Abstract—In order to further maintain the power balance on both sides of the DC capacitor and make the direct drive permanent magnet wind turbine generators(DPMSG) carry out low voltage ride through safely, the paper proposed a improved low voltage ride through(LVRT) strategy, harmonious flux-weakening control(HFWC), based on the magnetic field characteristics of permanent magnet synchronous motor when the grid voltage dropped. When the grid voltage dropped, in order to reduce the output active power of the generator, it changes the maximum power curve and reduces electromagnetic torque on the one hand, on the other hand, adding a negative current for d-axis in the machine side to achieve weak magnetic control and the value of compensation current increased with the increase of the DC bus voltage. So the current in d axis and q axis worked with each other and make the back EMF of generator decreased ,and the output active power of generator changed with the output active power of the grid. Finally, the simulation model of PMSG was built in Matlab/Simulink, and the control strategy was simulated and verified. Experimental results show that the flux-weakening control method is effective, and the harmonious flux-weakening control strategy(HFWC) made full use of the mechanical and electrical inertia energy storage, and reduced the use frequency of the unloading resistance, thus the wind turbines realized LVRT safely when the grid voltage dropped.

Index Terms—Directly-drive permanent magnet wind turbines, low voltage ride-through, weak magnetic control, simulink.

Huiting Chen is with School of Electrical Engineering, Shanghai Dianji University, Shanghai, China.
Shaojie Xin is with School of Mechanical Engineering, Shanghai Dianji University, Shanghai, China.
Enxing Yang is with Shanghai Electric Power Transmission & Distribution on Group Technology Center, Shanghai, China.

Cite:Huiting Chen, Shaojie Xin, Enxing Yang, "The Improved Low Voltage Ride through Technology of the Directly-Drive Permanent Magnet Wind Turbines," International Journal of Computer and Electrical Engineering vol. 10, no. 1, pp. 12-22, 2018.