An In-Depth Analysis of an advanced Series Compensation Technique

Abstract

A set of analytical equations describing tlie stcady state beliavior of an advanced form of scrics compcnsation is developed. The sclienac consists of a series capacitor conncctcd in parallcl with a thyristor-controlled rcaclor. Tlic cquations reveal tlie changes in the overall series cornpcnsalion by varying the thyristor firing angle. Additionally, the equations allow a means of calculating tlie cxpected compensation level for a given system. The eKccts of changes in the circuit parameters using the equations is also iwcsligaled, along with tlic harnionics gcncratcd by the cllyristor-controlled reactor. The steady state and transient characteristics of the advanced scrics cornpensation tecliriiquc wcre further studicd on a circuit model. The cquations developed rcveal that tlicre is a gradual approach in excess of 10 cycles toward a steady state condition for higher levels of series compensation. The circuit niodcl rcvealed a harmonic instability that occurs whcn the thyristors arc fired in a "quasi-resonant" region, which rcsults in unpredictable circuit beliavior.