Zoran Baus

PROBABILITY DENSITY FUNCTIONS OF VOLTAGE SAGS MEASURED INDICES

Probability Density Functions of Voltage Sags Measured Indices Voltage sags can cause interruptions of industrial processes, which could result as a malfunction of equipment and considerable economic losses. Thus, it is very useful to see certain rules of voltage sags occurrence due to duration and depth. This paper presents statistical analyses of voltage sags in several domestic and industrial transformer stations. Voltage sag probability functions are calculated from actual measurement data, by means of a hill climbing algorithm. Lognormal and Weibull frequency distribution functions are used to describe distribution of measured voltage dips.

Short–Term Planning of Hybrid Power System

Abstract In this paper short-term planning algorithm for hybrid power system consist of different types of cascade hydropower plants (run-of-the river, pumped storage, conventional), thermal power plants (coal-fired power plants, combined cycle gas-fired power plants) and wind farms is presented. The optimization process provides a joint bid of the hybrid system, and thus making the operation schedule of hydro and thermal power plants, the operation condition of pumped-storage hydropower plants with the aim of maximizing profits on day ahead market, according to expected hourly electricity prices, the expected local water inflow in certain hydropower plants, and the expected production of electrical energy from the wind farm, taking into account previously contracted bilateral agreement for electricity generation. Optimization process is formulated as hourly-discretized mixed integer linear optimization problem. Optimization model is applied on the case study in order to show general features of the developed model.

Smart Grid Architecture Based on Active Demand Approach

The paper analyzes ways on how to establish and sustain an active participation of consumers in the modern Smart Grid Architecture based on the Active Demand Approach by proposing the conceptual framework that supports it. The planning and implementation of the power system is a very demanding task, requiring that the electrical energy production and consumption are always equal. In order to efficiently manage such system, and its safety, an appropriate level of flexibility must be present. Today, the generators acting on the production side are the main flexibility enablers, and there is a very low level of flexibility available on the consumer side. From the technical point of view, it is necessary to establish a smart infrastructure that will be networked by the data transmission chain, in order to provide timely, accurate and highly secure transfer of required data. In this paper, we present the demand response approach and the respective solution on how to achieve the sufficient level of the consumer flexibility in such proposed model implementation. With addressing different technical aspects and IoT (Internet of Things) the envisaged integration is elaborated by taking into account the important requirements of its IT infrastructure, by analyzing the robustness, reliability and safety issues of the proposed system.

Use of Fuzzy Logic Systems for Assessment of Primary Faults

Abstract In electric power systems, grid elements are often subjected to very complex and demanding disturbances or dangerous operating conditions. Determining initial fault or cause of those states is a difficult task. When fault occurs, often it is an imperative to disconnect affected grid element from the grid. This paper contains an overview of possibilities for using fuzzy logic in an assessment of primary faults in the transmission grid. The tool for this task is SCADA system, which is based on information of currents, voltages, events of protection devices and status of circuit breakers in the grid. The function model described with the membership function and fuzzy logic systems will be presented in the paper. For input data, diagnostics system uses information of protection devices tripping, states of circuit breakers and measurements of currents and voltages before and after faults.

Power quality indices of distribution feeder in eastern Croatia under electricity market conditions

The reform of the Croatian energy sector began in 2000 in terms of harmonization with the European energy sector. Adoption of the energy acts has created necessary conditions for gradual opening of the national electricity market.