Harmonic Spectrum Analysis of the Output Voltage and Grid-Side Filter Design for Three-Level Voltage-Source Converters

Because of the complex arithmetic computation of the traditional three-level space vector modulation (SVM), its hardware implementation is difficult to achieve. Moreover, the normal approach of acquiring the output voltage harmonic is sensitive to the simulation step, measurement accuracy, system noise, etc. This paper proposes a new method for analyzing the voltage harmonic spectrum of the three-level converter. Furthermore, the minimum value of the inductance of the grid-side filters is designed on this basis. First, the formulas of the duty cycle and the modulation waveform of the three-level SVM algorithm are easily derived using some simple linear calculations under the 120 degrees coordinate. Then, considering the characteristics of the digital circuits, the harmonic components of the output voltage are calculated using Fourier analysis. Third, a precise analytical design of the minimum inductance value of grid-connected converters with LCL and L input filters is presented. Finally, the validity of this approach is verified by using experimental results. (C) 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.