Lyapunov-based control for single-phase three-level NPC AC/DC voltage-source converters

The mathematical model of single-phase three-level neutral-point-clamped (NPC) voltage-source converter using switching functions is founded and a space vector PWM (SVPWM) algorithm is proposed for the single-phase three-level NPC converter. In order to lower the switching loss and avoid the abrupt change of output voltage vectors, an optimal SVPWM algorithm is proposed. The strategy of changing the voltage adjusting coefficient to adjust the effective time of the positive and the negative small vectors to control the neutral point potential balance is proposed. A new control method based on the Lyapunov´s direct method is designed for the single-phase three-level NPC converter. Simulation results show that the converter can be stabilized globally and the whole system exhibits excellent transient response, near unit power factor under the perturbation of large load disturbance.