Four-level hybrid-clamped (4L-HC) converters are promising candidates in high-power medium-voltage applications. To ensure a low switching loss for 4L-HC converters operated in high power scenarios, the selective harmonic elimination pulse width modulation (SHE-PWM) is adopted, which has good harmonic performance with a low switching frequency. The unified SHE-PWM formulation is used in obtaining the four-level switching patterns and switching angles to achieve the optimal output waveform quality. In addition, to ensure the balanced voltages across the DC-link capacitors and flying capacitors in 4L-HC converters, the model predictive control (MPC) is used in selecting the redundant switching states based on the output voltage level signal from the SHE-PWM module, while regulating the switching frequency at the same time. Various steady-state and dynamic simulation results are provided to validate the effectiveness of the proposed SHE-MPC method for 4L-HC converters.

Multilevel converters;capacitor balance;selective harmonic elimination