An analytical algorithm for Selective Harmonic Elimination and efficient control in five-level inverters

Traditional methods, such as Modulating-Functios, Space-Vectors and Feedback Methods present the disadvantage of high residual harmonics. Selective Harmonic Elimination (SHE) generates trains of pulses such as the fundamental component of the resulting waveform has a specified frequency and amplitude while selected order harmonics are eliminated. To achieve this goal, a set of nonlinear equations must be solved. SHE offers many distinctive features including high quality of the output waveform, low switching frequency at fundamental frequency ratios, possibility to select the harmonics to be deleted and the ability to leave triplen harmonics uncontrolled. On the other side, the main drawbacks of SHE methods are their computational burden and the subsequent need of complicated hardware. This paper proposes a new analytical algorithm for SHE in a 5-level cascaded inverter. The proposed method transforms the trascendental system in a polinomial one resulting that analytical solution can be easy obtained using a typical Digital Signal Controller. The achievable results are demonstrated by both simulation and experimental results.