A novel current injection model of PWMSC for control and analysis of power system stability

This paper proposes a novel current injection model of Pulse width Modulation based Series Compensator (PWMSC), as new FACTS controller, for damping of low frequency oscillations. The PWMSC operates as a means of continuous control of the degree of series compensation through the variation of the duty cycle of a train of fixed frequency-pulses. The methodology is tested on the sample single machine power system including PWMSC controller by performing computer simulations for small and large distributions. MATLAB/ Simulink software package was used for the simulations

A three‐stage stochastic planning model for enhancing the resilience of distribution systems with microgrid formation strategy

In recent years, severe outages caused by natural disasters such as hurricanes have highlighted the importance of boosting the resilience level of distribution systems. However, due to the uncertain characteristics of natural disasters and loads, there exists a research gap in the selection of optimal planning strategies coupled with provisional microgrid (MG) formation. For this purpose, this study proposes a novel three‐stage stochastic planning model considering the planning step and emergency response step. In the first stage, the decisions on line hardening and Distributed Generation (DG) placement are made with the aim of maximising the distribution system resilience. Then, in the second stage, the line outage uncertainty is imposed via the given scenarios to form the provisional MGs based on a master‐slave control technique. In addition, the non‐anticipativity constraints are presented to guarantee that the MG formation decision is based on the line damage uncertainty. Last, with the realisation of the load demand, the cost of load shedding in each provisional MG is minimised based on a demand‐side management program. The proposed method can consider the step‐by‐step uncertainty realisation that is near to the reality in MG formation strategy. Two standard distribution systems are utilised to validate the correctness and effectiveness of the presented model

A Stochastic Planning Model for Improving Resilience of Distribution System Considering Master-Slave Distributed Generators and Network Reconfiguration

The recent experiences of extreme weather events highlight the significance of boosting the resilience of distribution systems. In this situation, the resilience of distribution systems planning leads to an efficient solution for protecting the system from these events via line hardening and the installation of distributed generators (DGs). For this aim, this study presents a new two-stage stochastic mixed-integer linear programming model (SMILP) to hedge against natural disaster uncertainty. The first stage involves making investment decisions about line hardening and DG installation. Then, in the second stage, the dynamic microgrids are created according to a master-slave concept with the ability of integrating distributed generators to minimize the cost of loss of load in each uncertain outage scenario. In particular, this paper presents an approach to select the line damage scenarios for the SMILP. In addition, the operational strategies such as load control capability, microgrid formation and network reconfiguration are integrated into the distribution system plans for resilience improvement in both planning and emergency response steps. The simulation results for an IEEE 33-bus test system demonstrate the effectiveness of the proposed model in improving disaster-induced the resilience of distribution systems.© 2021 IEEE. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

Dizajn PWMSC regulatora za prigušenje elektromehaničkih oscilacija

Pulse Width modulated based Series Compensator (PWMSC), a newly FACTS device, can modulate the impedance of a transmission line through the variation of the duty cycle of a train of pulses with fixed frequency, resulting in improvement of system performance. In this study, a current injection model of PWMSC is proposed and incorporated in the transmission system model. The purpose of the work reported in this paper is to design an oscillation damping controller for PWMSC to damp low frequency oscillations. We have used the residue method to the linearized equations of the power system for multiple operating conditions and obtained a generalized form which is suitable for different damping controller input-output channels and therefore suitable for different control devices. The case study results show that the proposed controller is very effective to mitigate the power system critical modes of oscillation.Pulsno-širinski modulirani serijski kompenzator (PWMSC), novi FACTS uređaj, modulira impendanciju prijenosne linije putem promjene popunjenosti niza signala s konstantnom frekvencijom, što rezultira poboljšanim svojstvima. U ovome radu predložen je model ubrizgavanja struje u PWMSC-u koji je nadodan u model prijenosa. Cilj ovoga rada bio je dizajnirati oscilatorni regulator prigušenja za PWMSC u svrhu prigušenja niskih frekvencija oscilatora. Korištena je metoda reziduala na linearizirani model energetskog sustava za različite uvjete te je dobivena općenita forma pogodna za ulazno-izlazne kanale regulatora prigušenja pogodna za različite upravljačke ulaze. Analiza pokazuje da je regulator učinkovit kod ublažavanja kritičnih oscilacija energetskog sustava

The Role of V-Domain Ig Suppressor of T Cell Activation (VISTA) in Cancer Therapy: Lessons Learned and the Road Ahead

Immune checkpoints (ICs) have pivotal roles in regulating immune responses. The inhibitory ICs in the tumor microenvironment (TME) have been implicated in the immune evasion of tumoral cells. Therefore, identifying and targeting these inhibitory ICs might be critical for eliminating tumoral cells. V-domain immunoglobulin suppressor of T cell activation (VISTA) is a novel inhibitory IC that is expressed on myeloid cells, lymphoid cells, and tumoral cells; therefore, VISTA can substantially regulate innate and adaptive anti-tumoral immune responses. Besides, growing evidence indicates that VISTA blockade can enhance the sensitivity of tumoral cells to conventional IC-based immunotherapy, e.g., cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors. In this regard, the current study aimed to review the current evidence about the structure and expression pattern of VISTA, its role in TME, the clinicopathological significance of VISTA, and its prognostic values in various cancers. Besides, this review intended to collect the lessons from the recent pre-clinical and clinical studies and propose a strategy to overcome tumor immune-resistance states

Evaluation of Sulfonamide Antibiotic Residues of Honey Samples Produced in Different Regions of Qazvin Province by ELISA

Honey is a unique food product containing bioactive compounds derived from bees and plants Nowadays, animal food products that may contain antibiotic residues have caused a lot of concern for the consumers. The presence of antibiotic residues in honey may be harmful to human health. One of the most important risks of antibiotic residues in food products is the occurrence of drug resistance in pathogenic bacteria in the body. Regarding the complications caused by these residues, the present research has investigated sulfonamide antibiotic residues in the honey samples consumed in Qazvin province. The present research is a cross-sectional study performed in different regions of Qazvin province in 2019. For this purpose, 80 honey samples were collected from different regions of Qazvin. The samples were transferred to the food safety laboratory of the Health Faculty under proper conditions. First, the samples were tested to check the sulfonamide antibiotic residue by the semi-quantitative ELISA assay. The data were recorded in SPSS 23, and data analysis was done by one-way analysis of variance (ANOVA) and (post hoc) Tukey test at the significant level of P˂0.05. According to the results of the ELISA assay, 10-120 ng of sulfonamide antibiotic residue was found in 23.75% (19 samples) of the samples. The findings showed that the highest and the lowest sulfonamide concentrations were respectively reported as 30.81 and 6.26 ppb, and the average sulfonamide residue was obtained as 14.50 ppb. According to the results, more than 75% of the honey samples collected from Qazvin province are free of sulfonamide or contain a little sulfonamide concentration. The research showed that most of the honey samples collected from different regions of Qazvin province are free of sulfonamide or contain a little sulfonamide concentration. Regarding the important role of honey consumption in health and the wide use of antibiotics in beehives, it is necessary to take the necessary actions to control the quality of this product

Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017

A double burden of malnutrition occurs when individuals, household members or communities experience both undernutrition and overweight. Here, we show geospatial estimates of overweight and wasting prevalence among children under 5 years of age in 105 low- and middle-income countries (LMICs) from 2000 to 2017 and aggregate these to policy-relevant administrative units. Wasting decreased overall across LMICs between 2000 and 2017, from 8.4% (62.3 (55.1–70.8) million) to 6.4% (58.3 (47.6–70.7) million), but is predicted to remain above the World Health Organization’s Global Nutrition Target of <5% in over half of LMICs by 2025. Prevalence of overweight increased from 5.2% (30 (22.8–38.5) million) in 2000 to 6.0% (55.5 (44.8–67.9) million) children aged under 5 years in 2017. Areas most affected by double burden of malnutrition were located in Indonesia, Thailand, southeastern China, Botswana, Cameroon and central Nigeria. Our estimates provide a new perspective to researchers, policy makers and public health agencies in their efforts to address this global childhood syndemic