基于直观线性化模型的同步发电机电磁力矩解析

Analysis of synchronous generator electromagnetic torque based on visual linearized model

含阻尼绕组同步发电机电磁力矩系数的传统算式忽略直轴阻尼绕组与励磁绕组的互感,且不考虑自动励磁调节(AVR)的作用。为提高电磁力矩系数计算的准确性,细化关于AVR和阻尼绕组对机组稳定性影响的认识,基于计及阻尼绕组作用的c1-c12模型,采用微振荡法建立了计及AVR以及直轴阻尼绕组与励磁绕组互感的同步发电机电磁力矩系数表达式。基于这些表达式,按是否与AVR有关,将电磁力矩划分为固有分量和受控分量,对交、直轴阻尼绕组,励磁调节主通道等对机组同步能力特别是阻尼能力的影响以及低频振荡的机理进行了详细分析。分析表明,AVR总是削弱机组阻尼;在AVR作用下,交轴阻尼绕组的阻尼作用得到增强,而直轴阻尼绕组反而可能提供负阻尼;外部电抗和有功负载的增大导致固有阻尼能力下降;AVR削弱阻尼的强度不仅与其增益有关,而且随着固有阻尼能力的下降而增强。根据c1-c12模型与Phillips-Heffronk1-k6模型下阻尼力矩系数之差,给出了k1-k6模型等效阻尼系数算式。

In traditional formulas of electromagnetic torque coefficients for the damped synchronous generator,the mutual inductance between d-axis damping winding and excitation winding is neglected and the effect of AVR（Automatic Voltage Regulator） is not considered. To improve the computing accuracy and better understand their effects on unit stability,some formulas of electromagnetic torque coefficients are founded by applying small oscillation method,which is based on the c1-c12 model of single-machine infinite-bus system and considers effects of AVR and mutual inductance. Based on formulas,the electromagnetic torque is divided into inherent part and controlled part according to whether it is related to AVR. Effects of q- axis damping winding,d- axis damping winding and main excitation regulating channels on synchronizing capacity,especially damping capacity,of generator unit,and the mechanism of low-frequency oscillation are analyzed in detail. It is achieved that,AVR always weakens the unit damping;q-axis winding damping is enhanced under AVR while d- axis winding may supply negative damping;the augment of external reactance and active power load reduces the inherent damping;the damping weakened by AVR is related to AVR gain and increases with the inherent damping decreasing. The calculating .formula of equivalent damping coefficient of k1- k6 model is introduced according to the difference of damping torque coefficients between c1-c12 model and Phillips-Heffron k1-k6 model.