Harmonic Domain Periodic Steady-State Modelingof Power Electronics Apparatus: SVC and TCSC

Lima, L.; Semlyen, A.; Iravani, R.M.

Author Affiliation: University of Toronto; Universidade FederalFluminense.

Abstract: This paper presents a general model for the representa-tion of a thyristor-controlled reactor (TCR) in frequency domain. Themodel undelines the implementation of a Newton-Raphson procedureto determine the periodic steady state of the power system with fastconvergence and high accuracy. The TCR model is used as a buildingblock to represent more sophisticated power electronics apparatus,such as the static var compensator (SVC) and the thyristor-controlledseries capacitor (TCSC).

Keywords: Power electronics, switched systems, thyristor circuits,power system harmonics, harmonic analysis, nonlinear systems.

Preprint Order Number: PE-269PRD (09-2002)Discussion Deadline: February 2003

A Systematical Method for SuppressingFerroresonance at Neutral-Grounded Substations

Li, Y; Qin, R.; Yang, J.; Shi, W

Author Affiliation: Jinyuan Power Plant; Xian Jiaotong University.Abstract: At neutral-grounded substations, ferroresonance may

happen upon switching a circuit breaker or disconnector due to the sat-urated magnetizing characteristics of the bus PT. A systematicalmethod is presented to analyze and suppress the phenomenon. Thescheme for suppressing the ferroresonance is to insert resistance, madefrom parallel-connected resistors, into the PT's wye secondary circuit.For a particular substation, it is first studied theoretically whetherferroresonance can possibly happen; and, if so, a theoretical critical re-sistance is estimated to avoid the resonance. A practical one is thenachieved by EMTP simulation on the basis of the theoretical one. Thescheme for switching these resistors out of the circuit is to not do it all atonce but rather in turn to avoid exciting ferroresonance again. The ap-propriate resistance value of the resistors and the schedule of switchingthem out are also determined by EMTP simulation. A prototype wasdeveloped to fulfill the scheme and proved to be effective by field tests.In addition, it is demonstrated that this kind of ferroresonance cannotbe suppressed by adding resistance to the PT's delta secondary circuit.

Keywords: Circuit breaker, electromagnetic transient, EMTP,ferroresonance, potential transformer, substation.

Preprint Order Number: PE-388PRD (09-2002)Discussion Deadline: February 2003

A New High-Pulse Voltage-SourcedConverter for HVDC Transmission

Liu, Y; Arrillaga, J.; Watson, N.R.

Author Affiliation: University of Canterbury.Abstract: The proposed converter is based on the reinjection of a

series of dc voltage pulses, at a frequency multiple of the fundamental,that shape the output voltage waveforms into a multilevel scheme. Thereinjection ratio and frequency are chosen to convert the standard12-pulse into 36-pulse configuration without the assistance of filters orPWM. Thus the switching losses are greatly reduced. The harmoniccurrent injection can be kept within present standards by an appropriatechoice of the interface transformer leakage reactance.

Keywords: dc voltage pulse reinjection, harmonic elimination, volt-age source converters, multi-level waveforms, HVDC transmission.

Preprint Order Number: PE-019PRD (09-2002)Discussion Deadline: February 2003

Frequency Response Characteristicsof the Unifled Power Flow Controller

Papic, I.; Gole, A.M.

Author Affiliation: University ofLjubljana; University ofManitoba.Abstract: The frequency response characteristics of the unified

power flow controller (UPFC) are derived using a state variable formu-lation. These characteristics are shown to be functions of the UPFC pa-rameters as well as of the operating point. The method is used toidentify operating points that cause resonance problems. The analyticalformulation is validated using an electromagnetic transients simulationtool. In addition, the influence of the UPFC's control system on the fre-quency response characteristic is investigated using a frequency scan-ning procedure coupled with a time domain simulation.

Keywords: FACTS, UPFC, frequency dependent model, frequencyresponse, frequency scanning.

Preprint Order Number: PE-020PRD (09-2002)Discussion Deadline: February 2003

SVC Dynamic Analytical ModelJovcic, D.

Author Affiliation: University of Ulster.Abstract: This paper presents a linear state-space model of a static

var compensator (SVC). The model consists of three individual subsys-tem models: an ac system, an SVC model, and a controller model,linked together through d-q transformation. The issue of nonlinearsusceptance-voltage term and coupling with a static frame of referenceis resolved using an artificial rotating susceptance and linearizing itsdependence on firing angle. The model is implemented in MATLABand verified against PSCAD/EMTDC in the time and frequency do-mains. The verification demonstrates very good system gain accuracyin a wide frequency rangef