003, 42nd IEEE International Conference on Decision and Control (IEEE Cat. No.03CH37475).

[7]  Fei Liu,et al.  Cascade multilevel inverter with phase-shift SPWM and its application in STATCOM , 2004, 30th Annual Conference of IEEE Industrial Electronics Society, 2004. IECON 2004.

[8]  Toshifumi Ise,et al.  A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system , 2005 .

[9]  L.M. Tolbert,et al.  Harmonic optimization of multilevel converters using genetic algorithms , 2004, IEEE Power Electronics Letters.

[10]  Leon M. Tolbert,et al.  Multilevel converters for large electric drives , 1999 .

[11]  Johann W. Kolar,et al.  A novel multicell DC-AC converter for applications in renewable energy systems , 2002, IEEE Trans. Ind. Electron..

[12]  Pedro Ibañez,et al.  Intelligent PV Module for Grid-Connected PV Systems , 2006, IEEE Transactions on Industrial Electronics.

[13]  Tian-Hua Liu,et al.  Optimum harmonic reduction with a wide range of modulation indexes for multilevel converters , 2002, IEEE Trans. Ind. Electron..

[14]  Cassiano Rech,et al.  Hybrid Multilevel Converters: Unified Analysis and Design Considerations , 2007, IEEE Transactions on Industrial Electronics.

[15]  A.R. Beig,et al.  A novel fifteen level inverter for photovoltaic power supply system , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[16]  Dong-Seok Hyun,et al.  A simple method for acquiring the conducting angle in a multilevel cascaded inverter using step pulse waves , 2005 .

[17]  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).

[18]  Zhong Du,et al.  A unified approach to solving the harmonic elimination equations in multilevel converters , 2004, IEEE Transactions on Power Electronics.

[19]  Jorge Pontt,et al.  A new modulation method to reduce common-mode voltages in multilevel inverters , 2004, IEEE Transactions on Industrial Electronics.

[20]  P. N. Tekwani,et al.  Twelve-Sided Polygonal Voltage Space Vector Based Multilevel Inverter for an Induction Motor Drive With Common-Mode Voltage Elimination , 2007, IEEE Transactions on Industrial Electronics.