基于注入电流扰动法的光伏直流模块的防孤岛控制

传统的交流型并网发电系统中，可以通过检测电网电压或频率，采用有功扰动、无功扰动或频率扰动等方法实现防孤岛控制。而在共直流母线系统中，母线直流电压是唯一可检测的变量，因此传统的防孤岛控制策略无法适用。以共直流母线分布式系统中光伏直流模块的防孤岛控制为研究对象，建立了模块正常运行和孤岛运行时的数学模型，推导得到了在两种工况下模块输出电压的时域表达式，并在此基础上提出了一种基于注入电流扰动法的新型防孤岛控制策略。该控制策略的核心思路是通过控制模块输出电流和扰动步长来改变在扰动时间内模块的输出电压特性，并根据检测判据来决策是否发生孤岛。最后，本文以Boost+FB-LLC的两级式结构作为光伏直流模块的工作拓扑，并设计了一台1000W的实验样机，样机实验结果验证了本文所提出的防孤岛控制策略的有效性。

Anti-islanding Control of Photovoltaic DC Module Based on Injected Current Perturbation

In conventional AC grid-connection generation system, anti-islanding control can be implemented using active power perturbation, reactive power perturbation or frequency perturbation when detecting grid voltage or frequency. However, in DC bus system, the only available parameter is the bus voltage, therefore, conventional anti-islanding control strategy is invalid in this application. Anti-islanding control strategy of photovoltaic DC module in DC bus distributed system is studied in this paper, the mathematical model of normal operation and islanded operation are build, and time-domain equation of output voltage in this two operation conditions are also derived. A novel anti-islanding strategy is proposed by injected current perturbation based on the mentioned work. The key of this strategy is to control the output current and disturbance step to change output voltage characteristics in the duration of disturbance, and to judge whether islanding is occurred according to detection criteria. Finally, Boost+FB-LLC is selected as the main topology for photovoltaic DC module, and a prototype with 1000W rated power is build. The experimental results verify the effectiveness of proposed anti-islanding control strategy.