Topology and Parameter Estimation in Power Systems through Inverter Based Broadband Stimulations

in IET Generation, Transmission and Distribution (2016)

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly ... [more ▼]

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly complicated the powerflows on the power network, requiring advanced and intelligent parameter knowledge to optimize the efficiency, quality and reliability of the system. This paper describes a method for identifying parameters associated with the power system model. In particular, the proposed algorithm in this paper addresses the line parameter and topology identification task in the scope of state estimation. The goal is to reduce the a priori knowledge for state estimation, and to obtain online information on the power system network. The proposed parameter estimation method relies on injected stimulations in the network. Broadband stimulation signals are injected from distributed generators and their effects measured at various locations in the grid. To process and evaluate this data, a novel aggregation method based on weighed least-squares will be proposed in this paper. It combines and correlates various measurements in order to obtain an accurate snapshot of the power network parameters. In order to test its capabilities, the performance of this algorithm is evaluated on a small-scale test system. [less ▲]

Hydrokinetic Micro-Power Generation in Small Rivers - a New Approach

in Renewable Energy and Power Quality Journal (2015)

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third ... [more ▼]

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third renewable energy resource, the hydropower has been already developed within the last decades and grew not significantly in the last years. Since some years the development of smaller hydrokinetic turbines increased. The smaller size of some hydrokinetic turbines enables new, unused sites to be harnessed in smaller rivers. The paper deals with the key specifications of hydrokinetic turbines and their influence on a villages’ energy supply. It introduces the concept of a turbine with variable immersion depths to exploit also locations with a varying water level. Based on historical hydrological data a propeller and oscillating hydrofoil type of hydrokinetic turbine are compared, it was found that the variable immersion depths increases the energy harvest. Furthermore, it is shown that in a generation portfolio of hydrokinetic and solar power plants an average Luxembourgish household theoretically renewable supplied has to exchange less energy with the power grid, the higher its share of hydrokinetic generation is. [less ▲]

Hydrokinetic Micro-Power Generation in Small Rivers - a New Approach

Poster (2015, March 25)

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third ... [more ▼]

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third renewable energy resource, the hydropower has been already developed within the last decades and grew not significantly in the last years. Since some years the development of smaller hydrokinetic turbines increased. The smaller size of some hydrokinetic turbines enables new, unused sites to be harnessed in smaller rivers. The paper deals with the key specifications of hydrokinetic turbines and their influence on a villages’ energy supply. It introduces the concept of a turbine with variable immersion depths to exploit also locations with a varying water level. Based on historical hydrological data a propeller and oscillating hydrofoil type of hydrokinetic turbine are compared, it was found that the variable immersion depths increases the energy harvest. Furthermore, it is shown that in a generation portfolio of hydrokinetic and solar power plants an average Luxembourgish household theoretically renewable supplied has to exchange less energy with the power grid, the higher its share of hydrokinetic generation is. [less ▲]

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

Poster (2015, March 10)

Introduction; 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 ... [more ▼]

Introduction; 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. Methodology; A linear optimisation for the minimum-cost of the power-supply of all villages with the following renewable energy resources: wind- (max.100kW), 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. Results; 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 rural Luxembourgish private households is considered and their power contribution to the system is estimated for different renewable energy supply scenarios, namely from 11,8% 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 amount of applied technologies. Discussion; 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. Conclusion; 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. [less ▲]

Using Polyurethane to Reduce the Production Cost of Hydrokinetic Turbine Foils

in Proceedings International Conference on Hydropower for Sustainable Development (2015, February 05)

Polyurethane made profiles can be used for hydrokinetic oscillating foil micro turbines to reduce their production cost. For this purpose, a NACA 0015 profile is designed with a computer aided design ... [more ▼]

Polyurethane made profiles can be used for hydrokinetic oscillating foil micro turbines to reduce their production cost. For this purpose, a NACA 0015 profile is designed with a computer aided design software and milled from aluminium. From this sample a negative mould of silicone is produced. This negative was used to produce finally polyurethane foils. Holes and grooves can be simply implemented in the negative by placing corresponding shapes made of metal within the silicone form. A massive reduction of the production cost of about 1600 Euro for a polyurethane (PUR) foil of 1000 mm length compared to an aluminium foil of the same shape is accomplished. [less ▲]

Integration of Distributed Renewable Generators in the Luxembourgish Power System

Poster (2014, September 08)

The amount of renewable generators increases worldwide. With the higher share of renewable resources in a system, simultaneously the alternating power generation increases. To understand the intermittent ... [more ▼]

The amount of renewable generators increases worldwide. With the higher share of renewable resources in a system, simultaneously the alternating power generation increases. To understand the intermittent influence of the three main renewable technologies, namely windpower, solarpower and hydropower, energy balances of larger regions and the corresponding renewable, distributed generation has to be estimated to understand their generators’ influence on a system. In the following Luxembourg is considered. [less ▲]

Horizontally Oscillating Hydrofoil-River-Turbine with Variable Immersion Depth

Scientific Conference (2014, May 22)

Motivated by the unused hydrokinetic potential of smaller European rivers and creeks we develop a horizontally oscillating hydrofoil turbine to exploit those resources. Based on the work of T. Kinsey and ... [more ▼]

Motivated by the unused hydrokinetic potential of smaller European rivers and creeks we develop a horizontally oscillating hydrofoil turbine to exploit those resources. Based on the work of T. Kinsey and Prof. G. Dumas of the Laval University, Canada, on vertically oscillating hydrofoils we adapt and improve the technology to the resources especially given in the country of Luxembourg in inner Europe. Currently, the energy of rivers is mainly harnessed and transformed in electricity by the well-known barrage type of hydropower plants. This type of hydropower plant becomes harder to implement, since the protection of the natural river flow and the protection of fishes and other animals becomes more important in Europe (see also Recovery of the European Eel Stock). The passage through an ordinary barrage turbine can lead to “very high mortality, notably on migrating silver eels”. Therefore other technologies have to be used to harness the still available rivers energy, namely hydrokinetic turbines. The field of hydrokinetic river turbines is in the beginning to evolve and first projects were implemented in the United States and Europe, harnessing large rivers and tidal currents. But there are fewer approaches available for smaller rivers with varying flow conditions, since the current propeller based concepts need a certain river depths and speed to generate electricity. Furthermore, it could be useful to implement controllable turbines, so that they serve the consumers need but do not lead to peaks in an energy systems balance, which have to be damped with other technologies, for example storages or throttle processes in thermal power plants. The hydrokinetic turbine, presented in this paper is fully controllable; its angle of incidence and its oscillation frequency can be controlled. The advantage of the full control of the motion of the moving hydrofoil is an improved efficiency of the power extraction from the seasonal but also daily varying flow conditions of smaller creeks. Furthermore we can answer with a varying power output to the altering consumers need. We can generate the power needed, once the dependence between oscillation frequencies, variation of the angle of incidence and the power output is derived. Operating the system, fixed to a raft, hold at a position floating on a river, we can also answer to the varying depth of the hydro resource. A simple mechanism can vary the immersion depth of the hydrofoil and adapt the harnessed flow cross-section to the current river conditions. This mechanism enables the new turbine concept to harness currently not useable hydro resources, which were limited by their minimum water depth. Furthermore the system can be protected from dangerous flood conditions with this lifting and lowering mechanism. We expect that we can contribute with this horizontally oscillating hydrofoil-river turbine to a higher share of hydropower generation in the field of micro generation. We are aiming on a concept which is modular (consisting of low kW range single modules) and can be adapted to the rivers size and the consumers’ needs. We will present the specifications of our idea which is currently on the way to be setup in our lab, to prove the controllability and want to present the physical restrictions and potentials for several flow conditions. [less ▲]

Online Determination of Grid Impedance Spectrum through Pseudo-Random Excitation of a Pulse Width Modulator

in Renewable Energy and Power Quality Journal (2014)

The last decade has seen a dramatic rise in renewable energy converters connected to the grid, consisting mostly of intermittent distributed generators on the medium or low voltage grid. Due to this ... [more ▼]

The last decade has seen a dramatic rise in renewable energy converters connected to the grid, consisting mostly of intermittent distributed generators on the medium or low voltage grid. Due to this evolution in energy transmission, improved monitoring and control of the distribution grid is becoming mandatory in order to efficiently integrate the new power sources and guarantee power quality, efficiency and reliability. Our paper describes a reliable and precise power grid impedance estimation method using an innovative scheme to control the Pulse Width Modulator’s pulse pattern on the inverters, in order to inject broad spectrum identification patterns. The generated harmonics and inter-harmonics will allow the online computation of the complete spectrum of the grid impedance at the Point of Common Coupling during normal operation. Simulations in typical grid situations verify that the proposed algorithm is robust to a realistic environment and can be used for automated feedback control. [less ▲]

Hydrokinetic and Solar Energy Contribution to a Reliable Energy Supply

Poster (2013, November 18)

Modular Hydrokinetic Micro Generation

Poster (2013, October 07)