A straightforward close-loop control strategy for a single-phase asymmetrical flying capacitor multilevel inverter

This paper focuses on the development of a close-loop control strategy for a single-phase asymmetrical flying capacitor multilevel inverter (AFCMLI). The proposed system has many notable advantages compared to the conventional open-loop PWM controls which are widely used. Since in this method, power section is embedded in control loop, the detrimental effect of deregulation of flying capacitor voltages and system non-linearity on quality of generated waveform is reduced considerably. Furthermore, not only is it simpler and more facile than PWM methods because of omitting complicated PWM generating procedure, but also prevents minimum pulse width problem which commonly occurs in PWM methods. Main advantage of proposed strategy is its ability to balance capacitor voltages in a simple way without requiring lookup table, which make this method very interesting especially in high level inverters. The performance of proposed method is confirmed by a simulation using PSCAD/EMTDC^® and a practically implemented low power 9-level AFCMLI.