Predictive DC voltage control of single-phase PV inverters with small DC link capacitance

This paper proposes a novel control method for DC voltage in single-phase voltage-source inverters fed by constant-current or constant-power sources. The technique predicts the inverter power require to correct a DC voltage error within one fundamental AC cycle. This is based on the power balance between DC input and AC output, and the energy stored in the DC link capacitor. The fast response means a smaller capacitor can be used, and operation with a large double-line-frequency ripple on the DC bus is possible without causing distortion of the AC output current. This scheme is suitable for applications where substantial DC link buffer energy is unnecessary, e.g.: grid-connected photovoltaic generators. The reliability and lifetime of the inverter can be significantly improved if a non-electrolytic type capacitor is used. Experimental results are presented that verify the inverter operation.