励磁调差单元对电力系统低频振荡的影响

Influence of Excitation Adjustment Unit on Low-frequency Oscillations in Power System

自动励磁调节器对改善发电机的静调压特性起了积极作用,但对调差电流引入后的分析不足。为了研究调差单元引入对电力系统低频振荡的影响,采用戴维南等效电路分析了不同励磁控制方式下单机无穷大系统电路的运行特性,对比研究了调差引入前后励磁系统测量电压变化对系统阻尼特性的影响,并通过Matlab建模仿真分析了调差单元参数及发电机工况改变时低频振荡阻尼的变化特性。理论分析与仿真结果表明,调差单元引入后测量电压变化会对系统阻尼力矩产生一定的影响,且调差提供阻尼的大小,不仅与调差单元的接入方式的正、负有关,也与发电机所处工况、调差系数以及励磁参数有关。

Automatic excitation regulators play an active role in improving the static voltage regulation characteristics of a generator. However, the analysis after the introduction of adjustment current is insufficient. To study the influence of adjustment unit on the low-frequency oscillations in power system, the operation characteristics of the circuit in a single-machine infinite bus system under different excitation control patterns are analyzed using Thevenin's equivalent circuit, and the influences of the variation of measured voltage of excitation system on the system’s damping characteristics before and after the introduction of adjustment are compared. Then, the changing characteristics of low-frequency oscillation damping with different parameters of adjustment unit and different operation conditions of the generator are analyzed through modeling and simulations using Matlab. The theoretical analysis and simulation results show that the change in measured voltage after the introduction of adjustment unit will affect the system’s damping torque to a certain degree;in addition, the magnitude of damping provided by adjustment is not only related to the access means of adjustment unit(i.e., positive or negative), but also to the generator’s operation condition, the values of adjustment parameters, and excitation parameters.