Research On Control Strategy Of Independent Photovoltaic Power Generation System

With the gradual depletion of energy and deterioration of environment, the rapid development of world economy has seriously restricted, solar as a new green energy has attracted the world’s attention. Photovoltaic power is the most widely used form of solar energy application, it has a very broad application prospect and has become one of the hotspots of domestic and foreign scholars research and development. The associated control strategy of Photovoltaic power generation system directly related to the utilization of solar energy and system stability. Therefore, this paper take independent photovoltaic power generation system as the research object, made an in-depth study on its associated control strategy:Firstly, based on the equivalent mathematical model of photovoltaic cells, the practical engineering model was established, and then obtained the output characteristics curves of photovoltaic cells by simulation, and then verify the correctness of the engineering model; Improved the observation method of fixed step perturbation in the traditional maximum power point tracking, and chosen the Boost transform circuit to realize MPPT, then established the simulation model by Matlab. The result showed that less time was needed to achieve stable output power in the improved perturbation and observation method, and the fluctuation of stable output power was smaller. That verified the superiority of the improved perturbation and observation method.Secondly, by choosing non-isolated bidirectional Buck/Boost converter to realize the two-way energy flow between DC bus and storage cell; By sampling the output voltage of the photovoltaic cell and terminal voltage of storage cell to determine the working mode of bi-directional DC/DC converter, then determine the main parameters of bidirectional Buck/Boost converter according to the working model, by using the Matlab to model the main circuit’s structure of bidirectional converter, and simulation with the main assured parameters. The simulation results meet the requirements of bidirectional buck-boost converter, so verified the correct choice of the n parameters.Finally, the storage cells charge and discharge through the bi-directional DC/DC converter, control strategy is designed for the storage cells charge and discharge method, the charge process was controlled by constant current or constant voltage loop, the discharge process was controlled by voltage and current dual-loop; Analysis on the storage cel’s three working states of charging, discharging and stop working through Matlab, the results verify the feasibility of the charge and discharge control strategy.