Comparison of thyristor-controlled reactors and voltage-sourceinverters for compensation of flicker caused by arc furnaces

摘要

The objective of this paper is to compare the performance ofnthyristor-controlled reactors (TCR) and shunt-connected PWM voltagensource inverters (PWM-VSI) for compensation of flicker caused by arcnfurnaces. First of all, arc-furnace principles are presented in order tonexplain the main characteristics of the problem. Secondly, traditionalnTCR control are analyzed. An improved measuring procedure is suggestednto enhance TCR performance showing that it achieves faster compensationnthan more traditional methods. Thirdly, PWM-VSI control for flickerncompensation is described in detail using Park's transformation. Thenanalysis shows how real and reactive power control can be decoupled.nContinuous-time and discrete-time models are considered. Finally, a TCRncontrol and a PWM-VSI control are compared by simulation using data andnmeasurements from a real arc-furnace installation. The analysisnconsiders three different periods of the production cycle: (a)nbore-down, (b) fusion, and (c) refining. It is clear from the resultsnobtained that a shunt-connected PWM-VSI is better than a TCR for flickerncompensation. This can be easily justified noting that the bandwidth ofnthe PWM-VSI control system is far better than that of the TCR control.nHowever, the control system for a PWM-VSI inverter is more complicatednthan that of a TCR. Besides, the latter uses a better-establishedntechnology than the former