基于故障串电流反向突变判据的光伏阵列线间故障保护方案

光伏阵列发生线间故障时故障电流较小，过电流保护无法有效清除故障。提出一种基于光伏串输出电流反向突变特性的光伏阵列线间故障保护方案。基于光伏串输出电流-电压曲线定性分析了光伏阵列发生线间故障时输出电压、电流的变化特性，得到光伏阵列线间故障下光伏串输出电流反向减小特征。通过光伏串等效电路模型，建立了光伏串输出电流与光伏串故障电池数量之间的量化关系。以最小故障电池数量的电流突变为阈值，提出了基于故障电流反向突变的保护判据。该保护判据可快速准确地定位光伏阵列中的故障串，且只需要测量光伏串的输出电流信号以及光伏阵列输出的电压信号，保护配合只需要跳闸信号。最后，通过时域仿真以及现场测试有效验证了所建立判据的准确性以及所提出的保护方案的正确性。

Line-line fault protection scheme of PV array based on current reverse mutation criterion of fault PV string

The fault current is small when line-line fault occurs in the photovoltaic(PV) array, and overcurrent protection cannot effectively clear the fault. A PV array line-line fault protection scheme based on the reverse mutation characteristics of PV string output current is proposed. The characteristics of the PV string’s output voltage and current under PV array line-line fault are qualitatively analyzed, which shows that the current will reversely decrease under PV array line-line fault. Then, based on the equivalent circuit model of PV string, the quantitative relationship between the output current and the number of the faulty battery is established. Setting the current reduction for one faulty battery as the threshold, a current reverse mutation criterion of fault PV string is proposed, which can effectively locate the fault string of PV array and only need to measure the output current signal of the PV string and the output voltage signal of the PV array. Meanwhile, the protection cooperation only need trip signal. The correctness of the theoretical analysis of the proposed criterion and the effectiveness of the proposed relay protection scheme are verified by time-domain simulations and field test.