A Grid Synchronization Method for Droop-Controlled Distributed Energy Resource Converters

The microgrid is a very effective way of integrating various distributed generation resources into the ac power system. To provide electric power of high reliability, the converters in the microgrid often rely on autonomous droop control methods to reduce their dependence on communication and need to operate in both the islanded mode and the grid-connected mode. In this paper, a grid synchronization method for a multiconverter distributed generation system is proposed. The proposed grid synchronization method allows multiple droop-controlled converters to adjust the frequency, phase, and amplitude of their output voltages to prepare for grid connection. The entire synchronization process can be executed with very limited communication requirement. This paper provides detailed explanation on the proposed grid synchronization method. Experimental test results are presented to validate the effectiveness of the proposed method.

[1]  Josep M. Guerrero,et al.  Mode Adaptive Droop Control With Virtual Output Impedances for an Inverter-Based Flexible AC Microgrid , 2011, IEEE Transactions on Power Electronics.

[2]  Thomas G. Habetler,et al.  A space vector-based rectifier regulator for AC/DC/AC converters , 1993 .

[3]  R. Adapa,et al.  Control of parallel connected inverters in stand-alone AC supply systems , 1991, Conference Record of the 1991 IEEE Industry Applications Society Annual Meeting.

[4]  Po-Tai Cheng,et al.  A new droop control method for the autonomous operation of distributed energy resource interface converters , 2010 .

[5]  S.M. Silva,et al.  PLL structures for utility connected systems , 2001, Conference Record of the 2001 IEEE Industry Applications Conference. 36th IAS Annual Meeting (Cat. No.01CH37248).

[6]  P.W. Lehn,et al.  Autonomous load sharing of voltage source converters , 2005, IEEE Transactions on Power Delivery.

[7]  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.

[8]  Yasser Abdel-Rady I. Mohamed,et al.  Hierarchical Control System for Robust Microgrid Operation and Seamless Mode Transfer in Active Distribution Systems , 2011, IEEE Transactions on Smart Grid.

[9]  Jih-Sheng Lai,et al.  Design of Parallel Inverters for Smooth Mode Transfer Microgrid Applications , 2009, 2009 Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition.

[10]  Frede Blaabjerg,et al.  Overview of Control and Grid Synchronization for Distributed Power Generation Systems , 2006, IEEE Transactions on Industrial Electronics.

[11]  F. Blaabjerg,et al.  Connection and disconnection transients for micro-grids under unbalance load condition , 2011, Proceedings of the 2011 14th European Conference on Power Electronics and Applications.

[12]  Deepak Divan,et al.  Control of distributed UPS systems , 1994, Proceedings of 1994 Power Electronics Specialist Conference - PESC'94.

[13]  V. Blasko,et al.  Operation of a phase locked loop system under distorted utility conditions , 1997 .

[14]  Timothy C. Green,et al.  Real-World MicroGrids-An Overview , 2007, 2007 IEEE International Conference on System of Systems Engineering.

[15]  Se-Kyo Chung,et al.  A phase tracking system for three phase utility interface inverters , 2000 .

[16]  R. Iravani,et al.  Microgrids management , 2008, IEEE Power and Energy Magazine.

[17]  M. Liserre,et al.  Generalized controller for small wind turbines working grid-connected and stand-alone , 2011, 2011 International Conference on Clean Electrical Power (ICCEP).

[18]  J. Rocabert,et al.  Intelligent Connection Agent for Three-Phase Grid-Connected Microgrids , 2011, IEEE Transactions on Power Electronics.

[19]  Josep M. Guerrero,et al.  Output impedance design of parallel-connected UPS inverters with wireless load-sharing control , 2005, IEEE Transactions on Industrial Electronics.

[20]  R.H. Lasseter,et al.  Autonomous control of microgrids , 2006, 2006 IEEE Power Engineering Society General Meeting.