Multiple PV Research Articles

Grid-connected modular PV-Converter system with shuffled frog leaping algorithm based DMPPT controller

Maximum power extraction for PV systems with multiple panels under partial shading conditions (PSCs) relies on the configuration of the system and the optimal searching algorithms used. This paper described a PV system with multiple PV panels in series. Each panel has a dc-dc step-down converter, hence allowing independent control of load and source power ratio corresponding to the irradiation levels. An H-bridge terminal inverter is also used for grid connection. An advanced searching algorithm (TSPSOEM) is proposed in the paper for the distributed maximum power point tracking (DMPPT). This applies the basic particle swarm optimization (PSO) procedure but with an extended memory and incorporating the grouping concept from shuffled frog leaping algorithm (SFLA). The new algorithm is applied simultaneously to all PV-converter modules in the chain. The system can exploit the variable converter ratios and reduces the effect of differential shading, both between panels and across panels. The paper presents the system and the proposed new algorithm and demonstrating superior results obtained when compared with other conventional methods.

Performance assessment of a three-phase distribution network with multiple residential single-phase PV systems

Performance assessment of a three-phase distribution network with multiple residential single-phase PV systems

Characterizing the spatio-temporal role of sorting nexin 17 in human papillomavirus trafficking.

The human papillomavirus (HPV) L2 capsid protein plays an essential role during the early stages of viral infection. Previous studies have shown that the interaction between HPV L2 and endosomal sorting nexin 17 (SNX17) is conserved across multiple PV types where it plays an essential role in infectious entry, suggesting an evolutionarily conserved pathway of PV trafficking. Here we show that the peak time of interaction between HPV-16 L2 and SNX17 is rather early, at 2 h post-infection. Interestingly, the L2-SNX17 interaction appears to be important for facilitating capsid disassembly and L1 dissociation, suggesting that L2 recruitment of SNX17 occurs prior to capsid disassembly. Furthermore, we also found evidence of L2-SNX17 association at the later stages of infectious entry, suggesting that the SNX17-mediated sorting machinery is either involved at different stages of HPV trafficking or that L2-SNX17 interaction is a long-lasting event in HPV trafficking.

The VPS4 component of the ESCRT machinery plays an essential role in HPV infectious entry and capsid disassembly

Human Papillomavirus (HPV) infection involves multiple steps, from cell attachment, through endocytic trafficking towards the trans-Golgi network, and, ultimately, the entry into the nucleus during mitosis. An essential viral protein in infectious entry is the minor capsid protein L2, which engages different components of the endocytic sorting machinery during this process. The ESCRT machinery is one such component that seems to play an important role in the early stages of infection. Here we have analysed the role of specific ESCRT components in HPV infection, and we find an essential role for VPS4. Loss of VPS4 blocks infection with multiple PV types, suggesting an evolutionarily conserved critical step in infectious entry. Intriguingly, both L1 and L2 can interact with VPS4, and appear to be in complex with VPS4 during the early stages of virus infection. By using cell lines stably expressing a dominant-negative mutant form of VPS4, we also show that loss of VPS4 ATPase activity results in a marked delay in capsid uncoating, resulting in a defect in the endocytic transport of incoming PsVs. These results demonstrate that the ESCRT machinery, and in particular VPS4, plays a critical role in the early stages of PV infection.

An ED paradox: patients who arrive by ambulance and then leave without consulting an ED provider

BackgroundScientists have called for strategies to identify ED patients with unmet needs. We identify the unique profile of ED patients who arrive by ambulance and subsequently leave without consulting a...

Global Maximum Power Point Tracking of Multiple PV Modules under Partially Shaded Condition Using Stepped Comparison Search

For a photovoltaic system consisting of multiple photovoltaic modules under partially shaded conditions, the Power-Voltage (P-V) and Current-Voltage (I-V) characteristics will exhibit multiple local maximum power points. Under this condition it is difficult to track the global maximum power point by using conventional maximum power point tracking techniques. In this article a direct variable step size global maximum power point technique using stepped comparison search has been proposed, which can effectively track the global maximum power point when the multiple photovoltaic modules are under partially shaded conditions. The proposed global maximum power point algorithm consists of a perturb and observe maximum power point tracker, global maximum power point tracking and duty cycle calculation for a DC/DC boost converter, and has been implemented in a single programming module of the microcontroller. The algorithm robustness has been tested under several partial shading conditions through simulation studies. A laboratory experimental model has been used to verify the proposed global maximum power point technique.

Probabilistic analysis of solar photovoltaic self‐consumption using Bayesian network models

In order to assess the systemic value and impacts of multiple PV systems in urban areas, detailed analysis of on-site electricity consumption and of solar PV yield at relatively high temporal resolution is required, together with an understanding of the impacts of stochastic variations in consumption and PV generation. In this study, measured and simulated time series data for consumption and PV generation at 5 and 1 minute resolution for a large number of domestic PV systems are analysed, and a statistical evaluation of self-consumption carried out. The results show a significant variability of annual PV self-consumption across the sample population, with typical median annual self-consumption of 31% and inter-quartile range of 22-44%. 10% of the dwellings exceed a self-consumption of 60% with 10% achieving 14% or less. The results have been used to construct a Bayesian Network model capable of probabilistically analysing self-consumption given consumption and PV generation. This model provides a basis for rapid detailed analysis of the techno-economic characteristics and socio-economic impacts of PV in a range of built environment contexts, from single building to district scales.

Distributed Cooperative ON/OFF Control of Photovoltaic Generation Systems

Abstract: This paper focuses on photovoltaic generation systems where multiple PV generators are connected to each other via communication channels. One of important problems for such systems is to suppress the fluctuation of PV outputs due to weather changes. The existing work proposed an approach which determines whether or not each PV generator supplies electric power, i.e., ON/OFF mode in order to maintain the power supply and demand balance. However, this approach cannot achieve the local generation of electric power for local consumption. Motivated by this, this paper tackles the problem to achieve (i) the power supply and demand balance and (ii) the local generation for local consumption by controlling ON/OFF modes of PV generators. Then, we propose a simple distributed controller as a solution to the problem.

Enhancement of PV Penetration with Centralized Control Method in Cimei Island Distribution System

This paper discusses the use of centralized control method in an Intelligent Energy Management System (iEMS) to prevent voltage violation after load transfer between distribution feeders with high PV penetration level. The proposed method comprises three control modes with different control algorithms for regulating both reactive and active power output of PV inverters in a distribution system with multiple PV installations. Before the execution of load transfer, the total reactive power compensation required at the critical Point of Common Coupling (PCC) is solved by the reactance of distribution feeder line segment to prevent system voltage violation. With the proposed control algorithms, the iEMS dispatches total reactive power compensation among PV systems according to the reactance of line segment and issues the control command to each PV inverter for adjustment of PV power generation so that the ancillary service of voltage support can be provided by all PV systems in a fairer manner. A practical Cimei island distribution feeder pair is selected for computer simulation to verify the effectiveness of the proposed control method after load transfer between two feeders.

Genetic Algorithm Based Network Reconfiguration in Distribution Systems with Multiple DGs for Time Varying Loads

Abstract This paper describes the implementation of an algorithm which predicts optimum reconfiguration plan for power distribution system with multiple PV generators. Since network reconfiguration is a multi objective and multi constrained problem, genetic algorithm is used for optimization. Forward backward load flow method with time varying load condition is considered. The objective function of the genetic algorithm incorporates all the objectives and constraints required for the reconfiguration plan. The algorithm developed predicts the switching pattern for reconfiguration which gives minimum loss and minimum voltage deviation. It also reduces the number of switching operations along with satisfying the defined limit constraints.

The Influence of Distributed Photovoltaic Access to Distribution Network on Voltage Profile

The generated photovoltaic located at load center has a significant impact on feeders' voltage profile. Firstly, considering the reactive power and the line reactance, after theoretical calculation and simulation, it is proved that the influence on voltage profile of generated PV access to distribution network has a great relationship with its access position and access capacity; when there are multiple PV access to distribution network, the influence on voltage profile is different when combined capacity and location is different. Then the maximum alternative capacity at each node is calculated. Al last, it is illustrated through simulation that shunt reactor at PV node and inverter controlling can solve the voltage violation problem.

IMICV fault analysis method with multiple PV grid-connected inverters for distribution systems

A novel faults analysis method with multiple PV grid-connected inverters for distribution systems is proposed. The aforesaid proposed method Inverter Matrix Impedance Current Vector (IMICV) employs symmetrical components combined with a matrix denominated of Inverter Matrix Impedance and with a vector denominated Impedance-Current Vector which are formed by inspection. This matrix and this vector are used to solve a linear system of equations where the following post-fault variables are: current in substation, the voltage at the fault point and voltages in the PV grid-connected nodes. A comparison of results obtained using the new method with the results of the professional software ANAFAS validates the method proposed. Computer simulations show that the proposed method for classical shunt faults analysis is efficient, accurate and easy to program.

Voltage unbalance assessment in secondary radial distribution networks with single-phase photovoltaic systems

• A voltage unbalance sensitivity analysis is presented in a SRDN with SPPVSs. • Current requirements of maximum size to be connected of SPPVSs in SRDNs are checked. • A stochastic assessment method accounts any random combination of SPPVSs in a SRDN. • The assessment of voltage unbalance is made on a 10-min basis throughout one year. • Results present maximum sizes of SPPVS to be connected based on PV penetration. This research describes a way to analyze voltage unbalance sensitivity for different maximum sizes of a single-phase photovoltaic system (SPPVS) with multiple PV penetration levels in a typical secondary radial distribution network (SRDN) in Spain. This analysis effectively assesses current requirements as specified in regulations concerning maximum size to be connected. It thus helps distribution network operators to define optimal limits, depending on their context. A stochastic assessment method is proposed to account for any random combination of SPPVSs in an SRDN. In addition, this method evaluates weekly voltage unbalance during a one-year time period, on the basis of 10-min intervals. More specifically, the voltage unbalance in SRDNs with SPPVSs is assessed for each 10-min interval by means of a probabilistic radial three-phase load flow (RTPLF). The results obtained show the maximum sizes of the SPPVS to be connected as a function of the PV penetration level in the SRDN, where high PV penetrations can produce voltage unbalance problems.

Islanding Detection for Multiple PV Grid-Connected Inverters Based on AFDPF and SMS

Due to the perturbation between multiple PV Grid-connected power system can’t be synchronized easily, the islanding detection often lose efficacy when multiple PV Grid-connected inverters are running simultaneously. The paper show the in-depth analysis of the principle and the advantages and disadvantages of the detection method of AFDPF and SMS, a composition controller is designed aim at the non-detection zone in multiple PV Grid-connected system in the practical application. Through the software simulation, it shows that the method mentioned in the paper practically improves the effect of the islanding detection.

Human papillomavirus infection requires the TSG101 component of the ESCRT machinery

Infection with human papillomaviruses (HPV) requires the minor capsid component L2, which plays an essential role in directing appropriate endosomal trafficking. Previous studies have indicated an infection route involving multi-vesicular bodies (MVBs), and an essential element in their biogenesis is the ESCRT machinery. Here we show that the ESCRT component TSG101 is required for optimal infection with both HPV-16 and BPV-1, with loss of TSG101 resulting in a decrease in viral infection, whereas overexpressed TSG101 increases rates of infection. We find that L2 proteins from multiple PV types interact with TSG101 and show that this interaction contributes to an alteration in the subcellular distribution of L2. In addition, TSG101 can modulate the levels of L2 polyubiquitination. These results demonstrate that TSG101 plays an important part in infection with diverse PVs, and suggests that trafficking of HPV through the ESCRT machinery and MVBs is part of infectious virus entry.

Performance Test Conditions for Direct Temperature Elements of Multiple PV Array Configurations in Malaysia

Solar PV technology and application has been given the highest priority in Malaysia Feed-in-Tariff (FiT) program based on the per kWh electricity rate achieving huge cumulative quota of 18,000 MW. The high enthusiasm and green culture is based on the fact that solar energy source is free, abundance, clean and Malaysia receive approximately 6 hours of sunlight every day the whole year round. This study explores the performance test conditions (PTC) for PV arrays in the tropics based on the direct temperature effect whereby surface temperature (Ts) is implied to the Flat (FF) PV and Tracking Flat (TF) PV array while the concentrating PV (CPV) array implies bottom temperature (Tb) of the Monocrystalline PV module. The field measurement for 10 months results in array efficiency of 3.04% for CPV, 10.04% for FF and the highest conversion efficiency of 10.78% from TF array. Recent studies have proven such significant reduction of 0.5% in energy generation based on 1 0C increase in PV array temperature. Based on this critical value and field validation, contrarily, it is found that an increase of 1 0C of direct temperature element results in 3.3% of array efficiency increase for CPV, 6.7% for TF array and the highest increment of 8.2% for FF array.

An improved active frequency drift anti-islanding method for multiple PV micro-inverter systems

An improved active frequency drift anti-islanding method for multiple PV micro-inverter systems

Calculating electrical and thermal characteristics of multiple PV array configurations installed in the tropics

This study intends to define the electrical characteristics and temperature equations of PV array installed in the tropics based on Sandia National Laboratory (SNL) model. Ten units of 1kW rated PV array namely Fixed Flat (FF), Tracking Flat (TF) and Concentrating (CPV) have been installed at Universiti Putra Malaysia (UPM), Serdang District, Malaysia at the coordinate of 2°59′20′′N:101°43′30′′E with tropical-based ground conditions. Electrical characteristics are the main elements of contributions where five operating conditions for CEEG PV Module are applied based on the SNL model to produce array parameter values. It is found that FF array projects the highest operating value of 12.06A (Isc), 11.55A (Imp), 524.78V (Voc), 89.5V (Vmp), and 1033.7W (Pmp) with good regression fit and strong correlation R2 of more than 0.5. The versatility and accuracy of this work have been validated and applied for three different types of PV array system installed in the equatorial doldrum spot of uniform temperature–irradiance, high in humidity–rainfall and generally light wind field conditions. The parameters are calculated using filtered field data sampled at STC of 5% tolerance. Focal point of calculating array temperature (Tarray) as means of thermal effect on multiple PV array configurations is highlighted based on recent study on Tc equations and Generalized Extreme Value (GEV) analysis using field data at site.

SNX17 Facilitates Infection with Diverse Papillomavirus Types

Previous studies have shown that the human papillomavirus type 16 (HPV-16) L2 capsid protein plays an essential role in viral infection, in part through its interaction with sorting nexin 17 (SNX17). We now show that this interaction between L2 and SNX17 is conserved across multiple PV types. Furthermore, we demonstrate that SNX17 is essential for infection with all PV types analyzed, indicating an evolutionarily highly conserved virus entry mechanism.

Pulmonary vein stenosis detection by early cardiac magnetic resonance imaging post-atrial fibrillation ablation

Summary Identification of early post-atrial ablation MRI characteristics can help predict the development of significant chronic pulmonary stenosis. Background Pulmonary vein stenosis (PVS) is a rare complication of atrial fibrillation (AF) ablation with a rate of significant stenosis, defined as >50%, of 1.3% in a recent multicenter study. As significant morbidity is associated with PVS, detection and surveillance with non-invasive imaging is routine. In this study, we hypothesized that prediction of PVS can be determined with early MRI to identify patients at risk for this complication. Methods A single-center, retrospective, 1:1 cohort to control matched study including patients with (23) and without (23) significant PVS 3 months post-ablation (3moPA) was performed. Study groups were selected from 925 patients who underwent AF ablation and serial MRI scanning. Inclusion criteria for both groups required a full set of three MRI scans: pre-ablation (pre), 24 hours post-ablation (24hrPA), and 3moPA. MRI scanning was performed on a 1.5T or 3T Siemens magnet. Of the 925 patients, 28 were found with significant stenosis on MRA 3moPA. The final PVS study cohort included 23/ 28 patients as 5 were excluded secondary to incomplete MRI scan sets. The control group was comprised of 23 age and sex-matched patients without significant stenosis 3moPA. PV cross-sectional areas were measured at the ostial/proximal portion of the vessels by 3D MRA (Figure 1). In patients with multiple stenotic PV’s, the most stenotic vein was selected for analysis. Results Out of 925 patients, we found 3% (28/925) incidence of significant PVS 3moPA. Of the 23/28 patients in the PVS study cohort, early PV narrowings of >20% on the 24hrPA scan were found in all (23/23, 100%) compared with significantly fewer in the control group (9/23, 39%) (p 20%) on the 24hrPA MRI scan. In addition, small PV caliber on baseline imaging appears to predispose to PVS with the LIPV involved disproportionately. Overall, MRI image characteristics are useful for predicting PVS and may help determine which patients will benefit from surveillance imaging.