Characteristic Analysis Of Blade Mass Imbalance Fault Of Wind Turbines Considering Spatiotemporal Distribution Of Wind Speed

With the expansion of the installed capacity of wind turbines,the size of wind turbines has also increased rapidly.On the one hand,the spatiotemporal distribution characteristics of wind have a greater impact on the wind power generation system;on the other hand,the impact of fault on the wind turbine has also become more complicated.Various factors have led to increased difficulty in wind turbine operation,maintenance and management.Therefore,it becomes significant to study the influence of wind turbine fault and wind speed spatiotemporal distribution on the aerodynamic characteristics of the wind turbine and the electrical characteristics of the generator is of great significance to wind turbine operation and maintenance management.Therefore,this paper takes doubly-fed wind turbine(DFIG)as the research object,and conducts a systematic study on the blade mass imbalance fault based on the spatiotemporal distribution of wind speed.First,the common types and mechanisms of blade faults are analyzed;the effects of faults on the electrical characteristics of DFIG and how to establish a fault diagnosis mechanism are emphasized;then,the equivalent wind speed model including wind shear and tower shadow effect is established and the effect of equivalent wind speed on the electrical characteristics of DFIG was analyzed;finally,a simulation platform was built to verify the conclusion of the theoretical analysis.The specific work and research content are as follows:(1)Established a mathematical model of DFIG,and built a simulation platform suitable for simulation and analysis according to the mathematical model.This simulation platform fully considers the blade aerodynamics,drive chain,DFIG transient characteristics and DFIG rotor side and Network-side control strategy.(2)The mechanism of the blade mass unbalance fault is analyzed,and the fault characteristics of the electrical signals such as electromagnetic power,stator and rotor current of the DFIG during the blade mass imbalance fault are analyzed and derived.(3)An equivalent wind speed model including wind shear and tower shadow effect is established.Combined with the DFIG model and the equivalent wind speed model,the mathematical model of output power and power coefficient is derived.Based on this model,the influence of wind turbine parameters such as blade radius,tower height,tower diameter and blade-to-tower centerline on power fluctuation frequency,amplitude,wavelength,fluctuation area and other characteristics were studied.Finally,an average power loss model is established,and the influence of wind turbine parameters on power loss due to the existence of equivalent wind speed is analyzed.The results show that the existence of equivalent wind speed will cause periodic fluctuation of output power and power loss.There are certain rules for the influence of different parameters on power fluctuation and power loss,and the blade radius and tower height are the main parameters that cause power loss.(4)Comprehensively considering the spatiotemporal distribution of natural wind speed,the influence of blade mass imbalance fault on the electrical characteristics of DFIG under the consideration of equivalent wind speed is re-analyzed.Firstly,the fault characteristics are analyzed and deduced.Based on the dq coordinate transformation method,the analytical expressions of the electromagnetic power,the stator and rotor currents and their variation characteristics under the blade mass imbalance fault after considering the wind speed spatiotemporal distribution are obtained.Electromagnetic power will have one-fold and 3i-fold rotor rotation frequency fluctuations,where the one-fold rotor rotation frequency fluctuation is caused by blade mass imbalance fault,and the 3i-fold rotor rotation frequency fluctuations are caused by equivalent wind speeds.The stator and rotor currents contain modulation frequencies mainly based on one-fold and 3i-fold rotor rotation frequency,and there are modulation frequencies which are 3i times frequency conversion but other than three-fold rotor rotation frequency,their amplitude is smaller.The fluctuation at f_e±f_w is caused by imbalance fault,the amplitude increases with the degree of imbalance;f_e±3if_w are caused by the equivalent wind speed,and its amplitude does not change with the degree of imbalance.(5)Establishing wind speed model and fault model based on DFIG simulation platform,and the electrical signals are obtained through simulation analysis,analyze the signals using a variety of signal processing methods,and propose a DFIG blade mass imbalance fault diagnosis method based on the electromagnetic power,stator current and rotor current,and consider wind speed spatiotemporal distribution.Based on the electrical signal characteristics of DFIG,this paper monitors the blade mass imbalance fault,and considers the spatiotemporal distribution of wind speed in the analysis,which provides a basis for fault diagnosis in actual operation of wind turbines,so as to achieve the purpose of improving wind power equipment operation and maintenance management technology.