# Flexible Dispatch for Integrated Power and Gas Systems Considering Power-to-Gas and Demand Response
## 1 Introduction  
With the increasingly prominent energy and environmental problems, renewable energy power generation has attracted wide attention from all over the world [1]. As a kind of typical renewable energy resources, wind power has been developed rapidly in recent years. However, the uncertainty and volatility of wind power challenge the flexibility of power systems, resulting in a large amount of wind power curtailment [2]. In 2017, the total wind power curtailment rate was over 20% in the north of China [3]. Therefore, it is urgent to improve the power system flexibility to benefit the accommodation of wind power while ensuring the secure operation of power systems. Nowadays, many measures can be taken to improve the flexibility of power systems with high penetration of wind power. From the generation side, more gas-fired generators are built due to their high generation efficiency, fast ramp rate, and low CO2 emission intensity [4]. From the load side, the demand-side response can contribute to changing the hourly load profile to add the power system flexibility [5]. From the energy conversion, power-to-gas (P2G) facility is an effective way that has recently been widely studied to provide the flexibility of power systems with large-scale wind power in China [6]. Since the large-capacity power storages still face challenges, excessive wind power has to be curtailed. Thanks to the P2G technology, the excessive wind power can be converted into hydrogen (H2) by water electrolysis and further converted into methane (CH4) via Sabatier reaction. Afterwards, methane can be stored via the natural gas systems or storage devices [7]. On the one hand, power systems and natural gas systems are closely coupled with the increasing proportion of natural gas in power generation [8; 9]. On the other hand, the maturity of P2G technology further strengthens the interaction between the power system and natural gas system, which makes bidirectional energy conversion possible [10]. How to use the coupling characteristics of power system and natural gas system to coordinate and optimize the energy transmission and distribution problems of gas-power integrated energy system, and then enhance the flexibility of power system, has become a hot research topic for scholars at home and abroad in recent years. In [11], a new electric-gas combined system (EGCS) operation strategy considering the dispatch evaluation index is introduced to improve the dispatch of EGCS, and then, proposes a unified quantitative dispatch modeling method. In [12; 13; 14; 15; 16], a centralized optimization approach is used to study the coordinated optimization of the electricity-gas interconnection system, assuming that both systems are subject to a unified dispatch scheme by a common decision maker, as opposed to the current situation where the electricity and natural gas systems are operated and managed by separate operators. To ensure that the optimization approach is as consistent as possible with the actual situation, some scholars have started to apply the idea of distributed coordinated optimization to model the optimal scheduling of two systems separately, and then realize coordinated optimization through key information interaction. A distributed multi-scene optimization framework based on an alternating directional multiplier method (ADMM) is proposed in [17], which decouples the original optimization sizing problem into an investment subproblem and multiple operational subproblems considering multiple scenarios. In [18], it is demonstrated that bi-objective optimization of a high-pressure gas network ensures better system efficiency than scalar optimization. The proposed algorithm seeks a compromise between minimizing the compressor operating costs and maximizing the gas network capacity (security of supply to customers). In [19], a cooperative game model for an integrated energy system-hydrogen and natural gas hybrid energy storage system (IES-HGESS) considering carbon neutrality was constructed.