Sensor-Fault-Estimation-based Tolerant Control For Single-phase Two-level PWM Rectifier In Electric Traction System

It is well known that power traction systems are the “heart” of high-speed trains.As one of the most crucial devices in the traction system,the rectifier determines whether the subsequent components can work in a normal condition.Therefore,the safety and reliability of traction rectifier is directly linked to the service consistency of power traction system.However,due to the complex and harsh operation environment of high-speed train,the sensors of rectifier may be subjected to many potential failures,which lead to the serious degradation of control performance of vehicular rectifier,and even the catastrophic failure of the whole traction drive system.Thus,in order to improve the operation safety of traction rectifier,this thesis develops the sensor fault-tolerant control method of traction rectifier based on the fault estimation and fault compensation theory,which is composed of the following aspects:Rectifier modeling and controller design:Firstly,the structure of single-phase power traction rectifier is introduced,and its standard state space model is constructed based on the switching principles of the switching devices in the main circuit.Secondly,for the single-phase two-level traction rectifier,the corresponding (9(9 decoupling control algorithm is designed to guarantee that the system is of excellent control performance under fault-free conditions,which lays the foundation for the algorithm embedding of sensor fault-tolerant control algorithm.Performance evaluation of sensor fault-tolerant control algorithm based on the Luenberger observer:After a brief introduction of the basic principle of Luenberger observer,a Luenberger observer is designed for the above rectifier topology,and the eigenvalue assignment method is used to guarantee the convergence of the observation error.Based on the observer,investigation of the difference between the observer output and the sensor output of the system,commonly called as residual,is carried out,and the corresponding threshold is designed for different residuals which relate to different sensors,improving the performance of the fault diagnosis unit.Moreover,the control reconfiguration is developed in which the observed output is used to replace the measurement output,reaching the goal of fault-tolerant control.Sensor fault-tolerant control for catenary current sensor and DC-link voltage sensor based on fault estimation:Due to the poor performance of the classical sensor fault-tolerant control based on Luenberger observer,the fault-tolerant control of catenary current sensor and DC-link voltage sensor based on fault estimation is discussed.Firstly,a descriptor linear switched rectifier model is established for the purpose of fault-tolerant control,and a linear reduced order observer is designed for the descriptor model to guarantee that the observation error converges exponentially,so as to achieve the goal of accurate sensor fault estimation.Furthermore,by adopting fault compensation technique,the goal of sensor fault-tolerant control is achieved.Fault-tolerant control of grid side voltage sensor based on fault estimation:Since the catenary voltage sensor is modeled as the control input in the rectifier model,thus the catenary voltage sensor fault-tolerant design is transformed to the design of actuator fault-tolerant control design in the descriptor system,which makes the fault estimation of the catenary voltage sensor possible.By designing an unknown input observer for the descriptor system with the catenary voltage sensor fault as one of the state variables,the accurate fault estimation of the catenary voltage sensor is achieved,and the fault estimation result is robust to the unknown disturbances.