Study on Modulation Strategies for Hybrid 15-Level Converter Based Electric Vehicle Energy Storage

The multi-level cascade converter is composed of H-bridge module in series. An improved 15-level hybrid cascade converter based on DC energy storage of electric vehicle can be obtained by changing the ratio of DC energy storage to supply voltage from 1:1:1 to 4:2:1 of the traditional cascaded 7-level converter cascaded by three H-bridge modules. In this paper, the modulation strategy of the 15 level hybrid cascade converter is studied, and a new algorithm for the switching angle of the multilevel converter powered by DC energy storage device for electric vehicle is proposed. Based on Saber simulation software, three different modulation strategies, stepped-wave modulation, PWM and partial PWM, are applied to verify and compare. Finally, the simulation results of total harmonic distortion, low-order harmonic component and switching loss of the converter based on the output voltage without any filter are compared, and the related modulation strategies are discussed.