Improving low-voltage ride-through capability of a multimegawatt DFIG based wind turbine under grid faults

Mohamed Nadour,Tamou Nasser,Ahmed Essadki

doi:10.1186/s41601-020-00172-w

Abstract

Large integration of doubly-fed induction generator (DFIG) based wind turbines (WTs) into power networks can have significant consequences for power system operation and the quality of the energy supplied due to their excessive sensitivity towards grid disturbances. Under voltage dips, the resulting overcurrent and overvoltage in the rotor circuit and the DC link of a DFIG, could lead to the activation of the protection system and WT disconnection. This potentially results in sudden loss of several tens/hundreds of MWs of energy, and consequently intensifying the severity of the fault. This paper aims to combine the use of a crowbar protection circuit and a robust backstepping control strategy that takes into consideration of the dynamics of the magnetic flux, to improve DFIG’s Low-Voltage Ride Through capability and fulfill the latest grid code requirements. While the power electronic interfaces are protected, the WTs also provide large reactive power during the fault to assist system voltage recovery. Simulation results using Matlab/Simulink demonstrate the effectiveness of the proposed strategy in terms of dynamic response and robustness against parametric variations.

Highlights

In the last few decades, there have been significant development and utilization of wind energy conversion systems (WECs)
Based on the theoretical analysis of the doubly-fed induction generator (DFIG)’s dynamic behavior during a severe voltage dip, this work proposes a combination of active crowbar hardware solution and robust control strategy that takes into consideration the dynamics of the generator magnetic flux, to fulfill the latest grid code requirements
3.1 Control objectives The section proposes a robust control strategy based on the backstepping approach, to allow DFIG based wind turbines (WTs) to respond to the latest grid connection requirements under grid voltage disturbances

Summary

Introduction

In the last few decades, there have been significant development and utilization of wind energy conversion systems (WECs). These control schemes suffer from stability problems due to the considerable time delay introduced during the decomposition process and the sluggish transient response of PI current controllers [14, 17, 18] These control strategies can only be effective when the voltage dip is short and not severe enough (very high overcurrent induced in the rotor windings) to urge for crowbar assistance. Based on the theoretical analysis of the DFIG’s dynamic behavior during a severe voltage dip, this work proposes a combination of active crowbar hardware solution and robust control strategy that takes into consideration the dynamics of the generator magnetic flux, to fulfill the latest grid code requirements. This means that an oversizing of the converters must be considered, losing one of the DFIG main advantages [6]

The proposed control strategy

Ls ψsq

Conclusion

Findings

Nomenclatures