The invention relates to a two-stage three-phase photovoltaic grid-connected
system without a direct-current (DC)
voltage sensor and a control method of the
system. The
system comprises a photovoltaic (PV)
cell array, a Boost circuit, an
inverter circuit, a
maximum power point tracking (MPPT) controller and an
inverter controller, wherein the output end of the PV
cell array is only provided with a
current sensor. For the MPPT control in a method, a DC sensor is utilized to measure PV current; based on the correspondence of the PV
voltage and the duty ratio d in the Boost circuit, d is used for calculating and controlling the PV
cell array to work at a maximum power point (MPP) position; for the
inverter control, based on the correspondence of the
DC link voltage and the modulating
signal amplitude, modulating
signal amplitudes is utilized to predict a
DC link voltage value in real time, and a DC link normalization coefficient is introduced so as to provide a grid-connected current reference amplitude ixref with maximum power (Pmax) after being subjected to three-phase even allocation; after being amplified by a follow-up proportional-integral (PI) controlling unit, the reference amplitude ixref is compared with a triangle
carrier signal to output a pulse-width modulation (PWM)
signal so as to control the switching-on / off of the inverter circuit, thus ensuring that actually output current ix can closely follows the current reference amplitude ixref, and the frequency and
phase angle of the actually output current ix are identical to the frequency and
phase angle of
power grid voltage at a grid-connected position. According to the invention, the volume of the system can be reduced effectively, the construction cost can be reduced, and the reliability of the system can beimproved.