Quasi-Polynomial Control of a Synchronous Generator

A simple dynamic model of permanent magnet synchronous generator, that is used for electrical energy generation is investigated in this work using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. It is well known that dynamical systems with smooth nonlinearities can be embedded in a quasi-polynomial model. Quasipolynomial systems are good candidates for a general nonlinear system representation since their global stability analysis is equivalent to the feasibility of a LMI. Moreover, the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. The classical stabilizing state feedback problem for quasipolynomial systems has been extended in this work with the ability of tracking time-dependent reference signals. It is shown, that the stabilizing quasi-polynomial servo controller design is equivalent to a bilinear matrix inequality. The results are applied to the model of a synchronous generator

Calculation of the temperature of boundary layer beside wall with time-dependent heat transfer coefficient

This paper proposes to investigate the changes in the temperature of external wall boundary layers of buildings when the heat transfer coefficient reaches its stationary state in time exponentially. We seek the solution to the one-dimensional parabolic partial differential equation describing the heat transfer process under special boundary conditions. The search for the solution originates from the solution of a Volterra integral equation of the second kind. The kernel of the Volterra integral equation is slightly singular therefore its solution is calculated numerically by one of the most efficient collocation methods. Using the Euler approach an iterative calculation algorithm is obtained, to be implemented through a programme written in the Maple computer algebra system. Changes in the temperature of the external boundary of brick walls and walls insulated with polystyrene foam are calculated. The conclusion is reached that the external temperature of the insulated wall matches the air temperature sooner than that of the brick wall

Gravity-flow dominated sedimentation on the Buda paleoslope (Hungary): Record of Late Eocene continental escape of the Bakony unit

The Upper Eocene sequence of the Buda Hills consists of fluvial and shallow marine conglomerates, sandstones, bioclastic shallow-water limestone, marlstone and pelagic Globigerina marl. The succession illustrates rapid, overall subsidence of the area, from terrestrial environments to bathyal depths. Sedimentation occurred on slopes situated on the flanks of synsedimentary basement antiforms. Vertical growth of antiforms caused progressive tilting of beds, layerparallel extension by boudinage and faulting, and induced redeposition by mass flow. Antiforms are localised in the dextral Budaörs shear zone and in the Buda imbricate stack, which accommodated the dextral displacement. The latter is underlain by blind reverse faults probably merging into a detachment tault at shallow depths. These structures were formed by WNW-ESE oriented compression and NNE-SSW directed tension. The morphological expression of the imbricate stack is the SE-facing Buda slope. The Bakony unit, while "escaping" from the Alps, was bordered by a northern sinistral and a southern dextral shear zone. Synsedimentary tectonics in the Buda Hills demonstrates the style of deformation inside the escaping block, close to the southern border zone. Tectonically controlled sedimentation suggests that escape tectonics was active as early as Late Eocene time

Generalized persistent fault detection in distribution systems using network flow theory

Persistent faults are steady state anomalies with a magnitude which does not necessary trigger general protective gear. It is present in various types of distribution networks, as leak in pipe networks or as high-impedance fault in electric systems. As smart meters come into general use, distribution systems are upgraded to have advanced metering infrastructure. The amount of consumer data is thereby increased, which can be used for diagnostic purposes. Different kind of detection methods, improvements are presented in different physical domains. However, persistent fault detection lies on basic physical principles like the conservation of energy. In order to be able to develop and evaluate methods, which target basically the same problems, the notions of the well established general network theory are being used. New formal definitions are presented to handle measurement data. In this framework a general extension of Flow networks is presented which enables the detection of faults which are not present from the beginning in our model, between metered points. The solution to this problem is presented in the form of a two-stage evolutionary algorithm. Finally the working of the methods is illustrated and verified through a simple simulation based case study

Aggregation of Heterogeneous Flexibility Resources Providing Services for System Operators and the Market Participants

Power systems characterized by large, centralized generation sources and the typical flow of energy from the transmission grid to the distribution grid towards consumers are evolving. The increasing penetration of intermittent and distributed renewable energy generation is forcing system operators to increase the volume of balancing capabilities and procure flexibility services at the distribution grid level that must be supported by the aggregation of small-scale resources connected at the distribution grid. This paper suggests an aggregator framework that provides services for both operators of transmission and distribution systems while optimizes its portfolio to perform on wholesale energy trading markets too. Overlaying phases of multi-period optimization runs are proposed that incorporate stochastic renewable energy generation as well as load forecasts and, moreover, the continuously changing business context while enabling cooperation between optimization phases throughout the business process

Simulation of a balanced low-voltage electrical grid using a simplified network model

A simulation method for low-voltage balanced distribution networks is proposed in this article. The novel method of node powers is based on the general calculation technique of node voltages. By researching only balanced networks, single-phase equivalents of the three-phase system are applicable. For the description of power lines, various parameters and matrices are available. In this work a simplified model is applied by using a purely resistive one. The active power results are solved through an iterative process. A main accomplishment is that the number of iterations needed is independent of the size of the network, and the process rapidly converges. Validation of the method is performed on the IEEE European Low-Voltage Test Feeder network. The simulation results confirm the achievements described in this paper

Investigation of the elements of Rho (Rop) GTPase-depent signalling in Medicago sp. : identification of Rop guanine nucleotide exchange factors (ROPGEFs) in Medicago truncatula

Rop GTPase-dependent signalling plays a significant role in plant development as well as during the responses of plants to environmental signals. The elements of these diverse signalling pathways just started to be revealed during the last couple of years, especially in Arabidopsis thaliana. In our laboratory we aim to identify these elements from the model species Medicago truncatula in order to allow investigations of Rop GTPase-mediated signalling during Medicago-Sinorhizobium symbiosis and somatic embryogenesis. Here we report on the in silico identification of seven Rop guanine nucleotide exchange factor (RopGEF) sequences and their primary characterization including gene expression profiling in various plant organs