Current Issue : October-December Volume : 2022 Issue Number : 4 Articles : 5 Articles
The generation of 1/f noise is closely related to the quality defects of IGBT devices. In the process of detecting single-tube noise of IGBT, thermal noise and shot noise show obvious white noise characteristics in the low-frequency range. This paper investigates how to accurately detect the 1/f noise under strong white noise, and thus proposes a particle swarm optimization method known as variational mode decomposition. First, the particle swarm optimization algorithm was used twice to search the optimal parameter combination between the penalty parameter and the decomposition modulus of the VMD model. Then, the parameters of the variational mode decomposition algorithm were set in optimal parameter combination. The frequency center and bandwidth of each IMF component were determined by continuous iteration in the variational framework. Finally, the 1/f noise signal was adaptively separated from background noise. Extensive experimental investigations carried out under different signal-to-noise ratios, compared with the optimal wavelet denoising algorithm, revealed that the PSO-VMD algorithm improved the signal-to-noise ratio by 6.6%, 16.82%, and 42.48%, whereas the mean square error is reduced by 7.12%, 19.80%, and 33.76%....
In view of the high-quality requirements of the power supply quality of the user-side sensitive equipment, the system for voltage sag in the grid operation is stable and efficient. This paper proposes a new virtual voltage comparison compensation dynamic voltage recovery method. The algorithm that uses the invariant constant signal as the input quantity, and the real-side input load side signal reduces the influence of the input quantity uncertainty change on the generated compensation signal and improves the simplicity of the system operation control and the system stability. The flexibility of the proposed control strategy, as well as the effectiveness of the optimal design method, is verified by both simulation and experimental results....
The article presents the results of tests related to failure analysis and finding ways to diagnose used semiconductor elements, among others, in power electronics converter systems on vessels and offshore facilities (drilling and production rigs and wind turbines). Diagnostic relationships were found between the temperature change in the above systems and the signals generated in the form of elastic waves of acoustic emission. The authors confirmed the influence of the transistor’s working temperature on its amplitude-frequency spectrum of acoustic emission signals emitted. The range of ‘safe temperatures’ was considered which means temperatures that do not directly affect the damage of the component....
This paper treats a parallel 12-pulse rectifier as the study subject. The influence of unbalanced terminal voltage, the triggering angle, as well as the commutation angle of a thyristor-controlled rectifier circuit are considered in switching functions. Then, a frequency-domain harmonic coupled admittance matrix under the effect of positive sequence and negative sequence voltages are proposed, respectively. With the integration of the above matrices, a harmonic coupled admittance matrix model of a parallel 12-pulse rectifier under unbalanced voltage is proposed. On this basis, a simplified harmonic model of a 12-pulse rectifier is established, which only considers the effect of major elements through analyzing the elements’ distribution and magnitude of the harmonic coupled admittance matrix, as well as the AC current harmonic producing mechanism. All the models proposed in this paper are verified with high accuracy through simulation in MATLAB/Simulink. The models proposed in this paper can be used to guide the selection of harmonic suppression measures and equipment....
This paper presents a Python-based simulation technique that can be used to predict the behavior of switch-mode non-isolated (SMNI) DC-DC converters operating in closed loop. The proposed technique can be implemented in an open-source numerical computation software, such as Scilab, Octave or Python, which makes it versatile and portable. The software that will be used to implement the proposed technique is Python, since it is an open-source programming language, unlike MATLAB, which is one of most-used programming and numeric computing platforms to simulate this type of system. The proposed technique requires the discretization of the equations that govern the open-loop operation of the converter, as well as the discretization of the transfer function of the controller. To simplify the implementation of the simulation technique, the code must be subdivided into different modules, which together form a package. The converter under analysis will be a buck converter operating in CCM. The proposed technique can be extended to any other SMNI DC-DC converter. The validation of the proposed technique will be carried out by comparing it with the results obtained in LTspice....
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