Search

The article presents a calculation of a turbogenerator rotor air-cooling system with self-ventilation of the rotor winding from a sub-slot duct. The mathematical model proposed in the article reflects all the significant geometric parameters of the physical model as well as the gas dynamics of the cooling process. Research has been done into the impact of the profile of a sub-slot duct along the length of the rotor on air velocity distribution in radial ducts and on the efficiency of heat transfer in a 320 MW turbogenerator. The research has also shown that the maximum temperature of the rotor winding may be lowered by means of a sub-slot duct smoothly tapering to the middle of the axial rotor length (17% of the inlet section area of the sub-slot duct). Such configuration compensates air heat up along the rotor sub-slot duct due to the forced unevenness of air distribution in the radial ducts. [ABSTRACT FROM AUTHOR]

A new method of deembedding a test fixture effect from the data of microwave measurements is presented in this paper. It is shown that the traditional unterminating problem (the problem of finding fixture characteristics) being posed in a finite frequency range may be reduced to a problem of fitting the characteristics of the ‘thru’ experiment. The latter is proposed to be solved by using the genetic algorithm (GA). A special trick is suggested to take fixture power loss into consideration, which is sometimes necessary to increase the goodness of fitting the characteristics. Physically correct constraints for optimization variables and optimal parameters of the GA are discussed in this paper. The method is applicable for all microwave fixtures, except for those whose characteristics are influenced by the relative position of the adapters comprising the fixture. The method does not have any specific frequency limitation and does not require any calibration standards. The results of the experiments performed have validated a high efficiency of the method proposed, and confirm that the accuracy of a deembedding problem solution is close to the goodness of fitting data of the ‘thru’ experiment. [ABSTRACT FROM AUTHOR]

A mechanism to demodulate a two-tone high-frequency oscillation in nonlinear electronic devices due to an external electromagnetic field is investigated. The results of a demodulation are low-frequency disturbances to the internal circuits of electronic devices. A method for the synthesis of nonlinear compensators on the basis of the operational equations of electronic devices is offered for protection against low-frequency noise. The nonlinear operator of the compensator is designed so that a cascade connection of the electronic device and the compensator is described by the linear Volterra functional. As an example, the compensation of nonlinear transformations of a detector at high-frequency oscillation is synthesized with the use of results of measurements. The accuracy of the executed compensation is estimated [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach that extracts the maximum power from photovoltaic (PV) system utilizing the Horse Herd Optimization (HHO) algorithm under different weather conditions, including fast changes in solar radiation (FCSR) and partial shading conditions (PSCs). The HHO algorithm is a technique for optimization that mimics the movement behavior exhibited by horses within a herd. The proposed MPPT controller has been tested and compared with other recognized metaheuristic algorithms, including the Grey Wolf Optimizer (GWO), Particle Swarm Optimization (PSO), Flower Pollination (FP), Deterministic PSO (DPSO), and Cuckoo Search (CS). According to the simulation results, the proposed HHO-based MPPT method is found to outperform other considered metaheuristic methods in terms of the maximum power extraction, fast-tracking, and settling times under various weather conditions. Additionally, the suggested MPPT controller is robust and can continuously track the MPP under the FCSR. The performance of the proposed HHO controller is validated experimentally on a real PV system. It is demonstrated that the proposed HHO algorithm is robust and capable of outperforming the other counterpart metaheuristic algorithms as well as offering the highest MPPT efficiency of about 98.81 % with a rapid tracking time of 2.2 s. Furthermore, it has the lowest power oscillations of about 1.91 %, ensuring stable and consistent power output. [ABSTRACT FROM AUTHOR]

This paper presents the application of Flexible Alternating Current Transmission System (FACTS) devices based on heuristic algorithms in power systems. The work proposes the Autonomous Groups Particle Swarm Optimization (AGPSO) approach for the optimal placement and sizing of the Static Var Compensator (SVC) to minimize the total active power losses in transmission lines. A comparative study is conducted with other heuristic optimization algorithms such as Particle Swarm Optimization (PSO), Timevarying Acceleration Coefficients PSO (TACPSO), Improved PSO (IPSO), Modified PSO (MPSO), and Moth-Flam Optimization (MFO) algorithms to confirm the efficacy of the proposed algorithm. Computer simulations have been carried out on MATLAB with the MATPOWER additional package to evaluate the performance of the AGPSO algorithm on the IEEE 14 and 30 bus systems. The simulation results show that the proposed algorithm offers the best performance among all algorithms with the lowest active power losses and the highest convergence rate. [ABSTRACT FROM AUTHOR]

Centralized inverter technology is one of the most common architectures of the PV installation, which interfaces a large number of PV panels that configured in series-parallel (SP) combination to the grid. However, the power generated from centralized inverter architecture based on SP array topology is significantly reduced under the non-uniform aging condition. Non-uniform aging of PV panels is a common problem in the PV generation plants, as they often operate under harsh outdoor environmental conditions for a long service period. Due to the elevated price of replacing aged PV panels with new ones, it is preferable to improve the power extracted from aged PV systems. This paper proposes a circuit-based topology known as current collector optimizer (CCO) topology to enhance the performance of centralized inverter technology under the uneven aging condition of PV modules. According to the results, the maximum power extracted from the non-uniform aging PV array is substantially increased by using the CCO topology compared to the conventional SP array topology with bypass diodes. With CCOs, the PV array characteristics have a unique maximum power point (MPP) which can be easily followed by a simple MPP tracking algorithm, subsequently, the CCO topology does not suffer from misleading power losses. The proposed topology requires offline rearrangement of aged modules to obtain the optimum power if only the degradation rate of short-circuit current is used to assess the aging process. Furthermore, the CCO topology operates close to optimum power if the degradation rate of open-circuit voltage is taken into account. • CCO topology is used to enhance energy harvest from non-uniform aging PV modules. • CCO topology does not suffer from misleading power losses. • Optimum power is obtained if SC current is used to assess the aging process. • Close to optimum power is achieved when SC current and OC voltage are used to evaluate the aging process. [ABSTRACT FROM AUTHOR]

The use of sensitive electronics in avionics and wind generation systems, as well as the introduction of lower-conductivity composite materials make it important to ensure adequate lightning testing of airplanes and wind turbines. Evidence exists suggesting that standardized testing lightning waveforms produce damages that differ from those observed in actual strike events. The applicability of the present standard current waveforms for lightning testing is assessed in this paper and it is argued that waveforms based on upward flashes may be better suited as a basis for testing than the currently used tests, which are based on downward lightning and on airborne measured current bursts. Upward lightning data obtained at the Säntis Tower in Switzerland are also presented to support the need to revisit current waveforms used in standardized aircraft testing. [ABSTRACT FROM AUTHOR]