Fault Diagnosis And Fault-tolerant Control Of The Converters In The Direct-driven Permanent Magnet Synchronous Wind Power System

As a most mature technology owned, the most development prospect renewableenergy utilization technology, the wind power generation technology has received ahuge worldwide attention, while the existing control strategies of wind turbines areonly limited to the normally operation, but the reality situation is the variableenvironment and the high failure-rate. With the fast growing of the wind turbinesinstalled capacity, how to improve the reliability of wind turbines has become a focalpoint of research.Recently, among the various types of wind power system, the permanent magnetdirect drive wind power system becomes the most promising development direction,because of the unique advantages especially no gearbox which has a highestfailure-rate. But due to it adopts back-to-back power converter, all of energygenerated by wind turbines be send to the grid through the converter. As the maincomponent and weak part of energy conversion system, the converter has a highestfailure-rate. In order to ensure the wind power system running continuously underconverter faults, it is urgent need to study the fault diagnosis and fault-tolerant controltechnology.In this paper, Firstly, the topology of permanent magnet direct drive wind powergeneration system are introduced, then the mathematical models of the PermanentMagnet Synchronous Motor and PWM converter are introduced detailedly. Based onthat, it introduced a kind of commonly used wind power system control strategy, itmakes a base for the future analysis.Secondly, according to the circuit topology of converter after failure, the runningmechanism of converter after open-circuit fault are analyzed in theory, and combiningthe Simulink simulation and experimental results, concluded that the changes ofcharacteristics of the system under converter faults. In order to overcomes theshortcomings of the traditional fault diagnostic method, such as calculate complexand the vulnerable to interferences, find out the unique change rules of characteristicsof the system after faults, by contraposes the operating characteristics of the systemunder normal operation, fault operation and interference occured. On the basis of that,this method choosing PMSG-side and grid-side current for fault diagnostic, it detectsfaults based on the variations of current Park’s vector phase, locates fault’s position according to the range of PMSG-side average current Park’s vector phase and thepositive or negative of grid-side each phase current. Basides, the simulink model andexperimental platform are built up, with simulation and experiment results validatethe reliability and rapidity of this fault diagnosis method.Finally, the principle of the three-phase four-switch converter and the algorithmof four-switch SVPWM are described deeply, considering the effect of DC buscapacitor voltage unbalance, the SVPWM formulas under voltage imbalance arediscussed detailedly. Fault-tolerant topology and control strategy of the no-redundanttolerant control system are designed, once fault occurred, converter will work in themode of three-phase four-switch by reconstituting topology of system. In theenvironment of Matlab/Simulink, fault-tolerant control model is built up andembedded in the fault diagnostic system, constitutes a complete wind powerfault-tolerant control system, to meet the targets of sustainable operation under faultoccurred of converter.