Research On Improved Small-scale Photovoltaic Power Generation And Grid System

In recent years, small-scale photovoltaic grid-connected power generation have been developing rapidly, but photovoltaic power generation technology still have many problems, DC/DC converter power switch works in hard switching mode, switching loss, switch voltage and current stress are large. In the rapidly changes environment, the maximum power point tracking malfunction occurs, reduce the tracking efficiency. The dynamic response of grid-connected inverter is slow. Output voltage contains harmonics and reduces the voltage quality.Based on the above issues, the article detailed analysis and studies the small-scale photovoltaic grid-connected power generation system, and proposed the improvements. Traditional photovoltaic DC-DC converters operate in hard switching state, the switching loss, voltage and current stress of switching device is large and other shortcomings, in this paper, we use a soft switch boost converter, its structure is simple, easy to control, greatly reducing switching losses and pressure drop of switching device. Contrast the existing MPPT method and found variable step incremental conductance method have fast tracking and high tracking accuracy, but when the light intensity changes significantly, due to miscalculating the step size ,will cause system oscillation, in this paper, we use an improved INC method. Tracking the maximum power point quickly and accurately, improve the operational stability of photovoltaic power generation system. Grid-connected inverter uses double loop control based on grid voltage feed-forward. DC bus voltage as outer loop and inverter output current as inner loop, all of these controls achieve by DSP. This control can achieve the grid inverter output current and voltage with the same frequency, so achieve unity power factor of the grid-connected inverter, and improve the dynamic response speed of the inverter and the quality of the output voltage.The simulation model of system is established using Matlab, and the experiment is implementing and gives the simulation and experiment results.