Firing Angle Range Control For Minimising Harmonics in TCR Employed in SVC-s

Most electrical distribution systems are incurring large losses as the loads are wide spread, inadequate reactive power compensation facilities and their improper control. A typical static VAR compensator consists of capacitor bank in binary sequential steps operated in conjunction with a thyristor controlled reactor of the smallest step size. This SVC facilitates stepless control of reactive power closely matching with load requirements so as to maintain power factor nearer to unity. This type of SVC-s requiring a appropriately controlled TCR. This paper deals with an air cored reactor suitable for distribution transformer of 3phase, 50Hz, Dy11, 11KV/433V, 125 KVA capacity. Air cored reactors are designed, built, tested and operated in conjunction with capacitor bank in five binary sequential steps. It is established how the delta connected TCR minimizes the harmonic components and the operating range for various electrical quantities as a function of firing angle is investigated. In particular firing angle v/s line & phase currents, D.C. components, THD-s, active and reactive powers, odd and even triplen harmonics, dominant characteristic harmonics are all investigated and range of firing angle is fixed for satisfactory operation. The harmonic spectra for phase and line quantities at specified firing angles are given. In case the TCR is operated within the bound specified in this paper established through simulation studies are yielding the best possible operating condition particularly free from all dominant harmonics.

Authors:

• D. R. Patil
• U. Gudaru

Keywords:

• Binary Sequential switched capacitor bank
• TCR
• Nontriplen harmonics
• step less Q control
• Active and Reactivepower
• Simulink

References:

[1] Herold Pender and Knov Mclwain, "Electrical Engineers Hand Book".
[2] U. Gudaru, Satish Sangale and D. R. Patil, "Adaptive static VAR
compensation for Rural Distribution Systems" presented at the
workshop on ÔÇÿReactive Power Compensation in Power Systems-,
organized by Engineering Staff College of India, Hyderabad, June 1992.
[3] A. Hammad and B. Roesle, "New roles for static Var compensators in
transmission system", Brown Boveri Rev., Vol. 73, pp 314-320, Jun.
1986.
[4] J. Kearly et. al., "Microprocessor controlled reactive power compensator
for loss reduction in Rural Distribution Feeders", IEEE Transactions on
power delivery, Vol. 6, No. 4. October 1991, pp. 1848-1855.
[5] Narain G. Hingorani and L. Gyugyi, "Understanding FACTS" IEEE
Press.
[6] K. Stahllleopf, M. Wichelm, "Tighter Controls for Busier System",
IEEE Spectrum, April 1977, P 49-52.
[7] J. Grahm, "Transient stability enhancement using Static Var
Compensation", Wart Verginia University, Thesis, 378, 3543 Engg.
G76tc2, Oct. 1995.
[8] U. Gudaru, "Microprocessor based static compensator of TSC and TCR
type meeting A. C. System control requirements", published in
CAPACIT-86 by IEEMA M. Young, The Techincal Writers Handbook.
Mill Valley, CA: University Science, 1989.