Analysis of Stand-Alone DFIG-DC System and DC Voltage Regulation With Reduced Sensors

Doubly fed induction generator (DFIG)-DC system has distorted stator voltages and currents. Therefore, there is a scope to evolve a scheme, such that it does not require stator side sensing. The proposed scheme is developed utilizing the following fact; since the control variables, i.e., rotor circuit currents, and the controlled variable, i.e., output dc link voltage, are both sensed, the requirement of sensing the intermediate stator side variables can be avoided. Second, the detailed mathematical analysis of the system, including dominant harmonics, is presented in this paper, which is helpful in understanding the behavior of the system. The stator frequency is indirectly maintained around the rated value, by suitable variation of flux reference, against load variations. This system is an attractive solution for variable speed dc power generation. The proposed control scheme is verified by detailed experiments on a 5.5 kW slip-ring induction machine.