An improved MPPT arithmetic and grid-connected control strategy for single-stage three-phase PV converter with LCL filter

This paper theoretically analyzed and established the state-space mathematical model of the single-stage three-phase PV converter with LCL filter, and proposed a design procedure of the pole-assignment control method based on state feedback and repetitive controller of current regulation. Additionally, the MPPT is realized by using improved P&O method with adaptive step algorithm, furthermore constant voltage tracking can be used in the MPPT startup. The adaptive step algorithm is realized according to the variety-rate of the DC bus voltage. At the same time the DC bus voltage floor level protection is adopted in case of the value of DC bus voltage is under the peak value of the grid line-voltage. This improvement aimed at stability of DC bus voltage when the solar irradiance bated suddenly. Finally the correctness and availability of this method are proved by the simulation and experiments.