Stand-alone Mode Research Articles

Techno-economic feasibility analysis of optimally sized a biomass/PV/DG hybrid system under different operation modes in the remote area

This paper presents an integrated research framework for the techno-economic feasibility and optimal design of a hybrid energy system for a remote area. A mixed-integer linear programming model is developed for finding optimal solutions to satisfy electricity demand and ensure sustainability. The cost-efficiency and environmental benefits of the hybrid system under the stand-alone and grid-connected operation modes are evaluated and compared. Suifenhe, a remote border area in Northeast China was taken as the case study to verify this model. The results suggest that a grid-connected hybrid system consisting of solar power (28.17 MW), biomass generator (8.71 MW), and battery storage (79.51 MW) is the best economically feasible option to satisfy local electricity demand with the levelized cost of electricity of 0.1498 $/kWh. To achieve 100% electricity self-sufficiency, diesel generators would become the main component satisfying 70% of total demand due to the cost advantage and flexibility. Besides, a 100% renewable energy system is currently not economically feasible due to extremely high costs and considerable electricity supply surplus. Future decreasing PV capital cost and implementing carbon price would facilitate the development of renewable energy and the decarbonization of the power system.

Multimode Features of CIPNLMS-MFX Controlled Single-Phase PV System With Finite State Machine Based Islanding/Synchronization Under Grid Outage

This article presents multimode features of a single-phase photovoltaic (PV) system controlled through a combined improved proportionate-normalized least mean square with modified filtered-X (CIPNLMS-MFX) technique. This system waves off from using the battery storage and successfully operated in standalone mode to achieve the load demand even under the grid outage. The CIPNLMS-MFX based current control technique includes asymmetry parameters and the optimized selection of these parameters provides fast convergence speed, good steady-state response, and improved power quality at nonlinear loads. This PV system is also supported with the synchronization and mode transfer control so that the PV system has autonomous operation under outage and recovery of the grid without disturbing the supply across the domestic loads. A fast detection of a dual cascaded generalized integrator synchronization/islanding structure is presented to evaluate fundamental grid voltage, phase angles, and change in frequency. This structure is robust against the abnormal conditions at the utility grid. The experimental results show that presented CIPNLMS-MFX, DCGI, and finite state machine based logic for islanding/synchronization techniques achieve considerably good performance under various operating scenarios, e.g., outage/ restoration of grid power, varying nonlinear loads, and outage of solar power.

MAF-DCGI Based Single-Phase Uninterrupted PV-Battery System Under Unintentional Islanding

The unintentional islanding is a critical issue in grid-connected solar battery systems in case of grid loss. This interrupts the power supply to the loads. Therefore, in this paper, an uninterrupted photovoltaic (PV)-battery energy storage (BES) system is presented to improve the reliability of the power supply. Besides, this system also furnishes the mitigation of load harmonics current and nonactive power compensation along with peak energy optimization for the PV array. The PV-battery system comprises a battery control by converter and an inverter regulated by an adaptive algorithm. The bidirectional controller regulates the voltage of the DC link capacitor. The moving average filter (MAF) - dual cascaded generalized integrator (DCGI) based adaptive control algorithm is used for utility-interactive operation and a voltage-based control algorithm is used for a standalone mode of operation. MAF-DCGI based phase-locked loop (PLL) is used for synchronization and islanding detection mechanism. An energy management system is used to manage the power flow between the devices in different modes of operation and smooth connection to the grid satisfying the IEEE 1547-2018 standard.

An E-STATCOM Based Solution for Smoothing Photovoltaic and Wind Power Fluctuations In a Microgrid Under Unbalanced Conditions

This manuscript presents a novel control architecture for the E-STATCOM (STATCOM integrated with Energy Storage System (ESS)) that is common for both the Stand-Alone (SA) as well as the Grid-Connected (GC) modes of operation of a microgrid operating under unbalanced conditions. The proposed control architecture fulfils the aim of regulating the E-STATCOM in such a manner so as to smoothen the power fluctuations of a nearby renewable energy source (solar, wind, etc) and also to maintain the voltage and frequency at the Point of Common Coupling (PCC) within the normal range of operation. Hence, the resultant real power injected by the renewable energy source along with the E-STATCOM is constant in magnitude, irrespective of whether the microgrid is in the GC or the SA mode of operation. Dynamically varying limits are introduced to provide inherent VSC over-current protection. In order to illustrate the performance of these control architectures, a model of the IEEE 34 node power distribution network that is being supplied by a solar Photo-Voltaic (PV) Distributed Generation (DG) unit, a wind DG unit and two identical E-STATCOMs (for compensating the power fluctuations from the PV and wind DG units) has been considered for study in PSCAD/EMTDC.

Embedded bleeding detector into a PMMA applicator for electron intraoperative radiotherapy.

The aim of this work is to present a ready to industrialize low-cost and easy-to-install bleeding detector for use in intraoperative electron radiation therapy (IOERT). The detector works in stand-alone mode and is embedded into a translucent polymethylmethacrylate (PMMA) applicator avoiding any contact with the patient, which represent a novelty compared to previous designs. The use of this detector will prevent dose misadministration during irradiation in the event of accumulation of fluids in the applicator. The detector is based on capacitive sensor and wireless power-supply electronics. Both sensor and electronics have been embedded in the applicator, so that any contact with the patient would be avoided. Since access to the tumor can be done through different trajectories, the detector has been calibrated for different tilting angles. The result of the calibration provides us with a fit curve that allows the interpolation of the results at any angle. Comparison of estimated fluid height vs real height gives an error of 1mm for tilting angles less than 10° and 2mm for tilting angles greater than 15°. This accuracy is better than the one required by clinic. The performance of the bleeding detector was evaluated in situ. No interference was observed between the detector and the beam. In addition, a user-friendly mobile application has been developed to help the surgical team making decisions before and during irradiation. The measurement provided by the mobile application was stable during the irradiation process.

A coordinated virtual impedance control scheme for three phase four leg inverters of electric vehicle to grid (V2G)

The three-phase four-leg (3p4L) inverter can be utilized to interface electric vehicles (EVs) with the distribution networks. Vehicle to grid (V2G) inverters are employed to charge EVs from the utility grid as well as compensating harmonics and unbalanced voltages & currents on demand. Motivated by this scenario, this paper proposes a coordinated virtual impedance control scheme for a vehicle to grid three phase four leg (V2G 3p4L) inverter. The proposed control scheme achieves simultaneously multifunctional objectives consisting of effective and good harmonic rejection capability, power sharing among V2G 3p4L inverter units with a smaller error, reactive power/voltage support during load power changes and balanced/unbalanced voltage sag conditions. An independently neutral current control approach is proposed for the fourth leg of the V2G 3p4L inverter to regulate the DC-link along with neutral current control capability. Besides, the proposed control scheme achieves grid connected mode (GCM) or standalone mode (SAM) operation capability as well as fulfilling smooth transition between operation modes without reconstructing control structure. Compared to well-known control schemes in the literature, synchronization during operation modes is also achieved without transients in voltage and current. Comprehensive tests under various scenarios validate the excellence of the proposed control scheme over existing methods.

A High-Gain Non-Isolated Three-Port Converter for Building-Integrated PV Systems

Using a hybrid renewable energy source with an energy storage system, this paper proposed a novel multi-stage non-isolated three-port converter with a 5H inverter to feed a residential load varying from 50 Watts to 3500 Watts. The proposed three-port converter operates in grid-tied and standalone power modes. A novel demand-side management algorithm, which covers eight operation modes, is described. Additionally, a complete control system is discussed. The proposed control system controls the PV maximum power point and battery charging/discharging, and regulates the 400 V DC bus voltage, the load voltage in standalone mode, and the grid-tied injected current. The proposed converter and the control system are validated through simulation for all power modes. The simulation results reveal that the proposed system is viable for Building-Integrated PV Systems.

High-throughput segmentation of unmyelinated axons by deep learning

Axonal characterizations of connectomes in healthy and disease phenotypes are surprisingly incomplete and biased because unmyelinated axons, the most prevalent type of fibers in the nervous system, have largely been ignored as their quantitative assessment quickly becomes unmanageable as the number of axons increases. Herein, we introduce the first prototype of a high-throughput processing pipeline for automated segmentation of unmyelinated fibers. Our team has used transmission electron microscopy images of vagus and pelvic nerves in rats. All unmyelinated axons in these images are individually annotated and used as labeled data to train and validate a deep instance segmentation network. We investigate the effect of different training strategies on the overall segmentation accuracy of the network. We extensively validate the segmentation algorithm as a stand-alone segmentation tool as well as in an expert-in-the-loop hybrid segmentation setting with preliminary, albeit remarkably encouraging results. Our algorithm achieves an instance-level F_1 score of between 0.7 and 0.9 on various test images in the stand-alone mode and reduces expert annotation labor by 80% in the hybrid setting. We hope that this new high-throughput segmentation pipeline will enable quick and accurate characterization of unmyelinated fibers at scale and become instrumental in significantly advancing our understanding of connectomes in both the peripheral and the central nervous systems.

Multi-column modelling of lake Geneva for climate applications

The interaction between large inland water bodies and the atmosphere impacts the evolution of regional weather and climate, which in turn affects the lake dynamics, thermodynamics, ice-formation, and, therefore, ecosystems. Over the last decades, various approaches have been used to model lake thermodynamics and dynamics in standalone mode or coupled to numerical atmospheric models. We assess a turbulence-closure k-epsilon multi-column lake model in standalone mode as a computationally-efficient alternative to a full three-dimensional hydrodynamic model in the case of Lake Geneva. While it struggles to reproduce some short-term features, the multi-column model reasonably reproduces the seasonal mean of the thermal horizontal and vertical structures governing heat and mass exchanges between the lake surface and the lower atmosphere (stratified period, thermocline depth, stability of the water column). As it requires typically two orders of magnitude less computational ressources, it may allow a two-way coupling with a RCM on timescales or spatial resolutions where full 3D lake models are too demanding.

Performance Enhancement of Grid Integrated Photovoltaic System Using Luo Converter

The main aim of this article is to implement a novel active power decoupling-based Luo converter for the weak grid system interfacing photovoltaic (PV) system. The modified Perturb and Observe (P&#x0026;O) algorithm has been used for maximum power extraction from the PV source. The proposed system is capable of operating in the standalone mode and the grid-connected mode. The Luo converter is promising with the viewpoint of low inrush current, high voltage gain, small ripples along with high power density, high efficiency, and simple structure. Hence, the Luo converter has been used for maximum power extraction from the PV source, which is appropriate for both grid-tied and islanding modes of operation. The modified P&#x0026;O algorithm has been used for maximum power extraction. The proposed MPPT technique reduces the drift problem, which occurs in the conventional MPPT methods by including the data of change in current (<inline-formula> <tex-math notation="LaTeX">$\Delta I$</tex-math> </inline-formula>) in addition to the data used in the conventional P&#x0026;O algorithm. This extraction has achieved by using a novel decoupling method, which, in turn, reduces the size of the filter. The converter along with the decoupling method also ensures reduced harmonics at the grid output. The operational principle and the stability analysis of the proposed converter have been analyzed in different modes of operation, such as grid-connected mode and standalone. The simulation has been carried out in MATLAB/Simulink environment. The implementation of the converter is carried out using a microcontroller-based prototype model to validate the performance. The efficiency of the proposed converter has been calculated to be 87.53% when operating under the grid-connected mode, whereas the efficiency is 92.46% when operating under the standalone mode.

An EAFOGI-FLL Based Adaptive Control for Seamless Operation of a Solar Photovoltaic System

This paper presents an enhanced adaptive fourth order generalized integrator with frequency locked loop (EAFOGI-FLL) based control that improves the power quality of a solar photovoltaic system (SPVS) in grid-connected mode (GCM) and standalone mode (SAM), ensures seamless operation, makes the grid currents sinusoidal and, also eliminates DC offset. It ensures unity power factor (UPF) operation of the grid to minimize line losses. The control maintains the point of common coupling (PCC) voltages sinusoidal in GCM and SAM even in the presence of nonlinear loads. The FLL enables effective frequency tracking with grid frequency variations and makes the system adaptive. The SPVS is run in maximum power point tracking (MPPT) mode in GCM and, with an improved control in SAM to ensure power balance. The system is analyzed using a developed simulink model in different conditions.

Unified Control Scheme of Grid-Connected Inverters for Autonomous and Smooth Transfer to Stand-Alone Mode

As one of the approaches for a grid-sustaining inverter, the inverter should cover not only grid-connected (GC) mode but also stand-alone (SA) mode for power supply to local loads; therefore, there are separate control loops for each mode. In order for an uninterruptible power supply to the local load, it should be seamless to change from GC mode to SA mode. This carries two types of issues. One is a transient state caused by switching the control loops. The other is an uncontrolled state during the time interval between a grid failure and its detection, called clearing time. These can lead to unstable voltage for the local load. Hence, a smooth and autonomous mode switching method is required even if the fault detection is late. Existing mode transfer methods considering both the issues have been accompanied by a slow dynamic response, additional sensors, restriction of adopting filter, or controller complexity due to third-order plant. To overcome them, in this article, a control scheme realized by a unified control loop is proposed for smooth and autonomous mode switching with a novel antiderailing control. Furthermore, the proposed control scheme can achieve a high bandwidth for the output power control in GC mode because it is based on controlling the current flowing the inverter-side inductor, and both filter types, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> , can be adopted. To validate the proposed concept, simulations and experiments were conducted. The results show that the proposed control scheme can be used to achieve autonomous and smooth mode transition even under reactive power reference and reactive load conditions.

Research on Optimization of Random Forest Algorithm Based on Spark

As society has developed, increasing amounts of data have been generated by various industries. The random forest algorithm, as a classification algorithm, is widely used because of its superior performance. However, the random forest algorithm uses a simple random sampling feature selection method when generating feature subspaces which cannot distinguish redundant features, thereby affecting its classification accuracy, and resulting in a low data calculation efficiency in the stand-alone mode. In response to the aforementioned problems, related optimization research was conducted with Spark in the present paper. This improved random forest algorithm performs feature extraction according to the calculated feature importance to form a feature subspace. When generating a random forest model, it selects decision trees based on the similarity and classification accuracy of different decision. Experimental results reveal that compared with the original random forest algorithm, the improved algorithm proposed in the present paper exhibited a higher classification accuracy rate and could effectively classify data.

A Comprehensive Review on Off-Grid and Hybrid Charging Systems for Electric Vehicles

In recent years, the research interest in off-grid (standalone mode) and hybrid (capable of both standalone and grid-connected modes) charging systems for electric vehicles (EVs) has increased. The main reason is to provide a seamless charging infrastructure in urban and rural areas where the electrical grid is unreliable or unavailable so that EV adoption can be increased worldwide. In this regard, this article reviews the state-of-the-art architectures of the off-grid and hybrid charging systems and investigates their various subsystems, such as single or multiple energy sources, power electronics converters, energy storage systems, and energy management strategies. These subsystems should be optimally integrated and operated to achieve low-cost and efficient EV charging. Moreover, each subsystem is explored in detail to find the current status and technology trends. Furthermore, EV charging connectors, their power level, and standards for all kinds of EVs (ranging from one-wheeler to four-wheelers) are reviewed, and suggestions are discussed related to the non-standardization of charging plugs. Finally, conclusions show the continuous efforts of the researchers in improving the systems in various aspects, such as cost reduction, performance improvement, longevity, negative environmental effect, system size minimization, and efficient operation, and highlight challenges for both charging systems.

Control of single-phase photovoltaic H6 inverter in grid-connected and stand-alone modes of operation

This paper proposes a control strategy for single-phase transformerless photovoltaic H6 inverter with capability of operation in both grid connected and stand-alone modes. This control strategy enables seamless transition between two modes without any reconfiguration of control structure and need of any external communication. A multi-loop control structure including an inner voltage and current control with PR controller and outer power control with droop controller is utilised to make the inverter operate in both modes. In grid-connected mode, the power control loop regulates reference voltage and frequency for voltage control loop, to adjust power flow of inverter to the main grid while in islanded mode, reference voltage and frequency are determined according to droop characteristic of inverter to supply local load demand. The simulation and experimental result are used to verify the performance of the proposed control.

A short review on landfill leachate treatment technologies

The solid waste disposal problem is a well-known global environmental issue, wherein landfilling and open dumping are the most widely followed practices. The production of toxic liquid, leachate, is a significant issue with landfilling practices. This leachate needs to be treated carefully before its disposal in the environment. Landfill leachate is characterized by very high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) consisting of unappealing constituents like toxic organic and inorganic pollutants. In general, leachate parameters such as landfill age, COD/BOD ratio, and COD are the decisive factors in the selection of appropriate treatment methods. The various adopted technologies for leachate treatment are assessed and summarized under heads like biological, physicochemical, and hybrid methods. The purpose of this research is to look at the technological improvements used for landfill leachate treatment, taking into account the lessons learnt over time and the solutions that have been implemented. It was observed that, when the treatment techniques are employed in standalone mode, they are unable to meet the acceptable water quality criteria, nevertheless when the treatment techniques are used in combination, then it meets the stringent criteria for disposal. The integrated biological and physicochemical treatment methods are viewed as critical for adhering to sustainable release limits and ensuring environmental protection by achieving satisfactory COD, BOD, and ammonia nitrogen removal efficiencies. The evaluation includes state-of-the-art research outputs as well as potential combined applications of various treatment strategies covered in previous works.

Resilience Enhancement at Edge Cloud Systems

It is becoming common practice to push interactive and location-based services from remote datacenters to resource-constrained edge domains. This trend creates new management challenges at the network edge, not least to ensure resilience. These challenges now need to be investigated and overcome. In this paper, we explore the use of open-source programmable asset orchestration at edge cloud systems to guarantee operational resilience and a satisfactory performance level despite system incidents such as faults, congestion, or cyber-attacks. We discuss the design and deployment of a new cross-level configurable solution, Resilient Edge Cloud Systems (RECS). Results from appropriate tests made on RECS highlight the positive effects of deploying novel service and resource management algorithms at both data and control planes of the programmable edge system to mitigate against disruptive events such as control channel issues, service overload, or link congestion. RECS offers the following benefits: i) the switch automatically selects the standalone operation mode after its disconnection from the upper-level controllers; ii) deployment of edge virtualized services is made, according to client requests; iii) the client requests are served by edge services and the related traffic is balanced among the alternative on-demand routing paths to the edge location where each service is available for its clients; iv) the TCP traffic quality is protected from unfair competitiveness of UDP flows; and v) a set of redundant controllers is orchestrated by a top-level multi-thread cluster manager, using a novel management protocol with low overhead.

DRX in NR Unlicensed for B5G Wireless: Modeling and Analysis

The proliferation in the demand of high data rate and improved performance has urged wireless vendors to think of extending 5G New Radio (NR) in unlicensed bands. The unlicensed band is mainly used by Wi-Fi and Wi-Gig resulting in the reduced probability of channel availability. The User Equipment (UE) has to remain active and wait for the availability of unlicensed channel. This process escalates the energy expense of battery-constrained mobile devices. Discontinuous Reception (DRX) introduced in 3GPP can also be used in NR-Unlicensed (NR-U) to reduce UEs energy consumption. This article introduces a DRX mechanism over NR-U networks for both Standalone (SA) and Non-Standalone (NSA) deployment modes. We have used two different flavors, Beam-Search and Beam-Aware, to model DRX mechanism. Hence, the proposed DRX mechanisms are: Standalone DRX with Beam-Search (SBS-DRX), Standalone DRX with Beam-Aware (SBA-DRX), Non-Standalone DRX with Beam-Search (NBS-DRX), and Non-Standalone DRX with Beam-Aware (NBA-DRX). Semi-Markov based modeling is used to show the estimation of power-saving, average delay, and resource utilization. The power-saving achieved with SBA-DRX is 21.13% and 24.84% higher than 5G NR DRX for both Trace 1 and Trace 2, respectively. Moreover, delay achieved with NBA-DRX is 19.16% less than NBS-DRX with 18% less resource utilization.

Control of single-phase photovoltaic H6 inverter in grid-connected and stand-alone modes of operation

Control of single-phase photovoltaic H6 inverter in grid-connected and stand-alone modes of operation

5G Network: Analysis and Compare 5G NSA /5G SA

The fifth generation 5G mobile is the newest global solution wireless standard after 4G. Also, it is a solution that opens the door to new services: Transport, industry..., and help achieve a variety of high-level goals for consumers and businesses. This paper starts by reviewing the evolvement of the mobile generations beginning by 1G until 5G and presenting their characteristics. Secondly, analyzing the implementation of the 5G architecture according to two modes: 5G Standalone Mode (SA) and 5G Non-Standalone (NSA) Mode. Then presenting the options of each mode and deployment scenario of each of these modes. Finally, we draw a conclusion by trying to answer the question that majority of operators are asking, searching for the best implementation of the 5G Network.