Research On PV Grid-connected Inverter Control Strategy And MPPT Technology

In recent years,Photovoltaic(PV) becomes more and more attention as a new form of energy generation. It protects the environment and saves energy. Photovoltaic grid-connected is an important form of utilization of solar energy. Currently it has a good development prospect. In PV grid-connected system, inverter is the most important, its performance determines the efficiency of various aspects of the system. So far, there have been a lot of research and applications on PV grid-connected inverter at home and abroad. But some problems have not been solved. In this paper, it makes a deep research about the problems.This paper analyzes several conventional Photovoltaic Maximum Power Point Tracking(MPPT) algorithms. Then, aiming at the common problems on oscillation and misjudgment it proposes a new MPPT algorithm—Based on the power prediction variable step P&O method. Building the model in the PSIM and comparing to track the performance of the new MPPT algorithm and the conventional to verify the accuracy theory of the new algorithm.Grid-connected inverter is the core section of the PV grid-connected system, so the selection of its topology and control strategy is very important. The inverter topology is three-level neutral-point-clamped(NPC) and its control strategy is PQ control. This paper analyses work process of the topology and the control strategy in detail. Then it established the mathematical model of three-phase inverter under different coordinate system basing on NPC topology and adopts the control method of combining the PI control and SPWM modulation techniques. Establishing a three-phase photovoltaic grid-connected inverter simulation model and setting up reasonable experimental parameters for experimental analysis and testing. The results show that it is correct and effective on the structure and control strategy of inverter.