Research On Power System Static Voltage Stability Analysis And AVC System Operation Status Evaluation Index

Static voltage stability analysis plays an important role in identitying power system static voltage stability margin and avoiding the occurrence of voltage instability. Voltage and reactive power operation status assessment is not only an important method of comprehensive grasping voltage and reactive power operation status, but also useful in developing the weakness of reactive capacity configuration and the control strategy about voltage and reactive power. With the development of intelligent electric power industry, AGC(Automatic Generation Control) and AVC(Automatic Voltage Control) have become core functions of electric power dispatch automation system. The use of AGC and AVC have significant impact in the distribution of active and reactive power flow. However, as exsiting static voltage stability analysis method neglecting the impact of different active load distribution methods of AGC units, and the voltage and reactive power operation status assessment method is not consider the area control features of AVC system, the corresponding assessment results cannot match the real power system accurately. Thus, this paper consider the AGC and AVC influence in static voltage stability analysis method as well as the loacal and partition characteristics of AVC in voltage and reactive power operation status assessment methods, the main results are as follows:(1)The existing continuation power flow(CPF) model which considering the regulation effects of AVC still has some defects, such as neglecting the static characteristics and the AGC regulation behaviors. Those defects make the static voltage stability analysis results cannot match the real power system accurately. For this reason, a new CPF model considering the static characteristics of power system and the regulation effects of the AGC and AVC systems is proposed. In the proposed model, following modifications are added to the CPF method which only considering AVC control behaviors: 1) the static frequency and voltage regulation characteristics of generator and load are considered, 2) the load-frequency advanced control strategy of AGC is introduced, 3) the node types expansion scheme and its conversion strategy are improved. And then, putting the estimation and allocation of system total adjustment amount, as well as the control modes conversion into the predictor-corrector scheme of CPF algorithm to ensure the proposed model solved effectively. The validity of the proposed model and its solution algorithm are illustrated by simulation and comparison on the IEEE 39-bus system.(2)The existing voltage and reactive power operation status assessment methods only consider the substation's voltage and reactive power control strategy, it cannot meet the assessment requirements of the voltage and reactive power hierarchical control mode. Thus, an evaluation index system for voltage and reactive power operation status of regional power grid under automatic voltage control is proposed. Based on the index system which only consider the local control strategy, the proposed evaluation index system supplements local control indicators relating to volatility of reactive load and unqualified reason of voltage, as well as the area control indicators about area supply bus voltage qualification, area gateway reactive power qualification, area load reactive power equilibrium degree and the voltage and reactive power unqualified reason. To verify the validity of the proposed index system, the evaluation analysis results of a regional power grid in Guangdong Province are given.