Higher Frequency Modeling of Synchronous Exciter Machines by Equivalent Circuits and Transfer Functions

In this article the influence of higher frequency effects in addition to a special damper design on the electrical behavior of a synchronous generator main exciter machine is investigated. On the one hand these machines are often highly stressed by harmonics from the bridge rectifier thus facing additional eddy current losses. On the other hand the switching may cause the excitation of dangerous voltage peaks in resonant circuits formed by the diodes of the rectifier and the commutation reactance of the machine. Therefore modern rotating exciters are treated like synchronous generators usually modeled with a second order equivalent circuit. Hence the well known Standstill Frequency Response Test (SSFR) method is applied to a test machine in order to determine parameters for the simulation. With these results it is clearly shown that higher frequencies have a strong impact on the conventional equivalent circuit model. Because of increasing field displacement effects in the stranded armature winding the sub-transient reactance is even smaller than the armature leakage at high frequencies. As a matter of fact this prevents the algorithm to find an equivalent scheme. This issue is finally solved using Laplace transfer functions fully describing the transient behavior at the model ports.

Authors:

• Marcus Banda

Keywords:

• Synchronous exciter machine
• Linear transfer function
• SSFR
• Equivalent Circuit

References:

[1] D. R. Gomes, I.E. Chabu, "Studies on electrical stresses in rotating
rectifiers for brushless exciters", IEEE/IAS Internal Conference of
Industrial Applications, November 2010
[2] S.M.L. Kabir, R. Shuttleworth, "Brushless exciter models", IEE Proc.-
Gener. Trans. Distrib., Vol. 141, No.1, January 1994
[3] M. Shahnazari, A. Vahedi, "Analysis of brushless exciter operation in all
modes of rotating rectifiers", 4th IEEE Conference on Industrial
Electronics and Applications, ICIEA 2009, June 2009
[4] M.A. Abdel-Halim, C.D. Manning, "Modeling a laminated brushless
exciter-alternator unit in all modes of operation", IEE Proceedings-B,
Vol.138, No.2, March 1991
[5] IEEE Std 115-1995, "Obtaining Synchronous Machine Parameters by
Standstill Frequency Response Test"
[6] DIN EN 60034-4, 2009, "Verfahren zur Ermittlung von Kenngrößen von
Synchronmaschinen durch Messung"
[7] P.L. Dandeno, A.T. Poray, "Development of detailled Turbogenerator
equivalent circuits from standstill frequency response measurements",
IEEE Transactions on Power Apparatus and Systems, Vol. PAS-100,
No. 4, April 1981, Ontario Hydro
[8] I.M. Canay, "Determination of the model parameters of machines from
the reactance operators xd(p), xq(p) (Evaluation of the Standstill
Frequency Response Test)", IEEE Transactions on Energy Conversion,
Vol.8, No.2, June 1993
[9] M. Freese, M. Klocke, "Aspects of Identification of equivalent circuit
parameters of large synchronous generators by SSFR - Tests",
Proceedings of XLIIIrd International Symposium on Electrical Machines
SME 2007, 2 -5 July, Poznań, Poland
[10] M. Banda, O. Michelsson, "A new network calculation model for the
predetermination of the exciter current and the reactance of salient-pole
synchronous machine", Information Technology and Electrical
Engineering - Devices and Systems, Materials and Technologies for the
Future, IWK, Internationales Wissenschaftliches Kolloquium der TU
Ilmenau, 54 / 2009 / 20100305890
[11] I.M. Canay, "Modeling of alternating-current machines having multiple
rotor circuits", IEEE Transactions on Energy Conversion, Vol. 8, No.2 ,
June 1993
[12] I.M., Canay, "Causes of Discrepancies on calculation of rotor quantities
and exact equivalent diagrams of the synchronous machine", IEEE
Transactions on Power Apparatus and Systems, Vol. PAS-88, pp.1114-
1120, July 1969
[13] Ponick, B., M├╝ller, G., "Theorie elektrischer Maschinen", 6. Auflage,
2009, Wiley-VCH
[14] I. M. Canay, "Block Diagrams and Transfer Functions of the
Synchronous Machine", IEEE TRANSACTIONS ON POWER
APPARATUS AND SYSTEMS, VOL. PAS-85, No. 9, 1966
[15] K.H. Dempewolf, "Transiente Simulation eines Antriebssystems zur
Bestimmung der frequenzabhängigen Verluste in schnelllaufenden
permanenterregten Synchronmaschinen", Internationaler ETG Kongress
Karlsruhe 2007