How Electrophilic are Ferrocenylmethyl Cations? Kinetics of their Reactions with Nucleophiles and Hydride Donors

Second-order rate constants for the reactions of the ferrocenylmethylium ions 2a - e with silyl enol ethers, allylsilanes, allylstannanes, and hydride donors have been determined photometrically and conductometrically in dichloromethane. The ferrocenylmethylium ions 2a - d (fc-CHR+, R = H, Me, Ph, An) are slightly stronger electrophiles than the tropylium ion, and their electrophilic reactivities depend only slightly on the nature of R. The bis(ferrocenyl)methylium ion 2e is a considerably weaker electrophile, comparable to the tricarbonyl(cyclohexadienyl)iron cation

Photochemical dihydrogen production using an analogue of the active site of [NiFe] hydrogenase

The photoproduction of dihydrogen (H2) by a low molecular weight analogue of the active site of [NiFe] hydrogenase has been investigated by the reduction of the [NiFe2] cluster, 1, by a photosensitier PS (PS = [ReCl(CO)3(bpy)] or [Ru(bpy)3][PF6]2). Reductive quenching of the 3MLCT excited state of the photosensitiser by NEt3 or N(CH2CH2OH)3 (TEOA) generates PS•−, and subsequent intermolecular electron transfer to 1 produces the reduced anionic form of 1. Time-resolved infrared spectroscopy (TRIR) has been used to probe the intermediates throughout the reduction of 1 and subsequent photocatalytic H2 production from [HTEOA][BF4], which was monitored by gas chromatography. Two structural isomers of the reduced form of 1 (1a•− and 1b•−) were detected by Fourier transform infrared spectroscopy (FTIR) in both CH3CN and DMF (dimethylformamide), while only 1a•− was detected in CH2Cl2. Structures for these intermediates are proposed from the results of density functional theory calculations and FTIR spectroscopy. 1a•− is assigned to a similar structure to 1 with six terminal carbonyl ligands, while calculations suggest that in 1b•− two of the carbonyl groups bridge the Fe centres, consistent with the peak observed at 1714 cm−1 in the FTIR spectrum for 1b•− in CH3CN, assigned to a ν(CO) stretching vibration. The formation of 1a•− and 1b•− and the production of H2 was studied in CH3CN, DMF and CH2Cl2. Although the more catalytically active species (1a•− or 1b•−) could not be determined, photocatalysis was observed only in CH3CN and DMF

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

During the last decade, a substantial growth in renewable, distributed energy production has been observed in industrial countries. This phenomenon, coupled with the adoption of open energy markets has signi cantly complicated the power ows on the distribution network, requiring advanced and intelligent system monitoring in order to optimize the e ciency, quality and reliability of the system. This thesis proposes a solution several power network challenges encountered with increasing Distributed Generation (DG) penetration. The three problems that are addressed are islanding detection, online transmission line parameter identi cation and system topology identi cation. These tasks are performed by requesting the DGs to provide ancillary services to the network operator. A novel and intelligent method has been proposed for reprogramming the DGs Pulse Width Modulator, requesting each DG to inject a uniquely coded Pseudo-Random Binary Sequence along with the fundamental. Islanding detection is obtained by measuring the equivalent Thevenin impedance at the inverters Point of Common Coupling, while system characterization is obtained by measuring the induced current frequencies at various locations in the grid. To process and evaluate the measured signals, a novelWeighed Least-Squares aggregation method is developed, through which measurements are combined and correlated in order to obtain an accurate snapshot of the power network parameters

Verification and Implementation of Pseudo-Random-Binary-Sequences for Online Determination of Grid Impedance Spectrum

The number of inverter based distributed power generators connected to the power network has rapidly grown in recent years. The consequence of this phenomenon is an increasingly complex distribution grid, requiring advanced and intelligent monitoring and observation tools in order to guarantee satisfactory power quality and reliability. This paper describes a novel power line impedance estimation method, implementing an innovative technique based on modifications of the Pulse Width Modulator’s pulse pattern on the inverters, in order to generate Pseudo-Random Binary Sequence based pilot signals. The stimuli are generated at different locations in the distribution grid, and detected at the transformer sub-station through cross correlation between the received distorted signal and the sequence, the parameters of the propagation channel can be estimated. Simulations in typical grid situations verify that the proposed algorithm is robust to a realistic environment and woul

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

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

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

Wideband Identification of Power Network Parameters Using Pseudo-Random Binary Sequences on Power Inverters

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

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

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