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The Single Linear Induction Motor (SLIM) is a specialized electrical machine that produces linear motion instead of the rotary motion produced by a traditional rotary induction motor. SLIM's accurate dynamic model is required to analyze the performance of the motor under different operating conditions. Dynamic modelling of SLIM using the traditional DQ- axis equivalent circuits is difficult due to the time-varying parameters such as end effect, air gap flux, saturation, and half-filled slot. The two methods for modelling SLIMs were compared, namely the conventional method and the split method. The results of the comparison showed that both methods provided similar results, but the split method offered a more detailed analysis of the components and provided deeper insight into the behavior of the motor. The choice between the two methods depends on the specific requirements and objectives of the analysis. In this paper, the dynamic model of SLIM is modelled using conventional and split methods in MATLAB/SIMULINK. The results of the two modelling methods are compared with each other, and it is concluded that the splitting method provides better transient performance than traditional D-Q axis methods.

Normally speed control of a Single-Sided Linear Induction Motor (SLIM) by an indirect vector control scheme is difficult because the motor's parameters are time-dependent and the performance depends on various factors such as end effect, saturation, location of primary losses, and iron losses. Traditional PI current regulators are commonly used in vector regulators, but there is a tuning problem due to the oscillation of an operating point. This problem can be overcome by substituting an adaptive neuro-fuzzy-based current controller, and this controller improves the operation of a SLIM, such as its motor speed and thrust force. In this adaptive neuro-fuzzy controller, the ID and IQ errors and the error delay are inputs, and its outputs are Vds and Vqs, respectively. It is trained based on available values. A SLIM's dynamic modelling is implemented by dividing current (I) and flux-linkages into two terms. In these two terms, one is dependent on the end effect, and the other is independent of the end effect. The function of a Voltage Source Inverter (VSI)-fed indirect vector-controlled SLIM drive is simulated in MATLAB/Simulink, and its operation under various operating conditions is studied using an adaptive neuro-fuzzy current controller. These results are compared to a traditional P-I controller. The Pulse Width Modulation (PWM) technology that is used for controlling the VSI is called Space Vector Modulation (SVM).

To improve the dynamic stability of power systems, by increasing the damping torque of the synchronous machine, it is necessary to use the power system stabilizers to enhance the damping during low frequency oscillations. In this article, an attempt has been made to design the parameters of power system stabilizer by using the Firefly Algorithm applied to the single machine infinite bus system to an amenable form. The stability enhancement has been compared with Genetic Algorithm stabilizer for different operating conditions. The results show that the designed power system stabilizer based on Firefly Algorithm gives a good dynamic response when compared to Genetic Algorithm power system stabilizer. The Pseudo Spectrum analysis is also presented which is evident about the enhanced stability of the system with the proposed Algorithm.

Le système électrique interconnecté est un système complexe dont le maintien de la stabilité est le facteur important du synchronisme par rapport à tous les générateurs connectés au système. Afin de maintenir le synchronisme parmi tous les générateurs et toutes les charges interconnectées, la stabilité de chaque machine individuelle ainsi que la stabilité des machines interconnectées sont importante. Le réglage du couple d'amortissement ou la fourniture suffisante du couple d'amortissement à la machine synchrone, ce qui augmente la stabilité du système, est effectué en appliquant le stabilisateur du système d'alimentation. Cet article présente une tentative de conception de ce stabilisateur en utilisant l’algorithme de recherche «Firefly » afin d’accroître la stabilité du système de « three machine nine bus » , qui est un système interconnecté de générateurs hydro-thermiques. La stabilité améliorée du système multi-machine a été comparée avec le stabilisateur d'algorithme de recherche génétique. Il est évident que l'amélioration de la stabilité du système multi-machine est réalisée en obtenant des valeurs propres Eigen. Il montre également les réponses des variations relatives des états interconnectés du système multi-machine soumis dans la condition non-linéaire. Les réponses du stabilisateur de système d'alimentation « Firefly » sont réglées plus rapidement pour le cas normal et aussi pour les cas de contigence. Les résultats sont comparés au stabilisant de l’algorithme génétique. Dans l'observation Pseudo Spectrum, les pôles stables du système sont évidents pour améliorer la stabilité du système multi-machine. TITRE Conception d'un stabilisateur de système d'alimentation « Firefly » pour l'amélioration de la stabilité d'un système multi-machines en cas de contigence TITLE Design of firefly power system stabilizer for stability improvement of multi machine system under contingency RÉSUMÉ Le système électrique interconnecté est un système complexe dont le maintien de la stabilité est le facteur important du synchronisme par rapport à tous les générateurs connectés au système. Afin de maintenir le synchronisme parmi tous les générateurs et toutes les charges interconnectées, la stabilité de chaque machine individuelle ainsi que la stabilité des machines interconnectées sont importante. Le réglage du couple d'amortissement ou la fourniture suffisante du couple d'amortissement à la machine synchrone, ce qui augmente la stabilité du système, est effectué en appliquant le stabilisateur du système d'alimentation. Cet article présente une tentative de conception de ce stabilisateur en utilisant l’algorithme de recherche «Firefly » afin d’accroître la stabilité du système de « three machine nine bus » , qui est un système interconnecté de générateurs hydro-thermiques. La stabilité améliorée du système multi-machine a été comparée avec le stabilisateur d'algorithme de recherche génétique. Il est évident que l'amélioration de la stabilité du système multi-machine est réalisée en obtenant des valeurs propres Eigen. Il montre également les réponses des variations relatives des états interconnectés du système multi-machine soumis dans la condition non-linéaire. Les réponses du stabilisateur de système d'alimentation « Firefly » sont réglées plus rapidement pour le cas normal et aussi pour les cas de contigence. Les résultats sont comparés au stabilisant de l’algorithme génétique. Dans l'observation Pseudo Spectrum, les pôles stables du système sont évidents pour améliorer la stabilité du système multi-machine. ABSTRACT Interconnected power system is the complex system which is having the stability maintenance as the important factor to be in the synchronism with respect to all generators connected to the system. To maintain the synchronism among all generators and loads that are interconnected, the stability of each individual machine and also the stability of interconnected machines have gained importance. Damping torque adjustment or sufficient supply of the damping torque to the synchronous machine which will increase the stability of the system is done by applying the power system stabilizer. This paper presents an attempt to design the power system stabilizer using the Firefly search Algorithm to increase the stability of the three machine nine bus system which is an interconnected system of hydro thermal generators. The enhanced stability of the multi machine system was compared with Genetic search Algorithm stabilizer. It is evident that the enhancement of the stability of the multi machine system is achieved by getting the stable Eigen values. It is also observed that the responses of relative variations of interconnected states of the multi machine system with under the nonlinearity condition. The responses of the system with firefly based power system stabilizer are settled at faster rate for the normal case and also for the contingency cases. The results are compared with the genetic algorithm stabilizer. In the Pseudo Spectrum observation the stable poles of the system are evident for the improved stability of the multi machine system. AUTHOR(S) M. RAVINDRABABU, G. SARASWATHI, K. R. SUDHA MOTS-CLÉS stabilisateur de système électrique (PSS en anglais), algorithme de « Firefly » (FFY en anglais), algorithme de génétique (GA en anglais), analyse de pseudo spectre, contigence. KEYWORDS power system stabilizer (PSS), firefly algorithm (FFY), genetic algorithm (GA), pseudo spectrum analysis, contingency. ARTICLE LANGUAGE English

The stability phenomenon of a synchronous machine plays a major role in the interconnected power systems. The dynamic stability of multi machine system can be improved by providing the compensating damping torque to the synchronous generator. Design of power system stabilizer is necessary to enhance the stability of the synchronous generator. The effect of a power system stabilizer located at machine certainly influences the stability of other machines. In this proposed approach, the power system stabilizer is designed by using firefly algorithm for the improvement of stability of a three machine system. The designed stabilizer's performance is observed for different locations of the system and compared with the performance of stabilizer designed by using genetic algorithm. From the results, the power system stabilizer designed from firefly algorithm gives an improved stable performance than a genetic algorithm based power system stabilizer. The stable eigen values are analyzed by using pseudo spectrum analysis. The step responses of each state of the three machines shows that the proposed stabilizer gives enhanced stability of the total system.

The multi machine power system, with the interconnection of number of generators and loads, has the dynamic stability as the important factor for maintaining the step with respect to the generators connected to it. The stability of individual machine, as well as, the stability of a generator with the other generators are more important terms. The supply of the damping torque required for getting the desired condition of stability enhancement is done by the power system stabilizer. In this paper a new method is proposed for stability enhancement of a three machine nine bus system by using the coordinated application of the unified power flow controller and the power system stabilizer designed by using the Firefly algorithm. The improved stability performance of the tested multi machine system was compared with Genetic search algorithm approach without and with the application of the unified power flow controller. From the pseudo spectrum analysis, it is observed that the better improvement of the stability of the multi machine system is achieved by using the proposed method. From the step responses it can be deduced that the relative variations of inter machine states with unified power flow controller and firefly-based power system stabilizer are settled at a faster rate. The contingency analysis is performed to consider the non-linearity problem. The responses of the system with unified power flow controller and firefly based power system stabilizer are settled at a faster rate in the normal case, as well as, in the contingency cases, respectively.

We describe and show results from a series of field campaigns that used balloonborne instruments launched from India and Saudi Arabia during the summers 2014–17 to study the nature, formation, and impacts of the Asian Tropopause Aerosol Layer (ATAL). The campaign goals were to i) characterize the optical, physical, and chemical properties of the ATAL; ii) assess its impacts on water vapor and ozone; and iii) understand the role of convection in its formation. To address these objectives, we launched 68 balloons from four locations, one in Saudi Arabia and three in India, with payload weights ranging from 1.5 to 50 kg. We measured meteorological parameters; ozone; water vapor; and aerosol backscatter, concentration, volatility, and composition in the upper troposphere and lower stratosphere (UTLS) region. We found peaks in aerosol concentrations of up to 25 cm–3 for radii > 94 nm, associated with a scattering ratio at 940 nm of ∼1.9 near the cold-point tropopause. During medium-duration balloon flights near the tropopause, we collected aerosols and found, after offline ion chromatography analysis, the dominant presence of nitrate ions with a concentration of about 100 ng m–3. Deep convection was found to influence aerosol loadings 1 km above the cold-point tropopause. The Balloon Measurements of the Asian Tropopause Aerosol Layer (BATAL) project will continue for the next 3–4 years, and the results gathered will be used to formulate a future National Aeronautics and Space Administration–Indian Space Research Organisation (NASA–ISRO) airborne campaign with NASA high-altitude aircraft.

It is well reported that the 2015–16 El Niño event is one of the most intense and long lasting events in the 21st century. The quantified changes in the trace gases (Ozone (O3), Carbon Monoxide (CO) and Water Vapour (WV)) in the tropical upper troposphere and lower stratosphere (UTLS) region are delineated using Aura Microwave Limb Sounder (MLS) and Atmosphere Infrared Radio Sounder (AIRS) satellite observations from June to December 2015. Prior to reaching its peak intensity of El Niño 2015–16, large anomalies in the trace gases (O3 and CO) were detected in the tropical UTLS region, which is a record high in the 21st century. A strong decrease in the UTLS (at 100 and 82 hPa) ozone (~200 ppbv) in July-August 2015 was noticed over the entire equatorial region followed by large enhancement in the CO (150 ppbv) from September to November 2015. The enhancement in the CO is more prevalent over the South East Asia (SEA) and Western Pacific (WP) regions where large anomalies of WV in the lower stratosphere are observed in December 2015. Dominant positive cold point tropopause temperature (CPT-T) anomalies (~5 K) are also noticed over the SEA and WP regions from the high-resolution Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Global Position System (GPS) Radio Occultation (RO) temperature profiles. These observed anomalies are explained in the light of dynamics and circulation changes during El Niño.

Over the Indian region, changes in the tropopause parameters during pre‐monsoon to monsoon seasons have been reported. However, no study exists to date dealing with the Indian summer monsoon (ISM) onset signatures on the tropopause parameters. In the present study, the climatological structure of the tropical tropopause layer during the onset phase of ISM is delineated by using long‐term (2006–2017) radiosonde observations over Gadanki (13.5°N, 79.2°E). A prominent transition in the tropopause parameters from pre‐monsoon to monsoon is noticed and the transition is initiated from the day of ISM onset. Continuous decrease (increase) of tropopause altitude (temperature) is perceived after the ISM onset. The ozonesonde observations clearly show the strong enhancement in the ozone mixing ratio in the lower stratosphere (~16–20 km) after the ISM onset. This clearly demonstrates the instantaneous warming of the tropopause region after the ISM onset in addition to the latent heat release due to the precipitation. Transitions from pre‐monsoon to monsoon in the tropopause parameters are influenced strongly by onset of ISM which was attributed as seasonal changes earlier. These results provide strong evidence on the ISM onset signatures on the tropical tropopause parameters. Climatological mean day‐to‐day variability of CPH, CPT, LRH, LRT, COH, COT, TTL thickness and OLR observed during monsoon onset. The effect of ISM onset/arrival is observed on the tropopause parameters with decrease (increase) in the tropopause altitudes (temperatures) and minimum in the TTL thickness. Transitions from pre‐monsoon to monsoon in the tropopause parameters are influenced strongly by onset of ISM which was earlier attributed as seasonal change.