The concept of interference alignment has recently become one of the importanttools to analyze the capacity of many multiuser communication networks,e.g. K-user interference channel, wireless X networks, multi hop interferencenetworks, etc. The idea is to consolidate the interference into smallerdimensions of signal space at each receiver and use the remaining dimensionsto transmit the desired signals. Furthermore, most progress in understandingof the wireless networks capacity has been made on the single hop schemes andmulti-hop multi-cast networks. However, there has not been as much progressin multi-hop multi-flow networks where all messages are not required by alldestination nodes. One of the basic problems in this area, is the capacity of2 × 2 × 2 interference channel. It is proved that the upper bound value of 2degrees of freedom (DoF) for this channel can be achieved using the so called“aligned interference neutralization” method.In the proposed interference alignment schemes for network problems whichwe mentioned in the above, including 2 × 2 × 2 interference channel, there aresome theoretical assumptions which seem to be difficult to apply in practice,e.g. high transmit power, asymptotic symbol extension of the channel, globaland perfect channel state information (CSI), etc. Among these assumptionsthe availability of CSI specially at transmitter, is crucial for performing theinterference alignment technique. The CSI at transmitter (CSIT) is usuallyavailable through feedback from receiver and it is used to estimate the currentchannel state, given that the channel coherence-time is long enough. However,it has been shown recently that the delayed CSIT, which is assumed to be independentof current channel state, still can be used to increase DoF of somespecific network settings.In this work, we consider the 2 × 2 × 2 interference channel where twosource nodes communicate with corresponding destination nodes via two relaynodes. We investigated the degrees of freedom of 2×2×2 interference channelwith delayed CSIT and we derived the upper bound on the degrees of freedomof the channel under this condition. Furthermore, we showed that this upperbound can be achieved using interference alignment technique. We also showedthat this completely out-of-date information of the channel can still be usefulto achieve higher rate compared to the situation where no CSIT is availableat the source nodes. Moreover, we observed that using relay nodes in interferencechannel can improve DoF compared to one hop interference channelwhere transmitters and receivers directly communicate with each other.

In this thesis, we investigate the performance of the coordinated MIMO precoders, using measured channels in indoorvenvironment. Instead of simulated radio propagationvconditions, measured channels are used to evaluate the precoder performance for real-world channels. Our measurement campaign includes several scenarios such as femtocell and “heterogeneous” networks. The study results illustrate that the precoders could reduce the interference significantly and support a high system throughput especially over high SNR where interference is dominant. Degree of freedom (DoF) is defined as the maximum number of data stream that could independently coordinate to be transmitted interference-free. Theoretically, the precoders could support 1 DoF per user, while DoF of uncoordinated transmission is 0 per user. Interference Alignment(IA) study arises from information theory of DoF in the interference channel (IC). Three precoding algorithms are investigated to align the interference: maximum sum rate, maxSINR and minWLI. Considering the distributed precoder methods, “maxSINR” always performs better than “minWLI”. Since it tries to maximize the user’s SINR instead of only repressing the interference as “minWLI” does. While “maximum sum rate” is not good at finding an IA like solution that scales well at high SNR. However “maximum sum rate” converges faster than “maxSINR” and “minWLI”. Our study about IA feasibility shows that precoding jointly over two subcarriers, using so called frequency extensions, allows 4 users to communicate interference-freeover a 2 × 2 MIMO IC. Without frequency extensions, only 3 users can communicate interference-free.

As the electric consumption increases and the investments are hard to make, electricitynetworks are operated closer to their limits. In such conditions, a generator or a transmissionline outage can have tremendous impact, leaving a great number of people without electricity. Itis therefore a matter of prime importance to ensure power system security and in particularvoltage stability. Static criteria used in on-line simulations as well as protection and defensedevices such as load-shedding devices play a critical role for voltage stability and are thus crucialfor the network security. The core of this project is to determine efficient tools to detectundesirable conditions in operational context and to determine a pertinent activation level foran automatic load-shedding device used for the system protection against voltage instability.In the first part of this report, theoretical background regarding voltage stability ispresented, followed by the software and methodologies used during the Master’s thesis work.The second part of this report focuses on case studies conducted for the French powersystem. From an initial objective of updating static criteria, the results have actually led to thewithdrawal of these criteria and a switch to dynamic simulations for the North-East and Eastareas, as well as to the improvement of Astre software database. Simulations on the moststressed conditions from last winter allowed the updating of the activation level for theautomatic load-shedding device. These changes have been validated and will be applied forvoltage security assessment of the French network in the future.

This master thesis project represents an improved model of a grid connected three phase, singlestage PV system implemented in SIMPOW program. The proposal model consists of a PVgenerator employing a PWM converter in order to interface the AC network. The main objectiveof the project is to introduce the main components of the represented model as well as therequired controller schemes. In order to achieve the accurate performance of the PV system withrespect to the integration grid, both AC and DC side network are equipped with controllerfacilities, optimizing the system operation. The control facilities, implemented on the DC side,are mainly focusing on regulation of the output DC voltage of the generator depending on therequirements of the system. The newly proposal MPPT model represents an improvedoptimization strategy for the DC voltage extraction corresponding to various environmentalconditions. The AC side controllers are designed considering the PV system dynamiccontribution on the grid as well as its participation in reactive power provision to the network. Tostudy the accuracy of the dynamic operation of the system, several case studies have beenperformed on AC and DC side. The results of those studies have been discussed considering theirsimulation diagrams.

Modern electrical power system is a very large scale of complex and interconnected system that the small disturbance easily would create havoc in power system stability and sustainability without operation of power system protection. In the analysis of power system protection the protection relay IED is the crucial part in order to prevent the unexpected event and maintain the integrity and security of the system. It is very useful at identifying problems with the fault relay settings or the algorithm of protection which could cause undesired operation and system disturbances. By replaying the recorded fault waveform which generated from the testing devices, the unexpected performance of the relay can be changed through the resetting of the parameters. Such analysis is complicated and expertise knowledge is usually required. Through such test running time of testing devices would usually demand very high cost. At the same time analysis of recognize and categories the faults to determine fault location and record data about fault level and fault resistance take lots of human resources in order to evaluate the correctness of the relay operation for a fault. The objective of this paper is to verify the performance of the relay IED through post-mortem analysis, the completion of design such system will help with operational decision making while saving working hour as well as the cost of running time of testing devices.

Large amounts of software are running on what is considered to be legacy platforms. These systems are often business critical and cannot be phased out without a proper replacement. The generations of developers that have developed, maintained and supported these systems are leaving the workforce leaving an estimated shortfall of developers in the near time. Migration of these legacy applications can be troublesome due poor documentation and estimating the sizes of the projects is nontrivial. Expert estimates are the most common method of estimation when it comes to software projects but the method is heavily relying on the experience, knowledge and intuition of the estimator. The use of a complementary estimation method can increase the accuracy of the estimation. This thesis constructs a meta model that combines enterprise architecture concepts with the COCOMO II estimation model in order to utilize the benefits of architectural overviews and tested models with the purpose of supporting the migration process. The study proposes a method combining expert cost estimation with model based estimation which increases the estimation accuracy. The combination method on the four project samples resulted in a mean magnitude of relative error of 10%.

In the coming years, the LV grid is expected to be updated to become a 'smart grid'. More monitoring and control mechanisms will be implemented allowing a more exible market and more ecient problem solving. This thesis investigates the possibility to use Service Level Agreement contracts as a tool to actively and automatically monitor quality of service in the low voltage grid. To this end, a thorough study of the already existing automated SLA monitoring systems, designed for telecommunication and e-business, is made, nding inspiration on how it should be implemented specically for the LV grid. It is concluded that in theory, it should be possible to create an automated SLA monitoring platform for the LV grid. Subsequently a conceptual framework is proposed for the automated SLA monitoring platform. In a next step of development, the proposed framework is implemented in a Java-code agent based programming environment (JACK). The program is surrounded by XML and txt inputs and outputs, increasing its exibility to communicate with other systems. Finally, the programmed automated SLA monitoring platform is put to the test and several proposals are highlighted on how the program might be used. A second topic in this master thesis is the analysis of the Grid4EU demo 2 project in the Uppsala region (about 80 km north of Stockholm). This project envisions a smart grid, constructed with elements provided by several partners in the Grid4EU consortium. To present the smart grid architecture in a clear, universally understandable and standardized way, the SGAM model is used to represent the Demo 2 smart grid architecture.

This thesis deals with direct generated electricity for the Swedish and Norwegian railway systems. The form of renewable energy sources that are presented in this thesis is hydropower and a small part is about wind power. Älvkarleby hydropower plant could give redundancy to the Swedish railway system and at the same time solve that problem of locations for static converters close to Stockholm since the land areas close to Stockholm are expensive [14]. A conversion of 50 Hz generators into 16.66 Hz generators in Älvkarleby hydropower plant could lower the pressure on the nearby converter stations which this thesis shows, see Table 6.6. The conversion of a part in Älvkarleby hydropower plant would also strengthen the Swedish railway grid as can be seen in Figure 6.11 and Figure 6.12. If a malfunction would happen in Häggvik converter station as the case was in the fall 2008 [35] and Älvkarleby is functioning it would be possible to have train traffic running. The simulation preformed in this thesis shows that it is possible to have reduced traffic and still have the voltage levels in an acceptable range, see Figure A 4.3 and Figure A 4.4. In 2009 the "132 kV power flow control system" will be introduced for the Swedish railway system. This control system together with direct generation by hydropower could make the idea of hydropower generation attractive as one alternative renewable energy source. Both Norway and Sweden have similar railway systems. The 16.66 Hz electricity price is increasing in Norway and that is one reason why JBV (Jernbaneverket, a company that owns the Norwegian railway grid) chose to renovate one of their two hydropower plants that generates low frequency electricity for the railway. The renovation plans show that JBV sees a profit in renovating their existing low frequency hydropower plants. These aspects are strong arguments to why a reintroduction of hydropower in Sweden could be one alternative solution to more static converters, when dealing with the problem of increasing power consumption.

As a promising technology, wireless sensor networks have a wide range of applications. However, the development of wireless sensor networks is stillin face of multiple challenges. Among these challenges, the privacy issue is acritical parameter involved in providing secure and reliable services and attracts much attention from researchers and engineers. In the last decade, alarge number of privacy solutions for wireless sensor networks have been proposed. However, most of them are taken as additional secure functionality blocks rather than being integrated in the original sensor network designs. In this thesis project, we will focus on the privacy assessment of a parallel distributed detection network, which represents a simplied physical-layer of wireless sensor networks. The security threat is assumed to come from a passive eavesdropper. Four privacy leakage criteria are proposed to evaluate the privacy issue of the distributed detection network in dierent scenarios. As references, the privacy leakages are evaluated by dierent criteria when the distributed detection system is optimized in the perspectives of Bayesian detection theory and information theory without considering the presence of the eavesdropper. Then, we propose the corresponding privacy-concerned distributed detection systems. Comparisons to the optimal detection systems are performed and they reveal the trade-off between privacy leakage suppression and detection performance degradation.

No description available.