SRF Based Output Voltage Control of 3-Level 3-Phase 4-Leg AT-NPC Inverter

Öz

This paper proposes a synchronous reference frame (SRF) based high performance output voltage controller for the 3-level 3-phase 4-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) inverter operated in stand-alone mode. 3-phase inverters for stand-alone operation are required to provide 3-phase balanced nominal voltage under different load types such as unbalanced linear and non-linear loads. 3P4L inverters working with these types of load allow controlling zero sequence voltage by additional fourth leg. The main contribution of this work is the control of the 3-level 3P4L AT-NPC inverter with an LC-type filter modeled based on the output voltage and capacitor current feedback in the synchronous coordinate system. According to obtained capacitor current decoupled model, double loop PI controller is adopted to control the output voltage of the inverter. An inner capacitor current feedback loop is employed to provide fast dynamic response and active damping of the capacitor current. Finally, transient and steady state operation performance of the controller have been tested with PSIM simulation studies considering different load types. Simulation results validate that the proposed SRF based double loop PI controller ensure high dynamic response and high quality output voltage with less than 3% total harmonic distortion (THD) value for the 3-level 3P4L AT-NPC inverter.

Anahtar Kelimeler

• 3-level,4-leg,AT-NPC inverter,carrier-based PWM,voltage control

Kaynakça

1. [1] Kim J.H., and Sul S.K., “A carrier-based PWM method for three-phase four-leg voltage source converters”, IEEE Transaction on Power Electronics, 19: 66–75, (2004).
2. [2] Hava A.M. and Demirkutlu E., “Output voltage control of a four-leg inverter based three-phase UPS”, 2007 European Conference on Power Electronics and Applications, Aalborg, Denmark, 1–10, (2007).
3. [3] Zhang R., Boroyevich D., Prasad V.H., Mao H., Lee F. C. and Dubovsky S., “A three-phase inverter with a neutral leg with space vector modulation”, Applied Power Electronics Conference and Exposition, Atlanta, Georgia, 857–863, (1997).
4. [4] Schweizer M. and Kolar J.W., “Design and implementation of a highly efficient three-level T-type converter for low-voltage applications”, IEEE Transaction on Power Electronics, 28: 899–907, (2013).
5. [5] Kortenbruck J., Premgamone T., Leksawat S., Ortjohann E., Holtschulte D., Schmelter A., and Morton D., “Multilevel and 4-leg topology for smart grid inverter”, Energy Conference (Energycon), Leuven, Belgium, 1-6, (2016).
6. [6] Aghdam G.H., “Optimised active harmonic elimination technique for three-level T-type inverters”, IET Power Electronics, 6: 425–433, (2013).
7. [7] Schweizer M. and Kolar J.W., “High efficiency drive system with 3-level T-type inverter”, 14th European Conference on Power Electronics and Applications, Birmingham, UK, 1-10, (2011).
8. [8] Zhang L., Sun K., Huang L. and Igarashi S., “Comparison of RB-IGBT and Normal IGBT in T-Type Three-Level Inverter”, 15th European Conference on Power Electronics and Applications (EPE), Lille, France, 1-7, (2013).

9. [9] Avci E. and Ucar M., “Analysis and design of grid-connected 3-phase 3-level AT-NPC inverter for low-voltage applications”, Turkish Journal of Electrical Engineering & Computer Sciences, 25: 2464–2478, (2017).
10. [10] Kesler M. and Ozdemir E., “Synchronous-reference-frame-based control method for UPQC under unbalanced and distorted load conditions”, IEEE Transactions on Industrial Electronics, 58: 3967–3975, (2011).
11. [11] Sato Y., Ishizuka T., Nezu K. and Kataoka T., “A new control strategy for voltage-type PWM rectifiers to realize zero steady-state control error in input current”, IEEE Transactions on Industrial Applications, 34: 480–486, (1998).
12. [12] Zhang N., Tang H. and Yao C., “A systematic method for designing a PR controller and active damping of the LCL filter for single-phase grid-connected pv inverters”, Energies, 7: 3934–3954, (2014).
13. [13] Loh, P.C., Newman M. J., Zmood D.N. and Holmes D. G., “A comparative analysis of multiloop voltage regulation strategies for single and three-phase UPS systems”, IEEE Transaction on Power Electronics, 18: 1176–1185, (2003).
14. [14] Byen B. J., Choe J.M. and Choe G.H., “High-performance voltage controller design based on capacitor current control model for stand-alone inverters”, Journal of Electrical Engineering & Technology, 10: 709–718, (2015).
15. [15] Yi H.Z. and Jin S., “Study on control strategy for three-phase four-leg inverter power supply”, IEEE Industrial Electronics Society Conference (IECON), Busan, South Korea, 805–809, (2004).
16. [16] Demirkutlu E. and Hava A.M., “A scalar resonant-filter-bank-based output-voltage control method and a scalar minimum-switching-loss discontinuous PWM method for the four-leg-inverter-based three-phase four-wire power suply”, IEEE Transactions on Industrial Electronics, 45: 982–991, (2009).
17. [17] Erickson R.W. and Maksimovic D., “Fundamentals of Power Electronics”, Second Edition, Kluwer Academic Publishers, New York, (2001).