3-Level T-type Inverter Operation Method Using Level Change

  • Kim, Tae-Hun (Dept. of Electrical, Electronic and Control Engineering, Hankyong National University) ;
  • Lee, Woo-Cheol (Dept. of Electrical, Electronic and Control Engineering, Hankyong National University, Institute for information technology convergence)
  • Received : 2017.03.08
  • Accepted : 2017.09.26
  • Published : 2018.01.01


In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

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Fig. 1. Operation areas based on phase angle of outputvoltage and inductor current in A-phase

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Fig. 2. 3-phase 2-level VSC circuit

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Fig. 3. 3LT VSC circuit

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Fig. 4. Block diagram of proposed method sequence

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Fig. 5. Simulation waveform (fs = 10 kHz, Rload = 48 Ω) :(a) output phase voltage Van, Vbn, and Vcn, (b)inductor current iaL, ibL, and icL, (c) 2-level A-phaseloss calculation Pa2 and 3-level A-phase losscalculation Pa3, (d) Pa3 - Pa2

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Fig. 6. Simulation efficiency with R load (3 kW, 6 kW)

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Fig. 7. 2-level operation mode waveform: Ch1 outputvoltage, Van (250 V/div), Ch2 inverter voltage, Vainv(250 V/div), Ch3 inductor current, iaL (10 A/div)

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Fig. 8. 3-level operation mode waveform: Ch1 outputvoltage, Van (250 V/div), Ch2 inverter voltage, Vainv(250 V/div), Ch3 inductor current, iaL (10 A/div)

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Fig. 9. Proposed method waveform: Ch1 output voltage,Van (250 V/div), Ch2 inverter voltage, Vainv (250V/div), Ch3 inductor current, iaL (10 A/div), Ch4Pa3 ? Pa2 value (5 W/div)

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Fig. 10. Proposed method waveform with RL load: Ch1output voltage, Van (250 V/div), Ch2 invertervoltage, Vainv (250 V/div), Ch3 load current, iLoad(10 A/div)

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Fig. 11. Experiment efficiency with R load (3 kW, 6 kW)

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Fig. 12. Experiment efficiency with R load (1 kW, 2 kW)

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Fig. 13. Experiment efficiency with RL load (1 kW, 2 kW)

Table 1. 2-level VSC switching and conduction losses

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Table 2. 3LT VSC switching and conduction losses

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Table 3. System parameter

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Supported by : National Research Foundation of Korea(NRF)


  1. P. Cortes, G. Ortiz, J. I. Yuz, J. Rodriguez, S. Vazquez, and L. G. Franquelo, "Model predictive control of an inverter with output lc filter for ups applications," Industrial Electronics, IEEE Transactions on, vol. 56, no. 6, pp. 1875-1883, 2009.
  2. L. G. Franquelo et al., "The age of multilevel converters arrives," IEEE Ind. Electron. Mag., vol. 2, no. 2, pp. 28-39, Jun. 2008.
  3. J. Rodriguez, S. Bernet, B. Wu, J. O. Pontt, and S. Kouro, "Multilevel Voltage-source-converter Topologies for Industrial Medium-voltage Drives," IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 2930-2945, Dec. 2007.
  4. H. Abu-Rub, J. Holtz, J. Rodriguez, and G. Baoming, "Medium voltage multilevel converters - State of the art, challenges and requirements in industrial applications," IEEE Trans. Ind. Electron, vol. 57, no. 8, pp. 2581-2596, Aug. 2010.
  5. T. Bruckner, S. Bernet, and H. Guldner, "The active NPC converter and its loss-balancing control," IEEE Trans. Ind. Electron., vol. 52, no. 3, pp. 855-868, Jun. 2005.
  6. F. Khoucha, M. S. Lagoun, A. Kheloui, and M. El Hachemi Benbouzid, "A comparison of symmetrical and asymmetrical three-phase H-bridge multilevel inverter for DTC induction motor drives," IEEE Trans. Energy Convers., vol. 26, no. 1, pp. 64-72, Mar. 2011.
  7. M. Schweizer and J. W. Kolar, "Design and implementation of a highly ef- ficient 3-level T-type converter for low-voltage applications," IEEE Trans. Power Electron., vol. 28, no. 2, pp. 889-907, Feb. 2013.
  8. Y. Kashihara and J. Itoh, "The performance of the multilevel converter topologies for PV inverter," in Proc. CIPS, Beijing, China, pp. 1-6, Mar. 2012,
  9. K. Komatsu, "New IGBT modules for advanced neutral-point-clamped 3-level power converters" International Power Electronics Conference (IPEC), pp. 523-527, 2010.
  10. S-M. Shin, J-H. Ahn, and B-K. Lee, "Maximum Efficiency Operation of Three-Level T-type Inverter for Low-Voltage and Low-Power Home Appliances," Journal of Electrical Engineering & Technology, vol. 10, no. 2, pp. 586-594, 2015.
  11. J. W. Kolar, "High efficiency drive system with 3- level T-type inverter," Proc. EPE Appl., pp. 1-10, Aug. 2011.
  12. R. Teichmann and S. Bernet, "A comparison of threelevel converters versus two-level converters for lowvoltage drives, traction, and utility applications," IEEE Trans. Ind. Appl., vol. 41, pp. 855-865, May-June 2005.
  13. Alemi, Payam, and Dong-Choon Lee. "A Generalized Loss Analysis Algorithm of Power Semiconductor Devices in Multilevel NPC Inverters," Journal of Electrical Engineering and Technology, vol.9, no.6, pp. 2168-2180, 2014.
  14. K. Zhang, Y. Kang, J. Xiong, and J. Chen, "Direct repetitive control of SPWM inverters for UPS purpose," IEEE Trans. Power Electron., vol. 18, no. 3, pp. 784-792, May 2003.
  15. Bai Baodong, Chen Dezhi, "Inverter IGBT Loss Analysis and Calculation," Industrial Technology (ICIT), 2013 IEEE International Conference on. IEEE, pp 563-569, 2013.
  16. W. Srirattanawichaikul, S. Premrudeepreechacharn, Y. Kumsuwan, "Modified Unipolar Carrier-Based PWM Strategy for Three-level Neutral-Point-Clamped Voltage Source Inverters," Journal of Electrical Engineering & Technology, vol. 9, no. 2, pp. 489-500, March 2014.