This paper describes the topological structure and working principle of the alternate-arm muhilevel converter （ AAMC }. As compared with conventional MMC, it offers some attractive features such as fewer modules~ no loop current, DC blocking capacity and no additional switching loss, so that it has a good prospect for further development. However, in AAMC, it is more difficult to solve the problem of voltage balance among capacitors. Voltage balancing is finally realized in the overlap current method by using bridge arm inductors to change the conducting time of the arms and adopting an additional control strategy. An AAMC topological model with 14 modules in each arm is established on the PSCAD/EMTDC platform, and simulation results verify the effectiveness of the overlap current approach.
alternate-arm multilevel converter
capacitor voltage balance
overlap current~ bridge arm inductor