Transient Oscillations Analysis and Modified Control Strategy for Seamless Mode Transfer in Micro-Grids: A Wind-PV-ES Hybrid System Case Study

Tengfei Zhang, Dong Yue, Michael J. O’Grady and Gregory M. P. O’Hare
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Tengfei Zhang: College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Dong Yue: College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Michael J. O’Grady: School of Computer Science, University College Dublin, Dublin 4, Ireland
Gregory M. P. O’Hare: School of Computer Science, University College Dublin, Dublin 4, Ireland

Energies, 2015, vol. 8, issue 12, 1-20

Abstract: With the rapid development of the micro-grid associated with new and clean energies, the smooth switching between grid-connected and islanded operation modes of the micro-grid is a key issue that needs to be addressed urgently. In traditional solutions, V/f (Voltage/frequency) control is adopted for the master micro sources when the micro-grid works in islanded mode, while PQ (real and reactive power) control is adopted when in grid-connected mode. However, when the two controllers switch when mode transfer occurs, transient oscillations usually occur and thereafter the dynamic response will be degraded. This paper considers an archetypical micro-grid with Wind-PV-ES (Wind, Photovoltaic and Energy Storage) hybrid system, which forms the basis of our case study. The underlying reason for such transient oscillation is analyzed in this paper. Thereafter a modified control strategy for seamless mode transfer is designed and implemented. An improved PQ control method is designed by which the output of the PQ controller always synchronously tracks the output of the V/f controller for micro-grid switches from islanded mode to grid-connected; furthermore, a dq rotating coordinate synchronization based V/f control method is proposed for transition from grid-connected mode to islanded mode. Finally, experiments and analysis are undertaken on some basic and important operating cases; the results in our case study indicate that the modified control strategy is effective in dominating the micro-grid during mode transfer and thus yielding significantly better performances.

Keywords: distributed energy resources; micro-grid; grid-connected operation; islanded operation; mode transfer (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2015
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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