Optimal capacitor placement to minimise harmonics in power systems and software tools

Harmonics in power systems is a relatively new area of research. In view of this and the growing awareness of the quality of the electricity supply, the theory of harmonics in power systems is reviewed. The sources and the effects of harmonics are investigated. The algorithms that are used for the frequency analysis of power systems are investigated and compared. These algorithms comprise the companion circuit method, the Gauss-Seidel method, the Newton-Raphson method and the current injection method. In addition various freely and commercially available software packages for the harmonic analysis of power systems are studied and compared. For this purpose a questionnaire was sent out to software developers and suppliers. This questionnaire as well as the results of the comparative investigation are presented. A power system has many configurations due to the switching of power capacitors on to and off the power grid. Some of these configurations can result in unacceptable distortion levels. An existing state space method is investigated to analyse these configurations and an example is worked through, to illustrate how this method works. However, this state space model is only applicable to radial power systems and there have to be power capacitors at the end of every feeder amongst others. Because of these significant disadvantages of this method, a new analytical approach or theoretical foundation for the analysis of power capacitors in radial as well as meshed power systems is developed in this thesis. For this purpose the branch current and nodal voltage equations are determined. Redundant nodal voltages are eliminated from the set of branch current equations. The remaining equations and the nodal voltage equations are then combined to form a system realisation. This system realisation is still overspecified and a further reduction is done to obtain a minimal realisation of the power system. This approach is demonstrated analytically and numerically by way of five case studies. This approach is also verified by comparing it with the current injection method. Identical results are obtained with the state space approach and with the current injection method, demonstrating that the state space approach is indeed valid

Organizations in development: the changing nature of service provision in the Philippines

The Institute of Social Studies is Europe's longest-established centre of higher education and research in development studies. Post-graduate teaching programmes range from six-week diploma courses to the PhD programme. Research at ISS is fundamental in the sense of laying a scientific basis for the formulation of appropriate development policies. The academic work of ISS is disseminated in the form of books, journal articles, teaching texts, monographs and working papers. The Working Paper series provides a forum for work in progress which seeks to elicit comments and generate discussion. The series includes the research of staff, PhD participants and visiting fellows, and outstanding research papers by graduate students

Fuzzing the Internet of Things: A Review on the Techniques and Challenges for Efficient Vulnerability Discovery in Embedded Systems

With a growing number of embedded devices that create, transform and send data autonomously at its core, the Internet-of-Things (IoT) is a reality in different sectors such as manufacturing, healthcare or transportation. With this expansion, the IoT is becoming more present in critical environments, where security is paramount. Infamous attacks such as Mirai have shown the insecurity of the devices that power the IoT, as well as the potential of such large-scale attacks. Therefore, it is important to secure these embedded systems that form the backbone of the IoT. However, the particular nature of these devices and their resource constraints mean that the most cost-effective manner of securing these devices is to secure them before they are deployed, by minimizing the number of vulnerabilities they ship. To this end, fuzzing has proved itself as a valuable technique for automated vulnerability finding, where specially crafted inputs are fed to programs in order to trigger vulnerabilities and crash the system. In this survey, we link the world of embedded IoT devices and fuzzing. For this end, we list the particularities of the embedded world as far as security is concerned, we perform a literature review on fuzzing techniques and proposals, studying their applicability to embedded IoT devices and, finally, we present future research directions by pointing out the gaps identified in the review