Multi-Energy Flow Calculation And Static Voltage Stability Analysis For Integrated Energy System

Integrated energy system is an effective form to realize energy ladder utilization,improve energy comprehensive utilization efficiency and promote the integration of renewable energy.But the coupling and interaction between multi-energy carriers make the research complicated,especially when high proportion renewable energy is injected,the operation mode and control strategy of the system are flexible and diverse,and the energy flow distribution is different from the tradition.In addition,natural gas system,thermal system as the source or load of power system,will certainly affect the original power flow distribution and safety degree.Therefore,this paper studies the energy flow calculation of integrated energy system,and further studies the stability evaluation.The results of the research have certain guiding significance for mastering the state of integrated energy system,planning and design,optimizing operation and protecting control.The specific contents of this article are as follows:(1)According to the physical structure and operation mechanism of the integrated energy network,this paper fully studies the interconnection between the networks,establishes the mathematical model of power,natural gas,thermal network and coupling equipment,and lays the foundation for energy flow calculation and steady-state analysis.(2)To solve the problem of the variation of gas quality,pressure and other parameters caused by the existence and mixing of multiple gas sources,a calculation method for energy flow of integrated energy system with multiple types of gas sources is proposed.By establishing a unified energy flow solution model including the specific gravity and gross calorific value deviation equation,and modifying of the unified Jacobian matrix,the influence of multi-type air supply on the integrated energy system is quantified,and the correctness and effectiveness of the proposed algorithm are verified by example analysis.(3)To solve the problem of the limited capacity and heavy burden of the single slack bus model in the coupled state,an energy flow calculation method for the integrated energy system with distributed slack bus is proposed.Based on the power sensitivity analysis,a distributed slack bus model considering the advantages of coupling equipment and the corresponding energy flow calculation method are established.The advantages of the distributed slack bus model in reducing the centralized burden and improving the integrated energy system to cope with power fluctuations are verified by example analysis.(4)To solve the change of energy flow distribution and stability in coupled power systems,a static voltage stability analysis method for integrated energy systems based on energy flow equation is proposed.The static stability criterion of power system in coupled state is given,and the stability problem is transformed into the problem of whether the energy flow has a solution.Secondly,the static voltage stability judgment matrix is established.Finally,the current voltage stability degree of the system is answered based on the singular value decomposition theory.An example is given to verify the applicability of the proposed index to determine static voltage stability in a comprehensive energy system.The proposed method and index can be used to select a safe and stable operation mode.