Predictive control of an H-NPC converter for single-phase rooftop photovoltaic systems

This paper presents the predictive control of the H-NPC converter for single-phase grid-connected photovoltaic (PV) applications. This topology has been commercialized by one major manufacturer for small-scale rooftop PV applications, up to 8 kW, with classic PI control and an adapted carrier based PWM modulation. The proposed control scheme allows the dc-Link voltage control and the balance of the dc-link capacitors. Low ripple currents and a near unity power factor are achieved. The use of predictive control has been further exploited by adding control of the average device switching frequency, and a switching loss reduction mechanism. Other additions to the predictive control scheme allow the control of the common-mode voltage to eliminate possible leakage currents due to parasitic capacitance of the PV modules. The proposed control scheme is validated trough simulation results and tested under dynamic conditions.