Study On Power Flow Calculation And Optimal Dispatch Model Under The Concept Of Electro-Thermal Coordination

Under the background of growing electricity demand,both academia and engineering members have focused on exploiting the transmission conductor's potential capacity sufficiently to impove the utilization efficiency of exiting power,ease the contradiction between power supply and reduce or postpone the buliding of new transmission corridor,which has special significance for practicing energy conservation and optimizing power grid configuration.As an emerging scheduling control theory,electro-thermal coordination theory has received wide attention for its highlighting of thermal load capacity of tansmission line.This paper promoted the development and improvement of electro-thermal coordination theory in power grid operation through theoretical and experimental research,especially in the conductor temperature calculation model and the solution of electro-thernal coordination model.The main research work can be summarized as follows three points.1)Research of electro-thermal coordination power flow model considering the nonlinear characteristics of AC resisance.In this research,an experimental platform is set up and resistance values of the conductor are measured under different currents and temperatures,then a current correction AC resistance model is built combined with parameter estimation method.On this basis,an electro-thermal coordination power flow model considering the nonlinear characteristics of AC resisance is proposed and the Newton solution method is derived,furthermore an electro-thermal decoupling method is proposed to reduce model complexity according to the characteristic of reactance much greater than resistance in high-voltage transmission network.Case study results show that the model is helpful to avoid overrating the allowance of line operating temperature,thus ensure the operation security of system;the proposed decoupling method can improve the solving effency of the model.2)Research of electro-thermal coordination dynamic optimal power flow model considering radial temperature distribution of the conductor.In this research,a radial thermal circuit model expression with state equation is built based on thermoelectric analogy theory and model parameters are proposed to obtain through parameter identification method to overcome the difficult of calculating thermal power,thermal resistance and thermal capacity,the regularity of model parameters with current and meteorological conditions are revealed.On this basis,double temperature constraints including surface temperature constraint and core temperature constraint are condtructed to ensure the security of transmission line,thus the electro-thermal coordination dynamic optimized power flow model considering radial temperature distribution of the conductor is built.A simplified calculation method in which static variables and dynamic variables are decoupled is proposed in the solving process with primal-dual interior point method,according to the special structure of KKT modified equation coefficient matrix.Case study results show that the model can ensure the safety of wire sag,thus improve the reliability of schedulingdecision.3)Research of electro-thermal security economic dispatching model based on model predictive control.In this research,a new short-term wind speed forecasting model based on wavelet packet decomposition and peak-type Markov chain is proposed to explore the uncertainty of meteorological parameters.Wind speed prediction error and its correlation with forecasting time are revealed combined with traditional wind speed forecasting model,then the insufficient of traditional open-loop scheduling model in coping with prediction error is analysed.On this basis,an electro-thermal coordination security economic dispatch model based on model predictive control is proposed,in which open-loop optimization is substituted by rolling time domain optimization and the real measuring output are taken as the feedback information to close the control loop.Case study results show that the proposed model can correct the deviation of optimal scheduling results caused by meteorolodical prediction error timely,thus improving the accuracy of control decision,which is beneficial to promote the further engineering applications of electro-thermal coordination scheduling theory.