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For a fully digital control of PWM converters, considerable research has been done based on the predictive current control (PCC) scheme. However, it requires a large amount of calculation in the step of experimental implementation. Besides, when compared with the classical linear control scheme, the sampling interval of the PCC scheme must be shorter to obtain the same control performance for current. Due to this, a digital signal processor with excellent performance is required. This paper proposes an improved simplified model PCC scheme for three-phase PWM converters. The main objective is to simplify the PCC scheme. Also, the proposed control scheme is able to reduce the calculation time without affecting the performance. Simulations and experiments are carried out to investigate the presented novel predictive current control scheme. The results indicate that the three-phase PWM converter has excellent static and dynamic performance with the proposed scheme. Besides, the calculation time can be obviously shortened.

The high frequency asymptotic formulas for the acoustic impedance modal coefficients of a clamped circular plate located at the boundary of the three-wall corner region have been obtained. The method of contour integral analysis, the series for the Bessel and Neumann functions and the stationary phase method have been used. Some sample modal coefficients of the acoustic resistance and reactance together with the absolute approximation error have been illustrated as the functions of a parameter proportional to the vibration frequency. The computational efficiency of the presented asymptotic formulas has been compared with the computational efficiency of the integral formulas. The cases, in which the asymptotic formulas allow to reduce the calculation time in comparison with the integral formulas, have been determined. The presented formulas can be used to decrease the computation time of the acoustics power radiated by a clamped circular plate located at the boundary of the three-wall corner region. Moreover, the sound pressure calculations can be performed much faster by using these formulas when the acoustic attenuation is included.

The sound radiation inside an acoustic canyon has been analyzed for a surface sound source located at the bottom. Based on rigorous mathematical manipulations, the formulas of a high computational efficiency describing the sound pressure and sound power have been obtained. They can be easily adapted to describe the sound radiation of an arbitrary system of sound sources. As an example of their application, the sound radiation of a piston has been investigated. The asymptotic formulas of the sound power modal coefficients have been obtained. They can be used to significantly improve the numerical calculation of the sound power.