Abstract: In order to solve the problem of fewer output levels existing in the positive and negative re-laminated H-bridge under the strategy of positive and negative reverse laminated velocity pulse width (POD-PWM) modulation, a new Topology with two-single-level co-level is proposed, as well as an improved POD-PWM double frequency modulation strategy. In order to eliminate the imbalance problem of power between the two units, the method of switching two-unit switch tube driving signals is adopted using a 1/2 output voltage cycle based on the improved POD-PWM frequency doubling modulation strategy. From the simulation and experimental study, the accuracy and practicality of the above theoretical analysis are proven.

Key words: five open-level H bridges, multi-level inverters, improved modulation strategies, total harmonic distortion, power balance