Abstract The aim of this paper is to analyse the stand-alone operation of the microgrid located in Umoljani, Bosnia and Herzegovina. The analysis was performed for two scenarios; one representing a summer day and the other a winter day. The analysed network was modelled using the DIgSilent PowerFactory. The Photovoltaic (PV) system, Wind Generator (WG) and battery sizing were performed using the HOMER software tool. The load data for the location was obtained from JP Elektroprivreda Bosne i Hercegovine. The analysis showed that the network was able to operate in stand-alone mode. Voltage levels were under the voltage limit defined by EN 50160. Line loading was decreased compared to loading in grid-connected mode. As given by the obtained results for the two scenarios, the consumer demand could be satisfied without the inclusion of WG. However, different input data (wind speed data measured on the location) could change the sizing of the production facilities as the results of the optimization calculations in HOMER, which needs to be considered in microgrid configuration.

A microgrid concept for the thermal and electrical energy supply of a Sport-Recreation Center Ajdinovići (S.R.C.A.) has been proposed in this paper. A self-contained and intelligent power distribution grid has been developed for this case, taking into account the location, locally available renewable energy sources and the very purpose of this center. Comparative analyses between independent power supply through the proposed hybrid power system and the supply over the transmission and distribution network were performed. Technical and economical optimization of an energy system with distributed power generation was done by applying HOMER and DIgSILENT PowerFactory professional software tools. As a result, hybrid power system is more cost-effective than the conventional supply by the power distribution network, microgrid meets the technical criteria based on the analysis of power flows and the stability of the network has been achieved. Establishment of energy independence for the existing S.R.C.A. besides economic factor will show several benefits regarding better use of locally available resources, reduction of CO2 emissions and energy efficiency increment as well as an employment opportunity to the local people, thus contributing to the sustainability of the region.

Modelling of harmonics in large medium voltage (MV) distribution networks has so far been a challenge due to the presence of a large number of harmonic sources contributing to total harmonic voltages. This study proposes a deterministic methodology of modelling harmonics in large real MV distribution networks using aggregate harmonic source models parameterised based on measurements and results from the literature. In this research, background harmonic voltages from the sub-transmission system are parameterised based on measurements in the analysed network. Aggregate harmonic current emission of different customer categories in low-voltage (LV) networks (households and small commercial customers) parameterised based on several measurements in LV networks was dominated by residential or office customer type configurations. The harmonic current emission of industrial customers is parameterised based on the results from published literature. Two methods for modelling harmonic sources are used and compared: (i) modelling according to the IEC 61000-3-6 summation law and recommended summation exponents and (ii) modelling using complex phasors. The results of the models show a good match with the measurements from power quality monitors installed in the analysed MV network. Based on these results, the method according to the IEC 61000-3-6 is recommended for large MV distribution networks.

Many recent studies have dealt with the future of the power distribution system, and there are different technologies which will facilitate the development towards the smart power distribution grid vision. Plug-in electric vehicles (PEV) and distributed generation (DG) technologies will become integral part of this vision. PEVs are specific because they can act both as a load and as a source of energy in a concept known as Vehicle-toGrid (V2G). This paper analyses the impact of these technologies on an example of a real medium-voltage distribution network operating in Bosnia and Herzegovina. The impact of each technology and in combination with another technology is analyzed. It is shown that the impact of PEVs may be negative in terms of the increase in the peak load and power losses as well as transformer overloading for scenarios of a high-penetration level and uncontrolled charging. However, controlled charging and regulated implementation of V2G can be beneficial in certain terms. The Photovoltaic (PV) technology can reduce the power losses, but will violate voltage-limitations in periods of high solar insolation, especially for a high-penetration level. By controlling the new emerging technologies, many of the negative impacts can be reduced and even turned into positive effects.

Harmonic voltages are important voltage quality parameters defined in EN 50160. For harmonic voltage studies in electricity networks, harmonic emission of loads is often modelled as harmonic current source. In this paper harmonic current sources were parameterised on the basis of measure-ments of total harmonic current emission of several different low voltage networks. Measurements from low voltage net-works with different typical customer configurations were used: residential, offices and PV. A real medium voltage electricity distribution network of an Austrian distribution system operator, with significant consumption of residential and office customers, was chosen for this analysis. In order to automate the harmonic load flow calculations in DIgSILENT PowerFactory for every 10-minute interval of one week, a script in DIgSILENT Programming Language - DPL was developed. Harmonic voltage results from the harmonic load flow simulation are compared with the results of harmonic voltage measurements from power quality monitoring system installed in this network. The goal of this paper is to assess the suitability of the approach, where only background harmonics and key harmonic current sources are modelled. Since the approach provided good results, it can be used in future work as a basis for optimising the number and locations of power quality monitors in electricity distribution networks.

Power quality is one of the important challenges for the smart distribution grids. It is not possible to know the state of power quality in the network without appropriate measurements or monitoring. As an answer to need for power quality monitoring in smart distribution grids, this paper further develops the Integrated Power Quality Monitoring System (IPQMS). IPQMS integrates power quality data from all the measurement devices available in the smart distribution grids: power quality monitors, portable power quality analyzers, smart meters, protection relays, fault locators etc. Smart meters are the key sensors in smart distribution grids and should be used as indicators of power quality disturbances in IPQMS. The complementary use of power quality monitors and smart meters in IPQMS should enable the analysis of the propagation of power quality disturbances throughout the distribution network. Current state-of-the-art smart meters have certain capabilities regarding the monitoring of some power quality parameters. The necessary upgrades to the state-of-the-art smart meters regarding their power quality monitoring capabilities are discussed in this paper in the context of their role in IPQMS. This paper elaborates in detail one new concept of operation and process algorithms for IPQMS, with special emphasis on smart meters. This paper also presents experimental results of integrated power quality monitoring using power quality monitors, state-of-the-art smart meters and protection relays. The presented experimental results prove that with integrated power quality monitoring, distribution system operators can get a complete information about power quality in their networks.

Expected increase in plug-in electric vehicle (PEV) sales makes different analysis of their impacts on electricity distribution networks very interesting. This paper analyses the impacts of PEV charging on an example of a real low voltage (LV) distribution network for various PEV penetration scenarios (5 %, 10 %, 20 % and 50 %). Two main charging technologies were modelled: slow charging at private charging stations and fast charging at public charging stations. Two basic charging modes were analysed: unregulated and regulated. The analysis was done in a professional software tool for analysis of LV distribution networks: WINDis. The results have shown that PEV charging can have negative impacts in terms of increased peak load, increase of power losses, overload of transformers and lines, decrease of voltage values and increased voltage asymmetry. It has been shown that the LV network can support regulated slow charging of a large number of PEV's.

Anticipated mass production and integration of plug-in electric vehicles (PEV) in the power system asks for the analysis of the impacts of PEV charging on different aspects of power system operation. This paper presents the analysis of the impacts of PEV charging on the example of a part of a real medium voltage distribution network from the Bosnia and Herzegovina. Three different charging technologies were modelled: slow charging at private charging stations, fast charging at public charging stations and ultrafast charging at DC charging stations. Three charging modes were analysed for slow charging: unregulated, regulated and regulated with Vehicle-to-grid (V2G) intervals. The analysis showed that the charging of PEV's has negative impacts on the distribution network in terms of the increase of peak load, the increase of energy losses, the negative impact on voltage profiles and the overload of distribution transformers. By regulating the process of PEV charging most of the negative impacts can however be reduced.