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Phase-shift control is a common approach to voltage control of traditional H-bridge inverters, but this method has not been used to voltage control of H-bridge Z-source inverter (ZSI) so far. This study proposes a new phase-shift control method for H-bridge ZSI, which its main difference with phase-shift control of traditional H-bridge inverters is existence of four shoot-through states (short circuit of the H-bridge) in each switching cycle. One of the advantages of the proposed method is simultaneous elimination of several harmonics by choosing the appropriate switching angles. Moreover, by using this phase-shift control method, the amplitude of low-order harmonics for many values of switching angles is less than the amplitude of low-order harmonics in traditional H-bridge voltage source inverter (VSI). Total harmonic distortion and distortion factor, as two important indexes for quantifying the merits of the proposed method, are calculated and compared with their values in traditional H-bridge VSI. A detailed description of suggested method and comparison with the traditional method are presented in this study. Simulation and experimental results are also given to demonstrate the new features of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a harmonic elimination technique for online reducing harmonics in voltage source inverters. In the presented method, in order to provide required fundamental voltage and eliminate specified harmonics simultaneously, the value of the switching angles are determined using a new efficient optimization algorithm named Enhanced Teaching-learning-based Optimization (ETLBO). The efficiency of the presented strategy is validated on three-phase seven-level diode-clamped inverter while other structures of multi-level inverters (MLIs) can be employed. The aim is to reduce the Total Harmonic Distortion (THD) in multilevel converter. In this paper, a new optimization algorithm named ETLBO has been successfully implemented to achieve optimal switching angles in order to harmonic elimination in MLIs. A three-phase seven-level diode-clamped MLI has been selected as a test case to validate the effectiveness of the proposed method. The simulation results demonstrated the ETLBO method not only is in preference to the Genetic Algorithm and Particle Swarm Optimization for including no user-defined parameter and simple implementation, but also for providing higher quality solutions. Moreover, in order to verify the superiority of the ETLBO algorithm over conventional methods for harmonic elimination, the Newton-Raphson (NR) method was implemented to find optimal switching angles. The results obtained by the NR method compared with those of the ETLBO and the superiority of the ETLBO in terms of the both computational time and the resulted %THD was concluded. As a whole, the results show that the ETLBO algorithm is expected to become widespread in power systems where on-line updating harmonics is needed since it provide accurate and high-quality solution in extremely short time. [ABSTRACT FROM AUTHOR]