Study On The Effect Of OLTC To The Voltage Stability Of Power System

Owing to several widespread system blackouts resulting from voltage collapse throughout the world, the problem of voltage stability has attracted persistent interest of researchers in the last two decades. Though great achievement has been made in this area, there still exist some problems. For example, there is the distinct opinions mechanics of the voltage collapse and there is not the integrated theory of the voltage stability model and dynamic analysis. In the course of researching on power system voltage stability, it has been realized OLTC dynamic characteristics effect significantly on voltage stability. This paper studies the proceeding and the factor of effect of OLTC on voltage stability.In the aspect of preventive measures of voltage collapse, combining classical power system model and the OLTC continuous model, Long-term voltage instability caused by OLTC automatically regulation is analyzed when the reactive power is insufficiency. Then the validity is discussed when the OLTC is locked and the OLTC is reversed. And the definitions of the limit-time when the OLTC locked and when the fault is cleared which have good value to avoid voltage collapse.Based on the bifurcation theory and the distinguish theorem of the dynamic and static voltage instability, this paper discuses the "migrating" problem of voltage instability static-bifurcation curve, the mechanism of voltage instability, and the primary factor affecting the "reverse regularization effect" of voltage caused by the action of OLTC. These factors include the OLTC voltage regulation span, OLTC capacity and OLTC power transmission distance.Using time domain simulation program, long-term voltage instability caused by OLTC automatically regulation is analyzed after disturb. The analysis proves that load can run at the lower voltage when OLTC is locked and the reverse regulation can delay the voltage collapse time. Based on the bifurcation theory, static state prove that more bigger regulating step size ,more larger capacity and longer electric distance are infaust for voltage stability.The analysis of power system embodies the OLTC used to improve the load voltage to void voltage instability and voltage collapse has done good work.