G.A. Taylor

Modelling, simulation and performance analysis of a PV array in an embedded environment

Photovoltaic (PV) generation involves the direct conversion of sunlight into electrical energy. In recent years it has proved to be a cost-effective method for generating electricity with minimum environmental impact. Due to the environmental and economic benefits PV generation is now being deployed worldwide as an embedded renewable energy source and extensive research is being performed in order to study and assess the effectiveness of PV arrays in Distributed Generation (DG) systems either as a potential energy source or as energy reserve in combination with other types of distributed energy resources. This paper presents the modeling and MATLAB simulation of a stand-alone polycrystalline PV Array system and investigates load following performance efficiency under various loading and weather conditions as well as suitability with regard to enhancing power supply reliability to critical loads. The modeling of the PV array that has been performed in this research using MATLAB Simulink is based on the calculation of parameters for the Thevenins equivalent circuit of each cell of the array. The standard double exponential polycrystalline cell model has been adopted for this research with solar irradiance E and ambient temperature T as the input and Thevenins voltage Vthar and Thevenins resistance Rthar as the output.

Solution of the elastic / visco-plastic constitutive equations: A finite volume approach

Abstract A novel two dimensional finite volume (FV) approach to the solution of elastic / visco-plastic solid mechanics problems is described. The numerical procedure is an extension of that developed by Fryer et al. for linear elastic materials and utilizes an unstructured mesh. The procedure is compared favorably with conventional finite element (FE) formulations with respect to both accuracy and CPU time. A number of test problems demonstrate the ability of the FV procedure to model a range of boundary constraints, in addition to mechanical and thermal loads. It might be argued from the work reported here that the FV approach shows the potential to be at least as effective as conventional FE formulations in representing nonlinear solid mechanics behavior.

Plug in to grid computing

This article discusses the potential benefits of grid computing for future power networks. It is also intended to alert the power system community to the concept of grid computing and to initiate a discussion of its potential applications in future power systems. Much like the Web, the grid can operate over the Internet or any other suitable computer networking technology. Grid computing offers an inexpensive and efficient means for participants to compete (but also cooperate) in providing reliable, cheap, and sustainable electrical energy supply. It also provides a relatively inexpensive new technology allowing the output of embedded generators to be monitored and, when necessary, controlled. Basically, the ability of grid-enabled systems to interact autonomously is vital for small generators where manned operation is likely to be viable.

Discretisation procedures for multi-physics phenomena

Procedures are described for solving the equations governing a multi-physics process. Finite volume techniques are used to discretise, using the same unstructured mesh, the equations of fluid flow, heat transfer with solidification, and solid deformation. These discretised equations are then solved in an integrated manner. The computational mechanics environment, PHYSICA, which facilitates the building of multi-physics models, is described. Comparisons between model predictions and experimental data are presented for the casting of metal components.

Mathematical modelling and performance evaluation of a stand-alone polycrystalline PV plant with MPPT facility

Photovoltaic (PV) generation has now-a-days proved to be a cost-effective method for renewable power generation with minimum environmental impact. Due to environmental and economic benefits, PV is now being widely deployed as a distributed energy resources (DER) in distributed generation systems or microgrids. Extensive laboratory-based research and simulation studies are being performed for assessing its effectiveness as DER in microgrids. Simulation studies mostly involve development of mathematical models which can account for the variation of PV output with solar irradiance and ambient temperature as well as the simulation of MPPT feature that is built in the inverters usually interfaced with the PV arrays. Simulation studies of microgrids with interconnected DERs and elaborate control schemes often warrants the development of simple and robust mathematical models for PV arrays that would pose low mathematical burden on the system, have low data storage requirements and which can be represented by standard block sets of a modelling software. At the same time, the models should be able to simulate the weather dependent electrical behaviour of the PV modules. This paper reports on the development of a DC voltage source model of a polycrystalline PV Array in MATLAB Simulink and its performance analysis under various loading and weather conditions as well as the application of the model to develop a load shedding scheme for a stand-alone PV system.

Distributed monitoring and control of future power systems via grid computing

It is now widely accepted within the electrical power supply industry that future power systems operates with significantly larger numbers of small-scale highly dispersed generation units that use renewable energy sources and also reduce carbon dioxide emissions. In order to operate such future power systems securely and efficiently it will be necessary to monitor and control output levels and scheduling when connecting such generation to a power system especially when it is typically embedded at the distribution level. Traditional monitoring and control technology that is currently employed at the transmission level is highly centralized and not scalable to include such significant increases in distributed and embedded generation. However, this paper proposes and demonstrates the adoption of a relatively new technology grid computing that can provide both a scalable and universally adoptable solution to the problems associated with the distributed monitoring and control of future power systems

Comparison of finite element and finite volume methods application in geometrically nonlinear stress analysis

A novel three-dimensional finite volume (FV) procedure is described in detail for the analysis of geometrically nonlinear problems. The FV procedure is compared with the conventional finite element (FE) Galerkin approach. FV can be considered to be a particular case of the weighted residual method with a unit weighting function, where in the FE Galerkin method we use the shape function as weighting function. A Fortran code has been developed based on the finite volume cell vertex formulation. The formulation is tested on a number of geometrically nonlinear problems. In comparison with FE, the results reveal that FV can reach the FE results in a higher mesh density.

Finite volume methods applied to the computational modelling of welding phenomena

Abstract This paper presents the computational modelling of welding phenomena within a versatile numerical framework. The framework embraces models from both the fields of computational fluid dynamics (CFD) and computational solid mechanics (CSM). With regard to the CFD modelling of the weld pool fluid dynamics, heat transfer and phase change, cell-centred finite volume (FV) methods are employed. Additionally, novel vertex-based FV methods are employed with regard to the elasto-plastic deformation associated with the CSM. The FV methods are included within an integrated modelling framework, P hysica , which can be readily applied to unstructured meshes. The modelling techniques are validated against a variety of reference solutions.

Coordinated voltage control for active network management of distributed generation

Existing approaches to the design, control and operation of 11 kV distribution networks often restrict optimal utilization. When confronting the increasing demand and growing amount of distributed generation being connected to the networks, it is essential for distribution system operators to employ new and more active network management practices. This paper presents and discusses a range of active voltage management schemes based on coordinated voltage control. These schemes can be used to improve the voltage profile in 11kV distribution networks and increase their ability to accommodate distributed generation. Technical limitations and commercial barriers are discussed. Two case studies based on EDF Energy distribution systems are presented. Both systems experienced voltage issues associated with the presence of distributed generation and innovative active control scheme trials have been installed. The functionality of each scheme is assessed based on a number of factors such as: ability of the scheme to increase network capacity, reliability and accuracy.

Flexible voltage control to support Distributed Generation in distribution networks

Increasing penetration of Distributed Generation (DG) in distribution networks significantly changes both the real and reactive power flows in the network and can create serious voltage control problems. Furthermore, traditional Automatic Voltage Control (AVC) schemes that can normally deal with the reverse power flows, are unable to cope with the voltage problems associated with the presence of DG under certain conditions. Several techniques have been deployed to improve distribution network voltage profiles in such cases, for instance network reinforcement or active voltage control with remote voltage sensing units. Another method that has been proposed and recently implemented is the SuperTAPP n+ relay scheme that is based on locally taken measurements at the substation level combined with a state estimation technique. Such an approach enables assessment of the voltage rise at the point of connection of DG and effective control of the voltage level at the substation. The first objective of this paper is to present the fundamental principles of innovative voltage control schemes for distribution networks with DG based on locally measured signals. Secondly the functionality of the most flexible scheme will be demonstrated via software simulation for a range of distribution network case studies based upon realistic EDF Energy network scenarios. Finally, the results from the modelling and analysis of the SuperTAPP n+ relay scheme and its feasible application will be discussed and detailed conclusions are presented.