Adaptive Droop Control Strategy for Load Sharing and Circulating Current Minimization in Low-Voltage Standalone DC Microgrid

This paper addresses load current sharing and circulating current issues of parallel-connected DC-DC converters in low-voltage DC microgrid. Droop control is the popular technique for load current sharing in DC microgrid. The main drawbacks of the conventional droop method are poor current sharing and drop in dc grid voltage due to the droop action. Circulating current issue will also arise due to mismatch in the converters output voltages. In this work, a figure of merit called droop index (DI) is introduced in order to improve the performance of dc microgrid, which is a function of normalized current sharing difference and losses in the output side of the converters. This proposed adaptive droop control method minimizes the circulating current and current sharing difference between the converters based on instantaneous virtual resistance Rdroop. Using Rdroop shifting, the proposed method also eliminates the tradeoff between current sharing difference and voltage regulation. The detailed analysis and design procedure are explained for two DC-DC boost converters connected in parallel. The effectiveness of the proposed method is verified by detailed simulation and experimental studies.

[1]  Wei Jiang,et al.  Active Current Sharing and Source Management in Fuel Cell–Battery Hybrid Power System , 2010, IEEE Transactions on Industrial Electronics.

[2]  S. R. Bull,et al.  Renewable energy today and tomorrow , 2001, Proc. IEEE.

[3]  Bo-Hyung Cho,et al.  A novel droop method for converter parallel operation , 2002 .

[4]  Federico Delfino,et al.  Optimal Control and Operation of Grid-Connected Photovoltaic Production Units for Voltage Support in Medium-Voltage Networks , 2014, IEEE Transactions on Sustainable Energy.

[5]  B. G. Fernandes,et al.  Distributed Control to Ensure Proportional Load Sharing and Improve Voltage Regulation in Low-Voltage DC Microgrids , 2013, IEEE Transactions on Power Electronics.

[6]  B. G. Fernandes,et al.  Modified droop controller for paralleling of dc-dc converters in standalone dc system , 2012 .

[7]  Narsa Reddy Tummuru,et al.  Multifunctional VSC Controlled Microgrid Using Instantaneous Symmetrical Components Theory , 2014, IEEE Transactions on Sustainable Energy.

[8]  B Renders,et al.  A Control Strategy for Islanded Microgrids With DC-Link Voltage Control , 2011, IEEE Transactions on Power Delivery.

[9]  Byungcho Choi Comparative study on paralleling schemes of converter modules for distributed power applications , 1998, IEEE Trans. Ind. Electron..

[10]  Marian K. Kazimierczuk,et al.  Pulse-Width Modulated DC-DC Power Converters , 2008 .

[11]  Enrico Tironi,et al.  Design and Development of a LV Test Facility for DC Active Distribution System , 2009 .

[12]  A. Sannino,et al.  An Adaptive Control System for a DC Microgrid for Data Centers , 2007, IEEE Transactions on Industry Applications.

[13]  A. Bonfiglio,et al.  The Smart Polygeneration Microgrid test-bed facility of Genoa University , 2012, 2012 47th International Universities Power Engineering Conference (UPEC).

[14]  Milan M. Jovanovic,et al.  Analysis, design, and performance evaluation of droop current-sharing method , 2000, APEC 2000. Fifteenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.00CH37058).

[15]  Fred C. Lee,et al.  A classification and evaluation of paralleling methods for power supply modules , 1999, 30th Annual IEEE Power Electronics Specialists Conference. Record. (Cat. No.99CH36321).

[16]  Frede Blaabjerg,et al.  Autonomous Operation of Hybrid Microgrid With AC and DC Subgrids , 2011, IEEE Transactions on Power Electronics.

[17]  Juan C. Vasquez,et al.  Hierarchical Control of Droop-Controlled AC and DC Microgrids—A General Approach Toward Standardization , 2009, IEEE Transactions on Industrial Electronics.

[18]  Richard Duke,et al.  DC-Bus Signaling: A Distributed Control Strategy for a Hybrid Renewable Nanogrid , 2006, IEEE Transactions on Industrial Electronics.

[19]  Hiroaki Kakigano,et al.  Low-Voltage Bipolar-Type DC Microgrid for Super High Quality Distribution , 2010, IEEE Transactions on Power Electronics.

[20]  Juan C. Vasquez,et al.  An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication With DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy , 2014, IEEE Transactions on Power Electronics.

[21]  Mahesh K. Mishra,et al.  Circulating current minimization and current sharing control of parallel boost converters based on Droop Index , 2013, 2013 9th IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives (SDEMPED).

[22]  Dushan Boroyevich,et al.  Design of parallel sources in DC distributed power systems by using gain-scheduling technique , 1999, 30th Annual IEEE Power Electronics Specialists Conference. Record. (Cat. No.99CH36321).

[23]  F. C. Lee,et al.  Modeling and dynamic analysis of paralleled DC/DC converters with master-slave current sharing control , 1996, Proceedings of Applied Power Electronics Conference. APEC '96.

[24]  Frank L. Lewis,et al.  Distributed adaptive droop control for DC microgrids , 2014, 2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014.

[25]  Ke-Horng Chen,et al.  Adaptive Droop Resistance Technique for Adaptive Voltage Positioning in Boost DC–DC Converters , 2011, IEEE Transactions on Power Electronics.

[26]  M. Kazimierczuk Pulse-Width Modulated DC-DC Power Converters: Kazimierczuk/Pulse-width Modulated DC-DC Power Converters , 2008 .

[27]  Issa Batarseh,et al.  Investigation of the output droop characteristics of parallel-connnected DC-DC converters , 1994, Proceedings of 1994 Power Electronics Specialist Conference - PESC'94.

[28]  M. J. Hossain,et al.  Nonlinear Current Control Scheme for a Single-Phase Grid-Connected Photovoltaic System , 2014, IEEE Transactions on Sustainable Energy.

[29]  Prasenjit Basak,et al.  A literature review on integration of distributed energy resources in the perspective of control, protection and stability of microgrid , 2012 .

[30]  H. Kakigano,et al.  Distribution Voltage Control for DC Microgrids Using Fuzzy Control and Gain-Scheduling Technique , 2013, IEEE Transactions on Power Electronics.