Research On Model And Algorithm For Risk-based Dispatch In Power Grids Considering The Operating Status Of Lines

Transmission lines are basic devices constructing power grids.Their reliability and load capacity have a significant influence on dispatch decisions of power systems.In this dissertation,deep reseaches on risk-based dispatch methods and algorithms are carried out from multiple time scales from the medium and short term,day ahead and real time.Furthermore,related engineering applications are explored and performed.Main contributions are summarized as follows:(1)An enhanced security-constrained OPF model which considers the thermal inertia of lines is proposed.The technology of dynamic thermal rating is used to improve short-term line capacities in the post-contingency stage to guarantee the operation security of power systems.Two typical temperature changing processes of overload lines are analyzed and then an equvilent time method is presented to build a relationship between the highest conductor temperature and unit power outputs.The security region of systems is expanded while a better operating point can be obtained.This model has both advantages of the security and economy from the preventive OPF model and the corrective OPF model,respectively.(2)A coordination model of the unit commitment and maintenance scheduling for units and lines is proposed.In this model,the power overflow caused by line forced outages are quantified.In order to solve the optimal decision-making problem of power systems involved in multiple periods and scenarios,a three-layer solving framework based on the Lagrangian relaxation and the Benders decomposition is further presented.The original problem is divided into several sub-problems of the unit and line maintenance scheduling,unit commitment and risk-based dispatch which are separately solved and iteratively coordinated.The total operating cost declines by above coordinations and the operation risk is effectively controlled.(3)A short-term reliability model of transmission lines considering the natural aging,health condition,disaster weather and load current is established.Furthermore,this reliability model is integrated into the proposed multi-stage risk-based dispatch ABSTRACT method.Scenario probabilities are calculated by time-varying failure rates of lines.The expected optimal load shedding is regarded as the risk severity and included in the objective function.In the presented double iterative solving strategy,the successive linearization method is utilized to handle bilinear items constructing the risk cost.While internal and external factors affecting the reliability of lines are taken into account,the operation risk of power systems can be traced and more reasonable dispatch decisions could be made.(4)A framework of the whole process risk coordination control consisting of the medium and short-term,day-ahead,real-time and post-contingency stages is established while the software architecture and related key technologies are discussed.The developed risk management and control system base on this framework is applied to a provincial power grid.Results of the above engineering application show that the proposed risk coordination control strategy can adapt to the current dispatching paradigm.The system can provide dispatchers with timely and effective decision supports and realize the step-by-step tracking and rolling control for the operation risk of power systems.