A review of grid-tied converter topologies used in photovoltaic systems

This study provides review of grid-tied architectures used in photovoltaic power systems, classified by the granularity level at which maximum power point tracking (MPPT) is applied. Grid-tied PV power systems can be divided into two main groups, namely centralized MPPT (CMPPT) and distributed MPPT (DMPPT). The DMPPT systems are further classified according to the levels at which MPPT can be applied, i.e. string, module, submodule, and cell level. Typical topologies for each category are also introduced, explained and analyzed. The classification is intended to help readers understand the latest developments of grid-tied PV power systems and inform research directions

Experimental study of flow in rectangular settling tanks.

Source: Masters Abstracts International, Volume: 40-07, page: . Thesis (M.A.Sc.)--University of Windsor (Canada), 1982

A Hierarchical Control Strategy With Fault Ride-Through Capability for Variable Frequency Transformer

A variable frequency transformer (VFT) is being considered as a new alternative to the classical back-to-back high voltage direct current (HVDC) link for interconnection of two asynchronous networks. The VFT is a retrospective form of frequency converter using the wound rotor induction machine (WRIM), which converts the constant frequency input into a variable frequency output. The prime objective of VFT is to achieve controlled bidirectional power transfer between the two asynchronous networks. This paper presents a detailed working principle of VFT technology and proposes a new hierarchical control strategy for establishing the VFT connection with two power systems to achieve bidirectional power transfer between them. Also, to restrict the grid fault propagation from one side of the VFT to the other side, a series dynamic braking resistor based fault ride-through (FRT) scheme is proposed. The performance of the VFT during the synchronization process, steady-state, dynamic, and the grid fault conditions is evaluated using the real-time hardware in-loop (HIL) system. The plant is simulated in real time using OPAL-RT real-time simulator while the control algorithm is implemented in digital signal processor to carry out HIL study. All the important results supporting the effectiveness of the proposed control strategy and FRT scheme are discussed

Noise-based logic: Binary, multi-valued, or fuzzy, with optional superposition of logic states

A new type of deterministic (non-probabilistic) computer logic system inspired by the stochasticity of brain signals is shown. The distinct values are represented by independent stochastic processes: independent voltage (or current) noises. The orthogonality of these processes provides a natural way to construct binary or multi-valued logic circuitry with arbitrary number N of logic values by using analog circuitry. Moreover, the logic values on a single wire can be made a (weighted) superposition of the N distinct logic values. Fuzzy logic is also naturally represented by a two-component superposition within the binary case (N=2). Error propagation and accumulation are suppressed. Other relevant advantages are reduced energy dissipation and leakage current problems, and robustness against circuit noise and background noises such as 1/f, Johnson, shot and crosstalk noise. Variability problems are also nonexistent because the logic value is an AC signal. A similar logic system can be built with orthogonal sinusoidal signals (different frequency or orthogonal phase) however that has an extra 1/N type slowdown compared to the noise-based logic system with increasing number of N furthermore it is less robust against time delay effects than the noise-based counterpart.Comment: Accepted for publication by Physics Letters A, on December 23, 200

An IoT enabled system for enhanced air quality monitoring and prediction on the edge

Air pollution is a major issue resulting from the excessive use of conventional energy sources in developing countries and worldwide. Particulate Matter less than 2.5 µm in diameter (PM2.5) is the most dangerous air pollutant invading the human respiratory system and causing lung and heart diseases. Therefore, innovative air pollution forecasting methods and systems are required to reduce such risk. To that end, this paper proposes an Internet of Things (IoT) enabled system for monitoring and predicting PM2.5 concentration on both edge devices and the cloud. This system employs a hybrid prediction architecture using several Machine Learning (ML) algorithms hosted by Nonlinear AutoRegression with eXogenous input (NARX). It uses the past 24 h of PM2.5, cumulated wind speed and cumulated rain hours to predict the next hour of PM2.5. This system was tested on a PC to evaluate cloud prediction and a Raspberry Pi to evaluate edge devices’ prediction. Such a system is essential, responding quickly to air pollution in remote areas with low bandwidth or no internet connection. The performance of our system was assessed using Root Mean Square Error (RMSE), Normalized Root Mean Square Error (NRMSE), coefficient of determination (R2), Index of Agreement (IA), and duration in seconds. The obtained results highlighted that NARX/LSTM achieved the highest R2 and IA and the least RMSE and NRMSE, outperforming other previously proposed deep learning hybrid algorithms. In contrast, NARX/XGBRF achieved the best balance between accuracy and speed on the Raspberry Pi

Fiqh of priorities in the light of the purposes of sharee'ah

This research tries to answer the question that reads: What is meant by the Fiqh of Priorities? What is the relationship between it and the other religious basic principles? How can we make benefit of it in confronting our contemporary problems? What is meant by the Fiqh of Priorities and what is its relationship with the other usool (religious basic principles)? Fiqh of Priorities means the most appropriate way of understanding the rulings that are in conformity with the objectives of the religion through achieving the most important and beneficial benefits, warding off the evils or the lesser harm of them, as well as observing the results that may be caused by these rulings. It is a kind of understanding which is followed by the Fiqh of Reality in its different aspects and the Fiqh of Text through knowing its aims and objectives so that the jurisprudence scholars may choose the most appropriate in time and result. Therefore, this kind of Fiqh is related to three other matters that should be understood so that the meaning of the Fiqh of Priorities may be clear for us, the thing that will make us care about it and apply it in the real life of our nation. The first is the objectives of the Sharee‘ah (Revealed laws of Islam). The second is removing difficulty and hardship. The third is elimination of means that may lead to unfavorable results. In this brief research, researchers will touch upon them according to the same earlier mentioned order

The relationship between the purposes of the law and legal reasoning

It is argued that, since qiyas presents a mechanism for the derivation of rulings from the textual sources of the law, in the light of its purposes, the existence of a relation between qiyas and the purposes of the law can be visualized. For, it is in the light of the consideration of the purposes that the rational of a given text is extended to the cases that do not come under its purview. This article therefore, attempts to highlight and analyze the relation between the purposes of the law and qiyas. It also investigates the literal and technical meanings of qiyas and purposes of the law and evaluates their relation in the light of latter providing justification for the former in respect of extension and restriction of legal rulings. The authors, using descriptive and analytical approach, conclude that the purposes of the law by virtue of their potential role in qiyas (legal reasoning) equip the jurist with the ability and insight in how to apply the rulings strictly and when to mitigate them, a fact underscoring the existence of a strong relation between the two

Human rights from an Islamic perspective

A critical overview of human rights from western perspective reveals their deficiencies in conceptualization, flaws in formulation, and injustices in application. This all is due to political agendas, economic pressure and culturally biased viewpoints. They often serve the interests of certain organizations. As such they carry the residues of colonialism and imperialism. This is clear from the ongoing suppression and atrocities inflicted on poor and weak nations without any effective measures being taken by these organizations for their defense and protection. Double standard is applied when it comes to the violation of human rights. Weak states are vigorously pursued whereas, powerful are blatantly exempted from prosecution. Islam as a divine and universal guidance lies a comprehensive framework of values that embodies universal human rights, which is free of bias and deal with the abuser of the human rights equally regardless the race, religion and color factors, hence provides a universal criterion for human rights. Therefore, this paper attempts to analyze the issue of human rights from an Islamic perspective in the light of the purposes of the law, and delineate the mechanism for their protection. Using both descriptive and analytical methods the research concludes that Islam provides a comprehensive and practical mechanism for protection of human rights which is just and of universal application hence is the pioneer of human rights