Research On The Low Voltage Ride-Through Of Direct-Drive Wind Turbine System

With the demand of world for clean energy, promote the rapid development of wind power industry. However, large-scale wind power generation system access to grid had a significant impact on grid stability. So for the network of wind power generation system proposed a new challenge—fault ride through capability. A number of advantages that now increasingly sophisticated high-power converter technology and high-performance permanent magnet materials technology and the simple structure, reliable technology, high power quality, low maintenance costs of the direct-drive permanent magnet wind power generation system have been verified in the world. Compared with the double-fed wind power generation system’s1/3of the inverter capacity, using the direct-drive permanent magnet wind power generation system with full power converter technology is more easily achieved low-voltage ride-through, either does not absorb reactive power. So it will better to meet the demanding requirements of grid.This paper focuses on the technical of low-voltage ride-through of direct-drive wind power system to start a series of works base on "Micro-Grid and its Controller Platform" of Southwest Jiaotong University211Project. Firstly, this paper study the motor steady-state analysis method based on phase diagram and the motor dynamic analysis based on coordinate transformation method,then establishment of permanent magnet motor and the voltage-type PWM rectifier mathematical model and the unity power factor vector control strategies in the conditions of symmetrical three-phase grid voltage and verified by Matlab/simulation.Secondly, deduced the form of negative-sequence component in a positive synchronous reference frame (SRF),and derived the PWM rectifier mathematical model in unbalanced input voltage condition. After that,this paper analyzed the PWM rectifier system response during the voltage drop and compared it with the non-fault conditions, obtained the conclusion that during the voltage drop.Then the direct-drive wind power system’s low-voltage ride-through program is proposed which based on Crowbar circuit unloading and Statcom operation strategy. And uses Matlab/Simulink verify the validity and reliability of the program. Finally,designed a5kW proto,which included dual DSP+FPGA digital controller, permanent magnet synchronous generator(PMSM) and PWM rectifier, and carryed out lots of key experiments and tests to verify the algorithm of direct-drive wind turbine system.