عنوان مقاله
هارمونیک و تحلیل چشمک زن در شبکه های نیرو کوره قوسی
فهرست مطالب
مقدمه
مدل سازی کوره قوسی
شبیه سازیدیجیتالی شبکه
هارمونیک
چشمک زن
نتیجه گیری
بخشی از مقاله
چشمک زن
پدیده چشمک زن به حس تجربه شده از دید انسان اشاره می کند زمانی که در شدت منابع نوری تغییرات سریعی رخ می دهد.روشنایی دائماً در حال تغییر باعث اذیت شده و همین امر منجر به شکایت بعضی از مشتریان اصلی می گردد. بر طبق کارهای تحقیقاتی وسیع انجام شده ، کاملاً معلوم است که چشمک زن را در شریط نوسانات مکرر ولتاژ تا فرکانسی دید آشکارسازی ترکیب تصاویر به وسیله چشم غیر ممکن می باشد.
کلمات کلیدی:
Harmonics and Flicker Analysis in Arc Furnace Power Systems J. Sousa(*) M.T. Correia de Barros M. Covas A. Simões IST - Technical University of Lisbon Instituto da Energia - INTERG Av. Rovisco Pais, 1096 Lisboa Codex (*) previously at LABELEC / EDP group PORTUGAL Abstract - This paper presents guidelines for the accurate evaluation of harmonics and flicker generated by ac electric arc furnaces, and its propagation through transmission and distribution systems. It is presented a typical case where a HV system supplies a high capacity arc furnace. The electrical network is simulated using the ATP version of the EMTP where a non-linear time-varying three-phase arc model is implemented in MODELS. The time-domain simulations are then used to evaluate the harmonic distortion and the short-term flicker severity index (Pst). For such purpose, two programs were developed using the MATLAB programming language. Keywords: Arc Furnace Modelling, MODELS, ATP Digital Simulation, Harmonics, Flicker. I. INTRODUCTION Disturbances produced in electrical networks by electric arc furnaces can significantly affect the voltage quality supplied by electrical power companies. In fact, an electric arc furnace is a non-linear, time-varying load, which gives rise to harmonics, interharmonics and voltage fluctuations (flicker). The cause of harmonics is mainly related to the non-linear voltage-current characteristic of the arc while the voltage fluctuations are due to the arc length changes that occur during the melting of the scrap. The current and voltage harmonic distortion causes several problems in electrical power systems, such as incorrect operation of devices, premature ageing of equipment, additional losses in transmission and distribution networks, overvoltages and overcurrents. The flicker phenomenon does not very much affect the electric equipments, but a physiological uneasiness in vision occurs due to electric lightning flux fluctuations, which are particularly important with incandescent lamps. Therefore, it is of crucial importance to predict these effects when an arc furnace is to be connected to a network or when an existing furnace is to be upgraded. Whenever the emission limits are exceeded ([1],[2]), mitigation techniques are to be used in order to correct such disturbances. This paper presents guidelines for accurate prediction of the harmonics and flicker generated by arc furnaces operation. The study covers the modelling of an ac three-phase arc furnace ([3],[4],[5],[6]) using the MODELS programming language of the ATP version of the EMTP ([7],[8]), the time-domain simulation of the transmission system and the evaluation of the harmonic distortion and the flicker severity index using two external routines developed in MATLAB according to international standards ([9],[10]). II. ARC FURNACE MODELLING The arc furnace modelling comprises two different features. On one hand, the accurate representation of the highly non-linear behaviour of the arc within each power cycle, which is the main cause of harmonics and interharmonics. On the other hand, the simulation of the arc length variations due to changes occurred in the melting process, are directly related to the flicker phenomenon. The model is implemented via a time-varying resistance controlled by the MODELS routine of the ATP, having the arc current as input variable. The evaluation of the value of this resistance for each time-step is described below and follows essentially the model presented in [5], adapted to the present study.
