Firing angle of a TCR

Firing angle of a - Sadhan Vol 30 Part 1 February 2005 pp 5767 Printed in India a Harmonics and voltage stability analysis in power systems

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S¯adhan¯a Vol. 30, Part 1, February 2005, pp. 57–67. © Printed in India Harmonics and voltage stability analysis in power systems including thyristor-controlled reactor M UZUNOGLU Yildiz Technical University, Electrical–Electronics Faculty, Electrical Engineering Department, 34349 Besiktas, Istanbul, Turkey e-mail: [email protected] MS received 28 October 2003; accepted 5 May 2004 Abstract. In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of signi±cant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious har- monic distortions in transmission and distribution systems. In this paper, harmonic generation of a static VAR compensator with thyristor-controlled reactor and effects of the harmonics on steady-state voltage stability are examined for various opera- tional conditions. Keywords. Harmonics; stability; thyristor-controlled reactor. 1. Introduction It is not only required to meet the demand for electrical energy but also to improve its quality. Today, power quality studies are becoming a growing concern. The present paper focuses on two parameters affecting power quality – harmonics and voltage stability. Static VAR compensators (SVCs) are applied on transmission systems to improve voltage control and system stability during both normal and contingency system conditions. Most SVCs use a thyristor-controlled reactor con±guration to provide continuous control of the reactivepowercompensationlevel.Thethyristor-controlledreactor(TCR)producesharmonic currents because thyristors only allow conduction in the reactor for a portion of the cycle. Harmonic current magnitudes vary as the ±ring angle of the thyristors is varied. A comprehen- sive harmonic study includes evaluation of possible harmonic concerns over the full range of ±ring angles and possible system conditions. Generally, harmonic ±ltering is accomplished with capacitors connected in parallel with the TCRs. For transmission applications, the ±lters might include tuned ±lters at the ±fth and seventh harmonics along with a high pass ±lter for higher order components. Use of a static compensator with a thyristor-controlled reactor (TCR) has been known to be an effective and reliable means to ensure power system voltage stability. This device is essentially a variable reactor that can adjust its reactive power consumption. The adjustment is realised through the ±ring angles of thyristors that normally operate in partial conducting 57
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58 M Uzunoglu states, and thereby produce harmonics (Miller 1982). The generated harmonics depend criti- cally on the control characteristics of a static VAR compensator (SVC) with a Fxed-capacitor thyristor-controlled reactor (±C-TCR). However, this makes the Fring angles dependent on the network load ²ow conditions and harmonic voltage distributions (Xu et al 1991). Poor
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This note was uploaded on 03/19/2010 for the course ECE 529 taught by Professor Johnson,b during the Spring '08 term at Idaho.

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Firing angle of a - Sadhan Vol 30 Part 1 February 2005 pp 5767 Printed in India a Harmonics and voltage stability analysis in power systems

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