Variations In Solar Insolation Research Articles

A multi-energy inertia-based coordinated voltage and frequency regulation in isolated hybrid power system using PI-TISMC

This paper proposes novel multi-energy inertia support for simultaneous frequency and voltage control of an isolated hybrid power system (IHPS). Multi-energy storage (gas inertia – hydrogen storage, thermal inertia – solar thermal storage, hydro inertia – gravity hydro storage, chemical inertia – battery energy storage) supported by demand side management (DSM) for simultaneous voltage and frequency regulation and backed by biodiesel generators, are the essential elements of IHPS. A novel control strategy of concurrent virtual droop control, virtual damping control, virtual inertia control, and virtual negative inertia control is proposed to utilise multiple inertia sources and to improve LFC and AVR performance effectively. The effective coordination of inertia sources in eradicating oscillations in IHPS, is aided by a developed cascaded proportional integral-tilt-integral-sliding mode (PI-TISMC) controller. The performance of PI-TISMC is compared with PID, PI-PID, and PI-SMC controllers. A maiden attempt has been done by training five diverse classes of optimization techniques to optimize the parameters of controllers in the present work. The results are evaluated in MATLAB and it is evident from the results that the performance of frequency control is improved by 6.5%, 7.8% and 3.4 s (over shoot, undershoot, and settling time). The performance of frequency control is improved by 6.5%, 7.8% and 3.4 s (over shoot, undershoot, and settling time). Similarly, the performance of voltage control is improved by 6.7%, 4.8% and 2.3 s (over shoot, undershoot, and settling time) by employing developed PI-TISMC controller and proposed concurrent inertia control. The combination exhibits superior performance in minimizing oscillations in IHPS due to variations in loading and solar insolation.

Application of an Optimal Fractional-Order Controller for a Standalone (Wind/Photovoltaic) Microgrid Utilizing Hybrid Storage (Battery/Ultracapacitor) System

Nowadays, standalone microgrids that make use of renewable energy sources have gained great interest. They provide a viable solution for rural electrification and decrease the burden on the utility grid. However, because standalone microgrids are nonlinear and time-varying, controlling and managing their energy can be difficult. A fractional-order proportional integral (FOPI) controller was proposed in this study to enhance a standalone microgrid’s energy management and performance. An ultra-capacitor (UC) and a battery, called a hybrid energy storage scheme, were employed as the microgrid’s energy storage system. The microgrid was primarily powered by solar and wind power. To achieve optimal performance, the FOPI’s parameters were ideally generated using the gorilla troop optimization (GTO) technique. The FOPI controller’s performance was contrasted with a conventional PI controller in terms of variations in load power, wind speed, and solar insolation. The microgrid was modeled and simulated using MATLAB/Simulink software R2023a 23.1. The results indicate that, in comparison to the traditional PI controller, the proposed FOPI controller significantly improved the microgrid’s transient performance. The load voltage and frequency were maintained constant against the least amount of disturbance despite variations in wind speed, photovoltaic intensity, and load power. In contrast, the storage battery precisely stores and releases energy to counteract variations in wind and photovoltaic power. The outcomes validate that in the presence of the UC, the microgrid performance is improved. However, the improvement is very close to that gained when using the proposed controller without UC. Hence, the proposed controller can reduce the cost, weight, and space of the system. Moreover, a Hardware-in-the-Loop (HIL) emulator was implemented using a C2000™ microcontroller LaunchPad™ TMS320F28379D kit (Texas Instruments, Dallas, TX, USA) to evaluate the proposed system and validate the simulation results.

On the influence of solar insolation and increase of outdoor temperature on energy savings obtained in heating system with forecast control

Throughout the world there is an ongoing emphasis on the implementation of modern technologies and services to reduce the carbon footprint and increase the energy efficiency of existing and new buildings. Of particular interest are energy-efficient measures that can be easily implemented in existing building stock and at a low cost, such as a forecast controller for heating systems. However, there is a lack of detailed measured data for assessing the influence of varying outdoor conditions on energy savings from a heating system controlled by a forecast controller. The work aimed to assess the influence of variations in solar insolation and outdoor air temperature on the supply temperature, power demand, and heat consumption within thirteen buildings equipped with a forecast control system. The application employs simple correlations, utilizing an equivalent outdoor temperature derived from an online weather prediction application (API) leveraging the data from nearby meteorological stations. The algorithm utilises the weather predictions for changes in outdoor conditions, such as wind speed, temperature, and solar insolation, to optimise the conditions of the heat supplied to buildings.The field research was conducted for one year. It was found that the use of the forecast controller in four public buildings and nine residential buildings reduced heat consumption by an average of 9.0% and 11.8%, respectively, for the case when the variations of the outdoor temperature or the solar insolation were taken into account independently. Higher energy savings (16.5%) were achieved for the case when the outdoor temperature increase as well as solar insolation were taken into account at the same time in the process of forecast control of the heating system.

Performance Improvement of an Electric Vehicle Charging Station Using Brain Emotional Learning-Based Intelligent Control

Electric vehicle (EV) charging facilities are essential to their development and deployment. These days, autonomous microgrids that use renewable energy resources to energize charging stations for electric vehicles alleviate pressure on the public electricity grid. Nevertheless, controlling and managing such charging stations’ energy is difficult due to the nonlinearity and irregular character of renewable energy sources. The current research recommends using a Brain Emotional Learning Intelligent Control (BELBIC) controller to enhance an autonomous EV charging station’s performance and power management. The charging station uses a battery to store energy and is primarily powered by photovoltaic (PV) solar energy. The principles of BELBIC are dependent on emotional cues and sensory inputs, and they are based on an emotion processing system in the brain. Noise and parameter variations do not affect this kind of controller. In this study, the performance of a conventional proportional–integral (PI) controller and the suggested BELBIC controller is evaluated for variations in solar insolation. The various parts of an EV charging station are simulated and modelled by the MATLAB/Simulink framework. The findings show that, in comparison to the conventional PI controller, the suggested BELBIC controller greatly enhances the transient responsiveness of the EV charging station’s performance. The EV keeps charging while the storage battery perfectly saves and keeps steady variations in PV power, even in the face of any PV insolation disturbances. The suggested system’s simulation results are provided and scrutinized to confirm the concept’s suitability. The findings validate the robustness of the suggested BELBIC control versus parameter variations.

Quantification of Holocene temperatures in the eastern Hunshandake Sandy Land using δ13C of loess organic matter

The soil organic carbon isotope indicator (δ13Corg) is widely used in paleoecology and paleoclimate reconstruction due to its ability to record the history of paleovegetation change. Although it has been used as a proxy for precipitation reconstruction, increasing evidence suggests that temperature has played a crucial role in influencing the relative abundance of C3/C4 plants in the mid-latitudes during the interglacial period. This opens up the possibility of reconstructing Holocene temperature using δ13Corg. In this study, the variation of δ13Corg values in a Holocene loess profile (GLH profile), located in the eastern Hunshandake Sandy Land, China, was investigated. And we analyzed the correlation between δ13Corg values and modern temperatures for a total of 792 surface soil samples from mid-latitudes of the Northern Hemisphere, which had thermal conditions comparable to the GLH profile. Strong positive correlations were found between δ13Corg values of surface soil samples and both summer temperatures (r = 0.672, p < 0.001) and growing season temperatures (r = 0.669, p < 0.001). Additionally, δ13Corg values showed significant positive correlations with accumulated temperatures above 10 °C (r = 0.641, p < 0.001) and above 0 °C (r = 0.527, p < 0.001). However, the correlation with mean annual temperature was weak (r = 0.280, p < 0.001). The δ13Corg variation in the GLH profile recorded a mixed C3/C4 vegetation composition, with C4 plants comprising between 23.40% and 1.70% of the total abundance during the Holocene. The combined evidence from modern processes and profile variations confirms that warm-season temperature was the main factor driving variations in the δ13Corg values in the GLH profile. Therefore, we used δ13Corg–temperature conversion equations to quantify Holocene seasonal and accumulated temperatures based on the GLH profile. The reconstructed summer temperatures peaked at 9.3 ka, followed by a fluctuating downward trend during the mid- and late-Holocene, which is consistent with variations in summer solar insolation. Mean summer temperatures were relatively high at 23.3 °C and 22.5 °C in the early and mid-Holocene, respectively, while the lowest mean summer temperature of 20.5 °C occurred in the late Holocene. Accumulated temperatures above 10 °C and above 0 °C in the early Holocene were 3722 °C·d and 4641 °C·d, respectively, similar to modern observations in the Beijing area, indicating a southward shift of the temperature zone by nearly three degrees of latitude since the early Holocene. These reconstruction results are supported by modern observations, TraCE21 simulations, and other studies. This study is significant for extending the application of the δ13Corg indicator for quantitative paleoclimate reconstructions. It verifies its effectiveness in quantifying Holocene temperatures in the marginal zone of the East Asian summer monsoon.

Astronomical Time Scale of the Late Pleistocene in the Northern South China Sea Based on Carbonate Deposition Record

Variations in solar insolation caused by changes in the Earth’s orbit—specifically its eccentricity, obliquity, and precession—can leave discernible marks on the geologic record. Astrochronology leverages these markers to establish a direct connection between chronological measurements and different facets of climate change as recorded in marine sediments. This approach offers a unique window into the Earth’s climate system and the construction of high-resolution, continuous time scales. Our study involves comprehensive bulk carbonate analyses of 390 discrete samples from core SCS1, which was retrieved from the deep-sea floor of the northern South China Sea. By utilizing carbonate stratigraphic data, we have developed a carbonate stratigraphic age model. This was achieved by aligning the carbonate sequence from core SCS1 with the established carbonate standard stratigraphic time scale of the South China Sea. Subsequently, we construct an astronomically tuned time scale based on this age model. Our findings indicate that sediment records in this core have been predominantly influenced by a 20,000-year cycle (precession cycle) throughout the Late Pleistocene. We have developed an astronomical time scale extending back approximately 110,000 years from the present, with a resolution of 280 years, by tuning the carbonate record to the precession curve. Time-domain spectral analysis of the tuned carbonate time series, alongside the consistent comparability of the early Holocene low-carbonate event (11–8 kyr), underscores the reliability of our astronomical time scale. Our age model exposes intricate variations in carbonate deposition, epitomizing a typical “Pacific-type” carbonate cycle. Previous research has illustrated that precession forcing predominantly influences productivity changes in the South China Sea. The pronounced precession-related cycle observed in our record suggests that changes in productivity significantly impact carbonate content in the area under study. Furthermore, the clear precession period identified in the carbonate record of core SCS1 reflects the response of low-latitude processes to orbital parameters, implying that carbonate deposition and preservation in core SCS1 are chiefly influenced by the interplay between the Intertropical Convergence Zone (ITCZ) and the monsoon system within the precession band. Our astronomical time scale is poised to enhance paleoceanographic, paleoclimatic, and correlation studies further. Additionally, the independent evidence we provide for using proxy records for astronomical age calibration of marine sediments lends additional support to similar methods of astronomical tuning.

DSP based Hardware-in-the-Loop (HIL) Simulation for GCPV-based DSTATCOM using Frequency Domain Controller

This study presents a comprehensive simulation of digital control applications for a grid-connected photovoltaic (GCPV) system using a Hardware-in-the-Loop (HIL) simulation approach that incorporates a Digital Signal Processor (DSP). The simulation is carried out using the MATLAB Simulink block set and employs a frequency domain controller as the control algorithm. The simulation inputs, which consist of voltage and current sensor readings, are processed by an ADC idealizer block that produces output based on a real-time DSP-based HIL system. The output is then utilized to generate a pulse width modulation (PWM) signal, which drives the voltage source inverter (VSI). The simulation’s primary objective is to demonstrate the simplicity and efficacy of the proposed frequency domain controller design for the GCPV-based DSTATCOM system. The simulation results validate the performance of the controller under various operating conditions, including steady-state, unbalanced loads, variable solar insolation, and day-to-night transitions.

Observations of Autumnal Cooling in a Large Estuary

AbstractSeasonal variations in solar insolation and wind create an annual water temperature cycle that impacts circulation and biological processes. The waters of Long Island Sound (LIS) warm from March‐February until August‐October and then begin to cool. Ship surveys show that the vertical temperature structure becomes almost uniform during this season when the area experiences low air temperatures and high winds. However, no observations have resolved the temporal evolution of the vertical structure of temperature during these cooling periods because conditions inhibit ship operations. We report glider measurements of the vertical structure of water temperatures and salinities from 22 October to 4 November 2014, in eastern LIS. We find that 20 m of water can cool at approximately during intervals of cold air and strong winds. We use the data to estimate heat content tendencies and infer surface fluxes. We also estimate the surface heat fluxes using buoy‐mounted instruments and show they are consistent. The net heat flux to the atmosphere exceeds 600 W/m2 during the gilder deployment and approximately 66% of this is due to latent heat transfer. Using the buoy fluxes and products of an operation regional model, we show that the agreement with the fluxes derived from heat budget is improved by using local wind observations. In addition to confirming the extremely large cooling rates, our results demonstrate that gliders can be used in a complex region with strong tidal currents to resolve the temperature structure and heat budget during the severe weather of the cooling season.

Quantitative relative humidity reconstruction combining tree-ring with ice core oxygen isotope records

As one of the driest regions in the Asia, the ecological conditions in Northwest China are very fragile. Although relative humidity (RH) plays a vital role in the environment, the lack of long-term RH records hinders the development of reliable scenarios for future extreme environmental conditions in this region. We developed a new method for quantitative regional RH reconstruction; in this method, the signals of precipitation oxygen isotope ratios (δ18O) and temperature in the tree-ring δ18O series are removed to extract the RH signal from the tree-ring δ18O records to the greatest extent. We then combined published millennium tree-ring δ18O, ice core δ18O, and paleo-temperature data to reconstruct a new millennium-long RH record around Delingha, Qinghai, China, on the edge of the northeastern Tibetan Plateau (TP). The reconstructed RH was closely related to both temperature and rainfall, and revealed cycles of approximately 35, 85, 130–160 and 200 years, which are associated with solar insolation variations, Pacific decadal oscillation, and the Atlantic multidecadal variability. With continuous global warming, RH may decrease as the contribution of the temperature increase becomes larger than that of the precipitation over the northeastern TP. This study provides a basis for a new method of RH reconstruction based on different paleoclimate archives.

Precessional pacing of tropical ocean carbon export during the Late Cretaceous

Abstract. The marine biological carbon pump, which exports organic carbon out of the surface ocean, plays an essential role in sequestering carbon from the atmosphere, thus impacting climate and affecting marine ecosystems. Orbital variations in solar insolation modulate these processes, but their influence on the tropical Pacific during the Late Cretaceous is unknown. Here we present a high-resolution composite record of elemental barium from deep-sea sediments as a proxy for organic carbon export out of the surface oceans (i.e., export production) from Shatsky Rise in the tropical Pacific. Variations in export production in the Pacific during the Maastrichtian, from 71.5 to 66 million years ago, were dominated by precession and less so by eccentricity modulation or obliquity, confirming that tropical surface-ocean carbon dynamics were influenced by seasonal insolation in the tropics during this greenhouse period. We suggest that precession paced primary production in the tropical Pacific and recycling in the euphotic zone by changing water column stratification, upwelling intensity, and continental nutrient fluxes. Benthic foraminiferal accumulation rates covaried with export production, providing evidence for bentho-pelagic coupling of the marine biological carbon pump across these high-frequency changes in a cool greenhouse planet.

Holocene environmental change along the central Namib Desert escarpment derived from hyrax and owl dung

Fossil pollen and geochemical sequences from a series of hyrax dung deposits from rock shelters along the eastern margin of the central Namib Desert shed light on the Holocene environmental history of Namibia. Grassy pollen assemblages suggest relatively humid conditions during the early Holocene between ca. 9.6 and 7.7 ka. A series of stepwise changes follows, including the prominence of different pioneer plant communities of which changes in ratios between grassy and shrub pollen types suggests moisture oscillations. The development of more C4 plants around ca. 4.5 ka, as indicated by isotope concentrations and persistent grass pollen percentages, point to the development of a different climatic regime than that in the early Holocene, which extended the area of subtropical savanna towards the south at ca. 24°S. This transition can in part be interpreted as a vegetation response to a shift in the rainfall distribution from an early even seasonal distribution to the current late Holocene summer rainfall regime. Climate changes may have been driven by variations in austral summer and winter solar insolation with changes in total solar irradiance (TSI) superimposed upon them. Through its link to Bond events in the North Atlantic, and thus Atlantic Meridional Overturning Circulation (AMOC), TSI may have affected SSTs in the SE Atlantic and SW Indian Ocean, which influence both summer and winter rainfall in southern Africa.

Mitigation of Cross-Coupling Effects in PV String-Integrated-Converters Employing SEPIC Converter with P&O MPPT Technique

Photovoltaic (PV) string-integrated-converter (S-I-C) topology allows each PV string to operate at their respective maximum power point (MPP) corresponding to the variations in solar insolation. The S-I-C topology comprises an individual DC–DC converter integrated into each PV string. The output terminals of the S-I-Cs are connected either in the series or parallel configuration. There are certain limitations in each of the series/parallel configured PV S-I-Cs. By employing DC–DC boost converter as an S-I-C, cross-coupling effect is the main limitation of a series configured S-I-Cs. The cross-coupling effect causes the deviation in operating points (MPPs) of the shaded & unshaded PV strings and this leads to power consumption by the boost type S-I-Cs instead of delivering to the load. This article presents the mitigation of cross-coupling effects by employing a single-ended primary inductor converter (SEPIC) as an S-I-C in a series configuration of S-I-Cs. The conventional perturb & observe (P&O) MPPT technique is used to track the maximum power from PV strings. The results of the series configuration of SEPIC converter-based S-I-Cs are compared with the boost converter-based series configuration along with the mathematical analysis under uneven-row, uneven-column, diagonal, and long & narrow shading patterns.

Variations in seasonal solar insolation are associated with a history of suicide attempts in bipolar I disorder

BackgroundBipolar disorder is associated with circadian disruption and a high risk of suicidal behavior. In a previous exploratory study of patients with bipolar I disorder, we found that a history of suicide attempts was associated with differences between winter and summer levels of solar insolation. The purpose of this study was to confirm this finding using international data from 42% more collection sites and 25% more countries.MethodsData analyzed were from 71 prior and new collection sites in 40 countries at a wide range of latitudes. The analysis included 4876 patients with bipolar I disorder, 45% more data than previously analyzed. Of the patients, 1496 (30.7%) had a history of suicide attempt. Solar insolation data, the amount of the sun’s electromagnetic energy striking the surface of the earth, was obtained for each onset location (479 locations in 64 countries).ResultsThis analysis confirmed the results of the exploratory study with the same best model and slightly better statistical significance. There was a significant inverse association between a history of suicide attempts and the ratio of mean winter insolation to mean summer insolation (mean winter insolation/mean summer insolation). This ratio is largest near the equator which has little change in solar insolation over the year, and smallest near the poles where the winter insolation is very small compared to the summer insolation. Other variables in the model associated with an increased risk of suicide attempts were a history of alcohol or substance abuse, female gender, and younger birth cohort. The winter/summer insolation ratio was also replaced with the ratio of minimum mean monthly insolation to the maximum mean monthly insolation to accommodate insolation patterns in the tropics, and nearly identical results were found. All estimated coefficients were significant at p < 0.01.ConclusionA large change in solar insolation, both between winter and summer and between the minimum and maximum monthly values, may increase the risk of suicide attempts in bipolar I disorder. With frequent circadian rhythm dysfunction and suicidal behavior in bipolar disorder, greater understanding of the optimal roles of daylight and electric lighting in circadian entrainment is needed.

Implementation of Solar Photovoltaic Grid Interfaced System Using Improved Second Order Generalised Integrator Quadrature (ISOGI-Q) Algorithm

This article deals with a single-stage solar photo voltaic (SPV) array tied toward a three-phase grid by means of an improved second-order generalised integrator quadrature (ISOGI-Q)-based control algorithm to develop the power quality of the grid. The maximum point power tracking (MPPT) is achieved by using a perturb and observe method (P&O). P&O MPPT technique is efficient to extract additional power commencing an SPV array and easy. The SOGI-Q based control serves multi functionalities for example load balancing, power factor correction as well as enhanced solar power penetration addicted to a distribution network. Investigation consequences of the SOGI-Q-based control algorithm are found to be adequate in favour of enhanced power quality in conditions of load balancing, harmonics elimination with very effective power factor correction under different dynamic conditions for instance load unbalancing, variable solar insolation, distorted grid along with imbalanced grid voltage conditions. Distributed static compensator capabilities of a SPV-based system are functional to supply the active power to the load as well as surplus power to the grid.

A Framework of L-HC and AM-MKF for Accurate Harmonic Supportive Control Schemes

In this paper, an enhanced optimal control technique based on adaptive Maximize-M Kalman filter (AM-MKF) is used. To maximize power extraction from solar PV (Photovoltaic) panel, a learning-based hill climbing (L-HC) algorithm is implemented for a grid integrated solar PV system. For the testing, a three-phase system configuration based on 2-stage topology, and the deployed load on a common connection point (CCP) are considered. The L-HC MPPT algorithm is the modified version of HC (Hill Climbing) algorithm, where issues like, oscillation in steady-state condition and, slow response during dynamic change condition are mitigated. The AM-MKF is an advanced version of KF (Kalman Filter), where for optimal estimation in KF, an AM-M (Adaptive Maximize-M) concept is integrated. The key objective of the novel control strategy is to extract maximum power from the solar panel and to meet the demand of the load. After satisfying the load demand, the rest power is transferred to the grid. However, in the nighttime, the system is used for reactive power support, which mode of operation is known as a DSTATCOM (Distribution Static Compensator). The capability of developed control strategies, is proven through testing on a prototype. During experimentation, different adverse grid conditions, unbalanced load situation and variable solar insolation are considered. In these situations, the satisfactory performances of control techniques prove the effectiveness of the developed control strategy.

Optimal planning of hybrid photovoltaic/battery/diesel generator in ship power system

In line with the increasing concern on the pollution release by marine ships, renewable energy technologies in ships power system has received so much attention. Recently, photovoltaic (PV) and energy storage system (ESS) are been integrated into conventional diesel generator in ships power system Nevertheless, improper sizing of the overall ship power station will result in a high investment cost and increase CO&lt;sub&gt;2&lt;/sub&gt; emission. This paper devised a methodology to compute the optimal size of the ESS, PV and diesel generator in a ship power system to minimize CO&lt;sub&gt;2&lt;/sub&gt; emission, fuel cost, and investment cost. It is a well-known fact that power generation in a sailing ship depend on the time zone, local time, date, latitude, and longitude along ship navigation route and the condition of the ship power system also differs from power systems on land. The devised method in this paper takes into accounts the geographical and season variation of solar insolation along the route from Lagos (Nigeria) to Conakry (Guinea) and accurately model the power output of PV modules is along the route.

AFLL-Based Control Technique for Grid Interfaced Three Phase PV System

This work deals with an advanced frequency locked loop (AFLL)-based control algorithm for a three phase double stage grid interfaced solar photovoltaic (PV) system. This AFLL-based algorithm extracts fundamental component of the load current and eliminates harmonics, performs grid currents balancing, improves the system performance during distorted grid conditions, and isolates the system during the occurrence of a grid fault. In a long radial network, the far away ends have the problem of voltage quality but this controller maintains the grid power quality by providing required reactive and active powers to the grid. The voltage source converter (VSC) of the PV system supplies the PV energy to the grid even under the worst situations of dc offset, solar insolation variation, load unbalancing, grid faults, voltage distortion, voltage unbalance, and voltage swell/sag. The VSC switching losses are reduced using an adaptive dc link voltage. This system is modeled and simulated in MATLAB and tests are conducted on a prototype built in the research laboratory under various odd states as stated earlier. Even during the disturbance, the harmonics level in the grid currents is seen in limits as suggested in the IEEE Standard-519.

Steepest Descent Laplacian Regression Based Neural Network Approach for Optimal Operation of Grid Supportive Solar PV Generation

For an optimal operation of a three-phase single-stage grid-tied solar photovoltaic (PV) system, the steepest descent Laplacian regression (SDLR) based adaptive control technique is proposed in this brief. In this topology, the local loads are considered on CPI (Common Point of Interface). Therefore, the objectives of SDLR based control technique, are harmonics mitigation and power quality improvement of the grid currents. Moreover, an additional feature of DSTATCOM (Distribution Static Compensator) is also included in the control scheme. During the night, or when solar PV power generation is zero, then the voltage source converter and capacitor of DC-link are operated as DSTATCOM, which provides reactive power support to the grid. An effectiveness of SDLR based control is validated through experimentation. Here during testing, different types of adverse conditions are considered, such as solar insolation variation, unbalanced load condition, unbalances in grid voltages, etc.

Holocene environmental evolution recorded by multi-proxies from lacustrine sediments of the Hangbu River Valley, Lake Chaohu Basin, East China

在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔），利用AMS¹⁴C测年技术建立可靠的地层年代序列，通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析，高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明，本区域的环境变化过程可以分为4个阶段，阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润，巢湖水位较高，平均粒径、磁化率值较低，TN、TOC、C/N也偏低；阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥，巢湖水量减少，水位降低，平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现，如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比，发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素，并与它们之间复杂的响应机制有关.;Time sequence of the SZK1507 core derived from AMS¹⁴C dating, and the content of the total nitrogen (TN), total organic carbon (TOC) and the C/N values as well as the mean grain size, magnetisability are utilized to reconstruct the environmental changes in the Hangbu River Valley of the Lake Chaohu Basin, East China during the Holocene. The comprehensive analyses of multiple alternative proxies indicated that the evolutionary process of Lake Chaohu Basin in the Holocene could be divided into four periods. The climate was moist in Period Ⅰ ( from 10050 cal. a B.P. to 9700 cal. a B.P.) and Period Ⅲ (from 9250 cal. a B.P. to 5300 cal. a B.P.), and lake level of Lake Chaohu was high inferred from the low values of TN, TOC, C/N, mean grain size and magnetisability. Period Ⅱ (from 9700 cal. a B.P. to 9250 cal. a B.P.) and Period Ⅳ (from 5300 cal. a B.P. to the present) were dry, and the Lake Chaohu had low lake level, suggested by the high values of mean grain size and magnetisability, TN, TOC, C/N. Some global-scale abrupt climatic change events (e.g., 9.3 ka B.P., 8.2 ka B.P., and 4.2 ka B.P. events) were also recorded in this sediment core. Comparing the lacustrine records of SZK1507 core to other observations of climate variability, such as the northern hemisphere summer solar insolation, the sunspot numbers etc during the Holocene, we discovered that the abrupt climatic change events occurring in the Lake Chaohu Basin were affected by the variation of summer solar insolation in the northern hemisphere, the solar activities, the volcanic activities, and the complex feedback mechanism among them principally.

Framework of Gradient Descent Least Squares Regression-Based NN Structure for Power Quality Improvement in PV-Integrated Low-Voltage Weak Grid System

This paper proposes a novel gradient descent least squares regression (GDLSR)-based neural network (NN) structure for the control of grid-integrated solar photovoltaic (PV) system with improved power quality. Here, a single-layer neuron structure is used for the extraction of fundamental component (FC) from the load current. During FC extraction, GDLSR-based NN structure attenuates harmonic components, noise, dc offsets, bias, notches and distortions from the nonlinear current, which improves the power quality under normal as well as under abnormal grid conditions. This single-layer GDLSR-based NN structure has a very simple architecture, which decreases the computational burden and algorithm complexity. Therefore, it is easy in implementation. In this work, the GDLSR-based control technique is tested on a single-phase single-stage grid-integrated PV topology with the nonlinear loads. The prime objective of the GDLSR-based NN structure is to provide reactive power compensation, power factor correction, harmonics filtering and mitigation of other power quality issues. Moreover, when solar irradiation is zero, the dc-link capacitor and voltage-source converter act as a distribution static compensator, which enhances the utilization factor of the system. The proposed system is modeled, and its performances are verified experimentally on a developed prototype in different grid disturbances as well as solar insolation variation conditions, which performances have satisfied the motive of the proposed technique as well as the IEEE-519 standard.