Modelling and power quality analysis of a grid-connected solar PV system

Increased concern about global warming coupled with the escalating demand of energy has driven the conventional power system to be more reliable one by integrating Renewable Energies (RE) in to grid. Over the recent years, integration of solar PV forming a gridconnected PV is considered as one of the most promisingtechnologies to the developed countries like Australia to meet the growing demand of energy. This rapid increase in grid connected photovoltaic (PV) systems has made the supply utilities concerned about the drastic effects that have to be considered on the distribution network in particular voltage fluctuations, harmonic distortions and the Power factor for sustainable power generation. However, irrespective of thefact that the utility grid can accommodate the variability of load or irregular solar irradiance, it is essential to study the impact of grid connected PV systems during higher penetration levels as the intermittent nature of solar PV adversely effects the grid characteristics in meeting the load demand. Hence, keeping this in track, this paper examines the grid-connected PV system considering a residential network of Geelong region (38◦.09' S and 144◦.21’ E) and explores the level of impacts considering summer load profile with a change in the level of integrations. Initially, a PV power system network model is developed in Matlab-Simulink environment and the simulations are carried out to explore the impacts of solar PV penetration at low voltage distribution network considering power quality (PQ) issues such as voltage fluctuations, harmonics distortion at different load conditions.

The social gradient of fractures at any skeletal site in men and women: data from the Geelong Osteoporosis Study Fracture Grid.

Age-specific and age-standardized associations between socioeconomic status (SES) and fractures in adults showed a social gradient of fracture, irrespective of fracture site. Compared to the highest SES, males in the lowest SES group had a sixfold increased odds for any fracture, whilst females had a twofold increased odds.

Severe plastic deformation of TWIP steel

The severe plastic deformation of a Twinning Induced Plasticity (TWIP), 0.61C-22.3Mn-0.19Si-0.14Ni-0.27Cr (wt. %) steel by Equal Channel Angular Pressing (ECAP) at elevated temperatures was used to study the deformation mechanism as a function of accumulated strain and processing parameters. The relationship between the microstructures after different deformation schedules of ECAP at the temperatures of 200, 300 and 400oC, strain hardening behavior and mechanical properties was studied. The best balance between strength and ductility (1702 MPa and 24%) was found after 2 passes at 400oC and 300oC of ECAP. It was due to the formation of deformation microbands and twins in the microstructure. The twinning was observed after all deformation schedules except after 1 pass at 400oC. The important finding was the formation of twins in the ultrafine grains. Moreover, the stacking faults were observed in the subgrains with the size of 50nm. It is also worth mentioning the formation of nano- twins within the micro-twins at the same time. It was found that the deformation schedule affects the dislocation substructure with formation of deformation bands, cells, subgrains, two variants of twins that, in turn, influence the strain-hardening behavior and mechanical properties. Keywords: Twinning Induced Plasticity steels; Equal Channel Angular Pressing; mechanical properties; transmission electron microscopy; micro/nano twins; dislocation substructure.

A novel distributed algorithm for power loss minimizing in Smart Grid

Because power generation of renewable resources are unstable and demands of the customers are time-varying, the supply power and demands of the customers are always unequal. To meet the demands of the customers, power is transmitted from primary power generation to secondary power generation. It will cause high power loss. To solve this problem, a distributed algorithm is proposed in this paper. By using the algorithm, the micro-grids are able to exchange power with their neighbors so as to minimize the total power losses of the smart grid. Moreover, communication overhead (bandwidth) is reduced, comparing with centralized algorithm. Through computer simulations, we demonstrate that the proposed algorithm can lead to near-optimal result for alleviating the average power loss per micro-grid and reduce the communication overhead significantly in contrast with the centralized approach.

Agent-based smart grid protection and security

The vision of a smart grid is to provide a modern, resilient, and secure electric power grid as it boasts up with a highly reliable and efficient environment through effective use of its information and communication technology (ICT). Generally, the control and operation of a smart grid which integrate the distributed energy resources (DERs) such as, wind power, solar power, energy storage, etc., largely depends on a complex network of computers, softwares, and communication infrastructure superimposed on its physical grid architecture facilitated with the deployment of intelligent decision support system applications. In recent years, multi-agent system (MAS) has been well investigated for wide area power system applications and specially gained a significant attention in smart grid protection and security due to its distributed characteristics. In this chapter, a MAS framework for smart grid protection relay coordination is proposed, which consists of a number of intelligent autonomous agents each of which are embedded with the protection relays. Each agent has its own thread of control that provides it with a capability to operate the circuit breakers (CBs) using the critical clearing time (CCT) information as well as communicate with each other through high speed communication network. Besides physical failure, since smart grid highly depends on communication infrastructure, it is vulnerable to several cyber threats on its information and communication channel. An attacker who has knowledge about a certain smart grid communication framework can easily compromise its appliances and components by corrupting the information which may destabilize a system results a widespread blackout. To mitigate such risk of cyber attacks, a few innovative counter measuring techniques are discussed in this chapter.

Modelling of the stiffness evolution of truss core structures damaged by plastic buckling

A finite element study based on 1D beam element model is performed in order to investigate the mechanical behavior of an elasto-plastic beam loaded in axial compression over its buckling limit. The mode of loading is related to the damage of truss-cored beams in truss-cored laminates. The analysis takes into account the effects of geometry and material properties. The results of the FEM analysis are used for developing a simple mechanical model based on the basic Euler-Bernoulli beam theory and accounts for the beam compressibility. The model uses phenomenological functions containing parameters related to the basic material and geometrical properties. The presented model is developed in the form of closed solution which does not require complex numerical methods or extensive parametric studies. Predictions of the compressive stiffness degradation of truss-cored composites are made with the proposed model and compared with the results of FEM simulations. The error of the stiffness prediction with respect to the FEM results is within 10% over a 5 fold range of stiffness.

New insights into the thermal behaviour of organic ionic plastic crystals: magnetic resonance imaging of polycrystalline morphology alterations induced by solid-solid phase transitions

Organic ionic plastic crystals (OIPCs) show strong potential as solid-state electrolytes for lithium battery applications, demonstrating promising electrochemical performance and eliminating the need for a volatile and flammable liquid electrolyte. The ionic conductivity (σ) in these systems has recently been shown to depend strongly on polycrystalline morphology, which is largely determined by the sample's thermal history. [K. Romanenko et al., J. Am. Chem. Soc., 2014, 136, 15638]. Tailoring this morphology could lead to conductivities sufficiently high for battery applications, so a more complete understanding of how phenomena such as solid-solid phase transitions can affect the sample morphology is of significant interest. Anisotropic relaxation of nuclear spin magnetisation provides a new MRI based approach for studies of polycrystalline materials at both a macroscopic and molecular level. In this contribution, morphology alterations induced by solid-solid phase transitions in triisobutyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1444FSI) and diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate (P1224PF6) are examined using magnetic resonance imaging (MRI), alongside nuclear magnetic resonance (NMR) spectroscopy, diffusion measurements and conductivity data. These observations are linked to molecular dynamics and structural behaviour crucial for the conductive properties of OIPCs. A distinct correlation is established between the conductivity at a given temperature, σ(T), and the intensity of the narrow NMR signal that is attributed to a mobile fraction, fm(T), of ions in the OIPC. To explain these findings we propose an analogy with the well-studied relationship between permeability (k) and void fraction (θ) in porous media, with k(θ) commonly quantified by a power-law dependence that can also be employed to describe σ(fm).

Structure and dynamics in solid state sodium ion electrolytes based on organic ionic plastic crystals

 The investigation of solid state sodium ion electrolytes based on Organic Ionic Plastic Crystals were carried out for potential use in the electrochemical devices such as batteries.

Insights into the transport of alkali metal ions doped into a plastic crystal electrolyte

The application of organic ionic plastic crystals (OIPCs) as a new class of solid electrolyte for energy storage devices such as lithium batteries and, more recently, sodium batteries is attracting increasing attention. Key to this is achieving sufficient target ion transport through the material. This requires fundamental understanding of the structure and dynamics of OIPCs that have been doped with the necessary lithium or sodium salts. Here we report, for the first time, the atomic level structure and transport of both lithium and sodium ions in the plastic crystalline phases of an OIPC diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate. These molecular dynamics simulations reveal two types of coordination geometries of the alkali metal ion first solvation shells, which cooperate closely with the metal ion hopping motion. The significantly different ion migration rates between two metal ion doped systems could also be related to the differences in solvation structures.

A study of phase behavior and conductivity of mixtures of the organic ionic plastic crystal N-methyl-N-methyl-pyrrolidinium dicyanamide with sodium dicyanamide

We report on the thermal, structural and conductivity properties of the organic ionic plastic crystal (OIPC) N-methyl-N-methyl-pyrrolidinium dicyanamide [C1mpyr][N(CN)2] mixed with the sodium salt Na[N(CN)2]. The DSC thermal traces indicate that an isothermal transition, which may be a eutectic melting, occurs at ~ 89 °C, below which all compositions are entirely in the solid phase. At 20 mol% Na[N(CN)2], this transition is the final melt for this mixture, and a new liquidus peak grows beyond 20 mol% Na[N(CN)2]. The III- > II solid-solid phase transition continues to be evident at ~- 2 °C. The microstructure for all the mixtures indicated a phase separated morphology where precipitates can be clearly observed. Most likely, these precipitates consist of a Na-rich second phase. This was also suggested from the vibrational spectroscopy and the 23Na NMR spectra. The lower concentrations of Na[N(CN)2] present complex 23Na MAS spectra, suggesting more than one sodium ion environment is present in these mixtures consistent with complex phase behavior. Unlike other OIPCs where the ionic conductivity usually increases upon doping or mixing in a second component, the conductivity of these mixtures remains relatively constant and above 10- 4 S cm- 1 at ∼ 80 °C, even in the solid state. Such high conductivities suggest these materials may be promising to be used for all solid-state electrochemical devices.

Enhanced ionic mobility in organic ionic plastic crystal - dendrimer solid electrolytes

We report the first study of the characterisation of the organic ionic plastic crystal (OIPC) N-ethyl-N-methylpyrrolidinium tetrafluoroborate (C2mpyrBF4) upon mixing with a dendrimer additive. Whereas previous reports of OIPC composite formation (i.e. with ceramics and polymers) have typically reported a decrease in the conductivity when lithium salt had been added, the addition of dendrimer is shown to lead to a substantial enhancement in the lithium containing system, approaching 3 orders of magnitude at 30°C. Mechanical analysis indicates that dendrimer addition leads to a softer more ductile material while microscopy shows that the dendrimer is uniformly distributed and that the crystal microstructure is substantially disrupted, ultimately adopting a dendritic microstructure at 1mol% dendrimer content. Thermal analysis indicates a new phase in the lithium OIPC system, the crystallisation of which is suppressed in the presence of dendrimer. Instead, a decrease in the phase transition enthalpies indicates a large increase in the amorphous component of the Lithium OIPC, particularly for the most conductive system -C2mpyrBF4 +10mol% LiBF4 +0.1mol% dendrimer. Variable temperature powder X-ray diffraction confirms the presence of a new distinct phase and its absence in the presence of dendrimer. A change in the progression of the thermal phase behaviour of the OIPC in the presence of dendrimer is also shown, exhibiting the phase I (high temperature) structure at temperatures below the phase II-I transition.