Abstract-Finite State Model Predictive Control (FS-MPC) has emerged as a promising control tool for power converters and drives. One of the major advantages is the possibility to control several system variables with a single control law, by including them with appropriate weighting factors. However, at the present state of the art, these coefficients are determined empirically. There is no analytical or numerical method proposed yet to obtain an optimal solution. In addition, the empirical method is not always straightforward, and no procedures have been reported. This paper presents a first approach to a set of guidelines that reduce the uncertainty of this process. First a classification of different types of cost functions and weighting factors is presented. Then the different steps of the empirical process are explained. Finally, results for several power converters and drives applications are presented, which show the effectiveness of the proposed guidelines to reach appropriate weighting factors.
This paper presents a new low switching frequency modulation technique for multilevel power converters. The proposed algorithm is based on model predictive control and uses the sliding discrete fourier transform to calculate harmonic components in real time in order to eliminate undesired harmonics at the output voltage. In this way the cost function of the predictive control can achieve similar results to traditional selective harmonic elimination, but without the need of off-line calculations and interpolation tables. The algorithm is executed online in real time, improving the dynamic performance of the system. In addition, no predefined switching patterns need to be designed, making the generalization for multilevel converters an easy task even for any modulation index or converters with different number of levels. Simulations results for three and seven level inverters are presented.
<p class="AMSmaintext1">The HP40-Nb heat resistant alloy (35Ni-25Cr-Nb) was analysed by means of optical microscopy after aging treatments at 1073 and 1173 K for different times, in order to apply the classic Johnson – Mehl - Avrami – Kolmogorov kinetic model (JMAK), and thus calculate the activation energy of secondary M<sub>23</sub>C<sub>6 </sub>precipitation, which occurs during thermal aging. The relevance of this theoretical analysis is to infer the mechanism that controls the nucleation and growth of M<sub>23</sub>C<sub>6</sub> secondary carbides, since the amount and morphology of these phase influences the mechanical properties as well as the corrosion resistance in service. After performing the kinetic analysis using the JMAK model, the activation energy was found to be 208 kJ/mol, which would indicate that the secondary precipitation in this alloy is controlled by the Cr-diffusion phenomenon along the austenitic matrix.</p>
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