Research on Unbalanced-Load Correction Capability of Two Power Electronic Transformer Topologies

Compared with conventional power transformer, power electronic transformer (PET) has many merits and an increasing possibility to replace it in the future. In this paper, the unbalanced-load correction capability of two H-bridge based three-phase three-stage modular PET topologies, the separate-phase-connection (SPC) one and the cross-phase-connection (CPC) one, are analyzed and compared. Both of the SPC and CPC consist of three stages: a modular multilevel ac-dc input stage, an isolation stage with several independent modular dual active bridge (DAB) dc-dc converters, and a dc-ac output stage with single-phase-inverter parallel-connected structure. Based on the control strategy, it is found that the SPC is suitable for dealing with full-range unbalanced load under the condition of increasing the input-stage current stress. For the SPC feeding, one load or three loads with identical power polarity, the current stress shall be theoretically increased up to 115% of the rated one, while the percentage is 153% when the SPC feeds three loads with different power polarity. On the contrary, the CPC is only suitable for dealing with partial unbalanced-load conditions. Extendedly, the third so-called full-range-power auto-balance PET is proposed to deal with unbalanced load, the performance of which is verified by simulation results. A downscaled prototype for SPC and CPC is built and tested. Experimental results verify the unbalanced-load correction performance of SPC and CPC.

[1]  M. Takasaki,et al.  A Transformerless D-STATCOM Based on a Multivoltage Cascade Converter Requiring No DC Sources , 2012, IEEE Transactions on Power Electronics.

[2]  A Q Huang,et al.  The Future Renewable Electric Energy Delivery and Management (FREEDM) System: The Energy Internet , 2011, Proceedings of the IEEE.

[3]  Prasad Enjeti,et al.  Analysis and design of electronic transformers for electric power distribution system , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[4]  N. Hugo,et al.  Power electronics traction transformer , 2007, 2007 European Conference on Power Electronics and Applications.

[5]  Hui Li,et al.  High-Frequency Transformer Isolated Bidirectional DC–DC Converter Modules With High Efficiency Over Wide Load Range for 20 kVA Solid-State Transformer , 2011, IEEE Transactions on Power Electronics.

[6]  T. M. Jahns,et al.  Evolving and Emerging Applications of Power Electronics in Systems , 2013, IEEE Journal of Emerging and Selected Topics in Power Electronics.

[7]  Rolando Burgos,et al.  Review of Solid-State Transformer Technologies and Their Application in Power Distribution Systems , 2013, IEEE Journal of Emerging and Selected Topics in Power Electronics.

[8]  Fei Wang,et al.  Design and Demonstration of a 3.6-kV–120-V/10-kVA Solid-State Transformer for Smart Grid Application , 2014, IEEE Transactions on Power Electronics.

[9]  Alex Q. Huang,et al.  High-voltage high-frequency transformer design for a 7.2kV to 120V/240V 20kVA solid state transformer , 2010, IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society.

[10]  Frede Blaabjerg,et al.  Future on Power Electronics for Wind Turbine Systems , 2013, IEEE Journal of Emerging and Selected Topics in Power Electronics.

[11]  Jonathan W. Kimball,et al.  Solid-State Transformer Architecture Using AC–AC Dual-Active-Bridge Converter , 2013, IEEE Transactions on Industrial Electronics.

[12]  Jih-Sheng Lai,et al.  Multilevel intelligent universal transformer for medium voltage applications , 2005, Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005..

[13]  Fei Wang,et al.  Wind Energy System With Integrated Functions of Active Power Transfer, Reactive Power Compensation, and Voltage Conversion , 2013, IEEE Transactions on Industrial Electronics.

[14]  Hao Yuan,et al.  Research on voltage and power balance control for cascaded modular solid-state transformer , 2011, IEEE Transactions on Power Electronics.

[15]  A. Huang,et al.  Comparison of 10-kV SiC power devices in solid-state transformer , 2010, 2010 IEEE Energy Conversion Congress and Exposition.

[16]  Ned Mohan,et al.  A novel integrated three-phase, switched multi-winding power electronic transformer converter for wind power generation system , 2009, 2009 35th Annual Conference of IEEE Industrial Electronics.

[17]  H. Akagi,et al.  Control and Performance of a Transformerless Cascade PWM STATCOM With Star Configuration , 2007, IEEE Transactions on Industry Applications.

[18]  Hirofumi Akagi.  Classification, Terminology, and Application of the Modular Multilevel Cascade Converter (MMCC) , 2011 .

[19]  Jinjun Liu,et al.  Control of a three-stage three-phase cascaded modular power electronic transformer , 2013, 2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

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

[21]  H. Akagi,et al.  A Transformerless Energy Storage System Based on a Cascade Multilevel PWM Converter With Star Configuration , 2008, IEEE Transactions on Industry Applications.

[22]  D.M. Divan,et al.  A three-phase soft-switched high power density DC/DC converter for high power applications , 1988, Conference Record of the 1988 IEEE Industry Applications Society Annual Meeting.

[23]  A. Agarwal,et al.  10 kV/120 A SiC DMOSFET half H-bridge power modules for 1 MVA solid state power substation , 2011, 2011 IEEE Electric Ship Technologies Symposium.

[24]  Alex Q. Huang,et al.  Voltage and Power Balance Control for a Cascaded H-Bridge Converter-Based Solid-State Transformer , 2013, IEEE Transactions on Power Electronics.

[25]  Alex Q. Huang,et al.  Current Sensorless Power Balance Strategy for DC/DC Converters in a Cascaded Multilevel Converter Based Solid State Transformer , 2014, IEEE Transactions on Power Electronics.

[26]  Yuan-Kang Wu,et al.  Taiwan's First Large-Scale Offshore Wind Farm Connection—A Real Project Case Study With a Comparison of Wind Turbine , 2011, IEEE Transactions on Industry Applications.

[27]  Jinjun Liu,et al.  Comparisons of different three-stage three-phase cascaded modular topologies for Power Electronic Transformer , 2012, 2012 IEEE Energy Conversion Congress and Exposition (ECCE).

[28]  R. Ayyanar,et al.  A DC–DC Multiport-Converter-Based Solid-State Transformer Integrating Distributed Generation and Storage , 2013, IEEE Transactions on Power Electronics.

[29]  S. D. Sudhoff,et al.  A Power Electronic-Based Distribution Transformer , 2002, IEEE Power Engineering Review.

[30]  P. Stefanutti,et al.  Power Electronic Traction Transformer-Low Voltage Prototype , 2013, IEEE Transactions on Power Electronics.

[31]  Stefano Bifaretti,et al.  Advanced Power Electronic Conversion and Control System for Universal and Flexible Power Management , 2011, IEEE Transactions on Smart Grid.

[32]  Li Wang,et al.  Combining the Wind Power Generation System With Energy Storage Equipment , 2009, IEEE Transactions on Industry Applications.

[33]  Jinjun Liu,et al.  A Novel DC Voltage Control Method for STATCOM Based on Hybrid Multilevel H-Bridge Converter , 2013, IEEE Transactions on Power Electronics.