Improved Ladder Wave Modulation of Circulating Current Suppressing Control Strategy of MMC

Pinggang Song, Yunfeng Li, Lina Wang

College of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang City, Jiangxi Province, China.

DOI: 10.4236/epe.2013.54B223                

Abstract

This paper partitions the arm current of MMC into uncontrollable current and controllable current. The former is determined by the load that can’t be controlled by taking any control strategy. The later caused by the unbalanced total inserted voltage of three arms can be controlled by some improved algorithms. The conclusion based on the researching the essence of circulating current is reached that change the number of the inserted sub-modules in each phase can suppress the circulating current. Combined with the improved ladder wave modulation, a novel circulating current suppression strategy particularly for the inverter station is developed. The improved strategy can adapt to load changes and reduce the circulating current and output voltage THD of MMC ac terminals greatly without increasing any peripheral circuits. Finally, the simulation model of 100 submodules in each phase is constructed in MATLAB and the simulation results verify the correctness and effectiveness of the modified control algorithm.

Keywords

Modular Multilevel Converter; High Voltage Direct Current Transmission; Circulating Current; Module Changing Selection Algorithm; Double Frequency Negative Component

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	A. Lesnicar and R. Marquardt, “An Innovative Modular Multilevel Converter Topology Suitable for a Wide Power Range,” IEEE Power Technology Conference Proceedings, Bologna Italy: IEEE, 2003, p. 6.
[2]	A. Antonopoulos, L. Angquist and H. P. Nee, “On Dynamics and Voltage Control of the Modular Multilevel Converter,” European Power electronics and Applications Conference, Barcelona Spain: IEEE 2009, pp. 1-10.
[3]	M. Glinka and R. Marquardt, “A New Ac/Ac Multi-level Converter Family,” IEEE Transactions on Industrial Electronics, Vol. 52, No. 3, 2005, pp. 662-669. doi:10.1109/TIE.2005.843973
[4]	M. Hagiwara, K. Nishimura, “A Medium Voltage Motor Drive with a Modular Multilevel PWM Inverter,” IEEE Transactions on Power Electronics, Vol. 25, No. 7, 2010, pp. 1786-1799. doi:10.1109/TPEL.2010.2042303
[5]	M. Hagiwara and H. Akagi, “PWM Control and Experiment of Modular Multilevel Converter,” in Proceedings IEEE Power Electronics Specialists Conference, Rhodes Greece, 2008, pp. 154-161.
[6]	Q. Tu and Z. Xu, “Impact of Sampling Frequency on Harmonic Distortion for Modular Multilevel Converter,” IEEE Transactions on Power Delivery, Vol. 26, No. 1, 2011, pp. 298-306. doi:10.1109/TPWRD.2010.2078837
[7]	J. Peralta and H. Saad, “Detaled and Averaged Models for a 401-level MMC-HVDC System,” IEEE Transactions on Power Delivery, Vol. 27, No. 3, 2012, pp. 1501-1508.
[8]	S. Allebrod, R. Hamerski and R. Marquardt, “New Transformerless, Scalable Modular Multilevel Converters for HVDC Transmission,” in Proceedings IEEE Power Electronics Specialists Conference, Rhodes Greece, 2008, pp. 174-179.
[9]	R. Marquardt, “Modular Multilevel Converter：An Universal Concept for HVDC-networks and Extended DC-bus-applications,” International Power Electronics Conference (IPEC), Sapporo Japan：Institute of Electrical and Electronics Engineers，2010, pp. 502-507．
[10]	S. Robner, S. Bernet and M. Hiller, “Modeling, Simulation and Analysis of a Modular Multilevel Converter for Medium Voltage Applications,” IEEE International Conference on Industrial Technology (ICIT), Viña del Mar Chile：Institute of Electrical and Electronics Engineers, 2010, pp. 775-782.
[11]	S. Rohner，S.Bernet，M. Hiller，etc., “Analysis and Simulation of a 6 Kv,6 MVA Modular Multilevel Converter,” 35th Annual Conference of IEEE on Industrial Electronics, Porto Portugal：Institute of Electrical and Electronics Engineers，2009, pp. 225-230．
[12]	Q. Tu, Z. Xu and L. Xu, “Reduced Switching Frequency Modulation and Circulating Current Suppression for Modular Multilevel Converters,” IEEE Transactions on Power Delivery, Vol. 23, No. 3, 2011, pp. 2009-2017.
[13]	Z. X. Li, P. Wang and H. B. Zhu, “An Improved Pulse Width Modulation Method for Chopper-Cell-Based Modular Multilevel Converters,” IEEE Transactions on Power Electronics, Vol. 27, No. 8, 2012, pp. 3472-3481. doi:10.1109/TPEL.2012.2187800