Frequency Coupling in Inverter Grids Modeling the Mutual Interference of Voltage Source Inverters in Island Grids

This paper presents a model to describe the mutual frequency disturbance of meshed and interconnected voltage source inverters during transient phases. The model provides a weighted mutual frequency coupling matrix taking into account that the mutual frequency measurement disturbance decreases for increasing electric distance between the inverters (i.e. depend on the line admittance) and depends on the respective inverter’s rated power, meaning that stronger inverters have more influence than small ones on the other inverters frequency perception

NetPower DemoLab A Test Bed Infrastructure for Security and Reliability Investigations of SCADA Systems

The purpose of this paper is to present the capabilities of the new NetPower DemoLab of the Interdisciplinary Centre for Reliability and Trust at the University of Luxembourg, operated by the Systems and Control group, and to stimulate potential public or private collaborations in the area of SCADA security and reliability investigations

Compound Model of Inverter Driven Grids Stability Analysis of Island Power Grids Containing Only Voltage Source Inverters

This paper presents a structured development of a compound state space model of an inverter driven power grid. It allows to perform stability investigations on power grids, depending on the inverter parameters influencing their dynamich behavior and on the grid structure. The general approach is to separate the active components, i.e. the inverters, from the passive components, i.e. the grid, and model them separately. A state space model of a single voltage source inverter is developed and then extended into a multi-inverter model. Based on the linearized power equations of one grid branch, a matrix representation of the grid is developed, based on the sorted node incidence matrix. The grid matrix model and the multi-inverter state space model are joined into one compound control model for inverter driven power grids

Structured Analysis of Arbitrary Island Grids

This paper recapitulates an analytic control model for arbitrary island grids and presents findings on the dynamic behaviour of purely inverter driven island grids. Pole zero plots of different grid structures are presented and the influence of several inverter parameters on the grid stability is analysed. Findings show that for improved grid stability the inverter’s time constants should also relate to their rated power. Further it is shown how P-Q rotation in the droop control can improve the integration density of renewable power sources in the distribution grid

11,8-100% Rural Renewable Energy and Power Supply and its Influence on the Luxembourgish Power System

Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively small Luxembourgish electricity system is analysed (0.55 Mio Inhabitants). Current power-system-models mainly focus on larger systems, due to the unavailability of specific consumption-data. Prices and effects on the Luxembourgish power system of different supply scenarios for rural-private households are analysed. A linear optimisation for the minimum-cost of the power-supply of a village with the following renewable energy resources: wind- (max.100 kW), solar-PV- and hydrokinetic-power is made. The electricity-demand scales with the number of inhabitants and agricultural-consumers. The wind-power-potential differs with the location of the village. The solar-radiation is assumed to be the equal over the country, due to the small size of approximately 80 by 50 km. The hydrokinetic turbines complete the supply where a village is located close to a river. The minimum cost of the specific village power-supply is the result of the optimization. The installation- and maintenance-cost of each renewable technology are considered. The whole number of a rural Luxembourgish model villages private households is considered and their electricity contribution to the system is estimated for different renewable energy supply scenarios, namely from 20% to 100% renewable-energy-scenarios. For each scenario the power exchanged from the village to the grid is calculated in 15-min-steps for 9-years, the amount differs widely with the number of applied generation technologies. Due to the high share of imported electricity of about 80% in the recent years, every consideration of national power generation does not harm the supply security. Luxembourg is a good model country to analyse the high share of distributed, renewable generators, due to its structure of rural and civic regions and their effects on a central European region with a high electricity-consumption

An evaluation of performance management in the public service

M.Comm.The aim of this study is to evaluate performance management in the public service particularly within the Gauteng Department of Health. The researcher also intends to discover the attitude of employees towards performance management systems. A triangulation approach involving qualitative and quantitative analysis was adopted to ensure the validity of the constructs

Observateur et contrôle optimal (améliorer l'efficacité de la conduite automobile avec Kalman et Pontryagin)

Ce mémoire de thèse présente une méthode permettant d'améliorer laconduite automobile. Le filtre de Kalman étendu est utilisé pour identifierun modèle de la voiture. Ce filtre est particulièrement étudié afin de prendreen compte la redondance des informations et leur mesure asynchrone.Un ensemble cohérent et bon marché de capteurs - incluant accéléromètres,GPS, temps d'ouverture des injecteurs et vitesse - a été développé et installédans plusieurs véhicules. Ces mesures sont utilisées afin de reconstituer lafonction d'efficacité du moteur. Cette méthodologie peut-être utilisée pourtoute étude requérant la connaissance de cette fonction.La fonction d'efficacité est approchée par une fonction polynomiale etle modèle obtenu est la base d'une optimisation utilisant le principe dumaximum de Pontryagin.Les résultats des tests en condition réelle sont donnés et montrent l'efficicacité de l'observateur et du contrôleurThe PhD presents a combined approach to improving individual car efficiency. An optimal observer, the Extended Kalman Filter, is used to create an efficiency model for the car. Particular attention was paid to handling the asynchronous and redundant nature of the measurement data. A low-cost sensor suite developed to measure data is described. This sensor suite was installed on multiple vehicles to good success. It employsan accelerometer, gps, fuel injector timer, and Vss input to measure all the data necessary to reconstruct the car's state. This observer and sensor suite can be used as the base for any study which requires car efficiency maps, allowing research to proceed without manufacturer supplied data. Once the efficiency map is found, it is then curve-fitted in order to reduce model complexity. The simplified model is then used as a basis for optimal control through Pontryagin's Maximum Principle. Real-world test results are given, both for efficiency mapping, and for optimal control. Detailed discussion of the observer and controller is presented, in order to ease understanding and save implementation timeDIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

Towards optimal post-fault self-healing in future smart distribution grids

This paper deals with a key functionality of the future distribution smart grids namely the automatic post-fault network self-healing. To this end we propose an optimization approach that aims finding the post-fault grid topology that minimizes the amount of unsupplied energy to consumers. The approach extends existing optimization models, developed in the context of losses minimization, for our particular application and proposes ways to overcome their limitations. We prove the interest of the approach on a 33-bus benchmark distribution system as well as on a 61-bus real-life distribution grid

Distributed Generator Status Estimation for Adaptive Feeder Protection in Active Distribution Grids

This paper proposes a framework for adaptive feeder protection in distribution grids with a high amount of distributed generators (DGs) installed. The scheme adapts the feeder protection relay settings according to the changes in the connection status of those DGs that have a significant impact on the fault current. The core of the method consists in the identification of the connection status of the DGs using an iterative modified state estimation (SE) program. The approach is illustrated using a realistic 31-node distribution network model

Distribution Grid Monitoring through Pilot Injection and Successive Interference Cancellation

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large portion of the electricity demand is fed in through the distribution grid, whose good health and operational status will be important for guaranteeing grid stability. In Luxembourg, the distribution network is sparsely monitored and controlled, thus instabilities arising due to line overvoltage or DG malfunctioning are not rapidly detected and resolved. This research discusses a novel and low infrastructure methodology for online monitoring of the distribution grid. Such a tool will be increasingly necessary in order to guarantee the stability, reliability and security of the power network, as a larger and larger portion of the energy demand will be satisfied by DG in future years. In this research, advanced system identification techniques utilized in communications, such as Pseudo-Random Binary Sequences, Successive Interference Cancellation are applied to estimate the transfer function of power network propagation paths. The developed method proposes an online monitoring tool that computes grid parameters in real time during operation, without extensive infrastructure addition, by utilizing the PWM based inverters on the grid for active system identification