Research On Optimal Planning Of Regional Integrated Energy Systems Considering Energy Quality

With the deepening of multi-energy integration,regional integrated energy system(RIES)has been considered as one of the most important paths to solve the problem of energy shortage in the future world.Due to the complex couplings of various energy forms including electricity,gas,heat and cooling,the planning of RIES is far more difficult than that of the single-form energy system.In this paper,the optimal planning of RIES considering energy quality is studied from four aspects: multi-energy couplings,comprehensive energy utilization efficiency evaluation,optimal energy flow analysis,as well as joint planning of generator-network-load-storage(GNLS).The main achievements are concluded as follows:(1)A multi-energy coupling modeling method of RIES based on hierarchical Energy Hub is proposed.Based on the classical Energy Hub,a hierarchical Energy Hub modeling method is established,wherein the coupling process of RIES from energy input to output is modeled into five clear tiers,i.e.,distribution tier,conversion tier,integration tier,storage tier and network tier,comprehensively covering the complex multi-energy couplings among GNLS.Thus a bridge between input and output is built to ensure the balance of energy supply and demand.This model not only can be integrated into optimal planning models,but also can realize automatic modeling,which has been applied in commercial software designs implementing friendly man-machine operating functions.(2)The evaluation method of comprehensive energy utilization efficiency of RIES based on exergy analysis is proposed.Based on the double attributes,i.e.,“quantity” and“quality” of energy,the concept of exergy born in thermodynamics is introduced into RIES.The concept of “energy quality coefficient” is defined to quantify the quality of various energy forms involved in RIES.The expressions of energy quality coefficient corresponding to each energy form are derived in detail,and the physical essence are deeply explored.Thus a novel method of exergy efficiency calculation for RIES based on black box model is proposed,which covers all the energy forms involved in RIES without considering the massive and complex energy conversion processes.The calculation can be completed only by relying on the external information of energy input and output of the RIES,thus achieving a reasonable evaluation of the comprehensive energy utilization efficiency.(3)An energy flow analysis and optimization method for RIES based on mixed integer cone programming is proposed.According to the physical nature of each subsystem including electricity,gas,heat,and cooling,the mathematical models of steady state energy flow calculation are derived.Then RIES optimal energy flow model was established with the objective of minizing the operation cost.The convexity and approximation methods are proposed to solve the non-convex and non-linear problems of the original model,via which the model can be transformed from a mixed integer nonlinear programming to a mixed integer cone programming.Thus the model can be solved by convex optimization theory,which improves the solving efficiency and can support large-scale RIES with multiple nodes and strong couplings.Case study shows that the proposed model can be solved efficiently with excellent universality and scalability.(4)A joint planning method of GNLS for RIES considering energy quality is proposed.A complete RIES planning model is constructed,which can realize the planning of RIES from scratch with the only known information of load demands.The planning objects cover GNLS,and potential of multi-energy couplings can be fully explored through this model,with economy and energy comprehensive utilization efficiency both considered in objective functions.Several convex relaxation measures are proposed to improve the solving efficiency,and the ?-constraint method and SQP(Sequential Quadratic Programming)algorithm are combined to achieve the Pareto Frontier.The planning model covers equipment capacity configuration,network topology design and operation scheduling optimization,which can provide a complete solution for RIES planning.