A novel CHB multilevel converter for PMSM drives with energy feedback system

Cascaded H-bridge (CHB) multilevel converter has been conceived as an effective device to reduce total harmonic distortion (THD) in medium-voltage motor drives. Although this advantage makes it useful for wide electric applications, the energy flow has worked in open-loop model. In the process of transmission, energy was not used to enhance the control performance of the whole system. This paper presents a solution to solve the problem through the addition of an energy feedback transformer in series with the converter and the motor; whereby the whole permanent magnet synchronous motor can work in energy closed-loop model, and if the control is adjusted to work at particular switching points, the energy flow would improve the system efficiency. Therefore the high frequency transformer design is the key of this system. This work shows some simulations and experiments on this concept.