The connection of distributed sources and their impact on distribution grid has been the subject of intensive research in the last two decades. Creating a favorable environment for the production of electrical energy from renewable energy sources in many countries around the world made an evident increase in electrical energy production from renewable sources. Connecting these generators to distribution grid is not always an easy task, and often, in cases of inadequate analysis and poor choice of ways of connecting these sources, can have a negative impact on the quality of electrical energy in local distribution grids. In this paper, using a realistic test system, the focus of research is to identify the behavior of group synchronous generators connected to the medium-voltage distribution grid in "cascade" manner. The s elected test system presents the real power distribution system of the Municipality of Gornji Vakuf-Uskoplje, to which six synchronous generators are connected at the moment. Analyses results of the work of this power distribution system in the previous period indicate that there have been significant changes in the existing distribution grid (significant change in voltage, increased losses, etc.) after these generators were connected. Dynamic simulations are conducted on the basis of the appropriate mathematical models, and the response of the generators and changes in the voltage value in the distribution grid were simulated for several types of disturbances. The results show that generators remain in synchronism while tested on selected simulated disturbances, where the oscillations of the generator rotor disappear over a period of several seconds. Also, the changes of voltage value in distribution grids for simulated disturbances are within the permitted limits.

Abstract Power system is constantly exposed to disturbances of varying intensity and cascading propagation of disturbance that can lead to partial or total power system blackout. Some of the consequences are network topology changes, outage of generator units or occurrence of low-frequency electromechanical oscillations (LFEO). One of the techniques for signal analysis and processing used in the past 20 years for power system disturbance analysis, and helped in better understanding of power system dynamic, is Wavelet Transform (WT). This work reviews WT applications for power system dynamic behavior analysis. With research made on vast literature it can be concluded that WT technique has different applications in disturbances identification and localization, LFEO identification and analysis, and assessment of active power imbalance.

—In terms of power sector restructuring and electricity market opening there have been significant changes in the functioning of activities at the level of Public Enterprise Elektroprivreda BiH d.d - Sarajevo (EPBiH). Distribution activity in an open electricity market is not a market activity, but the regulated activity, and although does not participate directly in the electricity market, its action must allow unhindered development and functioning of the market in which suppliers competes. The introduction of the smart grid concept in electricity distribution activity is a particularly challenging area of research due to the actuality and importance. The paper presents the elements of the business framework of EPBiH in terms of application of modern technologies in the area of smart grid and the changes that inevitably occur during transition process of energy sector in general

Future smart distribution grids will apart from a large number of measurement instruments, communication infrastructure, intelligent software etc., also require the appropriate techniques for analysis of the available signals. Various disturbances of different intensities constantly occur in real distribution systems. Many of them are just temporary while others cause the tripping of protection devices and the suspension of electricity supply. For distribution network operators, timely identification and adequate analysis of disturbances represent a very important segment of operation of electricity distribution networks. In this paper, the disturbance registered in the real distribution system of Bosnia and Herzegovina is analysed using four different time-frequency analysis techniques (Short-Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT), Wigner-Ville Distribution (WVD) and Hilbert-Huang Transform (HHT)). The results show that all the applied techniques successfully identified the disturbance which is reflected in changes in frequency during the observed time period. These techniques could be suitable to be applied as a part of power quality monitoring systems, which provide the required measurement signals. The utilization of these techniques can provide distribution system operators with additional, a very important information about the distribution system.

Analysis of power consumption presents a very important issue for power distribution system operators. Some power system processes such as planning, demand forecasting, development, etc.., require a complete understanding of behaviour of power consumption for observed area , which requires appropriate techniques for analysis of available data. In this paper, two different time-frequency techniques are applied for analysis of hourly values of active an d reactive power consumption from one real power distribution transformer substation in urban part of Sarajevo city . Using the continuous wavelet transform (CWT) with wavelet power spectrum and global wavelet spectrum some properties of analysed time series are determined. Then, empirical mode decomposition (EMD) and Hilbert -Huang Transform (HHT) are applied for the analyses of the same time series and the results show ed that both applied approaches can provide very useful information about the behaviour of power consumption for observed time interval and different period (frequency) bands. Also it can be noticed that the results obtained by global wavelet spectrum and marginal Hilbert spectrum are very similar, thus confirming that both approaches could be used for identification of main properties of active and reactive power consumption time series .