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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced electrical systems: From megabyte to megawatt' taking place on Wednesday, 12 March 2014 at 09:00-10:30. The meet-the-authors will take place in the poster area.

Jinho Kim Chonbu National University, Korea, Republic of
Co-authors:
Jinho Kim (1) F P
(1) Chonbu National Univercity, Chonju, Korea, Democratic People's Republic of

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Jinho Kim received his B.S. degree from Chonbuk National University, Korea in 2013. He is currently pursuing his M. S. degree at Chonbuk National University. His research interests include the development of control and protection methods for wind power plants in terms of voltage and reactive power.

Abstract

Dynamic behavior of a DFIG-based wind power plant for a grid fault considering the wake effects

Introduction

To meet the low voltage ride-through (LVRT) requirement, a wind power plant (WPP) should not only remain connected to the grid during a grid fault, but supply the active and reactive power after the fault clearance. The comprehensive study on the behavior of the WPP for a grid fault is required to design the control strategies of the WPP. To do this, it is essential to consider the wake effects for the analysis of the accurate WPP’s behavior because the wind speeds arrived at each WG are totally different and thus the WGs are operating in the different conditions.

Approach

The previous researches used a single equivalent WG for the study on the response of the WPP in the case of a grid fault. However, an aggregated WPP model is unable to represent the accurate behavior of the WPP because the WGs are not operating in the same conditions. In addition, difficulties arise in modeling the wake effects in the aggregated WPP. Thus, this paper models a WPP, which is composed of the multiple WGs. To consider the wake effects, the N. O. Jensen model is used to calculate the different wind speeds arrived at each WG.

Main body of abstract

In this paper, a 100 MW DFIG-based offshore WPP, which is composed of 20 units of a 5 MW DFIG, is modeled using an EMTP-RV simulator. To consider the wake effects, the wind speeds of the individual WGs are calculated with the different wind directions by using the N. O. Jensen model. To consider a grid fault, two kinds of the symmetrical faults with the different voltage dips are simulated. In this paper, the rotor-side converter (RSC) is in charge of regulating the active and reactive power through the stator to the grid whilst the grid-side converter (GSC) is in charge of keeping dc-link voltage constant in normal operation. However, the GSC injects the reactive power to the grid if the RSC is disconnected due to the activation of the crowbar. The results indicate that the crowbars in the WGs are activated at the different instants depending on the operating conditions due to the wake effects. For a zero voltage fault, the responses of the WPP are nearly the same during the fault even in the different wind directions whilst the WPP’s responses depend on the wind directions after the fault clearance. However, for a 0.7 pu voltage fault, the responses of the WPP depends on the wind directions during the fault as well as after the fault clearance. This is because the WGs are in the different operating conditions and thus the reactive powers consumed by the collection feeders depend on the active powers from the WGs.

Conclusion

This paper analyzes the dynamic behavior of a DFIG-based offshore WPP considering the wake effects. The active and reactive power and the voltage at the PCC are analyzed after the fault clearance as well as during the grid fault for the different wind directions. The simulation results indicate that the active and reactive power of the WPP are quite different depending on the wind directions due to the wake effects, particularly in the case of a 0.7pu voltage fault. The results will be utilized as a basis for the proper control algorithms to meet the LVRT requirement of the WPP.


Learning objectives
To analyze the accurate behavior of a DFIG-based offshore WPP for a grid fault, the wake effects should be considered because the different wind speeds arrived at the individual WGs give impacts on the WPP’s behavior during the fault as well as after the fault clearance.