适用于新能源并网系统的距离保护方法

Distance protection method applicable to renewable energy grid-connected systems

为进一步提升距离保护在新能源并网系统中的性能,提出一种综合考虑并网换流器控制策略和传输线分布电容效应的距离保护方法。当系统发生不对称故障时,结合换流器的控制特性、系统的序阻抗特征和过渡电阻的纯阻性特征,消除故障回路方程中过渡电阻和对端系统参数等3个未知量,进而实现R-L模型中对故障距离的求解。随后基于R-L模型中的计算结果设置整定点,并利用Bergeron模型中的计算公式推导整定点处的真实电气量。最后联列整定点至故障点的故障回路方程求解故障距离,以减弱分布电容效应对距离保护的影响。仿真结果验证了该方法受换流器故障特征和过渡电阻影响小,在长线中仍具有较好的性能。

To further improve the performance of distance protection in renewable energy systems,a distance protection method is proposed,which considers the effects of control system and the distributed capacitance effect of the line.When an asymmetric fault occurs in the system,combined with the control characteristics of the converter,the sequence impedance characteristics of the grid and the pure resistive feature of the fault resistance,three unknowns in the fault loop equation can be eliminated,and the solution of the fault distance can be solved in the R-L model.Then,the setting point is set based on the calculation results in the R-L model,and the real electrical quantity at the setting point can be deduced by the calculation formula in Bergeron model.Finally,the equation from the setting point to the fault point is simultaneously solved to reduce the distributed capacitance effect on the distance protection.The simulation results testify that the method is less influenced by the fault features of the converter and fault resistance.It still has good performance in long line.