考虑轴系特性的汽轮发电机阻抗模型

Impedance Model of Turbo-Generator Considering Torsional Characteristics of Shafting

与状态空间法和复转矩系数法相比,基于阻抗的分析方法更便于拓扑扩展和黑盒系统建模。然而,现有的汽轮发电机阻抗模型,如RL串联阻抗模型或同步发电机等效电路阻抗模型,仅关注汽轮发电机的电气特性。上述简化的阻抗模型无法考虑汽轮发电机轴系特性的影响,甚至导致错误的分析结果。针对这一问题,该文建立了考虑轴系特性的汽轮发电机阻抗模型,并以风火打捆外送系统为研究对象,对比了基于RL等效阻抗模型和所建立阻抗模型的振荡分析结果。验证了所建立模型在含有新能源以及电力电子设备的电力系统中进行稳定性分析的适用性与准确性。研究结果可为含汽轮发电机的复杂结构电力系统的稳定性分析提供模型。

Due to the increasing number of electronic power devices in power systems,power system structures have become complicated,and analyzing power system stability containing power electronic devices and turbo-generators is difficult.The impedance-based analysis method is a good choice because extending the system topology and establishing the black box system model is easy.However,the impedance of the turbo-generator only reflects electrical characteristics.This paper establishes an impedance model of the turbo-generator considering the mechanical part of the turbine,governor,and shafting mass-spring.The turbo-generator is divided into electrical and mechanical parts.For the electrical part modeling,an ideal state is assumed,and the small signal equation of the synchronous motor is standardized.For the mechanical part modeling,a small signal model is established for the shafting part,steam turbine,and speed regulator.Calculation results show that the impedance model of the turbo-generator in the d-q coordinate system is a 2nd-order matrix.Finally,the impedance model of the turbo-generator considering the shafting part is obtained by converting it into a sequence impedance model and considering the frequency coupling effect.The theoretical model is verified by the frequency scanning method.The experimental results of frequency scanning points agree with the theoretical model,which verifies the correctness of the impedance model.Taking the wind-thermal bundling delivery system as the research object,compared with the oscillation analysis based on the RL equivalent impedance model,the proposed impedance model can identify the sub-/super-synchronous oscillation risk.The proposed model for stability analysis in power systems containing new energy and power This study draws the following conclusions.(1)Compared with the equivalent circuit impedance of the synchronous motor,the proposed impedance model is more accurate near the natural torsional vibration frequency of the turbo-generator shafting,improving the model’s accuracy.(2)The turbo-generator impedance model can perform stability analysis well in complex power systems containing new energy systems and power electronic equipment.It is more accurate than the traditional turbo-generator impedance model in the sub-/super-synchronous frequency band.(3)Compared with the complex torque coefficient method,the impedance-based analysis has advantages in accuracy in multi-machine systems containing electronic power devices.