水轮机调速器参数对电力系统超低频振荡的影响

实际电网中多次发生超低频振荡事件,研究发现调速系统产生的负阻尼是引起超低频振荡的重要原因。该文分别推导了水轮机调速系统在考虑PID参数下的阻尼转矩系数,并且通过分界频率和实际振荡频率分析了水轮机调速系统的阻尼特性。基于单机系统,采用粒子群优化算法对调速器PID参数进行优化,优化目标函数同时考虑了水轮机的转速偏差和调速系统的阻尼转矩,并通过阻尼转矩法比较了优化前后系统的阻尼变化,同时利用附加控制器的方法增加了系统的正阻尼,达到抑制超低频振荡的目的。最后,在4机2区域系统和云南电网中某实际直流孤岛系统中验证了超低频振荡是由调速系统产生的负阻尼所引起的。

Influencing Mechanism Study on Turbine Governor Parameters Upon Ultra-low Frequency Oscillation of Power System

In actual power grids, ultra-low frequency oscillations occur many times, and the negative damping generated by speed control system is an important cause of frequency oscillation. In this paper, the damping torque coefficients of hydraulic turbine speed regulating systems with and without consideration of PID parameters are derived;and the damping characteristics of hydraulic turbine governing system are analyzed with dividing frequency and actual oscillation frequency. Based on single machine system, PSO algorithm is used to optimize the PID parameters of the governor. The objective function takes into account the speed deviation of the turbine and the damping torque of the speed regulating system at the same time. The damping torque method is used to compare the damping changes before and after the optimization, and the positive damping of the system is increased with additional controller to suppress the ultra-low frequency oscillation. Finally, in a 4-machine 2-area system and a practical DC islanded system in Yunnan power grid, it is verified that the ultra-low frequency oscillation is caused by the negative damping produced by the speed control system.