Three phase photovoltaic grid-connected generation technology with MPPT function and voltage control

Three phase photovoltaic grid-connected generation technology with maximum power point tracking (MPPT) and voltage control function is proposed in this paper. According to the equivalent circuit of the photovoltaic (PV) array, it builds the mathematic model of PV array. Based on the V-I characteristic curve, it calculates the MPPT of PV array in grid-connected system by using the Newton´s method. By the structure of the three phase photovoltaic grid-connected system, it establishes the dual-loop feedback control strategy. The voltage loop is considered as the external loop, and the grid-connected current loop as the internal loop. Based on the transformation of dqo coordinates, the grid-connected current is decoupled into active current and reactive current. The DC voltage control from the MPPT reference is used to adjust the active current, however, the AC voltage control from the system voltage is used to dominate the reactive current. It carries out the MPPT and voltage control function of the grid-connected generation. At last, the three phase photovoltaic grid-connected generation system is injected to distribution system. The control strategy with MPPT and voltage function is implemented with the example system, and the simulation is accomplished successfully. The simulation results verify that the proposed models of the three grid-connected phase photovoltaic system and the control strategy are valid and correct.