抽水蓄能机组RTDS仿真与失磁保护改进研究

抽水蓄能机组具备调峰、调频、调相以及事故备用等功能,对电网的安全稳定运行有重要的作用。抽蓄机组容量大、结构复杂、造价昂贵,在现场和物理模型上均无法进行大量的故障及异常运行试验。基于RTDS搭建了抽水蓄能机组的仿真模型,模拟机组在多种工况、多种负荷水平下的机组区内外故障及失磁等异常运行状态。证明在抽水调相工况下发生失磁时,现有的以定子阻抗判据为主的失磁保护有缺陷,机组励磁不能及时切换,不利于系统的稳定运行。对仿真数据进行分析,提出了新的改进失磁保护的KP阻抗圆判据,实现了机组全工况无死区的失磁保护。该判据算法对相关继电保护从业人员具有一定的参考价值。

RTDS simulation and improvement of excitation-loss protection for pumped storage units

A pumped storage unit has the functions of peak load,frequency,and phase regulation as well as emergency standby.Thus it plays an important role in the safe and stable operation of a power grid.Because of the large capacity,complex structure and expensive cost of a pumped storage unit,it is impossible to carry out a large number of fault and abnormal operation tests on site and physically model them.Based on RTDS,a simulation model of a pumped storage unit is built to simulate internal and external faults as well as the abnormal operation of the unit such as excitation-loss under various working conditions and load levels.It is verified that the existing stator impedance judgment criteria of excitation-loss protection is defective and the unit excitation cannot be switched in time when excitation-loss occurs under the condition of pump phase regulation.This is not conducive to the stable operation of the system.Based on the simulation analysis,a new KP impedance circle criterion is proposed to improve excitation-loss protection,so as to realize the excitation-loss protection without a dead zone in the whole working condition of the unit.The criterion can be used as a reference for relevant relay protection practitioners.