Losses and cost optimisation of PV multilevel voltage source inverter with integrated passive power filters

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonNowadays, the need for more contributions from renewable energy sources is rapidly growing. This is forced by many factors including the requirements to meet the targeted reductions of greenhouse gas emissions as well as improving the security of energy supply. According to the International Renewable Energy Agency (IRENA) report 2016, the total installed capacity of solar energy was at least 227 GWs worldwide by the end of 2015 with an annual addition of about 50 GWs in 2015, making solar power the world’s fastest growing energy source. The majority of these are grid-connected photo voltaic (PV) solar power plants, which are required be integrated efficiently into the power grids to meet the requirements of power quality standards at the minimum total investment cost. For this, multilevel voltage source inverters (VSI) have been applied extensively in recent years. In practice, there is a trade-off between the inverter’s number of levels and the required size of output filter, which is a key optimisation area. The aim of this research is to propose a generic model to optimise the design number of levels for the Cascaded H-Bridge Multilevel Inverter (CHB-MLI) and the size of output filter for medium voltage – high power applications. The model is based on key measures, including inverter power loss minimisation, efficient control for minimum total harmonic distortion (THD), minimisation of total system cost and proposing the optimum size of output filter. This research has made a contribution to knowledge in the optimisation of CHB-MLI for medium-voltage high-power applications, in particular, the trade-off optimisation of the inverter’s number of levels and the size of the output filter. The main contribution is the establishment and demonstration of a sound methodology and model based on multi-objective optimisation for the considered key measures of the trade-off model. Furthermore, this study has developed a generic precise model for conduction and switching loss calculation in multilevel inverters. Moreover, it applied Genetic Algorithm (GA) optimisation to provide a complete optimum solution for the problem of selective harmonic elimination (SHE) and suggests the optimum size of output passive power filter (PPF) for different levels CHB-MLIs. The proposed trade-off optimisation model presents an efficient tool for finding the optimum number of the inverter’s levels and the size of output filter, in which the integration system is at its lowest cost, based on optimisation dimensions and applied system constraints. The trade-off optimisation model is generic and can be applied to any multilevel inverter topologies and different power applications.Taif University (TU

Flashover Voltage Prediction Models under Agricultural and Biological Contaminated Condition on Insulators

The flashover performance of contaminated insulators highly depends on the type of pollutant and its present concentration. In this paper, important agricultural salts (NaCl, K2SO4, NaHCO3, CaSO4, KHCO3, MgSO4, NH4), 2Fe (SO4)2 , 6H2O (ferrous ammonium sulphate, dust and urea) at different concentration and biological contaminants such as algae and fungi were taken as pollutants, and AC flashover behaviour of porcelain cap and pin type insulator polluted with these two different pollutants was investigated. The experiment was carried out by a semi-natural method wherein the insulator was first polluted artificially thereafter natural fog was applied to measure the wet flashover voltage. Test results indicate that the flashover voltages were affected by both soluble salts and non-soluble components deposit on the insulator surface. In case of thick contaminated layer non-soluble deposits greatly reduced the flashover voltage. Moreover, by using regression analysis four empirical models based on different variables have been developed. The empirical models developed in the present work represent a good degree of relation to predicting the flash-over voltage of naturally contaminated insulators.publishedVersio

Influence of Area and Volume Effect on Dielectric Behaviour of the Mineral Oil-Based Nanofluids

Transformer oil is conventionally used as an insulating liquid for the purpose of insulation and cooling in power transformers. The rise in the power demand has put stress on the existing insulation system used for power transmission. Nanotechnology provides an advanced approach to upgrade the conventional insulation system by producing nano-oil with enhanced dielectric characteristics. The aim of the study is to present the influence of area volume effect on the dielectric performance of mineral oil and its nanofluids. In this paper, nanofluids are prepared by dispersing two different concentrations of SiO2 nanoparticles in base transformer oil using a two-step method. The effect of area and volume is investigated on nanofluids in the laboratory using coaxial electrode configurations under different test conditions. The AC breakdown voltage and maximum electric stress is determined for the pure oil and nanofluids. The results show that the addition of SiO2 nanoparticles significantly improves the dielectric characteristics of transformer oil. Moreover, the breakdown phenomenon is also discussed to analyze the effect of nanoparticle, stressed area, and stressed volume on the dielectric strength of insulating oil. Nanofluids could be an alternative to mineral oil.publishedVersio

Assessment of Thermophysical Performance of Ester-Based Nanofluids for Enhanced Insulation Cooling in Transformers

Nanotechnology provides an effective way to upgrade the thermo physical characteris- 12 tics of dielectric oils and creates optimal transformer design. The properties of insulation materials 13 have a significant effect on the optimal transformer design. Ester based nanofluids (NF) are intro- 14 duced as an energy-efficient alternative to conventional mineral oils, and prepared by dispersing 15 nanoparticles in the base oil. This study presents the effect of nanoparticles on the thermo-physical 16 properties of pure natural ester (NE) and synthetic ester (SE) oils with temperature varied from 17 ambient up to 80 oC. A range of concentrations of Graphene oxide (GO) and TiO2 nanoparticles 18 were used in the study to upgrade the thermo physical properties of ester based oils. The experi- 19 ment for thermal conductivity and viscosity were performed using a TC-4 apparatus that follows 20 Debby’s concept, and redwood viscometer apparatus that follows the ASTM- D445 experimental 21 standard respectively. The experimental results show that nanoparticles have a positive effect on 22 thermal conductivity and viscosity of oils, while they reduce with increase in temperaturepublishedVersio

Comprehensive survey of various energy storage technology used in hybrid energy

Various power generation technologies, such as wind turbines and solar power plants, have been increasingly installed in renewable energy projects as a result of rising demand and ongoing efforts by global researchers to mitigate environmental effects. The sole source of energy for such generation is nature. The incorporation of the green unit into the power grid also results in volatility. The stabilization of frequencies is critical and depends on the balance of supply and demand. An efficient monitoring scheme called Load Frequency Monitoring (LFM) is introduced to reduce the frequency deviation from its natural state. Specific energy storage systems may be considered to improve the efficiency of the control system. The storage system contributes to the load rate, peak rushing, black start support, etc., in addition to high energy and rapid responsive features. A detailed study of different power storage systems, their current business scenario, and the application of LFM facilities, as well as their analysis and disturbance, is presented in this paper. According to the literature analysis, the current approaches can be divided into two categories: grid and load scale structures. This article also distinguishes between the organized aggregate system and the uncoordinated system control scheme, both of which have advantages and disadvantages in terms of technology.Funding: The authors would like to acknowledge the financial support from Taif University Researchers Supporting Project Number (TURSP-2020/278), Taif University, Taif, Saudi Arabia.Scopu

Optimum design of passive power filter (PPF) at the output of 5-level CHB-MLI using genetic algorithm (GA)

While harmonics have adverse effects on both power utilities and customers, harmonic filtering is considered the most widely applied method among different harmonic-mitigation techniques. Passive power filters (PPFs) are currently more economical and commonly applied than active power filters (APFs). The problem of passive power filter (PPF) design is considered to be a combinatorial optimisation problem that can be solved by applying artificial intelligence. For PPF design, heuristic methods are powerful optimisation techniques and have many advantages such as: no requirement for detailed information about the power system and ability to achieve optimum PPF design compared to the conventional method. In addition, the cost of PPF implementation can be added to the optimisation objective, which is not considered in conventional design. The Authors of this paper propose an optimisation model based on genetic algorithm (GA) to design a composite PPF. As a case study, the model is applied to find the optimum filter design at the output of 5-level cascaded H-bridge multilevel invert (CHB-MLI). MATLAB-SIMULINK is used for the modelling and simulation

A Smart ANN-Based Converter for Efficient Bidirectional Power Flow in Hybrid Electric Vehicles

Electric vehicles (EV) are promising alternate fuel technologies to curtail vehicular emissions. A modeling framework in a hybrid electric vehicle system with a joint analysis of EV in powering and regenerative braking mode is introduced. Bidirectional DC–DC converters (BDC) are important for widespread voltage matching and effective for recovery of feedback energy. BDC connects the first voltage source (FVS) and second voltage source (SVS), and a DC-bus voltage at various levels is implemented. The main objectives of this work are coordinated control of the DC energy sources of various voltage levels, independent power flow between both the energy sources, and regulation of current flow from the DC-bus to the voltage sources. Optimization of the feedback control in the converter circuit of HEV is designed using an artificial neural network (ANN). Applicability of the EV in bidirectional power flow management is demonstrated. Furthermore, the dual-source low-voltage buck/boost mode enables independent power flow management between the two sources—FVS and SVS. In both modes of operation of the converter, drive performance with an ANN is compared with a conventional proportional–integral control. Simulations executed in MATLAB/Simulink demonstrate low steady-state error, peak overshoot, and settling time with the ANN controller

A Smart ANN-Based Converter for Efficient Bidirectional Power Flow in Hybrid Electric Vehicles

Electric vehicles (EV) are promising alternate fuel technologies to curtail vehicular emissions. A modeling framework in a hybrid electric vehicle system with a joint analysis of EV in powering and regenerative braking mode is introduced. Bidirectional DC–DC converters (BDC) are important for widespread voltage matching and effective for recovery of feedback energy. BDC connects the first voltage source (FVS) and second voltage source (SVS), and a DC-bus voltage at various levels is implemented. The main objectives of this work are coordinated control of the DC energy sources of various voltage levels, independent power flow between both the energy sources, and regulation of current flow from the DC-bus to the voltage sources. Optimization of the feedback control in the converter circuit of HEV is designed using an artificial neural network (ANN). Applicability of the EV in bidirectional power flow management is demonstrated. Furthermore, the dual-source low-voltage buck/boost mode enables independent power flow management between the two sources—FVS and SVS. In both modes of operation of the converter, drive performance with an ANN is compared with a conventional proportional–integral control. Simulations executed in MATLAB/Simulink demonstrate low steady-state error, peak overshoot, and settling time with the ANN controller

Evaluation and classification of power quality disturbances based on discrete Wavelet Transform and artificial neural networks

TesisEl presente estudio de investigación se realizó con el objetivo de determinar la influencia de la autopercepción de imagen corporal en los hábitos alimentarios de estudiantes de serie 100 – 200, Escuela Profesional de Enfermería. UNSCH – 2017. Material y método: Enfoque de estudio cuantitativo, tipo de investigación aplicativo, nivel de investigación descriptivo – correlacional, diseño de investigación transversal – retrospectivo no experimental. La población estuvo compuesta por 237 estudiantes de serie 100 y 200 de Escuela Profesional de Enfermería, matriculados en el semestre 2017 - I, y la muestra fue de 185 estudiantes obtenido mediante muestreo no probabilístico-intencional. Técnica de recolección de datos fue encuesta y psicometría, y como instrumento cuestionario estructurado y test de valoración de Gardner. Resultados: En cuanto a la autopercepción de la imagen corporal, el 63.8% están satisfechos con su imagen corporal y el 36.2% insatisfechos; y en cuanto a los hábitos alimentarios: el 58,4% regular, 27,0% bueno y 14,6% malo. Conclusión: La autopercepción de imagen corporal no influye en sus hábitos alimentarios de los estudiantes de la serie 100 y 200 de la Escuela Profesional de Enfermería UNSCH 2017

OrCAD vs Matlab Simulink in teaching power electronics

The use of simulation packages in teaching power electronics plays vital part in enhancing the understanding of converter topologies. Also it plays major part in evaluating some specific characteristics like switching losses and it can also be used in the verification of some new topologies or in the optimization of some parameters. In this paper a comparison between the two software packages (OrCAD and Matlab Simulink) is presented with the focus on the main advantages and disadvantages in using both packages in teaching power electronics for undergraduate and postgraduate courses. A UPS system has been taken as a case study for both packages as it contains several power electronic converters and it is an ideal application for teaching power electronics