Spectral analysis of SPWM controlled cascaded three-level inverter drive

Abstract

Cascaded retrofit of two two-level inverters can generate three-level voltage space vector. This paper proposes the use of double Fourier integral analysis based on unit cell approach that exists for two-level inverter in order to carry out the spectral analysis of the cascaded three-level inverter. The unit cells with their contours and the corresponding boundaries are carefully identified for the cascaded three-level inverter and analytical expressions are presented for the harmonic components present in the inverter output voltage. The effectiveness of the proposed spectral analysis is demonstrated first using MATLAB simulations and validated experimentally using a laboratory prototype.