火电机组交互影响对次同步振荡的作用机理研究

Study on the mechanism of interaction between thermal power units on subsyn⁃chrouns oscillation

有研究表明,多机系统发生SSO(次同步振荡)时,机组间具有相近扭振频率。为此,分析了相近频率机组轴系间的交互影响,及系统串补度、机组间电气距离和相近扭振频率对次同步振荡的作用机理。首先,基于特征矩阵,推导两台火电机组并列送出系统的复转矩系数表达式。然后,将单机的简化复转矩系数法扩展到多机系统,推导了双火电机组电气阻尼的简化表达式,分析了其他机组对待研机组阻尼的作用,结果表明,串补度、机组电气距离以及相近扭振频率都会影响到系统阻尼和稳定性。最后,通过算例验证了各影响因素对系统次同步稳定性的作用机理。

Research findings indicate that in multi-unit systems experiencing subsynchronous oscillations(SSO),the units tend to exhibit similar torsional vibration frequencies.Therefore,an analysis was conducted on the interac⁃tive effects among shaft systems of units with similar frequencies,as well as the mechanisms of system series com⁃pensation,electrical distances between units.Additionally,the paper delved into the mechanisms through which system series compensation,electrical distances between units,and similar torsional vibration frequencies impact the SSO.Firstly,based on characteristic matrices,the expression for the complex torque coefficients of two parallel thermal power units in the system was derived.Subsequently,the simplified complex torque coefficient method for a single unit was extended to encompass multi-unit systems,resulting in a streamlined expression for the electrical damping of dual thermal power units.The analysis further examined the influence of other units on the damping of the target unit,revealing that series compensation,electrical distances between units,and similar torsional vibra⁃tion frequencies all exert an influence on system damping and stability.Finally,the mechanisms through which in⁃fluencing factors affect the subsynchronous stability of the system were validated through numerical examples.