Five-level selective harmonic elimination PWM strategies and multicarrier phase-shifted sinusoidal PWM: A comparison

The multicarrier phase-shifted sinusoidal pulse-width modulation (MPS-SPWM) technique is well-known for its important advantage of offering an increased overall bandwidth as the number of carriers multiplied with their equal frequency directly controls the location of the dominant harmonics. In this paper, a five-level (line-to-neutral) multilevel selective harmonic elimination PWM (MSHE-PWM) strategy based on an equal number of switching transitions when compared against the previously mentioned technique is proposed. It is assumed that the four triangular carriers of the MPS-SPWM method have nine per unit frequency resulting in seventeen switching transitions for every quarter period. Requesting the same number of transitions from the MSHE-PWM allows the control of sixteen non-triplen harmonics. It is confirmed that the proposed MSHE-PWM offers significantly higher converter bandwidth along with higher modulation operating range. Selected results are presented to confirm the effectiveness of the proposed technique

A Seven-level defined selective harmonic elimination PWM strategy

Selective harmonic elimination pulse-width modulation (SHE-PWM) techniques offer an optimized control approach for a given converter and are therefore suitable for the low switching frequency high-power applications. Optimization techniques can be successfully used to obtain the solutions of the equations defining the SHE-PWM waveform. In this paper, a seven-level multilevel strategy (MSHE-PWM) defined on the line-to-neutral basis and based on a ratio of a variable number of angles distributed over three levels to be able to calculate the transition points is reported. The technique provides eighteen switching transitions for every quarter period in the standard modulation index range. In the overmodulation region, this can be changed in order to increase the gain of the modulator which in turn results in a compromised bandwidth. The switching angles as a function of the modulation index are reported for the standard as well as the overmodulation range. Selected simulation results are presented to verify the effectiveness and feasibility of the proposed method

Learning Renewable Energy by Scratch Programming

Scratch is a simple, media-rich programming language that has been developed to support self-directed learning through exploration, tinkering and collaboration with peers. It is being used more and more from teachers and students as a tool for building scientific models and evaluating students’ behavior in schools. Students, while sharing interactive projects, develop skills in areas such as acquisition and development of concepts, problem solving abilities, creative thinking, working collaboratively and all of that in a playful spirit. In this paper, we present Scratch as a useful tool for teaching renewable energy issues, mainly between the ages of 11 and 16, in order students to develop an effective understanding through interactive sustainability projects and to cultivate awareness and attitudes towards energy sustainability with new media. We also present how students can work on renewable energy and its types and control the experiments about solar and wind energy using Scratch. The key design goal of the project is to deep students’ understanding in the world of renewable energy and to help students in interacting with solar and wind energy experiments

Learning Renewable Energy by Scratch Programming

Scratch is a simple, media-rich programming language that has been developed to support self-directed learning through exploration, tinkering and collaboration with peers. It is being used more and more from teachers and students as a tool for building scientific models and evaluating students’ behavior in schools. Students, while sharing interactive projects, develop skills in areas such as acquisition and development of concepts, problem solving abilities, creative thinking, working collaboratively and all of that in a playful spirit. In this paper, we present Scratch as a useful tool for teaching renewable energy issues, mainly between the ages of 11 and 16, in order students to develop an effective understanding through interactive sustainability projects and to cultivate awareness and attitudes towards energy sustainability with new media. We also present how students can work on renewable energy and its types and control the experiments about solar and wind energy using Scratch. The key design goal of the project is to deep students’ understanding in the world of renewable energy and to help students in interacting with solar and wind energy experiments

Optimised inverter sizing in the UK

Optimal inverter sizing strategies in the UK are investigated in this paper, considering both the specific climate and the detailed inverter dynamic characteristics. A model of a PV system linked to an inverter is developed to assess and optimise how the different factors influence the correct sizing of a given PV system. Inverter efficiency changes up to 3% as a funtion of input voltage which needs to be considered in inverter sizing. The environmental data with time resolution higher than 10 minutes is recommended since low frequency data cannot guarantee accurate optimal sizing of inverter. Over-sizing the PV array rated power 10% to 40% with respect to the inverter nominal power appears to achieve the optimisation of inverter sizing in the UK

Carbon footprint of polycrystalline photovoltaic systems

The environmental and energy parameters of Photovoltaic (PV) systems play a very important role when compared to conventional power systems. In the present paper, a typical PV-system is analyzed to its elements and an assessment of the material and energy requirements during the production procedures is attempted. A Life Cycle Analysis (LCA) is being performed on the production system of photovoltaics. Energy and environmental analyses are extended to the production of the primary energy carriers. This allows having a complete picture of the life cycle of all the PV-components described in the present study. Four different scenarios are examined in detail providing every possible aspect of scientific interest involving polycrystalline PV systems. In order to obtain concrete results from this study, the specific working tool used is the Eco-Indicator ’95 (1999) as being reliable and widely applied and accepted within LCA community. A process that relates inventory information with relevant concerns about natural resource usage and potential effects of environmental loadings is attempted. Large-scale PV-systems have many advantages in comparison with a conventional power system (e.g. diesel power station) in electricity production. As a matter of fact, PV-systems become part of the environment and the ecosystems from the moment of their installation. Carbon Footprints of various PV-systems scenarios are greatly smaller than that of a diesel power station operation. Further technological improvements in PV module production and in the manufacture of Balance-of-System components, as well as extended use of renewable energy resources as primary energy resources could make Carbon Footprint of PV-systems even smaller. Extended operational period of time (O.P.T.) of PV-systems determined by system reliability should be given special attention, because it can dramatically mitigate energy resources and raw materials exploitation

Multiple sets of solutions for harmonic elimination PWM bipolar waveforms: Analysis and experimental verification

Multiple sets of solutions for the selective harmonic elimination pulse-width modulation method for inverter control exist. These sets present an independent solution to the same problem but further investigation reveals that certain sets may offer an improved overall harmonic performance. In this paper, a minimization method is discussed as a way to obtain these multiple sets of switching angles. A simple distortion harmonic factor that takes into account the first two most significant harmonics present in the generated waveform is considered in order to evaluate the performance of each set. The bipolar waveform is thoroughly analyzed and two cases are considered; single-phase patterns which eliminate all odd harmonics and three-phase counterparts which eliminate only the nontriplen odd harmonics from the line-to-neutral pattern but such harmonics are naturally eliminated from the line-to-line waveform. Experimental results support the theoretical considerations reported in the paper

Load matching in a direct-coupled photovoltaic system-application to Thevenin's equivalent loads

A methodology is developed for the assessment of load matching and further estimation of the optimum photovoltaic (PV) arrays arrangement over a prolonged period of time. The method calls for the calculation of the appropriate effectiveness factor defined as the ratio of the load energy over the maximum energy that can be produced by the PV array for a specific time period. The effectiveness factor depends on the PV array characteristics, the load characteristics, and the solar irradiance conditions. To produce realistic predictions for the effectiveness factor and the PV arrays arrangement with validity over long periods of time, the present statistical model describing irradiance employs a stochastic variation of solar radiation over a long period of time and not just a fixed diurnal variation as traditionally done in the past. Simulations are performed for the case of Thevenin's equivalent loads. In order to generalize the analysis, the simulation results are presented in a reduced form based on the values of the voltage and current corresponding to the maximum power of the PV array. The results are presented in multiple-curve comprehensive plots, which allow to determine the optimum photovoltaic array panel's arrangement without engaging sophisticated mathematical calculations