Key Technologies Of Analysis And Coordinated Optimal Dispatch Of Integrated Transmission And Distribution Systems

For a long time,many countries and regions have adopted a hierarchical management system for multi-voltage-level power systems.High-voltage transmission systems and low-voltage distribution systems are usually managed by different control centers.However,with the continuous expansion of power grids and the increasing complexity of operation modes,the traditional way of management,dispatch,modeling,and analysis of transmission systems and distribution systems cannot meet the needs of the development of power grid dispatch,control,and operation in the future.To accurately deal with the increasing coupling between transmission systems and distribution systems,improve the security,stability,and economy of power grid operation,and meet the needs of integrated management and dispatching of transmission and distribution systems,academia and industry have carried out fruitful exploration and practice on the analysis and coordinated optimal dispatch.However,with the continuous development of the energy industry,some new challenges have also arisen.Accordingly,these new challenges also bring key technical problems to the analysis and coordinated optimal dispatch of integrated transmission and distribution systems.First,the distributed new energy control mode and the operation mode of distribution systems are more complex.As the looped networks,voltage-controlled distributed generations,and other elements appear in distribution systems,the convergence of the traditional alternating iteration method deteriorates,and even divergence occurs.Therefore,it is necessary to explore how to improve the convergence of the analysis and coordinated optimal dispatch of integrated transmission and distribution systems.Second,the development of new energy and loads has brought more randomness and fluctuation to the operation of power systems.The uncertainties of generations and loads need to be considered in the analysis and coordinated optimal dispatch of integrated transmission and distribution systems.Therefore,it is necessary to explore the modeling of the uncertainties of generations and loads as well as distributed solution algorithms in the integrated transmission and distribution systems.Third,with the function upgrading of control center systems,the communication network loads between transmission control centers and distribution control centers increase,and the local network congestion intensifies.Therefore,it is necessary to explore the asynchronous analysis and coordinated optimal dispatch methods considering the communication network delays to meet the engineering requirements.In view of the above key technical problems,the research of this study is carried out from six aspects:(1)the distributed physical model of integrated transmission and distribution systems considering the randomness of generations and loads,as well as the communication model of integrated transmission and distribution systems considering the randomness of communication delays,are established,which provides a model basis for the analysis and coordinated optimal dispatch of integrated transmission and distribution systems;(2)the successive intersection approximation method,which is based on the fixed point theory,is proposed to improve the efficiency and convergence of the power flow calculation of integrated transmission and distribution systems;(3)an interval power flow analysis method based on the affine operation is proposed,which realizes the quantitative analysis of the uncertainties of generations and loads in the integrated systems and ensures the conservative of the interval solutions;(4)the periodic correction method of iterative variables is proposed to improve the efficiency and convergence of the optimal power flow calculation of integrated transmission and distribution systems;(5)a chance-constrained optimal power flow of integrated transmission and distribution systems based on the double iteration is proposed.Based on the limited information interaction between transmission control centers and distribution control centers,the quantitative analysis of the uncertainties in the optimal dispatch is realized;(6)an asynchronous power flow calculation method of integrated transmission and distribution systems is proposed,based on the forward-backward-splitting method;an optimal power flow calculation method of integrated transmission and distribution systems based on the heterogeneous decomposition method.Under the network communication delays,the algorithm’s calculation efficiency and engineering practicability are improved by reasonably tuning the parameters of asynchronous calculation.Finally,taking the actual situation of China as an example,this paper constructs an overall architecture of the main-distribution integrated dispatch system.An integrated model of transmission and distribution systems is constructed for main-distribution coordinated power flow calculation through the preprocessing of multi-source actual data of the Guangzhou power grid.Power flow calculation is then realized through alternating iterations of prefecture-level control centers and distribution-level control centers.The overall architecture of this main-distribution integrated dispatch system can also support other advanced main-distribution coordinated applications,including main-distribution coordinated optimal power flow,contingency analysis,uncertainty analysis,etc.