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.

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 .