## 2 Literature Review  
Demand-side controllable loads (e.g., air conditioners, water heaters, and refrigerators, etc.) have the characteristics of large power consumption, rapid response, and flexibility. According to [PERSON] [12], a high-precision AC load aggregation model is established based on the second-order equivalent thermal parameter (ETP) model of the AC load, meanwhile, the AC cluster control strategy is designed to provide various demand response services such as frequency adjustment and peak shaving. According to [PERSON] [13], the AC load is equivalent to a VES device base on the second-order equivalent thermal parameter model of the AC load, which improves the matching characteristics of the system, reduces the discharge depth and increases the life of the battery. However, model parameters based on the ETP are not easy to obtain, which increases the complexity of research. The relationship between the amount of cooling supplied by the AC, the heat storage capacity of the building, and the dissipation of cooling is established according to the law of conservation of energy, the continuous change characteristic curve of the temperature in the AC room is obtained in the work of [PERSON] [14]. The AC load modeling principle based on energy conservation is simple and does not require parameter identification. This paper uses this method to model the AC load and further establishes its VES model. According to [PERSON] [15], a type of first-order explicit equation is utilized to describe the thermal dynamic modes of the EWH, and the optimal scheduling problem of EWH is solved using linear integer planning to reduce the system dispatch costs. In the work of [PERSON] [16], a comprehensive model of the EWH is built, which switches between a one-node model and a two-node model depending on the situation and test its responses. According to [PERSON] [17], a VES model of a domestic refrigerator is developed based on its thermodynamic model, its control algorithm using the grid frequency as a regulation signal is proposed to mitigate the impact of uncertainties of DR. The aforementioned literature models typical controllable loads on the demand side and validates their utility for independent participation in DR. However, in actual situations, the demand side generally coexists with multiple controllable loads, and they can participate together to provide DR services.  
In a residential microgrid, the floor radiant heating/cooling system is modeled as a VES system, and the operating cost of the residential microgrid is effectively reduced through optimal scheduling of the microgrid [18]. In a combined cooling, heating, and power microgrid, the VES of the building is considered in the optimal scheduling model, which improves the economic and environmental operational benefits [19]. In a hybrid energy microgrid, a VES system based on AC and buildings is established, and the daily operating cost of the microgrid is reduced through the charging/discharging management of the VES system [20]. With the increasing penetration of BIPV in urban commercial buildings, it is practical significance to improve the operating economics of BIPV microgrid. However, little literature has considered VES in BIPVmicrogrid to enhance its economics.  
Therefore, in this paper, both the ACVES and EWHVES models were built and integrated into BIPV microgrid's optimal scheduling model. Through proper control of these devices, they can operate as VES that with similar functions of a battery storage system, i.e., transferring energy among each time interval based on the price signals. Thus, the operation cost of a BIPV microgrid can be further reduced with the proposed control strategy.