随着经济、社会的发展，人类社会对能源的需求越来越大。传统的化石能源日渐枯竭，寻找清洁、无污染的新能源被世界各国提上议程。太阳能以其分布广泛、清洁、无污染、取之不尽、用之不竭等优点，引起各国政府的重视。近年来，随着科学技术的进步，光伏电池的制造成本越来越低，这给太阳能发电的广泛应用提供了很好的机遇，光伏并网发电技术是未来太阳能发电技术的主要发展方向。本文对小功率并网系统进行了深入研究，并在此基础上设计了一套200W的微型型光伏并网逆变器。 本文首先分析了光伏电池的输出特性，在此基础上介绍了几种光伏电池的最大功率点追踪技术（简称MPPT）。通过分析比较，选择采用变步长滞环比较法作为控制系统前级电路的控制策略，并在Matlab中对其进行了仿真研究。 接着对各种常用的光伏并网系统的拓扑结构进行了分析比较，为所设计的微型逆变器选择了合适的电路拓扑。该拓扑是两级式结构，通过控制前级推挽升压电路实现光伏电池MPPT控制；通过控制后级全桥逆变电路输出的并网电流，实现光伏系统的并网控制。经过对几种电流控制策略的深入研究，最终选择采用电压外环、电流内环的双环控制策略控制并网电流，使其与电网电压同频、同相，并对整个系统进行了仿真研究。 最后对微型光伏并网系统的硬件电路和软件进行了详细设计，给出了系统主电路结构及各元件选型，并对其控制电路、采样电路以及系统软件设计流程等进行了详细设计。为了使逆变器的输出电流能与电网电压同频同相，本文采用了软件锁相环对电网电压的相位进行锁相，并对软件锁相环的工作原理和软件流程进行了详细介绍。 仿真和实验结果表明：该光伏并网系统能够达到预期的并网效果，运行稳定、可靠，性能良好。

With the development of economy and society, the demand for energy in human society is growing, while traditional fossil energy reserves are limited and will pollute the environment, so look for clean and non-polluting energy is a new agenda on the world.The advantages of widespread distribution, clean,non-polluting, inexhaustible, etc make solar energy become attention by various countries.Grid-connected PV echnology is the main direction of solar power. This article studies the topology and control methods of the low-power photovoltaic grid-connected system, and elaborates the design of hardware and software in 200w photovoltaic grid-connected system. Firstly,This article analyzes the output characteristics of photovoltaic cells and proposed several photovoltaic maximum power point tracking technology (MPPT),and select the variable step hysteresis law as a front-end circuit control and simulation its in Matlab. Then this article compare the advantages and disadvantages of the various topologies in different parts of the photovoltaic grid-connected system and choice a suitable for the micro inverter design.The topology is to tier architecture, through the grid current control level after the full bridge inverter circuit output, to realize the control of grid-connected photovoltaic system. The network control strategy of later class divide into the grid-voltage control and the grid-current control grid, here use the latter method to achieve photovoltaic grid inverters and network operation, through compare of several current control strategies , then chose double-loop current control strategies and simulate the entire system. Finally, the design of the hardware and software to micro-grid PV system in detailed and gives the design of system structure, the main circuit component selection, the control circuit, the sampling circuit and the system software design process. To make the output current of inverter with the same frequency and phase to grid voltage, here use a software PLL to lock-in phase of the grid voltage and described the principle and software processes in detail. The simulation and experimental results showed that: the system can implement the required performance of supplying power to grid perfectly. The system works stabilization and has good performances.