Research On Cooperative Optimization Operation Technology Of AC/DC Distribution Network For High Proportion Of Distributed Generation Integration

To cope with the increasingly severe energy depletion crisis and environmental pollution problems,vigorously developing distributed power sources represented by wind power and photovoltaics has become an important part of my country’s energy development strategy.The large-scale access of distributed power generation has significantly changed the system structure and operation mode of the traditional distribution network,which has brought serious challenges to the safe and stable operation of the distribution network.Combining both AC and DC distribution networks,AC/DC distribution network has outstanding advantages such as flexible topological structure,controllable power flow,and strong scalability,which makes it possible to provide effective support for the connection and consumption of large-scale distributed power generation.However,the current operation and control methods for AC/DC distribution networks are not yet perfect,while the utilization rate of regulation resources also needs further improvement.In the context of high-proportion access of distributed power generations and micro-energy internet,there are still many problems that need to be studied urgently.Therefore,in view of the development trend of AC/DC distribution network,research on the optimization operation technology of AC/DC distribution network with flexible power supply capability has important practical and forward-looking significance for improving clean energy consumption and building a power system with a high proportion of distributed power generation.In order to deal with the above situation,this paper conducts an in-depth study on the collaborative optimization operation technology of AC/DC distribution network for high proportion of distributed power access.The main contents are as follows:For the optimal power flow problem of AC/DC distribution network with flexible power supply structure,a improved unified power flow calculation method for joint optimal dispatching of AC/DC distribution network is proposed.Firstly,based on the connection mode and steady-state dispatching model of key components of the AC/DC distribution network including Voltage Source Converter(VSC),optimal power flow models with the optimal objectives of operating cost and network loss are proposed,respectively.Secondly,based on the unified expression form of the power flow equation of the AC/DC distribution network,the mathematical characteristics of the optimal power flow model are analyzed,and the unified power flow algorithm of the AC/DC distribution network is studied.The convex relaxation of the non-convex constraint is realized based on second-order cone relaxation,which greatly reduces the complexity of the power flow model.Finally,the improved IEEE-33 node AC/DC distribution network system is used for simulation calculation,and the calculation results verify the accuracy of the proposed unified power flow algorithm.For the collaborative optimization of various regulation resources within AC/DC distribution network under the background of high-proportion distributed power generation access,the AC/DC distribution network optimization dispatching technology considering dynamic network reconfiguration is proposed.First,the mathematical model of the radial network structure constraints of the distribution network is established,and the model modification method is proposed to avoid the passive loop network during the reconfiguring process.On this basis,a two-stage coordinated dispatch model of AC/DC distribution networks considering dynamic network reconfiguration is built.This model aims to optimize the comprehensive operating cost of the AC/DC distribution network considering various available resources in the distribution network.In the first stage,the network topology and transformer sub-tap gear in each period are determined according to the short-term forecast data of the distributed power generation and load.In the second stage,various scheduling resources are further optimized and dispatched according to the ultra-short-term forecast data.Finally,the linearization method of the coordinated scheduling model is proposed to realize the effective solution of the scheduling strategy.Numerical simulation verifies the effectiveness of the proposed coordination scheduling model,which can significantly promote the consumption of distributed power generationFor the problem of dual-side optimization of both energy supply and demand of the microenergy internet connected to the AC/DC distribution network,the self-dispatching technology of the micro-energy internet considering the coupling response characteristics of cooling,heating and electricity demand is studied.Firstly,a micro-energy internet operation architecture considering the coupling characteristics of both energy supply and demand side is constructed.Secondly,based on the electricity load price elastic response model,an Integrated Demand Response(IDR)model considering the coupling response characteristics of cooling,heating and power demand and a micro energy internet self-dispatching model are established.The selfdispatching model aims at minimizing the operating cost of the micro-energy internet and realizing the coordinated dispatch of energy supply-side and demand-side by optimizing the multi-energy price on the demand side and the operating parameters of energy conversion equipment on the supply-side.Finally,based on a typical multi-energy system,the IDR model and the micro-energy grid self-dispatching model are simulated and verified.The simulation results show that the proposed IDR model considering the demand coupling response characteristics can accurately describe the coupling response mechanism of multiple energy sources to energy prices.Meanwhile,the self-scheduling model of the micro-energy grid can accurately reflect the external characteristics of the micro-energy grid.For the optimal operation of the AC/DC distribution network with micro-energy internet access,the optimal dispatching strategy of the AC/DC distribution network considering both dynamic network reconfiguration and multi-energy coordination is proposed.First,the coordinated operation mechanism using locational marginal price of the distribution network and purchase/sale power of micro-energy internet as interative variables is established according to the characteristics of the system structure and dispatching model of AC/DC distribution network system with micro-energy internet attached.Secondly,on the basis of dispatching model proposed in the foregoing two chapters,a two-layer coordinated dispatch model of AC/DC distribution network based on the extreme learning machine is established with the optimal objective of system operation cost.The upper-level model solves the locational marginal price corresponding to the optimal operation cost and passes it to each micro-energy internet with all micro-energy internets considered as virtual loads.The lower-level model optimizes the internal energy production plan and external power purchase/sale plan of microenergy internet based on the electricity price provided by the distribution network.The twolayer scheduling model is then solved through cross-iteration under the framework of heterogeneous decomposition.Finally,the simulation studies based on the improved IEEE-33-node AC/DC distribution network with micro-energy internet shows that the proposed collaborative optimization model can significantly enhance the flexibility of system operation through dynamic network reconfiguration.It can effectively promote the consumption of distributed power generation through the coordination and complementation of the AC/DC distribution network and the micro-energy internet.Meanwhile,the solution algorithm based on heterogeneous decomposition can realize the efficient solution of the dispatch model.