Self-excited induction generator (SEIG) has received a lot of attentions for its increasing application in distributed generation systems with the essential feature of low cost. To analysis, the dynamic and transient performance of SEIG, several modifications of the mathematical models have been developed for improving the regulation of voltage and frequency. But these models are still complicated to be used in practice. Based on the transient equivalent circuit, a reduced-order model of SEIG with complex transformation in the two-phase stationary reference frame is realized for the transient analysis of voltage build-up. In this simplified model, the coefficients of the characteristic polynomial with multi-timescale time constants are proposed. Moreover, the physical interpretation of system transient behavior with the reconstructed time constants is established and visualized. Particularly, the upper and lower limits of the capacitance and speed for the SEIG with different parameters variation are simulated and analyzed respectively. The validation and the accuracy of the SEIG model are verified for the transient analysis of the voltage build-up. It is proved that the reduced-order model can be effectively used to insight the dynamic stability of SEIG voltage build-up with the multi-timescale. INDEX TERMS Autonomous system, characteristic polynomial equations, complex coefficients, multi-timescale, self-excited induction generator, voltage build-up analysis.
Finite control set-model predictive torque control (FCS-MPTC) depends on the system parameters and the weight coefficients setting. At the same time, since the actual load disturbance is unavoidable, the model parameters are not matched, and there is a torque tracking error. In traditional FCS-MPTC, the outer loop—that is, the speed loop—adopts a classic Proportional Integral (PI) controller, abbreviated as PI-MPTC. The pole placement of the PI controller is usually designed by a plunge-and-test, and it is difficult to achieve optimal dynamic performance and optimal suppression of concentrated disturbances at the same time. Aiming at squirrel cage induction motors, this paper first proposes an outer-loop F-ETFC-MPTC control strategy based on a feed-forward factor for electromagnetic torque feedback compensation (F-ETFC). The electromagnetic torque was imported to the input of the current regulator, which is used as the control input signal of feedback compensation of the speed loop; therefore, the capacity of an anti-load-torque-disturbance of the speed loop was improved. The given speed is quantified by a feed-forward factor into the input of the current regulator, which is used as the feed-forward adjustment control input of the speed controller to improve the dynamic response of the speed loop. The range of the feed-forward factor and feed-back compensation coefficient can be obtained according to the structural analysis of the system, which simplifies the process of parameter design adjustment. At the same time, the multi-objective optimization based on the sorting method replaces the single cost function in traditional control, so that the selection of the voltage vector works without the weight coefficient and can solve complicated calculation problems in traditional control. Finally, according to the relationship between the voltage vector and the switch state, the virtual six groups of three vector voltages can be adjusted in both the direction and amplitude, thereby effectively improving the control performance and reducing the flow rate and torque ripple. The experiment is based on the dSPACE platform, and experimental results verify the feasibility of the proposed F-ETFC-MPTC. Compared with traditional PI-MPTC, the feed-forward factor can effectively improve the stability time of the system by more than 10 percent, electromagnetic torque feedback compensation can improve the anti-load torque disturbance ability of the system by more than 60 percent, and the three-vector voltage method can effectively reduce the disturbance.
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