Research On Off-grid Single-phase Low-power Photovoltaic Voltage Conversion Mode

As China’s demand for energy development continues to increase,photovoltaic power generation has become one of the mainstream directions to solve the problem of energy shortages,which can alleviate the consumption of non-renewable energy to a certain extent.As a green and renewable energy,solar energy can be vigorously promoted in areas where the public grid is not covered or has weak coverage with sparsely populated areas,high light intensity and long time.The photovoltaic voltage conversion mode is a vital part of the photovoltaic power generation system.Its control effect can ensure the output power quality of the system and improve the power supply reliability of the photovoltaic power generation system.This article will focus on the off-grid single-phase low-power photovoltaic voltage conversion mode and control Strategy for research.This paper firstly analyzes the two voltage conversion modes of photovoltaic power generation system—isolated voltage con version mode and non-isolated voltage conversion mode.Combining the working principle of single-phase full-bridge inverter circuit,the mathematical model of the two voltage conversion modes is established.The inverter circuit is the key module in the two modes,and its control effect is very important to the output power quality and control accuracy of the photovoltaic power generation system.Because the traditional double closed-loop PI control accuracy is poor and the output voltage is unstable,the double closed-loop control strategy of single-phase inverter circuit in dq coordinate system is studied.Aiming at the problem that the standard particle swarm optimization algorithm(SPSO)has a slow convergence speed in the later stage of optimization and the particles are easy to fall into the local optimum,the Fuch mapping is applied to the SPSO and introduces the nonlinear inertia weight ω to form an adaptive inertial weight particle swarm optimization algorithm based on Fuch mapping(Fuch-PSO),which improves the convergence speed and search accuracy of the algorithm.Applying the Fuch-PSO algorithm to the offline parameter optimization of the PI controller solves the problems of parameter tuning difficulties and poor control accuracy,and effectively improves the robustness and dynamic response performance of the system.Based on the above theoretical research,on the Matlab/Simulink simulation platform,the simulation research on the off-grid single-phase low-power photovoltaic voltage conversion mode is carried out,and the simulation waveforms of the two conversion modes are compared and analyzed.Design and build an experimental platform with DSP control chip TMS320F28335 as the core,and focus on the experimental verification of the two conversion modes.The simulation and experimental results show that the Fuch-PSO optimization algorithm improves the control accuracy of the system,and compared with the non-isolated voltage conversion mode,the isolated voltage conversion mode is more suitable for areas that are not covered by the public grid or where the grid coverage is weak.