Abstract
This paper focuses on the electro-thermal analysis of a doubly-fed induction generator (DFIG) in a wind turbine (WT) with gear transmission configuration. The study of the thermal mechanism plays an important role in the development of cost-effective fault diagnostic techniques, design for reliability and premature failure prevention. Starting from an analysis of the DFIG system control and its power losses mechanism, a model that synthesizes the thermal mechanism of the DFIG and a WT system principle is developed to study the thermodynamics of generator stator winding. The transient-state and steady-state temperature characteristics of stator winding under constant and step-cycle patterns of wind speed are studied to show an intrinsic thermal process within a variable-speed WT generator. Thermal behaviors of two failure modes, i.e., generator ventilation system failure and generator stator winding under electric voltage unbalance, are examined in details and validated by both simulation and data analysis. The effective approach presented in this paper for generator fault diagnosis using the acquired SCADA data shows the importance of simulation models in providing guidance for post-data analysis and interpretation. WT generator winding lifetime is finally estimated based on a thermal ageing model to investigate the impacts of wind speed and failure mode.
Highlights
While wind energy development shifting from onshore to offshore, the external environment in which wind turbines (WTs) are installed has become more and more harsh [1]
Assuming a rigid drive train model, Jr is the rotational inertia of the WT rotor, Jg is the rotational inertia of the generator rotors, Tr is the aerodynamic torque of the WT (N·m); Tg is the mechanical torque of the high-speed shaft (N·m) which is connected to the generator, ωr is the rotor speed, ωg is the generator speed, n is the transmission ratio of gear box, η is the efficiency of the gearbox
The simulation performed in this paper is based on an onshore WT equipped with a doubly-fed induction generator (DFIG)
Summary
While wind energy development shifting from onshore to offshore, the external environment in which wind turbines (WTs) are installed has become more and more harsh [1]. The main advantages of the LPN method, such as low computational cost and capability to include the heat transfer of the cooling system, make it an appropriate method for thermal analysis of radial flux electrical generators [8]. Increasing high winding temperatures, e.g., caused by a ventilation system failure, can lead to permanent changes of the properties of the insulation system and even asphaltic run [10] In these cases the lifetime can be reduced significantly and diagnostic tests should be performed to estimate the remaining life. Applications of thermal analysis of WT DFIG on fault detection and diagnosis, and generator insulation lifetime estimation are presented By combining both simulation and realistic data analysis, the thermal mechanisms of two failure modes, i.e., generator ventilation system failure and supply voltage unbalance, are analyzed in detail to interpret the acquired data
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