基于零序电压相位变化的分布式光伏发电孤岛保护方法

Distributed Photovoltaic Power Islanding Protection Method Based onZero Sequence Voltage Phase Change

分布式光伏主要接入35kV及以下低压配电网,低压配电网故障主要以单相接地故障为主,约占70%以上。由于单相接地故障不影响系统功率正常输送,当电网发生故障时,常规分布式光伏孤岛保护方法存在孤岛判别失效及不可靠问题,给电网安全稳定运行带来严重挑战。首先,推导了电网发生单相接地故障时的零序电压表达式,定性分析了影响零序电压大小和相位的关键因素。其次,对比分析了电网中性点不接电和经消弧线圈接地2种方式下,电网发生单相接地故障时的零序电压大小和相位变化规律,在此基础上,提出了基于零序电压相位变化的分布式光伏孤岛识别方法。最后,对所提出的孤岛保护方法在实际工程中的应用提出建议。

Distributed photovoltaic generation is mainly connected to the low-voltage distribution network of 35kV and below.Low-voltage distribution network faults are mainly single-phase ground faults,accounting for more than 70%.Since single-phase ground fault does not affect the normal transmission of system power,when a fault occurs in the grid,the conventional distributed photovoltaic generation islanding protection method has the problem of islanding discrimination failure and unreliability,which brings serious challenges to the safe and stable operation of the grid.Firstly,the paper derives the expression of zero sequence voltage when a single-phase ground fault occurs in the grid,and qualitatively analyzes the key factors affecting the magnitude and phase of the zero sequence voltage.Secondly,the zero sequence voltage magnitude and phase change law when single-phase grounding fault occurs in two ways,i.e.,the neutral point is not connected to the power grid and the grounding through the arc extinguishing coil,are compared and analyzed,and based on this,a distributed power islanding identification method based on the phase change of zero sequence voltage is proposed.Finally,some suggestions are given for the application of the islanding protection method in practical engineering.