Research On Key Technologies Of Multi-energy Flow Optimization And Management In Integrated Energy System

The increasingly prominent issues of energy and environment have brought great influence to the traditional energy production and consumption mode.Under the background of energy structure transition and Energy Internet,the integrated energy system(IES),which is a physical carrier that uses electricity as the core to coordinate and optimize multiple energy forms,will become a main direction for the energy system development in the future.It also plays an important role in improving the energy comprehensive utilization efficiency,promoting the consumption of renewable energy and achieving multi-energy complementarity.How to maximize the comprehensive benefits and ensure the safe and reliable energy supply of IES based on the mutli-energy flow optimization and management to is becoming a key technical problem that needs to be solved.Based on the requirements of multi-energy flow optimization and management of IES,the research covers four key technical problems of multi-energy flow modeling,multi-time scale optimal dispatch,static security analysis and security an economic optimal operation.The main research work and achievements are listed as follows:(1)Modeling of the multi-energy flow of IES is the basis and premise of energy optimization and management.Based on the analysis of the basic topology of IES and the multi-energy flow interaction mechanism,the physical models of conventional energy equipment are established firstly.What’s more,the energy hub model with different structures is used to describe the coupling and conversion relationship of different energy forms.Based on the energy equipment modeling,the steady-state model of electricity,heat and natural gas transmission networks is established and the different operation modes of IES are analyzed.Finally,to solve the problems of high complexity and low efficiency during the energy flow calculation process,a distributed sequential solution algorithm for the hybrid energy flow calculation is proposed,and the effectiveness of the algorithm is verified by a testing case.(2)The access of large-scale renewable energy and all kinds of energy demand forms increased the uncertainty on both source and demand sides of IES,which will bring greater challenges to its optimal operation.Focus on the problems above,a day-ahead and intra-day multi-time scale optimal dispatch model is proposed in this paper for the distributed IES.During the day-ahead dispatch process,scenario simulation and analysis method is used to deal with the uncertainty of wind power,photovoltaic and loads.It mainly contains two steps:scenario simulation based on Latin hypercube sampling and scenario reduction based on K-means clustering algorithm.Based on the typical operation scenarios,an economic stochastic optimization model is established,which takes both operation economics and the energy efficiency of IES into account.To track the day-ahead dispatch results,an intra-day rolling optimization model is proposed combining model predictive control strategy and genetic algorithm,so as to realize the real-time corrective control of each controllable unit in IES.The case study results demonstrate the efficiency of the proposed model.(3)Security is the important link that needs to be considered in the operation and energy management of IES.The deeper coupling between different energy systems makes the interaction mechanism of them more complex,which makes great influence on the security and reliability of IES.Firstly,An N-1 static security analysis and evaluation model is proposed to analyze the variation characteristics of the state variables based on the IES contingency set,so as to preliminarily identify the current operation status of IES.As the coupling and integration of multi-energy flow in IES deepens increasingly,the cascading failure will develop across different energy systems more easily and widely.So,a novel simulation model of the cascading failure in IES was proposed in this paper to improve the rationality and comprehensiveness of IES security analysis.Based on the predicted fault chain,vulnerability analysis is presented to locate critical component and find out the correlation between cascading outages.Finally,the case studies are carried out on the combined heating and power systems to demonstrate the effectiveness of the proposed method.(4)Considering the complex network topology and large area for energy transmission,the economic and security of district IES should be both taken into account during the optimal operation process.So,a bi-level optimization model considering static security and optimal energy flow is proposed for district IES with multiple energy hubs.Firstly,the vulnerable components of IES are located by constructing a IES cascading fault space-time graph and calculating the node degree index.A prevention-correction hybrid control strategy is proposed to further screen the vulnerable components.On this basis,the day-ahead optimal optimization model is established.Overall IES operating cost and static security are both taken into account in the upper-level of the model to optimize power-heating output of each energy hub.After obtaining multi-objective optimal energy flow distribution of IES,the lower-level of the model takes both economic index and photovoltaic accommodation capacity as the target to optimize the output of each unit in energy hubs.Finally,a case study is given to verify effectiveness of the proposed model.