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Disturbance rejection performance optimization with constraints on robustness for a multivariable process is commonly encountered in industrial control applications. This paper presents the tuning of a multi-loop Proportional Integral (PI) controller method to enhance the performance of load disturbance rejection using evolutionary optimization. The proposed design methodology is formulated to minimize the load disturbance rejection response and the input control energy under the constraints of robust stability. The minimum singular value of multiplicative uncertainty is considered a multi-loop system robust stability indicator. Optimization is performed to achieve the same, or higher level than the most-explored Direct Synthesis (DS) based multi-loop PI controller, which is derived from a conventional criterion. Simulation analysis clearly proved that the proposed multi-loop PI controller tuning method gives better disturbance rejection, and either, the same or a higher level of robust stability when compared to the DS-based multi-loop PI controller. [ABSTRACT FROM AUTHOR]

The effectiveness of evolutionary algorithms (EAs) such as differential search algorithm (DSA), Real-Coded genetic algorithm with simulated binary crossover (RGA-SBX), particle swarm optimization (PSO), and chaotic gravitational search algorithm (CGSA) on the optimal design of cross-coupled nonlinear PID controllers is compared in this paper. A cross-coupled multivariable PID controller structure for the binary distillation column was developed with two inputs and two outputs. EA simulations are run to lower IAE using two stopping criteria, namely, maximum number of functional evaluations (Fevalmax) and Fevalmax plus PID parameter and IAE tolerance. Over 20 separate trials were used to compare the performances of several EAs using statistical measures such as best, mean, standard deviation of outcomes, and average calculation time. This article presents the design of a cross-coupled nonlinear PID controller using single-objective evolutionary algorithms. Using evolutionary algorithms (EAs) with a multicrossover strategy, the results achieved by various EAs are compared to previously reported results. The results of a multivariable cross-coupled system clearly show that a single-objective nonlinear PID controller performs better. Simulations further show that all four techniques evaluated are suitable for PID controller tweaking off-line. However, only the single-objective evolutionary algorithms are acceptable for online PID tuning due to their higher consistency and shorter computation time. [ABSTRACT FROM AUTHOR]

The buck converter is one of the DC/DC converters that are often used as power supplies and high energy conversion. These controllers are used in electronic devices to regulate the output voltage against change in the input voltage and load current. This leads to the requirement of an efficient control methodology to meet real-time demand. It is found in many works of literature that satisfactory performance in buck converter's dynamic behavior using genetic algorithm controlling techniques, but the appearance of the transient with large overshoots and the ripple output voltage is not focused. The main reason for such a problem is the improper selection of capacitance values. In this work, to address such issues, along with the PID controller gain values and capacitance selection also be considered in multi-objective problems. The optimization is carried out using the NSGA-II and modified NSGA-II algorithm. This paper also presents a comparison of these algorithms' performance in terms of time-domain specifications and ripple voltage. Simulated outputs exhibit that the controller based on MNSGA-II for buck converter gives better performance than NSGA-II-based controller and results compared with the existing wok. The MNSGA–II-based PID controller for buck converted validated in the real-time environment also. [ABSTRACT FROM AUTHOR]

The time delay element present in the PI controller brings dead-time compensation capability and shows improved performance for dead-time processes. However, design of robust time delayed PI controller needs much responsiveness for uncertainty in dead-time processes. Hence in this paper, robustness of time delayed PI controller has been analyzed for First Order plus Dead-Time (FOPDT) process model. The process having dead-time greater than three times of time constant is very sensitive to dead-time variation. A first order filter is introduced to ensure robustness. Furthermore, integral time constant of time delayed PI controller is modified to attain better regulatory performance for the lag-dominant processes. The FOPDT process models are classified into dead-time/lag dominated on the basis of dead-time to time constant ratio. A unified tuning method is developed for processes with a number of dead-time to time constant ratio. Several simulation examples and experimental evaluation are exhibited to show the efficiency of the proposed unified tuning technique. The applicability to the process models other than FOPDT such as high-order, integrating, right half plane zero systems are also demonstrated via simulation examples. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) measurement is used for a diagnosis and performance assessment of the solid insulation material inside the high-voltage (HV) equipment. PD measurement indicates the presence of voids, cracks and imperfection present in solid insulation material. The major problem associated with this measured PD signal is heavily contaminated by noise which results in reduction in PD pattern recognition. The objective of this work is to measure and de-noise the PD signal due to cavity and recognize two different size of cavities present in three different locations, namely near HV electrode, center and lower electrode. In first part, the measured PD signal is de-noised using translation invariant wavelet transform. In second part, the three-dimensional (φ–q–n) PD patterns are extracted from the de-noised PD data. Then, it is subjected to canny edge detection technique, and the features like horizontal and vertical fractal dimension averages are evaluated using fractal image compression-based semi-variance technique. For classification, multi-class nonlinear support vector machine has been proposed to classify position and size of the cavity based on the PD fingerprints. The findings of this proposed work can be used to design a solid basis for an recognition of cavity size and position in an electrical apparatus. [ABSTRACT FROM AUTHOR]

In many of the high voltage apparatus, liquid insulation is used as the coolant and isolating medium between conducting parts. Petroleum based mineral oil is utilized as one of the liquid insulation in most of the applications such as transformers, oil bushing and etc. Recently many research works are engaged in the development of alternate liquid insulation with vegetable oil based natural esters. Major concern with natural esters is their higher viscosity which influences in the cooling characteristics of liquid insulation. With the aim of reducing the viscosity, the edible natural esters are treated with ultrasonic waves of 100 W ultrasonic power at a fixed frequency of 30 kHz. This work is carried out with edible natural esters such as sunflower oil (SFO), palm oil (PO) and sesame oil (SO). Further analysis on the impact of ultrasonic wave for different exposure conditions, the natural esters are exposed to ultrasonic waves for different time period of 15 minutes to 60 minutes with different temperatures of 30, 60 and 90°C in ultrasonic wave treatment setup. This process results in the reduction of viscosity of natural esters after ultrasonic treatment. The influence of ultrasonic waves on viscosity is studied by measuring the values of viscosity of treated natural esters after 24 and 720 hours for analyzing the retention of reduction in viscosity after treatment. This investigation reveals that the ultrasonic waves have impact on the reduction of viscosity of natural esters. Also the outcome of the ultrasonic treatment is derived as the mathematical model to estimate the viscosity values for different processing temperature and exposure time. [ABSTRACT FROM AUTHOR]

In the recent decades, the natural esters have gained more attention as an alternate liquid insulation instead of the petroleum based mineral oil due to the development on power system networks and their environmental friendly nature. The failure free functioning of high voltage transformer mainly depends on the reliability of insulation used inside it. In this work, edible and non edible natural esters are studied and analyzed by using statistical distribution of the AC breakdown voltage in order to ensure their reliability. In this investigation work, sunflower oil (SFO), palm oil (PO) and sesame oil (SO) are studied under the category of edible natural esters, while honge oil (HO), neem oil (NEO) and punna oil (PAO) are analyzed under the non edible natural esters category. The applicability of investigated esters as liquid insulation is analyzed with distribution models like normal, Weibull and generalized extreme value (GEV) distributions. The statistical failure reliability analysis is carried out with the distribution functions such as survival rate, hazard rate and failure rate from the 100 distributed values of AC breakdown voltages of the investigating natural esters. The statistical analysis reveals the better characteristics for natural esters (edible and non edible) such as superior survival rate at higher value of electric stress, possibility of failure occurrence only at the wear out range and elevated statistical withstand voltage at various failure rates. Comparing both the category of natural esters, non edible natural esters have shown the superior characteristics than the edible natural esters. Consequently, it is evident that the natural esters are reliable and potential surrogate to the conventional liquid insulation for the application in high voltage transformers. [ABSTRACT FROM AUTHOR]

This paper investigates an optimized design of newly developed nonlinear controller called finitetime convergent controller to a third-order boiler-turbine dynamics. The third-order boiler-turbine dynamics only includes highly nonlinear and critical parameters of thermal plant like drum pressure, electric power and drum level; the design of controller is always a complicated task. The present work explores the possibility of application of newly developed finite-time convergent controller to a third-order boiler-turbine dynamics. The novelty of the newly developed finite-time convergent controller is complete utilization of system nonlinearities instead of cancelling or linearizing them. Also, the finite-time convergent controller ensures robustness and fast convergence. To achieve optimal performance, the tuning parameters involved in finite-time convergent controller have been optimized using evolutionary algorithm techniques. To validate the control performance of an optimized nonlinear controller design, simulations have been conducted using various evolutionary algorithm techniques and the results are reported as various case studies. To compare the performance of proposed optimized finite-time convergent controller, the fuzzy logic controller has also been designed using ANFIS for boiler-turbine system and the results are reported. [ABSTRACT FROM AUTHOR]

This work is focused towards identifying alternate insulating medium for replacing the mineral oil. With this aim, investigations are carried out with natural esters based vegetable oils which are considered as environmental friendly and biodegradable products. This work also extends to analyze the properties of vegetable oils with the antioxidants for enhanced insulating medium of transformer applications. The natural esters based vegetable oils such as honge oil, neem oil, mustard oil, punna oil and castor oil are considered as samples for the investigations. The butylated hydroxy toluene, butyalted hydroxy anisole and gallic acid are picked as the investigating antioxidants. Different particle volume fraction ranges from 0% to 1% of antioxidants are included for studying the performance of natural esters. The performances of natural esters without and with antioxidants are examined according to the international standards. From the investigation results, it is found that the natural esters based vegetable oils without and with antioxidants have the potential to replace the mineral oil as the insulating medium in the transformers. The mathematical functions for properties are developed based on the results obtained for various concentration of antioxidant. These functions are used to estimate the intermediate values of properties for different antioxidant concentrations. [ABSTRACT FROM AUTHOR]

Increasing power demand forces the development of the high-rated power transformers. In a transformer, petroleum-based mineral oil is used as insulation currently. Transformer oil (TO) produces environmental and health issues because it is nonbiodegradable. The availability of petroleum products is decreasing in the present century. So it encourages researchers to find potential replacements for them. In this work, two natural ester oils (rice bran oil and corn oil) were taken up for investigation to find their suitability for use in transformers. Aging analysis was performed on the TO and natural esters. For this, properties like breakdown voltage, flash point, fire point, viscosity, acidity, resistivity, and loss factor of the natural esters were considered. From the investigations, it was evident that rice bran and corn oil have the ability to be used as alternatives for TO. [ABSTRACT FROM AUTHOR]

Power transformers are one of the critical components in power system. Insulation plays a promistic role in determining the lifetime of transformers. Insulation used in transformers is of solid and liquid insulation. Solid insulation like kraft paper, press board on degradation process generates furanic derivatives such as 5‐methyl furan, 2‐acetyl furan, 2‐hydroxymethyl furan and 2‐furaldehyde. Traditionally, the presence of furanic compounds in transformer oil is determined using high‐sperformance liquid chromatography. An effort has been made to estimate the presence of furanic derivatives using artificial neural network (ANN) with the aid of ultra‐violet–visible light absorbance property. In ANN system, Levenberg Marquardt back propagation optimisation technique is used to determine the furanic derivatives in transformer oil. Degree of polymerisation of insulation paper and percentage tensile strength of paper remaining has been examined. [ABSTRACT FROM AUTHOR]

The optimized placements of mobile antennas (MA) in an existing high traffic urban area are identified using evolutionary multiobjective optimization algorithms (EMOA). The design parameters such as ( x, y) coordinates, transmitting power, height, and tilt are considered. The objectives are coverage and cost where as the inequality constraints are handover, traffic demand, and overlap. Modified NSGA-II (MNSGA-II) is preferred to improve the non dominated solutions. A detailed study is performed about physical and geometrical structure of propagation environment. Four different case studies are performed. The simulation results reveal that Hata-Okumura path loss model is more suited. MNSGA-II is able to determine optimal MA parameters for multiobjective case studies. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:737-743, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26627 [ABSTRACT FROM AUTHOR]

This article presents a covariance matrix adapted evolution strategy (CMAES) algorithm to solve dynamic economic dispatch (DED) problems. The DED is an extension of the conventional economic dispatch problem, in which optimal settings of generator units are determined with a predicted load demand over a period of time. In this article, the applicability and validity of the CMAES algorithm is demonstrated on three DED test systems with a sequential decomposition approach. The results obtained using the CMAES algorithm are compared with results obtained using the real-coded genetic algorithm, the Nelder-Mead simplex method, and other methods from the literature. To compare the performance of the various algorithms, statistical measures like best, mean, worst, standard deviation, and mean computation time over 20 independent runs are taken. The effect of population size on the performance of the CMAES algorithm is also investigated. The simulation experiments reveal that the CMAES algorithm performs better in terms of fuel cost and solution consistency. Karush-Kuhn-Tucker conditions are applied to the solutions obtained using the CMAES algorithm to verify optimality. It is found that the obtained results satisfy the Karush-Kuhn-Tucker conditions and confirm optimality. [ABSTRACT FROM AUTHOR]

The application and performance comparisons of various evolutionary algorithms (EA) on economic dispatch (ED) problems with non-smooth cost functions considering valve-point effects and multiple fuel options are presented. The EAs such as the real-coded genetic algorithm, particle swarm optimisation (PSO) and differential evolution (DE) are considered. New penalty parameter-less constraint-handling scheme is employed to improve the performance of EA. Ten-generator ED test system is taken for simulation purposes. To determine the efficiency and effectiveness of various EAs, two experiments are conducted, considering only multiple fuel options and considering both valve-point and multiple fuel options. The optimal results obtained using various EAs are compared with Nelder–Mead simplex method and previous reported results. To compare the performances of various EAs, statistical measures such as best, mean, worst, standard deviation and mean computation time over 20 independent runs are taken. The simulation experiments reveal that PSO performs better in terms of solution quality and consistency. DE performs better in terms of mean computation time. For the first time, Karush–Kuhn–Tucker (KKT) conditions are applied to the solutions obtained using EAs to verify optimality. It is found that the obtained results are satisfying the KKT conditions and confirm the optimality. Also, the effectiveness of KKT-based stopping criteria is clearly demonstrated. [ABSTRACT FROM AUTHOR]