Direct vector control of stand-alone self-excited induction generator

This paper presents the voltage build-up process and the terminal voltage control of a stand-alone self-excited induction generator (SEIG) using direct vector control (DVC) technique under variable speeds and different types of load. Here, the three-phase SEIG is excited by a pulse-width modulated voltage source inverter (PWM-VSI) connected to a single-capacitor on the DC side with a start-up battery. The limitation of having stand-alone SEIG is poor voltage regulation, which occurs with change in speed and load condition. Hence, there should be a control system that keeps the terminal voltage of the SEIG and the DC bus voltage constant when the speed of the rotor and also, the load on the SEIG are varied. The direct vector control scheme has been presented to maintain the terminal voltage of the generator and the DC bus voltage constant for variable rotor speed and load. The space-phasor model of the induction machine has been used in simulation. To predict the performance of the proposed system, a MATLAB/SIMULINK based study has been carried out for both AC and DC loads. The proposed control scheme has shown very good voltage regulation and phase balance even with unbalanced three-phase load.