DC voltage sensorless control strategy of grid-tied two-stage three-phase photovoltaic system

The variable dc voltage generated by photovoltaic (PV) array can be harnessed as much as possible through the well-known two-stage inversion in grid tied configuration, where the controlled dc-link voltage can be maintained stably to ensure the desired low harmonic ac output. Traditionally, the front-end dc Boost converter generally operates to track the maximum power point (MPP) of PV array by directly measuring the input current and voltage, meanwhile the rear-end inverter is controlled to generate sinusoidal output current and keep dc-link voltage unchanged. The PV voltage and dc-link voltage are measured to assist the accurate control of whole PV generation system. This paper proposes a novel control strategy to eliminate both dc voltage sensors assumed in traditional two-stage grid-tied PV system while not downgrade the system performance with regard to the MPPT accuracy and ac output quality. Matlab simulations verified the proposed control strategy with captured waveforms to illustrate its performance.