You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Survey on Optimal Control and Operation of Integrated Energy Systems 
Chapter Title:  Structure and Characteristic of IES. 
1. Abstract of Cited Paper (BIB001):  Integrated energy distribution system (IEDS) is one of the integrated energy and power system forms, which involves electricity/gas/cold/heat and other various energy forms. The energy coupling relationship is close and complex. IEDS is the focus of regional energy internet research and development at home and abroad. Compared with the traditional power distribution system, IEDS through the multi-energy coupling link comprehensive utilization, effectively improve the distribution system economy, safety, reliability, flexibility and toughness, but also to ease the regional energy system environmental pressure. IEDS is an important direction for the future development of energy systems, and its related research and practice on China's energy system development also has important practical and strategic significance. This paper summarizes the related researches of the IEDS and explores the energy operation characteristics and coupling mechanisms. What's more, the integrated model of IEDS is summarized. On these bases, this paper discusses and prospects some key issues such as joint planning, optimization control and security analysis, state estimation and situational awareness and generalized demand side management. 
2. Abstract of Cited Paper (BIB002):  The trend toward increasing energy efficiency and variable renewable energy (VRE) production has implications for combined heat and power (CHP) plants, which operate in both the price-driven power market and the district heating (DH) sector. Since CHP will be important in VRE integration, we develop a complementarity model to analyze CHP producers’ roles in integrated markets. We use a Nordic case study to gain insights into, first, the effect of the link between CHP and DH on market power and, second, market power's impact on operations in the DH sector. The results indicate that, first, the link of CHP to DH supply can increase market power and, second, market power can induce shifts in DH production from heat only to CHP. 
3. Abstract of Cited Paper (BIB003):  To schedule the distributed energy resources (DERs) and smart buildings of a microgrid in an optimal way and consider the uncertainties associated with forecasting data, a two-stage scheduling framework is proposed in this study. In stage I, a day-ahead dynamic optimal economic scheduling method is proposed to minimise the daily operating cost of the microgrid. In stage II, a model predictive control based intra-hour adjustment method is proposed to reschedule the DERs and smart buildings to cope with the uncertainties. A virtual energy storage system is modelled and scheduled as a flexible unit using the inertia of building in both stages. The underlying electric network and the associated power flow and system operational constraints of the microgrid are considered in the proposed scheduling method. Numerical studies demonstrate that the proposed method can reduce the daily operating cost in stage I and smooth the fluctuations of the electric tie-line power of the microgrid caused by the day-ahead forecasting errors in stage II. Meanwhile, the fluctuations of the electric tie-line power with the MPC based strategy are better smoothed compared with the traditional open-loop and single-period based optimisation methods, which demonstrates the better performance of the proposed scheduling method in a time-varying context. 
4. Abstract of Cited Paper (BIB004):  Increasing interactions between urban electrical and gas systems have the potential to transform smart grids into smart cities, where coordinated dispatch for interdependent urban infrastructure is desirable. This paper proposes an adaptive robust day-ahead energy-reserve co-optimization approach for urban energy systems, in which day-ahead energy-reserve dispatch and real-time energy-balancing regulation are employed as first- and second-stage decisions, respectively. By introducing an auxiliary variable to denote the worst-case balancing cost, we transform the trilevel optimization problem into a single-level model considering generated representative scenarios. Moreover, we propose an iterative algorithm composed of nested problems, where the master problem solves the single-level robust model considering the binding scenario subset identified by the subproblem. In this way, a more computationally tractable model can be obtained, owing to the greatly reduced number of scenarios. Finally, test results on an integrated urban energy network verify the computational superiority of the proposed solution methodology afforded by identifying the binding scenario subset. The economic benefits of the proposed adaptive robust framework are also discussed.

Literature Review:
e inputs of IES are a variety of energy sources and the outputs are electricity, heat and cold energy, to meet the energy demand of di erent users. With the existence of electricity and gas distribution system, heating and water supply pipelines, and other related energy supply network, a coupling system is formed. e coupling between gas and electricity distribution system and the complementation of various energy sources result in the complexity of energy combination and the diversity of energy utilization. According to the size of geographical area and energy characteristics, IES can be divided into three types: park (building) level, city level, and cross-regional level BIB002 . Figure 1 illustrates the typical open interconnection of multienergy systems. IES of building level mainly considers the coordination and complementation of multiple energies of buildings or users, and takes demand response, forecasting of demand load, electric vehicles, and cloud computing as the core technologies. ere is a deep coupling relationship among energy networks BIB004 . IES of park level covers energy systems with various forms and characteristics BIB001 , including underlying equipment, energy system units and systems with multienergy coupling, which has the characteristics of complementary utilization of energy, deep integration of physical information and coordinated interaction of source, network and storage. Regional IES mainly plays a connecting role of energy transmission, distribution, conversion and balance BIB005 . It takes hybrid energy storage system, energy conversion and active distribution network as the core technologies, and there is a strong coupling among energy systems. Cross-regional IES takes power electronics technology, information physics system, transmission, and energy router as its core technologies BIB003 . It mainly considers such factors as management, operation, scheduling (transmission) time between cross-regional energy systems. Based on the energy management and control platform, IES in the park (building) level covers many controllable resources, such as cold, heat, electricity, gas, and water, so as to realize the complementation of multiple energies. Based on the interaction between multiple decision makers, regional IES and cross-regional IES study the operational e ciency and economic cost of distributed and centralized decision makers (joint dispatching center). At the same time, the optimal power ow problem in the process of multienergy ow transmission should be considered to ensure the safe and stable transmission of energy. Electric power system, natural gas system and thermal system are composed of di erent stakeholders. It is necessary to analyze the economic distribution among di erent stakeholders, focusing on game theory and other related theories, so as to enhance the coupling relationship between multienergy ows.