The present paper proposes a novel multi‐objective robust fuzzy fractional order proportional–integral–derivative (PID) controller design for nonlinear hydraulic turbine governing system (HTGS) by using evolutionary computation techniques. The fuzzy fractional order PID (FOPID) controller takes closed loop error and its fractional derivative as inputs and performs fuzzy logic operations. Then, it produces the output through the fractional order integrator. The predominant advantages of the proposed controller are its capability to handle complex nonlinear processes like HTGS in heuristic manner, due to fuzzy incorporation and extending an additional flexibility in tuning the order of fractional derivative/integral terms to enhance the closed loop performance. The present work formulates the optimal tuning problem of fuzzy FOPID controller for HTGS as a multi‐objective one instead of a traditional single‐objective one towards satisfying the conflicting criteria such as less settling time and minimum damped oscillations simultaneously to ensure the improved dynamic performance of HTGS. The multi‐objective evolutionary computation techniques such as non‐dominated sorting genetic algorithm‐II (NSGA‐II) and modified NSGA‐II have been utilized to find the optimal input/output scaling factors of the proposed controller along with the order of fractional derivative/integral terms for HTGS system under no load and load turbulence conditions. The performance of the proposed fuzzy FOPID controller is compared with PID and FOPID controllers. The simulations have been conducted to test the tracking capability and robust performance of HTGS during dynamic set point changes for a wide range of operating conditions and model parameter variations, respectively. The proposed robust fuzzy FOPID controller has ensured better fitness value and better time domain specifications than the PID and FOPID controllers, during optimization towards satisfying the conflicting objectives such as less settling time and minimum damped oscillations simultaneously, due to its special inheritance of fuzzy and FOPID properties.
This paper discusses the performance comparison of Evolutionary Algorithm techniques with a view to tuning the desired design parameters of robust PID controller with filter. The design parameters of robust PID controller such as proportional gain K P , integral time constant T i , derivative time constant T d and filter time constant t d /N for Single Input Single Output (SISO) system are computed using Real coded Genetic Algorithm (RGA), Differential Evolution (DE) algorithm and Particle Swarm Optimization (PSO) algorithm. The design parameters are optimized using the statistical measures in twenty independent simulation runs. The computed design parameters obtained using Evolutionary Algorithms are used to determine the performance specifications of the Robust PID controller. The performance specifications determined are robustness with respect to model uncertainties and disturbance attenuation, set point tracking, load disturbance rejection and control energy. The test systems used to ascertain the performance specifications are Phase Locked Loop (PLL) system with motor control and Magnetic Levitation system (MLS). For PLL system, the output response obtained using the computed design parameters by RGA algorithm has proved to be better than DE and PSO. For MLS system, the output response obtained using the computed design parameters by DE algorithm has been better than PSO and RGA. meet out the performance specifications of the given system mainly depends on the tuning of the controller .Since the system has nonlinear plant and various uncertainties the tuning of the robust PID controller becomes difficult. This leads to poor tuning. The reasons of the poor tuning is due to a) lack of knowledge among operators and commissioning personnel b) variety of PID structures that leads to error during tuning c) in some cases the nature of tuning method do not meet the requirement of the process involved [3]. Out of the installed PID controllers in industry, nearly one third controllers are tuned manually and remaining two third are tuned automatically. But the automatically tuned PID controllers are not effective [7].To overcome these limitations optimization algorithms are used for the tuning of robust PID controller. In the past many researchers have used different optimization algorithm for tuning the parameters of robust PID controller. But the parameter tuned to meet out the performance specifications of the system is different in each case. Many researchers have considered set In this paper, Evolutionary algorithm is used to determine the optimal parameters for the robust optimal controller. Evolutionary Algorithms used are Particle Swarm Optimization (PSO), Real coded Genetic Algorithm (RGA) and Differential Evolution (DE). The main focus of this paper is to determine the design parameters of robust PID controller using evolutionary algorithm such that it meet out the system performance specifications like robustness with respect to model uncertainties and disturbance attenuation, set point tracking,...
Summary
Power transformer plays a vital role in power system network, and it mainly consists of liquid and solid insulations. In this mineral oil plays a major insulation role and cooling purpose. Moisture and prolonged electric stress leads the way for ageing in transformer insulation. It results in degradation of insulation properties and hindrance in uninterrupted operation. Due to thermal degradation, insulation loosens its dielectric withstand properties. To avoid this, periodic condition monitoring is required to protect the transformer insulation. In this work, an effort has been taken to investigate the aged mineral oil using semiconductive nanocomposites by retreatment technique. The nanocomposites are added with the aged oil in different volume fractions to evaluate the enhancement level of aged oil for reutilization purpose. The critical properties like breakdown voltage, dielectric loss, resistivity, dielectric permittivity, viscosity, flash point, and acidity of the samples before and after treatment are measured according to American Society for Testing and Materials (ASTM) and International Electro‐technical Commission (IEC) standards. It is found that semiconductive nanocomposites improve the critical properties of aged oil and suitable proportion of volume fractions shows impressively enhanced results than base fluid samples. The result paves a new way in economic retreatment of aged oil under environmental friendly nature for reutilization purpose.
For insulating liquids in power transformers, the development of low viscous vegetable oil based liquids has been proposed in this work. The viscosity reduction of vegetable oil based liquids has been achieved by processing of the natural esters with different levels of concentration of aromatic solvent of benzyl benzoate. Two categories of vegetable oil based liquids, namely edible such as sunflower oil, palm oil and sesame oil, and non edible such as honge oil, neem oil and punna oil are considered for this investigation. The analysis is also extended to investigate the influence of benzyl benzoate on other critical properties of vegetable oil based liquids such as breakdown voltage, flash point, moisture content, acidity, and density. From the experimental results, it is revealed that inclusion of benzyl benzoate has shown considerable reduction in viscosity of vegetable oil based liquids. Also based on properties of processed natural esters, results have given away the positive encouragement towards the development of low viscous insulating liquids with combined benzyl benzoate and natural esters for application in high voltage power transformers.
In the present developed work, a new controller design methodology of Internal Model Controller has been proposed for improving the closed-loop response. The IMC controller has been viewed into its gain and dynamic parts. The key strategic difference is that the controller dynamic part has a generalized structure. The designer has the choice to select between low and high-order controllers to outfit the control applications better. The controller order has been considered in terms of simple first/second-order type, and the design guidelines are presented. As in the case of the traditional IMC controller, there is principally a single variable parameter in the developed IMC controller, which can be monotonically tuned to meet the compromise between achievable performance and the stability of a closed-loop system. The merits and applications of the developed IMC controller design methodology for high-order systems have been evaluated using several simulation examples.
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