Research on Zero-Voltage Ride Through Control Strategy of Doubly Fed Wind Turbine

Kaina Qin,Zhongjian Kang,Shanshan Wang

doi:10.3390/en14082287

Abstract

With the rapid increase in the proportion of the installed wind power capacity in the total grid capacity, the state has put forward higher and higher requirements for wind power integration into the grid, among which the most difficult requirement is the zero-voltage ride through (ZVRT) capability of the wind turbine. When the voltage drops deeply, a series of transient processes, such as serious overvoltage, overcurrent, or speed rise, will occur in the motor, which will seriously endanger the safe operation of the wind turbine itself and its control system, and cause large-scale off-grid accident of wind generator. Therefore, it is of great significance to improve the uninterrupted operation ability of the wind turbine. Doubly fed induction generator (DFIG) can achieve the best wind energy tracking control in a wide range of wind speed and has the advantage of flexible power regulation. It is widely used at present, but it is sensitive to the grid voltage. In the current study, the DFIG is taken as the research object. The transient process of the DFIG during a fault is analyzed in detail. The mechanism of the rotor overcurrent and DC bus overvoltage of the DFIG during fault is studied. Additionally, the simulation model is built in DIgSILENT. The active crowbar hardware protection circuit is put into the rotor side of the wind turbine, and the extended state observer and terminal sliding mode control are added to the grid side converter control. Through the cooperative control technology, the rotor overcurrent and DC bus overvoltage can be suppressed to realize the zero-voltage ride-through of the doubly fed wind turbine, and ensure the safe and stable operation of the wind farm. Finally, the simulation results are presented to verify the theoretical analysis and the proposed control strategy.

Highlights

Driven by the rapid development of the global economy, the wind energy market is developing rapidly, and the installed capacity of global wind power is expanding promptly
The zero voltage ride through is based on the concept of low voltage ride through (LVRT), which refers to the ability of the wind turbine to maintain continuous operation without disconnection when the grid voltage drops to 0 completely [5]
Due to the special topology structure that the stator side of the doubly fed induction generator (DFIG), which is directly connected to the power grid, it is sensitive to grid voltage fault, its ability to resist grid disturbance is relatively weak, and due to the limitation of converter power, the fault ride through the capability of the DFIG is reduced [7]

Summary

Introduction

Driven by the rapid development of the global economy, the wind energy market is developing rapidly, and the installed capacity of global wind power is expanding promptly. The stator and rotor leakage inductance of large-scale doubly fed wind turbine are relatively small, about 0.1 times the standard unit value. In this way, the fault current generated by the DC component of the flux linkage will be large, even up to 5 to 10 times the rated value, which will bring serious damage to the doubly fed wind turbine system. RRoototrocrurcruenrtrceunrvte couf trhve edooufbltyhfeeddinoduucbtiolyn gfeenderaitnord(uDFcItGio) unndgeer nthererea-pthoarse(DFIG) short-circuit fault 1 du Substituting Equation (16) into Equation (15), Equation (217) can be obtained: dc

C P P 1C du2dc 2 dt 2 dt

Switching Strategy of Active Crowbar Circuit

Simulation Analysis

Conclusions