Maximising low voltage grid hosting capacity for PV and electric mobility by distributed voltage control

European low voltage grids host an increasing amount of energy from rooftop PV installations. Experience in Germany has shown that PV installations do not grow uniformly but with regional hot spots. Meanwhile it is widely agreed that low voltage grids should only be updated to accommodate some 90 % or less of available PV power in peak times in order to avoid extensive costs for grid reinforcement. The main limiting factor in rural distribution grids is the grid voltage. In the Austrian research project “DG DemoNet—Smart LV Grid” new approaches to deal with restricted grid capacities are analysed using active voltage control. In three pilot regions, the actual amount of installed PV is increased to reach physical limits. Voltage control schemes are developed, tested in simulations and then validated in the field. In one pilot region, electric mobility as additional future load in low voltage grids and its integration into the overall system is considered. This paper analyses the performance of the developed control approaches in simulation.     

Optimal control of LTI systems over unreliable communication links

In this paper, optimal control of linear time-invariant (LTI) systems over unreliable communication links is studied. The motivation of the problem comes from growing applications that demand remote control of objects over Internet-type or wireless networks where links are prone to failure. Depending on the availability of acknowledgment (ACK) signals, two different types of networking protocols are considered. Under a TCP structure, existence of ACK signals is assumed, unlike the UDP structure where no ACK packets are present. The objective here is to mean-square (m.s.) stabilize the system while minimizing a quadratic performance criterion when the information flow between the controller and the plant is disrupted due to link failures, or packet losses. Sufficient conditions for the existence of stabilizing optimal controllers are derived.     

CHEMICAL COAL DESULPHUR1ZATION RESEARCH IN TURKEY

Abstract

A number of methods have been developed which are used to remove the sulphur present in coal before combustion. The physical removal of pyritic sulphur by coal cleaning has been commercial practice for a number of years, but these methods do not remove organically bound sulphur, they can be applied effectively only to a limited number of coals. However, the removal of both pyritic and organically bound sulphur from coal can be effectively achieved by applying the chemical desulphurization methods. This paper gives a general review on the chemical desulphurization studies, including carbonization in different atmospheres, air oxidation, wet oxidation, Meyers Process, chlorination and extraction with the solutions of NaOH, CuCl₂ and C₂H₅OH, which were carried out using different Turkish lignites.     

Parametric analysis of flare edge rolling throat bending and asymmetric flare effects for H-plane horn radiator

In this paper, radiation characteristics of H-plane sectoral horn antenna are treated systematically by investigation of main structural design parameters and, flare edge rolling, throat bending and asymmetric flare effects. The analytical regularization method (ARM) is used to solve the problem of E-polarized wave diffraction in a fast and accurate way. The numerical procedure is initially verified by the analytical solutions, and then the calculated directivity gain patterns are demonstrated for the modeled horn antenna configurations. Proper choices of the antenna parameters, such as horn depth, aperture length, feeder waveguide width, flare angle, wall thickness, flare edge rolling and throat bending are proposed for the designers to reach high directivity gain, narrow beam width, suppressed side lobe levels, increased front-to back ratio and improved aperture efficiency.     

Improving the performance of simulated annealing in structural optimization

This study aims at improving the performance of simulated annealing (SA) search technique in real-size structural optimization applications with practical design considerations. It is noted that a standard SA algorithm usually fails to produce acceptable solutions to such problems associated with its poor convergence characteristics and incongruity with theoretical considerations. In the paper novel approaches are developed and incorporated into the standard SA algorithm to eliminate the observed drawbacks of the technique. The performance of the resulting (improved) algorithm is investigated in conjunction with two numerical examples (a 304-member braced planar steel frame, and 132-member unbraced space steel frame) designed according to provisions of the Allowable Stress Design (ASD) specification. In both examples, curves showing the variation of average acceptance probability parameter in standard and improved algorithms are plotted to verify usefulness and robustness of the integrated approaches.     

Characterization of poly(vinylferrocenium) coated surfaces and their applications in DNA sensor technology

Poly(vinylferrocenium) (PVF⁺) modified gold (Au) electrode was developed in this study for the electrochemical sensing of deoxyribonucleic acid (DNA) hybridization based on the oxidation signals of polymer and guanine, and also for the electrochemical investigation of interaction of anticancer drug, mitomycin C (MC) and DNA immobilized onto PVF⁺ modified Au electrode. PVF⁺ modified Au electrode was prepared by electrooxidation of poly(vinylferrocene) PVF at +0.7 V versus Ag/AgCl reference electrode. The polymer modified electrode and DNA immobilized polymer modified electrode were characterized by X-ray photoelectron (XPS), Fourier transform infrared-attenuated total reflentance (FTIR-ATR) and alternating current (AC) impedance spectroscopy. For application studies, differential pulse voltammetry (DPV) technique was used.     

Mechanical performance of low cement reactive powder concrete (LCRPC)

The possibility of producing a reactive powder concrete (RPC) with low cement content was aimed in the scope of this study. Cement was replaced with class-C fly ash (FA) up to 60% for this purpose. Three different curing conditions (standard water curing, autoclave curing and steam curing) were applied to specimens. Two series of RPC composites were prepared with bauxite and granite aggregates. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength and fracture energy of composites were investigated. Test results showed that, compressive strength of 200 MPa can be reached with low cement by using high-volume fly ash. Thermally treated specimens showed compressive strength beyond 250 MPa and high volume fly ash RPC have superior performance. Furthermore, compressive strength values reached up to 400 MPa with external pressure application during setting and hardening stages.     

Ultrathin polypyrrole films on self-assembled monolayers as an efficient ultramicroelectrode assay

In this work, we investigated the effect of electrodeposition of polypyrrole (PPy) films on two different self-assembled monolayers (SAMs) modified gold electrode for the electrochemical construction of ultramicroelectrode (UME). In order to obtain SAM modified surfaces, 4-mercapto-1-butanol and 11-mercaptoundecanoic acid were used. The effect of these two chains on pyrrole electropolymerization was compared. Electropolymerization of pyrrole on SAM modified Au electrode was carried out by using cyclic voltammetry (CV) and constant potential electrolysis. To investigate the UME formation, the obtained surfaces were tested in Fe(CN)₆^3−/4− redox system. UMEs were characterized using scanning electron microscopy energy-dispersive X-ray spectroscopy, attenuated total reflectance fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. The designed UME was applied as an immobilization matrix to entrap a redox protein, Hemoglobin (Hb), as a model. Direct electron transfer between this protein and the fabricated thiol modified PPy based UME was achieved, which is very challenging on bare electrode surfaces. With this study, a simple, low-cost and reproducible UME production way has been successfully accomplished and Hb modified UME is promising for different bioanalytical applications, for instance; cellular hydrogen peroxide or nitrite sensing.