Research on the unit power factor control of directly-driven PM wind generator

Compared with the doubly-fed AC excited wind-power generation system, the directly-driven permanent magnet synchronous generator (PMSG) for wind-power system has advantage of simpler structure, higher generation efficiency and more reliable operation. To solve the weakness associated with the traditional i_d=0 control scheme, such as relatively large power rating for generator-side converter and correspondingly increased power losses, a kind of unit power factor control strategy is put forward in this paper. The proposed new scheme is based on the control of back-to-back PWM converter used to connect PMSG with the grid, in which the unit power factor control is applied to the PMSG side converter by calculating the stator current, the grid voltage oriented control is appiled to the grid side converter to regulate output power factor of wind-power system. System simulation result demonstrates that using the proposed new scheme, the PMSG is capable of always keeping unit power factor operation at the steady-state and dynamic process both in the independent control of grid-connected active power and reactive power.