Submerged Arc Furnace Unbalanced Three-phase Symmetrical Component Analysis Method

Submerged arc furnace is electric furnace which extracts useful elements from the ore. During the ferroalloy smelting production process, Arc resistance's strong misalignment and randomness makes the arc's working condition not to be unstable, the short-net electric current will have many complex changes, generate a large number of harmonic, negative sequence current, cause power factor. The traditional method of symmetrical component method played the very major role in the analysis electrical power system breakdown, But for submerged arc furnace such a strong non-linear equipment, the pure application method of symmetrical component method analyzes the short net electric current three-phase non-equilibrium state to realize with difficulty. This thesis compares and analyses currently some three-phase detection methods used in metallurgy and power system, ip-iq method based on instant reactive power principle of permanency is a simple and reliable algorithm. With the symmetrical component method as a new accurate detection method in aspect of submerged arc furnace short-net harmonic, reactive and negative sequence current. From 2007, the thesis component member depends on the national science and technology support project "Ferroalloy furnace comprehensive energy control technology application research", have carried out the relevant research work, the detecting of arc short net's harmonics, non-reactive and negative sequence current is a important part work, this thesis is selected and carried out in this background.For the main contents of this thesis, carrying on the several research aspects:At first, introducing the composition of submerged arc furnace system briefly, the influence of the three-phase power unbalanced, and some viewpoints of experts in electrode system parameters and model solution method, the purpose is lets the reader have certain preliminary understanding to the submerged arc furnace system.In addition, the thesis carries on the contrastive analysis to the existing unbalanced three-phase current detection algorithms, explains the advantages and disadvantages of various detection algorithms. Taking elaboration and simulation research in Fourier law and ip-iq method which is much suits for the current research of the short-net.through the simulation we Obtains the following conclusions:(1) These above two methods are capable of detection in submerged arc furnace short-net harmonic, reactive and negative sequence current.(2) The ip-iq method requires 3-2 and 2-3 of the coordinate transformation, computation moderate and little delay time. The DFT has Computationally intensive taking up a large number of industrial computer resources, much delay time. (3) The ip-iq method is easily combined with symmetrical component method to analysis the problem of the unbalanced current detection.Furthermore, we design filter-link to resolve the problem amplitude fluctuation of the short-net. The filter-link is based on digital band-pass filter, under the premise of low-amount of the IPC to get the maximum improvement in current detection accuracy.At last, we take application of windings compensation method and similar mutual inductor method to compensate to the CT enhancing the Ferroalloy's CT precision from 0.5-level to 0.2-level, achieving the national standards. The all above parts of this thesis are mutually independent but interrelated, the issue is to accurate the harmonic, reactive and negative sequence current of the short-net. The Matlab simulation results show that the advantage-method combination of symmetrical component method and ip-iq law has high precision and reliability in unbalanced current detection.