Abstract
In this paper a load angle estimation method of round rotor synchronous generator is presented, for load angle limiter in AVR systems design purpose. To get information of load angle, it is necessary to have values of the one terminal voltage, one phase current and q-axis reactance Xq. Mentioned values are acquired by synchronous sampling technique and processed by discrete Fourier transformation. The accuracy of presented method highly depends on quality of zero-crossing detection of the input voltage signal and on the calculation estimation of the fundamental frequency. This method is of reduced sensitivity to higher harmonics presence contence in voltages and current waveforms. Another advantage, when compared to other dq or ab based calculations estimations, is the necessity of use only two measurement channels. Drawback of described approach is lack of immunity to current asymmetry. However, a solution to overcome this problem is offered by introducing the additional measurements into the algorithm to extract the synchronous sampled direct components of all three phase currents.
Highlights
Izračunaćemo digitalnom Furijeovom transformacijom (DFT) samo za jednu tačku k = 1 po definiciji (8), i tako dobiti realne i imaginarne delove Vm1 i Em1 na osnovu kojih možemo izvući informaciju o argumentima Vm1 i Em1
Mentioned values are acquired by synchronous sampling technique and processed by discrete Fourier transformation
The accuracy of presented method highly depends on quality of zero-crossing detection of the input voltage signal and on the calculation estimation of the fundamental frequency
Summary
Ugao snage se sastoji iz unutrašnjeg i spoljašnjeg ugla sinhrone mašine spojene na jaku mrežu:. Estimacija ugla sinhronog turbo generatora može da se izračuna na sledeći način: e. Ako pretpostavimo da je trofazni sistem simetričan i da je napon Vg fazor napona VR a da je struja Ig fazor struje IR, možemo odrediti fazore Em i Vm na osnovu merenja trenutnih vrednosti napona vST i struje iR, videti Sliku 2b). Pomeranje struje iR za 900 električno unapred je ekvivalentno sa pomeranjem napona vR električno unazad, po pogledu faznih stavova. Kako se pomeranje unazad realizuje kao kašnjenje, realizacija na taj način je lako izvodljiva. Fazor napona vR pomeren unazad za 900 je jednak fazoru napona vST / 3. Trenutne vrednosti em i vm se računaju pomoću trenutnih vrednosti vST i iR na sledeći način: em vST / 3 X qiR ,. Fazni stav između vm i em ćemo izračunati pomoću DFT algoritma na osnovnoj frekvenciji f1
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