The Sensorless Control System Of Permanent Magnet Direct-drive Wind Generators

Direct-drive wind turbine becomes an important research after DFIG in the field of variable speed constant frequency wind power technique, because of its advantages in energy conversion efficiency, reliability, and the flexibility of network power controlling, low voltage ride-through, etc. The installation of speed position sensors not only increased the cost and lowed the reliability of the system, but also made the system be influenced by the temperature, humidity, vibration and other factors easily. Therefore, the sensorless controlling technology becomes a hotspot in the research of permanent magnet direct-drive synchronous wind power generator controlling technology. According to the actual demand of the permanent magnet direct-drive wind power generator in the operation of the wind farm, the paper, based on the theory of the sensorless controlling technology which applied in the operation of wind farm, discussed and analyzed the programming method of the stator flux observer and the control strategy of the permanent magnet direct-drive generator in different conditions, and verified the correctness of the theoretical research through the simulations and experimentsFirst, the paper described the situation and the develop trend of the wind power industry, and then elaboration is drawn about the two operating modes of wind power generator sets, via the technology of variable speed constant frequency. The paper also introduced the structure and functions of full power converter and demonstrated the occasions and developments of the sensorless controlling technology of permanent magnet synchronous motor.Second, the mathematical model and control strategy of PMSG is discussed. The coordinate transformation matrix and various coordinates PMSG mathematical model are derived and the deep study and comparison is drawn in the vector control and direct torque control of PMSG, and confirmed the PMSG control strategy based on zero d-axis current vector control in the power generation condition and the DTC control in the motoring condition.Third, this paper made a survey about the sensorless controlling technology of PMSG. Through the research of the classification of mainstream sensorless controlling technology, pointed out the strength and weakness of stator flux observation based on the U-I mode. The thesis selected the double integrator with a saturable feedback based on coordinate transforming(DISF) for stator flux estimation and studied the process of estimation technique based on the Zero d-axis current vector control and DCT control.Fourth, the simulation model for flux observer and the sensorless control system of the direct-drive PMSG is built. With the simulation research of the flux observer, estimating results of the wave of the flux observer are analyzed and proved. In terms of the simulation model of the sensorless control system of the direct-drive PMSG, the implementation procedure of sensorless controlling technology based on the Zero d axis and the DTC control are analyzed respectively. After a series of simulation, the correctness of theoretical analysis is confirmed.Finally, the operation conditions of direct-driven wind generator sets are simulated in both the generator and the motor conditions, on25kW drag on experimental platform of the permanent magnet synchronous vector. The software is designed based on the hardware system of25kW converter. Via low power experiments of generating and motor-driven, verified the PMSG sensorless controlling strategy based on zero d-axis current vector control in the power generation condition and the DTC control in the motoring condition.