Introduction to Electromagnetic Compatibility

Particle swarm optimization (PSO) is one of the well-known population-based techniques used in global optimization and many engineering problems. Despite its simplicity and efficiency, the PSO has problems as being trapped in local minima due to premature convergence and weakness of global search capability. To overcome these disadvantages, the PSO is combined with Levy flight in this study. Levy flight is a random walk determining stepsize using Levy distribution. Being used Levy flight, a more efficient search takes place in the search space thanks to the long jumps to be made by the particles. In the proposed method, a limit value is defined for each particle, and if the particles could not improve self-solutions at the end of current iteration, this limit is increased. If the limit value determined is exceeded by a particle, the particle is redistributed in the search space with Levy flight method. To get rid of local minima and improve global search capability are ensured via this distribution in the basic PSO. The performance and accuracy of the proposed method called as Levy flight particle swarm optimization (LFPSO) are examined on well-known unimodal and multimodal benchmark functions. Experimental results show that the LFPSO is clearly seen to be more successful than one of the state-of-the-art PSO (SPSO) and the other PSO variants in terms of solution quality and robustness. The results are also statistically compared, and a significant difference is observed between the SPSO and the LFPSO methods. Furthermore, the results of proposed method are also compared with the results of well-known and recent population-based optimization methods.

A novel particle swarm optimization algorithm with Levy flight

For large photovoltaic power generation plants, number of panels are interconnected in series and parallel to form a photovoltaic (PV) array. In this configuration, partial shade will result in decrease in power output and introduce multiple peaks in the P–V curve. As a consequence, the modules in the array will deliver different row currents. Therefore, to maximize the power extraction from PV array, the panels need to be reconfigured for row current difference minimization. Row current minimization via Su Do Ku game theory do physical relocation of panels may cause laborious work and lengthy interconnecting ties. Hence, in this paper, an alternative to physical relocation based on particle swarm optimization (PSO) connected modules is proposed. In this method, the physical location of the modules remains unchanged, while its electrical connections are altered. Extensive simulations with different shade patterns are carried out and thorough analysis with the help of I–V , P–V curves is carried out to support the usefulness of the proposed method. The effectiveness of proposed PSO technique is evaluated via performance analysis based on energy saving and income generation. Further, a comprehensive comparison of various electrical array reconfiguration based is performed at the last to examine the suitability of proposed array reconfiguration method.

Particle Swarm Optimization Based Solar PV Array Reconfiguration of the Maximum Power Extraction Under Partial Shading Conditions

The amount of literature on partial discharge (PD) and partial discharge induced degradation is vast. In the past 10-20 years significant progress has been made on research within partial discharge induced aging of dielectrics. Researchers now agree on the main mechanisms pertaining to this topic. With the advent of a new generation of dielectrics of which many properties now can be affected by the introduction of small amounts of nano-sized particles it seems to be a good moment to review the progress on the understanding of PD induced aging. Focusing on internal partial discharge in solid polymeric insulation this paper tries to identify achievements and at the same time challenges still to be solved.

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Degradation of solid dielectrics due to internal partial discharge: some thoughts on progress made and where to go now

Photovoltaic (PV) power system performance depends on local irradiance conditions. PV systems are sometimes subject to partial shading, which may produce a nonideal characteristic curve, presenting true and local power maxima in the P -I curve. Traditional maximum power point tracking (MPPT) algorithms can converge to local maximum, which is not the true MPP. In order to solve the problem, this paper investigates the effects of nonuniform solar irradiance distribution on a PV source. An MPPT algorithm that is able to optimize the source instantaneous operating power under nonuniform irradiance is proposed. The ability of the algorithm and its increased performance with respect to traditional algorithms are evaluated by means of experimental tests performed on a real PV power system.

Experimental Performance of MPPT Algorithm for Photovoltaic Sources Subject to Inhomogeneous Insolation

In this paper the effects of temperature on partial discharge (PD) activity taking place inside a spherical void in epoxy resin system are studied. Indeed, some experimental tests previously performed on specimens, having different void shapes, under multi-stress condition of temperature and voltage, have shown very different PD amplitude distributions at temperatures higher than ambient. However, this phenomenon cannot be explained only by taking into account the different thermobaric conditions of the enclosed gas. In consequence of the general physical inaccessibility of such voids, a study is here performed using a numerical model based on an evolutionary optimization algorithm. This is used to evaluate the range values for the physical parameters of the insulating system influencing the observed changes in PD activity. Finally, comments are presented about the adopted criteria by which the comparison between the experimental data and the simulated ones is performed, and about the interpretation of the dependence on temperature of the experimental PD.

On PD mechanisms at high temperature in voids included in an epoxy resin

In this paper, the research of the optimal layout of photovoltaic (PV) modules in a PV array giving the maximum output power under different shaded working conditions is carried out. The particular condition of non uniform solar exposition of the modules is analyzed. The study of the different configurations has been carried out starting from a circuital model used for the design of PV cells and for the simulation of the working behavior of PV arrays. The attained results appear to be interesting although the complexity of the problem in mathematical terms is huge when the number of panels is high. Moreover, the results confirm that this approach often allows to attain a higher electrical energy production compared to that attainable with PV arrays with a static layout.

Reconfiguration Techniques of Partial Shaded PV Systems for the Maximization of Electrical Energy Production

This work presents a preliminary study on the implementation of a new system for power output maximization of photovoltaic generators under non-homogeneous conditions. The study evaluates the performance of an efficient switching matrix and the relevant automatic reconfiguration control algorithms. The switching matrix is installed between the PV generator and the inverter, allowing a large number of possible module configurations. PV generator, switching matrix and the intelligent controller have been simulated in Simulink. The proposed reconfiguration system improved the energy extracted by the PV generator under non-uniform solar irradiation conditions. Short calculation times of the proposed control algorithms allow its use in real time applications even where a higher number of PV modules is required.

Optimization of photovoltaic energy production through an efficient switching matrix

The continuing development of HVDC power transmission systems presents many problems related to evaluation of the reliability of power system assets [1]-[5]. In this context the identification of insulation defects plays a key role in preventing unexpected failures of electrical components. Partial discharge (PD) measurement is a useful approach to assessing the condition of HV power apparatus and cables. Such measurements are also widely employed for HVAC systems. The inception mechanisms of PD in AC systems are well-known, and measurements are usually performed following the IEC 60270 standard [6]. PD measurements under DC voltage present complexities related to the nature of the phenomenon and the supply conditions [7]. In AC systems phase-resolved-partial-discharge (PRPD) patterns allow assessment of the insulation condition, and provide information on the types of defect present [8]. Such analysis cannot be performed under DC voltage, since each discharge event cannot be related to a phase value. The interpretation of the acquired data therefore requires a different approach.

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A new approach to partial discharge detection under DC voltage

A partial discharge detection device for detecting and measuring partial discharges in electric systems or components, which delivers signals having a form much resembling that of the radiated pulse, for improved identification and analysis. The device is of small size, totally insulated and self-powered, and allows measurements to be performed with the highest safety with no need for direct connection, thereby allowing operators to stand at a distance and avoid any system shutdown while making measurements. Furthermore, it can also detect and deliver the sync signal, which is obtained by picking up the supply voltage of the discharge generating components.

Roberto Candela

Papers

On PD mechanisms at high temperature in voids included in an epoxy resin

Reconfiguration Techniques of Partial Shaded PV Systems for the Maximization of Electrical Energy Production

Optimization of photovoltaic energy production through an efficient switching matrix

A new approach to partial discharge detection under DC voltage

Portable partial discharge detection device