Study of Optimized SVPWM for Nine-Switch Inverter of Bearingless Motor Based on Reducing Switching Losses

The nine-switch inverter (NSI) can simultaneously control two three-phase loads, applying a NSI to a bearingless motor system can reduce the number of transistors, complexity, and cost of the bearingless motor system. This paper focuses on the consequent pole-bearingless permanent magnet motor and improves the conventional SVPWM method of the NSI. It is no longer limited to only considering the order of action of the voltage vector but reduces the number of switches generated by selecting the voltage vector. To further reduce the number of switching times, after analyzing the number of switching times for various sectors using different combinations of voltage vectors, an SVPWM control method with the minimum number of switching times is proposed. To verify the feasibility and correctness of the proposed method, simulation analysis was conducted under different operating conditions, and experimental verification was conducted. The results showed that the proposed method in this paper achieved the expected goals.