基于频率响应法的发电机低励限制与PSS协调控制

Coordinated Control Between Under-excitation Limiter and Power System Stabilizer of Generator Based on Frequency Response Method

低励限制器(UEL)作为励磁系统的限制环节对系统稳定性有重要影响,但由于UEL参数设置不合理,UEL动作后恶化了电力系统稳定器(PSS)提供正向阻尼的作用,导致机组出现振荡甚至解列的严重故障在电网实际运行中多次发生。文中基于扩展Heffron-Phillips模型,从理论上推导出励磁系统加入PSS和UEL的简化模型,采用频率响应法,画出励磁系统分别加入PSS与UEL的开环传递函数的波特图,分析UEL与PSS的作用频段,并给出具体的UEL参数设置方案,方案可以使UEL与PSS协调配合。以云南电网数据为例,在PSASP和MATLAB仿真软件下建立单机—无穷大模型验证理论分析的正确性。仿真结果表明:采用频率响应法对UEL进行参数整定后,UEL动作不影响PSS的输出效果,二者可以协调配合以确保系统的稳态运行。

The under-excitation limiter （UEL）, as a limit part of the excitation system, has an important influence on the stability of the system. However, due to the unrational parameter setting of UEL, the positive damping effect provided by the power system stabilizer （PSS） is weakened after UEL acts. This causes the oscillation and even the serious fault of the generator frequently in the actual operation of the power grid. Based on the extended Heffron-Phillips model, a simplified model with PSS and UEL for excitation system is derived. The frequency response method is used to draw the Bode diagram of the open-loop transfer function of PSS and UEL. The frequency band of UEL and PSS is analyzed, and a specific parameter setting program of UEL is given, which can make UEL and PSS coordinated. Taking the data of Yunnan power grid for example, the single machine infinite-bus system is developed to verify the correctness of the theory in simulation software of PSASP and MATLAB. The simulation results show that, after the UEL parameter is set by the frequency response method, the UEL action will not affect the output of the PSS, and UEL and PSS can cooperate to ensure the steady-state operation of the system.