Single-stage three-phase current-source inverter for photovoltaic grid-connected system

A single-stage three-phase current source inverter (CSI) using in photovoltaic grid-connected (PVGC) system is investigated. A dynamic predictive optimal control (DPOC) strategy for grid current is presented. In this method, based on a predictive model of grid current and real-time dynamic optimization cost function, an optimal control action for the next sampling interval is achieved in advance. In addition, a perturbing resistance maximum power point tracking (PR-MPPT) algorithm is proposed for the CSI PVGC system. The algorithm is implemented by perturbing resistance instead of perturbing current or voltage in conventional perturbation and observation (P&O) MPPT method. The PR-MPPT algorithm can solve the issues of current instability and power dropping instantly at the right side of maximum power point (MPP) of P-I curves in CSI PVGC system. With the proposed methods, the CSI PVGC system achieves the features of simple circuit, good stability and fast dynamic response and MPPT function. Experimental results validate the feasibility of the proposed work.