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[en] In this paper, we present the FPGA implementation of the multiple pulse width modulation (MPWM) signal generation with repetition of data segments, applied to the variable frequency variable voltage systems and specially at to the photovoltaic water pumping system, in order to generate a signal command very easily between 10 Hz to 60 Hz with a small frequency and reduce the cost of the control system.
[en] Highlights: • The paper presents a novel classification of methods for annual energy harvesting calculation of grid-connected PV systems. • The methods are classified in direct and indirect methods. • Direct methods directly calculate the energy. Indirect methods calculate the energy from the power. • The classification can help the PV professionals in order to choose the most suitable method for each application. - Abstract: Estimating the energy provided by the generators of grid-connected photovoltaic systems is important in order to analyze their economic viability and supervise their operation. The energy harvesting calculation of a photovoltaic generator is not trivial; there are a lot of methods for this calculation. The aim of this paper is to develop a novel classification of methods for annual energy harvesting calculation of a generator of a grid-connected photovoltaic system. The methods are classified in two groups: (1) those that indirectly calculate the energy, i.e. they first calculate the power and from this, they calculate the energy, and (2) those that directly calculate the energy. Furthermore, the indirect methods are grouped in two categories: those that first calculate the I–V curve of the generator and from this, they calculate the power, and those that directly calculate the power. The study has shown that the existing methods differ in simplicity and accuracy, so that the proposed classification is useful in order to choose the most suitable method for each specific application
[en] Highlights: ► To improve the efficiency of PV systems, under different temperature and irradiance conditions. ► The MPPT and different control method for the induction motor were applied. ► The DTC in PV pumping system introduced and performance studied. ► The introductions of DTC in PV systems are very promising. ► Optimizing the water pumping system speed response characteristic by DTC. - Abstract: We aim to find a better control and optimization among the different functions of a solar pumping system. The photovoltaic panel can provide a maximum power only for defined output voltage and current. In addition, the operation to get the maximum power depends on the terminals of load, mostly a non-linear load like induction motor. In this work, we propose an intelligent control method for the maximum power point tracking of a photovoltaic system under variable temperature and irradiance conditions. The system was tested without maximum power point tracking, with the use of Scalar-Based control motor, but we cannot maintain the speed optimal. Next, we developed several methods for the control. Finally, we have chosen the Direct Torque Control.
[en] Due largely to recent dramatic cost reductions, photovoltaics (PVs) are poised to make a significant contribution to electricity supply. In particular, distributed applications of PV on rooftops, brownfields, and other similar applications – hold great technical potential. In order for this potential to be realized, however, PV must be “cost-effective”—that is, it must be sufficiently financially appealing to attract large amounts of investment capital. Electricity costs for most commercial and industrial end-users come in two forms: consumption (kWh) and demand (kW). Although rates vary, for a typical larger commercial or industrial user, demand charges account for about ∼40% of total electricity costs. This paper uses a case study of PV on a large university campus to reveal that even very large PV installations will often provide very small demand reductions. As a result, it will be very difficult for PV to demonstrate cost-effectiveness for large commercial customers, even if PV costs continue to drop. If policymakers would like PV to play a significant role in electricity generation – for economic development, carbon reduction, or other reasons – then rate structures will need significant adjustment, or improved distributed storage technologies will be needed. - Highlights: ► Demand charges typically account for ∼40% of total electricity costs for larger electricity users. ► Distributed photovoltaic (PV) systems provide minimal demand charge reductions. ► As a result, PVs are not a financially viable alternative to centralized electricity. ► Electricity rate structures will need changes for PV to be a major electricity source.
[en] Highlights: • The ionization energies of doped-CZTS with amphoteric impurities have been obtained. • The ionization energies not cross the host bands because of a breathing mode. • It reduces the non-radiative recombination. • The maximum efficiency of these photovoltaic absorber materials has been estimated. -- Abstract: The substitution of Cu, Sn or Zn in the quaternary Cu2ZnSnS4 semiconductor by impurities that introduce intermediate states in the energy bandgap could have important implications either for photovoltaic or spintronic applications. This allows more generation–recombination channels than for the host semiconductor. We explore and discuss this possibility by obtaining the ionization energies from total energy first-principles calculations. The three substitutions of Cu, Sn and Zn by impurities are analyzed. From these results we have found that several impurities have an amphoteric behavior with the donor and acceptor energies in the energy bandgap. In order to analyze the role of the ionization energies in both the radiative and non-radiative processes, the host energy bandgap and the acceptor and the donor energies have been obtained as a function of the inward and outward impurity-S displacements. We carried out the analysis for both the natural and synthetic CZTS. The results show that the ionization energies are similar, whereas the energy band gaps are different
[en] The photorefractive surface waves with photorefractive nonlinearity of diffusion, drift, and photovoltaic effect is studied numerically for the first time. We find out that the essential cause of photorefractive surface waves is diffusion mechanism, but not drift and photovoltaic effects. The photovoltaic effect only has strong influence on the profile of photorefractive surface waves; the applied external electric field can also change the profile of the surface waves, and even destroy the mode upon a threshold, which provides a possible method to transform the modes of surface waves between high-frequency modes and low-frequency modes
[en] The present study aims at numerically investigating the feasibility of an adaptive TMD control system applied on lightweight, flexible structures characterized by time-varying inertial properties. The case study will consist of a photovoltaic support structure subject to snow drifting and slippage in windy conditions.