孤岛光伏微电网不平衡电压分层控制方法

针对不平衡电压控制电网有功和无功之间耦合程度大而导致控制效果不佳的问题,提出了孤岛光伏微电网不平衡电压分层控制方法。构建双层控制结构,协同控制电压质量。采用双层控制方案,完成不同的控制任务。上层负责调节各分布式电源负荷和功率,通过多个分布式电源并联,控制不平衡电压幅值;下层负责根据电能质量等级指令调整出力,保障系统能量平衡。使用下垂机制分配各分布式电源之间的功率和频率,增加系统阻尼,控制有功和无功功率之间的耦合程度。充分考虑负载变化,采用双环比例积分的PI调节策略补偿电压不平衡。由实验结果可知,该方法不平衡度最终稳定在2.1%并保持不变,具有良好的控制效果。

光伏电站防孤岛测试方法

根据孤岛检测的原理和分布式电源进行分类,详细阐述了各种检测方法的性能和优缺点。在此基础上,提出了采用由高压转换为低压方式实现光伏并网发电系统的防孤岛测试方法。设计了移动式光伏并网逆变器防孤岛检测系统,并解决了10/35 kV光伏电站防孤岛测试问题,可以实现三相不平衡状态带载,最小调整步幅10 W等要求。

FRT Control Method Including Islanding Detection in PCS Model for Photovoltaic Generation

The experimental results by the simulated PV （photovoltaic） system for understanding the cause of disconnection when instantaneous voltage sag occurs are reported in this study. Moreover, it is understood that the PCS with the voltage phase jump detection method which is one of the main causes of the disconnection. We modeled it in the simulation. When fault occurs, even though the residual voltage is more than 20% and the voltage sag time is within 1.0 s, the PCS disconnected by the voltage phase jump detection was confirmed in the simulation results. Ifa large number of PV systems are interconnected in the power system, this study is verified through the simulation that the interaction caused by the disconnection which generated by the voltage phase jump detection. This study is proposed threshold limit value of islanding detection. The validity of proposed method was verified through the simulation in this study.