Research On Distribution Network Configuration Under The Circumstance Of High Proportion Of Renewable Energy And Power Electronization

Driven by the technology development of distribution renewable energy exploiting and power electronics in recent years,traditional distribution network has shown some configuration transformation of its sources,network and loads.On the one hand,large amount of distribution generators(DGs)have turned the traditional passive distribution network into an active one,which makes the power dispatch more complicated.Meanwhile,the intermittent and fluctuant power supply from high proportion of renewable energy not only puts forward higher requirement for the flexible adjustment ability inside the distribution network,but also poses challenges to the peak load and frequency regulation at the boundary between the transmission and the distribution network.On the other hand,with more and more renewable energy and DC loads getting involved,the advantages of DC distribution network become increasingly prominent.DC network configuration can avoid large amount of converter investment while makes the grid operate more safely,economically and efficiently.Thus,it is of great significance for future optimal operation to explore the development pattern of the distribution network configuration from the aspects of sources,network and loads under the circumstance of high proportion of renewable energy and power electronization.This thesis mainly focuses on the adaptive transformation of the distribution network configuration in the aspects of sources,network and loads under the circumstance of high proportion of renewable energy and power electronization.The coordinated optimal dispatching of flexible adjusting resources and the evolution law and optimal operation of AC-DC distribution network under the circumstance of high proportion of renewable energy and power electronization have been studied.Detail works are as follows:(1)A coordinated optimal dispatching model considering various kinds of flexible resources in the distribution network under the circumstance of high proportion of renewable energy and power electronization is proposed.Firstly,the characteristics of various flexible resources are analyzed and mathematical models are established.Secondly,based on the branch power flow method,the optimal power flow calculation model of the AC distribution network is established by using the second-order cone optimization theory.Thirdly,the optimal dispatching of flexible adjusting resources is taken into account comprehensively in the optimal power flow calculation model.An optimal dispatching model of distribution network considering multiple flexible adjusting resources is established.Finally,the dispatching model is used to show the benefit getting from flexible adjusting resources and determine the optimal allocation of the energy storage in terms of capacity and output power limit.(2)In aspect of network planning,the configuration of AC-DC distribution network under the circumstance of high proportion of renewable energy and power electronization is analyzed and evaluated,and the optimal configuration evolution path of the AC-DC distribution network is proposed to transfer the AC distribution network to the DC distribution network.Firstly,an optimal power flow model of AC-DC distribution network considering converter units and DC power flow is established.Then,considering the investment cost of the AC-DC distribution network,a two-layer optimization model for the optimal topology evolution is established.Finally,an example is given to reveal the optimal path of topology evolution.(3)In aspect of network operation,the operation patterns of AC-DC distribution network under the circumstance of high proportion of renewable energy and power electronization is analyzed and modeled.By simplifying the converter units,a optimal dispatching model in the form of second-order cone is established for AC-DC distribution network,and the optimal operation point is solved by using the second-order cone optimization theory.On this basis,the internal relationship among the decision variables,the state variables and the state equations is analyzed.The optimization mechanism of the AC-DC distribution network,which improves the flexibility for power flow control,is clarified.Finally,an example is used to analyze the advantages of AC-DC hybrid distribution network in terms of renewable energy consumption and improving the operation conditions.