Research And Design Of Single-phase Photovoltaic Power Grid Connection System

With the population increasing,people's demand for resources increases rapidly.Because solar energy is renewable,clean,pollution-free and abundant,it has provided new ideas and development directions for the contemporary society to solve the energy crisis.Photovoltaic power generation and grid connection are the trend of the times.On this background,single-phase photovoltaic grid-connected inverters are analyzed and an optimized design is proposed in this paper.First of all,the main structure of the single-phase photovoltaic power generation system is designed.In order to make the system more stable and lower in loss,a bipolar non-isolated system is selected.Then,the pre-stage circuit is designed.For the sake of improving the conversion efficiency and avoiding output waste,the continuous working mode of boost chopper is selected to track the maximum power point.Finally,the insulated gate transistor is choosed as the switching transistor.The circuit structure is optimized by calculating the value of the inductance and filter capacitor of the boost chopper circuit.Through the analysis of several commonly used maximum power tracking methods,a new method,a variable step increment method of conductance is proposed,and the maximum power tracking simulation is carried out in the selected circuit.Neglecting the power loss of the circuit components,according to the DC voltage value and power value predicted by the previous chopper circuit parameter design,the maximum power output is achieved at last.The single-phase photovoltaic grid-connected inverter is optimized.Through the analysis of inverter circuit and inverter,the voltage-type single-phase full-bridge inverter circuit and L-type filter circuit areadopted,and relevant parameters are calculated.The double-loop control method based on triangular wave comparison method is selected,where the voltage outer loop stabilizes the DC side voltage,and the current inner loop grid-connected current is tracked and detected.Finally,a simulation model is built for the whole system on the basis of the foregoing.The simulation results show a stable voltage and current waveforms can be obtained no matter how the light intensity changes.The current waveform is a sine wave and stable voltage value is 220 V.At the same time,there is basically no harmonic component after the grid-connected current is stable.The optimization of the photovoltaic grid-connected inverter is finished.