Gcsc gto thyristor controlled series capacitor
- 1. GCSC - GTO THYRISTOR CONTROLLED SERIES CAPACITOR PRESENTED BY LEO PAUL CHITTILAPPILLY
- 2. INTRODUCTION • Proposed by Karady & others in 1992. • It consists of Fixed capacitor in parallel with anti parallel GTO pair or valve. • Thyristor valve has the capability to turn on and turn off mechanism. • Act as a dual of TCR.
- 3. BASIC SCHEME OF GCSC
- 4. • The GCSC controls the voltage across the capacitor (Vc) for a given line current. • when the GTO is closed the voltage across the capacitor is zero • when the GTO is open the voltage across the capacitor is at its maximum value • The magnitude of the capacitor voltage can be varied continuously by the method of delayed angle control • For practical applications, the GCSC compensates either the voltage or reactance
- 5. WORKING • Closing and opening of valve is carried out in each half cycle in synchronism with supply frequency. • Turn off instant of each half cycle is controlled by a delay angle ᵞ wrt peak of line current. • Here ᵞ varies from 0 to 90 degrees. • Line current i and Vc are shown for ᵞ =0 and at an arbitary value of ᵞ
- 6. principle of turn-off delay angle control
- 7. • Variation of VCF is normalized to maximum voltage • GCSC can be operated in either to control Voltage or reactance • Fundamental component of the series capacitor voltage vs. the turn-off delay angle γ.
- 8. GCSC IN VOLTAGE COMPENSATING MODE • GCSC can be operated either to compensate voltage or to compensate Xc(ᵞ). • In first case, GCSC is used to maintain the rated compensating voltage in association with decrease of line current over an interval I min ≤ I ≤I max • n this case, Xc is selected in such a manner that Vc max/I min = Xc. • When I is increased from I min to I max, ᵞ is also increased
- 9. GCSC IN REACTANCE COMPENSATING MODE • GCSC is used to maintain the max rated compensating reactance at any line current up to max. • In this case, Xc is selected in such a manner that Vc max/I max = Xc. • GCSC can be used to vary Xc from 0≤ Xc(ᵞ) ≤ Xc