State-Space based Current-Sensorless Finite Control Set - Modulated Model Predictive Control for a 5L-Flying Capacitor Multilevel Converter

In this paper, a sensorless constant switching frequency finite control set modulated model predictive controller (FCS-M2PC) is proposed for a single phase 5L flying capacitor multilevel converter (FCMC). The converter is designed to operate in voltage-control mode for a UPS application with an output LC filter. Current-sensorless operation is achieved through the implementation of a full order state-space observer. The state-space model is also used for two-step ahead prediction of filter capacitor voltage which is used as a reference to the Phase Shifted PWM (PSPWM) modulator. The use of PSPWM modulator guarantees balancing of the flying capacitors (FC’s) inherently thus removing the need for additional sensors required to measure FC’s voltages. The proposed method provides fast load dynamic response, robustness against parameter variation with minimal sensor requirements. Performance of the proposed scheme is verified by experimental results.