A calculation method of coupling relationship between multiple sections in chain power grid

Low frequency oscillation or poor dynamic stability tends to occur in long-chain interconnected power system. Factors on the source and grid side. The factors on the generator side and network side both have certain influence on the system dynamic stability, such as, generator control parameters, load characteristics, operation mode, subsystem internal structure and power flow, etc. In order to research the effect of transmission section location and power flow on system dynamic stability, in this paper, for the network made of several chain coupling structure sections, a calculation method was proposed about sensitivity and coupling degree of transmission sections, which contributes to analyze difference among influence of different sections on stability. At first, change law of system damping ratio and relative angles between the delivery end and the receiving end of interconnected system, was analyzed, based on relationship between interface power flow and relative power angle of units on both sides in chain grid. And then, the derivation was conducted, about relative sensitivity of system dynamic stability to interface power flow, following the exploration of coupling mechanism between sections power flow. Research shows that there are several factors associate with the section sensitivity, such as reactance, the angle difference and inertia time constants of sending-end units. Furthermore, the proposed method was applied in three-machine chain system model and Meng-xi chain network, and theoretical conclusion and simulation results verified the validity and feasibility of this method. When actual power grid running dynamic stably, calculation of the sensitivity and correlation of the cross section can provide a reliable basis, for the coordination control of power flow between several sections, as well as system damping improvement program.