当今，严峻的能源枯竭问题和日益严重的环境问题已经成为制约各国经济、社会发展的瓶颈。相对于传统的化石能源（煤、石油、天然气），太阳能能提供洁净的、可再生的资源，已获得了广泛的关注和重视。在太阳能的各种利用方式中，光伏并网发电已成为主要研究方向。并网控制器是光伏并网系统的核心部分也是本文研究的重点。本文对并网控制器的拓扑结构、控制策略、参数选取、最大功率点跟踪算法以及孤岛保护方法等多方面作了详细的分析和研究。本课题完成了额定功率为2kW的并网控制器样机的开发。样机采用带Boost环节的两级结构，前级把较低的光伏阵列电压升到较高值，后级完成并网电流的控制。该结构的应用扩大了输入电压的适用范围，增大了控制器的效率，减小了控制器的体积和重量。同时，也对各个环节的控制方法作深入的研究。对Boost变换器的输入电流采用PI控制，既克服了其开环控制存在稳态误差的缺点，又避免了单一电压反馈控制系统不稳定的情况，提高了稳定性和动态特性。对并网电流采用预测无差拍控制，实现了高效跟踪，电流谐波畸变率低、功率因数高。最大功率点跟踪采用了将常压法和多重判据法结合起来的混合算法，既能准确跟踪最大功率点，又能提高系统的稳定性。孤岛检测采用双重正反馈主动频率偏移法，可以快速检测出孤岛的发生，并对电能质量的影响小。通过实验，控制器运行稳定、各部分波形与理论分析相符合。通过与国外成熟产品对比，自主开发控制器的各性能指标都达到产品化的要求。
Nowadays, the issues like energy crisis and environment pollution have become the bottleneck of restricting the rapid increase of economic industry development chain around the world. Compared to the traditional fossil fuel fired utilities, solar energy can supply the energy demand in a clean and sustainable way, and has gradually drawn broad attention. The grid-connected photovoltaic generation is one of important applications using solar energy in many ways.The grid-connected controller, which can convert the direct current (DC) outputted from solar panels into the alternating current (AC) with favorable waveforms, is the core device of the grid-connected photovoltaic system. In this thesis, our researches and studies on the controller mainly focus on the topologies, control strategies, parameter settings, maximum power point tracking (MPPT) methods and anti-islanding methods.The sample machine of grid-connected controller with 2 kW is developed based on SH7047 MCU. The controller bears a dual-stage structure with Boost unit. The former stage can boost the voltage of photovoltaic arrays to a higher one using a Boost circuit. The shaping and inverting of the output current have to be done in the latter stage at high voltage level. This designed topology effectively avoids a transformer. On the other hand, it increases the controller efficiency, decreases device size and weight as well as expands the input voltage of the controller. Furthermore, the control strategies of other units are studied intensively as well. The PI control strategy is employed to control the input current of Boot unit. Such control strategy overcomes the existed errors from the open-loop control way, and improves the system stability and dynamic performance compared with the single voltage feedback loop control system. By applying predictive deadbeat-control strategy to the grid-connected current, the grid-connected controller produces a low THD sinusoidal current with fast response and high accuracy. A novel hybrid MPPT algorithm, which combines normal constant voltage method and multi-criterion method, is employed with much better dynamics and stability characteristics. A modified active frequency drift method is applied to effectively detect the islanding rapidly whilst keeping a high power quality.In accordance with the experiments, the results demonstrate that the grid-connected controller performs well, and the curves of each part are basically consistent with the curves from theoretical analysis. Compared with the mature foreign product in many aspects, all kinds of performance indices of the home-made grid-connected controller meet the product requirements.
