New scheme of SHE-PWM technique for cascaded multilevel inverters with regulation of DC voltage sources.

In this paper the Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) technique with considering controllable DC link voltages is implemented in the cascaded multilevel inverter. The novelty of this work is the method of mathematical modelling of SHE-PWM with respect to variable voltage of DC links. With respect to variable voltage of DC links, the number of degrees of freedom are increased compared to ordinary SHE techniques with constant voltage of DC links. One of the issues in SHE-PWM technique is solution of nonlinear equations under various operating conditions of the converter. In the proposed formulation, the resulted nonlinear equations are solved only one time for entire reachable range of output voltage amplitude, which leads to considerable reduction of computational burden. Also, the THD of output voltage waveform remains constant at minimum value for different operating points. The theoretical results of proposed technique are verified by the simulation and scale-down experimental setup of a cascaded 7-level inverter. [ABSTRACT FROM AUTHOR]