Research On Single-Phase Grid-Connected Photovoltaic System Based On Digital Signal Processor

With the growing global energy crisis and environmental pollution, the development and utilization of clean renewable energy is imperative. Solar is favored for its rich in natural resources, renewable, clean and harmless. The use of solar energy has become a hot spot of the world, and photovoltaic power generation as the development trend of utilization of solar energy, is bound to rapid development. Therefore, the research and design of photovoltaic grid-connected system has practical significance.In this paper, single-phase grid-connected system as the research object, photovoltaic grid-connected system is theoretical analyzed. On the network topology of the system, the choice of parameters, maximum power point tracking, control strategy and preventing island aspects of photovoltaic grid-connected system are researched in detail.In this paper, the equivalent circuit and mathematical model of photovoltaic cells was analyzed and get the output characteristics of photovoltaic cells. Using MATLAB/Simulink simulation software to simulate the output characteristic of photovoltaic cells in light and temperature change based on the mathematical model of photovoltaic cells, which provides the feasibility of theoretical basis of the maximum power point tracking (MPPT). Several commonly used maximum power point tracking control algorithm are researched and compared, and their advantages and disadvantages are presented. The incremental conductance has been improved.The main circuit topology and control method of inverter are analyzed in this paper. According to the characteristics of the circuit structure, the design parameters of the main devices and the filter are provided. Common current control strategy are analyzed, and confirmed by simulation. Hysteresis current control has been improved, with general hysteresis control were analyzed and compared. The simulation results show the availability and reliable of proposed control strategy.Based on TMS320LF28335, the single-phase grid inverter system’s main control circuit has been designed, including the minimum system, clock circuit, drive circuit, sampling circuit and so on. The control process of DC/DC and DC/AC circuit are introduced in detail. According to the principle of grid-connected inverter phase-locked digital lock, phase-locked digital lock of grid-connected inverter is constructed based on TMS320LF28335, and the grid-connected current can track the grid voltage, achieving the system hardware circuit design and control strategy.In this paper, the mechanism of islanding is analyzed, and the advantages and disadvantages of active islanding detection and passive detection are elaborated. The active frequency drift (AFD) and active frequency drift with positive feedback (AFDPF) are simulated by Matlab/Simulink, and the simulation results show the rapidity and availability of AFDPF.