A novel active voltage and frequency regulator to improve grid-disconnection transients of self-excited induction generator system

Loss of frequency and voltage regulation will be experienced by a self-excited induction generator system (SEIG) when it is disconnected from the utility grid. The SEIG may be shut down due to this grid-disconnection transient. To avoid the foregoing disadvantage, a novel active voltage and frequency regulator (AVFR) for a wind-turbine driven SEIG was developed in this paper. The control strategy of the AVFR is based on the decoupled d- and q-axis control in a synchronously rotating reference frame. The advantages of this scheme are that it can not only compensate the reactive power while SEIG is working in the grid-connection mode but it is also capable of stabilizing the frequency and voltage in the grid-disconnection mode. A mathematical model for this system is first developed, and then the simulation is performed on MATLAB/SIMULINK platform. The simulated results reveal that the performance of AVFR can be used to maintain output frequency and to mitigate terminal voltage fluctuations for the SEIG.