An Assessment Framework for PV Parallel MPPT Configuration with a New Utilization for UIPS Loads

The prevalence rate of photovoltaics (PV)-based generation systems has increased by more than 15 folds in the last decade, putting it on the top compared to any other power generation system from the expandability point of view. A portion of this huge expansion serves to energize standalone remote areas. Seeking improvements from different aspects of PV systems has been the focus of many studies. In the track of these improvements, parallel MPPT configuration for PV standalone systems have been introduced in the literature as an alternative to a series configuration to improve the overall efficiency of standalone PV systems. However, this efficiency improvement of the parallel MPPT configuration over the series one is not valid for any standalone application, therefore an assessment procedure is required to determine the most efficient MPPT configuration for different standalone applications. Therefore, in this study, an assessment procedure of parallel MPPT is conducted to demonstrate the suitability of utilizing such a configuration compared to series one, based on load daytime energy contributions. This assessment will help PV system designers to determine which MPPT configuration should be selected for applications under study. Furthermore, a new utilization of parallel MPPT configuration is introduced for operating universal input power supply (UIPS) loads to eliminate the inverter stage, thereby increasing the overall system efficiency and reliability. Finally, a systematic procedure to size the complete system is introduced and reinforced by a sizing example.

Mathematical Modeling of Knowledge-Intensive Products Export Energy Costs

This article presents the mathematical modeling of export energy costs. The knowledge-intensive products export energy costs are a set of financial, material, labor costs and resources consumption. Export costs are a multilevel system of indicators. The author sets out the order of mathematical modeling. At the first stage, the main trends in reducing export energy costs are identified. A set of integrated logistics support measures is modeled. The modeling of knowledge-intensive products export energy costs is a system of technical and economic indices and a cost value dependance: Maintenance and Repair, Material and Technical Maintenance, Business Model of After-Sales Service, Formation of the Cost of Insurance and Investment Management Strategy. Formulas, practical calculation examples and graphs are presented. The Ishikawa systematic analysis method is used to visualize data and dependence relations. The author's mathematical modeling of knowledge-intensive products export costs includes the calculation of integrated logistic support costs. Exporting countries require a high level of technical products efficiency. It has been established that "the more complex a knowledge-intensive products is, the higher the reliability of systems is". Reliability indices are basic. The author's scientific study confirms a hypothesis of the knowledge-intensive products export feasibility only with high reliability and efficiency factors. The author developed a set of integrated logistical support measures for knowledge-intensive products.

A Discrimination Method Between Transformer Inrush and Fault Current Based on Chromatic Monitoring

or successful transformer differential protection employment, correct discrimination between inrush current and fault current is essential. It is one of the main focuses of research and one of the main challenges for transformer protection. In this paper, a discrimination method based on utilizing chromatic monitoring of the box dimension algorithm outcome curve for transformer differential current in time-domain analysis is proposed. The x-L chromatic mapping is employed for general detection of fault cases, while the x-y chromatic mapping result is used for distinguishing inrush current from the fault current cycles. The preliminary results show that the proposed method can effectively provide correct discrimination of the current type within quite a short time and thus help in providing efficient decision-making supportive protection tool.

Management of a Dual-Bus AC+DC Microgrid Based on a Wind Turbine with Double Stator Induction Generator

The topology and management of a sustainable dual-bus, AC and DC, microgrid designed to operate connected to a weak grid is presented. AC+DC hybrid microgrids are a robust and cost-competitive solution for poorly connected areas, as can be found in rural or island electrification. The versatile microgrid proposed in this work is developed around a wind turbine based on a particular induction generator with double stator winding and squirrel cage rotor (DWIG). This singular generator is especially suitable for a combined AC+DC coupled microgrid application. One of its stator windings is coupled to the DC bus via a controlled AC/DC converter. The other is directly connected to the AC bus, only during the periods of abundant wind resource. The DWIG is complemented with photovoltaic panels and a hybrid energy storage system, comprising flow batteries assisted by supercapacitors, which converge to the DC Bus. The DC bus exchanges power with the AC bus through an interlinking inverter. The article describes the topology and details the operation of its Supervisory Control system, which gives rise to the five operating modes of the proposed AC+DC DWIG based microgrid. Its performance under different generation conditions and load regimes is thoroughly assessed by simulation.

Comparative Analysis of Motorcyclists’ Gaze Behavior in Different Road Environments

While car drivers consist the vast majority of road users, motorcycle drivers are considered among the most vulnerable ones with significant participation in accidents. The present study investigates the role of elements that permanently exist in the road environment and affect motorcyclist’s behavior since their usefulness requires visual contact between them and the rider during a certain period of time. Therefore, on such an occasion the riders do not monitor the road ahead which is considered as a fundamental driving task and hence the visual search and scan is not directed to the frontal view. The main objective of this paper is to identify and evaluate certain aspects of motorcyclists’ behavior influenced by exterior factors, such as observation of vertical signage or advertisement signs, by using naturalistic data. Motorcyclist’s visual behavior is evaluated via a continuous recording of his gaze, which acts as the main indicator regarding the rider’s performance, with the use of special equipment under naturalistic riding conditions. The selection of a naturalistic method permits continuous data recording, producing real-time data. Thus, the results are reliable and valid to the maximum possible extent. This research is based on a medium-scale experimental procedure that took place in three different road sections in Western Greece. A number of 11 motorcyclists participated in the study. The present research may be used as a tool to improve road infrastructure and to identify attitudes that pose a risk to rider’s safety aiming to the creation of a safer road environment, which will lead to less fatal and serious accidents.

Performance of Neutral Point Clamped Five Level Inverter Using Space Vector Modulation Control Fed by DPC-VF-SVM Rectifier

The purpose of this paper is to develop a control and regulation method for the input DC voltage of a five level neutral point clamping (NPC) inverter feeding a induction motor. In this context, the authors propose in the first part, the control strategy of three-phase pulse width modulation rectifier, they propose the virtual flux-based direct control (DPC_VF) with vector modulation (SVM), this method is applied for the enhancement of network power quality by compensation of harmonic currents produced by an non linear load, and good regulation of DC-bus voltage. The second part of the paper is dedicated to the presentation of the model of the three phase, five-level NPC voltage source inverter with its space vector modulation (SVM) control method. The performance of the proposed strategy in terms of out-put voltage and THD has studied successfully and shown using MATLAB/Simulink.

A Hybrid-Mode LDO Regulator with Fast Transient Response Performance for IoT applications

A hybrid-mode low-drop out (LDO) voltage regulator with fast transient response performance for IoT applications is proposed in this paper. The proposed LDO regulator consist of two sections. First section is an analog regulator which includes a folded cascode operational amplifier to achieve good PSRR. Second section is current DAC and detectors whitch includes a cource current DAC, sink current DAC, undershoot detectors, and overshoot detectors. The current DAC and detectors are designed to obtain a low drop out and fast transient response. The proposed hybrid-mode LDO voltage regulator has been designed, simulated and layouted in Cadence using TSMC 90 nm CMOS technology. The input range of the LDO regulator is 1.2–2.0 V, and it can produces an output voltage of 1.2V. The LDO regulator achieves 58uA quiescent current, -69 PSRR @ 1 KHz noise frequency and an output voltage drop of around 60mV for a load current step of 100 mA. The final design occupies approximately 0.09 mm2.

Power Generation by Offshore Wind Turbines: An Overview on Recent Research and Developments

Wind energy is one of the most sustainable and renewable resources of power generation. Offshore Wind Turbines (OWTs) derive significant wind energy compared to onshore installations. With the established phenomena that the wind speed has been high and consistent in offshore regions, the OWTs are likely to generate more electricity compared to the onshore ones. Design and installation of OWTs require sophisticated technology due to critical ocean environment to meet the safety and serviceability criteria. This necessitates in-depth understanding of power efficiency, mechanical operations and dynamic force distributions, together with the structural and foundation stabilities. This paper presents an intensive review of the existing knowledge on each of these diversified study areas. It is observed the subject is still under development with a significant number of unsolved problems. A critical analysis and the research directions on the relevant investigations have also been included in the paper.

Numerical Investigation of the Thermal Performance of an Axially Rotating Internally Finned Receiver Tube of Parabolic Trough Concentrator

Enhancement of the thermal performance of the parabolic trough receiver tube is one of the approaches to energy sustainability. In the present work, the thermal performance of an axially rotating receiver tube equipped with internal flat longitudinal fins is studied. The effects of both the fin height and the rate of axial rotation are investigated at low values of axial Reynold’s number. The numerical analysis is held at various rotation rates using ANSYS Fluent. The numerical findings showed that the effect of the axial rotation on the internally finned receiver tube is not significant yet negative where a maximum reduction of 6% in the outlet temperature is reached in the 2mm height internally finned tube at rotation rate of N=21. However, the analysis showed that as the rotation rate increases, the temperature homogeneity between the fluid layers also increases and thus the liquid stratification phenomenon between the fluid layers is eliminated. The percentage of temperature difference between the fluid layers near the pipe center and the layers near the pipe wall reaches an optimum value of 58.4% at N=21 which is confirmed by an optimum increase of 110% in Nusselt number at the same rotation rate. However, a maximum loss of 81.6% in pressure coefficient is found in the case of the 2mm internally finned tube due to the increased turbulence. Thus, the integration of pipe axial rotation and internal fins can yield an enhancement in the heat transfer to the parabolic trough concentrator receiver tube and thus its thermal performance.

Solar Cooling Technologies in Jordan: A Technical Study

In the recent years, solar cooling technologies for buildings have garnered increased attention. This study aimed to evaluate the performance of current solar thermal and solar photovoltaic (PV) air-conditioning technologies. Hence, the annual heating/cooling load profile and energy consumption of a reference building in the climate of Aqaba, Jordan were simulated using the TRNSYS software. The solar thermal and solar PV air-conditioning systems were designed and simulated to compensate the cooling demands. It was found that the annual cooling energy accounted for 96.3 % of the total annual energy demand (heating plus cooling) of the reference building. The solar PV and solar thermal air-conditioning systems compensated for direct cooling by 35.8 % and 30.9 %, respectively, and the corresponding compensations of cooling energy by the storage system were 7.3 % and 11.9 %, respectively. Thus, through this comparative study, we found that the storage system significantly contributed in compensating the cooling demands of the solar thermal system; however, the compensation to direct cooling was lower relative to the solar PV system