With an increasing interest for renewable power, photovoltaics (PV) have becomemore and more common in the distribution network. If a customer wants to install aPV system, or another type of distributed generation (DG), the distribution systemoperators (DSO) needs a good way to determine if it the grid can handle it or not. InSweden, a guideline to aid the DSO was published in 2011. However, this guidelineonly considers one connection without considering other DG units. This project isabout developing new guidelines for DG connections in grids with a large number ofDG units. Based on a literature study it has been concluded that one of the mostcritical issue is over-voltage, which is the main focus of this project. Two new methods have been developed; the first proposed method is based onneglecting reactance and losses in the grid, a simple linear relationship between thevoltage level, the resistance in the lines, and the installed power is obtained. Thisrelationship is then used to calculate the voltage level at critical points in the grid. Thesecond method is to find the weakest bus, with a connected DG unit. By assumingthat all power is installed at that point we get a very simple guideline; it is veryconservative but can be used before the first method. A simulation tool has been developed in order to analyze the voltage level in grids forvarious cases with connected DG units. The simulated results have proven that theproposed guidelines are, when considering voltage issues, very reliable and can beuseful. However, further work needs to be done to ensure that other problems donot occur.

The total energy demand in the world is expected to increase in the future years due to thehigh development rate of developing countries. Access to energy enables development, butthe current global energy mix has to be modified if a sustainable growth is desired. Renewableenergy sources (RES) benefit from both a political and economic support from manygovernments and international entities. The growing installation of RES takes place both inlarge scale, as wind farms with sizes 10 – 1000 MW, and in small scale in homes or smallenterprises with sizes 100 W – 100 kW. Small scale wind power connected to the grid is rarenowadays except in the case of remote mini-grids. By contrast, small scale solar photovoltaic(PV) power is being more and more commonly installed, especially in the form of investorownedroof-installed units. Taking increasing small scale solar and wind power into accountin network planning is a challenge faced by the distribution system operator (DSO).The aim of this thesis is to present a guideline that assists DSOs when planning lowvoltage (LV) distribution networks (DN) with a large amount of small scale distributedgeneration (DG) on a short-term perspective. A review on integration issues of DG isperformed and over-voltage constraints are identified as the most relevant issue. Simple ruleshave already been designed for individual DG units, as the one presented in the AMKhandbookpublished by Svensk Energi; but these are not valid any more when consideringmore than one DG unit. The new proposed guideline employs the AMK-handbook as astarting point and develops it further by including the interaction between DG units. Theguideline is then applicable to scenarios with more than one DG unit. The maximum capacityof a new DG unit applying for a connection to a grid is calculated based on the location andcapacity of the already installed DG units, and without any reinforcement. The proposedguideline can be applied under no load and minimum load condition.Since this thesis is a collaboration project between KTH-Royal Institute of Technologyand Vattenfall R&D, two specific Swedish LV distribution networks owned by VattenfallEldistribution AB are studied. Scenarios with different penetration levels of DG, with valuesbetween 12% and 71%, and capacity of individual DG units below 43.5 kW are analyzed.Evaluation of the results shows that the proposed guideline leads to acceptable results. Thedevelopment of future simple guidelines is suggested to be based on the following twoaspects: absolute and relative location of the DG units; and a correct identification of the weakbus. Relative location reveals the interaction with other DG units within the DN. Moreover, itis stated that the use of the penetration level as a planning measure, based on the total DGcapacity, has a limited application.

Although wireless sensor networks have been successfully used for environmental monitoring, one of the major challenges that this technology has been facing is supplying continuous and reliable electrical power during long-term field deployment. Batteries require repetitive visits to the deployment site to replace them once discharged; admittedly, they can be recharged from solar panels, but this only works in open areas where solar radiation is unrestricted. This dissertation introduces a novel approach to design and implement a reliable efficient solar energy harvester to continuously, and autonomously, provide power to wireless sensor nodes for long-term applications. The system uses supercapacitors charged by a solar panel and is designed to reduce power consumption to very low levels. Field tests were conducted for more than a year of continuous operation and under a variety of conditions, including areas under dense foliage. The resulting long-term field data demonstrates the feasibility and sustainability of the harvester system for challenging applications. In addition, we analyzed solar radiation data and supercapacitor charging behavior and showed that the harvester system can operate battery free, running on the power provided by supercapacitors. A battery is included only for backup in case the supercapacitor storage fails. The proposed approach provides continuous power supply to the system thereby significantly minimizing data loss by power failure and the frequency of visits to the deployment sites.

This master’s thesis engages in project of outgoing transformer unit for the photovoltaic power station. It describes project and its design documentation what conducts to practising of construction. It has compared investing to more expansive transformer what has lower loss. It describes charges of operation’s transformer in twenty years. It leads project of cable low voltage. It compares whether is better to use aluminium or cupric cables. Project is led with respect for investment costs and minimum of operation loss.