环状柔直工程直流极闭锁判据及措施量计算方法

DC blocking criterion and measure calculation method for VSC-HVDC grid of ring structure

以往常规直流与柔性直流工程的结构均为端对端或多端辐射,对应的稳定控制系统采用换流变电气量和直流极非正常停运信号作为极闭锁的判据,但该方法不适合环状结构的柔性直流输电工程应用,无法可靠地识别换流器闭锁故障。文中根据张北柔直输电工程稳定控制系统研制经验,提出一种新的适用于稳定控制的直流极闭锁判据改进方法。该判据在直流轻载时将直流控制保护的特征信号作为主要判断对象,在直流极运行功率超过10%额定功率时则将直流控制保护的特征信号结合换流变电气量作为主要判断对象,改进后的判据同样适用于特高压直流输电工程与多端环网柔性直流输电工程。同时,文中提出张北柔直输电工程稳控措施量计算方法,为后续柔性直流输电工程、特高压直流输电工程应用提供了参考。理论分析及实时数字仿真系统(RTDS)实验验证了判据的可靠性。

In the past,the structures of conventional direct current(DC)and flexible DC transmission projects were end-to-end or multi-terminal radiation.The corresponding stability control system uses the converter electric quantity and pole emergency switch off(ESOF)signal as the criterion of pole blocking.It is not suitable for the application of flexible DC power transmission engineering with ring structure,because the DC converter blocking failure cannot be identified reliably.According to the development experience of stability control system of Zhangbei voltage source converter based high voltage direct current(VSC-HVDC)transmission project,a new improved method of DC pole blocking detection is proposed in this paper for stability control.This criterion adopts the characteristic signal of DC control and protection as the main judgment object when DC light load is applied,and adopts the characteristic signal of DC control and protection combined with the converter electric quantity as the main judgment object when the DC power is above 10%of rated power.The improved detection is applicable to both HVDC transmission projects and ring structure flexible DC transmission projects.At the same time,the calculation method of stability control measures of Zhangbei VSC-HVDC transmission project is proposed,which provides a reference for the application of subsequent flexible DC transmission projects and HVDC transmission projects.Theoretical analysis and real-time digital simulation system(RTDS)experiment verifies the reliability of the criterion.