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SUMMARYNowadays, the amount of distributed generation (DG) connected to distribution networks is increasing significantly. In a European context, one of the main drivers for this growth is the support of electricity generation from renewable energy sources (RES) and combined heat and power (CHP) plants. Hence, these DG units mostly consist of non-controllable generation. Distribution is a regulated activity which is, at least, legally and functionally unbundled from the generation activity. These issues, together with the fact that distribution networks were not originally designed to accommodate generation, pose significant challenges on distribution network planning and operation. One of the major concerns of distribution system operators (DSOs) is the impact that large penetration levels of DG may have on distribution network costs. This paper presents a quantification of the impact of DG on distribution network costs in three real distribution areas. Different scenarios of demand and generation have been analysed for each region. Two possible situations are taken into account in each scenario: maximum net demand and maximum net generation. The computation of the distribution network costs was carried out by means of two large-scale distribution planning models called reference network models (RNMs).

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The objective of this paper is to compare the performance of thyristor-controlled reactors (TCR) and shunt-connected PWM voltage source inverters (PWM-VSI) for compensation of flicker caused by arc furnaces. First of all, arc-furnace principles are presented in order to explain the main characteristics of the problem. Secondly, traditional TCR control are analyzed. An improved measuring procedure is suggested to enhance TCR performance showing that it achieves faster compensation than more traditional methods. Thirdly, PWM-VSI control for flicker compensation is described in detail using Park's transformation. The analysis shows how real and reactive power control can be decoupled. Continuous-time and discrete-time models are considered. Finally, a TCR control and a PWM-VSI control are compared by simulation using data and measurements from a real arc-furnace installation. The analysis considers three different periods of the production cycle: a) bore-down, b) fusion, and c) refining. It is clear from the results obtained that a shunt-connected PWM-VSI is better than a TCR for flicker compensation. This can be easily justified noting that the bandwidth of the PWM-VSI control system is far better than that of the TCR control. However, the control system for a PWM-VSI inverter is more complicated than that of a TCR. Besides, the latter uses a better-established technology than the former.Index Terms-Arc furnace, flicker mitigation, PWM, TCR control, voltage source inverter control. pable@dea.icai.upco.es).Publisher Item Identifier S 0885-8977(00)10314-0.