Control and Design of a Modular Multilevel Cascade BTB System Using Bidirectional Isolated DC/DC Converters

This paper discusses the control and design of the 6.6-kV back-to-back (BTB) system combining bidirectional isolated dc/dc converters and modular multilevel cascade pulsewidth modulation (PWM) converters. The system consists of multiple converter cells connected in cascade per phase at both front ends. Each converter cell consists of a bidirectional isolated medium-frequency dc/dc converter and two voltage-source H-bridge (single-phase full-bridge) PWM converters. Extremely low-voltage steps bring a significant reduction in harmonics and electromagnetic interference emissions to the BTB system. This paper designs, constructs, and tests a single-phase downscaled BTB system rated at 120 V and 3.3 kW to verify the viability and effectiveness, leading to the actual system.

[1]  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.

[2]  N. Okada,et al.  Development of a 6.6 kV - 1 MVA Transformerless Loop Balance Controller , 2007, 2007 IEEE Power Electronics Specialists Conference.

[3]  H. Akagi,et al.  Active-Power Control of Individual Converter Cells for a Battery Energy Storage System Based on a Multilevel Cascade PWM Converter , 2012, IEEE Transactions on Power Electronics.

[4]  H. Akagi,et al.  A Transformerless Energy Storage System Based on a Cascade PWM Converter with Star-Configuration , 2007, 2007 Power Conversion Conference - Nagoya.

[5]  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).

[6]  Hirofumi Akagi,et al.  Fault-Tolerant Operation of a Battery-Energy-Storage System Based on a Multilevel Cascade PWM Converter With Star Configuration , 2010, IEEE Transactions on Power Electronics.

[7]  Alan J. Watson,et al.  Control Challenges and Solutions for a Multi-Cellular Converter for Use in Electricity Networks , 2009 .

[8]  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.

[9]  Alan J. Watson,et al.  Experimental implementation of a multilevel converter for power system integration , 2009, 2009 IEEE Energy Conversion Congress and Exposition.

[10]  Alfred Rufer,et al.  Uniflex-PM – a Key-Enabling Technology for Future European Electricity Networks , 2009 .

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

[12]  L. Heinemann,et al.  An actively cooled high power, high frequency transformer with high insulation capability , 2002, APEC. Seventeenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.02CH37335).

[13]  H. Akagi,et al.  State-of-Charge (SOC)-Balancing Control of a Battery Energy Storage System Based on a Cascade PWM Converter , 2009, IEEE Transactions on Power Electronics.

[14]  H. Akagi,et al.  A Bidirectional Isolated DC–DC Converter as a Core Circuit of the Next-Generation Medium-Voltage Power Conversion System , 2007, IEEE Transactions on Power Electronics.