Changes In Solar Insolation Research Articles

Interplay of the Indian summer monsoon and intermonsoon precipitation in Sri Lanka due to ITCZ migration during the last 80000 years

Precipitation variations in the tropical Indian Ocean region result from changes in the Indian Summer Monsoon (ISM), as well as convective and cyclonic rainfall. The relative roles of such forcing can be elucidated by constructing robust paleoclimate records, which help to better predict future variability in precipitation due to rising greenhouse gases. This study was carried out using a suite of paleoclimate proxies on a combination of marine and terrestrial sediment cores from Sri Lanka. The sites receive differing amounts of precipitation from the ISM versus convective and cyclone-driven intermonsoon rainfall and allow differentiation of precipitation sources through time. The constructed 80000-year-long precipitation record for the ISM-dominant regions of Sri Lanka shows strong sensitivity to orbital scale insolation variations as well as to millennial-scale events in the North Atlantic region. This precipitation response to external and internal forcings is a result of the combined effects of ISM and Intermonsoon intensity either of which dominated periodically. The strong positive correlation between different periods in the precipitation record and different monthly insolation curves shows that changes in solar insolation due to precession decide the dominant rainfall mechanism in the region, suggesting the ISM dominated after 13 ka (MIS1) while the first intermonsoon dominated between 29 and 13 ka (MIS2) and the second intermonsoon dominated period between 77 and 40 ka.

Impact of Paleogeography on the Stratospheric Polar Vortex in the Geological Past

AbstractThe stratospheric polar vortex (SPV) significantly influences current weather and climate patterns. However, its state in the geological past remains largely unexplored. This study investigates SPV variations in the past 250 million years, using a fully coupled Earth System Model. It is found that midlatitude paleogeography primarily drove substantial SPV variations in the deep time, while changes in CO2 concentrations and solar insolation play a minor role. Both the Arctic and Antarctic SPV were strengthened when the supercontinent Pangea broke up. The increased asymmetry of midlatitude land‐sea contrast tended to weaken the upward propagation of wavenumber‐1 planetary waves, thereby strengthening the SPV. This SPV strengthening correlated with the decelerated stratospheric Brewer‐Dobson circulation and uplift of the polar tropopause. Our results highlight the crucial role of paleogeography in regulating SPV variations and stratosphere–troposphere coupling in deep‐time climate.

Holocene extreme flood events in the middle reaches of the Lancang‒Mekong River basin recorded by a high-altitude lake in southwestern China

The Lancang‒Mekong River (LMR) basin is a region particularly susceptible to floods induced by extreme precipitation. However, owing to limited historical flood records, it is difficult to understand the processes and mechanisms of extreme floods in the LMR basin. In the present study, sediments from a high-altitude lake (Lake Baima, 4700 m above sea level) located in the upper-middle reaches of the LMR are used to reconstruct climate and hydrology variability since the last deglaciation based on a range of climate proxies and methods, including loss-on-ignition, grain size, X-ray diffraction, and X-ray fluorescence. Through the investigation of modern and historical floods in the LMR basin, we combine the climate proxies with hydrological frequency curves to reconstruct the paleoflood sequence during the Holocene. Our results suggest that the temperature and precipitation in southwestern China increased during the Holocene compared to the last deglaciation, indicating a response to changes in Northern Hemisphere summer solar insolation. In addition, Holocene sediments of Lake Baima are primarily composed of brown background layers and numerous light yellow/gray event layers. These event layers are further identified as flood events based on sedimentary facies, redness, and main exogenous elements content and their rate of change. The results show that extreme flood events in the LMR basin occurred more frequently during the early and late Holocene, with seven once-in-1000-year floods during the two intervals; while there were low-frequency flood periods during the mid-Holocene. The occurrence of Holocene floods may be related to external forcing, such as the abrupt changes in total solar irradiance (TSI) and volcanic activity, as well as the internal variability of the wider climate system including the Pacific Decadal Oscillation (PDO) and El Niño‒Southern Oscillation (ENSO). When the TSI was low, the Intertropical Convergence Zone (ITCZ) in the Northern Hemisphere shifted northward, and the Western Pacific Subtropical High (WPSH) moved eastward, accompanied with a negative phase of the PDO and La Niña-like phase of the ENSO. The air-sea interactions increased sea surface temperatures, leading to high precipitation and increasing flood risk in the LMR basin.

A Modified Perturb and Observe Algorithm in Photovoltaic Maximum Power Point Tracking System

Abstract: The power output of the photovoltaic (PV) array is nonlinear, and maximum power point tracking (MPPT) is required to boost the efficiency of solar energy generation. The traditional perturb and observe algorithm is frequently used, but it is difficult to comprehensively consider the tracking accuracy and response speed at the same time. Misjudgment occurs when the solar insolation changes drastically. In view of these shortcomings, this paper presents a variable step size threshold search algorithm. The modified algorithm can quickly track the maximum power point and restrain fluctuations near the maximum power point. Matlab is utilized to simulate and prove the effectiveness of this modified algorithm.

Simultaneous Damping and Frequency Control in AC Microgrid Using Coordinated Control Considering Time Delay and Noise

The incorporation of converter-based generating sources in utility-scale microgrids causes frequency instability and low-frequency oscillations (LFOs), which is also a reason for degeneration in system stability. Damping frequency control is an essential part of alternating current (AC) microgrid system operation and control. Sudden changes in load, variations in renewable power outputs due to changes in solar insolation or wind speed, and so on factors cause the system frequency to deviate from the nominal value. Therefore, the role of a frequency controller is to maintain the dynamic stability in an AC microgrid by retaining the system frequency at the nominal value. Again, AC microgrids with high renewable power penetration face even more difficulty in maintaining frequency stability because of their poor inertial response. The research presented here proposes a novel approach for grid-connected AC microgrid oscillation damping and frequency control that simultaneously takes into consideration time delay and noise. To improve the frequency response and dampen LFOs by providing the voltage and frequency within the specified range, a coordinated technique-based control approach is adopted. In the developed hybrid control, the frequency controller relies on active power modulation, while the power oscillation damping controller is dependent on reactive power modulation. To improve stability and reduce communication consequences such as noise and signal latency (time delay), the developed power oscillation damping controller and frequency controller are coordinated along with the robust linear quadratic Gaussian controller. The comparative investigation of the effectiveness of the coordinated control technique is employed in the software of MATLAB/Simulink for grid-connected AC microgrid. The outcome of the simulation illustrates the superior effectiveness of the suggested controller over the traditional droop controller for huge power flows under disturbance with various operating conditions, under/overfrequency events, time delay, and noise. This grid encouragement capability for AC microgrids is anticipated to lead to novel possibilities for generating revenue.

Optimal Fractional-Order Controller for the Voltage Stability of a DC Microgrid Feeding an Electric Vehicle Charging Station

Charging stations are regarded as the cornerstone of electric vehicle (EV) development and utilization. Electric vehicle charging stations (EVCSs) are now energized via standalone microgrids that utilize renewable energy sources and reduce the stress on the utility grid. However, the control and energy management of EVCSs are challenging tasks because they are nonlinear and time-varying. This study suggests a fractional-order proportional integral (FOPI) controller to improve the performance and energy management of a standalone EVCS microgrid. The microgrid is supplied mainly by photovoltaic (PV) energy and utilizes a battery as an energy storage system (ESS). The FOPI’s settings are best created utilizing the grey wolf optimization (GWO) method to attain the highest performance possible. The grey wolf is run for 100 iterations using 20 wolves. In addition, after 80 iterations for the specified goal function, the GWO algorithm almost discovers the ideal values. For changes in solar insolation, the performance of the proposed FOPI controller is compared with that of a traditional PI controller. The Matlab/Simulink platform models and simulates the EVCS’s microgrid. The results demonstrate that the suggested FOPI controller significantly improves the transient responsiveness of the EVCS performance compared to the standard PI controller. Despite all PV insolation disruptions, the EV battery continues to charge while the ESS battery precisely stores and balances PV energy changes. The results support the suggested FOPI control’s robustness to parameter mismatches. The microgrid’s efficiency fluctuations with the insolation level and state of charge of the EV battery are discussed.

Paleoclimatic reconstruction of northwest Himalaya since CE 475 using lake sediments from Tadag Taal, Kumaun, India

The Kumaun region of India in the northwestern Himalaya experiences complex rainfall patterns, receiving precipitation both during the summer monsoon (June to September) as well as during winter months dominated by westerlies (October to March). In this paper, we present a multi-proxy palaeoclimate record spanning the last ∼1500 years from Tadag Taal, an intermontane lake in Kumaun, India. Our dataset (stable isotope ratios, grain size, trace element ratios) suggests the occurrence of four long-term precipitation cycles of high and low rainfall coinciding with the Dark Ages Cold Period (DACP, ∼475–850 CE), Medieval Climate Anomaly (MCA ∼900–1300 CE), Little Ice Age (LIA, ∼1450–1800 CE) and Current Warm Period (CWP, ∼1850 CE to Present). We infer multi-decadal to centennial-scale shifts in the Indian summer monsoon co-varying with changes in El Niño-Southern Oscillation (ENSO) activity superimposed by changes in solar insolation. To correlate our time-series from the northwestern Himalaya with the Core Monsoon Zone and understand coherency in precipitation between the two regions, we applied the Wavelength Coherency Test. Our data suggest wet conditions during the early phase of the LIA (∼1450–1640 CE) and dry conditions in the later phase of the LIA from ∼1640–1800 CE. The wet conditions in the early LIA were perhaps driven by increased winter precipitation. This is in contrast to Central India that witnessed dry conditions during the entire duration of the LIA. This study thus suggests that monsoon strength was different during earlier and later phase of the LIA. Further, the LIA did not witness uniform climate variability through its duration as has been reported in some European and Chinese proxy records.

Reduced Voltage Sensors Based UPQC Tied Solar PV System Enabling Power Quality Improvement

This work presents an enhanced second-order generalized integrator (ESOGI) based control method for the grid integrated unified power quality conditioner (UPQC) with a solar photovoltaic (PV) system. The objective of this work is to improve the power quality (PQ) indices in the grid by eliminating voltage sensors (grid side) in the overall control. Moreover, presented control method effectively eliminates the DC offset from the input signals and estimates the fundamental element (FE), which is processed to compute the reference signals. The UPQC-PV system comprises two voltage source converters, one connected in a parallel at the point of common coupling for load compensation and the other connected in series via an injecting transformer for voltage compensation. The comparative performance is demonstrated in this work to validate the effectiveness of presented control over state-of-art control algorithms. Moreover, the cost analysis of the presented control is also discussed with the traditional controllers. The UPQC-PV system is simulated in Simulink tool of MATLAB and the performances are analyzed at various dynamic scenarios such as load unbalancing; distorted grid voltages; symmetrical and asymmetrical voltages swell and sag; and change in solar insolation, etc. Experimental results illustrate the superior performance under various operating conditions. The harmonics and magnitudes of load side voltages are restricted as per the IEEE standard 1159. The grid currents and load voltages are well sinusoidal with their total harmonic distortions in the permissible range state in the IEEE standard 519.

Experimental analysis of a solar water heater with a thermosiphone for domestic applications in the south-east of kazakhstan

In this study, a flat solar collector with a thermosyphon was tested in the laboratory of the Institute of Information and Computing Technologies of the Ministry of Education and Science of the Republic of Kazakhstan, located in Almaty (77 degrees east longitude and 43 degrees north latitude). Experimental data were collected over several sunny and cloudy days. The dynamic response of the system to changes in solar insolation is studied and analyzed. It has been found that such systems can provide enough energy to meet the need for hot water, contrary to the erroneous opinion of local residents. The system operates using six sensors (temperature sensor, water flow sensor, pressure sensor, coolant temperature sensor in the heater tank, coolant temperature sensor in the heat exchanger and outdoor temperature sensor). Six sensors are controlled with a programmable logistics integrated circuit (FPGA) STM32 circuit designed to monitor the entire solar system, and the actuators include power relays. The temperature readings are sent to the ESP 32 module. The ESP 32 module is synchronized with six sensors connected to the STM32 FPGA, with six electrical wires programmed in C++, which after processing the temperature, date and time data received from the real-time clock. After the whole process, all sensor data is sent to the ESP 32 module, where data is sent to the database. During the experiment an electric energy consumption savings of about 1% was achieved due to the control signal in the controller which had a significant impact on the service time of the equipment.

The impact of Holocene deglaciation and glacial dynamics on the landscapes and geomorphology of Potter Peninsula, King George Island (Isla 25 Mayo), NW Antarctic Peninsula

The timing and impact of deglaciation and Holocene readvances on the terrestrial continental margins of the Antarctic Peninsula (AP) have been well-studied but are still debated. Potter Peninsula on King George Island (KGI) (Isla 25 de Mayo), South Shetland Islands (SSI), NW Antarctic Peninsula, has a detailed assemblage of glacial landforms and stratigraphic exposures for constraining deglacial landscape development and glacier readvances. We undertook new morphostratigraphic mapping of the deglaciated foreland of the Warszawa Icefield, an outlet of the Bellingshausen (Collins) Ice Cap on Potter Peninsula, using satellite imagery and new lithofacies recognition and interpretations, combined with new chronostratigraphic analysis of stratigraphic sections, lake sediments, and moraine deposits. Results show that the deglaciation on Potter Peninsula began before c. 8.2 ka. Around c. 7.0 ka, the Warszawa Icefield and the marine-facing Fourcade Glacier readvanced across Potter Peninsula and to the outer part of Potter Cove. Evidence of further readvances on Potter Peninsula was absent until the Warszawa Icefield margin was landward of its present position on three occasions: c. 1.7–1.4 ka, after c. 0.7 ka (most likely c. 0.5–0.1 ka), and by 1956 CE. The timing of Holocene deglaciation and glacier fluctuations on Potter Peninsula are broadly coeval with other glacier- and ice-free areas on the SSI and the northern AP and likely driven by interactions between millennial–centennial-scale changes in solar insolation and irradiance, the southern westerlies, and the Southern Annular Mode.

Self-reliant solar PV based microgrid with seamless transition capabilities at weak grid conditions

• The extended proportional complex filter (EPCF) control allows a fast estimation of the quadrature and in-phase fundamental load current components with reduced harmonics within the prescribed limit. • The EPCF-based control has extracted the fundamental component of load current with high rate of convergence and better system response. The variations on load, utility, and solar array radiation are well established in simulation and test results. The PQ is enhanced at unbalancing of load, change in solar insolation and grid adverse conditions of voltages unbalances. The performance of the system is found satisfactory and its response is enhanced at adverse grid conditions. Experimental results have demonstrated that the THD are as recommended by the IEEE-519 standard even during weak grid conditions. • A comparative analysis is included, which validates the superior filtering capability and improved power quality during weak grid conditions. In addition a tabular comparative analysis is included to support its effectiveness while addressing abnormalities of the grid. • The EPCF-PLL grid synchronization and phase angle estimator scheme has provides fast mode transition, frequency tracking and uninterrupted supply to the load during non availability of the grid. This has given precise phase angle estimation. Conventional PLL controllers are non-adaptive towards large frequency. EPCF-PLL has provided effective frequency adaptability. This makes the synchronization process immune from frequency variation and voltage unbalance. • The proportional resonant controller with harmonic compensation (PRHC) controller provides satisfactory performance under all the intermittent conditions overcoming the tradeoff between improved steady-state and transient performance. This paper presents a solar photovoltaic (PV) based energy conversion system with seamless transfer to the grid. To provide satisfactory performance in grid connected mode, a control based on extended proportional complex filter (EPCF) is used. The EPCF is used to estimate the fundamental current component (LCFC) of local loads At the linkage point (LP), the power quality (maintaining IEEE-519 standard) is improved using this control. The EPCF maintains balanced grid currents whether PV array generation is available or not. It provides effective mitigation of harmonics and monitors the flow of active power, which improves the grid current quality.This control provides versatile actions such as extraction of LCFC, harmonics elimination, DC offset removal, robust performance during voltages unbalance etc. The same control technique (EPCF) along with phase locked loop is used for smooth synchronization; it reduces the use of another algorithm, which improves the dynamic response of the system. This control estimates exact phase and frequency variation for the seamless mode switching. It provides frequency adaptation during mode shifting. The comparative results validate that the control based on EPCF has a faster detection of grid in comparison with existing controls. During the grid-outage, the proportional resonant (PR) controller with harmonics compensation (HC) based control algorithm enhances performance of the microgrid. This provides successful solution for harmonics compensation and minimizing steady state errors. Simulated and experimental results, in various scenarios, have verified the effectiveness of the controllers and demonstrate the favourable solution in controlling the unfavorable grid conditions.

Late Miocene reorganization of lake hydrological systems on the northern Tibetan Plateau linked to topographic growth

The hydrological cycles of lakes on the Tibetan Plateau (TP) have had profound impacts on the climatic and environmental evolution of the Asian interior and hence they are crucial for the well-being of the large human population of this region. The late Miocene is regarded as the most recent interval when the TP was extensively occupied by large paleolakes. However, it is unclear when and how these mega paleolakes shrank and the environment evolved into its present domination by desert and semi-desert. To address these issues, we conducted detailed analyses of diffuse reflectance spectroscopy, sedimentology, paleomagnetic-based tectonic rotation, and biogeochemistry of a Middle to Late Miocene sedimentary sequence in the Xining Basin in the North-eastern (NE) TP, supplemented by a spatiotemporal comparison of our results with equivalent records from adjacent regions. The results reveal a clear transition of the lacustrine system in the Xining Basin at ∼ 11 Ma, characterized by decreased water level and an increase in the oxidation state of the depositional environment. Combined with a summary of sedimentary evidence from seven different basins in the NE TP, we propose that a fundamental reorganization of lake hydrological systems occurred in the NE TP at ∼ 11 Ma. This reorganization was synchronous with tectonic deformation and topographic growth in the NE TP, as revealed by our new tectonomagnetic and other available tectonic evidence. Therefore, tectonic activity—rather than changes in climate or solar insolation, as previously proposed—was the principal factor responsible. This hydrological reorganization was of profound significance for the regional hydrological cycle and the climatic and ecological environment of Asia, because the elevated topography prevented the NE TP from regaining its Middle Miocene paleohydrological configuration.

Control of Solar PV Arrays Based Microgrid Intertied to a 3-Phase 4-Wire Distribution Network

This article presents a multiple solar photovoltaic (PV) array based microgrid (MG) integrated into a 3-phase 4-wire distribution network. The main voltage source converter (VSC) and ancillary VSC's dc links are assimilated to PV arrays with maximum power point tracking. The main VSC operates with current control in a grid interfaced mode. However, at grid interruption, voltage control is utilized in an autonomous mode as a grid forming inverter, which sustains frequency and voltage across point of common coupling (PCC) for continuous power to loads. The ancillary VSC operates in current control. The feed-forward powers of PV arrays in VSCs current control improve MG dynamic behavior. MG's satisfactory behavior is achieved for changes in solar insolation and load, load unbalances, and neutral current compensation in MATLAB, and is authenticated in hardware in loop via a real-time controller, i.e., OPAL-RT (OP4510) with RT-LAB environment. The MG has the capability to sustain islanding and its mode transitions operation is seamless. The grid current total harmonics distortion (THD) and autonomous mode's PCC voltages THD are found to adhere to standard IEEE-519-2014.

Association between polarity of first episode and solar insolation in bipolar I disorder

ObjectiveCircadian rhythm disruption is commonly observed in bipolar disorder (BD). Daylight is the most powerful signal to entrain the human circadian clock system. This exploratory study investigated if solar insolation at the onset location was associated with the polarity of the first episode of BD I. Solar insolation is the amount of electromagnetic energy from the Sun striking a surface area of the Earth. MethodsData from 7488 patients with BD I were collected at 75 sites in 42 countries. The first episode occurred at 591 onset locations in 67 countries at a wide range of latitudes in both hemispheres. Solar insolation values were obtained for every onset location, and the ratio of the minimum mean monthly insolation to the maximum mean monthly insolation was calculated. This ratio is largest near the equator (with little change in solar insolation over the year), and smallest near the poles (where winter insolation is very small compared to summer insolation). This ratio also applies to tropical locations which may have a cloudy wet and clear dry season, rather than winter and summer. ResultsThe larger the change in solar insolation throughout the year (smaller the ratio between the minimum monthly and maximum monthly values), the greater the likelihood the first episode polarity was depression. Other associated variables were being female and increasing percentage of gross domestic product spent on country health expenditures. (All coefficients: P ≤ 0.001). ConclusionIncreased awareness and research into circadian dysfunction throughout the course of BD is warranted.

Improved perturb and observe maximum power point tracking technique for solar photovoltaic power generation systems

The primary concerns in the practical photovoltaic (PV) system are the power reduction due to the change in operating conditions, such as the temperature or irradiance, the high computation burden due to the modern maximum power point tracking (MPPT) mechanisms, and to maximize the PV array output during the rapid change in weather conditions. The conventional perturb and observe (P&O) technique is preferred in most of the PV systems. Nevertheless, it undergoes false tracking of maximum power point (MPP) during the rapid change in solar insolation due to the wrong decision in the duty cycle. To avoid the computational burden and drift effect, this article presents a simple and enhanced P&O MPPT technique. The proposed technique is enhanced by including the change in current (dI), in addition to the changes in output voltage and output power of the PV module. The effect of including the dI profile with the traditional method is explained with the fixed and variable step-size methods. The mathematical expression for the drift-free condition is derived. The traditional boost converter is considered for validating the effectiveness of the proposed methods by employing the direct duty cycle technique.

Golden Eagle Optimized Control for a Dual Stage Photovoltaic Residential System with Electric Vehicle Charging Capability

ABSTRACT In this article, the control of a grid-connected, single-phase, dual-stage photovoltaic (PV) residential system with electric vehicle (EV)-charging capability is being presented. A residential system faces a lot of dynamic conditions such as changing atmospheric condition or random patterns of load connection or disconnection as well as power failure. In this regard, this article proposes the optimization of proportional and integral gains selection of the bidirectional DC/DC converter (BDC) PI controller through golden eagle optimization (GEO) algorithm to improve the system performance. The system is subjected to various induced dynamic conditions simulated in MATLAB Simulink environment and the performance is compared with particle swarm optimization, genetic algorithm, and gains obtained through hit and trial. In comparison with other techniques, GEO algorithm provides optimum BDC PI gains, as a result, the DC-link voltage achieves 1.5 times shorter settling time. During the non-linear load changes and voltage swell condition, the settling time is 2 times shorter. Settling time of the EV battery power shows 1.7 times reduction. The transient response of the PV power also shows dramatic improvement with 3 times faster settling time during solar insolation changes. During the sudden non-linear load changes, the momentary transients die 1.5 times faster. Moreover, a seamless control is developed to achieve a seamless transition from islanded mode to grid connected mode and vice versa. The proposed system achieves unity power factor and complies with the IEEE -519 power quality standard.

Small scale wind & solar photovoltaic energy conversion system for DC microgrid applications

The rise in demand for electrical energy throughout the globe gives a significant rise in new power generating sources. The Wind and Solar Photovoltaic energy sources are the most propitious power generating sources among them. Nowadays, these sources play an important role to form a Micro Grid with the incorporation of conventional grid and energy storage facilities. This article comprises of the simulations analysis for Wind Energy Conversion System and Photovoltaic Energy System incorporated with DC load for the applications of DC Microgrid. The mathematical model of the WECS and PVES are incorporated and proposed with the Gain Scheduled Proportional Integral controller is proposed in the paper. The WECS and PVES are simulated with interfacing units for the DC load. The results are obtained for Ahmedabad, Gujarat, India for the input solar insolation and wind speed data. The materials used in small wind energy conversion systems and photovoltaic energy systems are discussed for microgrid applications. The performance for the WECS and PVES is analyzed for change in wind speed and change in solar insolation. The incorporation of GSPI controller provides stable results to maintain the voltage regulation. The results are stable over an extensive range under the unpredictable atmospheric conditions the dynamic scheduling is proposed.

Power Quality Improvement in SyRG-PV-BES-Based Standalone Microgrid Using ESOGI-FLL-WIF Control Algorithm

In this article, a resilient enhanced second-order generalized integrator with frequency locked loop and inner loop filter (ESOGI-FLL-WIF) control algorithm is implemented to enhance the power quality and to regulate the voltage/frequency of a microgrid. This control has a simple structure, fast convergence, and excellent dynamic and steady-state response. The ESOGI-FLL-WIF control algorithm is used for assessing the fundamental constituent from harmonics and dc bias infected current. ESOGI-FLL-WIF control strategy tracks the frequency and tunes to the frequency fluctuations in transient situations. To have a fair comparison, the performance of the ESOGI-FLL-WIF control algorithm is compared with already existing controls. This three-phase four-wire islanded system consists of a solar photovoltaic array and pico-hydro turbine-driven synchronous reluctance generator (SyRG). As an alternative to the conventional generators, SyRG is used because it is economical (no permanent magnets in the rotor) and has high efficiency (no electrical losses in the rotor). The four-leg converter compensates neutral current and controls the reactive power injection under unbalance load condition, whereas for active power management, battery energy storage is incorporated in the system. A prototype of the system is developed and tested under different situations of load unbalancing and solar insolation change to confirm the effectiveness and viability of the control strategy.

Abrupt Indian summer monsoon shifts aligned with Heinrich events and D-O cycles since MIS 3

The tropics experienced a unique monsoon climate that drove important changes in socio-economic conditions and shaped different phases of human history during the late Quaternary across the Indian subcontinent. This study presents a new high-resolution speleothem-record of Indian summer monsoon (ISM) variability ranging from ~45,000 to 34,000 yr BP combined with a published record up to 5500 yr BP from the Mawmluh cave, northeastern India. We document significant changes in solar insolation and precession harmonics, implicating solar activity as one of the major forcing factors for rapid monsoonal shifts. Our new δ 18 O time series shows high-amplitude shifts in the ISM during the marine isotope stage 3 (MIS 3), similar to Dansgaard-Oeschger (D-O) oscillations recorded at high northern latitudes, which mimic the Greenland ice sheet record. The sun driven Northern Hemisphere high latitude climate anomalies played an active role in driving ISM variability and changes in the regional hydrological cycle on centennial to millennial time scales across the Indian subcontinent. • Longest isotope record of speleothem from the South Asian region • Saw-tooth like isotope variability during MIS 3 • Changes in the NH temperatures impacted the hydroclimatic conditions in the Indian subcontinent. • Source region and transport pathways controlled the speleothem isotopic composition.

Dual mode control to improve power quality of 3‐phase 4‐wire grid interfaced PV‐battery system

This paper presents the dual-mode control to improve the power quality (PQ) of three-phase four-wire grid interfaced photovoltaic (PV) battery system in a single-stage configuration, where the current control is used at normal circumstances for the grid-interactive mode and for the grid interruption, the system operation is through the voltage control. The transient free switching between grid interactive and off-grid modes is executed by a power electronics switch, thus at disconnection, the system gives reliable and incessant power to the loads. The weight of the active current constituent from the load current is acquired using Mathew's algorithm-based adaptive filter. The voltage control regulates the frequency and voltage across the loads in off-grid mode. The current control used for a voltage source converter mends the PQ namely current harmonics extenuations and unity power factor operation and it utilizes the solar PV's array power feed-forward unit for the enhancement of the system's dynamic performance. The incremental conductance technique is applied for obtaining the maximum PV array's power. The addition of a battery across the DC link is realised using a DC–DC buck-boost converter. The battery is discharged and charged in accord with the load's variation. This converter's control sustains the maximum power point tracking voltage. The system's performances for the steady-state and dynamic situations, such as solar insolation change, load perturbation, load unbalancing and neutral current compensation, are authenticated on a developed prototype through test results.