Researches On Voltage Emergency Control Of Interconnected Power System

Electric power is the backbone of energy and economic lifeline of each country.With the rapid growth of national economy,the extent of power network interconnection is intensifying gradually,leading to the formation of huge interconnected power systems.This change makes the operation mode of power system become more complicated,and it's stability problem which makes the influence range of local fault increase is becoming more and more prominent.Moreover,this situation is easy to develop into a cascading failure,makes power system to collapse and brings great risk to the normal operation of it.Voltage control is one of the most important steps in maintaining the normal operation of power system.Emergency control is a means to restore the safe and stable operation of power system,and the voltage emergency control is proposed as an important part of it.The voltage emergency control requires that control system take a range of means to recover the voltage level in the shortest possible time.Voltage emergency control is the main mean to ensure the voltage stability and prevent the occurrence of the voltage collapse.In this thesis,the problem of voltage emergency control in huge interconnected power systems is studied.The main contributions are as follows:(1)The main reason of voltage instability is studied,and from the mechanism we can know that reactive power compensation equipment has play an important role on power system stability and voltage control.(2)By comparing the main performance of different voltage control means in emergency state,it's clear that the fast reactive power sources such as synchronous generators,SVC and STATCOM are the main means of voltage emergency control.(3)Aiming at the shortcomings of existing methods of reactive power and voltage partitioning,such as single index,huge data processing capacity,and poor real-time performance,the method of emergency partitioning of voltage based on principal component analysis is studied.The voltage instability node's sensitivity to the reactive power control node,the electrical distance between the components,the self-power margin of reactive power control node,and the priority of each reactive power control node are taken as the characteristic index of voltage control partition under the state of emergency.This method could meet the requirements of power system real-time partitioning in emergency state.In this way,on the basis of reducing the amount of calculation,the control area is divided quickly and reasonably according to the running state of the system..(4)Aiming at the demand of reactive power in node voltage control in power system,a kind of voltage emergency control organization structure with multi-level Agent is proposed.In this structure,the control equipments at all levels as the intelligent Agent with social collaboration,and through the interaction and coordination of each other,the rational use of reactive power in the system is realized.(5)Aiming at the problem of voltage regulation is less and lack of regulatory capacity after the exhaustive means in emergency control,the voltage emergency control strategy which based on various cooperation methods is studied.This strategy aims to restore voltage level of the failure point,by taking effective control means,better recovery voltage level to the safety range with minimal regulation costs,meet requirements of power system voltage stability.