Controller Design Using Ant Colony Algorithm for a Non-inverting Buck–Boost Chopper Based on a Detailed Average Model

In this article, the non-inverting buck–boost converter and its operation modes are scrutinized. The closed-loop stability of the converter in buck and boost modes is analyzed, and the necessity of using an appropriated controller is demonstrated. Then the application of an adapted ant colony optimization to design a feedback controller is proposed, and a controller based on its existing model is tuned. Simulation and experimental results obtained from the ant colony optimization designed controller are then compared with a controller designed with the classic method. Although the simulation and experimental results prove the efficiency of the proposed control approach, a significant difference between controller behavior in practice and simulation is obvious. Finding these differences, more detailed models, including all parasitic elements, in the buck and boost modes are derived. Applying the proposed model in controller design illustrates that the desired performance of the converter can be guaranteed with a simple proportional-integral (PI) controller. The suggested ant colony-based controller is again tuned based on the more detailed model, which improves the performance of the converter system even more. Furthermore, good agreement between analytical and experimental outputs validates the accuracy of the modeling and simulation.     

Comparison Between Discrete Magnetic Coils and Multipole Coils for Measurement of Plasma Displacement in IR-T1 Tokamak

We have expressed two different methods to determine the plasma positions in the IR-T1 tokamak. An array of magnetic probes are placed polidally outside the chamber surface and their signals are plugged in the displacement equation and horizontal displacement of plasma column is obtained. The results of this measurement are compared with the experimental data obtained from sensors of multipole moment. It was detected a fluctuation in plasma displacement obtained with discrete magnetic coils, so the method of multiple moments is better than the discrete magnetic coils for the determination plasma displacement that used for feed back control.     

Influence of morphology on the behaviour of electrodes in a proton-conducting Solid Oxide Fuel Cell

SrCe_0.95Yb_0.05O₃ (SCY) and related materials are under consideration as a proton conductors for Solid Oxide Fuel Cell (SOFC) electrolytes. Sintered pellets of SCY are used to perform impedance spectroscopy (IS) studies and fuel cell tests on cells with Pt electrodes of two different morphologies. Electrodes are applied to the SCY pellets by two routes: either by firing on a layer of Pt paint (denoted electrode P) or by magnetron sputtering (electrode S). In impedance spectra recorded over a wide temperature range under humidified hydrogen, in symmetrical cell conditions, cells with S electrodes give rise to a much smaller low frequency impedance feature than the cells with P electrodes. This is tentatively attributed to faster diffusion-related processes taking place at the S electrodes. The behaviour of working fuel cells with S and P electrode morphologies is evaluated in terms of maximum power output and Area Specific Resistance in two-atmosphere tests. The fuel cell anode with the S morphology results in superior fuel cell performance, in agreement with the impedance study. The influence of the two different electrode morphologies on the behaviour of the cells is discussed with reference to their morphology, as determined by SEM and AFM.     

Investigation of Tokamak Plasma MHD Activity Using FFT Analysis of Mirnov Coils Oscillations

A tokamak plasma mode was analyzed using the Fast Fourier Transform (FFT). Fourier analysis is reliable technique for mode detection in tokamaks. For this purpose, we used a poloidal array of Mirnov coils. After Fourier analysis on Mirnov coils data, Power Spectral Density (PSD) diagram was plotted. PSD describes how the power of a signal is distributed with frequency. In this contribution we also determined edge safety factor and safety factor from Fourier based derived mode numbers q = m/n. We obtained the maximum MHD activity using power spectrum in the frequency of 33 kHz. Also the edge safety factor determined small than 3, and the values of obtained safety factor from the mode numbers are between 2 ≤ q ≤ 5.     

Demonstration of Shafranov Shift by the Simplest Grad–Shafranov Equation Solution in IR-T1 Tokamak

There are analytically different solutions for the inhomogeneous Grad–Shafranov equation (GSE). We presented one of methods of analytical solution to the GSE corresponds to source function linear in ψ. This solution is over constrained both in shape and in plasma current. We demonstrated that Shafranov shift for this solution is independent of plasma current.     

Erratum to: Biasing Effect on Modifying of the Tokamak Plasma Horizontal Displacement

In this contribution we presented the first biasing experiments performed on the IR-T1 tokamak. For this purpose, a movable biasing system was designed, constructed, and installed, and then the positive voltage applied to an electrode inserted inside the tokamak limiter and the plasma current and also the plasma horizontal displacement in the absence and presence of the biased electrode based on the multipole moments and magnetic probes techniques were measured. Measurements result has shown a modification of plasma confinement by decreasing the plasma displacement.     

Determination of the Plasma Internal Inductance and Evaluation of its Effects on Plasma Horizontal Displacement in IR-T1 Tokamak

We analyzed dynamic equilibrium properties of a large aspect ratio and low Beta tokamaks, in particular deriving a modified relation for the Shafranov shift in the presence of poloidal flow and external vertical field, and demonstrate it experimentally on the IR-T1 tokamak. Poloidal flow can produce modifications in the equilibrium properties. By increasing Alfvenic Mach number from zero, flow produce outward force, and plasma shifted in outward direction. If the poloidal Alfvenic Mach number equal to one, singularity will observe in the solution of generalized Grad–Shafranov equation. Also inversion of Shafranov shift in the transition of flow speed between sub-Alfvenic to super-Alfvenic speeds can be observed due to inward force produced by flow.