For single-phase photovoltaic grid system, taking the circuit topology of double-stage single-phase grid inverter as a core, this paper establishes the mathematical model, and builds the simulation model of 5 kW single-phase grid inverter system in Matlab/Simulink environment. MPPT algorithm based on the observation of the disturbance voltage and double loop control strategy based on feedforward are adopted, whose properties are studied and simulated. With Matlab language, MPPT algorithm is programmed as a function which can simulate the illumination change, and the simulation analysis of illumination invariant and illumination change is respectively carried out. The simulation results show that it not only makes system have better stability and fast dynamic response characteristics, but also realizes the target that the output voltage has the same frequency and phase with inverted current and lower total harmonic distortion rate (THD less than 1%).%针对单相光伏并网系统，以两级式单相并网逆变器的主电路拓扑结构为核心，对其建立了数学模型，并在Matlab/Simulink环境下，搭建了5 kW单相并网逆变器的系统仿真模型。采用基于扰动观测的MPPT算法以及基于电网电压前馈的双闭环控制策略，对其特性进行了深入研究和仿真。并用Matlab语言将MPPT算法编写了函数，可以模拟光照变化，分别针对光照不变和光照变化两种情形进行了仿真分析。结果表明，其不但保证系统有较好的稳定性和快速的动态响应跟踪特性，而且能实现了逆变输出电流与电网电压的同频同相以及较低的逆变电流的总谐波畸变率（THD小于1%）。
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