Different from utility power systems, the grids of more electric aircraft (MEA) are frequency-variable, and the frequency change range is from 360 Hz to 800 Hz. Most grid synchronization methods are designed for const...
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Different from utility power systems, the grids of more electric aircraft (MEA) are frequency-variable, and the frequency change range is from 360 Hz to 800 Hz. Most grid synchronization methods are designed for constantfrequency grids whose frequency varies in a small range around 50 Hz or 60 Hz. Therefore, the dynamic performance of these methods decreases considerably in MEA grids. In addition, the frequency in MEA is higher than that in utility power systems. Grid voltage parameters are thus required to exhibit a fast dynamic response. To resolve this problem, this paper proposes an algebraic method to estimate the positive- and negative-sequencecomponents (PNSC) of grid voltage accurately. By analyzing the relationship between grid voltage and its time delay signals, the linear regression model is established. Then, grid frequency, PNSC are obtained with an algebraic method. The proposed method relies on algebraic operations only and thus exhibits a fast dynamic response. Experiment results verify the effectiveness of the proposed method.
Static synchronous compensators (STATCOMs) have been widely used for the reactive power and voltage regulation in the renewable energy field. The STATCOM could not only regulate the positive-sequencevoltagecomponent...
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Static synchronous compensators (STATCOMs) have been widely used for the reactive power and voltage regulation in the renewable energy field. The STATCOM could not only regulate the positive-sequencevoltagecomponent, but also suppress the negative-sequencevoltage by injecting the negativesequence current when the grid voltage is unbalanced. Aiming at diminishing the negativesequencevoltage, the control strategy based on the symmetrical virtual resistor circuit is proposed in this study. The strategy is on the assumption that there are parallel virtual resistors connected to the point of interconnection (POI) of the STATCOM. It is theoretically proved that the negativesequencevoltage can be eliminated when the current of the virtual resistors is balanced. Therefore, the negativesequencevoltage can be eliminated by making the current of virtual resistors balanced. As the resistors are virtual in the real circuit, the voltage of the POI of the STATCOM is used in the input of the negative-sequence current control loop instead of the current of the virtual resistors as the feedbacks. The signal of the ac voltages and currents of the STATCOM are only needed in this strategy which simplifies the system design. In the end, the simulation results are presented to validate the correctness and the effectiveness of the proposed control strategy.
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