Maximum Power Point Tracking And Grid-connected Operation Of Photovoltaic Power Generation System

In recent years, as the energy shortage and environmental pollution increase, the development and utilization of renewable energy have become a research hotspot, and grid-connected photovoltaic power generation has been widespread concern as a way of solar energy development and utilization. In order to allow maximum power output of PV arrays, and to output the energy into the grid as high-quality sine wave to reduce the pollution of the grid, it's needed that grid-connected PV inverter should adjust the operating point of the PV arrays, and transform the forms of the energy to output into the grid.In this paper, the research object is the grid-connected PV inverter. First, the operation principles and their respective characteristics of the commonly used algorithms for the maximum power point tracking (constant voltage method, perturbation and observation method, conductance increment method) are analyzed. The division operation in is eliminated by processed and the processing efficiency is improved. For the step size can affect the tracking speed and the tracking accuracy, perturbation and approximation method is put forward as a new algorithm for the maximum power point tracking. The new method can achieve the MPPT quickly and accurately with variable step size.Second, the operation principle and control method of grid-connected PV inverter are also analyzed in this paper. The characteristics of two-stage and single-stage grid-connected PV inverter are contrasted. The reason of"DC bus capacitor voltage collapse"in single-stage grid-connected PV inverter is discussed, and a voltage controlled loop is added to solve the problem. The digital implementations of some key technologies (e.g. SPWM, PID, PLL) in grid-connected inverter are studied.Finally, some simulation and the design of the grid-connected PV inverter are given in this paper. The simulation and experimental results show that the grid-connected PV inverter which using perturbation and approximation method can achieve the MPPT quickly and accurately and output the energy into the grid as high-quality sine wave with low THD and high PF.