Research On Control Strategy And Testbed System Of Direct-drive PMSG WECS

At present, energy crisis is becoming more and more serious, wind energy conversion system (WECS) has aroused the concern of the world due to its green and environment-friendly characteristics. Direct-drive permanent magnet WECS has simple structure and can be controlled conveniently so it is being wildly used. In order to meet customers’requirement for steady power supply, the control strategy of Stand-alone Operation and Grid-connected Operation is evidently the key point.First, the paper presented the control strategy of PWM converter, gird-side voltage oriented vector control algorithm was adopted with voltage and current loops. Meanwhile, synchronous angle was detected for axis transform. Then, a three-phase PWM converter model was built in MATLAB/Simulink, indirect current and direct current control strategy was separately researched, the difference between ac current response was analyzed; Meanwhile, SPWM and SVPWM method were also studied. Finally, the testbed of PWM converter was designed and established, program was also completed.MPPT is actually speed regulation of Permanent Magnet Synchronous Generator (PMSG) in essence, hence, the speed control strategies of PMSG were studied, rotor flux oriented vector control was adopted. Similarly, the speed control model of PMSG was built in MATLAB/Simulink, optimal torque method to achieve Maximum Power Point Track (MPPT) was studied on the basis of id=0vector control strategy. At last, a testbed of30kW PMSG was established and the id=0vector control experiment was also conducted.In back-to-back PWM system, rotor speed of PMSG was controlled by generator-side PWM converter to achieve MPPT. On the other hand, DC bus voltage was controlled by grid-side PWM converter. Then, the model of direct-drive permanent magnet WECS was constructed in MATLAB/Simulink, the results laid the foundation for further research.