A Space Vector based Pulse Density Modulation Scheme with Reduced Computational Complexity

摘要

Space vector based pulse density modulation (SVPDM) scheme exhibits variable switching frequency resulting in broad and continuous frequency spectrum. The spectral spreading results in harmonic performance improvement and decline of motor acoustic noise. A space vector based pulse density modulation scheme with reduced computational complexity for multilevel inverters is presented in this paper. Reduced computational complexity is achieved in such a way that the entire computation process takes place in 120° coordinate system itself without requiring the conversion to 60° or 90° systems. The scheme makes use of the concepts of sigma delta modulation and vector quantization for generating the output switching vectors for inverters. In the proposed scheme, nearest three vectors enclosing the reference vector is identified by comparing the instantaneous values of three phase reference signals. Out of the three surrounding vectors, the vector with minimum Euclidean distance is selected as the output switching vector. Simulation as well as experimental results are utilized for validating the scheme.