Electromagnetic shielding effectiveness of carbon/stainless steel/polypropylene hybrid yarn-based knitted fabrics and their composites

In this study, a range of conductive hybrid knitted fabrics and their composites have been investigated for shielding effectiveness in the frequency ranges of 50 MHz to 1.5 GHz (low frequency) and 4 to 8 GHz (C-Band). Carbon and stainless steel (SS) filaments were combined in Dref-3 spinning machine and different hybrid yarns were prepared. The plain- and rib-knitted fabrics were made in V-bed flat knitting machine from the prepared hybrid yarns. The composite laminate was prepared by sandwiching a ply of fabric between the polypropylene films in compression moulding machine at 180 °C for 5 min under a consolidation pressure of 12 bar. All the fabrics and composites were tested for shielding effectiveness (SE) in coaxial transmission line and C-band waveguide with the help of vector network analyser. It was observed that fabric having both conductive loop and inlaid yarns exhibited higher SE of 20.2 dB than other fabrics in low-frequency range. However, in the composite form, carbon composite with SS inlaid yarn showed better SE of 45 dB than other composites. In C-band frequency range, conductive loop fabric structures yielded high shielding effect in course direction compared to wales direction. Compared to fabric form, the composite showed higher SE for all frequency ranges. This study proposes that knitted fabrics and their composites can be utilized as electromagnetic shields in wide frequency ranges.     

Design of a Proportional-Integral-Derivative Controller for an Automatic Generation Control of Multi-area Power Thermal Systems Using Firefly Algorithm

Essentially, it is significant to supply the consumer with reliable and sufficient power. Since, power quality is mea sured by the consistency in frequency and power flow between control areas. Thus, in a power system operation and control, automatic generation control (AGC) plays a crucial role. In this paper, multi-area (Five areas: area 1, area 2, area 3, area 4 and area 5) reheat thermal power systems are considered with proportional-integral-derivative (PID) controller as a supplemen tary controller. Each area in the investigated power system is equipped with appropriate governor unit, turbine with reheater unit, generator and speed regulator unit. The PID controller parameters are optimized by considering nature bio-inspired firefly algorithm (FFA). The experimental results demonstrated the comparison of the proposed system performance (FFA-PID) with optimized PID controller based genetic algorithm (GA PID) and particle swarm optimization (PSO) technique (PSO PID) for the same investigated power system. The results proved the efficiency of employing the integral time absolute error (ITAE) cost function with one percent step load perturbation (1% SLP) in area 1. The proposed system based FFA achieved the least settling time compared to using the GA or the PSO algorithms, while, it attained good results with respect to the peak overshoot/undershoot. In addition, the FFA performance is improved with the increased number of iterations which outperformed the other optimization algorithms based controller.      

Application of flower pollination algorithm in load frequency control of multi-area interconnected power system with nonlinearity

This work presents an application of bio-inspired flower pollination algorithm (FPA) for tuning proportional–integral–derivative (PID) controller in load frequency control (LFC) of multi-area interconnected power system. The investigated power system comprises of three equal thermal power systems with appropriate PID controller. The controller gain [proportional gain (K _p), integral gain (K _i) and derivative gain (K _d)] values are tuned by using the FPA algorithm with one percent step load perturbation in area 1 (1 % SLP). The integral square error (ISE) is considered the objective function for the FPA. The supremacy performance of proposed algorithm for optimized PID controller is proved by comparing the results with genetic algorithm (GA) and particle swarm optimization (PSO)-based PID controller under the same investigated power system. In addition, the controller robustness is studied by considering appropriate generate rate constraint with nonlinearity in all areas. The result cumulative performance comparisons established that FPA-PID controller exhibit better performance compared to performances of GA-PID and PSO-PID controller-based power system with and without nonlinearity effect.