An Investigation of the Influences of the Voltage Sag on the Doubly Fed Induction Generator using Tuned PI Controllers

The paper presents dynamic and transient behavior of the doubly fed induction generator (DFIG) in the wind farms in the normal and faulted grid respectively. When Voltage sag or any fault occurs in the network, the variables in the Doubly Fed Induction Generators are varying severely. If a voltage sag occurs, active and reactive power generated by the DFIG start to oscillate. The DC-link voltage will be bigger and will have fluctuation, and the rotor current will increase. In this paper, proportional integral (PI) controllers are used to control the DFIG in the wind farms for driving of the electronic devices including Rotor Side Converter (RSC) and Grid Side Converter (GSC) and controlling the active and reactive power of DFIG. PI parameters are tuned by particle swarm optimization algorithm (PSO). Whereas the model of DFIGs and electronic device in the paper are nonlinear so PI controllers cannot protect and control the DFIG as well. Hence, effect of PI parameters is investigated on the DFIG with simulating in MATLAB software. Also, low voltage ride through (LVRT) feature for DFIG is explored in presence of PI controllers. The results of the simulation present DC-link over voltage and rotor and stator over current in the DFIG. In addition, it will explore the effect of proportional integral controllers when three-phase short circuit fault occurs

Provision of frequency stability of an islanded microgrid using a novel virtual inertia control and a fractional order cascade controller

Nowadays, the renewable energy sources in microgrids (MGs) have high participation to supply the consumer’s demand. In such MGs, the problems such as the system frequency stability, inertia, and damping reduction are threatened. To overcome this challenge, employing the virtual inertia control (VIC) concept in the MG structure could be considered as a viable solution to improve the system frequency response. Hence, this work proposes a novel modeling for VIC in an islanded MG that provides simultaneous emulation of the primary frequency control, virtual inertia, and damping. To show the efficiency of the proposed technique, a comparison is made between the dynamic performance of the proposed VIC and conventional VIC under different scenarios. The results indicate that the proposed VIC presents superior frequency performance in comparison with conventional VIC. In addition to VIC modeling, a new cascade controller based on three-degrees of freedom and fractional-order controllers (FOCs) is proposed as an MG secondary controller. The effectiveness of the proposed controller is compared to tilt-integral-derivative and FO proportional-integral-derivative controllers. The Squirrel search algorithm is utilized to obtain the optimal coefficients of the controllers. The results demonstrate that the proposed controller improves the MG frequency performance over other controllers. Eventually, the sensitivity analysis is performed to investigate the robustness of the proposed controller in the face of the variations of the parameters

An Efficient Rapid Method for Generators Coherency Identification in Large Power Systems

With steadily increasing interest in enhancing large power systems’ transient stability, generator coherency identification has become critical for the dynamic equivalents, controlled-islanding, and wide-area control of these systems. This paper presents an approach based on two classical and powerful techniques. The proposed method comprises the slow coherency method followed by the time-domain-based simulation of transient stability to identify the coherent groups of generators. In this regard, various operating conditions of the system are considered to obtain the updated coherency information between groups of generators by analyzing the chosen generator rotor angle. The proposed approach’s merits are tested on the New England IEEE 39-Bus and modified IEEE 118-Bus test systems in the PowerFactory software tools through Python. Corresponding simulation results validate the proposed paradigm’s effectiveness by enhancing the transient stability speed of a large power system without decreasing its coherency behavior accuracy. It is also observed that the proposed scheme tends to be more consistent in determining the coherent groups of generators in the presence of disturbances and different operational conditions.© 2022 the Authors. Published by 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

Primary ciliary dyskinesia in six patients with bronchiectasis

INTRODUCTION: Primary ciliary dyskinesia [PCD] is generally considered as a rare autosomal recessive disorder. Previous studies reported various prevalence of PCD among patients with bronchiectasis. MATERIAL AND METHODS: Six PCD patients who were diagnosed during the investigation of 40 patients with bronchiectasis were enrolled in this study. Ultra structural studies for both epithelium and cilia were performed, and the deformities in detailed electron microscopic images confirmed the diagnosis of PCD. RESULTS: Four patients experienced the first symptoms shortly after the birth, 1 by the age of 1 and 1 by the age of 4 years. Except of 1 case that was diagnosed 2 months after the onset of disease, diagnosis delay was longer than 5 years in all patients. Consanguineous marriage was observed in the parents of all patients. Upper respiratory tract infections were documented for all patients. CONCLUSIONS: PCD should be considered as a probable underlying disorder in patients with bronchiectasis. Past medical history of otitis media and history of similar clinical findings in family members should raise suspicion toward PCD.INTRODUCTION: Primary ciliary dyskinesia [PCD] is generally considered as a rare autosomal recessive disorder. Previous studies reported various prevalence of PCD among patients with bronchiectasis. MATERIAL AND METHODS: Six PCD patients who were diagnosed during the investigation of 40 patients with bronchiectasis were enrolled in this study. Ultra structural studies for both epithelium and cilia were performed, and the deformities in detailed electron microscopic images confirmed the diagnosis of PCD. RESULTS: Four patients experienced the first symptoms shortly after the birth, 1 by the age of 1 and 1 by the age of 4 years. Except of 1 case that was diagnosed 2 months after the onset of disease, diagnosis delay was longer than 5 years in all patients. Consanguineous marriage was observed in the parents of all patients. Upper respiratory tract infections were documented for all patients. CONCLUSIONS: PCD should be considered as a probable underlying disorder in patients with bronchiectasis. Past medical history of otitis media and history of similar clinical findings in family members should raise suspicion toward PCD

Effects of Preemptive and Preventive intravenous Paracetamol on postoperative pain and opioid consumption in patients undergoing laparoscopic nephrectomy

Background: Adequate pain control is a goal in post operative recovery. However opioids provide good analgesic effects, their side effects such as postoperative nausea and vomiting (PONV) limit their administration. Intravenous Paracetamol as a safe and well tolerated drug with lower side effects can be used instead of opioids for pain management.Objectives: The aim of this study is to compare preemptive or preventive administration of paracetamol with placebo group to investigate its effects on pain control and opioid consumption in patients undergoing laparoscopic nephrectomy.Patients and Methods: Ninety patients were randomly divided to three groups. Preemptive group received 1 gr paracetamol in 100 ml normal saline 30 minutes before induction of anesthesia, Preventive group received 1 gr paracetamol in 100 ml normal saline before closure of the skin and placebo group just received 100 ml normal saline. Post surgical pain was assessed using Verbal Rating Scale (VRS). Pethidine 0.25 mg/kg was administered and repeated each 10 minutes to control pain. Pain scores, total dose of opioid and symptoms like nausea and vomiting were recorded. Results: Preemptive and Preventive groups had lower pain scores than placebo group. Opioid consumption and PONV were significantly higher in placebo group. No significant differences were observed between Preemptive and Preventive groups.Conclusion: IV Paracetamol can provide an adequate pain control with low side effects and may be an effective choice in management of post operative pain in patients undergoing laparoscopic nephrectom

Costs of hospital admission on primary immunodeficiency diseases

Background Primary immunodeficiency diseases (PID) are heterogeneous group of inherited disorders mainly characterized by recurrent infections leading to several times hospital admissions. The economic impact of PID is a challenging issue; therefore, this study was designed to determine the medical costs of hospitalizations in this group of patients as an indicator of the direct cost of these diseases. Methods One hundred and ten children with PID hospitalized in the Children’s Medical Center Hospital, Tehran, Iran were included in this study during Jan 2011 and Jan 2012. All direct costs during the admission period were calculated, using the hospital information system. Results Medical cost was $7.090 per patient per admission. Among them, about 1.580$ belong to drug consuming during hospitalization. Anti-infective drugs for systemic use were the most cost-consuming group of drugs, followed by alimentary tract and metabolism and blood and blood forming organs agents. Investigation of anti-infective group internally showed that immune sera and immunoglobulin and antiviral agents for systemic use consisting the most important medication for PID patients during hospital admission. Conclusion Although the results of economic evaluations in a region cannot necessarily be applied to other regions, having an overall estimation of hospital admission costs and types of drugs used during admission could be helpful in health policy system

First Cystic Fibrosis Patient Registry Annual Data Report - Cystic Fibrosis Foundation of Iran

Cystic fibrosis (CF), as a fatal genetic condition, is associated with high morbidity and mortality rates. In Iran, limited studies exist on this disease. This study aims to compare the demographic, clinical and paraclinical data of CF patients. This cross-sectional study was conducted in 2014-2015 on 174 CF patients referred to the Tehran Children Medical Center hospital, which is the main referral center for CF. For each patient, the forced  expiratory volume in one second (FEV1) was measured and the comparative demographic, clinical and laboratory data of patients were recorded. Overall, 59% of studied patients were boys (n=102) and 41% were girls (n=72). The mean patient age (and standard deviations) was 7.1 ±5.7 years, with a range of 10 days to 28 years. In 67% of cases, the disease was diagnosed before their first birthday. The patients in this study were classified based on the FEV1 into mild (62%), moderate (33%) and sever (5%), indicating the degree of pulmonary complications. Cultures of respiratory secretions were positive for Pseudomonas aeruginosa and Staphylococcus aureus, in 23% and 16% of cases, respectively. In total, 61% of patients (n=83) were assigned to receive oral azithromycin for prophylaxis. Gastroesophageal reflux (reflux) was the most common gastrointestinal complication (35%), Regarding the complex nature of CF and the necessity of constant monitoring of patients during the life-span, the comparative demographic, clinical and laboratory analysis of patients and registering and standardization of patients’ data, can be a major step in the better understanding of the disease, and thereby increasing the quality of life and life expectancy in the affected population

A Review on Data-Driven Security Assessment of Power Systems: Trends and Applications of Artificial Intelligence

Boosting the complexity of the electricity network, penetration of renewable resources, and modernization of power systems has resulted in an increase in the complexity of the power systems security assessment (PSSA). In this context, to decrease the vulnerability of the systems to multiple instability threats and security issues while ensuring the safe operation of the power systems, providing effective online security assessment methods capable of monitoring the systems’ security under varying conditions is vital. However, although the traditional methods have demonstrated efficient PSSA performance, intelligent data-driven approaches have effectively overcome the traditional approaches by delivering impressive and rapid PSSA performance. Artificial intelligence (AI) -based techniques are required to guarantee the efficient, optimal, and safe security assessment. The usage of AI is emphasized due to its computational speed for online performance and its flexibility for providing corrective actions for insecure operating conditions to achieve a seamless transition in power systems. In this review, various available data-driven methods in power system security are comprehensively reviewed into two primary classifications: static and dynamic security assessment. The evaluated study aims to highlight the merits and demerits of developed techniques as well as their limitations to provide decision-making assistant for future investigations

An integrated method for under frequency load shedding based on hybrid intelligent system-part ii: UFLS design

The first part of this two part paper has proposed a novel strategy for frequency response modelling of modern power system, as it recommended a new application of artificial neural network in assessment of power system dynamic performance. The intelligent methods have shown a high ability in estimation and optimisation problems, as the recent advances in computer systems and intelligent methods have created new opportunities. The current paper proposes an integrated under frequency load shedding system based on genetic algorithm which is able to consider all effective factors at the same time. It also presents a new hybrid artificial neural network-genetic algorithm basis system for under frequency load shedding which is a quick, simple and applied method of UFLS. This assessment includes a review of significant researches on under frequency load shedding design and application

An integrated method for under frequency load shedding based on hybrid intelligent system-part i: dynamic simulation

Security is one of the most vital requirements in the operation of power systems. Frequency is a reliable indicator to determine instability condition in power system, i.e. the stability of power system is closely dependent on the value of system frequency. Under Frequency Load Shedding (UFLS) is one of the most important protection systems as in many cases it is the last action taken to prevent a system blackout after a serious disturbance occurs in power system. The first part of this two part paper presents various factors in modern power systems which have significant contribution on Under Frequency Load Shedding (UFLS). A high-order multi-machine frequency response model is utilized as it the best strategy of power system dynamic simulation. Classification of modern power system components and using an equal unit for each class is proposed in this work. The results show that ANN models can also be implemented as well as a fast dynamic simulator of electric power system. This assessment includes a review of significant researches on power system dynamic simulation and frequency response model leading to an integrated UFLS system design