Research On Frequency Stability And Emergency Control Strategy Of UHV AC/DC Receiving End Grid

With the acceleration construction of UHV large-capacity trans-regional transmission channels and the conceptualization of global energy interconnection,the pattern of UHV AC/DC hybrid power system emerged gradually with strong DC and weak AC,a new characteristics of the development transition period.The traditional control technologies have been difficult to meet the requirements of safe and stable operation of UHV AC/DC receiving power grid,while full use of the DC system support capability,combined with the pumped storage units and interruptible load control resources to improve stability of the receiving grid after the DC blocking fault has been proven by more and more studies as an effective method.Aiming at the stability problem of UHV AC/DC receiving power grid,this paper takes Jiangsu Power Grid as an example to carry out the research on emergency coordinated control strategy using various controllable measures.The main work contents are as follows:Firstly,the power receiving structure of typical UHV AC/DC hybrid power grid in Jiangsu is introduced and the specific connotation of its strong DC and weak AC characteristics is summarized.Then the AC/DC system model of Jiangsu Power Grid is established in PSD-BPA simulation software to analyze frequency and transmission section power responses after different DC blocking fault.Secondly,aiming at the severe frequency stability problem of UHV AC/DC receiving power grid after DC blocking fault,an online frequency emergency coordinated control decision method is proposed based on control performance indexes of emergency DC power support,pumped storage control and precise load shedding measures.The feasibility of different control measures for frequency stability control is analyzed to determine the appropriate DC power lift capacity,DC support duration,as well as pump cutting and precise load control strategy.Considering the frequency control margin,control cost and control response time of three different measures,the quantitative indexes of frequency control performance are proposed,and the heuristic algorithm based on participation factor is used to formulate the frequency emergency coordinated control strategy.The experimental simulation results verify that the decision method can not only effectively improve frequency stability of the receiving gird,coordinate the controllable resources in multiple time scales and geographical space,but also reduce the control cost.Finally,on the basis of the frequency emergency coordinated control decision mothod,considering the overload problem of transmission section,an online multi-stable constraint coordinated control decision method is proposed.Based on the necessity analysis of the overload of transmission section corrective control,according to the grid data after the frequency emergency coordinated control strategy implementation,the concept of section power safety margin is introduced to calculate the section power control performance indexes of emergency DC power support,pumped storage control and precise load shedding measures and formulate the corrective control strategy.In order to further improve comprehensive and refined level of the decision-making,considering frequency stability and section safety,the coordinated control decision method is proposed,which combines controllable measures and sort them according to the control cost,and successively approximates the optimal strategy by means of aggregation coordination and iterative recursion,to achieve fast search and real-time correction of the control strategy.The simulation examples show that the decision method avoids the overload of transmission section problem while maintaining the frequency stability of the receiving grid,and takes into account economy of the control strategy.