Modified DC-Bus Voltage-Balancing Algorithm Based Three-Level Neutral-Point-Clamped IPMSM Drive for Electric Vehicle Applications

A modified dc-link voltage-balancing scheme for a three-level neutral-point-clamped inverter with an interior permanent magnet synchronous machine is presented with a wider range of machine operation including field weakening. It uses two dc-link voltage sensors to take care of the voltage differences and keeps it to a required tolerance level. A switching control strategy is developed using a space vector pulsewidth modulation scheme. The number of vectors per switching cycle is optimized to five, and changes in the control strategy depending on the two capacitor voltage differences are only allowed to take place at the start of each switching cycle. This helps in reducing the switching losses. A detailed analysis on the larger capacitor voltage deviation at high modulation index and leading power factor is analyzed, and four control strategies are developed to reduce it. Simulation studies are carried out in MATLAB/Simulink platform, and an experimental setup is developed using a DSpace®-based real-time emulator. Simulation and experimental results show the effectiveness of the proposed system.