## 1 Introduction
Essentially, all energy (electricity, gas, heat) storage can be called energy storage systems, and the configuration of multiple energy storage equipment in the RIES can greatly improve the economy of the system and the phenomenon of wind abandonment [20]. Due to the relatively low cost of gas storage, it is possible to develop gas storage technology in the RIES [21]. Electric-thermal energy storage systems were used in [22] to increase the wind power consumption rate of the system. In [23], the impact of electric-thermal storage systems on the operation of Northern Communities' microgrids was analyzed. P2G and gas energy storage were adopted in a multi-source microgrid to study their impact on the economy of the system and the ability to absorb wind power in [24]. The operational impact of P2G on electrical and gas transmission networks was studied in [25]. Further, the study in [26] optimized the configuration of energy storage equipment in the RIES by a bi-level planning approach, but the gas storage system was not involved in it. None of the research above proposed the configuration model of electro-gas-thermal energy systems. Mutual influence between electric-thermal-gas energy storages was studied in [27], and the conclusion that multi-energy storage systems have the optimal economics was obtained. However, the capacity of the energy storage equipment has a certain impact on the above conclusion, of which there is lack of in further discussions. In general, there are many studies on the RIES planning with electric and thermal loads as terminal loads. However, the load demand in the RIES is diversified, and the gas load is gradually becoming an indispensable energy demand, but the research on the RIES planning with electric-thermal-gas loads as terminal loads is insufficient. In addition, a variety of energy storage equipment can improve the efficiency and economy of the RIES, but the research objects of related research are mostly concentrated in the source, network, and load. Therefore, the research on the electric-gas-heat integrated energy storage configuration method is insufficient. Moreover, the RIES operation mode is also divided into grid-connected and off-grid. At present, the planning for the RIES is mostly studied from grid-connected or off-grid mode, and the research on planning of RIES operating on both grid-connected and off-grid modes is less involved. In this paper, the RIES was first modeled from the four parts of the supply side, energy conversion side, energy storage side and the load side. Then, a method for configuring the rated capacity and power of electric-thermal-gas energy storage devices in the RIES with electric, thermal, gas loads as terminal loads was proposed. The contributions of this paper are summarized as follows:  
(1) In order to more clearly describe the functions of each link in RIES, this paper carried out extended modeling of the RIES, which can reduce repetitive modeling time and increase efficiency when the RIES structure is changed. (2) The configuration optimization model of electric-thermal-gas energy storage systems for the RIES under both off-grid and grid-connected operating modes was proposed. In other words, the method to determine the optimal configuration scheme of electric-gas-thermal energy storage equipment of the RIES was carried out. (3) The electric energy substitution and operation strategy were considered in the configuration optimization model. (4) The sensitivity analysis was carried out to quantify the influence degree of each factor (such as price, etc.) on the result of the energy storage configuration. The remaining sections of this paper are as follows: Section 2 describes the RIES mathematical model. The configuration optimization model of energy storage systems is introduced in Section 3. A case study and results analysis are given in Section 4. The discussion is given in Section 5. Finally, Section 6 draws the conclusion.