Abstract
This paper proposes a design methodology for an active power filter (APF) system to suppress the second harmonic subgroup injected by an AC electric arc furnace (EAF) to the utility grid. The APF system is composed of identical parallel units connected to the utility grid via a specially-designed coupling transformer. Each APF converter is a three-phase three-wire two-level voltage source converter (VSC). The number of parallel APF units, coupling transformer MVA rating, and turns ratio are optimized in the view of the ratings of commercially-available high voltage (HV) IGBTs. In this research work, line current waveforms sampled at 25.6-kS/s on the medium voltage (MV) side of a 65-MVA EAF transformer are then used to extract the second harmonic subgroup, 95-, 100-, and 105-Hz current components, by multiple synchronous reference frame (MSRF) analysis, which was previously proposed to decompose EAF current interharmonics and harmonics in real-time. By summing up this digital data of the second harmonic subgroup, the reference current signal for the APF system is produced in real-time. A detailed model of the APF system is then run on EMTDC/PSCAD to follow the produced reference current signal according to hysteresis band control philosophy. The simulation results show that the proposed APF system can successfully suppress the second harmonic subgroup of an AC EAF.
Highlights
Alternating current electric arc furnaces (AC EAF), which are widely used in steel melting and shaping industry, are nonlinear loads with rapidly changing operating characteristics
A; (ii) for thethe peak values of the current harmonic in time; (ii) values of the subgroup current harmonic components rarely coincide in time; (iii) the the peak optimum solution to the preliminary design study is chosen to be the minimization of the (iii) the optimum solution to thecurrents preliminary design study is chosen be the minimization of the second harmonic subgroup instead of the elimination of to them entirely; and harmonic subgroup currents instead of the elimination of themtransformer entirely; andcompensates (iv) second the fundamental current component flowing through the coupling onlyfundamental for active power filter (APF) switching conduction losses through and to magnetize the transformer
In order to make a comparison between the second harmonic subgroup current components of EAF and APF, the associated waveforms are expanded into DFT for a 10-cycle window
Summary
Alternating current electric arc furnaces (AC EAF), which are widely used in steel melting and shaping industry, are nonlinear loads with rapidly changing operating characteristics. For this reason, AC EAFs cause serious power quality problems on the utility grid such as voltage flicker, large and highly-fluctuating reactive power, harmonics, and interharmonics [1,2,3,4,5,6,7,8]. Harmonic and interharmonic current coupling transformer MVA rating and turns ratio are optimized in the view of the high voltage references obtained in real-time usinginMSRF analysis parallel processingcurrent on a (HV) IGBT are power semiconductors available the market. Framework, whichEAF provides fast and accurate current reference estimations for the highly time-varying EAF currents
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