Research On Fault Tolerant Control Of Current Sensor In Doubly-fed Wind Power Generation System

In order to face the shortage of fossil energy caused by population growth and social development,China has been committed to developing new energy since the 21 st century.With the development of offshore wind power generation strategy and the breakthrough of variable-speed constant-frequency(VSCF)wind power generation technology,the wind energy industry has maintained steady and rapid growth,gradually carrying the banner of the new energy industry.Among them,doubly-fed wind turbines,with many advantages,firmly occupy the leading position in the field of wind power,and their installed capacity and coverage are the largest in the world.Under such a huge industrial layout,how to ensure the operational reliability of doubly-fed wind turbines has always been a concern of people.In this paper,doubly-fed induction generator(DFIG)and brushless doubly-fed generator(BDFG)are taken as the research objects.The current sensor faults in double-fed wind power generation system are studied,and a novel current observer algorithm is proposed.With the proposed current observer as the core,a fault-tolerant control strategy for the current sensor is proposed.(1)The mathematical model of DFIG in three-phase stationary ABC coordinate system is established,and several common coordinate transformation formulas are explained in detail.On this basis,the current state space equation of DFIG in arbitrary synchronous rotating dq coordinate system is derived.Then,the basic principle of DFIG vector control is described intuitively and clearly in combination with simulation experiments.(2)Based on the DFIG model,the mathematical models of winding rotor BDFG in different coordinate systems are derived rigorously and in detail.The current state space equations of BDFG in rotor speed dq coordinate system and double synchronous speed MT coordinate system are derived.In addition,a brushless doubly-fed generator model and its vector control system based on Simulink are established.(3)Based on the model reference adaptive system,the reference model of the current observer can be obtained from the current state space equation of the generator.The coefficient matrix of state variables in the reference model is decomposed into a constant matrix and a time-varying matrix with speed variables.The complex pole assignment problem of time-varying systems can be avoided by using the constant matrix as the coefficient matrix of state variables of the adaptive model and the product of the time-varying matrix and the reference model as the time-varying input of the adaptive model.Based on Lyapunov stability theory,an adaptive law for estimating current is constructed.There are current differential terms that can not be neglected in the non-ideal steady state in the obtained current differential equation.This paper proposes and proves that the adaptive model can be used to replace the state variables approximately to optimize the adaptive law.(4)According to the residual between the measured value of the sensor and the estimated value of the observer,the fault of the current sensor can be diagnosed.By substituting the current observer for the corresponding sensor,the sensorless operation of the vector control system can be realized.Finally,taking the wind power generation system of DFIG as an example,the simulation experiment of fault-tolerant control of stator current sensor is carried out,and the results prove the reliability of the proposed theory.